A process and device for preparing pure Li2CO3 by continuous flow carbonization reaction in the process of carbonization purification of industrial Li2CO3

Abstract

The present invention discloses a process and apparatus for preparing pure Li2CO3 by continuous flow carbonization reaction during the carbonization process for purifying industrial Li2CO3. The process comprises: a slurry prepared by mixing industrial Li2CO3 with deionized water contacts and reacts with a mixed gas of CO2 and air blown in within a microbubble vertical reactor; the reaction liquid is received after a residence time, and a LiHCO3 solution is obtained after precision filtration; after purification and thermal cracking, a battery-grade Li2CO3 product is obtained. The reaction apparatus comprises the following modules: a slurry control and delivery module, a gas control and delivery module, a gas distribution module, and a reactor main body module. The process of the present invention shortens the reaction time of the carbonization reaction, avoids slurry sedimentation, and improves the utilization rate and production efficiency of CO2; the apparatus used in the process strengthens the reaction process of the carbonization reaction, and has a high safety factor and strong controllability. This invention is conducive to large-scale industrial application.

Description

Technical Field

[0001] The present invention relates to a process and device for preparing pure Li2CO3 by continuous flow carbonization reaction in the process of purifying industrial Li2CO3 by carbonization method. Background Art

[0002] Li2CO3 is a fundamental lithium compound with diverse industrial applications. It can be converted into a variety of other lithium compounds and is widely used in lithium battery cathode materials, medicine, aerospace, metallurgy, welding, ceramics, lithium alloys, and other fields. With the development of new energy vehicles, the demand and price of battery-grade Li2CO3 will continue to rise.

[0003] Currently, industrial Li2CO3 is produced through two methods: extracting lithium from ore and extracting lithium from salt lake brine. The resulting Li2CO3 has a purity lower than the standard for high-purity battery-grade Li2CO3 (99.5%-99.9%). Further purification of industrial-grade Li2CO3 can produce battery-grade Li2CO3. Commonly used techniques include recrystallization, carbonization decomposition, carbonization precipitation, and causticization.

[0004] Among the existing methods for purifying lithium carbonate, the carbonization decomposition method is widely used in industrial production due to its short process flow, mother liquor recycling, high recovery rate, and simple operation. The specific reaction equation is as follows:

[0005] Carbonization reaction: Li2CO3(s)+CO2(g)+H2O(l)→2LiHCO3(aq);

[0006] Thermal decomposition reaction: 2LiHCO3(aq)→Li2CO3(↓)+CO2(g)+H2O(l).

[0007] Master's thesis research by Quanfeng Zhao of Kunming University of Science and Technology, Hao Wen of Jiangxi University of Science and Technology, and Hanzhang Gong of Wuhan University of Technology all used atmospheric pressure carbonization decomposition to purify Li2CO3. The atmospheric pressure carbonization reaction times were 30 minutes, 45 minutes, and 60 minutes, respectively, and the CO2 consumption was significant, at 30 eq, 88 eq, and 146 eq, respectively. Patents CN110357129A and CN115072750A also used the same carbonization method, but their drawbacks were low reaction efficiency and excessive energy consumption.

[0008] J MATER RES TECHNOL. 2020; 9(5): 9498-9505 reported the use of CO2 pressurized microbubbles to assist carbonization reaction in a reactor. Although this process uses a pressurized method for carbonization reaction, it still fails to change the shortcomings of long reaction time (2.0h) and high carbon dioxide consumption; Patent CN209338136U proposes a continuous Li2CO3 purification reactor group. Under a low pressure of 0.1-0.2MPa, the carbonization reaction is carried out through five consecutive reactors (with gas distribution pipes inside). Due to the shortcomings of poor mass transfer and heat transfer performance of the reactor group, the reaction effect is not ideal. Based on the above research, in the gas-liquid-solid three-phase carbonization reaction, the traditional reactor reactor has the disadvantages of small specific surface area, low heat exchange efficiency, and limited gas-liquid mass transfer efficiency, which leads to the inability to effectively utilize a large amount of CO2 and excessive energy consumption, which is not conducive to industrial application.

[0009] When using the carbonization decomposition method to purify Li2CO3, optimizing the carbonization reaction is a key step. The solubility of Li2CO3 and CO2 in water decreases with decreasing temperature, but the carbonization reaction is an exothermic reaction (adiabatic temperature rise is between 10-13°C), which is limited by the shortcomings of traditional kettle reactors, resulting in insufficient mass transfer and heat transfer performance of the reaction process. The device proposed in the present invention, the microbubble vertical reactor, utilizes the excellent mass transfer and heat transfer performance of the tubular reactor, increases the contact area by blowing CO2 microbubbles, and increases the solubility of CO2 by pressurizing, essentially shortening the reaction time, reducing the amount of CO2, and realizing the continuous production of LiHCO3 solution safely and efficiently. Compared with kettle production technology, the continuous flow tubular process of the carbonization reaction has low energy consumption, fast speed and high efficiency. Summary of the Invention

[0010] To address the shortcomings of existing Li2CO3 carbonization purification processes, the present invention aims to provide a process and apparatus for producing pure Li2CO3 through a continuous-flow carbonization reaction during the carbonization process for industrial Li2CO3 purification, suitable for large-scale development and application. The present invention utilizes a continuous-flow vertical reactor to intensify the carbonization reaction during the Li2CO3 carbonization purification process, providing a greener and more efficient production pathway that overcomes the shortcomings of existing carbonization reaction processes.

[0011] The technical solution adopted in the present invention is as follows:

[0012] The process for preparing pure Li2CO3 by continuous flow carbonization reaction during the carbonization process for purifying industrial Li2CO3 comprises the following steps:

[0013] 1) Industrial-grade Li2CO3 and deionized water are mixed and stirred in a batching tank to prepare slurry a, the flow rate of slurry a is controlled by a metering pump, and the slurry a is continuously fed into the bottom of a microbubble vertical reactor; the flow rates of CO2 and air are respectively controlled by a gas flow meter, and the CO2 and air are mixed in a gas mixer and then blown into the bottom of the microbubble vertical reactor. By adjusting the internal pressure of the reactor, the CO2 microbubbles and slurry a are fully contacted in the reactor to cause a carbonization reaction;

[0014] 2) The reaction liquid is discharged from the top of the reactor and collected in a reaction liquid storage tank to obtain a LiHCO3 solution, which is filtered through a precision filter membrane and then injected into an exchange column filled with a cationic resin through a metering pump to receive the feed liquid to obtain a purified LiHCO3 solution;

[0015] 3) The purified LiHCO3 solution is then heated and decomposed to remove CO2 gas, and the resulting Li2CO3 precipitate is centrifuged, washed, dried and crushed to obtain a battery-grade Li2CO3 product.

[0016] Furthermore, the particle size of the industrial-grade Li2CO3 used in step 1) ranges from 1.0 μm to 25.0 μm, and the mass ratio of industrial-grade Li2CO3 to deionized water is 1:20-25.

[0017] Furthermore, in step 1), the feed temperature of slurry a is 5-25°C, and the feed temperature of the mixed gas is 5-25°C.

[0018] Furthermore, in step 1), the molar flow ratio of Li2CO3 to CO2 and air in the carbonization reaction is in the range of 1.0:1.0-1.6:0.3-0.6.

[0019] Furthermore, in step 1), the temperature range of the carbonization reaction is 5.0-25.0° C.; the back pressure range in the reactor is 0.1-1.5 MPa, preferably 0.6-0.8 MPa; and the residence time of the reaction solution is 0.5-1.5 min.

[0020] Furthermore, a gas microbubble plate is provided at the bottom of the microbubble vertical reactor, and the slurry a and the mixed gas are respectively inputted into the upper and lower sides of the gas microbubble plate, and the aeration pore size of the gas microbubble plate ranges from 0.1 μm to 30.0 μm.

[0021] Furthermore, the microbubble vertical reactor includes a vertical reaction pipe with an inner diameter of 1.0-10.0 cm.

[0022] The present invention also provides a device for preparing pure Li2CO3 by continuous flow carbonization reaction during the carbonization process for purifying industrial Li2CO3, comprising a slurry control and delivery module, a gas control and delivery module, a gas distribution module, and a reactor main module. The reactor main module includes a vertical reaction pipe, a backpressure valve, a reaction liquid storage tank, and a circulating heat exchange device. The top outlet of the vertical reaction pipe is connected to the reaction liquid storage tank by a pipeline via the backpressure valve; a heat exchange jacket is provided on the outside of the vertical reaction pipe, and the inlet and outlet of the heat exchange jacket are respectively connected to the circulating heat exchange device via pipelines. The internal diameter of the vertical reaction pipe ranges from 1.0 to 10 cm. The slurry control and delivery module includes a batching tank and a metering pump, which delivers slurry a in the batching tank to the bottom of the vertical reaction pipe. The gas control and delivery module includes an air cylinder, a CO2 cylinder, a gas flow meter, a gas mixer, and a gas temperature control system; the air cylinder and the CO2 cylinder are connected to the gas mixer through a gas flow meter by a pipeline, and the mixed gas discharged from the gas mixer is adjusted in temperature by the gas temperature control system and then input into the bottom of the vertical reaction pipeline.

[0023] The beneficial effects achieved by the present invention are:

[0024] Compared to conventional kettle processes, the continuous flow tube carbonization technology employed in this invention enhances the flow rate of the mixed gas by bubbling air to prevent slurry settling (the addition of air replaces carbon dioxide to enhance fluidization, thereby saving and reducing carbon dioxide consumption). It also enhances the mass and heat transfer processes of the carbonization reaction, facilitates automated operation, and improves production process safety. The carbonization reaction time is shortened from several hours to tens of seconds, significantly improving efficiency while significantly reducing CO2 consumption, making it a more low-carbon and environmentally friendly process highly suitable for industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic structural diagram of a device for preparing pure Li2CO3 by continuous flow carbonization reaction in the process of purifying industrial Li2CO3 by carbonization method provided by the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0027] Example: See Figure 1

[0028] The present application provides a device for preparing pure Li2CO3 by continuous flow carbonization reaction in the process of purifying industrial Li2CO3 by carbonization method, which includes a slurry control and delivery module A, a gas control and delivery module B, a gas distribution module C and a reactor main body module D.

[0029] The reactor main module D includes a vertical reaction pipe D1, a back-pressure valve D3, a reaction liquid storage tank D4 and a circulating heat exchange device D5. The top outlet of the vertical reaction pipe D1 is connected to the reaction liquid storage tank D4 by a pipeline through the back-pressure valve D3; a heat exchange jacket D2 is provided on the outside of the vertical reaction pipe D1, and the inlet and outlet of the heat exchange jacket D2 are respectively connected to the circulating heat exchange device D5 through pipelines. The circulating heat exchange device D5 controls the temperature of the heat exchange fluid entering the heat exchange jacket D2, thereby regulating the temperature of the vertical reaction pipe D1.

[0030] The slurry control and delivery module A includes a batching tank A1 and a metering pump A2. The metering pump A2 delivers the slurry a in the batching tank A1 to the bottom of the vertical reaction pipe D1.

[0031] The gas control and delivery module B includes an air cylinder B1, a CO2 cylinder B2, a gas flow meter B3, a gas mixer B4, and a gas temperature control system B5; the air cylinder B1 and the CO2 cylinder B2 are both connected to the gas mixer B4 by pipelines through the gas flow meter B3, and the mixed gas discharged from the gas mixer B4 is temperature-regulated by the gas temperature control system B5 and then input into the bottom of the vertical reaction pipe D1.

[0032] The gas distribution module C includes a gas microbubble plate C1 disposed at the bottom of the vertical reaction pipe D1, and the gas microbubble plate C1 is used to distribute gas microbubbles.

[0033] In this embodiment of the present invention, the flow rate input value of the gas mass flow controller is set, and the molar amount of each gas input per unit time is calculated based on the controller's standard conversion coefficients for different gases. The molar amount of input per unit time is converted based on the density of the slurry with different ratios. Finally, the molar flow ratio of Li2CO3, CO2, and air in the carbonization reaction is calculated.

[0034] Example 1

[0035] 5.0kg of industrial-grade Li2CO3 (purity 99.50%, average particle size 20μm) was added in batches to a batch tank containing 100.0L of deionized water. Slurry a was prepared under stirring and the temperature was controlled at around 20°C. Slurry a was injected into a vertical reaction pipe (inner diameter 1.5cm) via a metering pump A2 (slurry flow rate of 40mL / min). Air cylinder B1 and CO2 gas cylinder B2 were opened and the respective gas flow rates were controlled to 0.30L / min and 1.0L / min by mass flow controllers. The molar flow ratio of Li2CO3 to CO2 and air was 1.0:1.25:0.51. After flowing through a gas mixer, the inlet temperature was controlled to 15°C by a gas temperature control system B5, and microbubbles were distributed through a gas microbubble plate C1 (aeration pore size 30μm). The heat exchange jacket D2 controlled the reaction temperature at 20°C, and the back pressure valve D3 was adjusted to maintain the reaction system pressure at 0.6MPa. The reaction solution is retained for 90 seconds. Once the operation stabilizes, the reaction solution is collected and placed in reaction solution storage tank D4. The reaction solution is clarified to obtain a LiHCO3 solution. The LiHCO3 solution is filtered through a 2.5μm precision filter membrane and then injected into an exchange column filled with a cationic resin via a metering pump. This receives the feed solution to obtain a purified LiHCO3 solution. The purified LiHCO3 solution is heated to 95°C with stirring and allowed to react for 90 minutes, releasing a large amount of CO2. The resulting Li2CO3 precipitate mixture is centrifuged, washed, dried, and crushed to obtain a battery-grade Li2CO3 product.

[0036] Example 2

[0037] Under stirring, 5.0kg of technical-grade Li2CO3 (purity 99.5%, average 5μm) was added to a batch tank containing 125.0L of deionized water to prepare slurry a. The slurry a temperature was controlled to 10°C and the slurry a was stirred thoroughly to mix. Slurry a was injected into a reaction vertical pipeline (inner diameter 1.5cm) by metering pump A2 (flow rate of 40mL / min). At the same time, air cylinder B1 and CO2 gas cylinder B2 were opened and their respective gas flow rates were adjusted to 0.29L / min and 0.74L / min by mass flow controllers. The molar flow ratio of Li2CO3 to CO2 and air was 1.0:1.15:0.6. After the gases were mixed, the inlet temperature was brought to 10°C by gas temperature control system B5. Finally, gas microbubbles (aeration pore size 5μm) were distributed using gas microbubble plate C1. Heat exchange jacket D2 was regulated to maintain the reaction temperature at approximately 10°C, and back pressure valve D3 was adjusted to maintain the reaction system pressure at 0.8 MPa. After stable operation, the reaction solution was placed in reaction liquid storage tank D4 after a residence time of 80 seconds. The reaction solution was clarified and its pH was measured to be 7.2, yielding a LiHCO solution. Purification and thermal cracking (specific steps are the same as in Example 1) yielded a battery-grade LiCO product.

[0038] Example 3

[0039] Weigh 5.0kg technical grade Li2CO3 (purity 99.5%, average particle size 1 μm) and add 100.0L centrifugal mother liquor (being the Li2CO3 precipitated mixed liquor of embodiment 1 through centrifugal mother liquor) in the batch tank under agitation to prepare slurry a, control slurry a temperature to be 10 ℃, stir thoroughly and make it mix.Slurry a is injected into vertical reaction pipeline (internal diameter 3.0cm) through metering pump A2 (slurry flow rate is 80mL / min), open air cylinder B1 and CO2 gas cylinder B2 simultaneously, and it is 0.6L / min and 2.4L / min respectively to control gas flow rate by mass flow controller, Li2CO3 and CO2 and the molar flow ratio of air is: 1.0:1.50:0.51, and it is 10 ℃ to control inlet temperature by gas temperature control system B5 after gas mixer, and microbubble (aeration aperture 0.1 μm) is distributed through gas microbubble plate C1. Heat exchange jacket D2 was used to control the reaction temperature at 10°C, and back pressure valve D3 was adjusted to maintain the reaction system pressure at 0.8 MPa. After stabilization, the reaction solution was collected and placed in reaction solution storage tank D4 after a residence time of 60 seconds. The reaction solution clarified and measured a pH of 7.2, yielding a LiHCO3 solution. Purification and thermal cracking (specific steps are the same as in Example 1) yielded a battery-grade Li2CO3 product.

[0040] Example 4

[0041] Weigh 5.0kg industrial grade Li2CO3 (purity 99.5%, average particle size 5μm) and add it to a batch tank filled with 100.0L deionized water to prepare slurry a. The slurry temperature is controlled to 15°C and stirred thoroughly to mix evenly. Then, it is injected into a vertical reaction pipe (inner diameter 1.5cm) via a metering pump A2 (slurry flow rate is 40mL / min). Open the CO2 gas cylinder B2 and control its input temperature to 15°C. Adjust the mass flow controller parameter to 0.9L / min, the Li2CO3 and CO2 molar flow ratio to 1.0:1.12, and distribute microbubbles through the gas microbubble plate C1 (aeration pore size 5μm). Use a heat exchange jacket D2 to control the reaction temperature to 15°C, and adjust the back pressure valve D3 to control the reaction system pressure to 0.8MPa. After the operation is stable, the reaction solution is received and placed in the reaction solution storage tank D4 after a residence time of 120s. The reaction solution is clarified. After purification and thermal cracking of the LiHCO solution (the specific steps are the same as in Example 1), a battery-grade LiCO product with a purity of 99.93% and a yield of 87.5% was obtained. Operational stability testing showed that after several hours of operation, the pump pressure of metering pump A2 increased, and the concentration of the lithium bicarbonate solution at the outlet of the feed liquid deviated significantly from the theoretical value, resulting in a low overall yield. Furthermore, the deposition volume of slurry a in the reactor deviated from the liquid holdup volume.

[0042] Further optimization was performed by adding air to enhance fluidization and reducing the amount of carbon dioxide used, and good stability was achieved in the long-term operation of Examples 1, 2, and 3.

[0043] In order to test the effect of continuous flow carbonization reaction on product quality, the content of Li2CO3 products of Examples 1 to 3 was measured, and the results are shown in the following table:

[0044] plan Example 1 Example 2 Example 3 <![CDATA[Li2CO3 purity]]> 99.91％ 99.95％ 99.90％ <![CDATA[Li2CO3 yield]]> 95.0％ 94.5％ 95.3％

[0045] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the protection scope of the present invention should not be considered as being limited to the specific forms described in the embodiments.

Claims

1. A process for preparing pure Li2CO3 by continuous flow carbonization reaction in the process of purifying industrial Li2CO3 by carbonization, characterized by comprising the following steps: 1) Industrial-grade Li2CO3 and deionized water are mixed and stirred thoroughly in a batching tank to prepare slurry a. The flow rate of slurry a is controlled by a metering pump, and slurry a is continuously fed into the bottom of a microbubble vertical reactor. A gas microbubble plate is provided at the bottom of the microbubble vertical reactor. Slurry a and mixed gas are respectively fed into the upper and lower sides of the gas microbubble plate. The aeration pore size of the gas microbubble plate ranges from 0.1 μm to 30.0 μm. The microbubble vertical reactor includes a vertical reaction pipe with an inner diameter of 1.0 to 3.0 cm. The flow rates of CO2 and air are respectively controlled by a gas flow meter. The CO2 and air are mixed in a gas mixer and then blown into the bottom of a microbubble vertical reactor. By adjusting the internal pressure of the reactor, the CO2 microbubbles and slurry a are fully contacted in the reactor to cause a carbonization reaction. In step 1), the feed temperature of slurry a is 5-25°C, the inlet temperature of the mixed gas is 5-25°C, the molar flow ratio of Li2CO3 to CO2 and air in the carbonization reaction is in the range of 1.0:1.0-1.6:0.3-0.6; the temperature range of the carbonization reaction is 5.0-25.0°C; the back pressure in the reactor is in the range of 0.6-0.8 MPa, and the residence time of the reaction liquid is in the range of 0.5-1.5 min; 2) The reaction liquid is discharged from the top of the reactor and collected in a reaction liquid storage tank to obtain a LiHCO3 solution. After filtering through a precision filter membrane, it is injected into an exchange column filled with a cationic resin through a metering pump to receive the feed liquid to obtain a purified LiHCO3 solution; 3) The purified LiHCO3 solution is then heated and decomposed to remove CO2 gas. The resulting Li2CO3 precipitate is centrifuged, washed, dried and crushed to obtain battery-grade Li2CO3 product.

2. The process for preparing pure Li2CO3 by continuous flow carbonization reaction in the process of purifying industrial Li2CO3 by carbonization as claimed in claim 1, characterized in that The particle size of the industrial-grade Li2CO3 used in step 1) ranges from 1.0 μm to 25.0 μm, and the mass ratio of industrial-grade Li2CO3 to deionized water is 1:20-25.

0.

3. A device for preparing pure Li2CO3 by continuous flow carbonization reaction in a process of purifying industrial Li2CO3 by carbonization method based on the process of claim 1, characterized in that It includes a slurry control and delivery module (A), a gas control and delivery module (B), a gas distribution module (C) and a reactor main module (D); The reactor main module (D) includes a vertical reaction pipe (D1), a back pressure valve (D3), a reaction liquid storage tank (D4), and a circulating heat exchange device (D5). The top outlet of the vertical reaction pipe (D1) is connected to the reaction liquid storage tank (D4) via a pipeline through the back pressure valve (D3). A heat exchange jacket (D2) is provided on the outside of the vertical reaction pipe (D1), and the inlet and outlet of the heat exchange jacket (D2) are respectively connected to the circulating heat exchange device (D5) via pipelines. The slurry control and delivery module (A) includes a batching tank (A1) and a metering pump (A2), and the metering pump (A2) delivers the slurry a in the batching tank (A1) to the bottom of the vertical reaction pipe (D1); The gas control and delivery module (B) includes an air cylinder (B1), a CO2 cylinder (B2), a gas flow meter (B3), a gas mixer (B4), and a gas temperature control system (B5); the air cylinder (B1) and the CO2 cylinder (B2) are both connected to the gas mixer (B4) via a gas flow meter (B3) by a pipeline, and the mixed gas discharged from the gas mixer (B4) is temperature-regulated by the gas temperature control system (B5) and then input into the bottom of the vertical reaction pipe (D1).

4. The device according to claim 3, characterized in that The inner diameter of the vertical reaction pipe (D1) ranges from 1.0 to 10 cm. The gas distribution module (C) includes a gas microbubble plate (C1) arranged at the bottom of the vertical reaction pipe (D1), and the gas microbubble plate (C1) is used to distribute gas microbubbles.

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