Energy-saving lithium extraction method and device

Abstract

The present application relates to the technical field of metal extraction equipment by electrochemical deintercalation method, and particularly relates to an energy-saving lithium extraction method, which comprises the following steps: setting a reflux device on the basis of a conventional electrochemical lithium extraction method.The present application has the beneficial effect of reducing energy consumption while ensuring lithium extraction efficiency.

Description

Technical Field

[0001] This invention relates to the field of electrochemical metal extraction equipment technology, and in particular to an energy-saving lithium extraction method and apparatus. Background Technology

[0002] With the depletion of non-renewable energy sources, the development and utilization of new energy sources is an inevitable trend. New energy vehicles, as a typical representative of new energy development and utilization, have experienced rapid growth in recent years and will eventually surpass the market share of traditional gasoline vehicles, gradually replacing them. Lithium, as an essential energy metal for the power systems of new energy vehicles, will also see a dramatic increase in market demand. The efficient, clean, and low-cost mining of lithium resources is crucial for the sustainable development of the new energy vehicle industry.

[0003] Lithium resources exist in nature mainly in the form of ores and salt lake brines, with salt lake brines accounting for more than 80% of the total lithium reserves.

[0004] CN 102382984 A proposes a new electrochemical deintercalation method for lithium extraction from salt lakes. This method utilizes the working principle of aqueous lithium batteries, employing a delithiated battery cathode material with a "memory effect" for lithium ions as the electrode material, salt lake brine as the cathode electrolyte, and a magnesium-free supporting electrolyte as the anode electrolyte. This forms an electrochemical deintercalation system for lithium extraction. To address industrial production challenges, a tank, termed a deintercalation tank, is proposed. This tank holds the brine, other lithium-to-lime solutions, and a lithium-enriched solution, enabling the electrochemical deintercalation process for lithium extraction from salt lakes to be completed within it.

[0005] Analysis reveals that the electro-adsorption process of lithium on the cathode side involves two steps:

[0006] 1. Lithium ions move to the vicinity of the electrode under the influence of an electric field;

[0007] 2. Under the influence of an electric field, lithium ions near the electrode undergo an oxidation-reduction reaction with the adsorbent material on the electrode plate, and lithium ions in the liquid to be extracted are embedded into the adsorbent material of the electrode.

[0008] On the anode side, the process of lithium ion extraction consists of two steps:

[0009] 1. Under the influence of an electric field, the adsorbent material on the electrode plate undergoes a redox reaction, and lithium ions are released from the adsorbent material on the electrode.

[0010] 2. Lithium ions enter the lithium-rich solution from the electrode under the influence of an electric field;

[0011] In practice, it was found that the adsorption efficiency when the liquid is still is lower than that when the liquid is flowing. This is because the reaction occurs only on the electrode plate surface; a still liquid results in a low local ion concentration on the electrode plate surface, leading to low efficiency. Furthermore, since each lithium adsorption occurs only on the electrode plate surface, the amount adsorbed in a single instance is very small. Therefore, a continuous supply of fresh solution is needed to the electrode plate coating material. On the cathode side, lithium ions in the disturbed lithium-to-extract solution continuously reach the electrode surface and embed into the electrode material; on the anode side, lithium ions in the electrode material are released under the influence of the electric field and enter the lithium-rich solution, rapidly leaving the electrode surface. Maintaining the continuous reaction requires constantly pumping the lithium-to-extract solution and / or the lithium-rich solution into the electrochemical desorption device, a process that consumes a significant amount of energy.

[0012] To further optimize and improve the equipment, making it more efficient and energy-saving, we conducted a more detailed analysis of the overall process:

[0013] Taking a lithium-intercalated cathode chamber as an example, the reaction process of inserting lithium ions from the lithium-to-lime solution into the lithium-deficient cathode occurs within the cathode chamber. From the perspective of mass transfer, the surface of the electrode and the surrounding liquid layer can be roughly divided into the electric double layer, the diffusion layer, and the convection layer. Since brines are high-concentration lithium salt solutions, the electric double layer is usually very thin and can be ignored. The main mass transfer mechanisms in the diffusion layer region are electromigration and diffusion; its thickness is typically 10 mm. -3 ~10 -2 cm. From a macroscopic perspective, it is very close to the electrode surface. According to fluid mechanics, in a flow layer so close to the electrode surface, the convection velocity of the liquid is very small, and the closer to the electrode surface, the smaller the convection velocity. Therefore, the mass transfer effect of convection in this region is very small. When the solution contains a large amount of non-lithium electrolyte, the reacting ions Li... + The transport number is very small, and the electromigration mass transfer of reactant ions is negligible; diffusion mass transfer is the main mass transfer mechanism in the diffusion layer. The liquid layer near the surface of the reactant electrode is primarily a diffusion layer. The region outside this is the convection zone, where the concentrations of various substances are the same as in the bulk solution. Typically, convective mass transfer in this region is far greater than electromigration mass transfer, and the latter's effect is negligible. It can generally be considered that convective mass transfer plays a dominant role in this region.

[0014] Therefore, it is evident that during the reaction of brine on the electrode surface, the large amount of convection layer does not contribute to the reaction and consumes a significant amount of electrical energy. How to reduce energy consumption while maintaining a constant reaction rate has become a pressing problem for those skilled in the art.

[0015] Therefore, there is an urgent need for an energy-saving lithium extraction method and apparatus to solve the problems existing in the current technology. Summary of the Invention

[0016] The purpose of this invention is to provide an energy-saving lithium extraction method that reduces energy consumption while maintaining a constant reaction rate.

[0017] An energy-saving lithium extraction method includes the following steps: based on the conventional electrochemical lithium extraction method, a reflux device is set up to reduce the overall fluid flow rate while ensuring the electrochemical reaction rate, so as to achieve the purpose of energy saving.

[0018] Furthermore, the reflux device employs at least one of the following: a baffle plate disposed between the electrode plates and a reflux pipe disposed between the inlet and the outlet.

[0019] Preferably, when the reflux device uses a reflux pipe located between the inlet and outlet, a liquid separator is installed on the reflux pipe. The liquid separator is used to guide the fluid reflux. The advantage of this configuration is that it increases the flow rate without requiring a reflux pump.

[0020] Preferably, the liquid separation device employs at least one of a flow divider baffle and a three-way regulating valve.

[0021] An energy-saving lithium extraction device includes a deintercalation tank, one or more pairs of cathode plates and anode plates, an anion exchange membrane, and a reflux pipe; the cathode plates and anode plates are both disposed inside the deintercalation tank, the anion exchange membrane is disposed between each pair of cathode plates and anode plates, and the two ends of the reflux pipe are respectively connected to the liquid inlet and the liquid outlet of the deintercalation tank.

[0022] The return pipe guides a portion of the liquid flowing out of the outlet back to the inlet. This is done to reduce the overall fluid flow rate and lower energy consumption while maintaining the liquid flow velocity near the electrode plate.

[0023] Furthermore, the return pipe is equipped with a liquid distribution device, which is at least one of a diversion baffle and a three-way regulating valve.

[0024] Preferably, the reflux pipe is equipped with a three-way regulating valve, which can be used to adjust the reflux ratio.

[0025] Preferably, the reflux ratio is 0-90% (excluding 0), because the concentration of lithium ions in various lithium extraction solutions is different. A higher concentration requires a larger reflux ratio because more ions in the solution can participate in the electrochemical reaction; a lower concentration requires a smaller reflux ratio so that as much fresh solution as possible enters the extraction tank, and more lithium ions have the opportunity to participate in the electrochemical reaction at the electrode interface.

[0026] Preferably, the angle θ between the connection between the reflux pipe and the outlet pipe is an acute angle.

[0027] Furthermore, a reflux pump is installed on the reflux pipe.

[0028] Furthermore, the surfaces of the cathode plate and the anode plate are coated with an adsorbent material.

[0029] Furthermore, a water distribution net is provided on the surface of the cathode plate and the anode plate for uniform water distribution.

[0030] The beneficial effects of this invention are as follows:

[0031] Reduce energy consumption while ensuring lithium extraction efficiency. Attached Figure Description

[0032] Figure 1 1. Schematic diagram of the extraction groove structure;

[0033] Figure 2 1 is a schematic diagram of the structure of Example 1;

[0034] Figure 3 1 is a schematic diagram of the structure of Example 2;

[0035] Figure 4 1 is a schematic diagram of the structure of Example 3;

[0036] Figure 5 1. A schematic diagram of the connection structure between the outlet pipe and the return pipe;

[0037] Figure 6 Circulating pump performance curves. Detailed Implementation

[0038] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0039] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] like Figure 1 , 2 As shown in Figure 5, an energy-saving lithium extraction device includes a deintercalation tank 1, one or more pairs of cathode plates 15 and anode plates 16, an anion exchange membrane 17, and a reflux pipe 2. The cathode plates 15 and anode plates 16 are both disposed inside the deintercalation tank 1, the anion exchange membrane 17 is disposed between each pair of cathode plates 15 and anode plates 16, and the two ends of the reflux pipe 2 are respectively connected to the liquid inlet 12 and the liquid outlet 11 of the deintercalation tank 1.

[0042] The return pipe 2 guides a portion of the liquid flowing out of the outlet 11 back to the inlet 12. The purpose of this is to reduce the overall fluid flow rate and lower energy consumption while maintaining the liquid flow rate near the electrode plate.

[0043] Preferably, the angle θ between the connection between the return pipe 2 and the inlet pipe is an acute angle.

[0044] In this embodiment, the surfaces of the cathode plate 15 and the anode plate 16 are coated with an adsorption material.

[0045] In this embodiment, the surfaces of the cathode plate 15 and the anode plate 16 are provided with water distribution nets for uniform water distribution.

[0046] The cathode and anode surfaces are provided with water distribution nets to uniformly distribute water, thereby agitating the solution and enhancing the mass transfer of lithium ions within the solution.

[0047] Example 2

[0048] like Figure 1 , 3 As shown in Figure 5, an energy-saving lithium extraction device includes a deintercalation tank 1, one or more pairs of cathode plates 15 and anode plates 16, an anion exchange membrane 17, and a reflux pipe 2. The cathode plates 15 and anode plates 16 are both disposed inside the deintercalation tank 1, the anion exchange membrane 17 is disposed between each pair of cathode plates 15 and anode plates 16, and the two ends of the reflux pipe 2 are respectively connected to the liquid inlet 12 and the liquid outlet 11 of the deintercalation tank 1.

[0049] The return pipe 2 guides a portion of the liquid flowing out of the outlet 11 back to the inlet 12. The purpose of this is to reduce the overall fluid flow rate and lower energy consumption while maintaining the liquid flow rate near the electrode plate.

[0050] In this embodiment, the reflux pipe 2 is equipped with a liquid distribution device, which is a three-way regulating valve 21.

[0051] Preferably, the reflux pipe 2 is provided with a three-way regulating valve 21, which can be used to adjust the reflux ratio.

[0052] Preferably, the reflux ratio is 0-90% (excluding 0), because the concentration of lithium ions in various lithium extraction solutions is different. A higher concentration requires a larger reflux ratio because more ions in the solution can participate in the electrochemical reaction; a lower concentration requires a smaller reflux ratio so that more fresh solution can enter the extraction tank 1, and more lithium ions can participate in the electrochemical reaction at the electrode interface.

[0053] Preferably, the angle θ between the connection between the return pipe 2 and the inlet pipe is an acute angle.

[0054] In this embodiment, the surfaces of the cathode plate 15 and the anode plate 16 are coated with an adsorption material.

[0055] In this embodiment, the surfaces of the cathode plate 15 and the anode plate 16 are provided with water distribution nets for uniform water distribution.

[0056] The cathode and anode surfaces are provided with water distribution nets to uniformly distribute water, thereby agitating the solution and enhancing the mass transfer of lithium ions within the solution.

[0057] Example 3

[0058] like Figure 1 , 4 As shown in Figure 5, an energy-saving lithium extraction device includes a deintercalation tank 1, one or more pairs of cathode plates 15 and anode plates 16, an anion exchange membrane 17, and a reflux pipe 2. The cathode plates 15 and anode plates 16 are both disposed inside the deintercalation tank 1, the anion exchange membrane 17 is disposed between each pair of cathode plates 15 and anode plates 16, and the two ends of the reflux pipe 2 are respectively connected to the liquid inlet 12 and the liquid outlet 11 of the deintercalation tank 1.

[0059] The return pipe 2 guides a portion of the liquid flowing out of the outlet 11 back to the inlet 12. The purpose of this is to reduce the overall fluid flow rate and lower energy consumption while maintaining the liquid flow rate near the electrode plate.

[0060] In this embodiment, the reflux pipe 2 is equipped with a liquid distribution device, which is a three-way regulating valve 21.

[0061] Preferably, the reflux pipe 2 is provided with a three-way regulating valve 21, which can be used to adjust the reflux ratio.

[0062] Preferably, the reflux ratio is 0-90% (excluding 0), because the concentration of lithium ions in various lithium extraction solutions is different. A higher concentration requires a larger reflux ratio because more ions in the solution can participate in the electrochemical reaction; a lower concentration requires a smaller reflux ratio so that more fresh solution can enter the extraction tank 1, and more lithium ions can participate in the electrochemical reaction at the electrode interface.

[0063] Preferably, the angle θ between the connection between the return pipe 2 and the inlet pipe is an acute angle.

[0064] In this embodiment, a return pump 22 is provided on the return pipe 2.

[0065] In this embodiment, the surfaces of the cathode plate 15 and the anode plate 16 are coated with an adsorption material.

[0066] In this embodiment, the surfaces of the cathode plate 15 and the anode plate 16 are provided with water distribution nets for uniform water distribution.

[0067] The cathode and anode surfaces are provided with water distribution nets to uniformly distribute water, thereby agitating the solution and enhancing the mass transfer of lithium ions within the solution.

[0068] To illustrate the beneficial effects of the present invention, Comparative Example 1 is provided;

[0069] Comparative Example 1

[0070] Comparative Example 1 is an existing electrochemical electrolyzer. The only difference between Comparative Example 1 and Example 2 is that a reflux pipe is not installed. All other conditions remain the same.

[0071] To further illustrate the beneficial effects of the present invention, Example 2 and Comparative Example 1 were tested under the same conditions:

[0072] I. Verification of the effect of reflux ratio on lithium extraction efficiency in a single reaction

[0073] 1. Equipment required for the preparation of Example 2 and Comparative Example 1

[0074] 18 sheets of TA1 rhombic pure titanium mesh, 1mm thick, were cut to a size of 20cm × 17cm. LiFePO4, acetylene black, and PVDF were mixed evenly in a weight ratio of 8:1:1. N-methylpyrrolidone (NMP) organic solvent was added and ground into a slurry. This slurry was then coated onto the titanium mesh (10 meshes had a coating density of 1 unit, and the other 8 meshes had a coating density of 1 / 3 unit). The coating density for the LFP electrode was 80 g / cm³. 2 Then, they were placed in a vacuum drying oven, evacuated, heated to 110℃ and dried for 12 hours. After cooling, the prepared lithium iron phosphate electrode was obtained.

[0075] Nine integral electrodes coated with lithium iron phosphate were randomly selected (five with a coating density of 1 unit and four with a coating density of 1 / 3 unit). Using nickel foam as the cathode, the electrodes were placed in 1 L of NaCl solution with a concentration of 20 g / L. A voltage of less than 1.0 V was applied to both ends of the titanium electrode and the nickel foam for 12 h. The processing voltage of each electrode was kept the same (the current applied to the electrode with the lower coating density was kept to be 1 / 3 of the current of the other electrode). The lithium in the lithium iron phosphate coated on the titanium mesh was extracted to form an iron phosphate ion sieve electrode, which was then used as the cathode.

[0076] Using a prepared lithium iron phosphate electrode as the anode and a prepared iron phosphate ion sieve electrode as the cathode, the apparatus was placed in a deintercalation / intercalation tank, with water distribution nets placed on both sides of the anode and cathode electrodes. This is the apparatus described in Comparative Example 1. They are respectively referred to as Comparative Example 1-1 and Comparative Example 1-2.

[0077] Similarly, a return pipe is connected between the inlet and outlet, and a three-way regulating valve is installed. This is the device described in Example 2. These are respectively referred to as Example 2-1 and Example 2-2.

[0078] 2. Set up experimental tests

[0079] The following operations are performed in the above-mentioned device:

[0080] The cathode is placed in a LiCl solution containing 90 g / L Na under the experimental conditions. + The anode was placed in a NaCl supporting electrolyte of 10 g / L, and the test temperature was 26℃ and the humidity was 60%.

[0081] The experimental results are as follows:

[0082] Table 1. Results of Lithium Extraction Tests for a Single Reaction

[0083]

[0084]

[0085] The experimental data above show that even a 0.5 g / L difference in the concentration of the input lithium solution to be extracted can still maintain the same current density. This indicates that after a single cycle of the solution in each chamber, the change in lithium concentration in the lithium solution to be extracted is very small, and the small change in solution concentration after each reaction has little effect on the current density inside the deintercalation / extraction tank.

[0086] Therefore, adjusting the reflux ratio will not affect the lithium extraction result of a single reaction.

[0087] II. Verifying the impact of reflux ratio on power consumption

[0088] 1. Equipment required for the preparation of Example 2 and Comparative Example 1

[0089] To highlight the differences in experimental results, a number of larger devices were specially designed.

[0090] Select TA1 rhombic pure titanium mesh, 1mm thick, and cut 1m. 2 A total of 100 sheets were prepared. LiFePO4, acetylene black, and PVDF were mixed evenly in a weight ratio of 8:1:1. N-methylpyrrolidone (NMP) organic solvent was added and ground into a slurry. This slurry was then coated onto a titanium mesh. The LFP electrode coating density was 80 g / cm³. 2 Then, they were placed in a vacuum drying oven, evacuated, heated to 110℃ and dried for 12 hours. After cooling, the prepared lithium iron phosphate electrode was obtained.

[0091] Fifty sheets of the above-mentioned lithium iron phosphate coated integral electrode were randomly selected and placed in 1L of NaCl solution with a concentration of 20g / L using nickel foam as the cathode. A voltage of less than 1.0V was applied to both ends of the titanium electrode and the nickel foam for 12h, and the processing voltage of each electrode was kept the same. The lithium in the lithium iron phosphate coated on the titanium mesh was extracted to form an iron phosphate ion sieve electrode, which was used as the cathode.

[0092] Using the prepared lithium iron phosphate electrode as the anode and the prepared iron phosphate ion sieve electrode as the cathode, the apparatus was placed in a deintercalation / deintercalation tank, with water distribution nets placed on both sides of the anode and cathode electrodes. This is the apparatus described in Comparative Example 1.

[0093] A reflux pipe is connected between the inlet and outlet, and a three-way regulating valve is installed. This is the device described in Example 2.

[0094] 2. Set up experimental tests

[0095] The following operations are performed in the above-mentioned device:

[0096] The lithium ion concentration of the lithium extraction solution is 0.8 g / L (of which the NaCl concentration is 10 g / L); the NaCl concentration of the lithium-rich solution is 10 g / L, and the temperature is 20℃.

[0097] The pumps supplying liquid to the extraction tanks are all 40FUH-50S-20 / 35 engineering plastic horizontal pumps from Yixing Linggu Plastic Equipment Co., Ltd. See the attached performance curves for the pumps. Figure 6 .

[0098] Separate experiments were conducted to compare lithium extraction processes. The initial applied current, reaction cutoff current, composition of the lithium extraction solution, thickness of the basic coating material, flow rate, and other conditions, as well as the average electrode current density during the reaction, are shown in Table 2 below.

[0099] Table 1 Energy Consumption Parameters

[0100]

[0101] It is evident that by selecting different reflux ratios for different lithium solutions, while maintaining the overall lithium extraction efficiency (expressed as current density here) unchanged, the deintercalation pump with a reflux pipe consumes relatively less electrical energy compared to the setup without a reflux pipe, thus achieving the effect of saving electrical energy.

[0102] In summary, setting a reflux can reduce energy consumption while ensuring lithium extraction efficiency.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An energy-saving lithium extraction method, characterized in that, The process includes the following steps: based on the conventional electrochemical lithium extraction method, a reflux device is set up; the reflux device is a reflux pipe set between the inlet and outlet of the deintercalation tank.

2. The energy-saving lithium extraction method according to claim 1, characterized in that, A liquid separation device is installed on the reflux pipe.

3. The energy-saving lithium extraction method according to claim 2, characterized in that, The liquid separation device employs at least one of a flow divider baffle and a three-way regulating valve.

4. An energy-saving lithium extraction device, characterized in that, It includes a deintercalation tank (1), one or more pairs of cathode plates (15) and anode plates (16), an anion exchange membrane (17), and a reflux pipe (2); the cathode plates (15) and anode plates (16) are both disposed inside the deintercalation tank (1), the anion exchange membrane (17) is disposed between each pair of cathode plates (15) and anode plates (16), and the two ends of the reflux pipe (2) are connected to the liquid inlet (12) and the liquid outlet (11) of the deintercalation tank (1), respectively.

5. The energy-saving lithium extraction device according to claim 4, characterized in that, The return pipe (2) is equipped with a liquid distribution device, which is at least one of a diversion baffle and a three-way regulating valve (21).

6. The energy-saving lithium extraction device according to claim 4, characterized in that, The angle θ between the connection between the reflux pipe (2) and the outlet pipe (13) is an acute angle.

7. The energy-saving lithium extraction device according to claim 4, characterized in that, A reflux pump (22) is installed on the reflux pipe (2).

8. The energy-saving lithium extraction device according to claim 4, characterized in that, The cathode plate (15) and anode plate (16) are provided with water distribution nets for uniform water distribution.

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