Method and device for continuously preparing rare earth carbonate in asymmetric electrolytic cell

Abstract

The application discloses a method and device for continuously preparing rare earth carbonate in an asymmetric electrolytic cell, and belongs to the technical field of rare earth compound preparation. In the process of preparing rare earth carbonate by electrolysis, carbon dioxide is continuously introduced into the electrolytic cell for carbonization, and the prepared product is washed by ultrasonic waves, so that the prepared rare earth carbonate has a purity of greater than or equal to 99% and a chloride ion content of less than 200 ppm. The speed of the carbon dioxide entering the electrolytic cell is controlled, so that the solid-liquid two-phase in the cathode chamber of the electrolytic cell presents a fluidized state, and the mixed solution flows out from the liquid outlet on the cathode chamber, thereby improving the preparation efficiency of the rare earth carbonate and improving the utilization efficiency of the carbon dioxide gas to more than 80%. The distance between the cathode plate and the cation exchange membrane in the electrolytic cell is set, so that the electrolysis energy consumption per kilogram of rare earth carbonate is reduced by more than 70%. Meanwhile, the unreacted rare earth chloride is subjected to cyclic treatment, and the repeated utilization efficiency of the rare earth chloride solution is greatly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of rare earth compound preparation, and particularly relates to a method and device for continuously preparing rare earth carbonate in an asymmetric electrolytic cell. BACKGROUND

[0002] Rare earth compounds are known as "industrial vitamins" due to their unique physical and chemical properties and wide range of applications, playing a crucial role in modern science and technology and economic development. Rare earth compounds have excellent magnetic, optical, electrical, thermal, and other properties, and are widely used in high-performance permanent magnets, luminescent materials, catalysts, optical fiber communication, superconducting materials, glass-ceramic additives, and medical diagnosis and treatment. For example, neodymium-iron-boron permanent magnets are one of the strongest permanent magnets, widely used in electric motors, generators, computer disk drives, and other fields; rare earth fluorescent powder is widely used in LED lighting, displays, and televisions, improving display and lighting effects. In addition, rare earth compounds also have great potential in the field of environmental protection, such as wastewater treatment, air purification, and radioactive waste treatment. At the same time, rare earth elements also have important applications in new energy fields such as wind power generation, electric vehicles, and solar cells, which are of great significance to improving energy efficiency and environmental protection.

[0003] Patent CN118908263A discloses a kind of nano rare earth oxide and its preparation method. After the mixed solution of organic acid or organic acid salt solution and rare earth compound is reacted with precipitant, it is obtained after filtration, washing, drying and calcination. The preparation method provided by the invention controls the preparation of solution and the feeding mode of each raw material, introduces organic acid radical ion to form organic rare earth complex ion, accelerates the nucleation process, and controls the crystal growth process.

[0004] Patent CN117822003A discloses a device for continuously preparing rare earth compounds by electrochemical conversion of rare earth chlorides and its application. Through the design of the continuous electrochemical conversion device, the saturated rare earth chloride solution is one-step electrochemically converted to prepare rare earth hydroxide, oxide or rare earth carbonate. The invention realizes the preparation of rare earth compound materials from rare earth chloride solution in one step, realizes the circulation of aqueous solution, has no waste liquid discharge, and has no additional precipitant, eliminates the problems of repeated consumption of acid and alkali and wastewater treatment and discharge from the source, realizes the short process preparation of high-quality rare earth compounds, and realizes the recycling of raw materials.

[0005] Patent CN107190273A discloses a method for preparing rare earth oxide by electrochemical conversion of rare earth chloride, which comprises the following steps: pre-deacidification electrolysis of the rare earth chloride solution, return of hydrochloric acid to the rare earth production system; electrolysis of the pre-deacidified rare earth chloride solution as electrolyte, 10℃≤temperature<100℃, electrolysis voltage≥2.2V, carbon dioxide gas is introduced into the cathode chamber during electrolysis, and stirring is carried out, and rare earth carbonate is directly prepared; in the cathode chamber, the electrolyte and the rare earth carbonate flow directionally, and solid-liquid separation is carried out through a filtering device to obtain filtrate and rare earth carbonate, and the filtrate is recycled back to the cathode chamber; after drying, the rare earth carbonate is calcined to obtain CO2 gas and rare earth oxide product. The invention utilizes the electrolysis process, has simple process and low cost, recovers by-products hydrogen and chlorine to prepare hydrochloric acid which can be returned to the rare earth production system, and eliminates the pollution of ammonia nitrogen and other waste water, and finally high-purity rare earth oxide product is obtained.

[0006] In summary, the above-mentioned invention uses a precipitation method to prepare rare earth products, which is easy to cause pollution of waste water such as ammonia nitrogen; although the use of electrolysis to prepare rare earth oxide products can eliminate the pollution of waste water such as ammonia nitrogen, the problem of low utilization efficiency of carbon dioxide in the preparation of rare earth carbonate is not considered, the utilization efficiency of carbon dioxide is low, which not only increases the consumption of carbon dioxide, but also causes low purity of hydrogen produced in the cathode (less than 40%), and subsequent separation is difficult. Moreover, the above-mentioned method does not consider the problem of electrode distance, which increases the energy consumption of electrolysis. At the same time, the above-mentioned method does not consider the problem of the content of chloride ions in the obtained rare earth product, which leads to the decrease of the purity of the obtained rare earth compound. SUMMARY

[0007] In view of the above problems, the present application provides a method and device for continuously preparing rare earth carbonate in an asymmetric electrolytic cell to solve the problems of low utilization rate of carbon dioxide gas, low hydrogen purity, high electrolysis energy consumption and high chloride ion content in rare earth carbonate in the preparation process of rare earth carbonate.

[0008] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] A method for continuously preparing rare earth carbonate in an asymmetric electrolytic cell, comprising the following steps:

[0010] Step 1: the rare earth chloride solution flows into the anode chamber of the electrolytic cell through the overflow tank, and the sodium chloride solution continuously enters the cathode chamber of the electrolytic cell;

[0011] Step 2: carbon dioxide is introduced into the cathode chamber of the electrolytic cell to make the solution in the cathode chamber of the electrolytic cell flow;

[0012] Step 3: adjust the current size of the electrolytic cell to continuously perform carbonization electrolysis, and solid product and hydrogen are generated in the cathode chamber of the electrolytic cell, and chlorine is generated in the anode chamber of the electrolytic cell;

[0013] Step 4: The solid product is filtered by the filter press with sodium chloride solution, and the solid product enters the ultrasonic washing tank, the sodium chloride solution not involved in the reaction returns to the electrolytic tank for recycling, and the hydrogen and unreacted carbon dioxide are recovered;

[0014] Step 5: The rare earth chloride not involved in the reaction in the anode chamber of the electrolytic tank flows out from the cathode chamber of the electrolytic tank and enters the electrolytic tank again for recycling, and the chlorine gas is neutralized with the lye;

[0015] Step 6: The solid product entering the ultrasonic washing tank is ultrasonically washed to obtain the rare earth carbonate;

[0016] The electrolytic tank is provided with an anode chamber, an anode plate, a cation exchange membrane, a cathode chamber and a cathode plate, wherein the anode plate and the cathode plate adopt an asymmetric structure, the distance between the anode plate and the cation exchange membrane is 0, and the distance between the cathode plate and the cation exchange membrane is 1mm-10mm.

[0017] In step 1, the concentration of the rare earth chloride is 50g / L-350g / L, and the concentration of the sodium chloride solution is 20g / L-250g / L;

[0018] In step 2, the carbon dioxide is introduced at a rate of 10mL / min-200mL / min;

[0019] In step 3, the current density during the electrolysis is 600A / m 2 -1200A / m 2 ;

[0020] In step 5, the concentration of the unreacted rare earth chloride solution is 30g / L-300g / L;

[0021] In step 6, the ultrasonic washing conditions are as follows: the ultrasonic washing time is 10min-120min, the ultrasonic power is 100W-1000W, the cleaning temperature is 20℃-90℃, and the solid-liquid ratio of the cleaning liquid is (50-200):1;

[0022] The content of chloride ions in the rare earth carbonate is less than 200ppm, and the purity of the obtained rare earth carbonate is ≥99%;

[0023] In the method, the flow rate of the rare earth chloride solution and the sodium chloride solution entering or flowing out of the electrolytic tank is 0.5L / h-10L / h.

[0024] An asymmetric electrolytic tank continuous preparation device for rare earth carbonate is used to realize the above method, which comprises a high tank, a brine tank, an overflow tank, a circulating tank, an electrolytic tank, a filter press, an ultrasonic washing tank, a residual liquid tank, a lye tank, a carbon dioxide cylinder and a residual liquid barrel;

[0025] The electrolytic cell comprises a cathode chamber and an anode chamber; wherein the bottom of the cathode chamber is provided with a cathode chamber gas inlet; the upper part of the cathode chamber and the anode chamber are respectively provided with a cathode chamber liquid outlet and an anode chamber liquid outlet, and the lower part of the cathode chamber and the anode chamber are respectively provided with a cathode chamber liquid inlet and an anode chamber liquid inlet;

[0026] The bottom liquid outlet of the high tank, the overflow tank, the circulating tank, the liquid inlet of the high tank are connected in sequence; the bottom liquid outlet of the overflow tank is connected with the liquid inlet of the anode chamber of the electrolytic cell, and the brine tank is connected with the liquid inlet of the cathode chamber of the electrolytic cell; the liquid outlet of the cathode chamber of the electrolytic cell is connected with the ultrasonic washing tank of the filter press in sequence; the liquid outlet of the anode chamber of the electrolytic cell is connected with the solution inlet at the top of the residual liquid tank through a pipeline; the solution outlet of the residual liquid tank is connected with the solution inlet of the residual liquid barrel, and the gas outlet of the residual liquid tank is connected with the lye tank; the carbon dioxide cylinder is connected with the gas inlet of the cathode chamber of the electrolytic cell through a gas pipeline.

[0027] The overflow tank is used to ensure the stable flow rate of the rare earth chloride solution pumped into the anode chamber of the electrolytic cell, and the circulating tank is used to recycle the outflow of the overflow tank into the high tank.

[0028] The carbon dioxide utilization efficiency is calculated according to the following formula:

[0029] Carbon dioxide utilization efficiency (%) = actual carbon dioxide consumption (mL) in unit time / carbon dioxide input (mL) in unit time

[0030] The energy consumption is calculated according to the following formula:

[0031] The energy consumption per kilogram of rare earth compound electrolysis is calculated according to the following formula:

[0032] Unit energy consumption (kWh / kg) = voltage (V) * current (A) * time (h) / output (kg) in unit time

[0033] Compared with the prior art, the method provided by the present application has the following beneficial effects:

[0034] (1) In the method provided by the present application, carbon dioxide enters the cathode chamber and reacts with rare earth cations entering the cathode chamber to produce rare earth carbonate, and the rare earth carbonate is in a fluidized state in the cathode chamber under the action of carbon dioxide bubbles, and the mixed solution flows out from the upper liquid outlet of the cathode chamber, thereby improving the preparation efficiency of the rare earth carbonate, reducing the preparation energy consumption, and improving the carbon dioxide gas utilization efficiency to more than 80%.

[0035] (2) In the method provided by the present application, the anode plate and the cation exchange membrane of the anode chamber are tightly attached by a spring net, the distance between the anode plate and the cation exchange membrane is zero, the distance between the cathode plate and the cation exchange membrane is 1mm-10mm, and the energy consumption per kilogram of rare earth carbonate electrolysis is reduced by more than 70%.

[0036] (3) The present application adjusts the concentration of sodium chloride solution and the rare earth chloride not involved in the reaction, and then carries out cyclic electrolysis, thereby improving the reuse efficiency of the rare earth chloride solution.

[0037] (4) The present application reduces the chloride ion content of the rare earth carbonate by providing an ultrasonic washing device in the device, and the chloride ion content of the rare earth carbonate obtained after ultrasonic washing is less than 200ppm. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 A schematic diagram of a device for continuously electro-converting a rare earth chloride solution to prepare a rare earth carbonate.

[0039] 1 - high tank; 2 - brine tank; 3 - overflow tank; 4 - circulating tank; 5 - electrolytic tank; 6 - suction filter; 7 - ultrasonic washing tank; 8 - residual liquid tank; 9 - alkali tank; 10 - carbon dioxide gas cylinder; 11 - residual liquid barrel. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0041] A device for continuously electro-converting a rare earth chloride solution to prepare a rare earth carbonate used in the following examples is shown in Figure 1 .

[0042] Example 1

[0043] The device for preparing rare earth carbonate by continuous electro-conversion of rare earth chloride solution comprises a high tank 1, a brine tank 2, an overflow tank 3, a circulating tank 4, an electrolytic tank 5, a suction filter 6, an ultrasonic washing tank 7, a residual liquid tank 8, a lye tank 9, a carbon dioxide gas cylinder 10 and a residual liquid barrel 11. The electrolytic tank 5 comprises a cathode chamber and an anode chamber. The bottom of the cathode chamber is provided with a cathode chamber air inlet. The upper part of the cathode chamber and the anode chamber is respectively provided with a cathode chamber liquid outlet and an anode chamber liquid outlet, and the lower part is respectively provided with a cathode chamber liquid inlet and an anode chamber liquid inlet. The anode chamber of the electrolytic tank 5 is provided with an anode plate and a cation exchange membrane, and the cathode chamber is provided with a cathode plate. The anode plate and the cathode plate adopt an asymmetric structure, the distance between the anode plate and the cation exchange membrane is 0, and the distance between the cathode plate and the cation exchange membrane is 1mm-10mm. The high tank 1 is provided with a solution inlet and a solution outlet. The solution outlet is located at the bottom of the high tank 1 and is connected with the top liquid inlet of the overflow tank 3 by a pipeline. The solution inlet is located at the upper part of the high tank 1 and is connected with the upper solution inlet of the circulating tank 4. The upper solution outlet of the overflow tank 3 is connected with the liquid inlet of the circulating tank 4, and the bottom solution outlet of the overflow tank 3 is connected with the liquid inlet of the anode chamber of the electrolytic tank 5. The speed of the solution entering the anode chamber of the electrolytic tank 5 is controlled by a flowmeter. The brine tank 2 is provided with a solution inlet and a solution outlet. The solution outlet of the brine tank 2 is located at the bottom of the brine tank 2 and is connected with the liquid inlet of the cathode chamber of the electrolytic tank 5. The speed of the solution entering the cathode chamber of the electrolytic tank 5 is controlled by a flowmeter. The cathode chamber liquid outlet of the electrolytic tank 5 is connected with the solution inlet of the suction filter 6 by a pipeline. The anode chamber liquid outlet of the electrolytic tank 5 is connected with the top solution inlet of the residual liquid tank 8 by a pipeline. The suction filter 6 is provided with a solid outlet. The produced solid product is sent into the ultrasonic washing tank 7. After ultrasonic washing, high-purity rare earth carbonate is obtained. The solution outlet of the residual liquid tank 8 is connected with the solution inlet of the residual liquid barrel. The residual liquid tank 8 is provided with a gas outlet and is connected with the lye tank 9. The carbon dioxide gas cylinder is connected with the bottom gas inlet of the cathode chamber 5 of the electrolytic tank by a gas pipeline. The overflow tank 3 ensures the stable flow rate of the rare earth chloride solution pumped into the anode chamber of the electrolytic tank. The circulating tank 4 recovers the overflow liquid of the overflow tank 3 into the high tank 1.

[0044] Example 2

[0045] A method for continuously preparing rare earth carbonate by using an asymmetric electrolytic tank is realized based on the device in Example 1. In this embodiment, the distance between the anode plate and the cation exchange membrane is 0, and the distance between the cathode plate and the cation exchange membrane is 10mm. The method is carried out according to the following steps:

[0046] Step 1: 350g / L rare earth chloride solution in the high tank is flowed into the anode chamber through the bottom solution outlet of the high tank, the bottom outlet of the overflow tank and the liquid inlet of the anode chamber at a rate of 0.5L / h, and 250g / L sodium chloride solution in the brine tank is continuously flowed into the cathode chamber through the liquid inlet of the cathode chamber at a rate of 0.5L / h.

[0047] Step 2: Carbon dioxide gas is introduced into the electrolytic cell at a rate of 100 mL / min, the solution in the cathode chamber is fluidized, and the carbon dioxide utilization rate is 90%;

[0048] Step 3: Adjust the current density of the electrolytic cell to 1000 A / m 2 , and perform continuous carbonation electrolysis. The solid product and H2 are generated in the cathode chamber of the electrolytic cell, the volume fraction of hydrogen in the generated gas is 90%, Cl2 is generated in the anode chamber of the electrolytic cell, and the energy consumption of the rare earth carbonate electrolytic cell per unit of carbon per unit of time is 2.07 kW·h;

[0049] Step 4: After the solid product is filtered by the suction filter from the cathode chamber outlet with sodium chloride solution, the solid product enters the ultrasonic washing tank, the sodium chloride solution that does not participate in the reaction returns to the electrolytic cell for recycling, and H2 and unreacted carbon dioxide are recovered;

[0050] Step 5: The 250g / L rare earth chloride solution that does not participate in the reaction in the anode chamber of the electrolytic cell flows into the residual liquid tank at a rate of 0.5L / h from the anode outlet, and the liquid flows into the residual liquid tank through the residual liquid tank. After adjusting the mass fraction of the solution to 350g / L, it enters the circulating tank to start circulation, and Cl2 enters the lye tank through the residual liquid tank for neutralization treatment.

[0051] Step 6: The solid product entering the ultrasonic washing tank is ultrasonically washed under the following conditions: ultrasonic washing time is 60 min, ultrasonic power is 600W, cleaning temperature is 40℃, and solid-liquid ratio of cleaning liquid is 100:1. The rare earth carbonate is obtained, the chloride ion content in the rare earth carbonate is 80ppm, and the purity of the rare earth carbonate is 99.98%.

[0052] Example 3

[0053] A method for continuously preparing rare earth carbonate using an asymmetric electrolytic cell is realized based on the device described in Example 1. In this embodiment, the distance between the anode plate and the cation exchange membrane is 0, and the distance between the cathode plate and the cation exchange membrane is 5mm. The method is carried out in the following steps:

[0054] Step 1: The 200g / L rare earth chloride solution in the head tank flows into the anode chamber through the overflow tank bottom outlet from the anode chamber inlet at a rate of 5L / h, and the 200g / L sodium chloride solution in the brine tank continuously enters the cathode chamber at a rate of 5L / h from the cathode chamber inlet.

[0055] Step 2: Carbon dioxide gas is introduced into the electrolytic cell at a rate of 200 mL / min, the solution in the cathode chamber is fluidized, and the carbon dioxide utilization rate is 80%;

[0056] Step 3: Adjust the current density of the electrolytic cell to 600 A / m 2, the electrolytic cell cathode chamber generates solid product and H2, the volume fraction of hydrogen in the generated gas is 80%, the electrolytic cell anode chamber generates Cl2, and the energy consumption of the rare earth carbonate electrolytic cell per unit of time per unit of output is 1.76 kW·h;

[0057] Step 4: After the solid product is filtered by the filter with the sodium chloride solution from the cathode chamber outlet, the solid product enters the ultrasonic washing tank, the sodium chloride solution not involved in the reaction returns to the electrolytic cell for circulation, and H2 and unreacted carbon dioxide are recovered;

[0058] Step 5: The 180g / L rare earth chloride solution not involved in the reaction flows into the residual liquid tank at 5L / h from the anode outlet, flows into the residual liquid tank, and then flows into the circulating tank after adjusting the mass fraction to 200g / L, and Cl2 enters the alkali tank for neutralization treatment.

[0059] Step 6: The solid product entering the ultrasonic washing tank is ultrasonically washed, and the washing conditions are: ultrasonic washing time is 90min, ultrasonic power is 350W, cleaning temperature is 60℃, and solid-liquid ratio of cleaning liquid is 150:1, to obtain rare earth carbonate, the content of chloride ion in the rare earth carbonate is 120ppm, and the purity of the rare earth carbonate is 99.96%.

[0060] Example 4

[0061] A method for continuously preparing rare earth carbonate by using an asymmetric electrolytic cell, which is realized based on the device described in Example 1, in this embodiment, the distance between the anode plate and the cation exchange membrane is 0, and the distance between the cathode plate and the cation exchange membrane is 8mm, and the method is carried out according to the following steps:

[0062] Step 1: The 50g / L rare earth chloride solution in the high tank flows into the anode chamber through the overflow tank bottom outlet and the anode chamber inlet at 10L / h, and the 20g / L sodium chloride solution in the brine tank continuously enters the cathode chamber at 10L / h through the cathode chamber inlet.

[0063] Step 2: Carbon dioxide gas is introduced into the electrolytic cell, the carbon dioxide introduction rate is 100mL / min, the solution in the cathode chamber is in a fluidized state, and the carbon dioxide utilization rate is 80%;

[0064] Step 3: Adjust the current density of the electrolytic cell to 800A / m 2 , carry out continuous carbonation electrolysis, the electrolytic cell cathode chamber generates solid product and H2, the volume fraction of hydrogen in the generated gas is 95%, the electrolytic cell anode chamber generates Cl2, and the energy consumption of the rare earth carbonate electrolytic cell per unit of time per unit of output is 2.05KW·h;

[0065] Step 4: The solid product is filtered by the filter machine from the cathode chamber outlet with sodium chloride solution, and the solid product enters the ultrasonic washing tank. The sodium chloride solution not involved in the reaction returns to the electrolytic tank for recycling, and H2 and unreacted carbon dioxide are recovered.

[0066] Step 5: The 20 g / L rare earth chloride solution not involved in the reaction in the anode chamber of the electrolytic tank flows into the residual liquid tank at 10 L / h from the anode outlet, and the liquid flows into the residual liquid tank through the residual liquid tank. After adjusting the mass fraction of the solution to 50 g / L, it enters the circulating tank to start circulation. Cl2 enters the lye tank through the residual liquid tank for neutralization treatment.

[0067] Step 6: The solid product entering the ultrasonic washing tank is ultrasonically washed, and the washing conditions are: ultrasonic washing time is 120 min, ultrasonic power is 100 W, cleaning temperature is 20℃, and solid-liquid ratio of cleaning liquid is 120:1. The rare earth carbonate is obtained, the chloride ion content in the rare earth carbonate is 180 ppm, and the purity of the rare earth carbonate is 99.92%.

[0068] Example 5

[0069] A method for continuously preparing rare earth carbonate by using an asymmetric electrolytic tank is realized based on the device described in Example 1. In this embodiment, the distance between the anode plate and the cation exchange membrane is 0, and the distance between the cathode plate and the cation exchange membrane is 3 mm. The method is carried out in the following steps:

[0070] Step 1: The 350 g / L rare earth chloride solution in the head tank flows into the anode chamber at 0.5 L / h from the bottom outlet of the overflow tank through the anode chamber inlet, and the 250 g / L sodium chloride solution in the brine tank continuously enters the cathode chamber at 0.5 L / h from the cathode chamber inlet.

[0071] Step 2: Carbon dioxide gas is introduced into the electrolytic tank at a rate of 50 mL / min, and the solution in the cathode chamber is in a fluidized state. The utilization rate of carbon dioxide is 85%.

[0072] Step 3: Adjust the current density of the electrolytic tank to 1000 A / m 2 , and carry out continuous carbonation electrolysis. The solid product and H2 are generated in the cathode chamber of the electrolytic tank, the hydrogen volume fraction in the generated gas is 85%, and the energy consumption of the electrolytic tank per unit production of rare earth carbonate per unit time is 1.86 kW·h;

[0073] Step 4: The solid product is filtered by the filter machine from the cathode chamber outlet with sodium chloride solution, and the solid product enters the ultrasonic washing tank. The sodium chloride solution not involved in the reaction returns to the electrolytic tank for recycling, and H2 and unreacted carbon dioxide are recovered.

[0074] Step 5: 300 g / L of the rare earth chloride solution which is not involved in the reaction in the anode chamber of the electrolytic cell flows into the residual tank at a rate of 0.5 L / h from the anode outlet, and then flows into the residual tank through the liquid flow in the residual tank, and then enters the circulating tank after the mass fraction of the solution is adjusted to 350 g / L to start circulation, and Cl2 enters the lye tank through the residual tank to perform neutralization treatment.

[0075] Step 6: The solid product entering the ultrasonic washing tank is ultrasonically washed, and the washing conditions are as follows: the ultrasonic washing time is 10 min, the ultrasonic power is 1000 W, the cleaning temperature is 90°C, and the solid-liquid ratio of the cleaning solution is 200:1, to obtain rare earth carbonate, the chloride ion content in the rare earth carbonate is 80 ppm, and the purity of the rare earth carbonate is 99.98%.

[0076] Comparative Example 1

[0077] The comparative example is the same as Example 5, except that no ultrasonic washing device is added, and the chloride ion content in the obtained rare earth carbonate is 3000 ppm.

[0078] Comparative Example 2

[0079] The comparative example is the same as Example 5, except that the carbon dioxide is not fluidized by being introduced into the cathode chamber, and the carbon dioxide utilization rate is 8.7%, and the volume fraction of hydrogen in the gas obtained in the cathode chamber is 20%.

[0080] Comparative Example 3

[0081] The comparative example is the same as Example 5, except that the distance between the anode plate and the cation exchange membrane is 20 mm, the distance between the cathode plate and the cation exchange membrane is 20 mm, and the energy consumption of the rare earth carbonate electrolytic cell per unit production per unit time is 7 kW·h.

Claims

1. A method for continuous production of rare earth carbonate in an asymmetric electrolytic cell, characterized in that, The method comprises the following steps: Step 1: the rare earth chloride solution flows into the anode chamber of the electrolytic cell through the overflow tank, and the sodium chloride solution continuously enters the cathode chamber of the electrolytic cell; Step 2: carbon dioxide is introduced into the cathode chamber of the electrolytic cell to make the solution in the cathode chamber of the electrolytic cell be fluidized; Step 3: the current of the electrolytic cell is adjusted to perform continuous carbonization electrolysis, the solid product and hydrogen are generated in the cathode chamber of the electrolytic cell, and chlorine is generated in the anode chamber of the electrolytic cell; Step 4: the solid product is filtered by the filter press, then the solid product enters the ultrasonic washing tank, the sodium chloride solution not participating in the reaction is returned to the electrolytic cell for recycling, and the hydrogen and the unreacted carbon dioxide are recovered; Step 5: the rare earth chloride solution not participating in the reaction in the anode chamber of the electrolytic cell flows out of the anode chamber of the electrolytic cell, then enters the electrolytic cell again for recycling, and the chlorine is neutralized with the lye; Step 6: the solid product entering the ultrasonic washing tank is ultrasonically washed to obtain the rare earth carbonate. The electrolytic cell is provided with an anode chamber, an anode plate, a cation exchange membrane, a cathode chamber and a cathode plate, wherein the anode plate and the cathode plate adopt an asymmetric structure, the distance between the anode plate and the cation exchange membrane is 0, and the distance between the cathode plate and the cation exchange membrane is 1mm-10mm.

2. The method for continuously preparing rare earth carbonate in an asymmetric electrolytic cell according to claim 1, characterized in that, In step 1, the concentration of the rare earth chloride solution is 50g / L-350g / L, and the concentration of the sodium chloride solution is 20g / L-250g / L.

3. The method for continuously preparing rare earth carbonate in an asymmetric electrolytic cell according to claim 1, characterized in that, In step 2, the introduction rate of the carbon dioxide is 10mL / min-200mL / min.

4. The method for continuously preparing rare earth carbonate in an asymmetric electrolytic cell according to claim 1, characterized in that, In step 3, the current density during electrolysis was 600 A / m 2 ~ 1200 A / m 2 .

5. The method for continuously preparing rare earth carbonate in an asymmetric electrolytic cell according to claim 1, characterized in that, In step 5, the concentration of the unreacted rare earth chloride solution is 30g / L-300g / L.

6. The method for continuously preparing rare earth carbonate in an asymmetric electrolytic cell according to claim 1, characterized in that, In step 6, the ultrasonic washing conditions are as follows: the ultrasonic washing time is 10min-120min, the ultrasonic power is 100W-1000W, the cleaning temperature is 20℃-90℃, and the solid-liquid ratio of the cleaning liquid is (50-200):

1.

7. The method for continuously preparing rare earth carbonate in an asymmetric electrolytic cell according to claim 1, characterized in that, In the method, the flow rates of the rare earth chloride solution and the sodium chloride solution entering or flowing out of the electrolytic cell are both 0.5L / h-10L / h.

8. The method for continuously preparing rare earth carbonate in an asymmetric electrolytic cell according to claim 1, characterized in that, The content of chloride ions in the rare earth carbonate is less than 200ppm, and the purity of the obtained rare earth carbonate is ≥99%.

9. A device for continuous preparation of rare earth carbonate in an asymmetric electrolytic cell for carrying out the method according to any one of claims 1 to 8, characterized in that The system comprises a high tank, a brine tank, an overflow tank, a circulation tank, an electrolytic cell, a filter press, an ultrasonic washing tank, a residual liquid tank, a lye tank, a carbon dioxide cylinder and a residual liquid barrel. The electrolytic cell comprises a cathode chamber and an anode chamber; the bottom of the cathode chamber is provided with a cathode chamber gas inlet; the upper portions of the cathode chamber and the anode chamber are respectively provided with a cathode chamber liquid outlet and an anode chamber liquid outlet, and the lower portions of the cathode chamber and the anode chamber are respectively provided with a cathode chamber liquid inlet and an anode chamber liquid inlet.

10. The apparatus for continuously preparing a rare earth carbonate in an asymmetric electrolytic cell according to claim 9, wherein The bottom liquid outlet of the high tank, the overflow tank, the circulation tank and the liquid inlet of the high tank are sequentially connected; the bottom liquid outlet of the overflow tank is connected with the liquid inlet of the anode chamber of the electrolytic cell, the brine tank is connected with the liquid inlet of the cathode chamber of the electrolytic cell; the cathode chamber liquid outlet of the electrolytic cell is sequentially connected with the ultrasonic washing tank of the filter press; the anode chamber liquid outlet of the electrolytic cell is connected with the top solution inlet of the residual liquid tank through a pipeline; the solution outlet of the residual liquid tank is connected with the solution inlet of the residual liquid barrel, the gas outlet of the residual liquid tank is connected with the lye tank; the carbon dioxide cylinder is connected with the cathode chamber gas inlet of the electrolytic cell through a gas pipeline.

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