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

Abstract

The invention discloses a method and a device for continuously preparing rare earth carbonate through an asymmetric electrolytic cell, and belongs to the technical field of rare earth compound preparation. In the process of preparing the rare earth carbonate through electrolysis, carbon dioxide is introduced into the electrolytic cell for continuous carbonization, the prepared product is subjected to ultrasonic washing, the purity of the obtained rare earth carbonate is larger than or equal to 99%, and the chlorine ion content in the rare earth carbonate is smaller than 200 ppm. By controlling the speed of carbon dioxide entering the electrolytic cell, solid and liquid phases in the cathode chamber of the electrolytic cell are in a fluidized state, and a mixed solution flows out from a liquid outlet in the cathode chamber, so that the preparation efficiency of rare earth carbonate is improved, and the utilization efficiency of carbon dioxide gas is improved to 80% or above; by setting the distance between the cathode plate and the cation exchange membrane in the electrolytic bath, the electrolysis energy consumption of rare earth carbonate per kilogram is reduced by more than 70%. Meanwhile, unreacted rare earth chloride is circularly treated, so that the recycling efficiency of the rare earth chloride solution is greatly improved.

Description

Technical Field

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

[0002] Rare earth compounds are known as "vitamins of industry" due to their unique physical and chemical properties and wide range of applications. They play a vital 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 magnetic materials, luminescent materials, catalysts, optical fiber communications, superconducting materials, glass ceramic additives, medical diagnosis and treatment and other fields. For example, NdFeB permanent magnets are one of the most powerful permanent magnetic materials currently, and are widely used in motors, generators, computer disk drives and other fields; rare earth phosphors are widely used in LED lighting, displays and televisions, etc., improving display and lighting effects. In addition, rare earth compounds also show great potential in the field of environmental protection, such as wastewater treatment, air purification and treatment of radioactive waste. 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 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 subjected to heat preservation reaction with a precipitant, the nano rare earth oxide is obtained after filtering, washing, drying and calcining. The preparation method provided by the invention introduces organic acid radical ions to form organic rare earth complex ions by regulating the preparation of the solution and the feeding method of each raw material, so as to accelerate the nucleation process and regulate the crystal growth process.

[0004] Patent CN117822003A discloses a device for preparing rare earth compounds by continuous electroconversion of rare earth chlorides and its application. Through the design of the continuous electroconversion device, saturated rare earth chloride solution is electroconverted in one step to prepare rare earth hydroxides, oxides or rare earth carbonates. The invention uses rare earth chloride solution as raw material to prepare rare earth compound materials in one step. The whole process realizes the circulation of aqueous solution, no waste liquid discharge, no additional precipitant, eliminates the problem of repeated consumption of acid and alkali and wastewater treatment and discharge from the source, and realizes the short-process preparation of high-quality rare earth compounds and the recycling of raw materials.

[0005] Patent CN107190273A discloses a method for preparing rare earth oxide by electroconversion of rare earth chloride, wherein the method pre-deacidifies the rare earth chloride solution and electrolyzes it, and the hydrochloric acid is returned to the rare earth production system; the pre-deacidified rare earth chloride solution is used as an electrolyte for electrolysis, the temperature is 10°C≤<100°C, the electrolysis voltage is ≥2.2V, and carbon dioxide gas is introduced into the cathode area during the electrolysis process, and stirred to directly obtain rare earth carbonate; in the cathode chamber, the electrolyte and rare earth carbonate flow in a directional manner, and solid-liquid separation is performed through a filtering device to obtain a filtrate and rare earth carbonate, and the filtrate is circulated back to the cathode chamber; the rare earth carbonate is dried and roasted to obtain CO2 gas and rare earth oxide products. The invention utilizes the electrolysis process, has a simple process and low cost, and the hydrochloric acid prepared by recovering the by-products hydrogen and chlorine can be returned to the rare earth production system, and eliminates the pollution of some wastewater such as ammonia nitrogen, and finally obtains a high-purity rare earth oxide product.

[0006] In summary, the above invention uses precipitation method to prepare rare earth products, which is easy to produce ammonia nitrogen and other wastewater pollution; although the use of electrolysis to prepare rare earth oxide products can eliminate the pollution of wastewater such as ammonia nitrogen, it does not take into account the utilization efficiency of carbon dioxide in the preparation process of rare earth carbonate. The utilization efficiency of carbon dioxide is low, which not only increases the consumption of carbon dioxide, but also causes the purity of hydrogen produced by the cathode to be low (less than 40%), making subsequent separation difficult. In addition, the above method does not consider the problem of electrode spacing, which increases the energy consumption of electrolysis. At the same time, the above method does not take into account the problem of chloride ion content of rare earth products, resulting in a decrease in the purity of the obtained rare earth compounds. Summary of the invention

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

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for continuously preparing rare earth carbonate in an asymmetric electrolytic cell comprises 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: introducing carbon dioxide into the cathode chamber of the electrolytic cell to fluidize the solution in the cathode chamber of the electrolytic cell;

[0012] Step 3: Adjust the current of the electrolytic cell to perform continuous carbonization electrolysis, whereby solid products 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: After the solid product is filtered with the sodium chloride solution through a suction filter, the solid product enters an ultrasonic washing tank, and the sodium chloride solution that does not participate in the reaction returns to the electrolytic cell for circulation, and hydrogen and unreacted carbon dioxide are recovered;

[0014] Step 5: The rare earth chloride that has not participated in the reaction in the anode chamber of the electrolytic cell flows out from the cathode chamber of the electrolytic cell and enters the electrolytic cell again for circulation, and the chlorine gas and the alkali solution are neutralized;

[0015] Step 6: The solid product is ultrasonically cleaned in an ultrasonic cleaning tank to obtain rare earth carbonate;

[0016] 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; the distance between the cathode plate and the cation exchange membrane is 1mm-10mm.

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

[0018] In step 2, the rate of introduction of carbon dioxide is 10 mL / min to 200 mL / min;

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

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

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

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

[0023] 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 0.5 L / h to 10 L / h.

[0024] An asymmetric electrolytic cell continuous preparation of rare earth carbonate device, used to implement the above method, comprising a high-level tank, a brine tank, an overflow tank, a circulation tank, an electrolytic cell, a suction filter, an ultrasonic washing tank, a residual liquid tank, an alkali liquid tank, a carbon dioxide gas cylinder and a residual liquid barrel;

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

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

[0027] The overflow tank is used to ensure the stability of the rare earth chloride solution flow rate pumped into the anode chamber of the electrolytic cell, and the circulation tank is used to recover the effluent of the overflow tank to the high-level tank.

[0028] The calculation formula for carbon dioxide utilization efficiency is as follows:

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

[0030] The energy consumption calculation formula is as follows:

[0031] The calculation formula for electrolysis energy consumption per kilogram of rare earth compound is as follows:

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

[0033] Compared with the prior art, the present invention has the following beneficial effects:

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

[0035] (2) In the method provided by the present invention, the electrode plate in the anode chamber and the cation exchange membrane are tightly fitted with a spring mesh, the distance between the anode plate and the cation exchange membrane is zero, and the distance between the electrode plate in the cathode chamber and the cation exchange membrane is 1 mm to 10 mm, thereby reducing the energy consumption per kilogram of rare earth carbonate electrolysis by more than 70%.

[0036] (3) The present invention adjusts the concentrations of the sodium chloride solution and the rare earth chloride that does not participate in the reaction and then performs cyclic electrolysis, thereby improving the reuse efficiency of the rare earth chloride solution.

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

[0038] Figure 1 Schematic diagram of a device for preparing rare earth carbonate by continuous electroconversion of a rare earth chloride solution.

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

[0040] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] The following examples use a device for preparing rare earth carbonate by continuous electroconversion of rare earth chloride solution. Figure 1 .

[0042] Example 1

[0043] A device for preparing rare earth carbonate by continuous electroconversion of rare earth chloride solution comprises a high-level tank 1, a brine tank 2, an overflow tank 3, a circulation tank 4, an electrolytic tank 5, a suction filter 6, an ultrasonic washing tank 7, a residual liquid tank 8, an alkali liquid 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; wherein, a cathode chamber air inlet is provided at the bottom of the cathode chamber; a cathode chamber liquid outlet and an anode chamber liquid outlet are provided at the upper part of the cathode chamber and the anode chamber, respectively, and a cathode chamber liquid inlet and an anode chamber liquid inlet are provided at the lower part; an anode plate and a cation exchange membrane are provided in the anode chamber of the electrolytic tank 5, and a cathode plate is provided in the cathode chamber, the anode plate and the cathode plate adopt an asymmetric structure, and the polar 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 1 mm to 10 mm. The high-level tank 1 is equipped with a solution inlet and outlet, wherein the solution outlet is located at the bottom of the high-level tank 1 and is connected to the top inlet of the overflow tank 3 by a pipeline; the solution inlet is located at the upper part of the high-level tank 1 and is connected to the upper solution inlet of the circulation tank 4; the upper solution outlet of the overflow tank 3 is connected to the inlet of the circulation tank 4, and the bottom solution outlet of the overflow tank 3 is connected to the inlet of the anode chamber of the electrolytic cell 5, and the speed of the solution entering the anode chamber of the electrolytic cell 5 is controlled by a flow meter; the brine tank 2 is equipped with a solution inlet and outlet, wherein the solution outlet of the brine tank 2 is located at the bottom of the brine tank 2 and is connected to the inlet of the cathode chamber of the electrolytic cell 5. The liquid inlet is connected to the liquid outlet, and the speed of the solution entering the cathode chamber of the electrolytic cell 5 is controlled by a flow meter; the liquid outlet of the cathode chamber of the electrolytic cell 5 is connected to the solution inlet of the suction filter 6 through a pipeline; the liquid outlet of the anode chamber of the electrolytic cell 5 is connected to the solution inlet at the top of the residual liquid tank 8 through a pipeline; the suction filter 6 is provided with a solid outlet, and the solid product produced is sent to the ultrasonic washing tank 7, and high-purity rare earth carbonate is obtained after ultrasonic washing; the solution outlet of the residual liquid tank 8 is connected to the solution inlet of the residual liquid barrel, and the residual liquid tank 8 is provided with a gas outlet connected to the alkali liquid tank 9; the carbon dioxide gas cylinder is connected to the gas inlet at the bottom of the cathode chamber 5 of the electrolytic cell through a gas pipeline. The overflow tank 3 ensures the stability of the flow rate of the rare earth chloride solution pumped into the anode chamber of the electrolytic cell, and the function of the circulation tank 4 is to recycle the effluent of the overflow tank 3 to the high-level tank 1.

[0044] Example 2

[0045] A method for continuously preparing rare earth carbonate using an asymmetric electrolytic cell is implemented 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 10 mm. The method is carried out according to the following steps:

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

[0047] Step 2: introducing carbon dioxide gas 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 electrolytic cell current density to 1000A / m 2 , continuous carbonization electrolysis is carried out, solid products and H2 are generated in the cathode chamber of the electrolyzer, the hydrogen gas volume fraction in the produced gas is 90%, Cl2 is generated in the anode chamber of the electrolyzer, and the energy consumption of the rare earth carbonate electrolyzer per unit time and unit output is 2.07kW·h;

[0049] Step 4: The solid product is filtered from the cathode chamber outlet along with the sodium chloride solution by a suction filter, and then enters the ultrasonic washing tank. The sodium chloride solution that does not participate in the reaction returns to the electrolytic cell for circulation, 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 from the anode outlet at a rate of 0.5L / h, and the liquid flows into the residual liquid barrel through the residual liquid tank. After the mass fraction of the solution is adjusted to 350g / L, it enters the circulation tank to start circulation. Cl2 enters the alkali solution tank through the residual liquid tank for neutralization treatment.

[0051] Step 6: The solid product enters the ultrasonic washing tank for ultrasonic washing, and the washing conditions are: ultrasonic washing time is 60 minutes, ultrasonic power is 600W, cleaning temperature is 40°C, and cleaning liquid-solid ratio is 100:1, to obtain rare earth carbonate, 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 implemented 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 5 mm. The method is carried out according to the following steps:

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

[0055] Step 2: introducing carbon dioxide gas 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 electrolytic cell current density to 600A / m 2, continuous carbonization electrolysis is carried out, solid products and H2 are generated in the cathode chamber of the electrolyzer, the hydrogen gas volume fraction in the produced gas is 80%, Cl2 is generated in the anode chamber of the electrolyzer, and the energy consumption of the rare earth carbonate electrolyzer per unit time and unit output is 1.76kW·h;

[0057] Step 4: The solid product is filtered from the cathode chamber outlet along with the sodium chloride solution by a suction filter, and then enters the ultrasonic washing tank. The sodium chloride solution that does not participate 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 that does not participate in the reaction in the anode chamber of the electrolytic cell flows into the residual liquid tank from the anode outlet at a rate of 5L / h, and the liquid flows into the residual liquid barrel through the residual liquid tank. After the mass fraction of the solution is adjusted to 200g / L, it enters the circulation tank to start circulation. Cl2 enters the alkali solution tank through the residual liquid tank for neutralization treatment.

[0059] Step 6: The solid product enters the ultrasonic washing tank for ultrasonic washing, and the washing conditions are: ultrasonic washing time is 90 minutes, ultrasonic power is 350W, cleaning temperature is 60°C, and cleaning liquid-solid ratio is 150:1, to obtain rare earth carbonate, the chloride ion content 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 using an asymmetric electrolytic cell is implemented 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 8 mm. The method is carried out according to the following steps:

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

[0063] Step 2: introducing carbon dioxide gas 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 80%;

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

[0065] Step 4: The solid product is filtered from the cathode chamber outlet along with the sodium chloride solution by a suction filter, and then enters the ultrasonic washing tank. The sodium chloride solution that does not participate in the reaction returns to the electrolytic cell for circulation, and H2 and unreacted carbon dioxide are recovered;

[0066] Step 5: The 20g / 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 from the anode outlet at a rate of 10L / h, and the liquid flows into the residual liquid barrel through the residual liquid tank. After the solution mass fraction is adjusted to 50g / L, it enters the circulation tank to start circulation, and Cl2 enters the alkali liquid tank through the residual liquid tank for neutralization treatment.

[0067] Step 6: The solid product enters the ultrasonic washing tank for ultrasonic washing, and the washing conditions are: ultrasonic washing time is 120 minutes, ultrasonic power is 100 W, cleaning temperature is 20° C., and cleaning liquid-solid ratio is 120:1, to obtain rare earth carbonate, 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 using an asymmetric electrolytic cell is implemented 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 according to the following steps:

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

[0071] Step 2: introducing carbon dioxide gas into the electrolytic cell at a rate of 50 mL / min, the solution in the cathode chamber is fluidized, and the carbon dioxide utilization rate is 85%;

[0072] Step 3: Adjust the electrolytic cell current density to 1000A / m 2 , continuous carbonization electrolysis is carried out, solid products and H2 are generated in the cathode chamber of the electrolyzer, the hydrogen gas volume fraction in the produced gas is 85%, Cl2 is generated in the anode chamber of the electrolyzer, and the energy consumption of the rare earth carbonate electrolyzer per unit time and unit output is 1.86kW·h;

[0073] Step 4: The solid product is filtered from the cathode chamber outlet along with the sodium chloride solution by a suction filter, and then enters the ultrasonic washing tank. The sodium chloride solution that does not participate in the reaction returns to the electrolytic cell for circulation, and H2 and unreacted carbon dioxide are recovered;

[0074] Step 5: The 300g / 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 from the anode outlet at a rate of 0.5L / h, and the liquid flows into the residual liquid barrel through the residual liquid tank. After the mass fraction of the solution is adjusted to 350g / L, it enters the circulation tank to start circulation. Cl2 enters the alkali liquid tank through the residual liquid tank for neutralization treatment.

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

[0076] Comparison 1

[0077] This 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] Comparison 2

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

[0080] Contrast 3

[0081] This 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 electrolyzer per unit time and unit output is 7 kW·h.

Claims

1. A method for continuously preparing rare earth carbonate in an asymmetric electrolytic cell, characterized in that: The following steps are involved: 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: introducing carbon dioxide into the cathode chamber of the electrolytic cell to fluidize the solution in the cathode chamber of the electrolytic cell; Step 3: Adjust the current of the electrolytic cell to perform continuous carbonization electrolysis, whereby solid products 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: After the solid product is filtered with the sodium chloride solution through a suction filter, the solid product enters an ultrasonic washing tank, and the sodium chloride solution that does not participate in the reaction returns to the electrolytic cell for circulation, and hydrogen and unreacted carbon dioxide are recovered; Step 5: The rare earth chloride that has not participated in the reaction in the anode chamber of the electrolytic cell flows out from the cathode chamber of the electrolytic cell and enters the electrolytic cell again for circulation, and the chlorine gas and the alkali solution are neutralized; Step 6: The solid product is ultrasonically cleaned in an ultrasonic cleaning tank to obtain 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; 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 rare earth chloride is 50 g / L to 350 g / L, and the concentration of sodium chloride solution is 20 g / L to 250 g / 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 rate of introduction of carbon dioxide is 10 mL / min to 200 mL / 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 is 600A / m 2 ~1200A / 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 30 g / L to 300 g / 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: ultrasonic washing time is 10 min to 120 min, ultrasonic power is 100 W to 1000 W, cleaning temperature is 20° C. to 90° C., and cleaning liquid-solid ratio is (50 to 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 0.5 L / h to 10 L / h.

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

9. An asymmetric electrolytic cell continuous preparation of rare earth carbonate device, used to implement the method according to any one of claims 1 to 8, characterized in that: Including high-level tank, brine tank, overflow tank, circulation tank, electrolytic tank, filter, ultrasonic washing tank, residual liquid tank, alkali liquid tank, carbon dioxide gas cylinder and residual liquid barrel; The electrolytic cell comprises a cathode chamber and an anode chamber; wherein a cathode chamber air inlet is arranged at the bottom of the cathode chamber; a cathode chamber liquid outlet and an anode chamber liquid outlet are arranged at the upper part of the cathode chamber and the anode chamber, respectively, and a cathode chamber liquid inlet and an anode chamber liquid inlet are arranged at the lower part.

10. The device for continuously preparing rare earth carbonate in an asymmetric electrolytic cell according to claim 9, characterized in that: The bottom liquid outlet of the high-level tank, the overflow tank, the circulation tank, and the liquid inlet of the high-level tank are connected in sequence; the bottom liquid outlet of the overflow tank is connected to the liquid inlet of the anode chamber of the electrolytic cell, and the brine tank is connected to the liquid inlet of the cathode chamber of the electrolytic cell; the liquid outlet of the cathode chamber of the electrolytic cell is connected to the ultrasonic washing tank of the suction filter in sequence; the liquid outlet of the anode chamber of the electrolytic cell is connected to the solution inlet at the top of the residual liquid tank through a pipeline; the solution outlet of the residual liquid tank is connected to the solution inlet of the residual liquid barrel, and the gas outlet of the residual liquid tank is connected to the alkali solution tank; the carbon dioxide gas cylinder is connected to the gas inlet of the cathode chamber of the electrolytic cell through a gas pipeline.

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