Method and device for treating carbonate brine based on bipolar membrane electrodialysis

Abstract

The invention discloses a bipolar membrane electrodialysis-based carbonate brine treatment method and device, carbonate brine is added into a prepared low-concentration sodium metaaluminate solution through a chemical precipitation tank for precipitation reaction, suspended solids are removed through a filter, organic matters are removed through an activated carbon adsorption tower, and finally a refined solution is obtained through an ion exchange system; the refined liquid is introduced into a treatment device salt chamber, the voltage is controlled to be 1.5-2.5 V / membrane pair, and circular treatment is performed; deionized water is supplemented to the alkali chamber and the acid chamber respectively, high-purity NaOH is obtained in the alkali chamber, and high-purity carbon dioxide is obtained in the acid chamber. According to the present invention, the efficient separation treatment of the carbonate brine is achieved, the impurities can be effectively removed, the high-purity NaOH and the high-purity carbon dioxide are obtained, the treatment energy consumption is low, the cost is controllable, and the high-value resource utilization of the carbonate brine is achieved.

Description

Technical Field

[0001] This invention relates to the field of chemical high-salt wastewater treatment, and in particular to a method and apparatus for treating carbonate brine based on bipolar membrane electrodialysis. Background Technology

[0002] Traditional methods for preparing sodium hydroxide (such as in the chlor-alkali industry) and carbon dioxide capture / conversion processes often suffer from high energy consumption, associated byproducts (such as chlorine), complex processes, or secondary pollution. The process of converting carbonate brine (sodium carbonate or sodium bicarbonate) into sodium hydroxide and carbon dioxide addresses this issue. Many industrial processes, such as certain chemical production, flue gas scrubbing, or processing in specific chemical fields, generate brine or wastewater rich in sodium carbonate and sodium bicarbonate. Resource recovery from this saline wastewater, converting it into high-value sodium hydroxide and recyclable high-purity carbon dioxide, offers low-carbon and circular economy benefits.

[0003] Bipolar membrane electrodialysis technology can dissociate water molecules into H+ at the interface layer of a bipolar membrane under the action of a DC electric field. + and OH - This technology allows for the direct conversion of salt solutions into corresponding acids and bases without introducing new chemical substances. It offers advantages such as relatively low energy consumption, a clean and pollution-free process, compact equipment, and controllable product concentration. Studies have shown that compared to processing salts such as sodium sulfate, using sodium carbonate as a raw material to produce sodium hydroxide can yield high-purity alkaline solutions under similar conditions. Furthermore, in the acid chamber of a bipolar membrane electrodialysis system with high current efficiency, H... + With carbonate (CO3) 2- The combination of these substances will produce carbonic acid (H2CO3), which is unstable and easily decomposes to produce high-purity carbon dioxide gas. Bipolar membrane electrodialysis systems require high purity feed solutions, ensuring the effective removal of divalent and higher-valence metal ions such as calcium and magnesium to prevent contaminants from forming hydroxide precipitates in the alkali chamber, causing blockage and contamination of the membrane surface.

[0004] Bipolar membrane electrodialysis (BMED), as a novel membrane separation technology, can achieve directional migration of anions and cations through electric field drive, and simultaneously complete salt decomposition (common applications such as Na2SO4→H2SO4+NaOH) and acid and alkali recovery in a single device. It features low energy consumption, high efficiency, no phase change, and environmental friendliness, meeting the needs of green chemical industry and circular economy.

[0005] Bipolar membrane electrodialysis (BMED) is a membrane separation technology based on the principle of electrodialysis, which uses a bipolar membrane to dissociate water molecules into hydrogen ions (H+). + ) and hydroxide ions (OH) -This process involves separating and converting salt solutions by obtaining acids and bases. This technology offers advantages such as low energy consumption, ease of operation, and environmental friendliness, and has significant advantages in treating saline wastewater and recovering useful substances. However, bipolar membrane electrodialysis technology currently suffers from problems including high equipment costs, membrane fouling and short lifespan, high energy consumption, low product concentration, and the need for complex wastewater pretreatment. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a method and apparatus for treating carbonate brine based on bipolar membrane electrodialysis.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by this invention is as follows: In a first aspect, the present invention provides a method for treating carbonate brine based on bipolar membrane electrodialysis, comprising: The carbonate brine is transported to a chemical precipitation tank, where a low-concentration sodium aluminate solution is added to carry out a precipitation reaction to remove calcium and magnesium ions, resulting in refined liquid A. The purified liquid A is fed to a filter to remove suspended solids, yielding the primary filtrate; The primary filtrate is fed to an activated carbon adsorption tower to remove organic matter and obtain purified liquid; The purified solution is transported to an ion exchange system and purified by using a series of Na-type cation exchange resins to obtain purified solution B. The purified solution B is continuously fed into the salt chamber of the bipolar membrane electrodialysis device. The DC power supply is turned on and the voltage is controlled at 1.5V / membrane pair to 2.5V / membrane pair. The solution in the salt chamber is then circulated back to 30℃~45℃ after being controlled by a plate heat exchanger. Deionized water is added to the acid chamber of the bipolar membrane electrodialysis device to circulate the solution in the acid chamber and recover the carbon dioxide gas generated in the acid chamber. Deionized water is added to the alkali chamber of the bipolar membrane electrodialysis device, and the solution in the alkali chamber is circulated back after being controlled to 30℃~45℃ by a plate heat exchanger. When the NaOH solution concentration reaches 5% to 15%, part of the NaOH solution is diverted to the alkali storage tank to obtain NaOH solution.

[0008] In some embodiments, the purified solution B is continuously fed into the salt chamber of a bipolar membrane electrodialysis apparatus, and then the process further includes: The diluted brine, whose concentration has decreased in the salt chamber, is continuously circulated back to the salt chamber and mixed with the continuously transported refined solution B for cyclic electrolysis.

[0009] In some embodiments, the purified solution is fed to an ion exchange system to obtain purified solution B, and then the process further includes: The purified liquid B is sent to the ultrafiltration system, where a microporous filter with a filtration accuracy of not less than 0.5 μm is used to remove colloidal substances, thus obtaining the ultrafiltration purified liquid. The ultrafiltration purified solution is delivered to the salt chamber of the bipolar membrane electrodialysis unit.

[0010] In some embodiments, conveying the primary filtrate to an activated carbon adsorption tower includes: The primary filtrate is conveyed to an adsorption tower filled with activated carbon at an empty tower flow rate of 0.2 m / h to 1.2 m / h. The activated carbon is coconut shell-based granular carbon with a particle size of 1.0 mm to 3.0 mm and an iodine value of ≥800 mg / g.

[0011] In some embodiments, the activated carbon adsorption tower is operated in series with two towers to control the total organic carbon value of the final effluent to be <3 mg / L.

[0012] In some embodiments, replenishing the acid chamber of the bipolar membrane electrodialysis device with deionized water to circulate the solution within the acid chamber includes: The acid chamber circulating liquid is passed through a PP filter or bag filter with a filtration accuracy of not less than 5μm~10μm before returning to the acid chamber, and the acid chamber circulating current density is controlled at 400A / m²~1000A / m².

[0013] In some embodiments, replenishing the alkali chamber of the bipolar membrane electrodialysis device with deionized water to circulate the solution within the alkali chamber includes: The circulating current density in the alkali chamber is controlled to be 400A / m²~1000A / m².

[0014] In some embodiments, the method further includes chemical cleaning of the bipolar membrane electrodialysis apparatus, including: A 2% to 4% HCl solution was fed into the device and circulated for 12 hours for cleaning. Pure water is fed into the device and circulated for 12 hours for cleaning. A 2%–4% NaOH solution was fed into the device and circulated for 12 hours for cleaning. Pure water is then pumped back into the device for 12 hours of continuous cleaning.

[0015] In a second aspect, the present invention provides a treatment apparatus for carbonate brine based on bipolar membrane electrodialysis, applicable to the method described in the first aspect. The apparatus includes a salt chamber, an alkali chamber, an acid chamber, a bipolar membrane stack, a first circulation pipeline, a second circulation pipeline, and a third circulation pipeline. The salt chamber is used to hold and circulate the purified solution B. The alkali chamber is used to hold and circulate NaOH solution and is connected to an alkali storage tank. The acid chamber is used to generate and recover carbon dioxide gas. The bipolar membrane stack includes at least two bipolar membrane chambers connected in series, each of which has an inlet and an outlet connected to the salt chamber, the alkali chamber, and the acid chamber. The first circulation pipeline connects the outlet of the salt chamber to the inlet of the bipolar membrane stack. A first plate heat exchanger, a first pump body, and a first filter are sequentially arranged along the flow direction on the first circulation pipeline. The second circulation pipeline connects the outlet of the alkali chamber to the inlet of the bipolar membrane stack. A second plate heat exchanger, a second pump body, and a second filter are sequentially arranged along the flow direction on the second circulation pipeline. The third circulation pipeline connects the outlet of the acid chamber to the inlet of the acid chamber of the bipolar membrane stack. A third pump body and a third filter are sequentially arranged along the flow direction on the third circulation pipeline.

[0016] In some embodiments, the first filter, the second filter, and the third filter are precision filters, and the third filter is a PP filter or a bag filter with a filtration accuracy of not less than 5μm to 10μm.

[0017] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art: Unlike existing technologies, the above technical solution involves feeding carbonate brine into a chemical precipitation tank, adding a low-concentration sodium aluminate solution for precipitation to remove calcium and magnesium ions, yielding purified solution A; purified solution A is then fed into a filter to remove suspended solids, yielding primary filtrate; the primary filtrate is then fed into an activated carbon adsorption tower to remove organic matter, yielding purified solution; the purified solution is then fed into an ion exchange system, where it is further purified using a series of Na-type cation exchange resins, yielding purified solution B; purified solution B is continuously fed into the salt chamber of a bipolar membrane electrodialysis unit, and the DC power supply is activated and controlled... The voltage is controlled at 1.5V / membrane pair to 2.5V / membrane pair, allowing the solution in the salt chamber to be circulated back after being heated to 30℃~45℃ via a plate heat exchanger. Deionized water is added to the acid chamber of the bipolar membrane electrodialysis unit, allowing the solution to circulate back and recovering the carbon dioxide gas generated in the acid chamber. Similarly, deionized water is added to the alkali chamber of the bipolar membrane electrodialysis unit, allowing the solution to circulate back after being heated to 30℃~45℃ via a plate heat exchanger. When the NaOH solution concentration reaches 5% to 15%, a portion of the NaOH solution is diverted to the alkali storage tank to obtain NaOH solution. This achieves highly efficient treatment of carbonate brine, effectively removing impurities, improving the purity of sodium hydroxide and carbon dioxide products, reducing energy consumption, and realizing the resource utilization of wastewater. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the processing device described in the specific embodiment.

[0020] The attached figures are labeled as follows: 1. Salt chamber; 2. Bipolar membrane stack; 3. First circulation pipeline; 31. First heat exchanger; 32. First pump body; 33. First filter; 4. Second circulation pipeline; 41. Second heat exchanger; 42. Second pump body; 43. Second filter; 5. Third circulation pipeline; 51. The third pump body; 52. Third filter; 6. Alkali chamber; 7. Acid chamber. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the invention. Similarly, the following embodiments are only some, not all, embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] In a first aspect, this embodiment provides a method for treating carbonate brine based on bipolar membrane electrodialysis, comprising: The carbonate brine is transported to a chemical precipitation tank, where a low-concentration sodium aluminate solution is added to carry out a precipitation reaction to remove calcium and magnesium ions, resulting in refined liquid A. The purified liquid A is fed to a filter to remove suspended solids, yielding the primary filtrate; The primary filtrate is fed to an activated carbon adsorption tower to remove organic matter and obtain purified liquid; The purified solution is transported to an ion exchange system and purified by using a series of Na-type cation exchange resins to obtain purified solution B. The purified solution B is continuously fed into the salt chamber of the bipolar membrane electrodialysis device. The DC power supply is turned on and the voltage is controlled at 1.5V / membrane pair to 2.5V / membrane pair. The solution in the salt chamber is then circulated back to 30℃~45℃ after being controlled by a plate heat exchanger. Deionized water is added to the acid chamber of the bipolar membrane electrodialysis device to circulate the solution in the acid chamber and recover the carbon dioxide gas generated in the acid chamber. Deionized water is added to the alkali chamber of the bipolar membrane electrodialysis device, and the solution in the alkali chamber is circulated back after being controlled to 30℃~45℃ by a plate heat exchanger. When the NaOH solution concentration reaches 5% to 15%, part of the NaOH solution is diverted to the alkali storage tank to obtain NaOH solution.

[0023] Please see Figure 1 In a second aspect, this embodiment provides a treatment apparatus for carbonate brine based on bipolar membrane electrodialysis, applicable to the method described in the first aspect. The apparatus includes a salt chamber, an alkali chamber, an acid chamber, a bipolar membrane stack, a first circulation pipeline, a second circulation pipeline, and a third circulation pipeline. The salt chamber is used to hold and circulate the purified liquid B. The alkali chamber is used to hold and circulate NaOH solution and is connected to an alkali storage tank. The acid chamber is used to generate and recover carbon dioxide gas. The bipolar membrane stack includes at least two bipolar membrane chambers connected in series, each of which has an inlet and an outlet connected to the salt chamber, alkali chamber, and acid chamber. The first circulation pipeline connects the outlet of the salt chamber to the inlet of the bipolar membrane stack. A first plate heat exchanger, a first pump body, and a first filter are sequentially arranged along the flow direction on the first circulation pipeline. The second circulation pipeline connects the outlet of the alkali chamber to the inlet of the bipolar membrane stack. A second plate heat exchanger, a second pump body, and a second filter are sequentially arranged along the flow direction on the second circulation pipeline. The third circulation pipeline connects the outlet of the acid chamber to the inlet of the acid chamber of the bipolar membrane stack. A third pump body and a third filter are sequentially arranged along the flow direction on the third circulation pipeline.

[0024] In some embodiments, the first filter, the second filter, and the third filter are precision filters, and the third filter is a PP filter or a bag filter with a filtration accuracy of not less than 5μm to 10μm.

[0025] In this embodiment, the purified solution B is continuously fed into the salt chamber of the bipolar membrane electrodialysis device. The solution in the salt chamber is heated to 30°C~45°C via a plate heat exchanger and then returned to the bipolar membrane stack via a first pump and a first filter, forming a reflux cycle. Deionized water is added to the acid chamber, and the solution in the acid chamber is filtered by a third filter and then returned to the bipolar membrane stack via a second pump. The carbon dioxide gas generated in the acid chamber is recovered. Deionized water is added to the alkali chamber, and the solution in the alkali chamber is heated to 30°C~45°C via a plate heat exchanger and then returned to the bipolar membrane stack via a third pump. When the NaOH solution concentration reaches 5%~15%, a portion of the NaOH solution is diverted to the alkali storage tank. Through the synergistic pretreatment steps of chemical precipitation, filtration, activated carbon adsorption, and ion exchange, the carbonate brine is purified, effectively removing impurities such as calcium and magnesium ions, suspended solids, organic matter, and other heavy metal ions that affect the performance of the bipolar membrane and ion exchange membrane, significantly extending the membrane's service life.

[0026] This embodiment effectively removes suspended solids and particulate matter from the brine through filtration, providing a clean primary filtrate for subsequent treatment. The addition of a low-concentration sodium aluminate solution to the chemical precipitation tank allows for precise control of reaction conditions, ensuring sufficient precipitation and removal of calcium and magnesium ions. The activated carbon adsorption tower operates stably at an empty tower flow rate of 0.2 m / h to 1.2 m / h, guaranteeing both efficient removal of organic matter and long-term stable operation of the device. The ion exchange system uses a series of Na-type cation exchange resins for purification, obtaining a purified solution B that meets the requirements for electrodialysis feed. Through the synergistic effect of the entire pretreatment system, the purity of the feed solution is significantly improved, creating ideal conditions for the subsequent bipolar membrane electrodialysis process.

[0027] In the core stage of bipolar membrane electrodialysis, by controlling the DC voltage within the range of 1.5V / membrane pair to 2.5V / membrane pair, and using a plate heat exchanger to maintain the solution temperature in the salt and alkali chambers at 30℃~45℃, high ion migration efficiency and bipolar membrane water dissociation efficiency are ensured, while preventing membrane stack damage due to overheating. The acid and alkali chambers employ independent circulation loops. The acid chamber loop is equipped with a filter to ensure liquid cleanliness, while the alkali chamber loop is equipped with a plate heat exchanger to control temperature. This ensures stable system operation while efficiently achieving carbon dioxide gas recovery and continuous production of sodium hydroxide solution. This embodiment, by optimizing the operating parameters and control conditions of each process step, achieves efficient resource utilization of carbonate brine, while ensuring the long-term stable operation and economic efficiency of the entire system.

[0028] In some embodiments, the purified solution B is continuously fed into the salt chamber of a bipolar membrane electrodialysis apparatus, and then the process further includes: The diluted brine, whose concentration has decreased in the salt chamber, is continuously circulated back to the salt chamber and mixed with the continuously transported refined solution B for cyclic electrolysis.

[0029] In this embodiment, by monitoring the concentration change of the carbonate solution in the salt chamber in real time, while continuously supplying the refined solution B, the diluted brine produced during the electrolysis process is also continuously circulated back to the salt chamber, ensuring the continuous and efficient operation of the electrolysis process and realizing the cascade and recycling of materials; the remaining diluted brine continues to participate in the circulating electrolysis, maintaining the relative stability of the salt chamber concentration in the bipolar membrane electrodialysis system, effectively improving the utilization efficiency of raw materials.

[0030] This embodiment precisely controls the electrolysis process and returns the brine to the system for circulation, avoiding material waste and subsequent treatment problems caused by the discharge of brine. At the same time, it ensures the full recovery and utilization of the remaining valuable components in the brine. While maintaining the original treatment effect, it further improves the economy and environmental sustainability of the entire process system, realizing closed-loop treatment of carbonate brine and maximizing the utilization of resource value.

[0031] In some embodiments, the purified solution is fed to an ion exchange system to obtain purified solution B, and then the process further includes: The purified liquid B is sent to the ultrafiltration system, where a microporous filter with a filtration accuracy of not less than 0.5 μm is used to remove colloidal substances, thus obtaining the ultrafiltration purified liquid. The ultrafiltration purified solution is delivered to the salt chamber of the bipolar membrane electrodialysis unit.

[0032] In this embodiment, the purified solution B obtained after purification by the ion exchange system using Na-type cation exchange resins in series is transported to the ultrafiltration system. The purified solution B after ion exchange is further treated by a microporous filter with a filtration accuracy of not less than 0.5 μm. This step can effectively retain trace amounts of colloidal substances and finer suspended particles remaining in the previous process, further improving the purity of the carbonate solution and obtaining a higher quality ultrafiltration purified solution.

[0033] This embodiment fully leverages the respective technological advantages of chemical ion exchange and physical membrane filtration. Through the synergistic treatment of deep removal of ionic impurities by ion exchange resin and precise retention of colloidal substances by ultrafiltration membrane, it achieves deep removal of impurity ions and reliable separation of colloidal substances based on the original purification process. This not only provides a higher purity and more stable ultrafiltration purification solution as feed for the subsequent bipolar membrane electrodialysis process but also lays a solid foundation for further improving the purity of the final sodium hydroxide solution and carbon dioxide gas, meeting higher-end application requirements. Simultaneously, this phased, multi-step purification method optimizes the operating load and efficiency of each processing unit, helping to extend the service life of key components such as bipolar membranes, ion exchange membranes, and ion exchange resins, and reducing the overall operation and maintenance costs of the system. The ultrafiltration purification step can flexibly adjust its operating parameters according to different purity requirements of the final product, providing reliable technical support and process flexibility for preparing higher-quality acid and alkali products.

[0034] In some embodiments, conveying the primary filtrate to an activated carbon adsorption tower includes: The primary filtrate is conveyed to an adsorption tower filled with activated carbon at an empty tower flow rate of 0.2 m / h to 1.2 m / h. The activated carbon is coconut shell-based granular carbon with a particle size of 1.0 mm to 3.0 mm and an iodine value of ≥800 mg / g.

[0035] In some embodiments, the activated carbon adsorption tower is operated in series with two towers to control the total organic carbon value of the final effluent to be <3 mg / L.

[0036] In this embodiment, high-performance coconut shell-based granular activated carbon with a particle size of 1.0mm~3.0mm and an iodine value ≥800mg / g is used as the adsorption medium. Combined with precise empty tower flow rate control of 0.2m / h~1.2m / h, an optimal balance between the adsorption efficiency of organic matter in the primary filtrate and the device's processing throughput is achieved. A dual-tower series operation mode for the activated carbon adsorption towers is adopted. By setting reasonable operating parameters and switching regeneration cycles, and by strictly controlling the total organic carbon (TOC) of the final effluent to ensure its value is consistently below 3mg / L, the reliability and stability of organic matter removal are guaranteed, while fully utilizing the adsorption potential of the activated carbon adsorbent, thereby significantly extending the service life and regeneration frequency of the activated carbon.

[0037] This embodiment, through the synergistic effect of selecting high-quality adsorption materials and optimizing key operating parameters, not only significantly improves the overall removal effect of organic matter by the pretreatment system, but also enhances the stability, operational flexibility, and economy of the adsorption system through the dual-tower series staged adsorption method. It provides high-quality purified liquid with extremely low organic matter content for the subsequent ion exchange system and bipolar membrane electrodialysis device. The entire activated carbon adsorption system is easy to operate and maintain, reliable in operation, and can adapt to the deep removal requirements of organic matter under different influent water quality conditions.

[0038] In some embodiments, replenishing the acid chamber of the bipolar membrane electrodialysis device with deionized water to circulate the solution within the acid chamber includes: The acid chamber circulating liquid is passed through a PP filter or bag filter with a filtration accuracy of not less than 5μm~10μm before returning to the acid chamber, and the acid chamber circulating current density is controlled at 400A / m²~1000A / m².

[0039] In some embodiments, replenishing the alkali chamber of the bipolar membrane electrodialysis device with deionized water to circulate the solution within the alkali chamber includes: The circulating current density in the alkali chamber is controlled to be 400A / m²~1000A / m².

[0040] In this embodiment, during the acid chamber treatment process of the bipolar membrane electrodialysis device, deionized water is added and the solution in the acid chamber is circulated back. This circulating liquid needs to be purified by a PP filter or bag filter with a filtration accuracy of not less than 5μm~10μm before returning to the acid chamber. Simultaneously, the circulating current density in the acid chamber is precisely controlled within the range of 400A / m²~1000A / m² to achieve stable and efficient production of high-purity carbon dioxide gas. During the alkali chamber treatment process, deionized water is added and the solution in the alkali chamber is circulated back. This circulating liquid is precisely temperature-controlled to 30℃~45℃ by a plate heat exchanger before returning to the alkali chamber. Similarly, the circulating current density in the alkali chamber is controlled within the range of 400A / m²~1000A / m². When the NaOH solution concentration in the alkali chamber reaches the target range of 5%~15%, it is diverted and collected, effectively controlling the content of specific impurity ions such as chloride ions in the product to a low level.

[0041] This embodiment achieves efficient purification and concentration of sodium hydroxide solution and stable generation of carbon dioxide gas by precisely controlling the filtration accuracy of the acid chamber circulating liquid and the temperature of the alkali chamber circulating liquid, and synergistically optimizing the circulating current density of the acid and alkali chambers. The synergistic effect of temperature control, precision filtration, and current density optimization significantly improves the operational stability and process efficiency of the bipolar membrane electrodialysis device. While ensuring the quality of sodium hydroxide and carbon dioxide products, it also considers the energy economy of the process, providing key operational parameter guarantees and technical reliability for the long-term, stable, and efficient operation of the electrodialysis process. The entire system has scientifically and rationally set parameters and a clear and simple operation control logic, demonstrating significant technical advantages and application value.

[0042] In some embodiments, the method further includes chemical cleaning of the bipolar membrane electrodialysis apparatus, including: A 2% to 4% HCl solution was fed into the device and circulated for 12 hours for cleaning. Pure water is fed into the device and circulated for 12 hours for cleaning. A 2%–4% NaOH solution was fed into the device and circulated for 12 hours for cleaning. Pure water is then pumped back into the device for 12 hours of continuous cleaning.

[0043] In this embodiment, a periodic chemical cleaning process effectively maintains the long-term operational stability and membrane performance of the bipolar membrane electrodialysis treatment device. Specifically, the treatment device is sequentially cleaned for 12 hours each in each circulation loop using a 2%~4% HCl solution at a preset frequency to effectively dissolve and remove inorganic scale accumulated on the membrane surface and in the flow channels; then, pure water is used to clean each circulation loop for 12 hours to thoroughly rinse away residual acidic substances and dissolved matter; subsequently, a 2%~4% NaOH solution is used to clean each circulation loop for 12 hours to decompose and remove adsorbed organic pollutants on the membrane surface and in the flow channels; finally, pure water is used again to clean each circulation loop for 12 hours to ensure that the membrane stack and pipeline system are thoroughly cleaned and free of chemical cleaning agent residue.

[0044] This embodiment uses alternating cleaning with acidic and alkaline cleaning agents, combined with a pure water rinsing step, to maintain the efficient operation of the bipolar membrane electrodialysis system while effectively removing different types of contaminants from the membrane surface. This forms a complete and effective membrane system maintenance, cleaning, and regeneration process system.

[0045] Unlike existing technologies, the above technical solution involves feeding carbonate brine into a chemical precipitation tank, adding a low-concentration sodium aluminate solution for precipitation to remove calcium and magnesium ions, yielding purified solution A; purified solution A is then fed into a filter to remove suspended solids, yielding primary filtrate; the primary filtrate is then fed into an activated carbon adsorption tower to remove organic matter, yielding purified solution; the purified solution is then fed into an ion exchange system, where it is further purified using a series of Na-type cation exchange resins, yielding purified solution B; purified solution B is continuously fed into the salt chamber of a bipolar membrane electrodialysis unit, and the DC power supply is activated and controlled... The voltage is controlled at 1.5V / membrane pair to 2.5V / membrane pair, allowing the solution in the salt chamber to be circulated back after being heated to 30℃~45℃ via a plate heat exchanger. Deionized water is added to the acid chamber of the bipolar membrane electrodialysis unit, allowing the solution to circulate back and recovering the carbon dioxide gas generated in the acid chamber. Similarly, deionized water is added to the alkali chamber of the bipolar membrane electrodialysis unit, allowing the solution to circulate back after being heated to 30℃~45℃ via a plate heat exchanger. When the NaOH solution concentration reaches 5% to 15%, a portion of the NaOH solution is diverted to the alkali storage tank to obtain NaOH solution. This achieves highly efficient treatment of carbonate brine, effectively removing impurities, improving the purity of sodium hydroxide and carbon dioxide products, reducing energy consumption, and realizing the resource utilization of wastewater.

[0046] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0047] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute all or part of the steps of the methods of various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0048] The above description is only a part of the embodiments of the present invention and does not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made based on the content of the present invention specification and drawings, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for treating carbonate brine based on bipolar membrane electrodialysis, characterized in that, include: The carbonate brine is transported to a chemical precipitation tank, where a low-concentration sodium aluminate solution is added to carry out a precipitation reaction to remove calcium and magnesium ions, resulting in refined liquid A. The purified liquid A is fed to a filter to remove suspended solids, resulting in a primary filtrate. The primary filtrate is then fed to an activated carbon adsorption tower to remove organic matter, resulting in a purified liquid. The purified solution is transported to an ion exchange system and purified by using a series of Na-type cation exchange resins to obtain purified solution B. The purified solution B is continuously fed into the salt chamber of the bipolar membrane electrodialysis device. The DC power supply is turned on and the voltage is controlled at 1.5V / membrane pair to 2.5V / membrane pair. The solution in the salt chamber is then circulated back after being heated to 30℃~45℃ by a plate heat exchanger. Deionized water is added to the acid chamber of the bipolar membrane electrodialysis device to circulate the solution in the acid chamber and recover the carbon dioxide gas generated in the acid chamber. Deionized water is added to the alkali chamber of the bipolar membrane electrodialysis device, and the solution in the alkali chamber is circulated back after being controlled to 30℃~45℃ by a plate heat exchanger. When the NaOH solution concentration reaches 5% to 15%, part of the NaOH solution is diverted to the alkali storage tank to obtain NaOH solution.

2. The method for treating carbonate brine based on bipolar membrane electrodialysis according to claim 1, characterized in that, The purified solution B is continuously fed into the salt chamber of a bipolar membrane electrodialysis device, and then the process further includes: The diluted brine, whose concentration has decreased in the salt chamber, is continuously circulated back to the salt chamber and mixed with the continuously supplied refined liquid B for cyclic electrolysis.

3. The method for treating carbonate brine based on bipolar membrane electrodialysis according to claim 1, characterized in that, The purified solution is then fed into an ion exchange system to obtain purified solution B, which further includes: The purified liquid B is transported to an ultrafiltration system, where a microporous filter with a filtration accuracy of not less than 0.5 μm is used to remove colloidal substances, thereby obtaining an ultrafiltration purified liquid. The ultrafiltration purified solution is delivered to the salt chamber of the bipolar membrane electrodialysis device.

4. The method for treating carbonate brine based on bipolar membrane electrodialysis according to claim 1, characterized in that, The primary filtrate is then conveyed to an activated carbon adsorption tower, comprising: The primary filtrate is conveyed to an adsorption tower filled with activated carbon at an empty tower flow rate of 0.2 m / h to 1.2 m / h. The activated carbon is coconut shell-based granular carbon with a particle size of 1.0 mm to 3.0 mm and an iodine value of ≥800 mg / g.

5. The method for treating carbonate brine based on bipolar membrane electrodialysis according to claim 1, characterized in that, The activated carbon adsorption tower adopts a dual-tower series operation to control the total organic carbon value of the final effluent to be <3 mg / L.

6. The method for treating carbonate brine based on bipolar membrane electrodialysis according to claim 1, characterized in that, Replenishing the acid chamber of the bipolar membrane electrodialysis device with deionized water to circulate the solution within the acid chamber includes: The acid chamber circulating liquid is passed through a PP filter or bag filter with a filtration accuracy of not less than 5μm~10μm before being returned to the acid chamber, and the acid chamber circulating current density is controlled to be 400A / m²~1000A / m².

7. The method for treating carbonate brine based on bipolar membrane electrodialysis according to claim 1, characterized in that, Replenishing the alkali chamber of the bipolar membrane electrodialysis device with deionized water to circulate the solution within the alkali chamber includes: The circulating current density in the alkali chamber is controlled to be 400A / m²~1000A / m².

8. The method for treating carbonate brine based on bipolar membrane electrodialysis according to claim 1, characterized in that, The method further includes chemical cleaning of the bipolar membrane electrodialysis device, including: A 2% to 4% HCl solution was fed into the device and circulated for 12 hours for cleaning. Pure water is supplied to the device for 12 hours of circulating cleaning. A NaOH solution with a mass concentration of 2% to 4% was fed into the device and circulated for 12 hours for cleaning. Pure water is then pumped back into the device for 12 hours of continuous cleaning.

9. A treatment device for carbonate brine based on bipolar membrane electrodialysis, characterized in that, The apparatus is applicable to the method according to any one of claims 1 to 8, wherein the apparatus comprises: The salt chamber is used to hold and circulate refined liquid B. The alkali chamber is used to hold and circulate NaOH solution and is connected to the alkali storage tank. Acid chamber, used to generate and recover carbon dioxide gas; A bipolar membrane stack includes at least two bipolar membrane chambers connected in series, each of which has an inlet and an outlet communicating with the salt chamber, alkali chamber, and acid chamber; The first circulation pipeline connects the outlet of the salt chamber to the inlet of the salt chamber of the bipolar membrane stack. A first plate heat exchanger, a first pump body, and a first filter are sequentially arranged along the material flow direction on the first circulation pipeline. The second circulation pipeline connects the outlet of the alkali chamber to the inlet of the alkali chamber of the bipolar membrane stack. A second plate heat exchanger, a second pump body, and a second filter are sequentially arranged along the material flow direction on the second circulation pipeline. The third circulation pipeline connects the outlet of the acid chamber to the inlet of the acid chamber of the bipolar membrane stack. A third pump body and a third filter are sequentially arranged along the flow direction on the third circulation pipeline.

10. The processing apparatus according to claim 9, characterized in that, The first filter, the second filter, and the third filter are precision filters, and the third filter is a PP filter or a bag filter with a filtration accuracy of not less than 5μm~10μm.

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