Anti-blocking electrodialysis wastewater treatment system and method for resource utilization of carbon dioxide

Abstract

The application belongs to the field of high-salinity industrial wastewater treatment, and discloses a resource utilization carbon dioxide anti-blocking electrodialysis wastewater treatment system and method. The system comprises a water inlet subsystem, a security subsystem and an electrodialysis subsystem. The application solves the problems of membrane stack blocking by suspended impurities in high-salinity industrial wastewater and membrane stack blocking by concentrated salt scale, and utilizes CO2 in a chemical process, realizes resource utilization of CO2, and prolongs the efficient and stable operation time of the electrodialysis.

Description

Technical Field

[0001] This invention belongs to the field of high-salt industrial wastewater treatment, and more specifically, relates to a non-clogging electrodialysis wastewater treatment system and method that utilizes carbon dioxide for resource recovery. Background Technology

[0002] Currently, the water reuse rate of industrial enterprises above a certain scale has reached over 91%. To improve the reuse rate of industrial wastewater, the demand for resource-based treatment of high-salinity industrial wastewater is gradually increasing. Electrodialysis technology, due to its advantages of simple operation, wide treatment range, and no environmental pollution, plays an important role in the resource recovery and recycling of high-salinity industrial wastewater. Through its unique separation mechanism, electrodialysis utilizes the selective permeability of anion and cation membranes to anions and cations, relying on a direct current electric field to induce directional migration of anions and cations. This effectively desalinates industrial wastewater, obtaining fresh water for reuse and concentrated water for further salt recovery, thus achieving wastewater resource recovery.

[0003] However, membrane clogging frequently occurs during the operation of electrodialysis units, making continuous operation difficult and reducing the treatment capacity of electrodialysis technology. Membrane clogging is mainly caused by two factors: impurities in industrial wastewater and scaling after salt concentration in the cathode chamber. For impurities in industrial wastewater clogging, current methods mainly involve adding pretreatment processes or security filters to remove suspended impurities. However, adding pretreatment processes increases the floor space required and wastewater treatment costs need further reduction. Adding security filters alone is costly due to the high amount of suspended impurities in the wastewater, requiring frequent replacements and still affecting the continuous operation of the electrodialysis unit. Scaling due to salt concentration mainly occurs in alkaline industrial wastewater. After concentration by the anion exchange membrane, the Ca in the cathode chamber... 2+ Mg 2+ CO3 2- Ions are concentrated or polarized to produce OH- - The precipitation of Ca and Mg salts causes membrane fouling. Currently, frequent electrode reversal and the addition of acid solutions are the main methods to inhibit membrane fouling. However, frequent electrode reversal affects the continuous operation of the electrodialysis unit, while adding acid solutions increases process operating costs. A better solution is needed to address the membrane fouling problem in electrodialysis units to ensure long-term stable operation.

[0004] Chinese Patent Publication No. CN109250846A discloses a saline wastewater treatment system for inhibiting scaling. It comprises a wastewater reduction unit for pretreatment, consisting of a homogenization tank, a coagulation tank, a flocculation tank, a sedimentation tank, a first filter, and a chemical dosing unit; and an electrodialysis unit consisting of first, second, third, and fourth intermediate tanks, first and second reverse osmosis devices, a microfiltration unit, and an electrodialysis unit. This process is complex, requires multiple booster pumps for transfer drive, has high land occupation and energy consumption, and high construction costs.

[0005] Chinese Patent Publication No. CN112408558A discloses a pH-controlled anti-scaling electrodialysis system and treatment process. It includes an electrodialysis reactor, a desalination tank, a concentrate tank, a pH control system, and an acid absorption system. The pH control system, consisting of an acid storage tank, an acid pump, a pipeline mixer, and an online pH meter, adds strong acid to the wastewater to regulate the pH, thereby preventing membrane scaling. However, this method requires a dedicated pH control system, posing safety risks and significantly increasing costs. Summary of the Invention

[0006] Electrodialysis is an important method for desalinating and recycling high-salinity industrial wastewater, offering advantages such as simple operation, wide treatment range, and no environmental pollution. This invention addresses the problem of membrane clogging in electrodialysis units, which limits their efficient and stable operation, reduces treatment capacity, and leads to decreased current efficiency. It proposes a carbon dioxide-based anti-clogging electrodialysis wastewater treatment system and method. This invention solves the problems of membrane clogging caused by suspended impurities and concentrated salt scaling in high-salinity industrial wastewater, and utilizes CO2 from chemical processes, achieving CO2 resource utilization and extending the efficient and stable operation time of the electrodialysis unit.

[0007] To achieve the above objectives, the first aspect of the present invention provides a clog-resistant electrodialysis wastewater treatment system for resource utilization of carbon dioxide, the system comprising an influent subsystem, a security subsystem, and an electrodialysis subsystem;

[0008] The water inlet subsystem includes a first water tank, a second water tank, a micro / nano bubble generator, and a sludge scraping device. The first and second water tanks are connected at the top. The micro / nano bubble generator is located at the bottom of the first and second water tanks and is used to generate CO2-containing bubbles and introduce them into the first and second water tanks. The sludge scraping device is located above the first water tank and is used to scrape off suspended impurities in the water. The first water tank has a sludge discharge port at the top and a water inlet pipe at the bottom, with a chemical dosing port on the water inlet pipe. The second water tank has a freshwater overflow port on the upper part of one side wall opposite to the first water tank. The bottom of the second water tank is connected to a water outlet pipe.

[0009] The security subsystem includes a security filter and an electrode water tank; the outlet pipe is connected to the inlet end of the security filter, and the outlet end of the security filter is connected to a concentrated water inlet pipe and a desalinated water inlet pipe; the electrode water tank is equipped with an electrode water outlet pipe and an electrode water inlet pipe.

[0010] The electrodialysis subsystem includes a membrane stack assembly and an electrode device. The membrane stack assembly is alternately equipped with multiple cation exchange membranes and anion exchange membranes, with adjacent anion exchange membranes and cation exchange membranes forming adjacent desalination chambers and concentrate chambers. A concentrate inlet pipe connects to the concentrate chamber, and the concentrate chamber is connected to a concentrate tank with a concentrate overflow outlet at the top via a concentrate product pipe. A desalination inlet pipe connects to the desalination chamber, and the desalination chamber is connected to a second water tank via a desalination product pipe. The electrode device includes a changeable cathode and anode, which are located on opposite sides of the membrane stack assembly. Each cathode and anode, adjacent to the membrane stack assembly, forms an electrode chamber. An electrode water outlet pipe and an electrode water inlet pipe are used to circulate the electrode water within the electrode tank between the electrode chambers and the electrode tank.

[0011] In this invention, the concentrate inlet pipe is used to send the concentrate from the security filter into the concentrate chamber, and the concentrate chamber is connected to the concentrate tank with a concentrate overflow port at the top through the concentrate product pipe; the desalination inlet pipe is used to send the desalination from the security filter into the desalination chamber, and the desalination chamber is connected to the second water tank through the desalination product pipe.

[0012] According to the present invention, preferably, the first water tank is provided with a first side wall and a second side wall, the upper part of the first side wall and the second side wall are respectively provided with a slag overflow weir and a water overflow weir, the first water tank is connected to the second water tank through the water overflow weir, the slag overflow weir is located near the slag discharge port, and the lower part of the first side wall is provided with a water inlet connected to the water inlet pipe.

[0013] According to the present invention, preferably, the water inlet subsystem further includes an air inlet, which is connected to a micro / nano bubble generator. In the present invention, the micro / nano bubble generator penetrates the bottom of the second sidewall of the first water tank, thereby placing the micro / nano bubble generator at the bottom of both the first and second water tanks.

[0014] According to the present invention, preferably, an online turbidity detector is provided at the outlet overflow weir.

[0015] According to the present invention, preferably, the micro / nano bubble generator is equipped with a pressure regulator.

[0016] According to the present invention, preferably, a slag overflow weir is provided at the slag discharge port.

[0017] According to the present invention, preferably, an online pH detector and an online conductivity monitor are provided at the freshwater overflow outlet.

[0018] According to the present invention, preferably, the second water tank is internally equipped with a baffle plate to separate the drainage from the first water tank and the drainage from the freshwater production pipe. Specifically, the second water tank is divided into left and right regions by the baffle plate. The region closer to the first water tank (left region) primarily receives drainage from the first water tank, which is pH-adjusted by CO2 supplied by the lower micro-nano bubble generator and then enters the security filter from the bottom of the left region of the second water tank. Drainage from the freshwater production pipe enters the right region of the second water tank from the upper part of the right region, undergoing multiple electrodialysis cycles together with the water at the bottom of the second water tank awaiting entry into the electrodialysis subsystem. The freshwater overflow outlet is also located at the upper part of the right region, allowing the treated drainage from the freshwater production pipe to overflow and be recycled. Furthermore, the flow rate of the outlet pipe at the bottom of the second water tank is greater than the overflow velocity from the first water tank to the second water tank, achieving multiple wastewater recycling and improving the treatment effect. Meanwhile, the freshwater production pipe enters the second water tank from the upper right side, avoiding mixing with the untreated wastewater overflowing from the first water tank. The drainage from the freshwater production pipe only mixes with the treated wastewater from the second water tank, ensuring the treatment effect of the freshwater overflowing from the upper right freshwater overflow outlet.

[0019] According to the present invention, preferably, the water outlet pipe is provided with a water flow rate regulating device.

[0020] In this invention, a first conductivity online monitoring instrument is installed at the freshwater overflow port of the second water tank, and a water flow rate regulating device is installed at the outlet pipe. By monitoring the conductivity of the water discharged from the freshwater overflow port and adjusting the water flow rate, multiple purification processes can be achieved through freshwater circulation treatment, thereby reducing the conductivity of the produced freshwater. Preferably, using the water flow rate regulating device, the flow rate of the outlet pipe at the bottom of the second water tank is adjusted to 1-5 times the overflow flow rate from the first water tank to the second water tank; the flow rate of the freshwater overflow port of the second water tank is 0.5-0.9 times the overflow flow rate from the first water tank to the second water tank.

[0021] According to the present invention, preferably, the security filter is provided with a detachable filter bag and a differential pressure gauge. The pore size of the detachable filter bag is 1 to 500 μm. In the present invention, the filter bag size is selected by the turbidity of the wastewater. Preferably, the filter bag size of the detachable filter bag is 5 μm and 12 μm. A concentrated and dilute water flow distribution device is provided between the detachable filter bag and the outlet of the security filter.

[0022] In this invention, the detachable filter bag can further protect the electrodialysis membrane stack from clogging by suspended impurities in the wastewater.

[0023] According to the present invention, preferably, the electrode device includes 3-15 pairs of cathode and anode electrode pairs; the membrane stack assembly is disposed between the cathode and anode of each pair of electrode pairs and between adjacent electrode pairs.

[0024] Each membrane stack module has 3-20 cation exchange membranes, and the number of anion exchange membranes in each membrane stack module is one less than the number of cation exchange membranes in the same membrane stack module.

[0025] According to the present invention, preferably, the side of the cathode adjacent to the membrane stack assembly forms a cathode chamber with the membrane stack assembly; the side of the anode adjacent to the membrane stack assembly forms an anode chamber with the membrane stack assembly.

[0026] According to the present invention, preferably, the electrode device further includes a DC power supply with adjustable voltage, including power supply reversal, and preferably a voltage of 90-120V.

[0027] According to the present invention, preferably, the cathode chamber is provided with a second online conductivity monitor.

[0028] According to the present invention, preferably, a concentrate return pipe is connected to the bottom of one side wall of the concentrate tank, and the concentrate return pipe is used together with the concentrate inlet pipe to send the concentrate product water of the concentrate tank and the concentrate inlet water of the security filter into the concentrate chamber.

[0029] According to the present invention, preferably, a regulating valve is provided on the concentrate return pipe.

[0030] According to the present invention, preferably, a third online conductivity monitor is provided at the concentrated water overflow outlet.

[0031] A second aspect of this invention provides a method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide in a resource-efficient manner. The method employs the aforementioned system and includes the following steps:

[0032] S1: High-salt industrial wastewater and reagents are fed into the first water tank through the inlet pipe and the dosing port, respectively; a mixed gas containing CO2 is generated into bubbles by the micro-nano bubble generator and sent into the first water tank and the second water tank; above the first water tank, the scum, suspended impurities and foam in the first water tank are discharged from the system through the scum discharge port by the scum scraping device, and the resulting scum-removed wastewater enters the second water tank;

[0033] S2: The wastewater from the second water tank is sent to the security filter through the outlet pipe for filtration; concentrated water and desalinated water are obtained at the outlet of the security filter; the concentrated water and desalinated water are sent to the concentrated water chamber and the desalinated water chamber respectively for electrodialysis treatment; at the same time, the electrode water in the electrode water tank is circulated between the electrode chamber and the electrode water tank by the electrode water outlet pipe and the electrode water inlet pipe.

[0034] S3: Obtain concentrated water in the concentrated water chamber and send it into the concentrated water tank through the concentrated water pipe; recover high-salt wastewater and further separate and recover salt resources through the concentrated water overflow outlet; obtain fresh water in the fresh water chamber and send it into the second water tank through the fresh water pipe; recover fresh water resources through the fresh water overflow outlet.

[0035] According to the present invention, preferably, in step S1, the water quality conditions of the high-salinity industrial wastewater include: pH 7-8.5, conductivity 800-5000 μs / cm, total hardness 50-400 mg / L, total alkalinity 50-800 mg / L, TDS 300-2500 mg / L, COD 30-100 mg / L, TOC 6-25 mg / L, and turbidity 1.0-3.5 NTU. According to the present invention, preferably, in step S1, the agent is at least one of a coagulant, a flocculant, and a scale inhibitor; preferably, the dosage ratio of the coagulant, flocculant, and scale inhibitor is (1-10):(150-300):(0.1-1.5).

[0036] In this invention, within the first water tank, bubbles generated by a micro-nano bubble generator carry the pharmaceutical agent upwards. These bubbles disperse the agent while simultaneously capturing suspended solids in the wastewater and bringing them to the top of the first water tank. The scum, suspended impurities, and foam are then discharged from the top of the first water tank via a scraper, resulting in descum-removed wastewater that flows into the second water tank through the overflow weir. Inside the second water tank, a CO2-containing mixed gas is introduced through the micro-nano bubble generator, lowering the pH of the wastewater and increasing the HCO3- content. - Reduces H2CO3 concentration, improves wastewater pH stability, and resists OH- generated by concentration polarization of the membrane stack during shock electrodialysis operation. - .

[0037] According to the present invention, preferably, in step S1: the size of the bubble is adjusted by the pressure regulator, and the diameter of the bubble is 1μm to 80μm, preferably 20 to 40μm.

[0038] According to the present invention, preferably, in step S1: the CO2-containing mixed gas is the gas obtained by flue gas through a capture and separation process and / or the gas purified by flue gas through dust removal, desulfurization and denitrification, and the temperature of the CO2-containing mixed gas is 40-120°C, preferably 60-80°C.

[0039] In this invention, when the CO2-containing mixed gas is obtained from flue gas through a capture and separation process, it can be heated by supplementary heat treatment (e.g., by exchanging heat between the flue gas in the plant and the CO2-containing mixed gas, thereby heating the CO2-containing mixed gas) to bring the temperature of the CO2-containing mixed gas to 40–120°C. When the CO2-containing mixed gas is obtained from flue gas after dust removal, desulfurization, and denitrification purification, the temperature of the CO2-containing mixed gas is in the range of 40–120°C. A temperature of 40–120°C, preferably 60–80°C, can increase the solubility of CO2 in wastewater.

[0040] According to the present invention, preferably, in step S1, the volume ratio of the CO2-containing mixed gas and the high-salt industrial wastewater is in the range of 5:1 to 25:1, preferably 15:1 to 20:1.

[0041] According to the present invention, preferably, in step S1, the ratio of the amount of CO2-containing mixed gas fed into the first and second water tanks via the micro-nano bubble generator is in the range of 1:1 to 1:10, preferably 1:4 to 1:6.

[0042] According to the present invention, preferably, in step S1: the turbidity of the sludge removal wastewater is monitored by the online turbidity detector, and the turbidity of the sludge removal wastewater is controlled to be less than 0.6 NTU by adjusting at least one of the dosage of the reagent, the air intake of the air inlet, the output power of the pressure regulator and the sludge scraping device.

[0043] In this invention, the feed rate of the dosing port, air inlet, and water inlet, as well as the power and frequency of the sludge scraping device, can be adjusted to achieve a match between the amount of high-salt industrial wastewater being treated and the amount of added reagents.

[0044] According to the present invention, preferably, in step S1: the pH of the effluent at the freshwater overflow outlet is monitored using the pH online detector, and the pH of the effluent at the freshwater overflow outlet is controlled to be less than 7 by adjusting the air intake at the air inlet and / or the proportion of CO2 in the CO2-containing mixed gas; preferably, the proportion of CO2 in the CO2-containing mixed gas is in the range of 10%-80%, more preferably 20%-40%.

[0045] In this invention, the CO2-containing mixed gas contains nitrogen, and the proportion of CO2 in the CO2-containing mixed gas can be adjusted by adjusting the proportion of nitrogen.

[0046] According to the present invention, preferably, in step S1: the collection and separation process is at least one of pressure swing adsorption, molecular sieve adsorption, organic amine adsorption and membrane separation, and preferably, the collection and separation process is pressure swing adsorption.

[0047] According to the present invention, preferably, in step S2: when the differential pressure gauge measures a pressure difference of ≥0.1 MPa in the security filter, or preferably, when the differential pressure gauge measures a pressure difference of ≥0.15 MPa in the security filter, the removable filter bag in the security filter is replaced.

[0048] In this invention, the water quality of the wastewater after treatment by the security filter is consistent. The concentrated and dilute water flow distribution device is used to distribute the effluent after treatment by the security filter to the concentrated water inlet pipe and the dilute water inlet pipe. The concentrated and dilute water flow distribution device only controls the flow ratio of the concentrated water inlet and the dilute water inlet. According to this invention, preferably, in step S2, the ratio of the dilute water inlet to the concentrated water inlet is 10:1 to 2:1, preferably 3:1 to 6:1.

[0049] According to the present invention, preferably, in step S2: the method further includes swapping the positions of the cathode and the anode, preferably, the swapping time is determined according to the conductivity of the cathode chamber, and more preferably, the swapping interval is 0.5-2h.

[0050] In this invention, by interchangeing the positive and negative electrodes, the desalination chamber and concentrate chamber within the membrane stack assembly can be interchanged, thereby preventing fouling on the concentrate chamber side of the membrane stack.

[0051] According to the present invention, preferably, in step S2: the polar water is a NaCl aqueous solution with a concentration of 0.5-3%; the ratio of the polar water to the fresh water inlet is 1:(8-15).

[0052] In this invention, the electrode water can wash away the OH- enriched by concentration polarization on the cathode surface. - Ions, to prevent scaling (such as OH-) - The enrichment of ions (resulting in precipitation) and the removal of other ions prevent ion enrichment. Furthermore, it can remove bubbles (such as O2, Cl2, H2, etc.) that may be generated during the cathode and anolyte electrolysis processes, extending the electrode life and ensuring long-term stable operation. Additionally, the electrode water also functions as an electrolyte, allowing Na+ in the electrode water to pass between the electrode plates. + Ions and Cl - Ions migrate to prevent the ionization of H2O, avoid concentration polarization, and slow down the OH- on the electrode plate. -Ion enrichment.

[0053] According to the present invention, preferably, in step S3: the method further includes sending a portion of the concentrate product water in the concentrate tank as reflux concentrate water together with the concentrate inlet water into the concentrate chamber;

[0054] The amount of reflux concentrate is determined based on the conductivity of the water at the concentrate overflow outlet. Preferably, the ratio of the amount of reflux concentrate to the amount of concentrate inlet is 1:1 to 10:1, and more preferably 3:1 to 5:1.

[0055] The beneficial effects of the technical solution of this invention are as follows: This invention solves the problems of membrane stack blockage by suspended impurities and membrane stack blockage by concentrated salt in the integrated treatment of high-salt industrial wastewater, and utilizes CO2 from the chemical process to achieve CO2 resource utilization, and extends the efficient and stable operation time of electrodialysis. Specifically:

[0056] 1. This invention targets factory flue gas, making resource-efficient use of its CO2 content. This achieves carbon reduction in the flue gas while simultaneously removing suspended impurities from wastewater and increasing HCO3 content in the wastewater. - Concentration, reduce CO3 2- Concentration, neutralization of OH generated by polarization - This reduces the pH of the wastewater, protects the membrane stack of the electrodialysis unit, prevents membrane stack clogging and scaling, achieves waste treatment with waste, and increases the efficient and stable operation time of the electrodialysis unit at low cost, thereby improving the treatment capacity of the electrodialysis unit.

[0057] 2. This invention innovatively proposes a water tank structure that can purify wastewater, improve the processing capacity of the electrodialysis subsystem, and enhance current efficiency.

[0058] 3. This invention improves the utilization efficiency of CO2 and the treatment effect of wastewater by using a micro-nano bubble generator.

[0059] 4. This invention utilizes a mixed gas containing CO2 to regulate and treat wastewater, maintaining the pH of the wastewater and avoiding damage to the electrodialysis membrane stack caused by fluctuations in wastewater quality during acid solution regulation, thereby improving the shock resistance of the electrodialysis device.

[0060] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0061] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0062] Figure 1A schematic diagram of a non-clogging electrodialysis wastewater treatment system for resource utilization of carbon dioxide provided in Embodiment 1 of the present invention is shown.

[0063] Figure 2 The diagram shows the membrane stack assembly and electrode device of an anti-clogging electrodialysis wastewater treatment system for resource utilization of carbon dioxide provided by the present invention.

[0064] Figure 3(a) shows the changes in freshwater recovery rate in wastewater treatment of Example 1 and Comparative Example 2 of the present invention (in Figure 3(a), "40% CO2 at 60°C" is Example 1, and "mixed gas without CO2" is Comparative Example 2).

[0065] Figure 3(b) shows the changes in desalination rate of wastewater treatment in Example 1 and Comparative Example 2 of the present invention.

[0066] Figure 3(c) shows the changes in current efficiency of wastewater treatment in Example 1 and Comparative Example 2 of the present invention.

[0067] Figure 3(d) shows the pH fluctuations in the initial water quality of the untreated wastewater in Example 1 and Comparative Example 3 of the present invention.

[0068] Figure 3(e) shows the variation and fluctuation of total hardness in the initial water quality of the untreated wastewater in Example 1 and Comparative Example 3 of the present invention.

[0069] Figure 3(f) shows the variation and fluctuation of total alkalinity in the initial water quality of the untreated wastewater in Example 1 and Comparative Example 3 of the present invention.

[0070] Figure 3(g) shows the changes in desalination rate of wastewater treatment in Example 1 and Comparative Example 3 of the present invention (in Figure 3(g), "CO2 mixed gas" is Example 1 and "hydrochloric acid solution" is Comparative Example 3).

[0071] The annotations in the attached figures are explained as follows:

[0072] CM: Cation exchange membrane; AM: Anion exchange membrane;

[0073] 1 First water tank, 2 Second water tank, 3 Micro-nano bubble generator, 4 Sludge scraping device, 5 Water overflow weir, 6 Air inlet, 7 Water inlet, 8 Water inlet pipe, 9 Chemical dosing port, 10 Sludge discharge port, 11 Fresh water overflow port, 12 Water outlet pipe, 13 Sludge discharge overflow weir, 14 Baffle plate;

[0074] 15 Security filter, 16 Electrode water tank, 17 Concentrate inlet pipe, 18 Freshwater inlet pipe, 19 Electrode water outlet pipe, 20 Electrode water inlet pipe;

[0075] 21 Cathode, 22 Anode, 23 Concentrate product pipe, 24 Concentrate overflow port, 25 Concentrate tank, 26 Freshwater product pipe, 27 Concentrate return pipe, 28 Regulating valve. Detailed Implementation

[0076] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0077] In the following Example 1:

[0078] The coagulant was purchased from Hubei Shishun Biotechnology Co., Ltd., CAS No.: 26062-79-3;

[0079] The flocculant was purchased from Hubei Chengfeng Chemical Co., Ltd., CAS No.: 9003-04-7;

[0080] The scale inhibitor was purchased from Chongqing Ruiya Biotechnology Co., Ltd., model BF-108.

[0081] In the following Example 2:

[0082] The coagulant was purchased from Shanghai Jiejing Chemical Co., Ltd., model: PAC;

[0083] The flocculant was purchased from Shandong Yonglida New Material Technology Co., Ltd., CAS No.: 9003-05-8;

[0084] The scale inhibitor was purchased from Chongqing Ruiya Biotechnology Co., Ltd., model BF-108.

[0085] In the following Example 3:

[0086] The coagulant was purchased from Hubei Shishun Biotechnology Co., Ltd., CAS No.: 26062-79-3;

[0087] The flocculant was purchased from Hubei Yongkuo Technology Co., Ltd., CAS No.: 26590-05-06;

[0088] The scale inhibitor was purchased from Hubei Xinrunde Chemical Co., Ltd., CAS No.: 1429-50-1.

[0089] Example 1

[0090] This embodiment provides a non-clogging electrodialysis wastewater treatment system that utilizes carbon dioxide as a resource, such as... Figure 1 As shown, the system includes an influent subsystem, a security subsystem, and an electrodialysis subsystem;

[0091] The water inlet subsystem includes a first water tank 1, a second water tank 2, a micro / nano bubble generator 3, and a sludge scraping device 4. The first water tank 1 and the second water tank 2 are connected at the top. The micro / nano bubble generator 3 is located at the bottom of the first water tank 1 and the second water tank 2, and is used to generate CO2-containing bubbles and introduce the bubbles into the first water tank 1 and the second water tank 2. The water inlet subsystem also includes an air inlet 6, which is connected to the micro / nano bubble generator. The sludge scraping device 4 is located above the first water tank 1 and is used to scrape sludge. Suspended impurities in the water; the first water tank 1 is provided with a slag discharge port 10 at the top and a water inlet pipe 8 at the bottom, and a chemical dosing port 9 is provided on the water inlet pipe 8; the first water tank 1 is provided with a first side wall and a second side wall, and the upper parts of the first side wall and the second side wall are respectively provided with a slag discharge overflow weir 13 and a water outlet overflow weir 5. The first water tank 1 is connected to the second water tank 2 through the water outlet overflow weir 5. The slag discharge overflow weir 13 is located close to the slag discharge port 10. The lower part of the first side wall is provided with a water inlet 7, which is connected to the water inlet pipe 8;

[0092] The second water tank 2 is provided with a fresh water overflow port 11 on the upper part of the side wall opposite to the first water tank 1; the bottom of the second water tank 2 is connected to a water outlet pipe 12;

[0093] Furthermore, an online turbidity detector (not shown) is installed at the overflow weir 5; the micro-nano bubble generator 3 is equipped with a pressure regulator; a slag discharge overflow weir 13 is installed at the slag discharge port 10; an online pH detector and a first conductivity online monitor are installed at the freshwater overflow port 11; a baffle plate 14 is installed inside the second water tank 2 to separate the drainage from the first water tank 1 and the drainage from the freshwater production pipe 26; and a water flow rate regulating device is installed on the water outlet pipe 12.

[0094] The security subsystem includes a security filter 15 and an electrode water tank 16; the outlet pipe 12 is connected to the inlet end of the security filter 15, and the security filter 15 is equipped with a removable filter bag and a differential pressure gauge. The filter size of the removable filter bag is 20μm; a concentrated and dilute water flow distribution device is provided between the removable filter bag and the outlet end of the security filter 15, and the outlet end of the security filter 15 is connected to a concentrated water inlet pipe 17 and a dilute water inlet pipe 18. The concentrated and dilute water flow distribution device is used to distribute the effluent filtered by the removable filter bag to the concentrated water inlet pipe 17 and the dilute water inlet pipe 18; the electrode water tank 16 is equipped with an electrode water outlet pipe 19 and an electrode water inlet pipe 20.

[0095] The electrodialysis subsystem includes a membrane stack assembly and an electrode device; the electrode device includes six pairs of interchangeable cathodes 21 and anodes 22, and a DC power supply; the membrane stack assembly is disposed between the cathode and anode of each electrode pair and between adjacent electrode pairs; each membrane stack assembly is provided with eight cation exchange membranes CM and seven anion exchange membranes AM, the cation exchange membranes and anion exchange membranes being alternately arranged, and adjacent anion exchange membranes and cation exchange membranes forming adjacent desalination chambers and concentrate chambers; The concentrate inlet pipe 17 is used to deliver the concentrate from the security filter into the concentrate chamber, which is connected to the concentrate tank 25, which has a concentrate overflow port 24 at the top, via the concentrate product pipe 23. The desalination inlet pipe 18 is used to deliver the desalination from the security filter into the desalination chamber, which is connected to the second water tank 2 via the desalination product pipe 26. The side of the cathode adjacent to the membrane stack assembly forms the cathode chamber, and the side of the anode adjacent to the membrane stack assembly forms the anode chamber. Figure 2 As shown, in this embodiment, the cathode and the adjacent cation exchange membrane constitute a cathode chamber; the anode and the adjacent cation exchange membrane constitute an anode chamber; the cathode chamber is equipped with a second online conductivity monitor; the electrode water outlet pipe 19 and the electrode water inlet pipe 20 are used to realize the circulation of electrode water in the electrode water tank 16 between the cathode chamber and the electrode water tank 16, and between the anode chamber and the electrode water tank 16.

[0096] A concentrate return pipe 27 is connected to the bottom of one side wall of the concentrate tank 25. The concentrate return pipe 27 is used together with the concentrate inlet pipe 17 to send the concentrate produced water from the concentrate tank 25 and the concentrate inlet water from the security filter 15 into the concentrate chamber. A regulating valve 28 is provided on the concentrate return pipe 27. A third conductivity online monitoring instrument is provided at the concentrate overflow port 24.

[0097] This embodiment also provides a method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide in a resource-based manner. The method uses the system described above. The wastewater treated by the method is high-salt organic wastewater generated by a chemical enterprise producing polyvinyl alcohol products. The water quality is as follows: pH 8.45, conductivity 2620 μs / cm, total hardness 202 mg / L, total alkalinity 386 mg / L, TDS 1066 mg / L, COD 32 mg / L, TOC 6.68 mg / L, and turbidity 1.56 NTU.

[0098] The method includes the following steps:

[0099] S1: The high-salinity industrial wastewater and reagents (composed of 3 ppm coagulant, 200 ppm flocculant, and 1 ppm scale inhibitor) are respectively fed into the first water tank through the inlet pipe 8 and the dosing port 9; a CO2-containing mixed gas (40% CO2, 60°C, obtained from flue gas via pressure swing adsorption) is generated into bubbles by the micro / nano bubble generator 3 and then fed into the first water tank 1 and the second water tank 2 (the CO2-containing mixed gas in the first and second water tanks...) The volume ratio of the mixed gas containing CO2 to the high-salt industrial wastewater is 16:1. The pressure regulator of the micro-nano bubble generator is adjusted to control the bubble size to 40μm. Above the first water tank 1, the scum, suspended impurities and foam in the first water tank are discharged from the system through the scum outlet 10 by the scum scraping device (the turbidity of the scum-removed wastewater is controlled by adjusting the output power of the scum scraping device). The scum-removed wastewater enters the second water tank through the overflow weir 5.

[0100] S2: The wastewater from the sludge removal process in the second water tank is sent to the security filter 15 through the outlet pipe 12 for filtration (using the water flow regulating device installed at the outlet pipe 12, the water flow rate of the outlet pipe 12 is adjusted to twice the overflow flow rate from the first water tank to the second water tank). Specifically: the second water tank is divided into two areas, left and right, by a baffle plate in the middle. The area near the first water tank (left area) is mainly the drainage from the first water tank (i.e., the wastewater from the sludge removal process). It is affected by the pH adjustment effect of CO2 added by the micro-nano bubble generator at the bottom, and then enters the security filter from the bottom of the left area of ​​the second water tank. The drainage from the freshwater production pipe enters the right area of ​​the second water tank from the upper part of the right area, and undergoes multiple electrodialysis cycles together with the water in the bottom of the second water tank that is to enter the electrodialysis subsystem. The freshwater overflow outlet is also in the upper part of the right area. The drainage from the freshwater production pipe after multiple treatments overflows and is recycled through the freshwater overflow outlet. Furthermore, the flow rate of the outlet pipe at the bottom of the second water tank is greater than the overflow velocity from the first water tank to the second water tank, enabling multiple cycles of wastewater treatment and improving the treatment effect. Simultaneously, the freshwater production pipe enters the second water tank from the upper right side, preventing mixing with the untreated wastewater overflowing from the first water tank. The drainage from the freshwater production pipe only mixes with the treated wastewater from the second water tank, ensuring the effective treatment of the freshwater overflowing from the upper right side outlet.

[0101] The turbidity of the water in the outlet pipe 12 is 0.25 NTU, the pH reaches 6.82, and the CO2 utilization efficiency in the gas is 41.4%.

[0102] The concentrated and desalinated water flow distribution device distributes the outflow at the outlet of the security filter 15 to obtain concentrated water and desalinated water. The concentrated water and desalinated water have the same water quality, only the flow rate is different, and the flow rate ratio is desalinated water:concentrated water = 5:1. The concentrated water and desalinated water are respectively sent to the concentrated water chamber and the desalinated water chamber for electrodialysis treatment (110V DC power), and the cathode 21 and anode 22 are swapped every 1 hour. At the same time, the electrode water outlet pipe 19 and the electrode water inlet pipe 20 are used to make the electrode water (the electrode water is a 1% NaCl aqueous solution; the ratio of electrode water to desalinated water is 1:10) in the electrode water tank 16 circulate between the cathode chamber and the electrode water tank 16, and between the anode chamber and the electrode water tank 16, to protect the membrane stack.

[0103] S3: Concentrated water is obtained in the concentrated water chamber and sent to the concentrated water tank 25 through the concentrated water pipe 23. Part of the concentrated water in the concentrated water tank 25 is sent to the concentrated water chamber as return concentrated water together with the concentrated water inlet. The regulating valve 28 is adjusted to control the ratio of the amount of return concentrated water to the amount of concentrated water inlet to be 3:1. The remaining concentrated water in the concentrated water tank 25 is used as a salt resource and is recovered through the concentrated water overflow port 24. Fresh water is obtained in the fresh water chamber and sent to the second water tank 2 through the fresh water pipe 26. Fresh water resources are recovered through the fresh water overflow port 11.

[0104] After the system has been running stably for 2 hours, the conductivity has reached 667 μs / cm, the TDS has reached 298 mg / L, the total alkalinity has reached 45 mg / L, and the total hardness has reached 15 mg / L.

[0105] The conductivity of the water effluent from the concentrated water overflow outlet 24 reaches 11663 μs / cm, the TDS reaches 4822 mg / L, the total alkalinity reaches 1088 mg / L, and the total hardness reaches 336 mg / L.

[0106] In this embodiment, the freshwater recovery rate after wastewater desalination treatment is 86.2%, the desalination rate is 74.5%, and the system current efficiency is 72.2%.

[0107] Example 2

[0108] This embodiment provides a method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide in a resource-based manner. The method adopts the system of Embodiment 1. The wastewater treated by the method is high-salt organic wastewater produced by a refining and chemical enterprise, with the following water quality: pH 7.32, conductivity 1236 μs / cm, total hardness 96 mg / L, total alkalinity 117 mg / L, TDS 525 mg / L, COD 37 mg / L, TOC 12 mg / L, and turbidity 2.45 NTU.

[0109] The method includes the following steps:

[0110] S1: The high-salinity industrial wastewater and reagents (composed of 4 ppm coagulant, 220 ppm flocculant, and 0.3 ppm scale inhibitor) of this embodiment are respectively sent into the first water tank through the inlet pipe 8 and the dosing port 9; a CO2-containing mixed gas (CO2 content of 30%, temperature of 65°C, gas obtained from flue gas through pressure swing adsorption process) is passed through the micro-nano bubble generator 3 to form bubbles and sent into the first water tank 1 and the second water tank 2 (the CO2-containing mixed gas in the first water tank and the second water tank are...) The volume ratio of the mixed gas containing CO2 to the high-salt industrial wastewater is 15:1. The pressure regulator of the micro-nano bubble generator is adjusted to control the bubble size to 25μm. Above the first water tank 1, the scum, suspended impurities and foam in the first water tank are discharged from the system through the scum outlet 10 by the scum scraping device (the turbidity of the scum-removed wastewater is controlled by adjusting the output power of the scum scraping device). The scum-removed wastewater enters the second water tank through the overflow weir 5.

[0111] S2: The wastewater from the slag removal process in the second water tank is sent to the security filter 15 through the outlet pipe 12 for filtration (using the water flow regulating device installed at the outlet pipe 12, the water flow rate of the outlet pipe 12 is adjusted to 1.5 times the overflow flow rate from the first water tank to the second water tank). Specifically: the second water tank is divided into two areas by a baffle plate in the middle. The area near the first water tank (the left area) is mainly the drainage from the first water tank (i.e., the wastewater from the slag removal process). It is affected by the pH adjustment effect of CO2 added by the micro-nano bubble generator at the bottom, and then enters the security filter from the bottom of the left area of ​​the second water tank. The drainage from the freshwater production pipe enters the right area of ​​the second water tank from the upper part of the right area. It undergoes multiple electrodialysis cycles together with the water in the bottom of the second water tank that is to enter the electrodialysis subsystem. The freshwater overflow outlet is also in the upper part of the right area. The drainage from the freshwater production pipe after multiple treatments overflows and is recycled through the freshwater overflow outlet. Furthermore, the flow rate of the outlet pipe at the bottom of the second water tank is greater than the overflow velocity from the first water tank to the second water tank, enabling multiple cycles of wastewater treatment and improving the treatment effect. Simultaneously, the freshwater production pipe enters the second water tank from the upper right side, preventing mixing with the untreated wastewater overflowing from the first water tank. The drainage from the freshwater production pipe only mixes with the treated wastewater from the second water tank, ensuring the effective treatment of the freshwater overflowing from the upper right side outlet.

[0112] The turbidity of the water in the outlet pipe 12 is 0.33 NTU, the pH reaches 6.35, and the CO2 utilization efficiency in the gas is 38.6%.

[0113] The concentrated and desalinated water flow distribution device distributes the outflow at the outlet of the security filter 15 to obtain concentrated water and desalinated water inlet. The concentrated water and desalinated water inlet have the same water quality, only the flow rate is different, and the flow rate ratio is desalinated water:concentrated water = 6:1. The concentrated water and desalinated water inlet are respectively sent to the concentrated water chamber and the desalinated water chamber for electrodialysis treatment (100V DC power), and the cathode 21 and anode 22 are swapped every 40 minutes. At the same time, the electrode water outlet pipe 19 and the electrode water inlet pipe 20 are used to make the electrode water (the electrode water is a 1.5% concentration NaCl aqueous solution; the ratio of electrode water to desalinated water inlet is 1:10) in the electrode water tank 16 circulate between the cathode chamber and the electrode water tank 16, and between the anode chamber and the electrode water tank 16, to protect the membrane stack.

[0114] S3: Concentrated water is obtained in the concentrated water chamber and sent to the concentrated water tank 25 through the concentrated water pipe 23. Part of the concentrated water in the concentrated water tank 25 is sent to the concentrated water chamber as return concentrated water together with the concentrated water inlet. The regulating valve 28 is adjusted to control the ratio of the amount of return concentrated water to the amount of concentrated water inlet to be 4:1. The remaining concentrated water in the concentrated water tank 25 is used as a salt resource and is recovered through the concentrated water overflow port 24. Fresh water is obtained in the fresh water chamber and sent to the second water tank 2 through the fresh water pipe 26. Fresh water resources are recovered through the fresh water overflow port 11.

[0115] After the system has been running stably for 2 hours, the conductivity has reached 217 μs / cm, the TDS has reached 108 mg / L, the total alkalinity has reached 12 mg / L, and the total hardness has reached 17 mg / L.

[0116] The conductivity of the water effluent from the concentrated water overflow outlet 24 reaches 4575 μs / cm, the TDS reaches 1936 mg / L, the total alkalinity reaches 447 mg / L, and the total hardness reaches 235 mg / L.

[0117] In this embodiment, the freshwater recovery rate after wastewater desalination treatment is 82.6%, the desalination rate is 80.5%, and the system current efficiency is 76.3%.

[0118] Example 3

[0119] This embodiment provides a method for treating non-clogging electrodialysis wastewater by utilizing carbon dioxide in a resource-based manner. The only difference between the system used in this method and that in Embodiment 1 is that the size of the detachable filter bag is 5μm. The wastewater treated by this method is high-salt organic wastewater produced by a refining and chemical enterprise, with the following water quality: pH 7.26, conductivity 1775μs / cm, total hardness 126mg / L, total alkalinity 223mg / L, TDS 675mg / L, COD 55mg / L, TOC 17mg / L, and turbidity 2.98NTU.

[0120] The method includes the following steps:

[0121] S1: The high-salinity industrial wastewater and reagents (composed of 5 ppm coagulant, 250 ppm flocculant, and 0.5 ppm scale inhibitor) of this embodiment are respectively sent into the first water tank through the inlet pipe 8 and the dosing port 9; a mixed gas containing CO2 (CO2 content of 20%, temperature of 60°C, gas obtained from flue gas through pressure swing adsorption process) is passed through the micro-nano bubble generator 3 to form bubbles and sent into the first water tank 1 and the second water tank 2 (the mixed gas containing CO2 in the first water tank and the second water tank are...) The volume ratio of the mixed gas containing CO2 to the high-salt industrial wastewater is 20:1. The pressure regulator of the micro-nano bubble generator is adjusted to control the bubble size to 30μm. Above the first water tank 1, the scum, suspended impurities and foam in the first water tank are discharged from the system through the scum outlet 10 by the scum scraping device (the turbidity of the scum-removed wastewater is controlled by adjusting the output power of the scum scraping device). The scum-removed wastewater enters the second water tank through the overflow weir 5.

[0122] S2: The wastewater from the slag removal process in the second water tank is sent to the security filter 15 through the outlet pipe 12 for filtration (using the water flow regulating device installed at the outlet pipe 12, the water flow rate of the outlet pipe 12 is adjusted to 1.5 times the overflow flow rate from the first water tank to the second water tank). Specifically: the second water tank is divided into two areas by a baffle plate in the middle. The area near the first water tank (the left area) is mainly the drainage from the first water tank (i.e., the wastewater from the slag removal process). It is affected by the pH adjustment effect of CO2 added by the micro-nano bubble generator at the bottom, and then enters the security filter from the bottom of the left area of ​​the second water tank. The drainage from the freshwater production pipe enters the right area of ​​the second water tank from the upper part of the right area. It undergoes multiple electrodialysis cycles together with the water in the bottom of the second water tank that is to enter the electrodialysis subsystem. The freshwater overflow outlet is also in the upper part of the right area. The drainage from the freshwater production pipe after multiple treatments overflows and is recycled through the freshwater overflow outlet. Furthermore, the flow rate of the outlet pipe at the bottom of the second water tank is greater than the overflow velocity from the first water tank to the second water tank, enabling multiple cycles of wastewater treatment and improving the treatment effect. Simultaneously, the freshwater production pipe enters the second water tank from the upper right side, preventing mixing with the untreated wastewater overflowing from the first water tank. The drainage from the freshwater production pipe only mixes with the treated wastewater from the second water tank, ensuring the effective treatment of the freshwater overflowing from the upper right side outlet.

[0123] The turbidity of the water in the outlet pipe 12 is 0.52 NTU, the pH reaches 6.56, and the CO2 utilization efficiency in the gas is 31.3%.

[0124] The concentrated and desalinated water flow distribution device distributes the outflow at the outlet of the security filter 15 to obtain concentrated water and desalinated water inlet. The concentrated water and desalinated water inlet have the same water quality, only the flow rate is different, and the flow rate ratio is desalinated water:concentrated water = 3:1. The concentrated water and desalinated water inlet are respectively sent to the concentrated water chamber and the desalinated water chamber for electrodialysis treatment (100V DC power), and the positions of cathode 21 and anode 22 are swapped every 40 minutes. At the same time, the electrode water outlet pipe 19 and electrode water inlet pipe 20 are used to make the electrode water (the electrode water is a 2% NaCl aqueous solution; the ratio of electrode water to desalinated water inlet is 1:10) in the electrode water tank 16 circulate between the cathode chamber and the electrode water tank 16, and between the anode chamber and the electrode water tank 16, to protect the membrane stack.

[0125] S3: Concentrated water is obtained in the concentrated water chamber and sent to the concentrated water tank 25 through the concentrated water pipe 23. Part of the concentrated water in the concentrated water tank 25 is sent to the concentrated water chamber as return concentrated water together with the concentrated water inlet. The regulating valve 28 is adjusted to control the ratio of the amount of return concentrated water to the amount of concentrated water inlet to be 5:1. The remaining concentrated water in the concentrated water tank 25 is used as a salt resource and is recovered through the concentrated water overflow port 24. Fresh water is obtained in the fresh water chamber and sent to the second water tank 2 through the fresh water pipe 26. Fresh water resources are recovered through the fresh water overflow port 11.

[0126] After the system has been running stably for 2 hours, the conductivity has reached 388 μs / cm, the TDS has reached 178 mg / L, the total alkalinity has reached 33 mg / L, and the total hardness has reached 12 mg / L.

[0127] The conductivity of the water effluent from the concentrated water overflow outlet 24 reaches 6632 μs / cm, the TDS reaches 2533 mg / L, the total alkalinity reaches 806 mg / L, and the total hardness reaches 252 mg / L.

[0128] This embodiment achieves a freshwater recovery rate of 75% after wastewater desalination treatment, a desalination rate of 78.1%, a COD degradation rate of 52.7%, and a system current efficiency of 76.3%.

[0129] Example 4

[0130] This embodiment provides a method for treating electrodialysis wastewater that utilizes carbon dioxide to prevent clogging. The only difference between this method and Embodiment 1 is that the proportion of CO2 in the CO2-containing mixed gas is 36%, and the temperature is 70°C.

[0131] After the system has been running stably for 2 hours, the turbidity of the water in the outlet pipe 12 reaches 0.23 NTU, the pH reaches 6.22, and the CO2 utilization efficiency in the gas is 44.2%. In this embodiment, the freshwater recovery rate after wastewater desalination treatment reaches 87.2%, the desalination rate reaches 82.3%, and the device current efficiency is 76.1%.

[0132] Example 5

[0133] This embodiment provides a method for treating electrodialysis wastewater that utilizes carbon dioxide to prevent clogging. The only difference between this method and Embodiment 1 is that the proportion of CO2 in the CO2-containing mixed gas is 29%, and the temperature is 65°C.

[0134] After the system has been running stably for 2 hours, the turbidity of the water in the outlet pipe 12 reaches 0.32 NTU, the pH reaches 6.85, and the CO2 utilization efficiency in the gas is 39.2%. In this embodiment, the freshwater recovery rate after wastewater desalination treatment reaches 86.5%, the desalination rate reaches 80.2%, and the device current efficiency is 71.7%.

[0135] Example 6

[0136] This embodiment provides a method for treating electrodialysis wastewater by utilizing carbon dioxide in a way that prevents clogging. The only difference between this method and Embodiment 1 is that the proportion of CO2 in the mixed gas containing CO2 is 23%, and the temperature is 62°C.

[0137] After the system has been running stably for 2 hours, the turbidity of the water in the outlet pipe 12 reaches 0.35 NTU, the pH reaches 6.97, and the CO2 utilization efficiency in the gas is 33.6%. In this embodiment, the freshwater recovery rate after wastewater desalination treatment reaches 85.7%, the desalination rate reaches 73.6%, and the device current efficiency is 70.8%.

[0138] Examples 7-16

[0139] The only difference between Examples 7-16 and Example 1 is the proportion of CO2 in the CO2-containing gas mixture. (The proportion of CO2 in the CO2-containing gas mixture is adjusted by adjusting the proportion of nitrogen in the CO2-containing gas mixture.)

[0140] The processing effects of the systems in Examples 7-16 and Example 1 when running continuously for 2 hours are compared, as shown in Table 1.

[0141] Table 1

[0142]

[0143]

[0144] By comparing Table 1, we can find that:

[0145] When the CO2 content in the mixed gas is 20-40%, the process of this invention has excellent operating performance, exhibiting a high freshwater recovery rate, a high desalination rate, and a high current efficiency.

[0146] When the CO2 content is less than 20%, the pH, turbidity, total alkalinity and total hardness of the water in the outlet pipe 12 of the second water tank are high, indicating that the CO2 content is insufficient and the removal of total alkalinity and total hardness in the wastewater is incomplete. This leads to a large load on the electrodialysis membrane stack assembly, an increase in the frequency of clogging, and a significant decrease in performance after 2 hours of continuous operation.

[0147] When the CO2 content is higher than 40%, it is measured that the pH of the water in the outlet pipe 12 of the second water tank is low, and the content of carbonate ions and bicarbonate ions in the wastewater is high, which increases the load on the membrane stack during the operation of electrodialysis, reduces the current efficiency during operation, and leads to a decrease in wastewater desalination rate and freshwater recovery rate.

[0148] Therefore, it can be seen that by controlling the CO2 concentration (i.e., proportion) in the mixed gas used, the treatment effect of the first and second water tanks on wastewater can be significantly improved, thereby enhancing the treatment effect and current efficiency of electrodialysis.

[0149] Examples 17-27

[0150] The only difference between Examples 17-27 and Example 1 is that the temperature of the CO2-containing mixed gas is different.

[0151] Table 2 shows the processing effects of the systems in Examples 17-27 and Example 1 when they run continuously for 2 hours.

[0152] Table 2

[0153]

[0154] Comparing Table 2 reveals:

[0155] When the temperature of the mixed gas is between 60-80℃, the system of the present invention performs well, maintaining high CO2 utilization efficiency as well as high freshwater recovery rate, desalination rate and current efficiency.

[0156] When the temperature of the mixed gas is below 60℃, the CO2 utilization efficiency decreases due to the low temperature. Measurements show that the pH, turbidity, total alkalinity, and total hardness of the water in the outlet pipe 12 of the second water tank are too high, resulting in high membrane stack pressure in the electrodialysis system and reduced operating efficiency.

[0157] When the temperature of the mixed gas is higher than 80℃, the temperature is higher and the CO2 utilization efficiency is higher, but this also causes the water temperature in the outlet pipe 12 of the second water tank to rise. This affects the stability and performance of the membrane stack during the operation of the electrodialysis subsystem, reduces the ion permeability of the membrane stack during electrodialysis operation, reduces the desalination rate and current efficiency of the electrodialysis system, and leads to a decrease in efficiency and an increase in energy consumption.

[0158] The above comparison clearly shows that controlling the temperature of the CO2-containing mixed gas can effectively improve the operating performance of the electrodialysis system.

[0159] Examples 28-40

[0160] The only difference between Examples 28-40 and Example 1 is that the diameter of the bubbles is different (by adjusting the pressure regulator of the micro / nano bubble generator).

[0161] The processing effects of the systems in Examples 28-40 and Example 1 when running continuously for 2 hours are compared in Table 3.

[0162] Table 3

[0163]

[0164]

[0165] Comparing Table 3 reveals:

[0166] When the bubble size of the present invention is between 20-40 μm, the present invention can achieve a desalination rate of over 74% and a current efficiency of over 72% while maintaining a freshwater recovery rate of approximately 86% (85.8%-86.3%).

[0167] When the bubble size is less than 20μm, the CO2-containing gas mixture has a long residence time in the first and second water tanks due to its small size. Although the CO2 utilization efficiency is improved, the bubbles are in a suspended state in the wastewater. The long residence time and small size of the bubbles make it difficult for the small particles of flocculation sedimentation to be captured and floated by the bubbles. The scraping device's ability to remove suspended solids decreases, which leads to an increased load on the electrodialysis membrane stack. As a result, under the condition of approximately 86% freshwater recovery rate, the desalination rate of the electrodialysis process decreases to below 70.5%, reaching a minimum of 58.4%, and the current efficiency is below 70%, reaching a minimum of 56.7%, significantly reducing the operating effect.

[0168] When the bubble size exceeds 40 μm, the residence time of the CO2-containing gas mixture in the wastewater of the first and second water tanks decreases, leading to a decrease in CO2 utilization efficiency. This causes an increase in the pH of the water in the outlet pipe 12 of the second water tank, and consequently, an increase in Ca... 2+ and Mg 2+The decrease in removal rate leads to an increase in the load on the electrodialysis membrane stack and an acceleration of membrane stack blockage. As a result, under the condition of approximately 86% freshwater recovery rate during continuous operation for 2 hours, the desalination rate is lower than 72%, reaching a minimum of 553%, and the current efficiency is lower than 70%, reaching a minimum of 51.5%.

[0169] The above results clearly demonstrate that controlling the average size of the bubbles generated by the micro-nano bubble generator can enhance the regulation of wastewater pH, total hardness, and total alkalinity by the CO2 mixed gas in the first and second water tanks of the system and method of the present invention, prevent electrodialysis membrane blockage, and optimize the operating effect of the electrodialysis device.

[0170] Examples 41-49, Comparative Example 1

[0171] Examples 41-49 and Comparative Examples 1 differ from Example 1 only in the volume ratio of the CO2-containing mixed gas and the high-salt industrial wastewater.

[0172] Under the condition of maintaining a freshwater recovery rate of 86.2%, the treatment effects of the systems of Examples 41-49, Comparative Example 1 and Example 1 when running continuously for 6 hours are shown in Table 4.

[0173] Table 4

[0174]

[0175] * The electrodialysis desalination recovery rate was 86.2%.

[0176] Table 4 shows the results intuitively:

[0177] In Comparative Example 1, when no CO2-containing mixed gas was used, the NTU and pH of the water in the outlet pipe 12 of the second water tank were both high. Even under the operating conditions where the freshwater recovery rate was less than 70%, the electrodialysis operation effect deteriorated significantly.

[0178] After using a CO2-containing mixed gas, the water quality in the outlet pipe 12 of the second water tank was significantly purified, and the electrodialysis operation effect was enhanced.

[0179] Especially when the volume ratio of CO2-containing mixed gas and high-salt industrial wastewater is between 15:1 and 20:1, the NTU in the water in the outlet pipe 12 of the second water tank is maintained below 0.26 and the pH is maintained between 6.5 and 7. The system and process of this invention exhibit optimal performance, achieving a desalination rate of over 73% and a current efficiency of over 70% after 6 hours of continuous operation.

[0180] When the volume ratio of the CO2-containing mixed gas and the high-salinity industrial wastewater is greater than 20:1, the NTU of the water in the outlet pipe 12 of the second water tank is further purified, but the effect is not significant, and the pH is below 6.5, with CO3 in the wastewater... 2- and HCO3 - Increased concentration leads to increased load on the electrodialysis membrane stack, resulting in decreased desalination rate and current efficiency.

[0181] When the volume ratio of CO2-containing mixed gas and high-salt industrial wastewater is less than 15:1, due to insufficient gas volume, the NTU and pH of the water in the outlet pipe 12 of the second water tank are high, with NTU higher than 0.35 and pH higher than 7, resulting in poor water quality, high load on the electrodialysis membrane stack, and a decline in the operating effect of electrodialysis.

[0182] In summary, the system and process of this invention, along with the comprehensive utilization of CO2-containing mixed gas for wastewater treatment, can significantly reduce the load on the electrodialysis membrane stack, improve the electrodialysis treatment effect, and extend the operating time at the specified temperature.

[0183] Examples 50-58

[0184] The only difference between Examples 50-58 and Example 1 is that the proportion of CO2-containing mixed gas introduced into the first and second water tanks is different.

[0185] Under the condition of maintaining a freshwater recovery rate of 86.2%, the treatment effects of the systems in Examples 50-58 and Example 1 when running continuously for 2 hours are compared, as shown in Table 5.

[0186] Table 5

[0187]

[0188]

[0189] The comparison results in Table 5 show that:

[0190] In this invention, adjusting the ratio of CO2-containing mixed gas in the first and second water tanks can significantly affect the wastewater treatment effect.

[0191] When the ratio of CO2 mixed gas in the first and second water tanks is within the range of 1:4 to 1:6, the pH of the waste liquid in the first water tank remains high and the bubbles are relatively dense, resulting in good removal of NTU and total hardness. The NTU of the water in the outlet pipe 12 of the second water tank is lower than 0.25 and the total hardness is lower than 65 mg / L. Consequently, the load pressure of the electrodialysis membrane stack is low, and the desalination rate can be maintained above 74.5% and the current efficiency above 72% for 2 hours of continuous operation.

[0192] When the ratio of CO2 mixed gas in the first water tank to the second water tank is between 1:1 and 1:3, the pH of the wastewater in the first water tank drops significantly due to the higher CO2 content, with the pH values ​​all below 8. This affects the total hardness removal effect, resulting in the total hardness of the water in the outlet pipe 12 of the second water tank being higher than 75 mg / L. This increases the load on the electrodialysis membrane stack, thereby reducing the desalination rate and current efficiency after 2 hours of continuous operation.

[0193] When the ratio of CO2 mixed gas in the first and second water tanks is between 1:7 and 1:10, the low bubble concentration in the first water tank leads to poor flocculation and precipitation of calcium and magnesium ions. Furthermore, the high pH of the wastewater in the first water tank weakens the effect of the flocculant, resulting in higher NTU and total hardness in the water outlet pipe 12 of the second water tank. This increases the operating load on the electrodialysis membrane stack structure, thereby reducing the desalination rate and current efficiency.

[0194] In summary, the system and process of this invention can adjust the appropriate ratio of CO2 mixed gas in the first and second water tanks, optimize the removal effect of NTU and total hardness in wastewater, reduce the load on the electrodialysis membrane stack, and thus improve the desalination rate and current efficiency of the electrodialysis device.

[0195] Comparative Example 2

[0196] Compared with Example 1, the operation process is the same, but the mixed gas containing CO2 and the first water tank are not used. The treated wastewater directly enters the second water tank. The changes in freshwater recovery rate, desalination rate and current efficiency after wastewater desalination treatment in Comparative Example 2 and Example 1 are shown in Figures 3(a)-(b).

[0197] As can be seen from Figure 3(a), the present invention uses a mixed gas containing CO2, and the freshwater recovery rate remains above 80% within 10 hours of continuous operation. In contrast, the wastewater treated in Comparative Example 2 enters the system directly from the second water tank, which increases the membrane stack load and causes the freshwater recovery rate to gradually decrease from 85% to 56.8% during the 10-hour continuous operation.

[0198] As can be seen from Figure 3(b), the present invention utilizes a mixed gas containing CO2 to synergistically treat wastewater, reducing the pressure on the membrane stack. It achieves a desalination rate of over 70% within 8 hours of continuous operation and maintains a desalination rate of over 65% within 10 hours of continuous operation. In contrast, under the operating conditions of Comparative Example 2 without using a mixed gas containing CO2 and the first water tank, the desalination rate of the device gradually decreased from 76% to 50% within 3 hours of continuous operation. Subsequently, after 6 hours of operation, due to scaling and clogging on the membrane stack, the desalination rate dropped significantly to about 20%, and the quality of the electrodialysis permeate was significantly reduced.

[0199] As shown in Figure 3(c), under the condition of using a CO2-containing mixed gas to co-treat wastewater through the first water tank, the electrodialysis current efficiency of the present invention remained above 60% during continuous operation for 10 hours, and above 70% for the first 7 hours. However, in Comparative Example 2, without using the first water tank and without the CO2-containing mixed gas, the electrodialysis membrane stack rapidly scaled up, and the current efficiency dropped rapidly in the first 4 hours of operation, from about 75% to below 25%, and then remained at a low current efficiency, resulting in increased energy consumption for electrodialysis.

[0200] The above comparison reveals that the innovative structure of the first and second water tanks in this invention, along with the resource utilization of CO2 for synergistic wastewater treatment, can significantly improve the treatment effect of electrodialysis and reduce energy consumption, demonstrating significant advantages and application prospects.

[0201] Comparative Example 3

[0202] The difference between this comparative example and Example 1 is that the pH adjustment was performed in the first and second water tanks using a 5% hydrochloric acid solution instead of the mixed gas containing 40% CO2.

[0203] Furthermore, Comparative Example 3 and Example 1 were run continuously for 4 hours each time, with intermittent shutdowns of 5 minutes, to perform backwashing and purification operations on the membrane stacks and remove scale from their surfaces. The fluctuations in pH, total alkalinity, and total hardness of the untreated wastewater in Comparative Example 3 and Example 1 within 100 hours are shown in Figures 3(d)-(f), and the fluctuations in the desalination rate of Comparative Example 3 and Example 1 are shown in Figure (g).

[0204] Figures 3(d)-(f) show that the pH of the incoming water in the process plant fluctuates, generally ranging from 7.0 to 9.5. This invention addresses this by using a mixed gas containing 40% CO2 in the first and second water tanks to reduce alkalinity and hardness, thereby removing calcium. 2+ and Mg 2+ In contrast, Comparative Example 3 used hydrochloric acid solution to maintain a low pH in the wastewater and prevent clogging of the electrodialysis membrane stack.

[0205] As shown in Figure 3(g), the present invention utilizes a CO2-containing mixed gas to significantly maintain operational stability, with the electrodialysis desalination rate remaining above 60%, demonstrating high resistance to fluctuations. In contrast, Comparative Example 3, which uses hydrochloric acid solution to adjust the wastewater pH, can only reduce the total alkalinity of the treated wastewater, failing to reduce the total hardness. When the wastewater pH decreases, the hydrochloric acid solution causes the wastewater to exhibit a lower pH value, damaging the membrane stack and leading to a gradual decline in electrodialysis treatment capacity over long-term operation, with the desalination efficiency falling below 40% within 100 hours of operation.

[0206] The above comparison confirms that the system and method of the present invention have higher shock resistance. The CO2-containing mixed gas not only reduces the total alkalinity and total hardness of the wastewater and prevents membrane fouling, but also moderately adjusts the pH of the wastewater, counteracting the OH- generated by the concentration polarization of the membrane stack. - It will not cause the wastewater pH to drop too low, thus protecting the stable operation of the electrodialysis membrane stack.

[0207] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A clog-resistant electrodialysis wastewater treatment system for resource utilization of carbon dioxide, characterized in that, The system includes an inlet water subsystem, a security subsystem, and an electrodialysis subsystem; The water inlet subsystem includes a first water tank, a second water tank, a micro / nano bubble generator, and a sludge scraping device. The first and second water tanks are connected at the top. The micro / nano bubble generator is located at the bottom of the first and second water tanks and is used to generate CO2-containing bubbles and introduce them into the first and second water tanks. The sludge scraping device is located above the first water tank and is used to scrape off suspended impurities in the water. The first water tank has a sludge discharge port at the top and a water inlet pipe at the bottom, with a chemical dosing port on the water inlet pipe. The second water tank has a freshwater overflow port on the upper part of one side wall opposite to the first water tank. The bottom of the second water tank is connected to a water outlet pipe. The second water tank is equipped with a baffle plate to separate the drainage from the first water tank from the drainage from the freshwater production pipe; The security subsystem includes a security filter and an electrode water tank; the outlet pipe is connected to the inlet end of the security filter, and the outlet end of the security filter is connected to a concentrated water inlet pipe and a desalinated water inlet pipe; the electrode water tank is equipped with an electrode water outlet pipe and an electrode water inlet pipe. The electrodialysis subsystem includes a membrane stack assembly and an electrode device. The membrane stack assembly is alternately equipped with multiple cation exchange membranes and anion exchange membranes, with adjacent anion exchange membranes and cation exchange membranes forming adjacent desalination chambers and concentrate chambers. A concentrate inlet pipe connects to the concentrate chamber, and the concentrate chamber is connected to a concentrate tank with a concentrate overflow outlet at the top via a concentrate product pipe. A desalination inlet pipe connects to the desalination chamber, and the desalination chamber is connected to a second water tank via a desalination product pipe. The electrode device includes a changeable cathode and anode, which are located on opposite sides of the membrane stack assembly. Each cathode and anode, adjacent to the membrane stack assembly, forms an electrode chamber. An electrode water outlet pipe and an electrode water inlet pipe are used to circulate the electrode water within the electrode tank between the electrode chambers and the electrode tank.

2. The anti-clogging electrodialysis wastewater treatment system for resource utilization of carbon dioxide according to claim 1, wherein, The first water tank is provided with a first side wall and a second side wall. The upper part of the first side wall and the second side wall are respectively provided with a slag discharge overflow weir and a water outlet overflow weir. The first water tank is connected to the second water tank through the water outlet overflow weir. The slag discharge overflow weir is located near the slag discharge port. The lower part of the first side wall is provided with a water inlet, which is connected to the water inlet pipe.

3. The anti-clogging electrodialysis wastewater treatment system for resource utilization of carbon dioxide according to claim 1, wherein, The water inlet subsystem also includes an air inlet, which is connected to a micro-nano bubble generator; An online turbidity detector is installed at the outlet overflow weir; The micro-nano bubble generator is equipped with a pressure regulator. A pH online detector and a first conductivity online monitor are installed at the freshwater overflow outlet; The water outlet pipe is equipped with a water flow rate regulating device.

4. The anti-clogging electrodialysis wastewater treatment system for resource utilization of carbon dioxide according to claim 1, wherein, The security filter is equipped with a removable filter bag and a differential pressure gauge. The pore size of the removable filter bag is 1~500μm. A concentrated and dilute water flow distribution device is provided between the removable filter bag and the outlet of the security filter.

5. The anti-clogging electrodialysis wastewater treatment system for resource utilization of carbon dioxide according to claim 1, wherein, The electrode device includes 3-15 pairs of cathode and anode electrodes; the membrane stack assembly is provided between the cathode and anode of each pair of electrodes and between adjacent electrode pairs. Each membrane stack module is equipped with 3-20 cation exchange membranes, and the number of anion exchange membranes in each membrane stack module is one less than the number of cation exchange membranes in the same membrane stack module; The side of the cathode adjacent to the membrane stack assembly forms a cathode chamber with the membrane stack assembly; The side of the anode adjacent to the membrane stack assembly forms an anode chamber with the membrane stack assembly; The electrode device also includes a DC power supply; The cathode chamber is equipped with a second online conductivity monitor.

6. The anti-clogging electrodialysis wastewater treatment system for resource utilization of carbon dioxide according to claim 1, wherein, A concentrate return pipe is connected to the bottom of one side wall of the concentrate tank. The concentrate return pipe is used together with the concentrate inlet pipe to send the concentrate product water from the concentrate tank and the concentrate inlet water from the security filter into the concentrate chamber. A regulating valve is installed on the concentrate return pipe; A third online conductivity monitor is installed at the concentrated water overflow outlet.

7. A method for treating electrodialysis wastewater by utilizing carbon dioxide in a way that prevents clogging, characterized in that, The method employs the system described in any one of claims 1-6 and includes the following steps: S1: High-salt industrial wastewater and reagents are fed into the first water tank through the inlet pipe and the dosing port, respectively; a mixed gas containing CO2 is generated into bubbles by the micro-nano bubble generator and sent into the first water tank and the second water tank; above the first water tank, the scum, suspended impurities and foam in the first water tank are discharged from the system through the scum discharge port by the scum scraping device, and the resulting scum-removed wastewater enters the second water tank; S2: The wastewater from the second water tank is sent to the security filter through the outlet pipe for filtration; concentrated water and desalinated water are obtained at the outlet of the security filter; the concentrated water and desalinated water are sent to the concentrated water chamber and the desalinated water chamber respectively for electrodialysis treatment; at the same time, the electrode water in the electrode water tank is circulated between the electrode chamber and the electrode water tank by the electrode water outlet pipe and the electrode water inlet pipe. S3: Obtain concentrated water in the concentrated water chamber and send it into the concentrated water tank through the concentrated water pipe; recover high-salt wastewater and further separate and recover salt resources through the concentrated water overflow outlet; obtain fresh water in the fresh water chamber and send it into the second water tank through the fresh water pipe; recover fresh water resources through the fresh water overflow outlet.

8. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 7, wherein, In step S1: The water quality conditions of the high-salinity industrial wastewater include: pH 7-8.5, conductivity 800-5000 μs / cm, total hardness 50-400 mg / L, total alkalinity 50-800 mg / L, TDS 300-2500 mg / L, COD 30-100 mg / L, TOC 6-25 mg / L, and turbidity 1.0-3.5 NTU. The agent is at least one of coagulant, flocculant and scale inhibitor; The diameter of the bubble is 1μm~80μm; The CO2-containing mixed gas is the gas obtained from flue gas through a capture and separation process and / or the gas purified by flue gas after dust removal, desulfurization and denitrification, and the temperature of the CO2-containing mixed gas is 40~120℃. The volume ratio of the CO2-containing mixed gas and the high-salinity industrial wastewater ranges from 5:1 to 25:

1. The ratio of the CO2-containing mixed gas fed into the first and second water tanks via the micro-nano bubble generator is in the range of 1:1 to 1:

10. The turbidity of the sludge removal wastewater is monitored using the online turbidity detector, and the turbidity of the sludge removal wastewater is controlled to be less than 0.6 NTU by adjusting at least one of the following: the dosage of the reagent, the air intake of the air inlet, the output power of the pressure regulator and the sludge scraping device. The pH of the effluent at the freshwater overflow outlet is monitored using the online pH detector, and the pH of the effluent at the freshwater overflow outlet is controlled to be less than 7 by adjusting the air intake at the air inlet and / or the proportion of CO2 in the CO2-containing mixed gas.

9. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 8, wherein, The dosage ratio of the coagulant, flocculant and scale inhibitor is (1-10):(150-300):(0.1-1.5).

10. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 8, wherein, The diameter of the bubble is 20~40μm.

11. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 8, wherein, The temperature of the CO2-containing mixed gas is 60~80℃.

12. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 8, wherein, The volume ratio of the CO2-containing mixed gas and the high-salt industrial wastewater is in the range of 15:1 to 20:

1.

13. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 8, wherein, The ratio of the CO2-containing mixed gas fed into the first and second water tanks via the micro-nano bubble generator is in the range of 1:4 to 1:

6.

14. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 8, wherein, The CO2 content in the CO2-containing gas mixture ranges from 10% to 80%.

15. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 14, wherein, The CO2 content in the CO2-containing gas mixture ranges from 20% to 40%.

16. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 8, wherein, The capture and separation process is at least one of pressure swing adsorption, molecular sieve adsorption, organic amine adsorption, and membrane separation.

17. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 16, wherein, The capture and separation process is pressure swing adsorption.

18. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 7, wherein, In step S2: When the pressure difference inside the security filter is ≥0.1Mpa, replace the removable filter bag inside the security filter. The ratio of freshwater inlet to concentrated water inlet is 10:1 to 2:1; The method also includes interchangeable cathodes and anodes; The polar water is a 0.5-3% NaCl aqueous solution; the ratio of the polar water to the fresh water inlet is 1:(8-15).

19. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 18, wherein, The ratio of freshwater intake to concentrated water intake is 3:1 to 6:

1.

20. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 18, wherein, The interval between switching the cathode and anode in the method is determined based on the conductivity of the cathode chamber.

21. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 7, wherein, In step S3: The method further includes sending a portion of the concentrate product water in the concentrate tank as reflux concentrate water together with the concentrate inlet water into the concentrate chamber; The amount of reflux concentrate is determined based on the conductivity of the water effluent at the concentrate overflow outlet.

22. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 21, wherein, The ratio of the amount of reflux concentrate to the amount of concentrate inlet is 1:1 to 10:

1.

23. The method for treating anti-clogging electrodialysis wastewater by utilizing carbon dioxide according to claim 22, wherein, The ratio of the amount of reflux concentrate to the amount of concentrate inlet is 3:1 to 5:1.

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