Zero-emission combined treatment method and device for high-salinity wastewater and circulating water

Abstract

The invention discloses a zero-emission combined treatment method and device for high-salinity wastewater and circulating water, and relates to the field of water treatment.The method comprises the steps that 1, the circulating water and the high-salinity wastewater in a water collecting tank of an open cooling tower enter a diaphragm electrolytic cell for electrochemical softening treatment; (2) carrying out carbon dioxide micro-nano bubble treatment on water discharged from the cathode chamber, then carrying out sedimentation treatment, and returning the treated water to the open cooling tower water collecting tank; (3) monitoring the water quality of the circulating water and the high-salinity wastewater in real time, and discharging the circulating water and the high-salinity wastewater into a closed cooling tower water collecting tank when a discharge condition is met; (4) carrying out reverse scale precipitation treatment on the spray circulating water by using a nanocrystalline material, wherein the closed cooling tower runs under the limit concentration multiple and does not discharge water; and (5) the closed cooling tower sprays circulating water to evaporate and exchange heat, and precipitated scaling particles and crystallized salt particles are discharged after being deposited. Specific components in the high-salinity wastewater are selectively consumed to replace chemicals to remove hardness and obtain a chlorine byproduct, so that high-value utilization of the high-salinity wastewater is realized, and salt reduction and corrosion reduction effects in a downstream process are achieved.

Description

Technical Field

[0001] The invention relates to the field of water treatment, and in particular to a zero-discharge combined treatment method and device for high-salt wastewater and circulating water. Background Art

[0002] Under the background of "zero wastewater discharge", steel enterprises generally invest heavily in the construction of wastewater deep treatment and zero discharge systems. After the comprehensive wastewater of the whole plant is pre-treated for hardness removal and concentrated by multi-stage membrane, the produced water is reused in the production unit as recycled water, and the concentrated water enters the evaporation crystallization unit. In actual operation, the pre-treatment, multi-stage membrane concentration and evaporation crystallization units have long process flows and high operating costs, requiring a lot of manpower and material resources. The wastewater of the circulating water system is one of the main sources of water for the sewage treatment system, accounting for more than 60% of the comprehensive wastewater of the whole plant. The excessive amount of treated water and the long treatment process make the operating costs and production pressure of the deep treatment and evaporation crystallization units remain high.

[0003] For the reduction of sewage discharge in circulating water systems, electrochemical hardness removal technology has obvious environmental friendliness and development potential. It is currently widely used and can remove scale-forming ions (Ca 2+ Mg 2+ The conventional non-diaphragm electrochemical method can only remove temporary hardness, HCO3 - The concentration of Ca 2+ Mg 2+ The ion removal efficiency is greatly affected and it does not soften the water quality. It needs to be combined with other technologies to achieve it, such as ion exchange resin method, lime-soda ash method, etc., which all require the consumption of a large amount of reagents; the existing diaphragm electrochemical hardness removal usually uses the same water in the anode and cathode chambers, and there are problems such as incomplete removal of permanent hardness of the cathode chamber water and the need for additional alkali adjustment due to the decrease in pH of the anode chamber water.

[0004] The treatment of high-salt wastewater (mainly containing sodium chloride and sodium sulfate) produced by multi-stage membrane concentration deep treatment has become a major problem faced by steel companies. Traditional methods such as membrane separation, freezing, evaporation and crystallization consume huge amounts of energy and are costly, and the by-products sodium chloride and sodium sulfate are of low value.

[0005] In the prior art, someone has proposed a method and system for electrochemically reducing the hardness of wastewater. The pretreated wastewater is passed into an electrochemical hardness removal device for electrolysis, and then reacted with dispersed carbon dioxide to obtain hardness-removed wastewater. After solid-liquid separation, hardness-removed water is obtained. In this method, the anode and cathode chambers are the same type of wastewater, and only the permanent hardness of the anode chamber water can be removed, but not the permanent hardness of the cathode chamber water. The pH value of the anode chamber water decreases after treatment, and the pH value of the cathode chamber water may also decrease. In order to ensure that the pH of the treated mixed water meets the requirements, additional alkali needs to be added to the treated water in the cathode chamber. In the prior art, someone has also proposed a combined circulating water treatment device and process for achieving water conservation and emission reduction in the entire plant, but the electrochemical method in this scheme only removes temporary hardness, and the treatment object is only circulating water.

[0006] The patent "Microcrystal Purifier" with application number 201710260053.0 discloses a microcrystal purifier, including: a DC power supply; a cathode electrode, that is, a metal shell with a hollow shell; a plurality of microcrystal blocks placed in the metal shell with a hollow shell; an anode electrode, placed between two adjacent microcrystal blocks; the anode electrode is connected to the positive pole of the power supply, and the cathode electrode is connected to the negative pole of the power supply; a controller is connected between the DC power supply and the cathode electrode or between the DC power supply and the anode electrode, which is used to control the power on and off of the anode electrode and the cathode electrode, and is mainly used for the treatment of spray circulating cooling water of evaporative cooling equipment.

[0007] At present, there are few combined processes for using high-salt wastewater for softening and emission reduction in circulating water systems and for using circulating water systems for low-cost treatment of high-salt wastewater. Therefore, it is necessary to develop a zero-emission combined treatment method for high-salt wastewater and circulating water to achieve source emission reduction and agent reduction in the circulating water system, while achieving higher value utilization and low-cost evaporation and crystallization of high-salt wastewater. Summary of the invention

[0008] The purpose of the present invention is to solve the shortcomings of the above-mentioned background technology and provide a zero-emission combined treatment method for high-salt wastewater and circulating water, so as to achieve source emission reduction and reagent reduction in the circulating water system, while achieving higher value utilization and low-cost evaporation and crystallization of high-salt wastewater.

[0009] The technical solution of the present invention is: a zero-discharge combined treatment method for high-salinity wastewater and circulating water, comprising the following steps:

[0010] The circulating water in the water collection tank of the open cooling tower enters the cathode chamber of the diaphragm electrolyzer, and the high-salt wastewater in the high-salt wastewater tank enters the anode chamber of the diaphragm electrolyzer, and the diaphragm electrolyzer performs diaphragm electrochemical softening treatment;

[0011] The effluent from the cathode chamber of the diaphragm electrolyzer is treated with carbon dioxide micro-nano bubbles to generate precipitation, and then returned to the open cooling tower water collection tank after sedimentation treatment, and the effluent from the anode chamber is returned to the high-salt wastewater pool;

[0012] Real-time monitoring of the circulating water quality in the open cooling tower collection tank and the high-salt wastewater quality in the high-salt wastewater pool. When the water quality of the circulating water and high-salt wastewater meets the discharge conditions, they are discharged into the closed cooling tower collection tank as spray circulating water replenishment for the closed cooling tower;

[0013] The nano-microcrystalline material installed in the slow flow area of ​​the closed cooling tower water collection tank is used to perform reverse scale separation and self-softening purification on the spray circulating water. The closed cooling tower operates at the maximum concentration multiple without drainage.

[0014] The closed cooling tower sprays circulating water for evaporation and heat exchange, and the precipitated scaling particles and crystallized salt particles are deposited and discharged.

[0015] Compared with the existing diaphragm electrochemical hardness removal or traditional chemical hardness removal, the present invention has better hardness removal effect, greatly reduces the consumption of circulating water chemicals, and no longer discharges water when the circulating water is operated at the extreme concentration multiple, which greatly reduces the discharge volume, achieves "zero emission", and greatly reduces the operating cost and processing pressure of subsequent deep treatment units.

[0016] The present invention innovatively and selectively consumes specific components in high-salt wastewater to replace chemicals for hardness removal and obtain chlorine byproduct, thereby achieving relatively high-value utilization of high-salt wastewater and playing a role in reducing salt and corrosion in downstream processes; the high-salt wastewater is evaporated and crystallized by a low-grade heat source in a closed cooling tower, which greatly reduces the energy consumption and cost of traditional evaporation and crystallization methods.

[0017] Preferably, a diaphragm is provided between the cathode chamber and the anode chamber of the diaphragm electrolyzer, and the diaphragm is a cation exchange membrane; an anode is provided in the anode chamber, and the anode material is graphite, precious metal, titanium-based metal oxide or boron-doped diamond; a cathode is provided in the cathode chamber, and the cathode material is stainless steel or carbon steel.

[0018] Preferably, the electrochemical softening treatment uses a DC voltage of 10 to 50 V and a current of 5 to 40 A; during the electrochemical softening treatment, hydrogen is recovered above the cathode chamber, and chlorine is recovered above the anode chamber.

[0019] Preferably, the original high-salinity wastewater has a pH of 6-9, a TDS of ≥120,000 mg / L, a conductivity of ≥160,000 us / cm, and a Cl - ≥30000mg / L, SO4 2- ≥20000mg / L, COD≤500mg / L, total hardness≤100mg / L. The molar number of sodium chloride contained in the anode chamber is 2 to 2.4 times the sum of the molar numbers of calcium and magnesium ions of the permanent hardness in the corresponding treated cathode chamber circulating water, which is used to ensure the removal of the permanent hardness of magnesium in the cathode chamber circulating water and to ensure that there are enough hydroxide ions to work together with the carbon dioxide in the carbon dioxide micro-nano bubble treatment to remove the permanent hardness of calcium.

[0020] Preferably, the carbon dioxide micro-nano bubble treatment includes: the cathode chamber effluent enters the micro-nano bubble generating device and the micro-nano bubble releasing device, and fully reacts with the micro-nano bubble carbon dioxide to generate calcium carbonate precipitation, the diameter of the carbon dioxide micro-nano bubble is 50nm-50μm, and the suspension time in water is ≥250s. The carbon dioxide introduction amount should meet the following requirements: the molar number of carbon dioxide is 1.2-1.6 times the sum of the molar number of permanent hardness calcium in the cathode chamber circulating water and the molar number of calcium in the high-salt wastewater, so as to ensure the removal of the permanent hardness of calcium in the cathode chamber circulating water.

[0021] The source of carbon dioxide in the carbon dioxide micro-nano bubble treatment is obtained by absorbing and collecting carbon dioxide in industrial flue gas, which is stored in a carbon dioxide storage tank and used to provide carbon dioxide to the micro-nano bubble generating device. The micro-nano bubble generating device can generate micro-nano bubbles using dispersed air method, dissolved gas release method, ultrasonic cavitation method, etc.; a carbon dioxide recovery pipeline is provided on the top of the micro-nano bubble releasing device to recover the residual carbon dioxide that has not reacted with the cathode chamber effluent into the carbon dioxide storage tank.

[0022] Preferably, the sedimentation treatment includes: entering a sedimentation tank for flocculation and sedimentation, obtaining a supernatant as de-hardened water, the de-hardened water has a pH of 7.0 to 9.0, and the de-hardened water is returned to the open cooling tower collection tank.

[0023] Preferably, the discharge conditions of high-salinity wastewater quality include: Cl - ≤30mg / L and pH≥6. The discharge condition of circulating water quality is that it can be discharged when it does not meet the preset control indicators. The preset control indicators can be set by yourself, such as referring to the control indicator requirements in GB / T 50050-2017 "Industrial Circulating Cooling Water Treatment Design Specification" or the internal control indicator requirements of the enterprise. Preferably, the discharge condition of circulating water quality is that it can be discharged when it does not meet the preset control indicators. The preset control indicators include Cl - ≤700mg / L and 9.5≥pH≥6.8.

[0024] Preferably, the nano-microcrystalline material is the microcrystalline material disclosed in the patent "Microcrystalline Purifier" with application number 201710260053.0. The nano-microcrystalline carrier continuously releases microcrystalline elements into the water, enriches the calcium and magnesium scaling ions in the water and reacts with alkaline ions, promotes scaling nucleation, eliminates the scaling of the water quality, and adsorbs and condenses the scaling particles with the crystalline salt precipitated in the high-salt wastewater to form sand-like sub-microcrystalline particles, which are compact and lose adhesion, do not precipitate on the heat transfer surface, and are directionally deposited and gathered in the slow flow area at the bottom of the water collection tank. The components contained in the microcrystalline elements have a strong affinity for oxygen, can reduce the corrosion sensitivity of the metal surface, and have a certain corrosion inhibition function.

[0025] Preferably, the closed cooling tower spray circulating water and the hot water in the cooling tower coil are evaporated for heat exchange, and the precipitated scaling particles and crystallized salt particles are directionally deposited in the slow flow area at the bottom of the water collection tank and discharged through the bottom descaling groove.

[0026] The present invention also provides a device for the zero-discharge combined treatment method of high-salt wastewater and circulating water, characterized in that it includes an open cooling tower water collection tank, a high-salt wastewater tank, a diaphragm electrolyzer, a micro-nano bubble generating device, a micro-nano bubble releasing device, a carbon dioxide storage tank, a sedimentation tank, and a closed cooling tower water collection tank;

[0027] The diaphragm electrolyzer comprises a cathode chamber, an anode chamber and a diaphragm arranged between the cathode chamber and the anode chamber, the open cooling tower water collecting tank is connected to the cathode chamber liquid inlet, the cathode chamber liquid outlet and the carbon dioxide storage tank gas outlet are both connected to the micro-nano bubble generating device, the micro-nano bubble generating device liquid outlet is connected to the micro-nano bubble releasing device liquid inlet, the micro-nano bubble releasing device liquid outlet is connected to the sedimentation tank liquid inlet, the sedimentation tank liquid outlet is connected to the open cooling tower water collecting tank liquid inlet, and the top of the micro-nano bubble releasing device is provided with a carbon dioxide collection pipeline leading to the carbon dioxide storage tank;

[0028] The liquid outlet of the high-salt wastewater pool is connected to the liquid inlet of the anode chamber, and the liquid outlet of the anode chamber is connected to the liquid inlet of the high-salt wastewater pool;

[0029] The open cooling tower water collection pool and the high-salt wastewater pool are both equipped with water quality monitoring equipment. The open cooling tower water collection pool and the high-salt wastewater pool are also respectively provided with a water collection pool discharge pipe and a wastewater pool discharge pipe leading to the closed cooling tower water collection pool. The closed cooling tower water collection pool is provided with nano-microcrystalline material for reverse scaling and self-softening purification of the spray circulating water. The bottom of the closed cooling tower water collection pool is provided with a scale discharge groove for discharging precipitated particles.

[0030] Preferably, a hydrogen collecting device and a chlorine collecting device are respectively provided on the top of the cathode chamber and the top of the anode chamber.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] 1. Unlike the existing patented diaphragm electrochemical hardness removal, where the anode and cathode chambers are mostly filled with the same type of water, the anode and cathode chambers of this patent are filled with different types of water. The sodium ions in the high-salt wastewater in the anode chamber migrate through the membrane to provide the number of hydroxide ions required to remove all permanent hardness of the circulating water in the cathode chamber. The total hardness of the circulating water in the cathode chamber is removed more thoroughly, allowing the circulating water to operate at a higher concentration multiple, greatly reducing the amount of make-up and water discharge. The high-salt wastewater in the anode chamber itself is also softened through the migration of calcium and magnesium ions, reducing the impact on the subsequent concentration and crystallization entering the closed cooling tower.

[0033] 2. The principle of the electrochemical method of this patent is sodium hydroxide + carbon dioxide for hardness removal, but the provider of sodium ions is high-salt wastewater. High-salt wastewater is used to replace traditional softening agents, which greatly reduces agent consumption, and the generated chlorine is recovered, realizing relatively high-value utilization of high-salt wastewater.

[0034] 3. In the diaphragm electrochemical treatment, the sodium chloride component in the high-salt wastewater is innovatively selectively consumed, and the sodium sulfate component is retained, so that the pH of the cathode chamber water does not decrease after treatment, and no alkali adjustment is required. At the same time, it plays a role in reducing salt at the source. After the high-salt wastewater consumes the chloride ions, it enters the closed cooling tower for concentration and crystallization, which can reduce corrosion to the closed cooling tower equipment.

[0035] 4. The use of carbon dioxide micro-nano bubble technology increases the solubility and specific surface area of ​​carbon dioxide in water, with higher hardness removal efficiency, no loss of carbon dioxide, and a utilization rate of nearly 100%. The use of carbon dioxide in industrial flue gas to fix it into calcium carbonate is conducive to reducing carbon emissions and being low-carbon and environmentally friendly.

[0036] 5. The closed cooling tower uses the high-salt wastewater from the open cooling tower and electrochemical treatment as the spray circulating water replenishment. It uses the reverse scaling and corrosion inhibition function of nano-crystals to directionally aggregate scaling particles and crystallized salt particles to achieve self-softening and purification of water quality. The closed cooling tower operates at the extreme concentration multiple, no drainage is generated, and the circulating water is "zero discharge";

[0037] 6. Using closed cooling towers as low-grade heat sources to evaporate and crystallize high-salt wastewater can greatly reduce energy consumption and costs compared to traditional evaporation and crystallization. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0039] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0040] Figure 1 The zero-discharge combined treatment device for high-salt wastewater and circulating water of the present invention

[0041] Among them: 1. Open cooling tower water collection tank; 2. High-salt wastewater tank; 3. Diaphragm electrolyzer; 31. Cathode chamber; 32. Anode chamber; 4. Cathode; 5. Anode; 6. Diaphragm; 7. Hydrogen collection device; 8. Chlorine collection device; 9. Micro-nano bubble generating device; 10. Micro-nano bubble releasing device; 11. Carbon dioxide storage tank; 12. Carbon dioxide collection pipeline; 13. Sedimentation tank; 14. Closed cooling tower water collection tank; 15. Nano-microcrystalline material; 16. Descaling tank; 17. Water collection tank discharge pipe; 18. Wastewater tank discharge pipe. DETAILED DESCRIPTION

[0042] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians of the art without making creative work belong to the scope of protection of the present application. Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application, etc., can be purchased from the market or can be prepared by existing methods.

[0043] like Figure 1 As shown, the present invention provides a zero-discharge combined treatment device for high-salt wastewater and circulating water, including an open cooling tower water collection tank 1, a high-salt wastewater tank 2, a diaphragm electrolyzer 3, a micro-nano bubble generating device 9, a micro-nano bubble releasing device 10, a carbon dioxide storage tank 11, a sedimentation tank 13, and a closed cooling tower water collection tank 14.

[0044] The diaphragm electrolyzer 3 comprises a cathode chamber 31, an anode chamber 32 and a diaphragm 6 arranged between the cathode chamber 31 and the anode chamber 32. The diaphragm 6 is a cation exchange membrane, and one or more cation exchange membranes can be provided to separate the diaphragm electrolyzer 3 into at least one cathode chamber and an anode chamber. The temporary hardness of the circulating water in the cathode chamber 31 is removed in the strong alkaline environment near the cathode. The sodium ions in the high-salt wastewater in the anode chamber 32 are enriched in the cathode chamber through the diaphragm, so that the cathode chamber obtains the hydroxide ions required to remove the permanent hardness. The high-salt wastewater in the anode chamber is partially softened as the calcium and magnesium ions migrate to the cathode chamber to form hydroxides. The diaphragm electrolyzer 3 is provided with a cathode 4 in the cathode chamber 31 and an anode 5 in the anode chamber 32. The material of the anode 5 is graphite, precious metal, titanium-based metal oxide or boron-doped diamond, and the material of the cathode 4 is stainless steel or carbon steel. When the diaphragm electrolyzer 3 is electrolyzed, the DC voltage is 10-50V and the current is 5-40A. A hydrogen collecting device 7 and a chlorine collecting device 8 are provided at the top of the cathode chamber 31 and the top of the anode chamber 32, respectively.

[0045] The open cooling tower water collecting pool 1 is connected with the liquid inlet of the cathode chamber 31, and the liquid outlet of the cathode chamber 31 and the gas outlet of the carbon dioxide storage tank 11 are both connected with the micro-nano bubble generating device 9. The micro-nano bubble generating device 9 can generate micro-nano carbon dioxide bubbles by using dispersed air method, dissolved gas release method, ultrasonic cavitation method, etc. The liquid outlet of the micro-nano bubble generating device 9 is connected with the liquid inlet of the micro-nano bubble releasing device 10, and the liquid outlet of the micro-nano bubble releasing device 10 is connected with the liquid inlet of the sedimentation tank 13, and the liquid outlet of the sedimentation tank 13 is connected with the liquid inlet of the open cooling tower water collecting pool 1. A carbon dioxide collection pipe 12 is provided on the top of the micro-nano bubble releasing device 10, which leads to the carbon dioxide storage tank 11, and the residual carbon dioxide that has not reacted with the cathode chamber water outlet is recycled into the carbon dioxide storage tank 11.

[0046] The liquid outlet of the high-salt wastewater pool 2 is connected to the liquid inlet of the anode chamber 32, and the liquid outlet of the anode chamber 32 is connected to the liquid inlet of the high-salt wastewater pool 2, so that the high-salt wastewater circulates into the anode chamber 32 for electrolysis.

[0047] The open cooling tower water collection pool 1 and the high-salt wastewater pool 2 are equipped with water quality monitoring equipment, which can monitor Cl - , pH, calcium hardness + total alkalinity and other indicators, which can be purchased according to needs. Water quality monitoring equipment is used to determine whether circulating water and high-salt wastewater meet the discharge conditions. The open cooling tower water collection pool 1 and the high-salt wastewater pool 2 are also respectively provided with a water collection pool discharge pipe 17 and a wastewater pool discharge pipe 18 leading to the closed cooling tower water collection pool 14. The closed cooling tower water collection pool 14 is provided with a nano-microcrystalline material 15 for reverse scale self-softening purification of the spray circulating water. The bottom of the closed cooling tower water collection pool 14 is provided with a scale discharge groove 16 for discharging the precipitated particles.

[0048] Nanocrystalline materials are the microcrystalline materials disclosed in the patent "Microcrystalline Purifier" with application number 201710260053.0. The nanocrystalline carrier continuously releases microcrystalline elements into the water, enriches the calcium and magnesium scaling ions in the water and reacts with alkaline ions, promotes scaling nucleation, eliminates the scaling of water quality, and adsorbs and condenses the scaling particles with the crystalline salt precipitated in the high-salt wastewater to form sand-like submicrocrystalline particles, which are compact and lose adhesion, do not precipitate on the heat transfer surface, and are directionally deposited and gathered in the slow flow area at the bottom of the water collection tank. The components contained in the microcrystalline elements have a strong affinity for oxygen, can reduce the corrosion sensitivity of the metal surface, and have a certain corrosion inhibition function.

[0049] The following uses the above device to further describe the zero-discharge combined treatment method for high-salinity wastewater and circulating water. These embodiments are only used to illustrate the present application and are not used to limit the scope of the present application. The experimental methods in the following examples that do not specify specific conditions are usually measured according to national standards. If there is no corresponding national standard, it is carried out according to the general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0050] Example 1

[0051] The circulating water for the open cooling tower is recycled water, with the following water qualities: pH 7.1, conductivity 2296us / cm, total hardness 278mg / L, Cl - 357mg / L, total alkalinity 110mg / L.

[0052] like Figure 1 As shown, a zero-discharge combined treatment method for high-salinity wastewater and circulating water in this embodiment includes the following steps:

[0053] (1) The circulating water in the open cooling tower water collection tank 1 enters the cathode chamber 31 of the diaphragm electrolytic cell 3, and the high-salt wastewater in the high-salt wastewater tank 2 enters the anode chamber 32 of the diaphragm electrolytic cell 3. The diaphragm electrolytic cell 3 continuously electrolyzes to perform diaphragm electrochemical softening treatment;

[0054] In this embodiment, the specific electrolysis DC voltage is 10V, the current is 5A, the pH of the original high-salinity wastewater is 7.0, the TDS is 120000mg / L, the conductivity is 200000us / cm, and the Cl - 30000mg / L, SO4 2- 20000mg / L, COD 500mg / L, total hardness 100mg / L, the molar number of sodium chloride contained in the anode chamber is twice the sum of the molar numbers of calcium and magnesium ions of the permanent hardness in the corresponding treated cathode chamber circulating water. During electrolysis, the cathode chamber 31 recovers hydrogen through the hydrogen collecting device 7 at the top, and the anode chamber 32 recovers chlorine through the chlorine collecting device 8 at the top.

[0055] (2) The effluent from the cathode chamber 31 is treated with carbon dioxide micro-nano bubbles to generate precipitation, and then returned to the open cooling tower water collection tank 1 after sedimentation treatment. The effluent from the anode chamber is returned to the high-salt wastewater pool 2. The water quality of the circulating water in the open cooling tower water collection tank 1 and the water quality of the high-salt wastewater in the high-salt wastewater pool 2 are monitored in real time;

[0056] The carbon dioxide micro-nano bubble treatment is specifically as follows: the cathode chamber effluent enters the micro-nano bubble generator 9 and the nano-micro bubble release device 10, and fully reacts with the micro-nano bubble carbon dioxide. The micro-nano bubble generator 9 can use the dissolved gas release method to convert the carbon dioxide provided by the carbon dioxide storage tank 11 into micro-nano bubbles. The nano-micro bubble release device 10 can recover the residual carbon dioxide to the carbon dioxide storage tank 11 through the carbon dioxide recovery pipeline 12 at the top. The diameter of the carbon dioxide micro-nano bubble is 50μm, and the suspension time in the water is 250s. Its function is to react with the hydroxide of calcium in the cathode chamber effluent to generate calcium carbonate precipitation. The molar number of carbon dioxide introduced into the micro-nano bubble generator 9 is 1.2 times the sum of the molar number of calcium in the permanent hardness of the cathode chamber circulating water and the molar number of calcium in the high-salt wastewater.

[0057] The sedimentation treatment is specifically as follows: the water from the nano-micro bubble release device 10 enters the sedimentation tank 13, undergoes flocculation and sedimentation treatment, and the supernatant is obtained as de-hardened water, the pH of the de-hardened water is 7.0, and the de-hardened water returns to the open cooling tower water collection tank 1.

[0058] (3) Real-time monitoring of the water quality of circulating water in the open cooling tower water collection tank 1 and the water quality of high-salt wastewater in the high-salt wastewater tank 2. When the water quality of the circulating water and high-salt wastewater meets the discharge conditions, they are discharged into the closed cooling tower water collection tank 14 as spray circulating water replenishment for the closed cooling tower;

[0059] The circulating water quality gradually deteriorates during the electrolysis process. Therefore, when the preset control index is not met, it can be discharged to the closed cooling tower sump 14. The preset control index can refer to the control index requirements in GB / T50050-2017 "Industrial Circulating Cooling Water Treatment Design Specification" or the internal control standard requirements of the enterprise. In this embodiment, the preset control index is obtained by referring to GB / T 50050-2017: Cl - ≤700mg / L and 9.5≥pH≥6.8, calcium hardness + total alkalinity (calculated as CaCO3) ≤1100mg / L, turbidity ≤20.0NTU and SO4 - +Cl - ≤2500mg / L. If the circulating water quality does not meet the above control indicators, it can be discharged.

[0060] The discharge conditions of high-salt wastewater are: Cl - Dropped to ≤30mg / L and pH ≥6.

[0061] The water quality of high-salt wastewater is pH: 6.8, TDS 48000mg / L, conductivity 80000us / cm, Cl - 25mg / L, SO4 2- 20000mg / L, total hardness 30mg / L. The water quality of the circulating water of the open cooling tower is: pH7.0, conductivity 9597us / cm, total hardness 60.5mg / L, Cl - 2102mg / L, total alkalinity 19.3mg / L, concentration multiple 5.9.

[0062] (4) The spray circulating water is treated with reverse scaling and self-softening purification by using the nano-microcrystalline material 15 disposed in the slow flow area of ​​the closed cooling tower water collection pool 14. After the nano-microcrystalline self-softening and scaling, the total hardness of the spray circulating water of the closed cooling tower is reduced to 12.6 mg / L. The closed cooling tower is operated at the maximum concentration multiple without drainage.

[0063] (5) The spray circulating water of the closed cooling tower exchanges heat with the hot water (i.e., the low-grade heat source) in the cooling tower coil by evaporation, and the precipitated scaling particles and crystallized salt particles are directionally deposited in the slow flow area at the bottom of the closed cooling tower sump 14 and discharged through the bottom descaling trough 16.

[0064] Example 2

[0065] The circulating water for the open cooling tower is recycled water, with the following water qualities: pH 7.1, conductivity 2296us / cm, total hardness 278mg / L, Cl - 357mg / L, total alkalinity 110mg / L.

[0066] like Figure 1 As shown, a zero-discharge combined treatment method for high-salinity wastewater and circulating water in this embodiment includes the following steps:

[0067] (1) The circulating water in the open cooling tower water collection tank 1 enters the cathode chamber 31 of the diaphragm electrolytic cell 3, and the high-salt wastewater in the high-salt wastewater tank 2 enters the anode chamber 32 of the diaphragm electrolytic cell 3. The diaphragm electrolytic cell 3 continuously electrolyzes to perform diaphragm electrochemical softening treatment;

[0068] In this embodiment, the specific electrolysis DC voltage is 30V, the current is 25A, the pH of the original high-salinity wastewater is 7.0, the TDS is 150000mg / L, the conductivity is 250000us / cm, and the Cl - 40000mg / L, SO4 2- 30000mg / L, COD500mg / L, total hardness 100mg / L, the molar number of sodium chloride contained in the anode chamber is 2.2 times the sum of the molar numbers of calcium and magnesium ions of the permanent hardness in the corresponding treated cathode chamber circulating water. During electrolysis, the cathode chamber 31 recovers hydrogen through the hydrogen collecting device 7 at the top, and the anode chamber 32 recovers chlorine through the chlorine collecting device 8 at the top.

[0069] (2) The effluent from the cathode chamber 31 is treated with carbon dioxide micro-nano bubbles to generate precipitation, and then returned to the open cooling tower water collection tank 1 after sedimentation treatment. The effluent from the anode chamber is returned to the high-salt wastewater pool 2. The water quality of the circulating water in the open cooling tower water collection tank 1 and the water quality of the high-salt wastewater in the high-salt wastewater pool 2 are monitored in real time;

[0070] The carbon dioxide micro-nano bubble treatment is specifically as follows: the cathode chamber effluent enters the micro-nano bubble generator 9 and the nano-micro bubble release device 10, and fully reacts with the micro-nano bubble carbon dioxide. The micro-nano bubble generator 9 can use the dissolved gas release method to convert the carbon dioxide provided by the carbon dioxide storage tank 11 into micro-nano bubbles. The nano-micro bubble release device 10 can recover the residual carbon dioxide to the carbon dioxide storage tank 11 through the carbon dioxide recovery pipeline 12 at the top. The diameter of the carbon dioxide micro-nano bubble is 1.5 μm, and the suspension time in the water is 350 s. Its function is to react with the hydroxide of calcium in the cathode chamber effluent to generate calcium carbonate precipitation. The molar number of carbon dioxide introduced into the micro-nano bubble generator 9 is 1.4 times the sum of the molar number of calcium in the permanent hardness of the cathode chamber circulating water and the molar number of calcium in the high-salt wastewater.

[0071] The sedimentation treatment is specifically as follows: the water from the nano-micro bubble release device 10 enters the sedimentation tank 13, undergoes flocculation and sedimentation treatment, and the supernatant is obtained as de-hardened water, the pH of the de-hardened water is 7.0, and the de-hardened water returns to the open cooling tower water collection tank 1.

[0072] (3) Real-time monitoring of the water quality of circulating water in the open cooling tower water collection tank 1 and the water quality of high-salt wastewater in the high-salt wastewater tank 2. When the water quality of the circulating water and high-salt wastewater meets the discharge conditions, they are discharged into the closed cooling tower water collection tank 14 as spray circulating water replenishment for the closed cooling tower;

[0073] The circulating water quality gradually deteriorates during the electrolysis process. Therefore, when the preset control index is not met, it can be discharged to the closed cooling tower sump 14. The preset control index can refer to the control index requirements in GB / T50050-2017 "Industrial Circulating Cooling Water Treatment Design Specification" or the internal control standard requirements of the enterprise. In this embodiment, the preset control index is obtained by referring to GB / T 50050-2017: Cl - ≤700mg / L and 9.5≥pH≥6.8, calcium hardness + total alkalinity (calculated as CaCO3) ≤1100mg / L, turbidity ≤20.0NTU and SO4 - +Cl - ≤2500mg / L. If the circulating water quality does not meet the above control indicators, it can be discharged.

[0074] The discharge conditions of high-salt wastewater are: Cl - Dropped to ≤30mg / L and pH ≥6.

[0075] The water quality of high-salt wastewater is: pH 6.7, TDS 65000mg / L, conductivity 108000us / cm, Cl - 30mg / L, SO4 2-30000mg / L, total hardness 30mg / L. The water quality of the circulating water of the open cooling tower is: pH8.0, conductivity 11916us / cm, total hardness 28.7mg / L, Cl - 2610mg / L, total alkalinity 15.6mg / L, concentration multiple 7.3.

[0076] (4) The spray circulating water is treated with reverse scaling and self-softening purification by using the nano-microcrystalline material 15 disposed in the slow flow area of ​​the closed cooling tower water collection pool 14. After the nano-microcrystalline self-softening and scaling, the total hardness of the spray circulating water of the closed cooling tower is reduced to 5.7 mg / L. The closed cooling tower is operated at the maximum concentration multiple without drainage.

[0077] (5) The spray circulating water of the closed cooling tower exchanges heat with the hot water (i.e., the low-grade heat source) in the cooling tower coil by evaporation, and the precipitated scaling particles and crystallized salt particles are directionally deposited in the slow flow area at the bottom of the closed cooling tower sump 14 and discharged through the bottom descaling trough 16.

[0078] Example 3

[0079] The circulating water for the open cooling tower is recycled water, with the following water qualities: pH 7.1, conductivity 2296us / cm, total hardness 278mg / L, Cl - 357mg / L, total alkalinity 110mg / L.

[0080] like Figure 1 As shown, a zero-discharge combined treatment method for high-salinity wastewater and circulating water in this embodiment includes the following steps:

[0081] (1) The circulating water in the open cooling tower water collection tank 1 enters the cathode chamber 31 of the diaphragm electrolytic cell 3, and the high-salt wastewater in the high-salt wastewater tank 2 enters the anode chamber 32 of the diaphragm electrolytic cell 3. The diaphragm electrolytic cell 3 continuously electrolyzes to perform diaphragm electrochemical softening treatment;

[0082] In this embodiment, the specific electrolysis DC voltage is 50V, the current is 40A, the pH of the original high-salinity wastewater is 7.0, the TDS is 180000mg / L, the conductivity is 300000us / cm, and the Cl - 50000mg / L, SO4 2- 40000mg / L, COD500mg / L, total hardness 100mg / L, the molar number of sodium chloride contained in the anode chamber is 2.4 times the sum of the molar numbers of calcium and magnesium ions of the permanent hardness in the corresponding treated cathode chamber circulating water. During electrolysis, the cathode chamber 31 recovers hydrogen through the hydrogen collecting device 7 at the top, and the anode chamber 32 recovers chlorine through the chlorine collecting device 8 at the top.

[0083] (2) The effluent from the cathode chamber 31 is treated with carbon dioxide micro-nano bubbles to generate precipitation, and then returned to the open cooling tower water collection tank 1 after sedimentation treatment. The effluent from the anode chamber is returned to the high-salt wastewater pool 2. The water quality of the circulating water in the open cooling tower water collection tank 1 and the water quality of the high-salt wastewater in the high-salt wastewater pool 2 are monitored in real time;

[0084] The carbon dioxide micro-nano bubble treatment is specifically as follows: the cathode chamber effluent enters the micro-nano bubble generator 9 and the nano-micro bubble release device 10, and fully reacts with the micro-nano bubble carbon dioxide. The micro-nano bubble generator 9 can use the dissolved gas release method to convert the carbon dioxide provided by the carbon dioxide storage tank 11 into micro-nano bubbles. The nano-micro bubble release device 10 can recover the residual carbon dioxide to the carbon dioxide storage tank 11 through the carbon dioxide recovery pipeline 12 at the top. The diameter of the carbon dioxide micro-nano bubble is 50nm, and the suspension time in the water is 450s. Its function is to react with the hydroxide of calcium in the cathode chamber effluent to generate calcium carbonate precipitation. The molar number of carbon dioxide introduced into the micro-nano bubble generator 9 is 1.4 times the sum of the molar number of calcium in the permanent hardness of the cathode chamber circulating water and the molar number of calcium in the high-salt wastewater.

[0085] The sedimentation treatment is specifically as follows: the water from the nano-micro bubble release device 10 enters the sedimentation tank 13, undergoes flocculation and sedimentation treatment, and the supernatant is obtained as de-hardened water, the pH of the de-hardened water is 7.0, and the de-hardened water returns to the open cooling tower water collection tank 1.

[0086] (3) Real-time monitoring of the water quality of circulating water in the open cooling tower water collection tank 1 and the water quality of high-salt wastewater in the high-salt wastewater tank 2. When the water quality of the circulating water and high-salt wastewater meets the discharge conditions, they are discharged into the closed cooling tower water collection tank 14 as spray circulating water replenishment for the closed cooling tower;

[0087] The circulating water quality gradually deteriorates during the electrolysis process. Therefore, when the preset control index is not met, it can be discharged to the closed cooling tower sump 14. The preset control index can refer to the control index requirements in GB / T50050-2017 "Industrial Circulating Cooling Water Treatment Design Specification" or the internal control standard requirements of the enterprise. In this embodiment, the preset control index is obtained by referring to GB / T 50050-2017: Cl - ≤700mg / L and 9.5≥pH≥6.8, calcium hardness + total alkalinity (calculated as CaCO3) ≤1100mg / L, turbidity ≤20.0NTU and SO4 - +Cl - ≤2500mg / L. If the circulating water quality does not meet the above control indicators, it can be discharged.

[0088] The discharge conditions of high-salt wastewater are: Cl - Dropped to ≤30mg / L and pH ≥6.

[0089] The water quality of high-salt wastewater is: pH 6.6, TDS 80000mg / L, conductivity 133000us / cm, Cl - 30mg / L, SO4 2- 40000mg / L, total hardness 30mg / L. The water quality of the circulating water of the open cooling tower is: pH9.0, conductivity 11291us / cm, total hardness 26.1mg / L, Cl - 2473mg / L, total alkalinity 120mg / L, concentration multiple 7.0.

[0090] (4) The spray circulating water is treated with reverse scaling and self-softening purification by using the nano-microcrystalline material 15 disposed in the slow flow area of ​​the closed cooling tower water collection pool 14. After the nano-microcrystalline self-softening and scaling, the total hardness of the spray circulating water of the closed cooling tower is reduced to 5.2 mg / L. The closed cooling tower is operated at the maximum concentration multiple without drainage.

[0091] (5) The spray circulating water of the closed cooling tower exchanges heat with the hot water (i.e., the low-grade heat source) in the cooling tower coil by evaporation, and the precipitated scaling particles and crystallized salt particles are directionally deposited in the slow flow area at the bottom of the closed cooling tower sump 14 and discharged through the bottom descaling trough 16.

[0092] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A zero-discharge combined treatment method for high-salinity wastewater and circulating water, characterized in that: The following steps are involved: The circulating water in the water collection tank of the open cooling tower enters the cathode chamber of the diaphragm electrolyzer, and the high-salt wastewater in the high-salt wastewater tank enters the anode chamber of the diaphragm electrolyzer, and the diaphragm electrolyzer performs diaphragm electrochemical softening treatment; The effluent from the cathode chamber of the diaphragm electrolyzer is treated with carbon dioxide micro-nano bubbles to generate precipitation, and then returned to the open cooling tower water collection tank after sedimentation treatment, and the effluent from the anode chamber is returned to the high-salt wastewater pool; Real-time monitoring of the circulating water quality in the open cooling tower collection tank and the high-salt wastewater quality in the high-salt wastewater pool. When the water quality of the circulating water and high-salt wastewater meets the discharge conditions, they are discharged into the closed cooling tower collection tank as spray circulating water replenishment for the closed cooling tower; The nano-microcrystalline material installed in the slow flow area of ​​the closed cooling tower water collection tank is used to perform reverse scale separation and self-softening purification on the spray circulating water. The closed cooling tower operates at the maximum concentration multiple without drainage. The closed cooling tower sprays circulating water for evaporation and heat exchange, and the precipitated scaling particles and crystallized salt particles are deposited and discharged.

2. The zero-discharge combined treatment method for high-salinity wastewater and circulating water according to claim 1, characterized in that: A diaphragm is arranged between the cathode chamber and the anode chamber of the diaphragm electrolyzer, and the diaphragm is a cation exchange membrane; an anode is arranged in the anode chamber, and the anode material is graphite, precious metal, titanium-based metal oxide or boron-doped diamond; a cathode is arranged in the cathode chamber, and the cathode material is stainless steel or carbon steel.

3. The zero-discharge combined treatment method for high-salinity wastewater and circulating water according to claim 1, characterized in that: The electrochemical softening treatment uses a DC voltage of 10 to 50 V and a current of 5 to 40 A. During the electrochemical softening treatment, hydrogen is recovered above the cathode chamber, and chlorine is recovered above the anode chamber.

4. The zero-discharge combined treatment method for high-salinity wastewater and circulating water according to claim 1, characterized in that: Original high-salinity wastewater pH: 6-9, TDS ≥ 120000 mg / L, conductivity ≥ 160000 us / cm, Cl - ≥30000mg / L, SO4 2- ≥20000mg / L, COD≤500mg / L, total hardness≤100mg / L.

5. The zero-discharge combined treatment method for high-salinity wastewater and circulating water according to claim 1, characterized in that: The carbon dioxide micro-nano bubble treatment includes: the water from the cathode chamber enters the micro-nano bubble generating device and the micro-nano bubble releasing device, and fully reacts with the micro-nano bubble carbon dioxide to generate calcium carbonate precipitation. The diameter of the carbon dioxide micro-nano bubble is 50nm~50μm, and the suspension time in water is 1000s≥250s.

6. The zero-discharge combined treatment method for high-salinity wastewater and circulating water according to claim 1, characterized in that: The sedimentation treatment includes: entering the sedimentation tank for flocculation and sedimentation, and obtaining the supernatant as the de-hardened water, the pH of the de-hardened water is 7.0-9.0, and the de-hardened water returns to the open cooling tower collection tank.

7. The zero-discharge combined treatment method for high-salinity wastewater and circulating water according to claim 1, characterized in that: The discharge conditions of high-salinity wastewater quality include: Cl - ≤30mg / L and pH≥6; the circulating water can be discharged when it does not meet the preset control indicators. The preset control indicators include Cl - ≤700mg / L and 9.5≥pH≥6.

8.

8. The zero-discharge combined treatment method for high-salinity wastewater and circulating water according to claim 1, characterized in that: The spray circulating water of the closed cooling tower evaporates and exchanges heat with the hot water in the cooling tower coil. The precipitated scaling particles and crystallized salt particles are directionally deposited in the slow flow area at the bottom of the collection tank and discharged through the bottom descaling groove.

9. A device for the zero-discharge combined treatment method of high-salinity wastewater and circulating water as claimed in any one of claims 1 to 8, characterized in that: It comprises an open cooling tower water collection tank (1), a high-salt wastewater tank (2), a diaphragm electrolyzer (3), a micro-nano bubble generating device (9), a micro-nano bubble releasing device (10), a carbon dioxide storage tank (11), a sedimentation tank (13), and a closed cooling tower water collection tank (14); The diaphragm electrolyzer (3) comprises a cathode chamber (31), an anode chamber (32), and a diaphragm (6) arranged between the cathode chamber (31) and the anode chamber (32); the open cooling tower water collecting tank (1) is connected to the liquid inlet of the cathode chamber (31); the liquid outlet of the cathode chamber (31) and the gas outlet of the carbon dioxide storage tank (11) are both connected to the micro-nano bubble generating device (9); the liquid outlet of the micro-nano bubble generating device (9) is connected to the liquid inlet of the micro-nano bubble releasing device (10); the liquid outlet of the micro-nano bubble releasing device (10) is connected to the liquid inlet of the sedimentation tank (13); the liquid outlet of the sedimentation tank (13) is connected to the liquid inlet of the open cooling tower water collecting tank (1); and a carbon dioxide collecting pipe (12) is provided on the top of the micro-nano bubble releasing device (10) and leads to the carbon dioxide storage tank (11); The liquid outlet of the high-salt wastewater pool (2) is in communication with the liquid inlet of the anode chamber (32), and the liquid outlet of the anode chamber (32) is in communication with the liquid inlet of the high-salt wastewater pool (2); The open cooling tower water collection pool (1) and the high-salt wastewater pool (2) are both provided with water quality monitoring equipment. The open cooling tower water collection pool (1) and the high-salt wastewater pool (2) are also respectively provided with a water collection pool discharge pipe (17) and a wastewater pool discharge pipe (18) leading to the closed cooling tower water collection pool (14). The closed cooling tower water collection pool (14) is provided with a nano-microcrystalline material (15) for reverse scaling self-softening purification treatment of the spray circulating water. The bottom of the closed cooling tower water collection pool (14) is provided with a scale discharge groove (16) for discharging precipitated particles.

10. The device for the zero-discharge combined treatment method of high-salinity wastewater and circulating water according to claim 9, characterized in that: A hydrogen collecting device (7) and a chlorine collecting device (8) are respectively provided on the top of the cathode chamber (31) and the top of the anode chamber (32).

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