Circulating cooling water treatment method adopting internal circulation type electrochemical method

Abstract

The invention discloses a circulating cooling water treatment method based on an internal circulation type electrochemical method, which tightly combines electrochemical softening and chemical softening to realize hardness removal and sterilization integration. On one hand, the diaphragm electrolytic cell and the continuous crystallizer are combined to realize three-stage softening of circulating cooling water, so that the hardness removal efficiency is effectively improved; and the mixed flow discharged by the crystallizer partially flows back to the cathode region, so that the scale suspension growth of the cathode region is realized, the scale is prevented from growing on the cathode plate, and the adhesion of the scale body is effectively reduced. On the other hand, anode effluent enters the temporary storage tank, the hydraulic retention time is prolonged, and full sterilization and algae removal are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of circulating cooling water treatment, and in particular to a circulating cooling water treatment method using an internal circulation electrochemical method. Background Art

[0002] Cooling water is a water resource used to cool process media and process equipment in industrial production, and accounts for a large proportion of industrial water. In the past, professionals have realized that direct cooling water greatly wastes water resources and is not conducive to environmental protection and sustainable development. The water-saving effect brought by circulating cooling water is obvious, which can effectively reduce the water replenishment rate and reduce the amount of sewage discharged. Therefore, it has become a consensus among professionals in related industries to promote the use of circulating cooling water and pay attention to the corrosion and scaling problems in the circulating water system. The cooling water in the circulating water system is heated to hot water by the hot end after passing through the cooler. The hot water is basically not discharged, but is returned to the system for recycling after being cooled, thus greatly saving water. It is estimated that when the concentration of circulating water reaches 3-5 times, the amount of replenishment water can be reduced to 2%-3% of the circulating water. Therefore, the promotion and development of circulating cooling water technology is of great significance to promoting industrial water conservation and even near-zero discharge of industrial water.

[0003] Electrochemical descaling technology is a new type of circulating water treatment technology. Compared with the traditional chemical method, it can actively remove scaling factors from the circulating water, effectively increase the concentration multiple, greatly reduce the make-up water and sewage discharge, and the treatment process is green, environmentally friendly and pollution-free. Electrochemical descaling technology is mainly aimed at the scaling problem caused by the operation and management of circulating cooling water. It also has a certain effect on corrosion, algae growth and other problems. It usually uses diaphragm separation to achieve effective pH control. Diaphragm electrolysis technology is to add a conductive ion exchange membrane between the electrodes to hinder the ion exchange between the electrolytic cells. In the diaphragm electrochemical descaling technology, it can be achieved by hindering the H between the electrolytic cells. + and OH - The neutralization reaction improves the current efficiency by releasing OH - , a highly alkaline environment is created around the cathode to remove hardness and alkalinity ions, and an electro-oxidation reaction occurs in the anode area to produce oxidants and H + Inhibit the growth of bacteria and algae, and form a dense oxide film to prevent pipeline corrosion. Since ion exchange membranes are expensive and may be scratched and damage the membrane surface structure in actual applications, in the latest research, researchers tried to use cheap non-conductive membranes to replace ion exchange membranes, and also achieved good barrier effects, showing considerable potential.

[0004] According to relevant research reports, compared with traditional electrochemical descaling, the current efficiency and descaling of diaphragm electrochemical descaling technology have been greatly improved, which is conducive to promoting the industrial application of electrochemical descaling equipment. However, in practice, the operating stability of diaphragm electrochemical equipment is limited by equipment scaling. Scale will be deposited and attached on the cathode and diaphragm surface, resulting in a significant increase in the voltage of the electrolytic cell, increased energy consumption, reduced current efficiency, and reduced system processing efficiency. It is necessary to use manual or engineering means to clean the scale in time, which greatly increases the consumption of manpower and material resources. In response to this problem, Chinese patent CN113754150B discloses "a stable operation of high-hardness water electrochemical descaling system and treatment process method", which adopts the electrochemical descaling method of "diaphragm electrochemical descaling + enhanced crystallization + scale crystal separation". The alkaline water produced by the diaphragm electrolytic cell is mixed with the raw water and then descaled in the enhanced crystallization device. The alkaline softened water is partially neutralized with the anode acidic water and discharged, and the part is mixed with the raw water and then returned to the electrolytic cell for treatment. This method can alleviate the scaling problem of equipment to a certain extent and ensure the stability of electrolytic cell operation. However, the treatment process only passes through the scale-crystal separation device once, and the cathode is still prone to scaling, which reduces the life of the electrode; the mixing of cathode alkaline water and raw water will reduce the pH value of the water body, thereby affecting the hardness removal efficiency of the enhanced crystallization device. In addition, in the field of circulating cooling water treatment, the limited sterilization ability of diaphragm electrolyzers is also considered to be an important issue restricting its development, that is, the active substances and H generated by the anode electrode + The sterilization effect cannot meet the management requirements of circulating cooling water within a limited time, which affects the integration level of circulating cooling water electrochemical equipment.

[0005] It can be seen that although diaphragm electrolysis technology has certain effects on descaling, sterilization and corrosion inhibition, in actual applications, it exposes the cathode scaling, the active substances and H generated by anode electrolysis. + Problems such as limited sterilization capacity. Summary of the invention

[0006] The object of the present invention is to provide a circulating cooling water treatment method of an internal circulation electrochemical method to solve the problems raised in the above-mentioned background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: a circulating cooling water treatment method using an internal circulation electrochemical method, comprising the following steps: S1: passing circulating cooling water into a diaphragm electrolyzer for electrolysis, wherein the diaphragm electrolyzer has an anode tank and a cathode tank separated by a diaphragm, and after electrolysis, the anode tank obtains acidic water, and the cathode tank obtains alkaline water; S2: passing the alkaline water into a filter for filtering, passing the filtered alkaline water and the circulating cooling water in step S1 into a crystallizer, softening the circulating cooling water by induced crystallization technology, and obtaining crystal particles and alkaline softened water; S3: returning the mixture of the crystal particles and alkaline softened water to the cathode tank of the diaphragm electrolyzer in step S1 to enhance the processing capacity; S4: passing the acidic water in step S1 into a sterilization temporary storage tank to increase the residence time to enhance the sterilization ability; S5: The alkaline softened water in step S2 and the acidic water in step S4 are mixed and neutralized, passed into a filter for filtration and then discharged.

[0008] Preferably, in step S1, the pH value of the acidic water is in the range of 3.0-6.5, and the pH value of the alkaline water is in the range of 8.0-12.0.

[0009] Preferably, in step S2, the continuous crystallizer is an internal circulation fluidized bed reactor, and the internal circulation fluidized bed reactor does not need to add any reagents when treating the alkaline water and raw water in step S1.

[0010] Preferably, in step S2, the average particle size of the crystal particles is not less than 1 mm, and the pH range of the alkaline softened water is 8.0-10.0.

[0011] Preferably, in step S3, the reflux liquid flow rate is 50%-200% of the inlet water flow rate.

[0012] Compared with the prior art, the present invention has the following beneficial effects: the present invention improves the system processing efficiency by rationally configuring the solid-liquid flow inside the system to solve the problems of cathode scaling and limited sterilization capacity of anode effluent. The present invention constructs a crystallizer-like environment conducive to inducing crystallization in the cathode tank of the diaphragm electrolyzer, and utilizes the OH generated by electrolysis to generate - As an alkaline agent, the mixed flow of crystal particles discharged from the crystallizer and alkaline softened water is used as a new crystal-inducing carrier, which forms a dual driving force with the electrochemical reaction of the cathode tank to synergistically degrade the hardness and alkalinity in the circulating cooling water; in the crystallizer, the filtered cathode effluent is used as an alkaline agent to soften the circulating cooling water, thereby increasing the OH content in the cathode alkaline water. - The utilization rate and processing efficiency of the system are improved, and part of the mixed flow of crystal particles and alkaline softened water in the crystallizer flows back to the cathode tank of the diaphragm electrolyzer as a new crystal-inducing carrier, closely linking electrochemical and chemical softening. On the one hand, the three-stage softening of the circulating cooling water is achieved by combining the diaphragm electrolyzer and the continuous crystallizer, effectively improving the hardness removal efficiency; the mixed flow discharged from the crystallizer is partially returned to the cathode area to achieve suspended growth of scale in the cathode area, avoiding scale growth on the cathode plate, and effectively reducing scale adhesion. On the other hand, the anode effluent enters the temporary storage tank to increase the hydraulic retention time and fully sterilize and kill algae. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the structure of the present invention.

[0014] Figure 2 This is the water quality data diagram of the circulating cooling water to be treated.

[0015] Figure 3 This is a data chart of electrochemical softened water.

[0016] Figure 4 Secondary electrochemical softened water data chart In the figure: 1 diaphragm electrolytic cell, 2 filtering device 1, 3 sterilization temporary storage device, 4 continuous crystallizer, 5 neutralization tank, 6 filtering device 2. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Cooling water is a water resource used to cool process media and process equipment in industrial production, and accounts for a large proportion of industrial water. In the past, professionals have realized that direct cooling water greatly wastes water resources and is not conducive to environmental protection and sustainable development. The water-saving effect brought by circulating cooling water is obvious, which can effectively reduce the water replenishment rate and reduce the amount of sewage discharged. Therefore, it has become a consensus among professionals in related industries to promote the use of circulating cooling water and pay attention to the corrosion and scaling problems in the circulating water system. The cooling water in the circulating water system is heated to hot water by the hot end after passing through the cooler. The hot water is basically not discharged, but is returned to the system for recycling after being cooled, thus greatly saving water. It is estimated that when the concentration of circulating water reaches 3-5 times, the amount of replenishment water can be reduced to 2%-3% of the circulating water. Therefore, the promotion and development of circulating cooling water technology is of great significance to promoting industrial water conservation and even near-zero discharge of industrial water.

[0019] Electrochemical water treatment technology is a new circulating cooling water treatment technology. Compared with the chemical method, it can effectively increase the concentration multiple and reduce water replenishment and sewage discharge. Although this method has certain effects on the descaling, sterilization and corrosion inhibition required for the stability of circulating cooling water quality, it exposes problems such as cathode scaling and limited sterilization capacity of anode effluent.

[0020] To this end, in response to the technical problems of equipment scaling and limited sterilization ability in the electrochemical method, the present invention provides a method for treating circulating cooling water that can achieve multi-stage softening and reduce scale adhesion, enhance the anode sterilization ability, and has low operating costs and easy management and maintenance. The method has high economic, social and environmental benefits, as well as good application prospects.

[0021] See also Figure 1 The present invention provides a technical solution: a circulating cooling water treatment method using an internal circulation electrochemical method, comprising the following steps: S1, passing circulating cooling water into a diaphragm electrolyzer for electrolysis, wherein the diaphragm electrolyzer has an anode tank and a cathode tank separated by a diaphragm, and after electrolysis, the anode tank obtains acidic water, and the cathode tank obtains alkaline water; S2: passing the alkaline water into a filter for filtering, passing the filtered alkaline water and the circulating cooling water in step S1 into a crystallizer, softening the circulating cooling water by induced crystallization technology, and obtaining crystal particles and alkaline softened water; S3: returning the mixture of the crystal particles and alkaline softened water to the cathode tank of the diaphragm electrolyzer in step S1 to enhance the processing capacity; S4: passing the acidic water in step S1 into a sterilization temporary storage tank to increase the residence time to enhance the sterilization ability; S5: The alkaline softened water in step S2 and the acidic water in step S4 are mixed and neutralized, passed into a filter for filtration and then discharged.

[0022] In step S1, the pH value of the acidic water is in the range of 3.0-6.5, and the pH value of the alkaline water is in the range of 8.0-12.0.

[0023] The diaphragm electrolyzer uses a diaphragm with a barrier function to divide the electrolyzer into an anode cell and a cathode cell. During the electrolysis process, the diaphragm material has a certain ion selective permeability, that is, it only allows certain specific ions to pass through, while preventing other ions or molecules from passing through. For example, some diaphragms only allow hydrogen ions (H + ) or hydroxide ion (OH - ) through, while preventing other ions or molecules from passing through. This ensures that the ion concentrations in the cathode and anode regions remain stable during electrolysis, avoiding material exchange. In the present invention, a diaphragm electrolyzer is used to electrolyze water in the anode and cathode regions to generate hydrogen ions (H + ) and hydroxide ions (OH - ). In the anode tank, other anions in the water molecules will lose electrons and undergo an oxidation reaction. Due to the high concentration of hydrogen ions in the water, the water in the anode tank is acidic. In the cathode tank, hydrogen ions will gain electrons and undergo a reduction reaction to produce hydroxide ions, and the water in the cathode tank is alkaline. Therefore, by using a diaphragm electrolytic cell to electrolyze circulating cooling water, the separation of acidic water and alkaline water is achieved, so that acidic water and alkaline water can be treated differently later.

[0024] In step S2, the diameter of the crystal particles is not less than 1 mm, and the pH range of the alkaline softened water is 8.0-11.0; The hardness of water mainly refers to the concentration of calcium and magnesium ions dissolved in water, while the alkalinity of water refers to the total amount of substances in water that can neutralize acids. During the electrochemical softening process, calcium and magnesium ions migrate to the cathode tank under the dual effects of diffusion and electric field. In the process, they react with alkalinity ions to form scale, which initially reduces the hardness of the water. However, over time, the deposition of scale will be difficult to remove, and it will reduce the current efficiency and mass transfer efficiency, making it difficult for the diaphragm electrolyzer to operate stably for a long time. The formation of scale, that is, the process in which calcium and magnesium ions in water combine with alkalinity to precipitate from the solution, is a crystallization process. It is generally believed that crystal formation and precipitation go through two stages, namely the generation of crystal nuclei and the growth of crystals. The former is mainly controlled by thermodynamic conditions, and the latter is mainly controlled by kinetic conditions. Based on the above crystallization theory, the induced crystallization softening technology first loads a certain amount of seed crystals into the reactor, and at the same time adds alkaline agents to react with calcium and magnesium ions to produce crystal products. The crystal products are then attached to the surface of the seed crystals and gradually grow as the system continues to operate. Finally, when the seed crystals grow to a certain size, they are discharged from the reactor and a portion of new seed crystals are added. Relevant studies have shown that the growth of scale crystal particles is mainly affected by multiple factors such as pH, supersaturation, seed crystal size, and flow rate. The continuous crystallizer is an internal circulation fluidized bed reactor, which is a multiphase flow reactor with the advantages of simple structure, good mixing and mass transfer performance, easy operation and maintenance, and low energy consumption per unit volume.

[0025] In step S3, the reflux flow rate is 50%-200% of the inlet flow rate; The formation of scale is a crystal nucleation and growth process. There are two nucleation modes: heterogeneous nucleation and homogeneous nucleation. Nucleation on the surface of the electrode or equipment is heterogeneous nucleation, and nucleation in the solution is homogeneous nucleation. In the conventional electrochemical softening process, because the cathode electrode surface produces OH - The first place, therefore, the supersaturated environment near the cathode surface makes heterogeneous nucleation dominant, which is not conducive to the continuous operation of the electrode. The conventional crystallizer is a device that converts solutes in the solution into crystal particles, which can help the alkaline water crystals to nucleate on the surface of the loaded seed crystals through induced crystallization technology. Therefore, the present invention uses the mature crystal particles produced by the continuous crystallizer as new seed crystals, which can effectively avoid scale deposition, achieve rapid solid-liquid separation, further reduce the hardness and alkalinity of water, improve the system processing efficiency, and avoid affecting the stable operation of the system due to scale deposition.

[0026] In step S4, the acidic water residence time is not less than 10 min; Common microorganisms in circulating cooling water systems include bacteria, algae, fungi and insects. The main hazards to the system include adhesion and corrosion, and will also aggravate the fouling and corrosion of other non-microorganisms. In the chemical method, the agent that controls the growth of microorganisms is called a bactericide, which has both bactericidal and bacteriostatic effects. The bactericidal effect is generally manifested as the inability of cells to divide, the destruction of life activities, and a direct reduction in the number of microorganisms; the bacteriostatic effect is generally manifested as the difficulty of normal life activities of microorganisms to continue, and the number of microorganisms has not increased significantly. The bactericidal or bacteriostatic effect of the chemical method is mainly related to the nature of the agent, the concentration used, pH, temperature and duration of action. The bactericidal effect of electrochemical circulating water treatment technology is generally considered to be the H generated by electrolysis. + The method provided by the present invention realizes the step-by-step softening of the cathode effluent, and accordingly increases the residence time of the anode effluent, which can effectively improve the bactericidal capacity of the anode effluent.

[0027] In summary, the present invention provides a circulating cooling water treatment method of an internal circulation electrochemical method, which aims to improve the system treatment efficiency by rationally configuring the solid-liquid flow inside the system in order to solve the problems of cathode scaling and limited sterilization capacity of anode effluent. The present invention constructs a crystallizer-like environment conducive to inducing crystallization in the cathode tank of the diaphragm electrolyzer, and utilizes the OH generated by electrolysis to generate a - As an alkaline agent, the mixed flow of crystal particles discharged from the crystallizer and alkaline softened water is used as a new crystal-inducing carrier, which forms a dual driving force with the electrochemical reaction of the cathode tank to synergistically degrade the hardness and alkalinity in the circulating cooling water; in the crystallizer, the filtered cathode effluent is used as an alkaline agent to soften the circulating cooling water, thereby increasing the OH content in the cathode alkaline water. - The utilization rate and processing efficiency of the system are improved, and part of the mixed flow of crystal particles and alkaline softened water in the crystallizer flows back to the cathode tank of the diaphragm electrolyzer as a new crystal-inducing carrier, closely linking electrochemical and chemical softening. On the one hand, the three-stage softening of the circulating cooling water is achieved by combining the diaphragm electrolyzer and the continuous crystallizer, effectively improving the hardness removal efficiency; the mixed flow discharged from the crystallizer is partially returned to the cathode area to achieve suspended growth of scale in the cathode area, avoiding scale growth on the cathode plate, and effectively reducing scale adhesion. On the other hand, the anode effluent enters the temporary storage tank to increase the hydraulic retention time and fully sterilize and kill algae. Example

[0028] The circulating cooling water is pumped into the diaphragm electrolyzer 1. Under the electrolysis of the diaphragm electrolyzer 1, the circulating cooling water generates acidic water and alkaline water in the anode tank and cathode tank respectively. The acidic water is passed into the sterilization temporary storage tank 3 to extend the residence time to improve the sterilization ability. On the other hand, the alkaline water is passed into the filter device 2 to achieve solid-liquid separation, and then the filtered alkaline water is used as an alkaline agent to soften the circulating cooling water in the crystallization device of the continuous crystallizer 4. After the reaction, scale crystal particles and water are formed, which reduces the hardness and alkalinity of the water. The scale crystal particles are discharged from the bottom and partially returned to the cathode chamber of the diaphragm electrolyzer 1. Finally, the treated water and the anode outlet water in the sterilization temporary storage 4 are passed into the neutralization tank 5 for mixing and neutralization, and the outlet water is passed into the filter device 2 6 for filtration and then discharged. Example

[0029] The water quality data of the circulating cooling water to be treated is as follows: Figure 2 As shown, The steps of removing hardness and alkali from the above-mentioned circulating cooling water to be treated are as follows: When the water flow rate is 10.0m 3 / h, the circulating cooling water to be treated is passed into the diaphragm electrolyzer 1 for electrolysis. The DC power supply voltage used by the diaphragm electrolyzer 1 is 9.0 V. The diaphragm in the diaphragm electrolyzer 1 divides the electrolyzer into an anode tank and a cathode tank. After electrolysis, the pH range of the anode tank outlet water reaches 3.0-6.5, and the pH range of the cathode tank outlet water reaches 9.0-12.0. When the anode tank outlet water flow rate is 5.0 m 3 / h, the effluent from the anode tank is passed into the sterilization temporary storage tank 3 to enhance the sterilization ability, and the active substances and H generated by electrolysis are + The sterilization rate is greater than 50% within a residence time of not less than 10 minutes.

[0030] In the cathode tank, water is electrolyzed to produce OH - The pH value rises, and the alkalinity ions and hardness ions in the water nucleate and form scale on the surface of the seed crystal under the high pH environment. After electrolysis treatment, the total hardness removal rate reaches 80%. In order to avoid scale deposition on the electrode and further soften the circulating cooling water, the water flow rate of the cathode tank is 5 m 3 / h, the cathode tank effluent was filtered and passed into the continuous crystallizer 4, and softened by induced crystallization technology with a flow rate of 5 m 3 / h circulating cooling water. After the reaction in the continuous crystallizer 4, the pH value of the effluent reached 10, the hardness removal rate reached 70%, the alkalinity removal rate reached 50%, and the average particle size of the crystal particles at the bottom of the continuous crystallizer 4 was greater than 1 mm. At the same time, the mixed flow of crystal particles discharged from the bottom of the continuous crystallizer 4 was discharged at a rate of 5 m 3 / h part flows back to the cathode tank of the diaphragm electrolyzer 1 to enhance the processing capacity. The softened water and the anode effluent from the sterilization temporary storage 3 are mixed and neutralized, and then passed into the filtering device 2 6 for filtration and then discharged.

[0031] It is worth noting that different flow rates of water entering the continuous crystallizer 4 will affect the removal effect of the reaction. When the flow rate is too fast, most of the calcium and magnesium ions will flow out with the water without homogeneous nucleation and growth. When the flow rate is too slow, the removal efficiency will also be greatly reduced due to the decrease in flow rate. Therefore, the appropriate flow rate should be selected according to the actual application.

[0032] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A circulating cooling water treatment method using an internal circulation electrochemical method, characterized in that: It includes the following steps: S1: passing circulating cooling water into a diaphragm electrolyzer for electrolysis, wherein the diaphragm electrolyzer has an anode tank and a cathode tank separated by a diaphragm, and after electrolysis, the anode tank obtains acidic water, and the cathode tank obtains alkaline water; S2: passing the alkaline water into a filter for filtering, passing the filtered alkaline water and the circulating cooling water in step S1 into a crystallizer, softening the circulating cooling water by induced crystallization technology, and obtaining crystal particles and alkaline softened water; S3: returning the mixture of the crystal particles and alkaline softened water to the cathode tank of the diaphragm electrolyzer in step S1 to enhance the processing capacity; S4: passing the acidic water in step S1 into a sterilization temporary storage tank to increase the residence time to enhance the sterilization ability; S5: The alkaline softened water in step S2 and the acidic water in step S4 are mixed and neutralized, passed into a filter for filtration and then discharged.

2. The method for treating circulating cooling water by an internal circulation electrochemical method according to claim 1, characterized in that: In step S1, the pH value of the acidic water is in the range of 3.0-6.5, and the pH value of the alkaline water is in the range of 8.0-12.

0.

3. The method for treating circulating cooling water by an internal circulation electrochemical method according to claim 1, characterized in that: In step S2, the continuous crystallizer is an internal circulation fluidized bed reactor. When the internal circulation fluidized bed reactor treats the alkaline water and raw water in step S1, no reagent needs to be added.

4. The method for treating circulating cooling water by an internal circulation electrochemical method according to claim 1, characterized in that: In step S2, the average particle size of the crystal particles is not less than 1 mm, and the pH range of the alkaline softened water is 8.0-10.

0.

5. The method for treating circulating cooling water by an internal circulation electrochemical method according to claim 1, characterized in that: In step S3, the reflux flow rate is 50%-200% of the inlet flow rate.

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