Diaphragm-free electrochemical softening device based on multistage microstructure anti-scaling cathode

Abstract

The invention belongs to the technical field of water treatment, and discloses an electrochemical water softening device, which consists of a cathode settling zone, an anode neutralizing zone and a scale collecting zone. Under a certain current density, micro-bubbles can be generated on the surface of the multi-stage microstructure anti-scaling cathode horizontally placed in the device, are bound by the cathode and are gradually coalesced, when the bubbles are coalesced to a certain degree, the bubbles can slip off the surface of the electrode, scale crystals generated on the surface of the cathode can be peeled off by shearing force generated in the sliding process, and the anti-scaling effect is achieved. And the peeled scale crystals are settled by gravity, are enriched in a scale collection area of the reaction device, and flow out and are collected through a valve at the lower end. Meanwhile, reaction effluent flows out from a water outlet of the anode neutralization zone, alkali liquor generated in the cathode precipitation zone flows through the anode neutralization zone under the action of fluid to be neutralized with acid liquor in the anode neutralization zone, and finally, nearly neutral water flows out of the reaction device from the water outlet. According to the device, microbubbles generated in the electrolysis process are enriched and amplified by utilizing the multistage microstructure anti-scaling electrode, and the anti-scaling function of the electrode of the electrochemical softening device in the actual water softening process is realized by utilizing shearing force generated by desorption sliding of the electrode, so that reaction termination caused by continuous scaling of a cathode is avoided. Meanwhile, according to the device, the cathode region and the anode region are physically isolated by adopting an insulating partition plate with low price, and ion mass transfer and diffusion of an alkaline region are enhanced by virtue of a synergistic effect of water flow and bubbles, so that a membrane material in a traditional electrochemical softening device is omitted, and the material cost and the maintenance complexity are remarkably reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of water treatment, and relates to a diaphragm-free electrochemical softening device based on a multi-stage microstructure anti-fouling cathode. BACKGROUND

[0002] In a reverse osmosis system, calcium and magnesium ions on the reverse osmosis concentrated water side are highly concentrated, and if not properly treated, they can easily cause serious secondary pollution. During the process of using membrane technology for deep treatment of concentrated water, high-hardness water quality can easily cause membrane pollution, leading to a decrease in water production and a decrease in desalination rate. In order to maintain system operation, it is often necessary to increase operating pressure and increase cleaning frequency, which not only significantly increases energy consumption and maintenance costs, but also irreversibly shortens the service life of the membrane element, ultimately forming a vicious cycle of rising operating costs, increasing maintenance burden and declining system stability, seriously threatening the operation reliability, safety and economy of the reverse osmosis system. In view of this problem, various water softening technologies such as chemical precipitation, ion exchange and electrochemistry have been developed. Among them, electrochemical softening technology has shown significant advantages in the field of softening water treatment because it does not require the addition of additional chemicals during the reaction process and does not produce solid waste causing secondary pollution.

[0003] The main principle of electrochemical water softening is that OH - HCO3 - is converted to CO3 2- , further combined with Ca 2+ to form CaCO3, or directly combined with Mg 2+ to form MgOH2, thereby removing hardness ions.

[0004] However, in practical applications, electrochemical water softening technology is often subject to certain limitations. In the case of heterogeneous nucleation domination, as the reaction proceeds, the cathode surface will be gradually covered by an insulating scale layer. This phenomenon will directly lead to the interruption of the electrochemical softening process, and the cathode must be frequently regenerated.

[0005] When the scale layer accumulated on the surface of the cathode reaches a certain thickness, it needs to be removed by mechanical scraping, reverse polarization or ultrasonic cleaning. Commercial electrochemical descaling equipment generally operates according to the above descaling principle, specifically, the patents with publication numbers CN222428661U, CN220393398U and CN119747267A use mechanical scraping to remove scale from the surface of the cathode plate; the patent with publication number CN219950606U uses reverse polarization to remove scale; and the patent with publication number CN222647728U uses ultrasonic cleaning to remove scale. These descaling methods not only interrupt the reaction, but also cause damage to the cathode, shortening the service life of the equipment.

[0006] The essence of the above-mentioned descaling methods all belong to passive descaling mechanism, that is, after the scale layer has been formed and covered on the cathode surface, it is removed again. Such methods do not have the self-descaling ability of the cathode surface, are easy to cause damage to the cathode material, and also interrupt the reaction, which leads to the complex operation process of the application of the electrochemical descaling technology, significantly increases the additional operation and maintenance cost, and restricts the application and promotion of the technology in a wider range of scenarios.

[0007] Currently, there are relevant literatures reporting the reinforcement of homogeneous nucleation technology, designing a reactor with a cathode-nylon mesh-anode sandwich structure, using the micro-bubbles generated by the cathode to promote the rapid diffusion of OH⁻ generated by water electrolysis to the cathode chamber, constructing a large-scale alkaline region, and promoting the scale crystals to uniformly nucleate in the solution instead of the cathode surface, so as to inhibit the cathode scaling, for example, reference literatures “Spatial and Temporal Regulation of Homogeneous Nucleation and Crystal Growth for High-flux Electrochemical Water Softening” and “Freestanding cylindrical metal-nylon mesh electrochemical modules for flexible and scalable water softening treatment”. However, the nylon mesh has limited resistance to acid, especially in the long-term continuous operation condition, the H⁺ generated in the anode region will inevitably diffuse to the interlayer interface, causing the nylon mesh to be exposed to an acidic environment for a long time. This long-term exposure will cause the nylon mesh to be corroded and irreversibly damaged, resulting in the failure of the homogeneous nucleation mechanism. Due to its limited durability, the system must be periodically interrupted during operation to replace and maintain the nylon mesh. This periodic disturbance to the continuous process makes the reactor with this structure lack practicality in the industrial scene that pursues stable operation. In order to overcome the limitations of the diaphragm material, some studies have proposed an electrochemical softening device without a diaphragm, which promotes the rapid diffusion of OH⁻ through the cooperation of water flow and bubble motion, thereby strengthening the homogeneous nucleation process, for example, “Facilitated OH⁻ diffusion via bubble motion and water flow in a novel electrochemical reactor for enhancing homogeneous nucleation of CaCO3”. Although this design can alleviate the problem of cathode scaling in the short term, the cathode surface will still gradually accumulate deposits as the operation time increases, which not only leads to an increase in energy consumption, but also threatens the stability and treatment effect of the reactor in long-term operation. SUMMARY

[0008] The application provides an electrochemical softening device, aiming at solving the problem of frequent interruption of operation for descaling due to cathode scaling in existing water softening technology. The core innovation of the device is the use of a multi-stage microstructure anti-scaling cathode. The potting glue layer on the surface of the cathode can effectively bind the micro-bubbles generated in the electrolysis process. These bound micro-bubbles continuously generate and coalesce on the surface of the cathode, forming large-sized bubbles. When the size of the coalesced bubbles increases to a critical value, they will spontaneously slip off the surface of the cathode. The local shear force generated in the bubble sliding process can effectively peel off the trace scale formed on the surface of the cathode, thereby realizing the automatic descaling of the cathode surface. For the first time, the bubble-induced self-cleaning descaling mechanism under the condition of horizontal arrangement of the cathode is applied to the field of electrochemical water treatment. This design significantly improves the anti-scaling ability of the cathode in the device during long-term continuous operation, ensuring the stability and continuity of the electrochemical softening process in actual water treatment applications. At the same time, the parallel structure of the cathode and anode in the device enables the spontaneous formation of a cathode precipitation zone, a scale collection zone and an anode neutralization zone during operation under the action of the water flow and the movement of the bubbles, without the use of expensive proton exchange membranes to separate the acid and alkali, which has significant economic benefits.

[0009] The technical scheme of the application is as follows:

[0010] A diaphragm-free electrochemical softening device based on a multi-stage microstructure anti-scaling cathode, comprising a cathode precipitation zone 1, an anode neutralization zone 2 and a scale collection zone 3, the cathode precipitation zone 1 and the anode neutralization zone 2 being located above the scale collection zone 3, the anode neutralization zone 2 being surrounded outside the cathode precipitation zone 1, and the anode neutralization zone 2 and the scale collection zone 3 being an integral structure; wherein a diaphragm 6 is arranged between the cathode precipitation zone 1 and the anode neutralization zone 2 to realize the electrical isolation and physical separation of the two; a fixed frame 7 is installed on the top of the scale collection zone 3, and the fixed frame 7 is used to support and position the multi-stage microstructure anti-scaling cathode 9 in the cathode reaction zone 1 and the anode 10 in the anode reaction zone 2, and also support the diaphragm 6;

[0011] The cathode precipitation zone 1 is the core area of softening, and a multi-stage microstructure anti-scaling cathode 9 is horizontally arranged in the cathode precipitation zone 1, and the multi-stage microstructure anti-scaling cathode 9 is installed on the fixed frame 7; the lead wire of the multi-stage microstructure anti-scaling cathode 9 is fixed on the diaphragm 6; a water inlet 4 is arranged on the top of the cathode reaction zone 1 for the introduction of the water to be treated;

[0012] The anode neutralization zone 2, in which a ring-shaped wire mesh anode 10 is horizontally arranged, the ring-shaped wire mesh anode 10 is installed on the fixed frame 7 and arranged around the multi-stage microstructure anti-scaling cathode 9; the lead wire of the ring-shaped wire mesh anode 10 is fixed on the outer wall of the diaphragm-free electrochemical softening device; a water outlet 5 is arranged on the upper part of the anode neutralization zone 2 for discharging the softened water;

[0013] The scale collection area 3 is mainly composed of a trapezoidal scale collection groove 11 and a scale discharge valve 12; wherein the trapezoidal scale collection groove 11 is provided with an inner wall surface inclined downward, and a scale discharge opening is formed at the lowest point of the trapezoidal scale collection groove 11; the scale discharge valve 12 is fixedly installed at the scale discharge opening by a threaded connection mode; during the reaction process, the water flowing through the cathode area 1 moves upward to the anode neutralization area 2 after reaching the bottom of the scale collection area 3, so that a complete treatment flow path is realized; and the precipitate generated during the reaction process is deposited in the trapezoidal scale collection groove 11 by gravity, and is collected by opening and closing the scale discharge valve 12.

[0014] The fixed frame 7 is a cross-shaped support, which is arranged at the top of the scale collection area 3, and is used for bearing the multi-stage microstructure anti-scale cathode 9 and the annular wire mesh anode 10, and realizing partition; recesses are arranged at the four end fixed positions of the fixed frame 7, and are used for embedding the partition plate 6, so as to separate the cathode precipitation area 1 and the anode neutralization area 2.

[0015] The skeleton of the multi-stage microstructure anti-scale cathode 9 is composed of a plurality of metal wire mesh layers arranged closely, and after the skeleton is filled and solidified by the pouring sealant, a cuboid matrix is obtained; the four peripheries of the cuboid matrix are completely covered by the pouring sealant, the top surface is closed by the pouring sealant after being adhered to the external lead wire by the conductive adhesive, so that all the surfaces except the bottom surface are insulated; finally, the exposed conductive bottom surface is electroplated and modified, so that a uniform micro-cone alloy array is constructed, and a multi-stage microstructure interface with high specific surface area is formed.

[0016] The pore size of the metal wire mesh ranges from 0.001 mm to 2 mm.

[0017] The metal wire mesh is an iron mesh, a copper mesh, a titanium mesh, a nickel mesh or an aluminum mesh.

[0018] The pouring sealant is an epoxy pouring sealant, a silicone pouring sealant, a polyurethane heat-conducting pouring sealant or a polyacrylate pouring sealant.

[0019] The annular wire mesh anode 10 has a ring width of 1.5 cm and a thickness of 0.1 cm.

[0020] The material of the annular wire mesh anode 10 is ruthenium iridium titanium, iron, copper, aluminum, titanium, zinc, nickel or stainless steel.

[0021] The center position of the water outlet 5 is 1 cm away from the top end of the diaphragm-free electrochemical softening device.

[0022] The thickness of the partition plate 6 is 0.2 cm.

[0023] The beneficial effects of the present application are as follows:

[0024] 1. The multi-stage microstructure anti-scale cathode used in the device is horizontally placed during the water softening process, and the shear stress generated by the surface bubble slip can effectively remove the scale crystals generated on the surface of the cathode, so that the device can be stably and durably operated.

[0025] 2. The specially designed scale collection zone at the bottom of the device of the present invention enables the effective enrichment and storage of settled sediments, and the sediments can be intermittently discharged and collected through the lower valve.

[0026] 3. The device of this invention cleverly designs a fluid path, allowing the alkaline solution generated in the cathode precipitation zone to flow naturally through the anode neutralization zone under the propulsion of the fluid. In the anode zone, the alkaline solution reacts with the acid produced by the anode, undergoing a neutralization reaction. This integrated design ensures that the treated water flowing out of the outlet reaches a near-neutral pH without the need for additional acid-base adjusters, simplifying subsequent treatment steps and reducing operating costs and the risk of secondary pollution.

[0027] 4. The device of the present invention omits the high-cost ion exchange membrane, thereby significantly reducing the initial investment and maintenance costs of the device and enhancing its economic advantages. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structural assembly of the electrochemical softening device of the present invention.

[0029] Figure 2 This is an exploded structural diagram of the electrochemical softening device of the present invention.

[0030] Figure 3 This is a cross-sectional view of the electrochemical softening device of the present invention.

[0031] Figure 4 This is a reaction flow diagram of the electrochemical softening device of the present invention.

[0032] In the diagram: 1. Cathode precipitation zone, 2. Anode neutralization zone, 3. Scale collection zone, 4. Inlet, 5. Outlet, 6. Baffle, 7. Fixing frame, 8. Support, 9. Multi-stage microstructure anti-scaling cathode, 10. Annular wire mesh anode, 11. Trapezoidal scale collection tank, 12. Scale discharge valve. Detailed Implementation

[0033] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0034] Example 1

[0035] A method for preparing a multi-level anti-scaling cathode is as follows:

[0036] 50 layers of metal wire mesh with predetermined specifications are cut and pressed into a 2 cm-thick stack by a tablet press; subsequently, vaseline release agent is coated on the inner wall of the mold and weighing paper is laid to form a double-layer release interface; then, liquid potting adhesive is injected into the mold, the metal wire mesh stack is laid horizontally on the surface of the adhesive and the potting adhesive is supplemented to completely immerse the metal wire mesh stack, and then the stack is placed in a 60℃ oven for 2 hours for curing; after curing, the stack is demolded and cut along the side direction to form a 5 mm cathode substrate; conductive glue and high-temperature waterproof glue are used to package the electrode wire to achieve complete sealing on one side; finally, the cathode substrate is used as a substrate, and a micro-cone alloy microstructure is formed on the surface thereof by electroplating process.

[0037] In combination Figures 1-3 The specific embodiment of the present application is described as follows: a central cross is fixed in the middle of the cathode reaction zone, and then the wire mesh anode, the separator, and the multi-stage microstructure anti-fouling cathode are arranged and placed on the central cross in the form from outside to inside, and the electrochemical softening device is assembled according to the content shown in Figures 1-3 .

[0038] The reverse osmosis concentrated water with a hardness of 1575 mg / L is continuously injected from the top end of the cathode precipitation zone of the reactor, the flow rate of the electrochemical reaction device is adjusted to 28 mL / min, the hydraulic retention time is 30 min, and the current density is set to 50 mA / cm 2 . After a period of treatment, the pH value of the solution in the cathode zone increases from the initial 8.3 to 11.32. As the reaction proceeds, a large amount of precipitate appears in the solution, which sinks under the action of gravity and is collected in the fouling tank. The removal rate of water hardness is 88%, and the removal effect is good. After the hardness of the effluent is stable, the reaction voltage is always stable at 4.5 V, and the weight gain of the multi-stage microstructure anti-fouling cathode is only 3.94 mg.

[0039] Comparative Example 1

[0040] The multi-stage microstructure anti-fouling cathode used in Example 1 is replaced by a metal wire mesh with the same area, and the reverse osmosis concentrated water with a hardness of 1575 mg / L is continuously injected from the top end of the cathode precipitation zone of the reactor. The flow rate of the electrochemical reaction device is adjusted to 28 mL / min, the hydraulic retention time is 30 min, and the current density is set to 50 mA / cm 2 . After a period of treatment, the pH value of the solution in the cathode zone increases from the initial 8.3 to 11.26. After the hardness of the effluent is stable, the voltage gradually increases from the initial 4.8 V to 5.1 V due to the influence of the cathode surface fouling, and the weight gain of the stainless steel mesh is 128 mg, which is 32 times the weight gain of the multi-stage microstructure anti-fouling cathode.

[0041] Comparative Example 2

[0042] After removing the separator used in Example 1, the electrochemical reactor lost the division of anode and cathode zones. Reverse osmosis concentrated water with hardness of 1575 mg / L was continuously injected from the top of the cathode precipitation zone of the reactor, and the flow rate of the electrochemical reactor was adjusted to 28 mL / min with a hydraulic retention time of 30 min, and the current density was set to 50 mA / cm 2 After a period of treatment, the pH of the solution near the cathode only increased from the initial 8.3 to 9.7, and OH - ions generated near the cathode tried to diffuse into the bulk solution, they would be quickly neutralized by H + ions generated at the anode. No obvious precipitation was generated in the solution, and the hardness removal rate was only 9%.

Claims

1. A diaphragm-free electrochemical softening device based on a multi-level microstructure anti-scaling cathode, characterized in that, The diaphragm-free electrochemical softening device includes a cathode precipitation zone (1), an anode neutralization zone (2), and a scale collection zone (3). The cathode precipitation zone (1) and the anode neutralization zone (2) are located above the scale collection zone (3). The anode neutralization zone (2) surrounds the cathode precipitation zone (1). The anode neutralization zone (2) and the scale collection zone (3) are an integral structure. A partition (6) is provided between the cathode precipitation zone (1) and the anode neutralization zone (2) to achieve electrical isolation and physical separation between the two. A fixing frame (7) is installed on the top of the scale collection zone (3). The fixing frame (7) is used to support and position the multi-level microstructure anti-scaling cathode (9) in the cathode reaction zone (1) and the anode (10) in the anode reaction zone (2), while supporting the fixing partition (6). The cathode precipitation zone (1) is the core area for softening, in which a multi-level microstructure anti-scaling cathode (9) is horizontally arranged. The multi-level microstructure anti-scaling cathode (9) is installed on a fixed frame (7). The wires of the multi-level microstructure anti-scaling cathode (9) are fixed on a partition (6). The top of the cathode reaction zone (1) is provided with an inlet (4) for introducing the water to be treated. The anode neutralization zone (2) has a horizontally arranged annular wire mesh anode (10), which is mounted on a fixed frame (7) and arranged around the multi-level microstructure anti-scaling cathode (9); the wires of the annular wire mesh anode (10) are fixed to the outer wall of the diaphragmless electrochemical softening device; the anode neutralization zone (2) has an outlet (5) at the top for discharging the softened water; The scale collection zone (3) is mainly composed of a trapezoidal scale collection tank (11) and a scale discharge valve (12); wherein, the trapezoidal scale collection tank (11) has a downward sloping inner wall surface, and a scale discharge port is provided at its lowest point; the scale discharge valve (12) is fixedly installed at the scale discharge port by a threaded connection; during the reaction, the water flowing through the cathode zone (1) reaches the bottom of the scale collection zone (3) and then flows upward into the anode neutralization zone (2), realizing a complete treatment flow path; the precipitate generated during the reaction is deposited in the trapezoidal scale collection tank (11) under the action of gravity, and is collected in a concentrated manner by opening and closing the scale discharge valve (12); The fixing frame (7) is a cross-shaped support, placed on top of the scale collection area (3), used to support the multi-level microstructure anti-scaling cathode (9) and the annular wire mesh anode (10), and to achieve partitioning; the four fixed positions of the fixing frame (7) are provided with grooves for embedding partitions (6) to separate the cathode precipitation area (1) and the anode neutralization area (2).

2. The diaphragm-free electrochemical softening device according to claim 1, characterized in that, The skeleton of the multi-level microstructure anti-fouling cathode (9) is composed of multiple layers of tightly arranged metal wire mesh. After the skeleton is filled and cured with potting compound, a cuboid substrate is obtained. The cuboid substrate is completely covered by potting compound. After the top surface is bonded to the external wire with conductive adhesive, it is sealed with potting compound to achieve insulation of all surfaces except the bottom surface. Finally, by electroplating the exposed conductive bottom surface, a uniformly distributed microcone alloy array is constructed to form a multi-level microstructure interface with a high specific surface area.

3. The diaphragm-free electrochemical softening device according to claim 1, characterized in that, The aperture range of the metal wire mesh is 0.001-2 mm.

4. The diaphragm-free electrochemical softening device according to claim 1, characterized in that, The metal wire mesh is made of iron, copper, titanium, nickel, or aluminum.

5. The diaphragm-free electrochemical softening device according to claim 1, characterized in that, The potting compound is an epoxy potting compound, a silicone potting compound, a polyurethane thermally conductive potting compound, or a polyacrylate potting compound.

6. The diaphragmless electrochemical softening device according to claim 1, characterized in that, The annular wire mesh anode (10) has a ring width of 1.5 cm and a thickness of 0.1 cm.

7. The diaphragm-free electrochemical softening device according to claim 1, characterized in that, The material of the annular wire mesh anode (10) is ruthenium-iridium-titanium, iron, copper, aluminum, titanium, zinc, nickel or stainless steel.

8. The diaphragmless electrochemical softening device according to claim 1, characterized in that, The center of the outlet (5) is 1 cm away from the top of the diaphragmless electrochemical softening device.

9. The diaphragmless electrochemical softening device according to claim 1, characterized in that, The partition (6) is 0.2 cm thick, and is insulated and has no pores.

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