Device and method for removing calcium and magnesium ions in circulating water

Abstract

The invention relates to the technical field of water treatment, in particular to a device and a method for removing calcium and magnesium ions in circulating water. The device comprises an electrolysis unit, a two-phase separation unit, a precipitation unit and an anode acid liquor collection and storage unit, the electrolysis unit comprises an electrolytic bath, a to-be-treated circulating water pump connected with the electrolytic bath, and a plurality of anodes and cathodes positioned in the electrolytic bath, the anodes and the cathodes are separated into anode chambers and cathode chambers through separation nets with holes, and to-be-treated circulating water is electrolyzed in the electrolysis unit; the anode chamber is communicated with the anode acid liquor collection and storage unit through an acid liquor extraction pump; the two-phase separation unit comprises a gas-liquid inlet, a gas outlet and a liquid outlet, the gas-liquid inlet is communicated with a cathode gas-liquid water outlet of the electrolytic cell, the gas outlet is communicated with the anode fluid, and the liquid outlet is communicated with the precipitation unit. According to the method for removing the calcium and magnesium ions in the circulating water by adopting the device, high-efficiency removal of the calcium and magnesium ions in the circulating water and low energy consumption can be taken into account.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a device and method for removing calcium and magnesium ions in circulating water. Background Art

[0002] In industrial production processes, the stable operation of circulating cooling water systems is crucial to equipment efficiency and lifespan. However, the presence of calcium and magnesium ions in water increases water hardness, leading to serious scaling problems. Especially in energy-intensive industries such as thermal power plants, where circulating water systems account for 80% to 90% of total water consumption and total discharge, scaling not only affects the equipment's heat exchange efficiency and increases energy consumption, but can also lead to pipe blockages, equipment damage, and significantly shorten equipment lifespan. Therefore, water conservation, emission reduction, and scale prevention in circulating water systems have become key research areas in the field of industrial water treatment.

[0003] Currently, the main methods commonly used in industrial circulating cooling water scale prevention include chemical, physical, and ion exchange methods. Among chemical methods, the lime-soda ash method removes calcium and magnesium ions by converting them into precipitates through chemical reactions; the boiling method exploits the solubility differences between calcium carbonate and magnesium hydroxide to achieve ion removal; and the addition of chemical inhibitors is a more common control measure. Traditional chemical inhibitors, such as 1-hydroxyethane-1,1-diphosphonic acid (HEDP) and aminotrimethylenephosphonic acid (ATMP), offer advantages such as low dosage and high scale inhibition effectiveness. However, as organophosphorus compounds, they are difficult to degrade during conventional water treatment processes and tend to accumulate in water bodies, leading to environmental problems such as heavy metal accumulation and eutrophication. Newer green scale inhibitors, such as polyaspartic acid (PASP) and polyepoxysuccinic acid (PESA), have been developed in recent years. Although they are phosphorus-free and biodegradable, they suffer from drawbacks such as long degradation times, increased biochemical oxygen demand (BOD) in wastewater, and high costs, limiting their large-scale application.

[0004] Physical scale inhibition methods, including magnetic field, electric field, and ultrasonic methods, have attracted widespread attention due to their long service life, low cost, and pollution-free nature. However, these methods are limited by their scale inhibition mechanisms and are only suitable for treating low-hardness water. With higher water hardness, the scale inhibition effect decreases sharply. While combining multiple physical methods can improve effectiveness, it significantly increases investment costs, making it difficult to meet the actual needs of industrial circulating cooling water systems.

[0005] In summary, existing industrial circulating cooling water scale prevention technologies may pose environmental pollution risks, be limited by treatment effectiveness and cost, or be unable to meet the needs of large-scale industrial applications. While emerging electrochemical descaling technologies hold great promise, they still require optimization in terms of efficiency, energy consumption, and cost. Therefore, developing a new, cost-effective, environmentally friendly, and adaptable circulating cooling water scale prevention method suitable for waters of varying hardness is crucial for ensuring the stable operation of industrial circulating cooling water systems and achieving sustainable industrial and environmental development. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a device and method for removing calcium and magnesium ions from circulating water, which achieves the purpose of removing calcium and magnesium ions from circulating water with high efficiency and low energy consumption without using any chemicals.

[0007] In one aspect, the present invention provides a device for removing calcium and magnesium ions from circulating water, which comprises: an electrolysis unit, a two-phase separation unit, a precipitation unit, and an anodic acid collection and storage unit;

[0008] The electrolysis unit includes an electrolytic cell, a water pump for circulating water to be treated connected to the electrolytic cell, and a plurality of anodes and cathodes located in the electrolytic cell. The anodes and cathodes are separated by a porous isolation mesh to form an anode chamber and a cathode chamber. The circulating water to be treated is electrolyzed in the electrolysis unit; the anode chamber is connected to the anode acid collection and storage unit through an acid extraction pump;

[0009] The two-item separation unit includes a gas-liquid inlet, a gas outlet and a liquid outlet. The gas-liquid inlet is connected to the cathode gas-liquid outlet of the electrolytic cell, the gas outlet is connected to the anode fluid, and the liquid outlet is connected to the precipitation unit.

[0010] The electrolytic cell is provided with a power supply, which is used to power the anode and cathode in the electrolytic cell, causing an electrolytic reaction in the electrolytic cell, a hydrogen evolution reaction (HER) reaction at the cathode, and accumulation of hydroxide in the cathode liquid. The two-phase separation unit is used to separate the gas phase H2 produced by the cathode reaction and the liquid phase alkaline circulating water. The alkaline circulating water continuously accumulates in the electrolytic cell body and finally overflows from the cathode gas-liquid outlet above the electrolytic cell. The H2 is transported to the gas-liquid inlet of the two-phase separator. The gas-liquid inlet adopts a tangential inlet design so that the fluid forms a vortex after entering, and gas-liquid separation is performed by centrifugal force or gravity. The H2 separated by the two-phase separator is circulated to the water body near the anode, where a reverse reaction hydrogen oxidation reaction (HOR) occurs, which is used to suppress the oxidation and acidification of the water body near the anode. The anode produces H +After being confined in the anode boundary layer, the acid is rapidly pressed into the anode cavity under the action of the pressure difference between the inner and outer cavities of the anode to produce acid solution, which is then extracted from the bottom of the reaction tank. The precipitation unit is used to precipitate and separate the alkaline circulating water containing precipitates, remove calcium and magnesium flocculated precipitates, and achieve the purpose of removing calcium and magnesium ions in the circulating water.

[0011] Conventional circulating water electrolysis reaction mainly occurs on the anode and cathode surfaces, and the product H + and OH − Initially confined to the electrode boundary layer, it gradually diffuses into the bulk solution and is consumed in equal amounts through neutralization reactions. Neutralization reactions occurring directly in the electrolyzer release a significant amount of heat, reducing electrolysis efficiency. At the same time, the cathode region must maintain alkalinity to promote hydrogen evolution, while the anode chamber must maintain acidity to promote oxygen evolution. However, direct mixing of the acid in the anode chamber and the alkaline solution in the cathode chamber in the electrolyzer can cause pH imbalance between the anode and cathode chambers, thereby reducing catalytic efficiency.

[0012] The electrolyzer of the present invention extracts H directly from the anode boundary layer of the anode chamber. + To stop H + Transfer to the bulk solution, specifically, the circulating water to be treated is pumped into the reactor by the circulating water pump, and the solution in the anode cavity is extracted by the acid extraction pump, so a pressure difference can be generated between the anode outer cavity and the anode cavity. Under the action of the pressure difference, the H-containing liquid near the outer wall of the anode filter is + The solution can be pressed into its inner cavity, thus achieving H + Extraction from the boundary layer. The extraction of H⁺ from the boundary layer can inhibit its electromigration to the bulk solution, thereby reducing the mixing of H⁺ and OH⁻. - Since it is not with H + The pressure difference between the inner and outer chambers of the anode is achieved by regulating the flow rate of the water inlet pump and the acid extraction pump to achieve a high Reynolds number (Re), so that the flow enters a turbulent state. The porous anode system operates in turbulent mode to ensure that the H generated at the anode is + The lateral migration force is greater than the sum of the electric field force and the hydrodynamic convection caused by turbulence near the anode surface. The pressure difference generated in this process can achieve effective extraction of H⁺.

[0013] Preferably, the device for removing calcium and magnesium ions from circulating water further includes an acid-base neutralization unit;

[0014] The acid-base neutralization unit includes a cathode alkali liquid storage unit and a neutralization and recycling unit connected to the precipitation unit; the cathode alkali liquid storage unit and the anode acid liquid collection and storage unit are respectively connected to the neutralization and recycling unit.

[0015] Among them, the two-phase separation unit sends the alkaline circulating water to the precipitation separation device; the precipitation device sends the alkaline circulating water after removing the sediment to the cathode alkali liquid storage unit for storage; the regenerated reuse water unit is the neutralization reaction site of the alkaline circulating water and the acidic circulating water.

[0016] Preferably, the anode is made of ruthenium-iridium-plated titanium mesh, and the cathode is made of titanium mesh.

[0017] Preferably, the anode is arranged inside the cathode with a spacing of 1 to 10 cm.

[0018] Preferably, the isolation net is a three-layer nylon net structure, wherein the middle layer nylon net is 12500 mesh and the outer layer nylon net is 400 mesh. The three-layer nylon net structure can separate the calcium carbonate and magnesium hydroxide precipitated flocs.

[0019] Preferably, the anode, cathode, and separator mesh are all hollow cylindrical structures, with the nylon mesh interposed between the anode and cathode. The hollow cylindrical structure of the anode forms the anode chamber, while the space between the nylon mesh and cathode forms the cathode chamber. This tubular, porous structure can lower the critical Reynolds number and fluid resistance, promote mass transfer, and facilitate turbulent flow.

[0020] Preferably, the sedimentation separation device is a sedimentation tank or a membrane separation device; the sedimentation tank is one of a vertical flow sedimentation tank, a horizontal flow sedimentation tank, a radial flow sedimentation tank and an inclined tube sedimentation tank; the membrane separation device can be at least one of an ultrafiltration membrane assembly, a microfiltration assembly, and a composite membrane separation system.

[0021] Preferably, a carbon dioxide pumping device is provided on the electrolytic cell.

[0022] Further preferably, the carbon dioxide pumping device is a micro-nano bubble generator that pumps carbon dioxide into the electrolytic cell, enriching the circulating water to be treated with dissolved carbon dioxide. By adding carbon dioxide, the dissolved carbon dioxide content in the circulating water is increased, and a high content of carbonate ions is generated in the circulating water for flocculation and precipitation of calcium ions.

[0023] Preferably, the circulating water pump to be treated and the acid extraction pump are the same or different pumps, and are selected from one of a centrifugal pump, a self-priming pump, a plunger pump, a screw pump or a peristaltic pump.

[0024] Preferably, a mist collector is provided in the two-phase separator for circulating hydrogen to the anode chamber.

[0025] In one aspect, the present invention further provides a method for removing calcium and magnesium ions from circulating water using the above-mentioned device, which comprises the following steps:

[0026] Cathode hydrogen evolution: The circulating water to be treated is pumped into the electrolytic cell through the circulating water pump to be treated. The circulating water to be treated is electrolyzed, and the circulating water in the cathode chamber undergoes an electrochemical hydrogen evolution reaction to generate alkaline circulating water containing hydroxide ions and hydrogen;

[0027] Calcium and magnesium ion flocculation precipitation: In the cathode chamber, hydroxide ions react with magnesium ions to form magnesium hydroxide flocculation precipitates; hydroxide ions react with dissolved carbon dioxide in the circulating water to form carbonate ions, and carbonate ions react with calcium ions to form calcium carbonate flocculation precipitates;

[0028] Anodic oxidation: The circulating water in the anode chamber undergoes water oxidation reaction to produce acidic circulating water;

[0029] Acid-base separation: The flow rate of the circulating water pump to be treated is greater than the flow rate of the acid extraction pump, which creates a pressure difference between the inside and outside of the anode chamber. The acidic circulating water produced in the anode chamber is confined in the anode chamber and pumped into the anode acid collection and storage unit through the acid extraction pump; the alkaline circulating water and hydrogen containing sediment in the cathode chamber overflow from the cathode gas-liquid outlet of the electrolyzer and enter the gas-liquid inlet of the two separation units, thus achieving the separation of the circulating water acid and the alkaline solution containing sediment;

[0030] Gas-liquid separation: the alkaline circulating water containing sediment and hydrogen enter the gas-liquid inlet to form a cyclone, and hydrogen is separated by centrifugal force or gravity;

[0031] Inhibit the oxidation of anode circulating water: After hydrogen is separated into gas and liquid by the gas-liquid separation device, it circulates into the anode chamber and undergoes hydrogen oxidation reaction, thereby inhibiting the oxidation reaction of circulating water at the anode to produce acid and oxygen;

[0032] Deprecipitation: The alkaline circulating water produced by the cathode hydrogen evolution reaction is separated to remove the magnesium hydroxide flocculation precipitate and the calcium carbonate flocculation precipitate therein to obtain the deprecipitated alkaline circulating water.

[0033] Preferably, the flow rate of the circulating water pump to be treated is 500ML / min~1000ML / min, and the flow rate of the acid extraction pump is 50ML / min~120ML / min.

[0034] Preferably, after the deprecipitation step, an acid-base neutralization step is further included: the alkaline circulating water after the deprecipitation is mixed with the acidic circulating water in the anode acid liquid collection and storage unit to undergo a neutralization reaction until it becomes neutral, thereby obtaining regenerated circulating water.

[0035] Preferably, the mixing volume ratio of the alkaline circulating water to the acidic circulating water is (5-10):1.

[0036] Preferably, the current density of the electrolysis is 5-20 mA / cm 2, direct current with voltage ≤30V, current ≤10A, and electrolysis time 30~120min.

[0037] Preferably, carbon dioxide is introduced into the circulating water to be treated through a micro-nano bubble machine to generate circulating water to be treated rich in dissolved carbon dioxide, and the concentration of carbon dioxide in the circulating water to be treated is 1.2 g / L circulating water.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The present invention optimizes the electrochemical descaling process, designs a HER-HOR coupling system and a corresponding device for removing calcium and magnesium ions from circulating water. An electrochemical hydrogen evolution reaction (HER) occurs at the cathode. Based on the principle of water ionization equilibrium shift, hydrogen ions gain electrons to generate hydrogen gas, which promotes the forward ionization of water. A large amount of hydroxide ions accumulate at the negative electrode, significantly increasing the alkalinity of the circulating water. The increase in alkalinity promotes the conversion of bicarbonate ions into carbonate ions, which combine with calcium and magnesium ions to form precipitates such as calcium carbonate and magnesium carbonate, thereby achieving efficient capture and removal of calcium and magnesium ions.

[0040] (2) The HER-HOR coupling system relies on a simple two-electron reaction mechanism. Compared with the multi-electron reaction system, its electron transfer step is shorter and the reaction activation energy is lower. It can complete the hydroxide ion generation, hydrogen circulation and hydrogen oxidation reaction (HOR) in a short time, accelerate the alkalinity improvement process, and thus accelerate the calcium and magnesium ion precipitation reaction rate. By shortening the reaction cycle, the treatment device significantly increases the amount of circulating water treated per unit time, and the calcium and magnesium ion removal efficiency is greatly improved. The overall water treatment performance and operating efficiency of the device significantly optimize the circulating water treatment devices in the existing technology.

[0041] (3) The traditional water oxidation and acid production process consumes a large amount of electrical energy to drive the decomposition of water molecules. However, this invention innovatively reconstructs the anode reaction pathway by recycling the hydrogen produced by HER to the anode to participate in the HOR reaction. Hydrogen, as a highly active electron donor, preferentially participates in the oxidation reaction, replacing part of the water oxidation and acid production process, reducing the high energy input required for the direct decomposition of water molecules. While maintaining the dynamic balance of acid and alkali production in the system, the overall energy consumption is reduced by optimizing the electron transfer pathway and energy utilization mode, thereby improving the feasibility of practical application of this technology in the field of industrial circulating water treatment.

[0042] (4) The present invention has developed an industrial-scale, stable, and complete electrolyzer with the ability to extract H from the anode boundary layer. + This system, which uses a tubular porous titanium anode, operates in turbulent flow mode to ensure that the H generated at the anode is +The lateral migration force is greater than the sum of the electric field force and the hydrodynamic convection caused by turbulence near the anode surface to achieve H + and OH - The acid and alkali separated by the electrolytic cell can be fully utilized. During operation, the separated alkali precipitates calcium and magnesium ions in the circulating water, reducing the alkalinity of the circulating water. The H2 generated by the cathode of the electrolytic cell is connected to the anode chamber to inhibit the process of water oxidation and oxygen production, making the electrolytic cell have a faster acid-base separation efficiency.

[0043] (5) The generated acid solution is mixed with the alkaline circulating water after precipitation in a ratio of (5~10):1 until it becomes neutral, thereby realizing the regeneration and reuse of the circulating water.

[0044] (6) No external descaling agent or additional physical descaling equipment is required, achieving efficient descaling and efficient reuse of circulating water. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and, therefore, should not be regarded as limiting the scope. For those skilled in the art, other relevant drawings can be obtained based on these drawings without creative work.

[0046] Figure 1 Schematic diagram of the structure of the device for removing calcium and magnesium ions from circulating water in Example 1;

[0047] Figure 2 This is a schematic diagram of the structure of the device for removing calcium and magnesium ions from circulating water in Example 2.

[0048] Among them, 1. external power supply; 2. electrolytic cell; 3. anode; 4. cathode; 5. anode acid collection pipe; 6. wire; 7. cathode gas-liquid outlet; 8. cathode alkali storage unit; 9. anode acid storage tank; 10. circulating water inlet; 11. anode acid outlet pipe; 12. isolation net; 13. two-phase separation unit; 131. gas-liquid inlet; 132. gas outlet; 133 liquid outlet; 14. hydrogen circulation pipe; 15 circulating water pump for treatment; 16 acid extraction pump; 17. precipitation separation device 18. regeneration reuse water tank, 19. mist collector. DETAILED DESCRIPTION

[0049] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described 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 making any creative efforts are within the scope of protection of the present invention.

[0050] Refer to the attached Figure 1 As shown, the present invention provides a device for removing calcium and magnesium ions from circulating water, comprising an electrolysis unit, a two-phase separation unit, a precipitation unit, and an anode acid collection and storage unit;

[0051] The electrolysis unit includes an electrolytic cell 2, a circulating water pump 15 for treated water connected to the electrolytic cell 2 via a circulating water inlet 10, a plurality of ruthenium-plated iridium-titanium mesh anodes 3 and a titanium mesh cathode 4. The anodes 3 and cathodes 4 are separated by a porous isolation mesh 12 to form an anode chamber and a cathode chamber. The circulating water to be treated is electrolyzed in the electrolysis unit.

[0052] The anodic acid liquid collection and storage unit includes an anodic acid liquid collection pipe 5, an anodic acid liquid collection pipe outlet 11 provided on the side of the electrolytic cell, and an anodic acid liquid storage tank 9;

[0053] The lower end of the anode chamber is connected to the anode acid liquid storage tank 9 through the anode acid liquid collection pipe 5, the anode acid liquid collection pipe outlet 11, and the acid liquid extraction pump 16 in sequence;

[0054] The sedimentation unit includes a sedimentation separation device 17;

[0055] The two-phase separation unit 13 includes a gas-liquid inlet 131, a gas outlet 132 and a liquid outlet 133. The gas-liquid inlet 131 is connected to the cathode gas-liquid outlet 7 of the electrolytic cell. The gas outlet 132 is fluidically connected to the ruthenium-plated iridium-titanium mesh anode 3 through the hydrogen circulation pipe 14. The liquid outlet is connected to the precipitation separation device 17.

[0056] The external power supply 1 is electrically connected to the ruthenium-iridium-plated titanium mesh anode 3 and the titanium mesh cathode 4 through a wire 6 for electrolysis.

[0057] Refer to the attached Figure 2 As shown, the device for removing calcium and magnesium ions from circulating water also includes an acid-base neutralization unit;

[0058] The acid-base neutralization unit includes a cathode alkali liquid storage unit 8 and a neutralization and reuse unit connected to a precipitation separation device 17; the neutralization and reuse unit includes a regeneration and reuse water tank 18; the cathode alkali liquid storage unit 8 and the anode acid liquid storage tank 9 are respectively connected to the regeneration and reuse water tank 18, and the cathode alkali liquid and the anode acid liquid are mixed in the regeneration and reuse water tank 18 according to a set ratio to undergo a neutralization reaction to obtain reused circulating water.

[0059] As a preferred embodiment, the ruthenium-iridium-plated titanium mesh anode 3 is arranged in the titanium mesh cathode 4, and the isolation mesh 12 is arranged between the anode and the cathode to form an anode-cathode group. One or more anode-cathode groups are arranged in the electrolytic cell 2; the power supply is a DC power supply, the positive pole of which is connected to the anode 3 through a wire 6, and the negative pole is connected to the cathode 4 through a wire 6.

[0060] As a preferred embodiment, the ruthenium-iridium-plated titanium mesh anode 3 is nested within the titanium mesh cathode 4, with a spacing of 1 to 10 cm. Specifically, the spacing is 1 cm, 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, or a range of values therebetween.

[0061] As a preferred embodiment, the porous isolation net 12 is a three-layer nylon mesh structure, wherein the middle layer nylon mesh is 12500 mesh and the outer layer nylon mesh is 400 mesh. The three-layer nylon mesh structure can separate the calcium carbonate and magnesium hydroxide precipitated flocs.

[0062] As a preferred embodiment, the anode 3, cathode 4 and nylon mesh 12 are all hollow cylindrical structures, and the nylon mesh 12 is arranged between the anode and the cathode; an anode chamber is formed in the hollow cylindrical structure of the ruthenium-iridium-titanium mesh anode 3, and a cathode chamber is formed between the nylon mesh 12 and the titanium mesh cathode 4.

[0063] As an embodiment, the electrolytic cell 2 is cylindrical.

[0064] As an embodiment, the sedimentation separation device 17 adopts a sedimentation tank; the sedimentation tank is one of a vertical flow sedimentation tank, a horizontal flow sedimentation tank, a radial flow sedimentation tank and an inclined tube sedimentation tank.

[0065] As an embodiment, the sedimentation separation device 17 adopts a membrane separation device, and the membrane separation device is at least one of an ultrafiltration membrane component, a microfiltration component, and a composite membrane separation system.

[0066] As a preferred embodiment, the electrolytic cell is provided with a nano bubble machine for pumping carbon dioxide into the circulating water to be treated.

[0067] As a preferred embodiment, a mist collector is provided in the two-phase separator for circulating hydrogen to the anode chamber.

[0068] The method for removing calcium and magnesium ions from circulating water using the above device comprises the following steps:

[0069] Cathode hydrogen evolution: The circulating water to be treated is pumped into the electrolytic cell through the circulating water pump to be treated. The circulating water to be treated is electrolyzed, and the circulating water in the cathode chamber undergoes an electrochemical hydrogen evolution reaction to generate alkaline circulating water containing hydroxide ions and hydrogen;

[0070] Calcium and magnesium ion flocculation precipitation: Hydroxyl ions react with magnesium ions to form magnesium hydroxide flocculation precipitates; Hydroxyl ions react with dissolved carbon dioxide in the circulating water to form carbonate ions, and carbonate ions react with calcium ions to form calcium carbonate flocculation precipitates;

[0071] Anodic oxidation: The circulating water in the anode chamber undergoes water oxidation reaction to produce acidic circulating water;

[0072] Acid-base separation: The flow rate of the circulating water pump to be treated is greater than the flow rate of the acid extraction pump, which creates a pressure difference between the inside and outside of the anode chamber. The acidic circulating water produced in the anode chamber is confined in the anode chamber and pumped into the anode acid collection and storage unit through the acid extraction pump; the alkaline circulating water and hydrogen containing sediment in the cathode chamber overflow from the cathode gas-liquid outlet of the electrolyzer and enter the gas-liquid inlet of the two separation units, thus achieving the separation of the circulating water acid and the alkaline solution containing sediment;

[0073] Gas-liquid separation: the alkaline circulating water containing sediment and hydrogen enter the gas-liquid inlet to form a cyclone, and hydrogen is separated by centrifugal force or gravity;

[0074] Inhibit the oxidation of anode circulating water: After hydrogen is separated into gas and liquid by the gas-liquid separation device, it circulates into the anode chamber and undergoes hydrogen oxidation reaction, thereby inhibiting the oxidation reaction of circulating water at the anode to produce acid and oxygen;

[0075] Deprecipitation: The alkaline circulating water produced by the cathode hydrogen evolution reaction is separated to remove the magnesium hydroxide flocculation precipitate and the calcium carbonate flocculation precipitate therein to obtain the deprecipitated alkaline circulating water.

[0076] In a preferred embodiment, the flow rate of the circulating water pump to be treated is 500 ML / min~1000 ML / min, and the flow rate of the acid extraction pump is 50 ML / min~120 ML / min.

[0077] A preferred embodiment further includes an acid-base neutralization step after the deprecipitation step: the separated alkaline circulating water is mixed with the acidic circulating water produced by the anode, and a neutralization reaction is carried out to neutrality to obtain regenerated circulating water.

[0078] As a preferred embodiment, the mixing volume ratio of alkaline circulating water to acidic circulating water is (5-10):1.

[0079] As a preferred embodiment, the current density of the current is 5~20mA / cm 2 , direct current with voltage ≤30V, current ≤10A, and electrolysis time 30~120min.

[0080] As a preferred embodiment, carbon dioxide is introduced into the circulating water to be treated through a micro-nano bubble machine to generate circulating water to be treated with a carbon dioxide concentration of 1.2 g / L.

[0081] As a preferred embodiment, the circulating water to be treated contains 1~5g CaCO3 L -1 (i.e. 1-5g CaCO3 in 1L of water) Total hardness. Preferably the total hardness is 4 g CaCO3 L -1 In the water sample, Ca²⁺=0.8 g / L and Mg²⁺=0.48 g / L.

[0082] The following is a detailed review of the method for removing calcium and magnesium ions from circulating water in this embodiment through examples and comparative examples.

[0083] The following embodiments use the above device for removing calcium and magnesium ions from circulating water, wherein the anode uses a ruthenium-iridium-plated titanium mesh, the cathode uses a titanium mesh, and the isolation mesh uses a three-layer nylon mesh. The anode, cathode, and isolation mesh are all hollow cylindrical structures, the anode is sheathed in the cathode, and the isolation mesh is sheathed between the anode and the cathode; the electrode spacing in Examples 1-2 is 6 cm.

[0084] Example 1

[0085] A method for removing calcium and magnesium ions from circulating water, using Figure 1 The device shown comprises the following steps:

[0086] (1) Cathode hydrogen evolution: The treated circulating water is pumped into the electrolyzer through the treated circulating water pump at a flow rate of 400 ML / min; a current density of 5 mA / cm is passed into the treated circulating water in electrolyzer 2. 2 , a direct current of 10V and 2A is applied, and the electrolysis time is 60min; the circulating water in the cathode chamber undergoes an electrochemical hydrogen evolution reaction to generate alkaline circulating water containing hydroxide ions and hydrogen;

[0087] (2) Calcium and magnesium ion flocculation precipitation: In the cathode chamber, hydroxide ions react with magnesium ions to form magnesium hydroxide flocculation precipitates; hydroxide ions react with dissolved carbon dioxide in the circulating water to form carbonate ions, and carbonate ions react with calcium ions to form calcium carbonate flocculation precipitates;

[0088] (3) Anodic oxidation: The circulating water in the anode chamber undergoes water oxidation reaction to produce acidic circulating water;

[0089] (4) Acid-base separation: The acidic circulating water is extracted into the anode acid storage tank at a flow rate of 30 ML / min through the anode acid collection pipe and the acid extraction pump; the alkaline circulating water and hydrogen containing sediment in the cathode chamber overflow from the cathode gas-liquid outlet of the electrolytic cell and enter the gas-liquid inlet of the two separation units, thereby achieving the separation of the circulating water acid and the alkaline solution containing sediment;

[0090] (5) Gas-liquid separation: The alkaline circulating water and hydrogen containing the flocculent precipitate enter the gas-liquid inlet of the two-phase separator through the cathode gas-liquid outlet 7 and form a cyclone, and the hydrogen and alkaline circulating water are separated by centrifugal force or gravity;

[0091] (5) Inhibit the oxidation of anode circulating water: Hydrogen circulates into the ruthenium-plated iridium-titanium mesh anode chamber of the electrolytic cell, and hydrogen oxidation reaction occurs, inhibiting the oxidation of circulating water at the anode to produce acid and oxygen;

[0092] (6) Deprecipitation: The alkaline circulating water containing flocculated sediment enters the sedimentation tank, and the sediment is separated from the alkaline circulating water produced by the cathode hydrogen evolution reaction in the sedimentation tank to remove the magnesium hydroxide flocculated sediment and the calcium carbonate flocculated sediment to obtain the deprecipitated alkaline circulating water.

[0093] The initial total water hardness is 4 g / L (calculated as CaCO3), of which Ca²⁺=0.8 g / L, Mg²⁺=0.48 g / L,

[0094] After the electrolytic cell was powered on, a large amount of flocs were generated in the cathode gas-liquid effluent. EDTA titration method (GB / T15452-2009) was used for detection (the following detection methods are the same). After the floc sediment was removed, the Ca²⁺ concentration was 0.0947 g / Lg / L, and the Mg 2+ The concentration is 0.0847g / L, Ca²⁺, Mg 2+ The removal rates were 88.16% and 82.35% respectively.

[0095] Example 2

[0096] A method for removing calcium and magnesium ions from circulating water, using Figure 2 The device shown comprises the following steps:

[0097] (1) Cathode hydrogen evolution: The treated circulating water is pumped into the electrolyzer through the treated circulating water pump at a flow rate of 500 ML / min. The current density of the treated circulating water in the electrolyzer 2 is 12.5 mA / cm 2 , a direct current of 25V and 5A is applied, and the electrolysis time is 120min; the circulating water in the cathode chamber undergoes an electrochemical hydrogen evolution reaction to generate alkaline circulating water containing hydroxide ions and hydrogen;

[0098] (2) Calcium and magnesium ion flocculation precipitation: In the cathode chamber, hydroxide ions react with magnesium ions to form magnesium hydroxide flocculation precipitates; hydroxide ions react with dissolved carbon dioxide in the circulating water to form carbonate ions, and carbonate ions react with calcium ions to form calcium carbonate flocculation precipitates;

[0099] (3) Anodic oxidation: The circulating water in the anode chamber undergoes water oxidation reaction to produce acidic circulating water;

[0100] (4) Acid-base separation: The acidic circulating water is extracted into the anode acid liquid storage tank through the anode acid liquid collection pipe and the acid liquid extraction pump at a flow rate of 50ML / min; the alkaline circulating water and hydrogen containing sediment in the cathode chamber overflow from the cathode gas-liquid outlet of the electrolytic cell and enter the gas-liquid inlet of the two separation units, thereby achieving the separation of the circulating water acid and the alkaline liquid containing sediment;

[0101] (5) Gas-liquid separation: The alkaline circulating water and hydrogen containing the flocculent precipitate enter the gas-liquid inlet of the two-phase separator through the cathode gas-liquid outlet 7 and form a cyclone, and the hydrogen and alkaline circulating water are separated by centrifugal force or gravity;

[0102] (6) Inhibit the oxidation of circulating water at the anode: Hydrogen circulates into the ruthenium-plated iridium-titanium mesh anode chamber of the electrolytic cell, where hydrogen oxidation reaction occurs, inhibiting the oxidation of circulating water at the anode to produce acid and oxygen;

[0103] (7) Deprecipitation: The alkaline circulating water containing flocculated precipitates enters a sedimentation tank, where the alkaline circulating water produced by the cathode hydrogen evolution reaction is subjected to sedimentation separation, and the magnesium hydroxide flocculated precipitates and calcium carbonate flocculated precipitates therein are removed to obtain deprecipitated alkaline circulating water;

[0104] (8) Acid-base neutralization: The alkaline circulating water after precipitation is stored in the cathode alkaline liquid storage unit 8, and the alkaline circulating water therein and the acidic circulating water in the anode acid liquid storage tank 9 are mixed in the regeneration reuse water tank at a volume ratio of 5:1 to produce a neutralization reaction to obtain regenerated circulating water.

[0105] After the device was operated for a period of time under the same water inlet parameters as in Example 1, the effluent Ca 2+ The concentration dropped to 0.06 g / L, Mg 2+ The concentration dropped to 0.07 g / L.

[0106] Example 3

[0107] A method for removing calcium and magnesium ions from circulating water, using Figure 2 The device shown comprises the following steps:

[0108] (1) Cathode hydrogen evolution: The treated circulating water is pumped into the electrolytic cell through the treated circulating water pump at a flow rate of 1000 ML / min. A CO2 concentration of 1.2 mg / L is introduced into the treated circulating water in electrolytic cell 2 through a nanobubble machine, and a current density of 20 mA / cm is introduced. 2 , a direct current of 30V and 8A is applied, and the electrolysis time is 30min; the circulating water in the cathode chamber undergoes an electrochemical hydrogen evolution reaction to generate alkaline circulating water containing hydroxide ions and hydrogen;

[0109] (2) Calcium and magnesium ion flocculation precipitation: In the cathode chamber, hydroxide ions react with magnesium ions to form magnesium hydroxide flocculation precipitates; hydroxide ions react with dissolved carbon dioxide in the circulating water to form carbonate ions, and carbonate ions react with calcium ions to form calcium carbonate flocculation precipitates;

[0110] (3) Anodic oxidation: The circulating water in the anode chamber undergoes water oxidation reaction to produce acidic circulating water;

[0111] (4) Acid-base separation: The acidic circulating water is extracted into the anode acid storage tank through the anode acid collection pipe and the acid extraction pump at a flow rate of 120 ML / min; the alkaline circulating water and hydrogen containing sediment in the cathode chamber overflow from the cathode gas-liquid outlet of the electrolytic cell and enter the gas-liquid inlet of the two separation units, thereby achieving the separation of the circulating water acid and the alkaline solution containing sediment;

[0112] (5) Gas-liquid separation: The alkaline circulating water containing sediment and hydrogen enter the gas-liquid inlet to form a cyclone, and hydrogen is separated by centrifugal force or gravity;

[0113] (6) Inhibit the oxidation of circulating water at the anode: Hydrogen circulates into the ruthenium-plated iridium-titanium mesh anode of the electrolytic cell, causing hydrogen oxidation reaction, which inhibits the oxidation of circulating water at the anode to produce acid and oxygen;

[0114] (7) Deprecipitation: The alkaline circulating water enters the membrane separation device, and the alkaline circulating water produced by the cathode hydrogen evolution reaction is subjected to sediment separation, and the magnesium hydroxide flocculation precipitate and the calcium carbonate flocculation precipitate therein are removed to obtain the alkaline circulating water after precipitation;

[0115] (8) Acid-base neutralization: The alkaline circulating water after precipitation is stored in the cathode alkaline liquid storage unit 8, and the alkaline circulating water therein and the acidic circulating water in the anode acid liquid storage tank 9 are mixed in the regeneration reuse water tank at a volume ratio of 4:1 to produce a neutralization reaction to obtain regenerated circulating water.

[0116] Under the same water inlet parameters as in Example 1 and Example 2, the electrode spacing was adjusted from 6 cm to 4 cm, and the effluent concentration was tested after the electrolytic cell was powered on. The effluent hardness was significantly reduced, and the specific ion concentration was Mg²⁺=0.03 g / L, Ca 2+ =0.05 g / L.

[0117] Example 4

[0118] A method for removing calcium and magnesium ions from circulating water, using Figure 2 The device shown comprises the following steps:

[0119] (1) Cathode hydrogen evolution: The treated circulating water is pumped into the electrolytic cell through the treated circulating water pump at a flow rate of 750 ML / min. A CO2 concentration of 1.2 mg / L is introduced into the treated circulating water in electrolytic cell 2 through a nanobubble machine, and a current density of 20 mA / cm is introduced. 2 , a direct current of 30V and 8A is applied, and the electrolysis time is 30min; the circulating water in the cathode chamber undergoes an electrochemical hydrogen evolution reaction to generate alkaline circulating water containing hydroxide ions and hydrogen;

[0120] (2) Calcium and magnesium ion flocculation precipitation: In the cathode chamber, hydroxide ions react with magnesium ions to form magnesium hydroxide flocculation precipitates; hydroxide ions react with dissolved carbon dioxide in the circulating water to form carbonate ions, and carbonate ions react with calcium ions to form calcium carbonate flocculation precipitates;

[0121] (3) Anodic oxidation: The circulating water in the anode chamber undergoes water oxidation reaction to produce acidic circulating water;

[0122] (4) Acid-base separation: The acidic circulating water is extracted into the anode acid liquid storage tank at a flow rate of 80 ml / min through the anode acid liquid collection pipe and the acid liquid extraction pump; the alkaline circulating water and hydrogen containing sediment in the cathode chamber overflow from the cathode gas-liquid outlet of the electrolytic cell and enter the gas-liquid inlet of the two separation units, thereby achieving the separation of the circulating water acid and the alkaline liquid containing sediment;

[0123] (5) Gas-liquid separation: The alkaline circulating water containing sediment and hydrogen enter the gas-liquid inlet to form a cyclone, and hydrogen is separated by centrifugal force or gravity;

[0124] (6) Inhibit the oxidation of circulating water at the anode: Hydrogen circulates into the ruthenium-plated iridium-titanium mesh anode of the electrolytic cell, causing hydrogen oxidation reaction, which inhibits the oxidation of circulating water at the anode to produce acid and oxygen;

[0125] (7) Deprecipitation: The alkaline circulating water enters the membrane separation device, and the alkaline circulating water produced by the cathode hydrogen evolution reaction is subjected to sediment separation, and the magnesium hydroxide flocculation precipitate and the calcium carbonate flocculation precipitate therein are removed to obtain the alkaline circulating water after precipitation;

[0126] (8) Acid-base neutralization: The alkaline circulating water after precipitation is stored in the cathode alkaline liquid storage unit 8, and the alkaline circulating water therein and the acidic circulating water in the anode acid liquid storage tank 9 are mixed in the regeneration reuse water tank at a volume ratio of 4:1 to produce a neutralization reaction to obtain regenerated circulating water.

[0127] Under the same water inlet parameters as in Example 1 and Example 2, the electrode spacing was adjusted from 6 cm to 1 cm, and the effluent concentration was tested after the electrolytic cell was powered on. The effluent hardness was significantly reduced, and the specific ion concentration was Mg²⁺=0.025 g / L, Ca 2+ = 0.041g / L.

[0128] Comparative Example 1

[0129] A method for removing calcium and magnesium ions from circulating water through chemical precipitation. Initial water hardness is 400 mg / L, pH = 7.5, Ca²⁺ = 150 mg / L, and Mg²⁺ = 50 mg / L. 15 mg / L of Ca(OH)₂ is added to adjust the pH of the circulating water to 10.5-11.5, followed by a 30 mg / L sodium carbonate supplement to remove excess Ca²⁺. Rapid stirring is performed for 10-15 minutes to disperse the agent, followed by slow stirring for 30-60 minutes to promote precipitation. The sedimentation tank is retained for 4 hours, and the precipitate is removed through sand filtration or fiber ball filters. The effluent hardness can be reduced to Mg²⁺ = 10 mg / L, Ca²⁺ = 10 mg / L, and Mg²⁺ = 10 mg / L. 2+ =22 mg / L.

[0130] Comparative Example 2

[0131] A method uses ultrasound to promote the metabolic activity of microorganisms (such as alkalinity-producing bacteria) to accelerate the formation of stable calcium and magnesium ion deposits. Alkalinity-producing bacteria are inoculated into a liquid culture medium and cultured with shaking at 37°C. The bacterial suspension is then added to seawater containing calcium and magnesium ions at a ratio of 1:1000 and irradiated with ultrasound (40 kHz frequency, 100 W power) for 30 minutes. The culture is then allowed to stand for 72 hours to promote the formation of biodeposits. Finally, the sediment is removed by centrifugation (3000 rpm, 10 minutes) or natural sedimentation. After treatment, the calcium ion concentration of the seawater is reduced from 420 mg / L to 79.8 mg / L, and the magnesium ion concentration is reduced from 1200 mg / L to 354 mg / L.

[0132] The initial and post-treatment concentrations of calcium and magnesium ions in the circulating water of Examples 1-4 and Comparative Examples 1-2 were measured, and the calcium and magnesium ion removal rates were calculated. The results are shown in Table 1.

[0133] Table 1

[0134] project Initial concentration of soluble calcium ions wt% Soluble calcium ion concentration after treatment wt% Calcium ion removal rate% Initial concentration of soluble magnesium ions wt% Soluble magnesium ion concentration after treatment wt% Magnesium ion removal rate% Example 1 62.50 7.40 88.16 37.50 6.62 82.35 Example 2 62.50 4.69 92.5 37.50 5.47 85.41 Example 3 62.50 2.34 96.26 37.50 3.91 89.57 Example 4 62.50 1.98 96.83 37.50 3.21 91.44 Comparative Example 1 75.00 11.00 85.30 25.00 5.00 80.00 Comparative Example 2 25.90 4.90 81.10 74.10 21.90 70.40

[0135] A comparison of the test results in Table 1 demonstrates that the circulating water calcium and magnesium ion removal device and method of the present invention exhibit significant technical advantages: while ensuring efficient calcium and magnesium ion removal (removal rates exceeding 85%), it also achieves low energy consumption. Furthermore, by precisely controlling the mixing ratio of acid and alkali, Examples 2 and 3 can directly produce circulating water that meets reuse standards. This entire process eliminates the need for the addition of additional scale inhibitors or the installation of specialized scale-inhibiting equipment, achieving a dual breakthrough in both efficient scale inhibition and energy conservation, thus broadening its applicability to industrial applications.

[0136] The chemical precipitation method used in Comparative Example 1 produces sludge that requires regular discharge and treatment, potentially causing secondary pollution. Furthermore, improper pH control (e.g., excessive alkalinity) can accelerate corrosion of metal equipment. The electrochemical scale inhibition method employed in this invention is environmentally friendly, requires no chemical additions, and prevents scale regeneration in real time. It is suitable for applications requiring long-term, stable scale prevention, such as small-scale cooling systems and domestic water supply.

[0137] The scale inhibition method mentioned in Comparative Example 2 suffers from the disadvantages of a long microbial culture cycle and the need to control microbial activity. Furthermore, in high-hardness water, the ultrasonic cavitation effect may not be sufficient to completely prevent scaling, necessitating integration with other technologies. Electrochemical scale inhibition, on the other hand, is highly adaptable to high-salinity and high-turbidity water and is particularly suitable for large-scale industrial circulating water systems. Furthermore, the strong oxidizing substances (such as ClO⁻) produced at the anode of electrochemical scale inhibition can kill microorganisms and algae, reducing the formation of biosludge and indirectly assisting in scale inhibition.

[0138] The present invention is further described above with the aid of specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the essence and scope of the present invention. Various modifications made to the above embodiments by ordinary technicians in this field after reading this specification are all within the scope of protection of the present invention.

Claims

1. A device for removing calcium and magnesium ions from circulating water, characterized in that: It includes an electrolysis unit, a two-phase separation unit, a precipitation unit and an anode acid collection and storage unit; The electrolysis unit includes an electrolytic cell, a water pump for circulating water to be treated connected to the electrolytic cell, and a plurality of anodes and cathodes located in the electrolytic cell. The anodes and cathodes are separated by a porous isolation mesh to form an anode chamber and a cathode chamber. The circulating water to be treated is electrolyzed in the electrolysis unit; the anode chamber is connected to the anode acid collection and storage unit through an acid extraction pump; The two-item separation unit includes a gas-liquid inlet, a gas outlet and a liquid outlet. The gas-liquid inlet is connected to the cathode gas-liquid outlet of the electrolytic cell, the gas outlet is connected to the anode fluid, and the liquid outlet is connected to the precipitation unit.

2. The device for removing calcium and magnesium ions from circulating water according to claim 1, characterized in that: It also includes an acid-base neutralization unit; The acid-base neutralization unit includes a cathode alkali liquid storage unit and a neutralization and recycling unit connected to the precipitation unit; the cathode alkali liquid storage unit and the anode acid liquid collection and storage unit are respectively connected to the neutralization and recycling unit.

3. The device for removing calcium and magnesium ions from circulating water according to claim 1, characterized in that: The anode is arranged inside the cathode with a spacing of 1 to 10 cm; and / or, The isolation net is a three-layer nylon net structure, the middle nylon net is 12500 mesh, and the outer nylon net is 400 mesh; and / or, The anode, cathode and isolation net are all hollow cylindrical structures, and the nylon net is set between the anode and cathode.

4. The device for removing calcium and magnesium ions from circulating water according to claim 1, characterized in that: The sedimentation separation device is a sedimentation tank or a membrane separation device; the sedimentation tank is one of a vertical flow sedimentation tank, a horizontal flow sedimentation tank, a radial flow sedimentation tank and an inclined tube sedimentation tank; the membrane separation device is at least one of an ultrafiltration membrane assembly, a microfiltration assembly and a composite membrane separation system.

5. The device for removing calcium and magnesium ions from circulating water according to claim 1, characterized in that: A carbon dioxide pumping device is provided on the electrolytic cell.

6. A method for removing calcium and magnesium ions from circulating water, characterized in that: The device for removing calcium and magnesium ions from circulating water according to any one of claims 1 to 5 comprises the following steps: Cathode hydrogen evolution: The circulating water to be treated is pumped into the electrolyzer through the circulating water pump to be treated. The circulating water to be treated is electrolyzed, and the circulating water to be treated undergoes electrochemical hydrogen evolution reaction in the cathode chamber to generate alkaline circulating water containing hydroxide ions and hydrogen; Calcium and magnesium ion flocculation precipitation: In the cathode chamber, hydroxide ions react with magnesium ions to form magnesium hydroxide flocculation precipitates; hydroxide ions react with dissolved carbon dioxide in the circulating water to form carbonate ions, and carbonate ions react with calcium ions to form calcium carbonate flocculation precipitates; Anodic oxidation: The circulating water in the anode chamber undergoes water oxidation reaction to produce acidic circulating water; Acid-base separation: The flow rate of the circulating water pump to be treated is greater than the flow rate of the acid extraction pump, which creates a pressure difference between the inside and outside of the anode chamber. The acidic circulating water produced in the anode chamber is confined in the anode chamber and pumped into the anode acid collection and storage unit through the acid extraction pump; the alkaline circulating water and hydrogen containing sediment in the cathode chamber overflow from the cathode gas-liquid outlet of the electrolyzer and enter the gas-liquid inlet of the two separation units, thus achieving the separation of the circulating water acid and the alkaline solution containing sediment; Gas-liquid separation: The alkaline circulating water containing sediment and hydrogen enter the gas-liquid inlet to form a cyclone, and hydrogen is separated by centrifugal force or gravity; Inhibit the oxidation of anode circulating water: After hydrogen is separated into gas and liquid by the gas-liquid separation device, it circulates into the anode chamber and undergoes hydrogen oxidation reaction, thereby inhibiting the oxidation of circulating water at the anode to produce acid and oxygen; Deprecipitation: The alkaline circulating water produced by the cathode hydrogen evolution reaction is separated and the precipitates therein are removed to obtain deprecipitated alkaline circulating water.

7. A method for removing calcium and magnesium ions from circulating water according to claim 6, characterized in that: The flow rate of the circulating water pump to be treated is 500ML / min~1000ML / min, and the flow rate of the acid extraction pump is 50ML / min~120ML / min.

8. The method for removing calcium and magnesium ions from circulating water according to claim 6, wherein: After the deprecipitation step, an acid-base neutralization step is also included: the alkaline circulating water after the precipitation is mixed with the acidic circulating water in the anode acid collection and storage unit to undergo a neutralization reaction until it becomes neutral, thereby obtaining regenerated circulating water; and / or, the mixing volume ratio of the alkaline circulating water to the acidic circulating water is (5~10):

1.

9. The method for removing calcium and magnesium ions from circulating water according to claim 6, characterized in that: The current density of the electrolysis is 5-20 mA / cm 2 , direct current with voltage ≤30V and current intensity ≤10A, and electrolysis time is 30~120min.

10. The method for removing calcium and magnesium ions from circulating water according to claim 6, characterized in that: Carbon dioxide is introduced into the circulating water to be treated to generate circulating water to be treated with a carbon dioxide concentration of 1.2 g / L.

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