Hardness-removing, scale-inhibiting and sterilizing system for circulating water of power plant

Abstract

The utility model discloses a hardness removal, scale inhibition and sterilization system for circulating water of a power plant, which comprises a pretreatment system, an electrochemical descaling system, an electro-adsorption sterilization system and a high-pressure oxidation polarization system which are connected in sequence, and a small amount of cooling tower circulating water passes through the pretreatment system and the electrochemical descaling system in sequence. A small amount of effluent of the electrochemical descaling system enters the electro-adsorption system, desorption and concentration produced water enters the electrolytic sterilization system, produced water of the electrolytic sterilization system enters the high-pressure oxidation polarization system, and produced water of the high-pressure oxidation polarization system flows back to the cooling tower; backwashing water of the electrochemical descaling system, adsorption produced water of the electro-adsorption system and backwashing water of the electrolytic sterilization system enter the desulfurization system to be recycled; and the rest circulating water of the cooling tower and the effluent of the electrochemical descaling system directly enter the oxidation polarization system. Various systems are combined, so that hardness removal, scale inhibition, corrosion inhibition and sterilization of the circulating water of the power plant are realized without adding chemical water treatment agents, secondary pollution is avoided, and the circulating water concentration multiple is relatively high, and relatively good economic benefits and environmental benefits are achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of wastewater treatment and resource recycling, and particularly relates to a system for removing hardness, scale and bacteria from power plant circulating water. Background Art

[0002] At present, China is facing the basic water situation of water resource shortage and water environment ecological deterioration, and the water safety situation is not optimistic. There is no other way to solve the problem but to save water, and giving priority to water conservation has also become the primary task of China's water pollution control, water ecological protection and water resource conservation. The power industry is a typical industry with high water consumption and high energy consumption. Therefore, the power industry faces a difficult task of water conservation and emission reduction in the process of realizing green and high-quality development.

[0003] For the power industry, the total amount of cooling circulating water accounts for up to 90% of the total water consumption. Solving the problem of circulating water treatment is of great significance for water conservation and emission reduction in thermal power plants. Therefore, the key to water conservation in the power industry is to improve the utilization rate of industrial cooling circulation, and the main way is to increase the circulating water concentration ratio. However, with the increase of the concentration ratio, the concentrations of scaling ions (such as Ca 2+ , Mg 2+ , HCO3 - , CO3 2- etc.) in the system also increase, which will lead to the deposition of scale (such as CaCO3, MgCO3, etc.) on the surface of the heat exchanger, reduce the heat transfer efficiency, accumulate microorganisms to form slime, and even cause under-scale corrosion, threatening the safe operation of the unit. It can be seen that the scaling of hardness ions is one of the core problems affecting the stable operation of the circulating water system at high concentration ratios.

[0004] At present, domestic power plants mainly adopt traditional chemical methods, that is, treating circulating water by adding scale inhibitors, corrosion inhibitors and bactericides to the circulating water. However, the chemical treatment method has high application cost and serious secondary pollution, and it is difficult to fully meet the requirements of water conservation and energy conservation in power plants under the new environmental protection requirements. Summary of the Invention

[0005] In view of the above problems existing in the prior art, the utility model provides a system for removing hardness, scale and bacteria from power plant circulating water. By adopting the process combination of a pretreatment system, an electrochemical scale removal system, an oxidation polarization system and an electroadsorption sterilization system, the system realizes the effects of scale removal, corrosion inhibition and sterilization of power plant circulating water without adding chemical water treatment agents, has no secondary pollution, has a high circulating water concentration ratio, and has good economic and environmental benefits.

[0006] The object of the present utility model is achieved in the following manner: A hard scale removal, scale inhibition and sterilization system for power plant circulating water includes a pretreatment system, an electrochemical scale removal system, an electro-adsorption sterilization system and a high-pressure oxidation polarization system connected in sequence. 1% - 2% of the circulating water in the cooling tower enters the pretreatment system, and the pretreated circulating water enters the electrochemical scale removal system. 0.1% - 2% of the effluent from the electrochemical scale removal system enters the electro-adsorption sterilization system. The electro-adsorption sterilization system includes an electro-adsorption system and an electrolytic sterilization system. The effluent from the electrochemical scale removal system entering the electro-adsorption sterilization system enters the electro-adsorption system, and the desorbed and concentrated produced water enters the electrolytic sterilization system. The produced water of the electrolytic sterilization system enters the high-pressure oxidation polarization system, and the produced water of the high-pressure oxidation polarization system returns to the cooling tower; The backwash water of the electrochemical scale removal system, the adsorption produced water of the electro-adsorption system and the backwash water of the electrolytic sterilization system all enter the desulfurization system for reuse; 98% - 99% of the circulating water in the cooling tower and the rest of the effluent from the electrochemical scale removal system except for that entering the electro-adsorption sterilization system directly enter the oxidation polarization system.

[0007] The cathode of the electrochemical scale removal system is a graphene carbon rod, and the anode is a steel plate coated with a precious metal oxide coating by titanium metal. A low-voltage high-frequency pulsed direct current is connected between the anode and the cathode. The low voltage does not exceed 12V, and the high frequency is 1kHz - 1MHz, forming a low-voltage electric field not exceeding 12V.

[0008] When the calcium and magnesium ions are saturated on the cathode plate, the positive and negative poles are switched for reverse polarization desorption, and the concentrated water rich in calcium carbonate enters the desulfurization system.

[0009] The cathode of the electro-adsorption system is a graphene carbon rod, and the anode is coconut shell activated carbon. A low-voltage high-frequency pulsed direct current is connected between the anode and the cathode. The low voltage does not exceed 12V, and the high frequency is 1kHz - 1MHz, forming a low-voltage electric field not exceeding 12V.

[0010] The cathode of the electrolytic sterilization system is a graphene carbon rod, and the anode is a steel plate coated with a precious metal oxide layer by titanium metal. A low-voltage high-frequency pulsed direct current is connected between the anode and the cathode. The low voltage does not exceed 12V, and the high frequency is 1kHz - 1MHz, forming a low-voltage electric field not exceeding 12V.

[0011] The cathode of the high-pressure oxidation polarization system is a graphene carbon rod, and the anode is a steel plate coated with a precious metal oxide layer by titanium metal. A high-voltage direct current is connected between the anode and the cathode. The high voltage is 1500V - 30000V, forming a high-voltage electrostatic field not exceeding 30000V.

[0012] Compared with the prior art, the present utility model adopts the combination of a pretreatment system, an electrochemical scale removal system, an electro-adsorption sterilization system and a high-pressure oxidation polarization system, achieving the effects of hard scale removal, scale inhibition, corrosion inhibition and sterilization for power plant circulating water without adding chemical water treatment agents, without secondary pollution, and having a high circulating water concentration ratio, good economic benefits and environmental benefits.

[0013] The treated circulating water pretreated by the electrochemical scale removal system not only replaces the existing technology of adjusting the water body pH by adding acid, but also achieves the purposes of hardness removal and scale inhibition.

[0014] Through the treatment of the electro-adsorption sterilization system process, not only can the salt content in the water body be reduced, but also a large amount of hypochlorite can be generated, which can replace or greatly reduce the addition of bactericides. While meeting the sterilization requirements, it reduces environmental pollution and has good economic and environmental benefits.

[0015] The circulating water is subjected to secondary scale inhibition and anti-corrosion treatment through the high-voltage polarization oxidation system, which further guarantees the efficient electrochemical scale removal and the operation with high alkalinity. Brief Description of the Drawings

[0016] Figure 1 It is the process flow diagram of the present utility model. Detailed Embodiments

[0017] The present utility model will be further described below in conjunction with the drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present utility model and are not used to limit the scope of the present utility model. After reading the content of the present utility model, those skilled in the art can make various changes or modifications to the present utility model, and these equivalent forms also fall within the scope defined by the present utility model.

[0018] As Figure 1 shown, a system for removing hardness, inhibiting scale and sterilizing circulating water in a power plant includes a pretreatment system, an electrochemical scale removal system, an electro-adsorption sterilization system and a high-voltage oxidation polarization system connected in sequence. 1% - 2% of the cooling tower circulating water enters the pretreatment system, and the pretreated cooling tower circulating water enters the electrochemical scale removal system. 0.1% - 2% of the effluent from the electrochemical scale removal system (the water volume can be adjusted according to the actual requirements such as the effluent water quality of the electrochemical scale removal system, such as chloride ion concentration and bactericide demand) enters the electro-adsorption sterilization system. The electro-adsorption sterilization system includes an electro-adsorption system and an electrolytic sterilization system. The effluent from the electrochemical scale removal system entering the electro-adsorption sterilization system enters the electro-adsorption system, and the desorbed and concentrated product water enters the electrolytic sterilization system. The product water of the electrolytic sterilization system enters the high-voltage oxidation polarization system, and the product water of the high-voltage oxidation polarization system returns to the cooling tower; the backwash water of the electrochemical scale removal system, the adsorption product water of the electro-adsorption system and the backwash water of the electrolytic sterilization system all enter the desulfurization system for reuse; 98% - 99% of the cooling tower circulating water and the remaining effluent from the electrochemical scale removal system except for the part entering the electro-adsorption sterilization system (i.e., 98% - 99.9% of the effluent from the electrochemical scale removal system) directly enter the oxidation polarization system.

[0019] The cathode of the electrochemical scale removal system is a graphene carbon rod, and the anode is a steel plate coated with a precious metal oxide coating by titanium metal. A low-voltage high-frequency pulsed direct current is connected between the anode and the cathode. The low voltage does not exceed 12V, and the high frequency is 1kHz - 1MHz, forming a low-voltage electric field not exceeding 12V.

[0020] When the calcium and magnesium ions are enriched to saturation on the cathode plate, the positive and negative poles are switched, and reverse polarization desorption occurs. The concentrated water rich in calcium carbonate enters the desulfurization system.

[0021] The cathode of the electro-adsorption system is a graphene carbon rod, and the anode is coconut shell activated carbon. A low-voltage high-frequency pulsed direct current is connected between the anode and the cathode. The low voltage does not exceed 12V, and the high frequency is 1kHz - 1MHz, forming a low-voltage electric field not exceeding 12V.

[0022] The cathode of the electrolytic sterilization system is a graphene carbon rod, and the anode is a steel plate coated with a precious metal oxide layer by titanium metal. A low-voltage high-frequency pulsed direct current is connected between the anode and the cathode. The low voltage does not exceed 12V, and the high frequency is 1kHz - 1MHz, forming a low-voltage electric field not exceeding 12V.

[0023] The electrochemical scale removal system, electro-adsorption system, and electrolytic sterilization system use high-frequency pulsed direct current because the voltage and current output by the high-frequency pulse are more stable.

[0024] The cathode of the high-pressure oxidation polarization system is a graphene carbon rod, and the anode is a steel plate coated with a precious metal oxide layer by titanium metal. A high-voltage direct current is connected between the anode and the cathode. The high voltage is 1500V - 30000V, forming a high-voltage electrostatic field not exceeding 30000V.

[0025] The specific process steps of the power plant circulating water hardness removal, scale inhibition, and sterilization system are as follows:

[0026] 1.1% - 2% of the circulating water in the cooling tower basin is used as raw water, introduced into the pretreatment system to remove the suspended solids therein, and then enters the electrochemical scale removal system.

[0027] 2. The circulating water entering the electrochemical scale removal system flows through a low-voltage electric field of no more than 12V formed by the positive and negative poles of low-voltage high-frequency pulsed direct current loaded on the cathode (graphene carbon rod) and anode (steel plate coated with precious metal oxide coating on titanium metal) of the electrochemical scale and hardness inhibitor equipment. A strongly alkaline environment (pH up to 14) will be generated in the water near the cathode. Calcium and magnesium ions will migrate towards the cathode plate and accumulate on the cathode plate to form scale. The flowing water becomes non-scaling water due to the significant reduction of alkalinity (temporary hardness), thus achieving the purpose of removing hardness and inhibiting scale in the circulating water. At the same time, a hydrogen evolution reaction occurs at the anode, making the overall effluent of the entire electrochemical scale removal system acidic, and generating substances with bactericidal effects such as ozone, hypochlorous acid, and hydrogen peroxide, so that there is still a certain bactericidal and algicidal effect after the effluent is mixed with the circulating water. When the calcium and magnesium ions are saturated in the accumulation on the cathode plate, the positive and negative poles are switched for reverse polarization desorption, and the concentrated water rich in calcium carbonate is used as the makeup water for the desulfurization system.

[0028] Reaction principle of the electrochemical scale removal system: Under the action of the electric field force, anions migrate towards the anode and cations migrate towards the cathode.

[0029] There is a reaction in the cathode area:

[0030] 2H2O + 2e - →H2 + 2OH -

[0031] Since OH is generated by electrolyzing water at the cathode - , near the cathode, HCO3 - and OH - combine to occur the following reactions:

[0032] HCO3 - + OH - →CO3 2- + H2O

[0033] Ca 2+ / Mg 2+ + 2OH - →Ca(OH)2↓

[0034] Ca 2+ / Mg 2+ + CO3 2- →CaCO3 / MgCO3↓

[0035] There is a reaction in the anode area:

[0036] Hydrogen evolution reaction: 2H2O - 4e - →O2↑ + 4H +

[0037] HCO3 - + H + →CO2↑ + H2O

[0038] Ozone: O2 + 2OH - -2e - → O3 + H2O

[0039] Free chlorine: Cl - -e - → Cl

[0040] Chlorine gas: 2Cl - -2e - → Cl2↑

[0041] Hypochlorous acid: Cl2 + H2O → H + + Cl - + HClO

[0042] Hydrogen peroxide: 2H2O - 2e - → H2O2 + 2H +

[0043] The pH of the effluent from the electrochemical scale removal system is 5.5 - 7, showing weak acidity. After mixing with the circulating water, the pH of the water body is 8 - 8.2, meeting the daily operation requirements of the circulating water in the power plant cooling tower. It can replace the existing technology of adjusting the pH by adding acid, saving the operation cost.

[0044] The removal rate of the alkalinity (temporary hardness) of the effluent from the electrochemical scale removal system can reach 30%. Under normal operation of the cooling tower circulating water, the concentration ratio is relatively high. By removing the alkalinity (temporary hardness) at a high concentration ratio through the electrochemical scale removal system, low-concentration ratio makeup water is replenished into the cooling tower circulating water system. The alkalinity (temporary hardness) brought in by the makeup water is at a low concentration ratio. The amount of alkalinity (temporary hardness) removed at a high concentration ratio by the electrochemical scale removal system is greater than the amount of alkalinity (temporary hardness) carried by the makeup water concentrated to a high concentration ratio. It can achieve the purpose of removing hardness and scale inhibition, and then replace the addition of chemical scale inhibitors.

[0045] The effluent from the electrochemical scale removal system carries some substances with bactericidal effects such as ozone, hypochlorous acid, and hydrogen peroxide. After the effluent is mixed with the circulating water, it still maintains a certain bactericidal and algicidal inactivation and inhibition effect. The main function of the electrochemical scale removal system is to remove hardness and scale, and the bactericidal substances are by-products with a small amount, which is not enough to meet the sterilization of the entire circulating water system, but can reduce the dosage of bactericidal agents.

[0046] 3. Take 0.1%-2% of the effluent from the electro-chemical scale removal system and feed it into the electro-sorption system. When it flows through the low-voltage electric field formed by loading the positive and negative poles of high-frequency pulsed direct current on the cathode (graphene carbon rod) and anode (coconut shell activated carbon) of the electro-sorption device, a double electric layer will be formed between the cathode and anode. Calcium and magnesium ions will migrate towards the cathode and be adsorbed on the cathode, while chloride ions will be adsorbed on the anode. The permanent hardness and chloride ions in the flowing water will be significantly reduced, thus achieving the purpose of desalination. The adsorbed water produced by the electro-sorption system can be used to supplement water for the desulfurization system, and the pH value of the effluent is 13.

[0047] The electro-sorption desorption concentrated water contains a large amount of chloride ions. After precipitation, it enters the electrolytic sterilization system and flows through the low-voltage electric field formed by loading the positive and negative poles of high-frequency pulsed direct current on the cathode (graphene carbon rod) and anode (steel plate coated with precious metal oxide layer by titanium metal) of the electrolytic sterilization device. Chloride ions will be electrolyzed into sodium hypochlorite and free chlorine. Hypochlorous acid is released from the water in gaseous form. After collection, it is mixed with strongly alkaline electrolyzed water to form calcium hypochlorite solution, which is used for circulating water sterilization treatment, thus reducing and even replacing the addition of oxidizing bactericides.

[0048] The principle of the electro-sorption sterilization system is as follows:

[0049] There is a reaction in the cathode region:

[0050] 2H2O + 2e - →H2 + 2OH -

[0051] Ca 2+ / Mg 2+ + 2OH - →Ca(OH)2↓

[0052] There is a reaction in the anode region:

[0053] Hydrogen evolution reaction: 2H2O - 4e - →O2↑ + 4H +

[0054] Free chlorine: Cl - - e - →Cl

[0055] Chlorine gas: 2Cl - - 2e - →Cl2↑

[0056] Hypochlorite: Cl2 + 4OH - →2H2O + 2ClO - + 2e -

[0057] 4. The effluent of the electrochemical scale removal system, the effluent of the electro-adsorption sterilization system, and the circulating water in the circulating water tank of the circulating tower are mixed and enter the high-pressure oxidation and polarization system. When flowing through the high-voltage electrostatic field formed by the positive and negative electrodes of the high-voltage direct current loaded on the cathode and anode of the high-voltage oxidation and polarization equipment, the circulating water flowing through is subjected to secondary scale inhibition and anti-corrosion treatment, providing further guarantee for efficient electrochemical scale removal and maintaining high-alkalinity operation.

[0058] The principle of the high-voltage oxidation and polarization device:

[0059] Anti-corrosion principle: When the circulating water flows through the high-voltage electrostatic field formed by the cathode and anode, the water molecules are charged and polarized. The positively charged water molecule clusters first contact the water-using wall as the cathode, blocking and wrapping the direct contact between anions, especially chloride ions, and the wall, playing a role of cathodic protection; at the same time, the oxide film continuously formed on the cathode wall by oxygen polarization plays a role in corrosion inhibition of the water-using system wall during the alternating attack and defense process of continuously breaking through the oxide film by chloride ions to form pitting corrosion.

[0060] Scale inhibition principle: When the circulating water flows through the high-voltage electrostatic field formed by the cathode and anode, the water molecules carry positive and negative charges and are polarized. The negatively charged water molecule clusters will wrap the direct contact between cations such as calcium and magnesium and the wall, playing a role of cathodic protection and scale inhibition. Cathodic protection and scale inhibition are suitable for water quality with an alkalinity of 3 - 14 mmol / L. When the alkalinity of the circulating water (temporary hardness) is 5 - 14 mmol / L, it is suitable for electrochemical scale removal treatment; when the alkalinity is greater than 14 mmol / L and less than 3 mmol / L, the efficiency of electrochemical alkalinity removal fluctuates, and when the circulating water quality shows a scaling tendency, it is guaranteed by the high-voltage oxidation and polarization scale inhibition and anti-corrosion process.

[0061] Implementation case one:

[0062] A certain power plant in Tianjin has 2 × 330MW subcritical coal-fired condensing steam turbine generator sets, adopting an open secondary circulating cooling system. The condenser tubes of the units are TP317L stainless steel tubes, and each unit is equipped with a countercurrent natural draft cooling tower. The circulating cooling water volume of the two units is 60000m 3 / h in summer and 40000m 3 / h. During the upgrading period, the electrochemical hard scale removal, fouling inhibition and sterilization system disclosed by the present utility model was used to treat the circulating water of the cooling tower of Unit 1. Designed according to the maximum water volume of the treated circulating water of 30,000 m³ / h, a new set of 500 m³ / h electrochemical scale removal system, 1 m³ / h electro-adsorption sterilization system and 30,000 m³ / h high-pressure oxidation polarization system were built. After the equipment was put into operation without adding any chemicals, the pH of the circulating water was 8.0 - 8.3, the average removal rate of alkalinity (temporary hardness) was 32.3%, the average residual chlorine in the effluent of the electro-adsorption sterilization was 0.87 mg / L, the corrosion rate of the whole process on 317L stainless steel was about 0.00096 mm / year, the average concentration ratio of the circulating water was about 7.12 times, and the overall operation effect was good. At the same time, the water produced by the electrochemical scale removal was used as the process water for the desulfurization system, saving 10% of the externally purchased calcium carbonate for desulfurization.

[0063] Case Two of Implementation:

[0064] The planned capacity of a power plant unit in Hubei is 2×350 MW supercritical condensing heating units + 2×50 MW back-pressure heating units. In the first phase, 1×350 MW + 1×50 MW were built, and the 50 MW back-pressure unit is equipped with a 370 t / h high-pressure boiler. An open secondary circulation cooling system is adopted, and the condenser tubes of the unit are TP317L stainless steel tubes, with a countercurrent natural draft cooling tower. During the technical transformation period, the electrochemical hard scale removal, fouling inhibition and sterilization system disclosed by the present utility model was used to treat the circulating water of the cooling tower of the unit. Designed according to the maximum water volume of the treated circulating water of 30,000 m³ / h, a new set of 500 m³ / h electrochemical scale removal system, 1 m³ / h electro-adsorption sterilization system and 30,000 m³ / h high-pressure oxidation polarization system were built. After the equipment was put into operation without adding any chemicals, the pH of the circulating water was 8.2 - 8.5, the average removal rate of alkalinity (temporary hardness) was 23%, the average residual chlorine in the effluent of the electro-adsorption sterilization was 0.65 mg / L, the corrosion rate of the whole process on 317L stainless steel was about 0.001 mm / year, the average concentration ratio of the circulating water was about 6.08 times, and the overall operation effect was good.

[0065] The above are only the preferred implementation modes of the present utility model. It should be noted that for those skilled in the art, without departing from the overall concept of the present utility model, several changes and improvements can still be made, and these should also be regarded as the protection scope of the present utility model.

Claims

1. A hard scale removal, scale inhibition and sterilization system for circulating water in a power plant, characterized in that: It includes a pre-treatment system, an electrochemical scale removal system, an electro-adsorption sterilization system, and a high-voltage oxidation polarization system connected in sequence. 1% - 2% of the cooling tower circulating water enters the pre-treatment system, and the pre-treated circulating water enters the electrochemical scale removal system. 0.1% - 2% of the effluent from the electrochemical scale removal system enters the electro-adsorption sterilization system. The electro-adsorption sterilization system includes an electro-adsorption system and an electrolytic sterilization system. The effluent from the electrochemical scale removal system entering the electro-adsorption sterilization system enters the electro-adsorption system, and the desorbed and concentrated product water enters the electrolytic sterilization system. The effluent from the electrolytic sterilization system enters the high-voltage oxidation polarization system, and the effluent from the high-voltage oxidation polarization system is recycled to the cooling tower; the backwash water of the electrochemical scale removal system, the adsorption product water of the electro-adsorption system, and the backwash water of the electrolytic sterilization system all enter the desulfurization system for reuse; 98% - 99% of the cooling tower circulating water and the rest of the effluent from the electrochemical scale removal system except for that entering the electro-adsorption sterilization system directly enter the oxidation polarization system.

2. The hard scale removal, scale inhibition and sterilization system for circulating water in a power plant according to claim 1, characterized in that: The cathode of the electrochemical scale removal system is a graphene carbon rod, and the anode is a steel plate coated with a precious metal oxide coating by titanium metal. A low-voltage high-frequency pulsed direct current is connected between the cathode and the anode. The low voltage does not exceed 12V, and the high frequency is 1kHz - 1MHz, forming a low-voltage electric field not exceeding 12V.

3. The hard scale removal, fouling resistance and sterilization system for circulating water in a power plant according to claim 2, wherein: When the calcium and magnesium ions are saturated in the enrichment on the cathode plate, the positive and negative poles are switched for reverse polarization desorption, and the concentrated water rich in calcium carbonate enters the desulfurization system.

4. The hard scale removal, fouling resistance and sterilization system for circulating water in a power plant according to claim 1, wherein: The cathode of the electro-adsorption system is a graphene carbon rod, and the anode is coconut shell activated carbon. A low-voltage high-frequency pulsed direct current is connected between the cathode and the anode. The low voltage does not exceed 12V, and the high frequency is 1kHz - 1MHz, forming a low-voltage electric field not exceeding 12V.

5. The hard scale removal, scale inhibition and sterilization system for circulating water in a power plant according to claim 1, wherein: The cathode of the electrolytic sterilization system is a graphene carbon rod, and the anode is a steel plate coated with a precious metal oxide layer by titanium metal. A low-voltage high-frequency pulsed direct current is connected between the cathode and the anode. The low voltage does not exceed 12V, and the high frequency is 1kHz - 1MHz, forming a low-voltage electric field not exceeding 12V.

6. The hard scale removal, scale inhibition and sterilization system for circulating water in a power plant according to claim 1, characterized in that: The cathode of the high-voltage oxidation polarization system is a graphene carbon rod, and the anode is a steel plate coated with a precious metal oxide layer by titanium metal. A high-voltage direct current is connected between the cathode and the anode. The high voltage is 1500V - 30000V, forming a high-voltage electrostatic field not exceeding 30000V.

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