A method for mitigating corrosion in the cooling water system of auxiliary equipment in thermal power plants

Abstract

This invention relates to the field of cooling water control methods, specifically to a corrosion mitigation control method for auxiliary cooling water systems in thermal power plants. Based on specific chemical analysis indicators of the circulating cooling water's pH, alkalinity, calcium hardness, and total dissolved solids, along with water temperature monitoring, the correlation coefficients of each indicator parameter are refined, and a stability index Iw is calculated. Acid is added to the circulating water to adjust the pH value, ensuring it remains within a set range. According to preset standards and based on the stability index Iw, the degree of scaling is determined, and a composite slow-release scale inhibitor is added to the circulating cooling water system. The stability index Iw and ΔB are jointly controlled, first ensuring Iw is within a first preset range, and then adjusting the lower limit of Iw to a second preset range, which is included within the first preset range. This invention ensures the safe operation of the system, avoids significant scaling and corrosion, ensures that system equipment does not experience significant scaling or corrosion perforation, and guarantees long-term safe and stable operation of the unit.

Description

Technical Field

[0001] This invention relates to the field of cooling water control methods, and more specifically to a method for mitigating corrosion in the cooling water system of auxiliary equipment in thermal power plants. Background Technology

[0002] The 660MW coal-fired power generating unit used in the thermal power plant has a single-unit circulating water volume of approximately 60,000 m³ for its condenser and auxiliary equipment circulating cooling water system. 3 The circulating water design requires zero discharge, with a concentration ratio of 5.4-6.0. The system materials are mainly stainless steel and carbon steel, especially the stainless steel pipes with smaller diameters inside the condenser and the carbon steel main pipes of the circulating water cooling system, as well as the carbon steel pipes with relatively small diameters in the circulating cooling water systems of auxiliary units such as the main engine lubricating oil cooler, generator hydrogen cooler, and generator stator water cooler. These pipes are relatively small in size and have thin walls, making them prone to corrosion or scaling during the circulation of water, which can cause abnormalities. Therefore, it is necessary to strengthen the treatment of the circulating water.

[0003] In recent years, traditional methods of treating circulating water systems, such as adding scale inhibitors and corrosion inhibitors and sulfuric acid, have been used for scale inhibition and corrosion prevention. For example, one method to improve corrosion and scaling in circulating cooling water involves using the ratio of chloride ion content in the circulating cooling water to that in the makeup water as the concentration ratio. Makeup water can be either soft water with a concentration ratio of 11-12 or tap water with a concentration ratio of 4-5. When soft water is used as makeup water with a concentration ratio of 11-12, the circulating system can achieve stable water quality or a state of slight scaling, reducing the degree of scaling by metal ions in the equipment. When tap water is used as makeup water with a concentration ratio of 4-5, the total ion concentration in the circulating system reaches a suitable level, resulting in relatively mild corrosion and scaling of the equipment.

[0004] However, the existing chemical dosing treatment for circulating water is carried out uniformly in the dosing tank at the water inlet of the pipeline. After the chemical is added, the circulating water is transported to various equipment through different delivery pipelines for heat exchange to meet the cooling needs of different equipment in the overall system. This does not take into account the carbon steel pipelines in the auxiliary cooling water system. Such circulating water is prone to causing local corrosion and perforation of carbon steel pipelines, resulting in repeated leaks. The original circulating cooling water treatment method is not very effective in preventing corrosion and inhibiting carbon steel equipment, and there are certain safety risks. Summary of the Invention

[0005] The present invention aims to provide a method for mitigating corrosion control in the cooling water system of auxiliary equipment in thermal power plants, in order to solve the problem that existing methods can cause localized corrosion and perforation of carbon steel pipes, resulting in pipe leaks.

[0006] The corrosion control methods for auxiliary cooling water systems in thermal power plants outlined in this plan include the following:

[0007] Based on the specific chemical analysis indicators of pH, alkalinity, calcium hardness and total dissolved solids of circulating cooling water and the water temperature monitoring, the correlation coefficients of each indicator parameter are refined, and the stability index Iw is calculated.

[0008] Add acid to the circulating water to adjust the pH value and keep it within the set range;

[0009] According to the preset standard, the degree of scaling is judged based on the stability index Iw. A composite slow-release scale inhibitor is added to the circulating water cooling. The corrosion prevention of carbon steel and stainless steel equipment is jointly regulated based on the stability index Iw and the ΔB discrimination method. First, the stability index Iw is made to be within the first preset range while ΔB is made to be less than or equal to the set value. Then, the lower limit of the stability index Iw is adjusted to be within the second preset range. The second preset range is included in the first preset range.

[0010] The beneficial effects of this plan are:

[0011] By simultaneously employing two stability indices, Iw and ΔB, and controlling water quality indicators through acid adjustment, along with the simultaneous addition of inorganic-organic composite corrosion and scale inhibitors, the system achieves higher operational stability. This ensures the condenser's stainless steel heat exchange tubes and carbon steel pipes remain in good condition, preventing significant scaling and corrosion. This guarantees that the system equipment does not experience significant scaling or corrosion perforation, ensuring long-term safe and stable operation of the unit.

[0012] Furthermore, the composite slow-release scale inhibitor uses an inorganic-organic composite corrosion inhibitor, including polycarboxylate, organic phosphonate and zinc salt.

[0013] The beneficial effects are: by adding inorganic-organic composite corrosion inhibitors, films can be formed on both the anode and the cathode. These corrosion inhibitors have polar groups and can be adsorbed on the metal surface to form a monomolecular film, preventing water and dissolved oxygen in the water from diffusing to the metal surface, thus achieving a better corrosion inhibition effect.

[0014] Furthermore, the zinc salt accounts for more than or equal to 0.8% of the total mass of the controlled-release scale inhibitor, and the zinc salt added to the circulating cooling water is at a concentration of 1.0–2.0 mg / L. The addition or subtraction of polycarboxylate and organophosphonate are synchronized with the preset weight.

[0015] The beneficial effect is that by setting the zinc salt content in the inorganic-organic composite corrosion inhibitor, the corrosion can be slowed down to the maximum extent.

[0016] Furthermore, the correlation coefficients include: coefficient A related to dissolved solids in water, in mg / L; coefficient B related to water temperature, in °C; coefficient C related to calcium hardness in water, expressed as calcium carbonate, in mg / L; and coefficient D related to alkalinity in water, expressed as calcium carbonate, in mg / L.

[0017] The beneficial effect is that the pre-setting of the correlation coefficient makes it easier to calculate the stability index Iw.

[0018] Furthermore, the stability index Iw is calculated using the formula: Iw = 2 * pHs - pH, where pHs is calculated according to the correlation coefficient, and pH is the actual pH value.

[0019] The beneficial effects are: the stability index Iw is calculated based on the measured pH value, which can adjust the circulating water in real time and dynamically to maintain the corrosion resistance of the circulating water.

[0020] Furthermore, the formula for calculating pHs is: pHs = 9.3 + A + B - (C + D).

[0021] The beneficial effects are: pHs calculation is based on various correlation coefficients, which can reflect the changes in the stability index Iw in real time and dynamically, thereby improving the real-time performance and accuracy of corrosion mitigation regulation and control.

[0022] Furthermore, the pH value of the circulating cooling water is set within a range that first needs to be met (8.0-8.5) and then (8.3-8.5).

[0023] The beneficial effect is that the stable characteristics of the circulating water are maintained within the set range of acidity adjustment.

[0024] Furthermore, the first preset range is 5.2-6.1, and the second preset range is 5.2-5.5.

[0025] The beneficial effects are: by setting two preset ranges, it is possible to first adjust to the approximate range and then adjust to the target range during the actual adjustment process, making the operation more convenient and the adjustment results more accurate.

[0026] Furthermore, the refinement process of the correlation coefficient is as follows:

[0027] The coefficient A, which is related to dissolved solids in water, is refined by incrementing the initial value in steps according to the low, lower-middle, middle, upper-middle and high concentrations of total dissolved solids in water. The initial value is set to 0.07 based on actual measurements. The set steps include 0.01 and 0.02. The low concentration is 50-100 mg / L incremented in steps of 25 mg / L, the lower-middle concentration is 100-200 mg / L incremented in steps of 50 mg / L, the middle concentration is 200-400 mg / L incremented in steps of 100 mg / L, the upper-middle concentration is 400-1000 mg / L incremented in steps of 200 mg / L, and the high concentration is 1000-2000 mg / L incremented in steps of 500 mg / L.

[0028] The coefficient B, which is related to water temperature, is divided into 15 segments from 0 to 82℃, with each segment spanning 1, 3, 3, 3, 3, 3, 5, 3, 5, 5, 6, 4, 8, 5, 11. The coefficient B is obtained by decreasing the initial value of 2.6 in increments of 0.1.

[0029] The coefficient C value related to calcium hardness in water was calculated for calcium carbonate in the range of 200 to 900 percentiles in increments of 100. For each calcium hardness range of 0 to 90, the value was increased by increments of 10 at each point, starting from the initial value.

[0030] The coefficient D, which is related to alkalinity in water, was calculated for calcium carbonate at the 200–800 percentile using a step size of 100. Within each calcium carbonate hardness range of 0–90, the value was increased incrementally from the initial set value at each point using an increasing step size.

[0031] The beneficial effect is that, based on the refinement of the correlation coefficient, the operating conditions of the cooling water can be preset in advance and quantified into numerical values, so that the stability index Iw can be calculated quickly and timely.

[0032] Furthermore, at the delivery pipeline leading out of the dosing tank and at the inlet of each equipment, a cooling treatment of a preset duration is performed when the control stability index Iw is within the first preset range.

[0033] The beneficial effects are: by reducing the temperature of the circulating water entering the equipment from the conveying pipeline when the stability index is within the first preset range, the liquid pressure inside the pipe can be reduced to a certain extent. Combined with the adjustment of the stability index Iw, the degree of corrosion is reduced, while the heat exchange rate and efficiency are improved. Furthermore, no cooling treatment is applied during the subsequent adjustment of the stability index Iw. After the circulating water is adjusted to the most suitable state, the pressure of the conveying pipeline is maintained, further maintaining the conveying pressure of the pipeline, allowing the circulating water to flow stably for heat exchange. Attached Figure Description

[0034] Figure 1This is a schematic diagram of an embodiment of the corrosion mitigation and control method for the cooling water system of auxiliary equipment in thermal power plants according to the present invention. Detailed Implementation

[0035] The following detailed description provides further details on specific implementation methods.

[0036] Example

[0037] A method for mitigating corrosion in the cooling water system of auxiliary equipment in a thermal power plant, such as... Figure 1 As shown: Includes the following:

[0038] Based on the specific chemical analysis indicators of pH, alkalinity, calcium hardness, and total dissolved solids of the circulating cooling water, and the water temperature monitoring data, the correlation coefficients of each indicator parameter are refined, and the stability index Iw is calculated.

[0039] The process of refining the correlation coefficient is as follows: The coefficient A, which is related to dissolved solids in water, is refined by incrementing the initial value at a set step size according to the low, lower-middle, middle, upper-middle and high ranges of the total dissolved solids concentration in water. The initial value is set to 0.07 based on actual measurements. The set step sizes include 0.01 and 0.02. The low range is 50-100 mg / L incremented at a step size of 25 mg / L, the lower-middle range is 100-200 mg / L incremented at a step size of 50 mg / L, the middle range is 200-400 mg / L incremented at a step size of 100 mg / L, the upper-middle range is 400-1000 mg / L incremented at a step size of 200 mg / L, and the high range is 1000-2000 mg / L incremented at a step size of 500 mg / L.

[0040] The coefficient B, which is related to water temperature, is obtained by dividing the 0-82℃ range into 15 segments with a span of 1, 3, 3, 3, 3, 3, 5, 3, 5, 5, 5, 6, 4, 8, 5, 11. The coefficient B is obtained by decreasing the initial value of 2.6 in increments of 0.1.

[0041] The coefficient C, which is related to calcium hardness in water, is calculated for calcium carbonate in the range of 200 to 900 percentiles in increments of 100. For each calcium hardness range of 0 to 90, the coefficient C is increased by increments of 10 from the initial value at each point.

[0042] The coefficient D, which is related to alkalinity in water, is calculated for calcium carbonate in the range of 200 to 800 percentiles in increments of 100. For each calcium carbonate in the range of 0 to 90 percentiles, the coefficient D is increased by increments of 10 from the initial value at each point.

[0043] The correlation coefficients include: coefficient A related to dissolved solids in water, in mg / L, as shown in Table 1; coefficient B related to water temperature, in °C, as shown in Table 2; coefficient C related to calcium hardness in water, expressed as calcium carbonate, in mg / L, as shown in Table 3; and coefficient D related to alkalinity in water, expressed as calcium carbonate, in mg / L, as shown in Table 4.

[0044] Table 1. Coefficient A values ​​corresponding to different dissolved solids

[0045]

[0046] Table 2. Coefficient B values ​​at different temperatures

[0047] Temperature (°C) B value Temperature (°C) B value Temperature (°C) B value Temperature (°C) B value 0～1 2.6 14～17 2.2 32～37 1.8 56～64 1.4 2～5 2.5 18～21 2.1 38～43 1.7 65～70 1.3 6～9 2.4 22～27 2.0 44～50 1.6 71～82 1.2 10～13 2.3 28～31 1.9 51～55 1.5

[0048] Table 3. Coefficient C values ​​corresponding to different calcium hardness levels.

[0049]

[0050] Table 4. Coefficient D values ​​corresponding to different alkalinities.

[0051]

[0052] By refining the coefficients A, B, C, and D, the actual control situation of auxiliary cooling water in thermal power plants can be accurately and intuitively shown, thereby improving the calculation speed and timeliness of the stability index Iw.

[0053] The formula for calculating the stability index Iw is:

[0054] Iw = 2 * pHs - pH;

[0055] pHs is calculated based on the correlation coefficient, where pH is the measured pH value. The formula for calculating pHs is: pHs = 9.3 + A + B - (C + D).

[0056] Add acid to the circulating water to adjust the pH value, so that the upper limit of the pH value is within the set range, which is 8.0-8.5, and further adjust it to 8.3-8.5.

[0057] The degree of scaling is determined based on the stability index Iw according to the preset standards, as shown in Table 5. A composite slow-release scale inhibitor is added to the circulating water. The corrosion prevention of carbon steel and stainless steel equipment is jointly regulated according to the stability index Iw and the ΔB discrimination method. First, the stability index Iw is kept within the first preset range while ΔB is kept less than or equal to the set value, which is 0.2. Then, the lower limit of the stability index Iw is adjusted to be within the second preset range, which is included in the first preset range. The first preset range is 5.2-6.1, and the second preset range is 5.2-5.5.

[0058] The discriminant formula for the △B discriminant method is:

[0059]

[0060] in, Cl in circulating water - Content, mg / L; To replenish Cl in the water - Content, mg / L; YD 循 The hardness of the circulating water is expressed in mg / L; YD 补 Add water hardness, mg / L. When ΔB≤0.2 (sometimes less than zero), it indicates that the water quality is stable and there is no tendency for scaling; when ΔB>0.2, it indicates that the water quality is unstable and there is a tendency for scaling.

[0061] The composite slow-release scale inhibitor uses an inorganic-organic composite corrosion inhibitor, including polycarboxylate, organic phosphonate and zinc salt. The zinc salt accounts for more than or equal to 0.8% of the mass of the composite slow-release scale inhibitor, and the content of zinc salt added to the circulating cooling water is 1.0 to 2.0 mg / L.

[0062] Table 5 Preset Standards

[0063]

[0064] This embodiment first refines the correlation coefficients of various index parameters, calculates the stability index Iw based on the correlation coefficients, and adopts an inorganic-organic composite corrosion inhibitor, namely a combination of polycarboxylate, organic phosphonate, and zinc salt. This corrosion inhibitor is an organic mixed type. Combined with the stability index Iw and the ΔB discriminant method, Iw is gradually adjusted to a smaller range. The composite corrosion inhibitor can form films at both the anodic and cathodic sites. The corrosion inhibitor has polar groups and can adsorb onto the metal surface to form a monomolecular film, preventing water and dissolved oxygen in the water from diffusing to the metal surface. It coordinates the anti-corrosion process of carbon steel and stainless steel, thereby synergistically preventing scale and corrosion of stainless steel and carbon steel pipelines and equipment, achieving a better corrosion inhibition effect. It prevents the system from having scale and corrosion perforation problems in both carbon steel and stainless steel equipment, resulting in higher overall operational continuity and ensuring long-term safe and stable operation of the unit.

[0065] Example 2

[0066] A method for mitigating corrosion in a cooling water system for auxiliary equipment in a thermal power plant, based on Example 1, further includes: verifying a composite corrosion inhibitor formula by placing carbon steel and stainless steel inserts in the circulating water and controlling corrosion mitigation according to the method of Example 1; calculating the corrosion rate by weighing the weight loss of the inserts; and the method for calculating the corrosion rate is as follows:

[0067] Corrosion rate = 87.6 × 1000 W / SPT (mm / a);

[0068] In the formula: W represents the weight loss of the hanging piece in grams, and S represents the surface area of ​​the hanging piece: 28 cm². 2 T represents the test time for the padding, in hours; P represents the density of the padding type; the density of stainless steel is 7.92 g / cm³. 3 The density of carbon steel is 7.85 g / cm³. 3 .

[0069] The hanging plates have a size of 50×25×2mm. Wipe the stainless steel and carbon steel hanging plates clean of rust-preventing grease with filter paper, then soak them in anhydrous ethanol, wipe them with degreased cotton, place them on clean filter paper, blot them dry with the filter paper, and place them in a desiccator for at least 4 hours before weighing. Alternatively, they can be stored in a desiccator until use, and weighed before hanging them in the circulating water tank. First, carbon steel and stainless steel plates were weighed and suspended in the circulating water tank. After 15-30 days, the plates were removed, treated, and the corrosion rate was calculated. The treatment method after removal was as follows: the plates were brushed clean, rinsed with distilled water, wiped and dried with filter paper, soaked in anhydrous ethanol for about 3 minutes, placed on clean filter paper, dried with filter paper, and placed in a desiccator for more than 4 hours. The weighing accuracy was accurate to 0.0001g. This was used to evaluate the corrosion inhibition effect of the circulating water scale inhibitor. The corrosion rate of carbon steel plates was less than 0.075mm / a to be considered qualified, and the corrosion rate of stainless steel plates was less than 0.005mm / a to be considered qualified.

[0070] Experiments have shown that, after more than half a year of operation, corrosion and leakage of carbon steel pipes in the circulating water cooling system have been extremely rare. Statistics show that the corrosion and leakage rate of carbon steel pipes in the cooling water system has decreased by 90%, and stainless steel pipes have not shown significant scaling or corrosion. This has solved the problem of high corrosion rates of carbon steel in the current circulating water system, effectively controlling the safety risks of unit operation. By controlling water quality stability using traditional circulating water treatment methods, the cost of replacing carbon steel pipes in the turbine has been greatly reduced, resulting in significant savings in circulating water treatment costs. Compared with circulating water electrochemical treatment and membrane treatment methods, this significantly reduces engineering investment and saves hundreds of thousands of yuan or more in operating costs annually.

[0071] Example 3

[0072] A method for controlling corrosion in a cooling water system for auxiliary equipment in a thermal power plant, which differs from Embodiment 1, involves performing a cooling process for a preset duration at the delivery pipeline leading out of the chemical dosing tank and at the inlet of each piece of equipment when the stability index Iw is within a first preset range. The cooling process is performed by applying low-temperature air, and the preset duration is set according to the time when the stability index Iw is within the first preset range. The preset duration is set to 5 minutes.

[0073] Because the overall diameter of the delivery pipe leading from the dosing tank is relatively large, and the thickness of the delivery pipe is greater than that of the pipes introduced into each piece of equipment, the corrosion situation of the delivery pipe is much better than that of the smaller pipes introduced into the equipment. That is, the parameters and water pressure of the circulating water have little impact on the corrosion of the delivery pipe. However, the corrosion situation of the smaller pipes introduced into the equipment and the maintenance after corrosion are more troublesome. Therefore, this embodiment reduces the temperature of the circulating water entering the equipment from the delivery pipe at the port of entry when the stability index is within the first preset range. This reduces the liquid pressure inside the pipe to a certain extent before the stability index of the circulating water reaches the final target within the first preset range. Combined with the stability index I... The initial adjustment of the stability index Iw reduces the corrosion of the pipes inside the equipment. At the same time, the cooled circulating water can improve the heat exchange rate and efficiency. Furthermore, no cooling treatment is applied when the subsequent stability index Iw reaches the second preset range of the final target. After the circulating water is adjusted to the most suitable state, the pressure of the delivery pipeline is maintained to further maintain the pipeline delivery pressure and allow the circulating water to flow stably for heat exchange. Through the two adjustment processes of the stability index Iw of the circulating water, the corrosion of the pipes inside the equipment is made controllable, ensuring the safe operation of the overall heat exchange system. The corrosion of stainless steel and carbon steel pipes is mitigated in the most optimal way, which improves the service life of the system equipment, reduces the number of pipes to be repaired and replaced, and lowers maintenance costs.

[0074] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for mitigating corrosion in a cooling water system for auxiliary equipment in a thermal power plant, characterized in that: Includes the following: Based on the specific chemical analysis indicators of pH, alkalinity, calcium hardness and total dissolved solids of circulating cooling water and the water temperature monitoring, the correlation coefficients of each indicator parameter are refined, and the stability index Iw is calculated. The correlation coefficients include: coefficient A related to dissolved solids in water, in mg / L; coefficient B related to water temperature, in °C; coefficient C related to calcium hardness in water, expressed as calcium carbonate, in mg / L; and coefficient D related to alkalinity in water, expressed as calcium carbonate, in mg / L. The stability index Iw is calculated as follows: Iw = 2 * pHs - pH, where pHs is calculated according to the correlation coefficients, and pH is the measured pH value. The pHs is calculated as follows: pHs = 9.3 + A + B - (C + D). Add acid to the circulating water to adjust the pH value and keep it within the set range; According to the preset standard, the degree of scaling is judged based on the stability index Iw. A composite slow-release scale inhibitor is added to the circulating water cooling. The corrosion prevention of carbon steel and stainless steel equipment is jointly regulated based on the stability index Iw and ΔB discrimination method. First, the stability index Iw is placed within the first preset range while ΔB is less than or equal to the set value. Then, the lower limit of the stability index Iw is adjusted to be within the second preset range. The second preset range is included in the first preset range. The discriminant formula for the △B discriminant method is: ； in, Cl in circulating water - Content, mg / L; To replenish Cl in the water - Content, mg / L; The hardness of the circulating water is expressed in mg / L. Add water hardness, mg / L; The first preset range is 5.2-6.1, the second preset range is 5.2-5.5, and the refinement process of the correlation coefficient is as follows: The coefficient A, which is related to dissolved solids in water, is refined by incrementing the initial value in steps according to the low, lower-middle, middle, upper-middle and high concentrations of total dissolved solids in water. The initial value is set to 0.07 based on actual measurements. The set steps include 0.01 and 0.

02. The low concentration is 50-100 mg / L incremented in steps of 25 mg / L, the lower-middle concentration is 100-200 mg / L incremented in steps of 50 mg / L, the middle concentration is 200-400 mg / L incremented in steps of 100 mg / L, the upper-middle concentration is 400-1000 mg / L incremented in steps of 200 mg / L, and the high concentration is 1000-2000 mg / L incremented in steps of 500 mg / L. The coefficient B, which is related to water temperature, is divided into 15 segments from 0 to 82℃, with each segment spanning 1, 3, 3, 3, 3, 3, 5, 3, 5, 5, 6, 4, 8, 5, 11. The coefficient B is obtained by decreasing the initial value of 2.6 in increments of 0.

1. The coefficient C value related to calcium hardness in water was calculated for calcium carbonate in the range of 200 to 900 percentiles in increments of 100. For each calcium hardness range of 0 to 90, the value was increased by increments of 10 at each point, starting from the initial value. The coefficient D, which is related to alkalinity in water, is calculated for calcium carbonate in the range of 200 to 800 percentiles in increments of 100. For each calcium carbonate in the range of 0 to 90 percentiles, the coefficient D is increased by increments of 10 from the initial value at each point.

2. The corrosion mitigation and control method for a thermal power plant auxiliary equipment cooling water system according to claim 1, characterized in that: The composite slow-release scale inhibitor uses an inorganic-organic composite corrosion inhibitor, including polycarboxylate, organic phosphonate and zinc salt.

3. The corrosion mitigation and control method for a thermal power plant auxiliary equipment cooling water system according to claim 2, characterized in that: The zinc salt accounts for 0.8% or more of the mass of the controlled-release scale inhibitor, and the zinc salt added to the circulating water is 1.0 to 2.0 mg / L. The increase or decrease of polycarboxylate and organophosphonate is synchronized with the preset weight.

4. The method for mitigating corrosion in a cooling water system for auxiliary equipment in a thermal power plant according to claim 1, characterized in that: The set range includes 8.0-8.5, which is satisfied first, and 8.3-8.5, which is satisfied later.

5. The method for mitigating corrosion in a cooling water system for auxiliary equipment in a thermal power plant according to claim 1, characterized in that: At the delivery pipeline leading out of the dosing tank and at the inlet of each equipment, a cooling treatment of a preset duration is performed when the control stability index Iw is within the first preset range.

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