An indirect air cooling circulating water system oxidation passivation anti-corrosion system and method

Abstract

This invention discloses an oxidation passivation corrosion prevention system and method for an indirect air-cooled circulating water system. The outlet of the condenser is connected to the inlet of the indirect air-cooled circulating water quality monitoring system and the inlet of the circulating water pump. The outlet of the circulating water pump is divided into two paths. One path is connected to the inlet of the circulating water flow regulating valve, and the other path is connected to the outlet of the circulating water flow regulating valve via a pipeline after passing through the inlet regulating valve, the circulating water purification device, and the outlet valve of the circulating water purification device. The outlet of the oxygen supply source is connected to the inlet of the indirect air-cooled tower via an oxygen supply pressure reducing valve, an oxygen supply flow regulating valve, and an oxygen supply outlet valve. The outlet of the chemical storage tank is connected to the inlet of the indirect air-cooled tower via a chemical metering pump and a chemical supply outlet valve. This system and method can maintain good water quality in the indirect air-cooled circulating water system while inhibiting corrosion.

Description

Technical Field

[0001] This invention belongs to the field of corrosion prevention of circulating water systems in indirect air-cooled power plants, and relates to an oxidation passivation corrosion prevention system and method for indirect air-cooled circulating water systems. Background Technology

[0002] The circulating water systems of indirect air-cooled power plants are extensive. Most indirect air-cooled systems use both iron circulating water pipes and aluminum heat dissipation pipes, while a few use all-iron materials. Although the makeup water for these systems is demineralized water, over time, most power plants experience corrosion due to deteriorating circulating water quality, leading to high iron and aluminum content in the circulating water and even corrosion and leaks in the iron and aluminum pipes. Currently, the main corrosion prevention method for indirect air-cooled circulating water systems is adding reducing corrosion inhibitors. However, investigations show that corrosion remains severe in most power plants even after adding these inhibitors. Furthermore, discharging circulating water with added inhibitors causes varying degrees of environmental pollution, and the cost of treating the related wastewater is very high.

[0003] Both iron and aluminum can be protected against corrosion in desalinated water environments through oxidation passivation. The corrosion protection effect is significant and no wastewater containing corrosion inhibitors is generated. Therefore, it is of great significance to develop an oxidation passivation corrosion protection system and method for an indirect air-cooled circulating water system. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an oxidation passivation and corrosion prevention system and method for an indirect air-cooled circulating water system. This system and method can maintain good water quality in the indirect air-cooled circulating water system while inhibiting corrosion.

[0005] To achieve the above objectives, this invention discloses an oxidation passivation and corrosion prevention system for an indirect air-cooled circulating water system, comprising a condenser, an indirect air-cooled circulating water quality monitoring system, a circulating water pump, a circulating water flow regulating valve, an inlet regulating valve for a circulating water purification device, a circulating water purification device, an outlet valve for a circulating water purification device, an indirect air-cooled tower, an oxygen supply source, an oxygen supply pressure reducing valve, an oxygen supply flow regulating valve, an oxygen supply outlet valve, a chemical storage tank, a chemical metering pump, and a chemical supply outlet valve.

[0006] The condenser outlet is connected to the inlet of the intercooled circulating water quality monitoring system and the inlet of the circulating water pump. The outlet of the circulating water pump is divided into two paths. One path is connected to the inlet of the circulating water flow regulating valve, and the other path is connected to the outlet of the circulating water flow regulating valve through a pipeline after passing through the circulating water purification device inlet regulating valve, the circulating water purification device, and the circulating water purification device outlet valve. The outlet of the oxygen supply is connected to the inlet of the indirect air-cooled tower through the oxygen supply pressure reducing valve, the oxygen supply flow regulating valve, and the oxygen supply outlet valve. The outlet of the chemical storage tank is connected to the inlet of the indirect air-cooled tower through the chemical metering pump and the chemical supply outlet valve. The outlet of the indirect air-cooled tower is connected to the condenser inlet.

[0007] It also includes a control device for the intercooled circulating water corrosion prevention system. The input end of the intercooled circulating water corrosion prevention system control device is connected to the output end of the intercooled circulating water quality monitoring system. The output end of the intercooled circulating water corrosion prevention system control device is connected to the control end of the circulating water flow regulating valve, the inlet regulating valve of the circulating water purification device, the oxygenation flow regulating valve, and the dosing metering pump.

[0008] This invention discloses an oxidation passivation corrosion prevention method for an indirect air-cooled circulating water system, comprising the following steps:

[0009] Open the outlet valve of the circulating water purification device, and adjust the opening of the circulating water flow regulating valve and the inlet regulating valve of the circulating water purification device to control the flow rate of the circulating water processed by the circulating water purification device.

[0010] The chloride ion content of the circulating water is detected by a chloride ion analyzer. When the chloride ion content of the circulating water is less than or equal to the chloride ion content threshold, the oxygenation outlet valve is opened. The oxygenation pressure reducing valve reduces the outlet pressure of the oxygenation source to the outlet pressure threshold. The opening of the oxygenation flow regulating valve is adjusted to control the amount of oxygen added. The oxygen content of the circulating water is detected by a dissolved oxygen analyzer and controlled to be greater than the oxygen content threshold.

[0011] Open the dosing outlet valve, control the dosage of alkalizing agent by adjusting the frequency of the dosing metering pump, add the alkalizing agent from the chemical storage tank into the circulating water, detect the pH value of the circulating water with a pH analyzer, and control the dosage of alkalizing agent accordingly.

[0012] When the chloride ion content measured by the chloride ion analyzer is greater than the chloride ion content threshold, the oxygen supply outlet valve is closed and oxygen supply is stopped until the chloride ion content is less than or equal to the chloride ion content threshold.

[0013] The threshold for chloride ion content is 3 μg / L; the threshold for oxygen content is 15 μg / L.

[0014] When the condenser is a surface condenser, the alkalizing agent is ammonia or sodium hydroxide.

[0015] When the condenser is a mixed condenser, the alkalizing agent is ammonia.

[0016] The outlet pressure threshold is 0.5–2.0 MPa.

[0017] For indirect air-cooled towers made of aluminum, open the dosing outlet valve, control the dosage of alkalizing agent by adjusting the frequency of the dosing metering pump, add the alkalizing agent from the chemical storage tank to the circulating water, detect the pH value of the circulating water with a pH analyzer, and control the dosage of alkalizing agent to make the pH value of the circulating water 8.0 to 8.5.

[0018] For indirect air-cooled towers made entirely of iron, open the dosing outlet valve, control the dosage of alkalizing agent by adjusting the frequency of the dosing metering pump, add the alkalizing agent from the chemical storage tank to the circulating water, and use a pH analyzer to detect the pH value of the circulating water to control the dosage of alkalizing agent so that the pH value of the circulating water is 8.5 to 9.0.

[0019] The circulating water purification device includes a filtration section and an ion exchange section. The number of filtration and ion exchange sections is designed according to the bypass treatment flow rate.

[0020] In an indirect air-cooled circulating water system, the makeup water is demineralized water, and the conductivity of the makeup water should be ≤0.4μS / cm.

[0021] The present invention has the following beneficial effects:

[0022] In specific operation, the indirect air-cooled circulating water system oxidation passivation corrosion prevention system and method of the present invention forms a passivation film on the surface of iron and aluminum by adding oxygen, which effectively prevents corrosion of the metal substrate. The corrosion prevention effect is significant, and there is no need to add corrosion inhibitors to the circulating water, and no wastewater containing corrosion inhibitors is generated. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the present invention.

[0024] Among them, 1 is the condenser, 2 is the intercooled circulating water quality monitoring system, 3 is the dissolved oxygen analyzer, 4 is the chloride ion analyzer, 5 is the pH analyzer, 6 is the intercooled circulating water anti-corrosion system control device, 7 is the circulating water pump, 8 is the circulating water flow regulating valve, 9 is the circulating water purification device inlet regulating valve, 10 is the circulating water purification device, 11 is the circulating water purification device outlet valve, 12 is the oxygen supply outlet valve, 13 is the oxygen supply flow regulating valve, 14 is the oxygen supply pressure reducing valve, 15 is the oxygen supply source, 16 is the chemical dosing outlet valve, 17 is the chemical dosing metering pump, 18 is the chemical storage tank, and 19 is the indirect air-cooled tower. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, not all embodiments, and are not intended to limit the scope of the present invention. Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion regarding the concepts disclosed in the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0026] The accompanying drawings show structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not drawn to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0027] refer to Figure 1 The indirect air-cooled circulating water system oxidation passivation corrosion prevention system of the present invention includes an indirect air-cooled circulating water quality monitoring system 2, a circulating water purification device 10, a circulating water purification device inlet regulating valve 9, a circulating water purification device outlet valve 11, a circulating water flow regulating valve 8, an oxygenation outlet valve 12, an oxygenation flow regulating valve 13, an oxygenation pressure reducing valve 14, an oxygenation source 15, a chemical dosing outlet valve 16, a chemical dosing metering pump 17, a chemical storage tank 18, and an indirect air-cooled circulating water corrosion prevention system control device 6. It also includes a condenser 1, a circulating water pump 7, and an indirect air-cooled tower 19. The indirect air-cooled circulating water quality monitoring system 2 includes a dissolved oxygen analyzer 3, a chloride ion analyzer 4, and a pH analyzer 5.

[0028] The outlet of condenser 1 is connected to the inlet of the intercooled circulating water quality monitoring system 2 and the inlet of the circulating water pump 7. The outlet of the circulating water pump 7 is divided into two paths. One path is connected to the inlet of the circulating water flow regulating valve 8, and the other path is connected to the outlet of the circulating water flow regulating valve 8 through the circulating water purification device inlet regulating valve 9, the circulating water purification device 10 and the circulating water purification device outlet valve 11, and then connected to the inlet of the indirect air-cooled tower 19 through a pipeline. The outlet of the oxygen supply source 15 is connected to the inlet of the indirect air-cooled tower 19 through the oxygen supply pressure reducing valve 14, the oxygen supply flow regulating valve 13 and the oxygen supply outlet valve 12. The outlet of the chemical storage tank 18 is connected to the inlet of the indirect air-cooled tower 9 through the chemical metering pump 17 and the chemical supply outlet valve 16. The outlet of the indirect air-cooled tower 19 is connected to the inlet of condenser 1.

[0029] The input end of the intercooled circulating water corrosion prevention system control device 6 is connected to the output end of the intercooled circulating water quality monitoring system 2. The output end of the intercooled circulating water corrosion prevention system control device 6 is connected to the control end of the circulating water flow regulating valve 9, the circulating water purification device inlet regulating valve 9, the oxygenation flow regulating valve 13, and the dosing metering pump 17.

[0030] refer to Figure 1 The oxidation passivation and corrosion prevention method for an indirect air-cooled circulating water system according to the present invention includes the following steps:

[0031] Open the outlet valve 11 of the circulating water purification device, and adjust the opening of the circulating water flow regulating valve 8 and the inlet regulating valve 9 of the circulating water purification device to control the flow rate of the circulating water treated by the circulating water purification device 10. Since the circulating water flow rate is large, in order to improve the water purification efficiency, the bypass treatment flow rate should be at least 1 / 10 of the total flow rate of the intercooled circulating water.

[0032] The chloride ion content of the circulating water is detected by the chloride ion analyzer 4. When the chloride ion content of the circulating water is ≤3μg / L, the oxygen outlet valve 12 is opened, and the outlet pressure of the oxygen source 15 is reduced to 0.5~2.0MPa by the oxygen pressure reducing valve 14. The opening degree of the oxygen flow regulating valve 13 is adjusted to control the oxygen supply. The oxygen content of the circulating water is detected by the dissolved oxygen analyzer 3 and controlled to be >15μg / L.

[0033] While adding oxygen for corrosion prevention in the indirect air-cooled circulating water system, an appropriate amount of alkalizing agent can also be added to assist in corrosion prevention. For the indirect air-cooled tower 19 made of aluminum, open the dosing outlet valve 16, and control the dosing amount of alkalizing agent by adjusting the frequency of the dosing metering pump 17. Add the alkalizing agent from the chemical storage tank 18 to the circulating water, and use the pH analyzer 5 to detect the pH value of the circulating water to control the amount of alkalizing agent added, so that the pH value of the circulating water is 8.0 to 8.5.

[0034] For the indirect air-cooled tower 19 made entirely of iron, open the dosing outlet valve 16, control the dosing amount of alkalizing agent by adjusting the frequency of the dosing metering pump 17, add the alkalizing agent from the chemical storage tank 18 to the circulating water, and use the pH analyzer 5 to detect the pH value of the circulating water in order to control the dosing amount of alkalizing agent so that the pH value of the circulating water is 8.5 to 9.0.

[0035] When the chloride ion content measured by the chloride ion analyzer 4 is >3μg / L, the oxygen outlet valve 12 is closed to stop oxygen supply until the chloride ion content is ≤3μg / L, at which point oxygen supply is resumed.

[0036] The circulating water purification device 10 includes a filtration section and an ion exchange section. The filtration section can be a tubular filter or a powder resin filter, etc., and the ion exchange section can be a cation bed + decarbonator + anion bed or a cation bed + decarbonator + mixed bed, etc. The ion exchange section is also equipped with a resin regeneration system. The number of filtration and ion exchange sections is designed according to the bypass treatment flow rate, and can be one or more sets.

[0037] For the indirect air-cooling system of the surface condenser 1, the alkalizing agent can be ammonia, sodium hydroxide or other strong alkaline alkalizing agents; for the indirect air-cooling system of the mixed condenser 1, the alkalizing agent is ammonia.

[0038] The makeup water for an indirect air-cooled circulating water system should be demineralized water, and the conductivity of the makeup water should be ≤0.4μS / cm.

[0039] Example 1

[0040] The oxidation passivation and corrosion prevention method for an indirect air-cooled circulating water system according to the present invention includes the following steps:

[0041] For a 600MW unit, the circulating water piping is made of iron, the heat exchange tubes of the indirect air-cooled tower 19 are made of aluminum, and an indirect air-cooling system using a surface condenser 1 is employed. The outlet valve 11 of the circulating water purification device is opened, and the opening of the circulating water flow regulating valve 8 and the inlet regulating valve 9 of the circulating water purification device are adjusted to control the flow rate of the circulating water treated by the circulating water purification device 10 to 5000t / h. In the circulating water purification device 10, the bypass circulating water sequentially passes through a tubular filter, a cation exchange bed, a decarbonizer, and a mixed bed. The circulating water purification device 10 is equipped with four parallel bypass purification systems, three in operation and one on standby. The maximum processing capacity of a single purification system is 2000t / h.

[0042] The chloride ion content of the circulating water is detected by chloride ion analyzer 4. When the chloride ion content is ≤3μg / L, the oxygen outlet valve 12 is opened, and the outlet pressure of the oxygen source 15 is reduced to 1.0MPa by oxygen pressure reducing valve 14. The opening of the oxygen flow regulating valve 13 is adjusted, and the oxygen content of the circulating water is detected by dissolved oxygen analyzer 3. The oxygen content of the circulating water is controlled to be >15μg / L.

[0043] Open the dosing outlet valve 16, adjust the frequency of the dosing metering pump 17 to control the amount of ammonia added, add the ammonia water from the chemical storage tank 18 to the circulating water, detect the pH value of the circulating water with the pH analyzer 5, and control the amount of ammonia added so that the pH value of the circulating water is between 8.0 and 8.5.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An oxidation passivation corrosion prevention method for an indirect air-cooling circulating water system, characterized by, The indirect air cooling circulating water system oxidation passivation corrosion prevention system comprises a condenser (1), an indirect air cooling circulating water quality monitoring system (2), a circulating water pump (7), a circulating water flow regulating valve (8), a circulating water purification device inlet regulating valve (9), a circulating water purification device (10), a circulating water purification device outlet valve (11), an indirect air cooling tower (19), an oxygen adding gas source (15), an oxygen adding pressure reducing valve (14), an oxygen adding flow regulating valve (13), an oxygen adding outlet valve (12), a chemical liquid storage tank (18), a chemical adding metering pump (17), and a chemical adding outlet valve (16). The outlet of the condenser (1) is in communication with the inlet of the indirect air cooling circulating water quality monitoring system (2) and the inlet of the circulating water pump (7). The outlet of the circulating water pump (7) is divided into two routes. One route is in communication with the inlet of the circulating water flow regulating valve (8), and the other route is in communication with the outlet of the circulating water flow regulating valve (8) through a pipeline after the circulating water purification device inlet regulating valve (9), the circulating water purification device (10), and the circulating water purification device outlet valve (11), and then is in communication with the inlet of the indirect air cooling tower (19). The outlet of the oxygen adding gas source (15) is in communication with the inlet of the indirect air cooling tower (19) through the oxygen adding pressure reducing valve (14), the oxygen adding flow regulating valve (13), and the oxygen adding outlet valve (12). The outlet of the chemical liquid storage tank (18) is in communication with the inlet of the indirect air cooling tower (19) through the chemical adding metering pump (17) and the chemical adding outlet valve (16). The outlet of the indirect air cooling tower (19) is in communication with the inlet of the condenser (1). The indirect air cooling circulating water corrosion prevention system control device (6) is further included. The input end of the indirect air cooling circulating water corrosion prevention system control device (6) is connected with the output end of the indirect air cooling circulating water quality monitoring system (2). The output end of the indirect air cooling circulating water corrosion prevention system control device (6) is connected with the control ends of the circulating water flow regulating valve (8), the circulating water purification device inlet regulating valve (9), the oxygen adding flow regulating valve (13), and the chemical adding metering pump (17). The method comprises the following steps: The circulating water purification device outlet valve (11) is opened. The opening degree of the circulating water flow regulating valve (8) and the circulating water purification device inlet regulating valve (9) is adjusted to control the flow of the circulating water treated by the circulating water purification device (10). The chlorine ion content of the circulating water is detected by the chlorine ion analyzer (4). When the chlorine ion content of the circulating water is less than or equal to the chlorine ion content threshold value, the oxygen adding outlet valve (12) is opened. The outlet gas pressure of the oxygen adding gas source (15) is reduced to the outlet gas pressure threshold value by the oxygen adding pressure reducing valve (14). The opening degree of the oxygen adding flow regulating valve (13) is adjusted to control the oxygen adding amount. The oxygen content of the circulating water is detected by the dissolved oxygen analyzer (3) to control the oxygen content of the circulating water to be greater than the oxygen content threshold value. The chemical adding outlet valve (16) is opened. The frequency of the chemical adding metering pump (17) is adjusted to control the chemical adding amount of the alkalizing agent. The alkalizing agent in the chemical liquid storage tank (18) is added into the circulating water. The pH value of the circulating water is detected by the pH analyzer (5) to control the chemical adding amount of the alkalizing agent. When the chloride ion content measured by the chloride ion analyzer (4) is greater than the chloride ion content threshold value, the oxygen addition outlet valve (12) is closed to stop oxygen addition until the chloride ion content is less than or equal to the chloride ion content threshold value; For the indirect air cooling tower (19) made of aluminum, the dosing outlet valve (16) is opened, the dosing amount of the alkalizing agent is controlled by adjusting the frequency of the dosing metering pump (17), the alkalizing agent in the chemical liquid storage tank (18) is added to the circulating water, the pH value of the circulating water is detected by the pH analyzer (5), and the dosing amount of the alkalizing agent is controlled to make the pH value of the circulating water be 8.0-8.5; For the indirect air cooling tower (19) made of all-iron material, the dosing outlet valve (16) is opened, the dosing amount of the alkalizing agent is controlled by adjusting the frequency of the dosing metering pump (17), the alkalizing agent in the chemical liquid storage tank (18) is added to the circulating water, the pH value of the circulating water is detected by the pH analyzer (5), and the dosing amount of the alkalizing agent is controlled to make the pH value of the circulating water be 8.5-9.

0.

2. The oxidation passivation corrosion prevention method for an indirect air-cooling circulating water system according to claim 1, characterized by, The chloride ion content threshold value is 3 μg / L; the oxygen content threshold value is 15 μg / L.

3. The method of claim 1, wherein the method is characterized by: When the condenser (1) is a surface type condenser, the alkalizing agent is ammonia or sodium hydroxide.

4. The method of claim 1, wherein the method is characterized by: When the condenser (1) is a mixed type condenser, the alkalizing agent is ammonia.

5. The method of claim 1, wherein the method is characterized by: The outlet gas pressure threshold value is 0.5-2.0 MPa.

6. The method of claim 1, wherein the method is characterized by: The circulating water purification device (10) comprises a filtering part and an ion exchange part, and the number of the filtering part and the ion exchange part is designed according to the bypass treatment flow rate; The make-up water of the circulating water in the indirect air cooling circulating water system is desalted water, and the conductivity of the make-up water should be ≤0.4 μS / cm.

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