Air-cooled island flow-accelerated corrosion simulation test system and method

Abstract

The application discloses a kind of air cooling island flow accelerated corrosion simulation test system and method, main loop subsystem, including high-purity water tank, main loop outlet pipe, electrode flow cell and main loop return pipe;The water outlet of high-purity water tank is connected with the one end of main loop outlet pipe, the other end of main loop outlet pipe is connected with the water inlet of electrode flow cell, the one end of main loop return pipe is connected with the water outlet of electrode flow cell, the other end of main loop return pipe is connected with the backwater of high-purity water tank;Dosing subsystem is used to add alkali agent or oxidizing agent to main loop outlet pipe;Flow accelerated corrosion test subsystem includes test electrode and corrosion tester;Test electrode is placed in electrode flow cell, and test electrode is connected with the input end of corrosion tester by wire;The material of test electrode is the same as the material of the equipment to be simulated air cooling island;The application realizes the real simulation of air cooling island equipment, meets the simulation of high flow rate and anaerobic condition, and the error of simulation test result is small.

Description

Technical Field

[0001] This invention belongs to the field of flow-accelerated corrosion testing technology, and specifically relates to a flow-accelerated corrosion simulation test system and method for air-cooled islands. Background Technology

[0002] Air-cooled islands are used to cool the high-temperature exhaust steam from steam turbines in thermal power units, and they are widely used in coal-rich and water-scarce regions. Currently, the main material for constructing air-cooled islands is carbon steel, which is extremely susceptible to corrosion in high-temperature dissolved oxygen water environments. In particular, the accelerated corrosion caused by single-phase or gas-liquid two-phase flow (FAC) of the air-cooled island due to steam turbine exhaust is especially severe.

[0003] Theoretical calculations show that in ultra-supercritical direct air-cooled units, the exhaust steam velocity of the turbine can reach over 60 m / s, and the surface liquid phase or liquid film velocity of the main exhaust pipe is over 15 m / s. Under high-velocity wet steam or liquid film, the Fe3O4 oxide film formed on the inner surface of carbon steel will continue to dissolve, causing the iron content in the unit's water-steam system to exceed the standard, resulting in corrosion and deposition of carbon steel components in the air-cooled island. Among them, the wall thickness of the air-cooled heat dissipation tubes is mostly 1.5 mm. Long-term operational corrosion may lead to local thinning failure, causing air or pollutants to leak in. On the one hand, this will cause an increase in turbine back pressure or water-steam quality pollution, and on the other hand, it will lead to high-temperature steam leakage, posing a significant threat to the safety of life and property in the surrounding area.

[0004] Currently, research on flow-accelerated corrosion in air-cooled islands is still in its early stages. Existing simulation devices cannot simulate high flow rates and oxygen-free conditions, resulting in significant errors in the simulation results. Therefore, there is an urgent need to provide a flow-accelerated corrosion simulation system for air-cooled islands to realistically simulate corrosion conditions, explore its corrosion mechanism, and reduce or inhibit corrosion. This has significant theoretical and practical implications for protecting thermal equipment and increasing the cycle water production of fine-treatment mixed beds. Summary of the Invention

[0005] In view of the technical problems existing in the prior art, the present invention provides an air-cooled island flow accelerated corrosion simulation test system and method to solve the technical problem that existing simulation test devices cannot simulate high flow rate and oxygen-free conditions, thus leading to large errors in the simulation test results.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a flow-accelerated corrosion simulation test system for air-cooled islands, including a main loop subsystem, a chemical dosing subsystem, and a flow-accelerated corrosion testing subsystem;

[0008] The main circuit subsystem includes a high-purity water tank, a main circuit outlet pipe, an electrode flow cell, and a main circuit return pipe. The high-purity water tank stores high-purity water. The outlet of the high-purity water tank is connected to one end of the main circuit outlet pipe, and the other end of the main circuit outlet pipe is connected to the inlet of the electrode flow cell. One end of the main circuit return pipe is connected to the outlet of the electrode flow cell, and the other end of the main circuit return pipe is connected to the return port of the high-purity water tank.

[0009] The dosing subsystem is used to add an alkalizing agent or an oxidizing agent into the main circuit outlet pipe;

[0010] The flow-accelerated corrosion testing subsystem includes a test electrode and a corrosion tester; the test electrode is placed in the electrode flow cell and connected to the input terminal of the corrosion tester via a wire; wherein the material of the test electrode is the same as the material of the equipment to be simulated in the air-cooled island; the corrosion tester is used to collect the polarization resistance of the test electrode.

[0011] Furthermore, it also includes a deoxygenation subsystem; the deoxygenation subsystem includes a gas source; the gas source stores inert gas, and the outlet of the gas source is divided into three branches; wherein, the first branch is connected to the high-purity water tank, the second branch is connected to the dosing subsystem, and the third branch is connected to the electrode flow cell.

[0012] Furthermore, it also includes an online monitoring subsystem; the online monitoring subsystem includes a cooler, a first sampling shut-off valve, a first three-way valve, a hydrogen exchange column, a conductivity meter, a second three-way valve, a second sampling shut-off valve, and a dissolved oxygen meter;

[0013] The inlet end of the cooler is connected to the main circuit outlet pipe; the outlet end of the cooler is divided into two paths, one of which is connected to one end of the first sampling shut-off valve, and the other is connected to one end of the second sampling shut-off valve.

[0014] The other end of the first sampling shut-off valve is connected to the first port of the first three-way valve, and the second end of the first three-way valve is connected to the inlet of the hydrogen exchange column; the third port of the first three-way valve and the outlet of the hydrogen exchange column are both connected to the inlet of the conductivity meter, and the outlet of the conductivity meter is connected to the first port of the second three-way valve; the second port of the second three-way valve is connected to the main circuit return water pipe, and the third port of the second three-way valve serves as a manual sampling port.

[0015] The other end of the second sampling shut-off valve is connected to the inlet end of the dissolved oxygen meter, and the outlet end of the dissolved oxygen meter is connected to the main circuit return water pipe.

[0016] Furthermore, it also includes a bypass recirculation subsystem; the bypass recirculation subsystem includes a bypass recirculation ball valve and a bypass pipe; one end of the bypass pipe is connected to the main circuit outlet pipe, and the other end of the bypass pipe is connected to the main circuit return pipe; the bypass recirculation ball valve is installed on the bypass pipe.

[0017] Furthermore, it also includes a purification subsystem; the purification subsystem includes a mixed bed sampling shut-off valve and a mixed bed; one end of the mixed bed sampling shut-off valve is connected to the main circuit outlet pipe, the other end of the mixed bed sampling shut-off valve is connected to the inlet end of the mixed bed, and the outlet end of the mixed bed is connected to the main circuit return pipe.

[0018] Furthermore, the dosing subsystem includes a first dosing tank, a second dosing tank, and a dosing pipeline; the first dosing tank is used to store an alkalizing agent, and the second dosing tank is used to store an oxidizing agent; the outlet end of the first dosing tank and the outlet end of the second dosing tank are both connected to one end of the dosing pipeline, and the other end of the dosing pipeline is connected to the main circuit outlet pipe.

[0019] Furthermore, the electrode flow cell includes a 180° electrode flow cell and a 90° electrode flow cell; the 180° electrode flow cell and the 90° electrode flow cell are connected in parallel between the main circuit outlet pipe and the main circuit return pipe; the 180° electrode flow cell is provided with a first test electrode, and the 90° electrode flow cell is provided with a second test electrode; wherein, both the first test electrode and the second test electrode include a working electrode, a reference electrode, and an auxiliary electrode of the same material and model, and the working electrode, the reference electrode, and the auxiliary electrode are respectively connected to the corrosion tester through wires.

[0020] Furthermore, the main circuit outlet pipe is also equipped with a fourth flow meter, a main circuit outlet pressure gauge, and a first temperature sensor; the fourth flow meter is used to monitor the flow rate of the water sample in the main circuit outlet pipe; the main circuit outlet pressure gauge is used to monitor the pressure of the water sample in the main circuit outlet pipe; the first temperature sensor is located at the inlet of the electrode flow cell and is used to monitor the temperature of the water sample at the inlet of the electrode flow cell.

[0021] A second temperature sensor is also installed on the main circuit return water pipe. The second temperature sensor is located at the outlet of the electrode flow cell. The second temperature sensor is used to monitor the temperature information of the water sample at the outlet of the electrode flow cell.

[0022] Furthermore, the operating environment characteristics of the air-cooled island flow accelerated corrosion simulation test system are as follows: temperature 50-70℃, flow rate 15-25m / s, hydrogen conductivity less than 0.15μS / cm, and dissolved oxygen value less than 5μg / L.

[0023] This invention also provides a method for simulating accelerated corrosion in an air-cooled island, utilizing the aforementioned air-cooled island accelerated corrosion simulation system; wherein, the simulation method includes the following steps:

[0024] Step 1: Using the dosing subsystem, add an alkalizing agent or oxidizing agent to the main loop outlet pipe to bring the hydrogen conductivity or dissolved oxygen value of the water sample in the main loop outlet pipe and the main loop return pipe to the design range.

[0025] Step 2: Turn on the corrosion tester and record the polarization resistance of the test electrode;

[0026] Step 3: Determine the corrosion result of the test electrode based on the polarization resistance of the test electrode, and then obtain the results of the air-cooled island flow-accelerated corrosion simulation test.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] This invention provides a system and method for simulating accelerated corrosion in air-cooled islands. An alkalizing agent or oxidizing agent is added to the main loop outlet pipe using a dosing subsystem to maintain the designed hydrogen conductivity or dissolved oxygen value of the water sample in the main loop pipe. This ensures the system operates in a stable environment, protecting the test electrodes in the electrode flow cell from interference and oxidation caused by dissolved oxygen in the system water sample, thus accurately reflecting the original state of the test electrodes. A corrosion testing instrument is used to monitor the polarization resistance of the test electrodes, and the corrosion status of the test electrodes is characterized based on the polarization resistance, achieving a realistic simulation of the air-cooled island equipment. The device has a simple structure, meets the requirements for simulating high flow rates and oxygen-free conditions, and the simulation test results have small errors.

[0029] Furthermore, the deoxygenation subsystem is connected to the high-purity water tank, the dosing subsystem, and the electrode flow cell to achieve multi-point deoxygenation, which effectively improves the deoxygenation effect. This ensures that the dissolved oxygen in the system loop is less than 5 μg / L, ensuring that the test electrode is not affected by dissolved oxygen in the water or oxidation, truly reflecting the original state of the electrode and reducing test errors.

[0030] Furthermore, by setting up an online monitoring subsystem, a cooler is used to cool the water sample taken from the main circuit outlet pipe, and the hydrogen conductivity and dissolved oxygen value of the water sample are monitored in real time using a conductivity meter and a dissolved oxygen meter, respectively, to provide data support for the operation of the dosing subsystem and ensure the reliability of the system operation; at the same time, a manual sampling port is set up to achieve the purpose of calibrating the online instruments or receiving water samples for testing.

[0031] Furthermore, a bypass recirculation ball valve is installed on the bypass pipe. By adjusting the opening of the bypass recirculation ball valve, the flow rate of the water sample in the electrode flow cell can be adjusted to meet the requirements of the accelerated corrosion simulation test of the flow channel at different flow rates, thereby obtaining corrosion performance test data at different flow rates.

[0032] Furthermore, by setting up a purification subsystem, which connects to a mixed bed, the purification treatment effect of the system water sample is achieved.

[0033] Furthermore, the dosing subsystem employs dual dosing tanks to allow for the separate addition of alkalizing agents and oxidizing agents, thereby improving the accuracy of dosing.

[0034] Furthermore, a 180° electrode flow cell was used to simulate the 180° straight pipe of the air-cooled island, and a 90° electrode flow cell was used to simulate the 90° bend of the air-cooled island, achieving the most realistic simulation of the on-site working conditions of the air-cooled island and ensuring the authenticity of the simulation test. Secondly, the test electrode adopts a three-electrode combination of working electrode, reference electrode and auxiliary electrode, which effectively eliminates the influence of pure water resistance on electrochemical corrosion measurement. Attached Figure Description

[0035] Figure 1 This is a structural block diagram of the air-cooled island flow-accelerated corrosion simulation test system described in the embodiment;

[0036] Figure 2 This is a flowchart of the air-cooled island flow-accelerated corrosion simulation test method described in the embodiment;

[0037] Figure 3 The image shows electrode corrosion polarization curves at the same pH but different oxidant concentrations in the examples.

[0038] The components include: 1. High-purity water tank; 2. Automatic temperature controller; 3. Heater; 4. Exhaust port; 5. Drain port; 6. Water tank gas supply shut-off valve; 7. Water inlet; 8. Gas source; 9. Chemical dosing tank gas supply shut-off valve; 10. Electrode flow cell gas supply shut-off valve; 11. First chemical dosing tank; 12. Second chemical dosing tank; 13. Chemical dosing shut-off valve; 14. Magnetic pump; 15. Cooler; 16. First sampling shut-off valve; 17. First flow meter; 18. First three-way valve; 19. Hydrogen exchange column; 20. Conductivity... Table 21 Second three-way valve, 22 Second sampling shut-off valve, 23 Second flow meter, 24 Dissolved oxygen meter, 25 Mixed bed sampling shut-off valve, 26 Third flow meter, 27 Mixed bed, 28 Bypass recirculation ball valve, 29 Main circuit outlet ball valve, 30 Fourth flow meter, 31 First inlet shut-off valve, 32 Second inlet shut-off valve, 33 Main circuit bypass ball valve, 34 Corrosion tester, 35 180° electrode flow cell, 36 First test electrode, 37 90° electrode flow cell, 38 Second test electrode, 39 Main circuit return water ball valve, 40 Water tank pressure gauge; 41 Main circuit outlet pressure gauge, 42 First temperature sensor, 43 Second temperature sensor, 44 Pressure reducing valve. Detailed Implementation

[0039] To make the technical problems solved by the present invention, the technical solutions, and the beneficial effects clearer, the following specific embodiments provide a further detailed description of the present invention. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.

[0040] This invention provides an air-cooled island flow-accelerated corrosion simulation test system, including a main loop subsystem, a deoxygenation subsystem, a chemical dosing subsystem, an online monitoring subsystem, a purification subsystem, a bypass recirculation subsystem, and a flow-accelerated corrosion testing subsystem.

[0041] In this invention, the main circuit subsystem includes a high-purity water tank 1, a main circuit outlet pipe, an electrode flow cell, a main circuit return pipe, a fourth flow meter 30, a main circuit outlet pressure gauge 41, a first temperature sensor 42, and a second temperature sensor 43. The high-purity water tank 1 stores high-purity water. The outlet of the high-purity water tank 1 is connected to one end of the main circuit outlet pipe, and the other end of the main circuit outlet pipe is connected to the inlet of the electrode flow cell. One end of the main circuit return pipe is connected to the outlet of the electrode flow cell, and the other end of the main circuit return pipe is connected to the return outlet of the high-purity water tank 1. The electrode flow cell includes a 180° electrode flow cell 35 and a 90° electrode flow cell 37. The 180° electrode flow cell 35 and the 90° electrode flow cell 37 are connected in parallel between the main circuit outlet pipe and the main circuit return pipe.

[0042] The fourth flow meter 30, the main circuit outlet pressure gauge 41, and the first temperature sensor 42 are all installed on the main circuit outlet pipe. The fourth flow meter 30 monitors the flow rate of the water sample in the main circuit outlet pipe. The main circuit outlet pressure gauge 41 monitors the pressure of the water sample in the main circuit outlet pipe. The first temperature sensor 42 is located at the inlet of the electrode flow cell and monitors the temperature of the water sample at the inlet of the electrode flow cell. The second temperature sensor 43 is installed on the main circuit return pipe and is located at the outlet of the electrode flow cell. The second temperature sensor 43 monitors the temperature of the water sample at the outlet of the electrode flow cell.

[0043] In this invention, the deoxygenation subsystem includes a gas source 8; the gas source 8 stores an inert gas, which is nitrogen or other inert gas; the outlet of the gas source 8 is divided into three branches; wherein, the first branch is connected to the high-purity water tank 1, the second branch is connected to the dosing subsystem, and the third branch is connected to the electrode flow cell.

[0044] In this invention, the dosing subsystem is used to add an alkalizing agent or an oxidizing agent into the main circuit outlet pipe; the dosing subsystem includes a first dosing tank 11, a second dosing tank 12, and a dosing pipeline; the first dosing tank 11 is used to store the alkalizing agent, and the second dosing tank 12 is used to store the oxidizing agent; the outlet end of the first dosing tank 11 and the outlet end of the second dosing tank 12 are both connected to one end of the dosing pipeline, and the other end of the dosing pipeline is connected to the main circuit outlet pipe.

[0045] In this invention, the online monitoring subsystem includes a cooler 15, a first sampling shut-off valve 16, a first three-way valve 18, a hydrogen exchange column 19, a conductivity meter 20, a second three-way valve 21, a second sampling shut-off valve 22, and a dissolved oxygen meter 24. The inlet of the cooler 15 is connected to the main circuit outlet pipe. The outlet of the cooler 15 is divided into two paths, one of which is connected to one end of the first sampling shut-off valve 16, and the other is connected to one end of the second sampling shut-off valve 22. The other end of the first sampling shut-off valve 16 is connected to the first port of the first three-way valve 18. The second end of valve 18 is connected to the inlet end of hydrogen exchange column 19; the third port of the first three-way valve 18 and the outlet end of hydrogen exchange column 19 are both connected to the inlet end of conductivity meter 21, and the outlet end of conductivity meter 21 is connected to the first port of second three-way valve 21; the second port of second three-way valve 21 is connected to the main circuit return water pipe, and the third port of second three-way valve 21 serves as a manual sampling port; the other end of the second sampling shut-off valve 22 is connected to the inlet end of dissolved oxygen meter 24, and the outlet end of dissolved oxygen meter 24 is connected to the main circuit return water pipe.

[0046] In this invention, the purification subsystem includes a mixed bed sampling shut-off valve 25 and a mixed bed 27; one end of the mixed bed sampling shut-off valve 25 is connected to the main circuit outlet pipe, the other end of the mixed bed sampling shut-off valve 25 is connected to the inlet end of the mixed bed 27, and the outlet end of the mixed bed 27 is connected to the main circuit return pipe.

[0047] In this invention, the bypass recirculation subsystem includes a bypass recirculation ball valve 28 and a bypass pipe; one end of the bypass pipe is connected to the main circuit outlet pipe, and the other end of the bypass pipe is connected to the main circuit return pipe; the bypass recirculation ball valve 28 is mounted on the bypass pipe.

[0048] The accelerated corrosion testing subsystem includes a test electrode and a corrosion tester 34. The test electrode is placed in the electrode flow cell and connected to the input terminal of the corrosion tester 34 via a wire. The material of the test electrode is the same as that of the equipment in the simulated air-cooled island. The corrosion tester 34 is used to collect the polarization resistance of the test electrode. The test electrode includes a first test electrode 36 and a second test electrode 38. The first test electrode is disposed in the 180° electrode flow cell 35, and the second test electrode 38 is disposed in the 90° electrode flow cell 37. Preferably, both the first test electrode 36 and the second test electrode 38 include a working electrode, a reference electrode, and an auxiliary electrode of the same material and model. The working electrode, the reference electrode, and the auxiliary electrode are connected to the corrosion tester 34 via wires.

[0049] Working principle and test methods:

[0050] This invention provides a method for simulating accelerated corrosion in air-cooled islands, comprising the following steps:

[0051] Step 1: Using the deoxygenation subsystem, inert gas is introduced into the high-purity water tank 1, the dosing subsystem, and the electrode flow cell, respectively. The purification subsystem is turned on to purify the water sample in the system so that the dissolved oxygen value in the system is less than 5 μg / L and the temperature is maintained at 50-70℃. When the hydrogen conductivity is less than 0.15 μS / cm, the purification subsystem is turned off.

[0052] Step 2: Activate the dosing subsystem and add an alkalizing agent or oxidizing agent to the main circuit outlet pipe to bring the hydrogen conductivity or dissolved oxygen value of the water sample in the main circuit outlet pipe and the main circuit return pipe to the design range; wherein, the design range is: the direct conductivity reading of the water sample in the system is 2.2 to 5.4 μS / cm, and the concentration of the alkalizing agent in the water sample in the system is 0 to 2 mg / L.

[0053] Step 3: Turn on the corrosion tester 34 and record the polarization resistance of the test electrode.

[0054] Step 4: Determine the corrosion result of the test electrode based on the polarization resistance of the test electrode, and then obtain the results of the air-cooled island flow-accelerated corrosion simulation test.

[0055] Step 5: Activate the bypass recirculation subsystem to clean the system until the hydrogen conductivity of the water sample in the system is less than 0.15 μS / cm.

[0056] The air-cooled island flow accelerated corrosion simulation test system and method described in this invention utilizes a dosing subsystem to inject an alkalizing agent or oxidizing agent into the main loop outlet pipe. This maintains the designed hydrogen conductivity or dissolved oxygen value of the water sample in the main loop pipe, ensuring the system operates in a stable environment. This protects the test electrodes in the electrode flow cell from interference and oxidation caused by dissolved oxygen in the system water sample, thus accurately reflecting the original state of the test electrodes. A corrosion tester monitors the polarization resistance of the test electrodes, and the corrosion status of the test electrodes is characterized based on the polarization resistance, achieving a realistic simulation of the air-cooled island equipment. The device has a simple structure, meets the requirements for simulating high flow rates and oxygen-free conditions, and the simulation test results have small errors.

[0057] Example

[0058] As attached Figure 1As shown, this embodiment provides a flow-accelerated corrosion simulation test system for an air-cooled island. The operating environment characteristics of the simulation test system are: temperature of 50-70℃, flow rate of 15-25m / s, hydrogen conductivity of less than 0.15μS / cm, and dissolved oxygen value of less than 5μg / L. The air-cooled island flow-accelerated corrosion simulation test system includes a main loop subsystem, a deoxygenation subsystem, a chemical dosing subsystem, an online monitoring subsystem, a purification subsystem, a bypass recirculation subsystem, and a flow-accelerated corrosion testing subsystem.

[0059] In this embodiment, the main circuit subsystem includes a high-purity water tank 1, a main circuit outlet pipe, a magnetic pump 14, a main circuit outlet ball valve 29, a fourth flow meter 30, a first inlet pipe, a first inlet shut-off valve 31, a second inlet pipe, a second inlet shut-off valve 32, a main circuit bypass pipe, a main circuit bypass ball valve 33, a 180° electrode flow cell 35, a 90° electrode flow cell 37, a main circuit return pipe, a main circuit return ball valve 39, a main circuit outlet pressure gauge 41, a first temperature sensor 42, and a second temperature sensor 43.

[0060] The high-purity water tank 1 is a hollow box structure used to store high-purity water. The high-purity water tank 1 is equipped with an exhaust port 4, a drain port 5, a water inlet 7, a water outlet, and a return port. The exhaust port 4 is connected to the outside environment for venting air from the high-purity water tank 1. The water inlet 7 is connected to a high-purity water source for injecting high-purity water into the high-purity water tank 1. A water tank pressure gauge 40 is also installed on the top of the high-purity water tank 1 for monitoring the pressure information inside the high-purity water tank 1. The drain port 5 is used to drain water samples from the high-purity water tank 1. The high-purity water tank 1 is equipped with an automatic temperature controller 2 located on its lower left side. The automatic temperature controller 2 is connected to the control terminal of the heater 3. The automatic temperature controller 2 is used to monitor the temperature information of the water sample in the high-purity water tank 1 and generate a heater operation command based on the temperature information of the water sample in the high-purity water tank 1. The heater 3 is installed on the inner wall of the high-purity water tank 1 and is used to heat the water sample in the high-purity water tank 1. The water outlet is connected to the inlet end of the main circuit water outlet pipe, and the water return port is connected to the outlet end of the main circuit water return pipe.

[0061] The magnetic pump 14 and the main circuit outlet pressure gauge 41 are sequentially installed on the main circuit outlet pipe. The magnetic pump 14 is located near the end of the high-purity water tank 1, and the main circuit outlet pressure gauge 41 is located near the outlet end of the magnetic pump 14. The main circuit outlet pressure gauge 41 is used to monitor the pressure information of the water sample in the main circuit outlet pipe. The outlet end of the main circuit outlet pipe is divided into four outlet branches. The first outlet branch is connected to the cooler 15 in the online monitoring subsystem, the second outlet branch is connected to the mixed bed sampling shut-off valve 25 in the purification subsystem, the third outlet branch is connected to the bypass pipe in the bypass recirculation subsystem, and the fourth outlet branch is connected to the inlet end of the main circuit outlet ball valve 29.

[0062] The outlet end of the main circuit outlet ball valve 29 is connected to a main pipeline, and the outlet end of the main pipeline is connected to two test branch pipes and a main circuit bypass pipe. Specifically, the fourth flow meter 30 and the first temperature sensor 42 are sequentially installed on the main pipeline. The fourth flow meter 30 is used to monitor the flow rate of the water sample in the main circuit outlet pipe. The first temperature sensor 42 is used to monitor the temperature of the water sample at the inlet of the electrode flow cell. The inlet end of the main pipeline is connected to the outlet end of the main circuit outlet ball valve 29, and the outlet end of the main pipeline is divided into three branches. Among them, the first branch of the outlet end of the main pipeline is connected to the second branch pipe. One end of a test branch pipe is connected to the first test branch pipe, and the other end of the first test branch pipe is connected to the inlet end of the 90° electrode flow cell 37. The first inlet shut-off valve 31 is installed on the first test branch pipe. The second outlet end of the main pipeline is connected to one end of the second test branch pipe, and the other end of the second test branch pipe is connected to the inlet end of the 180° electrode flow cell 35. The second inlet shut-off valve 32 is installed on the second test branch pipe. The third outlet end of the main pipeline is connected to the inlet end of the main circuit bypass pipe, and the main circuit bypass ball valve 33 is installed on the main circuit bypass pipe.

[0063] The outlet end of the 180° electrode flow cell 35, the outlet end of the 90° electrode flow cell 37, and the outlet end of the main circuit bypass pipe are all connected to the inlet end of the main circuit return water pipe. The outlet end of the main circuit return water pipe is connected to the return water port of the high-purity water tank 1. The main circuit return water ball valve 39 and the second temperature sensor 43 are sequentially arranged on the main circuit return water pipe, with the main circuit return water ball valve 39 located near the end of the high-purity water tank 1, and the second temperature sensor 43 located near the ends of the 180° electrode flow cell 35 and the 90° electrode flow cell 37. The second temperature sensor 43 is used to monitor the temperature information of the water sample at the outlet of the 180° electrode flow cell 35 and the 90° electrode flow cell 37.

[0064] In this embodiment, there are two electrode flow pools: a 90° electrode flow pool 37 and a 180° electrode flow pool 35, both made of plexiglass. The structure of the 90° electrode flow pool 37 is adapted to the structure of a 90° bend in the air-cooled island to simulate the 90° bend in the air-cooled island. The structure of the 180° electrode flow pool 35 is adapted to the structure of a 180° straight pipe in the air-cooled island to simulate the flow-accelerated corrosion of the 180° straight pipe in the air-cooled island. The 90° electrode flow pool 37 and the 180° electrode flow pool 35 are connected in parallel between the main circuit outlet pipe and the main circuit return pipe. The flow channels in the 90° electrode flow pool 37 and the 180° electrode flow pool 35 are designed as slit structures to ensure that the flow velocity in the electrode flow pool is greater than 20 m / s, so as to simulate the flow-accelerated corrosion of the 90° bend and the 180° straight pipe under actual working conditions to the greatest extent.

[0065] In this embodiment, the deoxygenation subsystem includes a water tank gas supply shut-off valve 6, a gas source 8, a chemical dosing tank gas supply shut-off valve 9, an electrode flow cell gas supply shut-off valve 10, and a pressure reducing valve 44. The gas source 8 stores an inert gas, which is nitrogen or other inert gas. Preferably, the gas source 8 is an inert gas cylinder. The outlet of the gas source 8 is connected to the inlet of the pressure reducing valve 44, and the outlet of the pressure reducing valve 44 is divided into three paths. The first path of the outlet of the pressure reducing valve 44 is connected to the high-purity water through a first gas guide pipe. The tank 1 is connected, and the water tank gas supply shut-off valve 6 is installed on the first gas guide pipe, and the first gas guide pipe extends to the bottom of the high-purity water tank 1; the second outlet of the pressure reducing valve 44 is connected to the dosing subsystem through the second gas guide pipe, and the pressurized storage tank gas supply shut-off valve 9 is installed on the second gas guide pipe; the third outlet of the pressure reducing valve 44 is connected to both the first test branch pipe and the second test branch pipe through the third gas guide pipe, and the electrode flow cell gas supply shut-off valve 10 is installed on the third gas guide pipe.

[0066] In this embodiment, the dosing subsystem includes a first dosing tank 11, a second dosing tank 12, a dosing shut-off valve 13, and a dosing pipeline. The first dosing tank 11 is used to store an alkalizing agent, and the second dosing tank 12 is used to store an oxidizing agent. The outlet end of the second vent pipe is divided into two paths, one of which enters into the first dosing tank 11 and extends to the bottom of the first dosing tank 11, and the other of which enters into the second dosing tank 12 and extends to the bottom of the second dosing tank 12. The outlet ends of the first dosing tank 11 and the second dosing tank 12 are both connected to the inlet end of the dosing pipeline, and the outlet end of the dosing pipeline is connected to the main circuit water outlet pipe. The dosing shut-off valve 13 is located on the dosing pipeline, and the outlet end of the dosing pipeline is located on the side of the inlet end of the magnetic pump 14. The top of both the first dosing tank 11 and the second dosing tank 12 is provided with an exhaust port, which is connected to the outside.

[0067] In this embodiment, the online monitoring subsystem includes a cooler 15, a first sampling shut-off valve 16, a first flow meter 17, a first three-way valve 18, a hydrogen exchange column 19, a conductivity meter 20, a second three-way valve 21, a second sampling shut-off valve 22, a second flow meter 23, and a dissolved oxygen meter 24. The inlet end of the cooler 15 is connected to the first outlet branch of the main circuit outlet pipe, and the inlet end of the cooler 15 is located near the outlet end of the magnetic pump 14. The outlet end of the cooler 15 is divided into two paths, one of which is connected to one end of the first sampling shut-off valve 16, and the other is connected to one end of the second sampling shut-off valve 22. The other end of the first sampling shut-off valve 16 is connected to the first port of the first three-way valve 18, and the first flow meter 17 is located between the first sampling shut-off valve 16 and the first port of the first three-way valve 18. The second end of a three-way valve 18 is connected to the inlet end of the hydrogen exchange column 19. The third port of the first three-way valve 18 and the outlet end of the hydrogen exchange column 19 are both connected to the inlet end of the conductivity meter 21. The outlet end of the conductivity meter 21 is connected to the first port of the second three-way valve 21. The second port of the second three-way valve 21 is connected to the main circuit return water pipe, and the third port of the second three-way valve 21 serves as a manual sampling port. The other end of the second sampling shut-off valve 22 is connected to the inlet end of the dissolved oxygen meter 24. The second flow meter 23 is located between the second sampling shut-off valve 22 and the dissolved oxygen meter 24. The outlet end of the dissolved oxygen meter 24 is connected to the main circuit return water pipe. The second port of the second three-way valve 21 and the outlet end of the dissolved oxygen meter 24 are both located near the inlet end of the main circuit return water ball valve 39.

[0068] In this embodiment, the purification subsystem includes a mixed bed sampling shut-off valve 25, a third flow meter 26, and a mixed bed 27. One end of the mixed bed sampling shut-off valve 25 is connected to the second outlet branch of the main circuit outlet pipe, and the other end of the mixed bed sampling shut-off valve 25 is connected to the inlet end of the mixed bed 27. The outlet end of the mixed bed 27 is connected to the main circuit return water pipe. The third flow meter 26 is located between the mixed bed sampling shut-off valve 25 and the mixed bed 27. The outlet end of the mixed bed 27 is located near the inlet end of the main circuit return water ball valve 39. The mixed bed 27 contains anion and cation exchange resins for purifying water samples within the system. The inlet end of the mixed bed 27 is located at the bottom, and the outlet end of the mixed bed 27 is located at the top.

[0069] In this embodiment, the bypass in the circulation subsystem includes a bypass recirculation ball valve 28 and a bypass pipe; the inlet end of the bypass pipe is connected to the third outlet branch of the main circuit outlet pipe, the outlet end of the bypass pipe is connected to the main circuit return pipe, and the bypass recirculation ball valve 28 is installed on the bypass pipe.

[0070] In this embodiment, the flow-accelerated corrosion testing subsystem includes a corrosion tester 34, a first test electrode 36, and a second test electrode 38. The corrosion tester 34 is used to collect the polarization resistance of the test electrodes. The first test electrode 36 is disposed in the 180° electrode flow cell 35, and the second test electrode 38 is disposed in the 90° electrode flow cell 37. The materials of the first test electrode 36 and the second test electrode 38 are the same as the materials of the equipment to be simulated in the air-cooled island, and both the first test electrode 36 and the second test electrode 38 include a working electrode, a reference electrode, and an auxiliary electrode of the same material and model. The working electrode, the reference electrode, and the auxiliary electrode are respectively connected to the corrosion tester 34 through wires. The auxiliary electrode is used to eliminate the influence of pure water resistance. Specifically, in the 180° electrode flow cell 35, the three electrodes of the first test electrode 36 are installed opposite each other along the direction of fluid flow. In the 90° electrode flow cell 37, the three electrodes of the second test electrode 38 are located at their 90° right angles and are installed opposite to the direction of fluid flow.

[0071] As attached Figure 2 As shown, this embodiment also provides a method for simulating accelerated corrosion in an air-cooled island, specifically including the following steps:

[0072] Step 1: Turn on the magnetic pump 14, heater 3, automatic temperature controller 2, fourth flow meter 30, conductivity meter 20, dissolved oxygen meter 24, first temperature sensor 42, and second temperature sensor 43; then, sequentially turn on the gas source 8, pressure reducing valve 44, water tank gas supply shut-off valve 6, chemical dosing tank gas supply shut-off valve 9, and electrode flow cell gas supply shut-off valve 10 to introduce inert gas into the high-purity water tank 1, first chemical dosing tank 11, second chemical dosing tank 12, 180° electrode flow cell 35, and 90° electrode flow cell 37, respectively; preferably, the inert gas... Nitrogen gas is used as the inert gas; and the cooler 15, the first sampling shut-off valve 16, the first flow meter 17, the second sampling shut-off valve 22, the second flow meter 23, the mixed bed sampling shut-off valve 25, the bypass recirculation ball valve 28, the main circuit outlet ball valve 29, the main circuit bypass ball valve 33, and the main circuit return ball valve 39 are turned on to allow the system to continuously circulate for a preset time period, continuously introducing inert gas to keep the dissolved oxygen <5μg / L and the temperature 50~70℃; when the online hydrogen conductivity is <0.10μS / cm, the mixed bed sampling shut-off valve 25 is turned off.

[0073] Step 2: Open the first three-way valve 18 to switch the measurement mode of the conductivity meter 20 from hydrogen conductivity to direct conductivity; open the dosing shut-off valve 13 to add alkalizing agent into the main circuit outlet pipe, and control the opening degree of the dosing shut-off valve 13 so that the direct conductivity reading of the water sample in the system is 2.2 to 5.4 μS / cm; that is, when converting to pH, the pH of the water sample in the system is 8.9 to 9.3.

[0074] Alternatively, open the dosing shut-off valve 13, add oxidant into the main circuit outlet pipe, and control the opening degree of the dosing shut-off valve 13. Take samples at manual sampling points and monitor the concentration of oxidant in the system water sample using instrument testing to keep the concentration of oxidant at 0-2 mg / L. Preferably, the oxidant is hydrogen peroxide.

[0075] Step 3: Close the main circuit bypass ball valve 33, turn on the corrosion tester 34, open the first inlet shut-off valve 31, and record the polarization resistance of the second test electrode 38 in the 90° electrode flow cell 37.

[0076] Step 4: Close the first inlet shut-off valve 31, turn on the corrosion tester 34, and open the second inlet shut-off valve 32. Record the polarization resistance of the first test electrode 36 in the 180° electrode flow cell 35.

[0077] Step 5: Since the corrosion system is controlled by activation polarization, when the natural corrosion potential Ecorr of the corroded metal is far from the equilibrium potential of the two local reactions, the electrode potential E and the corrosion current I conform to the Stern-Geary equation; that is, there is a linear relationship between the change in current and the change in potential near the corrosion potential. Specifically, based on the polarization resistance of the first test electrode 36 and the polarization resistance of the second test electrode 38, the corrosion results of the test electrodes can be obtained using the linear scan (step) method or the AC impedance method, and then the results of the air-cooled island flow accelerated corrosion simulation test can be obtained.

[0078] Step 6: After the experiment is completed, turn off the magnetic pump 14, heater 3, automatic temperature controller 2, fourth flow meter 30, conductivity meter 20, dissolved oxygen meter 24, first temperature sensor 42, and second temperature sensor 43; then, turn off the gas source 8, pressure reducing valve 44, water tank gas supply shut-off valve 6, chemical dosing tank gas supply shut-off valve 9, and electrode flow cell gas supply shut-off valve 10; next, open the drain port 5 of the high-purity water tank 1 to drain the liquid in the high-purity water tank 1; then, open the inlet port 7 of the high-purity water tank 1, inject high-purity water, and turn on the magnetic pump 14 to recirculate the loop and clean the system. Repeat the cleaning 2 to 3 times until the hydrogen conductivity is less than 0.10 μS / cm.

[0079] As attached Figure 3 As shown, Figure 3 The figure shows electrode corrosion polarization curves with different oxidant concentrations at the same pH; from the appendix... Figure 3 The corrosion current density and corrosion rate can be obtained from the data, as shown in Table 1 below; from the attached... Figure 3 As shown in Table 1, with the increase of the oxidant concentration, the corrosion current density gradually decreases, and although the corrosion rate decreases simultaneously, it tends to level off. The corrosion prevention effect is optimal when the concentration of the oxidant added to the test solution is 0.9–1.03 mg / L.

[0080] Table 1. Relationship between oxidant concentration and corrosion current density and corrosion rate

[0081] Theoretical dosage concentration (mg / L) <![CDATA[Corrosion current density (μA / cm 2 )]]> <![CDATA[Corrosion rate (g / m 2. h)]]> 0 2.672 0.045 0.30 1.871 0.037 0.60 1.364 0.028 0.90 1.018 0.019 1.03 1.012 0.019

[0082] It should be noted that the cooler 15 is an air cooler; the first flow meter 17, the second flow meter 23 and the third flow meter 26 are all float flow meters, and the fourth flow meter 30 is a turbine digital display flow meter; the first three-way valve 18 and the second three-way valve 21 are both three-way shut-off valves.

[0083] The simulation test system and method described in this embodiment use a fourth flow meter 30, a main circuit outlet water pressure gauge 41, a first temperature sensor 42, and a second temperature sensor in the main circuit to monitor the flow rate, pressure, and temperature of the water sample in the system, respectively. An oxidant or alkalizing agent is added to the main circuit outlet pipe through a dosing subsystem to adjust the conductivity and oxygen content of the system's operating conditions. A mixed bed 27 is used to purify the pure water in the high-purity water tank 1. A corrosion tester 34 is used to examine the polarization resistance of the carbon steel electrode when it reaches a steady state in solutions of different concentrations of alkalizing agent, oxidant, or a combination of both, to assess its corrosion resistance.

[0084] In this invention, a main loop recirculation and multi-point nitrogen deoxygenation method are used to improve the deoxygenation effect of the system, making the dissolved oxygen in the system less than 5 μg / L; by isolating and protecting the electrodes in the flow cell from the interference and oxidation effects of dissolved oxygen in the water, the original state of the electrodes is truly reflected, reducing experimental errors; a three-electrode system is used to eliminate the influence of pure water resistance on electrochemical corrosion measurement; and the narrow slit design of the flow cell allows the flow velocity to be greater than 20 m / s, maximally simulating the accelerated corrosion of 90° bends and 180° straight pipes under actual working conditions.

[0085] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

Claims

1. A simulated test system for accelerated corrosion in an air-cooled island flow, characterized in that, This includes the main circuit subsystem, the chemical dosing subsystem, and the flow-accelerated corrosion testing subsystem; The main circuit subsystem includes a high-purity water tank (1), a main circuit outlet pipe, an electrode flow cell, and a main circuit return pipe; the high-purity water tank (1) stores high-purity water, the outlet of the high-purity water tank (1) is connected to one end of the main circuit outlet pipe, the other end of the main circuit outlet pipe is connected to the inlet of the electrode flow cell, one end of the main circuit return pipe is connected to the outlet of the electrode flow cell, and the other end of the main circuit return pipe is connected to the return port of the high-purity water tank (1); The dosing subsystem is used to add an alkalizing agent or an oxidizing agent into the main circuit outlet pipe; The flow-accelerated corrosion testing subsystem includes a test electrode and a corrosion tester (34); the test electrode is placed in the electrode flow cell and is connected to the input terminal of the corrosion tester (34) via a wire; wherein the material of the test electrode is the same as the material of the equipment to be simulated in the air-cooled island; the corrosion tester (34) is used to collect the polarization resistance of the test electrode; It also includes an online monitoring subsystem; the online monitoring subsystem includes a cooler (15), a first sampling shut-off valve (16), a first three-way valve (18), a hydrogen exchange column (19), a conductivity meter (20), a second three-way valve (21), a second sampling shut-off valve (22), and a dissolved oxygen meter (24). The inlet end of the cooler (15) is connected to the main circuit water outlet pipe; the outlet end of the cooler (15) is divided into two paths, one of which is connected to one end of the first sampling shut-off valve (16), and the other is connected to one end of the second sampling shut-off valve (22). The other end of the first sampling shut-off valve (16) is connected to the first port of the first three-way valve (18), and the second end of the first three-way valve (18) is connected to the inlet end of the hydrogen exchange column (19); the third port of the first three-way valve (18) and the outlet end of the hydrogen exchange column (19) are both connected to the inlet end of the conductivity meter (20), and the outlet end of the conductivity meter (20) is connected to the first port of the second three-way valve (21); the second port of the second three-way valve (21) is connected to the main circuit return water pipe, and the third port of the second three-way valve (21) serves as a manual sampling port; The other end of the second sampling shut-off valve (22) is connected to the inlet end of the dissolved oxygen meter (24), and the outlet end of the dissolved oxygen meter (24) is connected to the main circuit return water pipe. The dosing subsystem includes a first dosing tank (11), a second dosing tank (12), and a dosing pipeline; the first dosing tank (11) is used to store alkalizing agent, and the second dosing tank (12) is used to store oxidizing agent; the outlet end of the first dosing tank (11) and the outlet end of the second dosing tank (12) are both connected to one end of the dosing pipeline, and the other end of the dosing pipeline is connected to the main circuit outlet pipe.

2. The air-cooled island flow accelerated corrosion simulation test system according to claim 1, characterized in that, It also includes a deoxygenation subsystem; the deoxygenation subsystem includes a gas source (8); the gas source (8) stores inert gas, and the outlet of the gas source (8) is divided into three branches; wherein, the first branch is connected to the high-purity water tank (1), the second branch is connected to the dosing subsystem, and the third branch is connected to the electrode flow cell.

3. The air-cooled island flow accelerated corrosion simulation test system according to claim 1, characterized in that, It also includes a bypass recirculation subsystem; the bypass recirculation subsystem includes a bypass recirculation ball valve (28) and a bypass pipe; one end of the bypass pipe is connected to the main circuit outlet pipe, and the other end of the bypass pipe is connected to the main circuit return pipe; the bypass recirculation ball valve (28) is installed on the bypass pipe.

4. The air-cooled island flow accelerated corrosion simulation test system according to claim 1, characterized in that, It also includes a purification subsystem; the purification subsystem includes a mixed bed sampling shut-off valve (25) and a mixed bed (27); one end of the mixed bed sampling shut-off valve (25) is connected to the main circuit outlet pipe, the other end of the mixed bed sampling shut-off valve (25) is connected to the inlet end of the mixed bed (27), and the outlet end of the mixed bed (27) is connected to the main circuit return pipe.

5. The air-cooled island flow accelerated corrosion simulation test system according to claim 1, characterized in that, The electrode flow cell includes a 180° electrode flow cell (35) and a 90° electrode flow cell (37); the 180° electrode flow cell (35) and the 90° electrode flow cell (37) are connected in parallel between the main circuit outlet pipe and the main circuit return pipe. The 180° electrode flow cell (35) is provided with a first test electrode (36), and the 90° electrode flow cell (37) is provided with a second test electrode (38). The first test electrode (36) and the second test electrode (38) each include a working electrode, a reference electrode and an auxiliary electrode of the same material and model. The working electrode, the reference electrode and the auxiliary electrode are respectively connected to the corrosion tester (34) through wires.

6. The air-cooled island flow accelerated corrosion simulation test system according to claim 1, characterized in that, The main circuit outlet pipe is also equipped with a fourth flow meter (30), a main circuit outlet pressure gauge (41), and a first temperature sensor (42); the fourth flow meter (30) is used to monitor the flow rate of the water sample in the main circuit outlet pipe; the main circuit outlet pressure gauge (41) is used to monitor the pressure of the water sample in the main circuit outlet pipe; the first temperature sensor (42) is located at the inlet of the electrode flow cell and is used to monitor the temperature of the water sample at the inlet of the electrode flow cell. A second temperature sensor (43) is also installed on the main circuit return water pipe. The second temperature sensor (43) is located at the outlet of the electrode flow cell. The second temperature sensor (43) is used to monitor the temperature information of the water sample at the outlet of the electrode flow cell.

7. The air-cooled island flow accelerated corrosion simulation test system according to claim 1, characterized in that, The operating environment characteristics of the air-cooled island flow-accelerated corrosion simulation test system are as follows: temperature 50~70℃, flow rate 15~25m / s, hydrogen conductivity less than 0.15μS / cm, and dissolved oxygen value less than 5μg / L.

8. A method for simulating accelerated corrosion in an air-cooled island, characterized in that, The simulation test system for accelerated corrosion in an air-cooled island, as described in any one of claims 1-7, includes the following steps: Step 1: Using the dosing subsystem, add an alkalizing agent or oxidizing agent to the main loop outlet pipe to bring the hydrogen conductivity or dissolved oxygen value of the water sample in the main loop outlet pipe and the main loop return pipe to the design range. Step 2: Turn on the corrosion tester (34) and record the polarization resistance of the test electrode; Step 3: Determine the corrosion result of the test electrode based on the polarization resistance of the test electrode, and then obtain the results of the air-cooled island flow-accelerated corrosion simulation test.

Images