A system and method for monitoring the corrosion rate during shutdown and nitrogen filling maintenance of a gas-steam combined cycle unit

Abstract

The present invention discloses a system and method for monitoring the corrosion rate and performing nitrogen filling maintenance during the shutdown of a gas-steam combined cycle unit. The system comprises: a metal corrosion coupon, disposed on a metal component of a corrosive-prone device; a corrosion area measurement module, disposed on the corrosive-prone device and used to observe the corrosion condition on the surface of the metal corrosion coupon; a metal corrosion rate monitoring module, disposed near the metal component of the corrosive-prone device and used to continuously measure the corrosion rate of the metal component of the corrosive-prone device; an ambient atmosphere monitoring module, used to continuously measure the ambient atmosphere near the metal component of the corrosive-prone device; a nitrogen filling protection module, used to prepare nitrogen and periodically fill it into the corrosive-prone device requiring maintenance; and an industrial computer, used to receive monitoring signals and send control instructions to the nitrogen filling protection module. The present invention can realize online monitoring of the corrosion rate of metal components of different corrosive-prone devices and nitrogen filling maintenance during the shutdown of a gas-steam combined cycle unit.

Description

Technical Field

[0001] The present invention belongs to the technical field of shutdown maintenance of gas-steam combined cycle units, and in particular relates to a shutdown corrosion rate monitoring and nitrogen filling maintenance system and method for gas-steam combined cycle units. Background Art

[0002] my country's combined-cycle gas-steam units are generally peak-shaving units, characterized by frequent starts and stops and uncertain downtime. Compared to coal-fired power plants, they have fewer annual utilization hours and spend a considerable portion of their time in standby mode. During standby periods, these units experience severe corrosion in certain areas of the unit, including the low-pressure economizer at the tail end of the waste heat boiler (HRSG) flue (flue gas side), the steam drum (steam-water side), the condenser (steam-water side), the deaerator tank (water side), and the TCA (steam side). Corrosion is particularly severe in southern China, where rainfall and humidity are high, leading to significant economic losses and even directly impacting the unit's operational safety and service life. Corrosion on the flue gas side can cause rust or even peeling of the heating surface, reducing its heat transfer performance and increasing flue gas flow resistance. In severe cases, this can affect the unit's normal load-carrying capacity. Corrosion on the steam-water side can also deteriorate the quality of the working fluid during standby periods, significantly increasing water treatment costs.

[0003] At present, technicians in this technical field generally use the following four methods for shutdown maintenance: desiccant method, wet alkali solution method, inert protection method, and hot dry air method.

[0004] The desiccant method is primarily used for maintenance during downtime on the steam / water side of the system. This manual operation follows the following steps: After draining the working fluid from the steam / water side, remove scale and sludge from the system's internal surfaces. An appropriate amount of desiccant is then added to ensure that the metal surfaces on the steam / water side are fully dry (ensuring that no electrolyte solution is present anywhere) to prevent corrosion. This method is only suitable for steam / water system components with large internal spaces and is not suitable for confined spaces. Furthermore, desiccant absorbs moisture over time, becoming thinner and difficult to remove. Therefore, the desiccant should be checked regularly and replaced promptly.

[0005] The wet lye method is a manual process, with the following steps: After removing scale and sludge from the surface of the water vapor system, the boiler is filled with a certain concentration of lye as required, maintaining the pH of the water at 10 or higher. This allows the metal surface to passivate and prevents oxygen corrosion, thereby preventing boiler corrosion. This method is not suitable for use with narrow orifices and can cause alkali corrosion. It is only suitable for boilers that have been out of service for no more than three months. Before starting the boiler, the lye must be drained and all areas exposed to the lye must be cleaned with water. Therefore, boiler maintenance is labor-intensive and cumbersome.

[0006] The inerting method is a manual operation involving the following steps: Gas pipelines are pre-placed in appropriate locations. When the unit is shut down for standby, the inerting equipment is activated, allowing inert gas to be introduced into the maintenance area through these pre-placed pipelines, replacing the existing atmosphere. While this method can mitigate corrosion of metal components during downtime, the inert gas is prone to leakage during extended downtime, rendering it ineffective for long-term protection. Continuous inerting also results in relatively high maintenance costs.

[0007] The hot dry air method follows the same steps as the inerting method, but uses heated and dried air instead of inert gas. This method shares the same issues as the inerting method, but also has the added disadvantages of higher costs and poorer maintenance.

[0008] In addition to their own problems, the above four existing methods also have the problem of being unable to obtain the corrosion rate of metal components of the gas-steam combined cycle unit. Therefore, they can only adopt continuous operation or artificially timed interval operation methods, which greatly increases the cost of shutdown maintenance and may affect the effectiveness of shutdown maintenance. Summary of the Invention

[0009] The present invention provides a system and method for monitoring the corrosion rate of metal parts of different susceptible-to-corrosion equipment during shutdown and nitrogen charging maintenance of a gas-steam combined cycle unit. The system can realize online monitoring of the corrosion rate of metal parts of different susceptible-to-corrosion equipment during shutdown of the gas-steam combined cycle unit and on-demand commissioning of corresponding nitrogen charging modules, thereby achieving shutdown maintenance of metal parts of the gas-steam combined cycle unit.

[0010] A gas-steam combined cycle unit shutdown corrosion rate monitoring and nitrogen filling maintenance system is used to monitor and maintain corrosive equipment in the gas-steam combined cycle unit, including:

[0011] Metal corrosion coupons are placed on metal parts of corrosion-prone equipment to simulate the corrosion conditions of metal parts in corrosion-prone equipment;

[0012] The corrosion area measurement module is installed on the corrosion-prone equipment to observe the corrosion condition of the metal corrosion sample surface and serve as a verification of the resistance value measured by the metal corrosion rate monitoring module;

[0013] The metal corrosion rate monitoring module is installed near the metal parts of the corrosive equipment and is used to continuously measure the corrosion rate of the metal parts of the corrosive equipment during the shutdown and standby period of the gas-steam combined cycle unit;

[0014] The ambient atmosphere monitoring module is installed near the metal corrosion sample and is used to continuously measure the ambient atmosphere near the metal parts of the corrosion-prone equipment during the shutdown and standby period of the gas-steam combined cycle unit;

[0015] A nitrogen filling protection module, comprising a nitrogen generator system, a nitrogen filling valve group, a flow meter, a pressure gauge and a nitrogen filling port connected in sequence by a connecting pipe, is used to prepare nitrogen and regularly fill it into the corrosive equipment that requires maintenance;

[0016] The industrial computer is connected to the metal corrosion rate monitoring module, the environmental atmosphere monitoring module and the nitrogen filling protection module respectively, and is used to receive signals from the metal corrosion rate monitoring module and the environmental atmosphere monitoring module, and send control instructions to the nitrogen filling protection module.

[0017] In the present invention, the easily corrosive equipment includes a low-pressure economizer at the tail end of the flue of a waste heat boiler, a waste heat boiler drum, a condenser and a TCA.

[0018] Furthermore, the metal corrosion sample includes a metal test piece, an insulating protective cover and a fixing bolt; the metal test piece is installed on the inner side of the insulating protective cover, and the front side of the insulating protective cover is exposed, ensuring that the front side of the metal test piece is exposed to the ambient atmosphere; one end of the fixing bolt is connected to the bolt hole on the insulating protective cover, and the other end is fixed to the metal part of the corrosion-prone equipment by welding.

[0019] In order to ensure that the corrosion rate of the metal test piece is consistent with the corrosion rate of the metal parts of the corrosion-prone equipment, preferably, the metal test piece is made of the same metal material as the corresponding corrosion-prone equipment, and the front side of the metal test piece is polished, cleaned and low-temperature dried.

[0020] The front side of the insulating protective cover is exposed, ensuring that the front side of the metal test piece is exposed to the ambient atmosphere. A bolt hole is provided on one side of the insulating protective cover. During installation, the metal test piece is first installed on the insulating protective cover exposed on both sides. The insulating protective cover is connected to the external thread of the fixing bolt through threaded cooperation. The insulating protective cover and the metal test piece are installed on the corrosion-prone equipment through the fixing bolt.

[0021] Furthermore, the corrosion area measurement module includes an industrial CCD and a data transmission line; the industrial CCD has a fill light function, is fixedly installed and facing the exposed surface of the metal test piece, and continuously captures corrosion images of the metal test piece surface.

[0022] In order to obtain the corrosion rate of metal parts of corrosion-prone equipment in the shutdown and standby state of a gas-steam combined cycle unit, a metal corrosion specimen was installed near the metal parts of the corrosion-prone equipment when the unit was shut down for the first time. The corrosion area measurement module was installed facing the exposed surface of the metal specimen of the metal corrosion specimen, and an industrial CCD continuously captured images of the corrosion condition of the exposed surface of the metal specimen.

[0023] In order to quantify the corrosion condition image of the metal test piece surface, the captured image is processed, each pixel in the image is identified, the R, G, and B values of all pixels are read, and the R, G, and B values are converted into grayscale values. The difference between the surface color of the polished metal test piece and the surface color after corrosion is used to calculate the relative area of the shadow part according to the grayscale values of all pixels, and quantitative data on the proportional change value of the corrosion area on the metal test piece surface is obtained.

[0024] Furthermore, the metal corrosion rate monitoring module includes a stabilized power supply, a wire, a fixed resistor and a data acquisition instrument; the stabilized power supply is connected to the two ends of the front side of the metal test piece through the wire, and the fixed resistor is connected in series and connected to the data acquisition instrument for continuously measuring the resistance value of the metal test piece.

[0025] When corrosion occurs on the surface of the metal test piece, the metal material oxidizes and becomes insulated, and the conductive cross-sectional area of the metal test piece decreases. The data acquisition instrument is connected in series with the voltage-stabilized power supply and the metal test piece to collect real-time data on the current changes in the loop and calculate the metal test piece resistance value used to reflect the corrosion rate of the metal test piece.

[0026] The corrosion area ratio on the metal test piece surface has a certain correlation with the resistance of the metal test piece. The quantitative data of the corrosion area on the metal test piece surface obtained by measuring and image processing using the corrosion area measurement module can be used to verify the metal test piece resistance value measured by the metal corrosion rate monitoring module.

[0027] In order to avoid the impact of the metal corrosion rate monitoring module on the normal operation of the flue gas side and the steam-water side during normal operation of the unit, the metal corrosion sample, corrosion area measurement module and metal corrosion rate monitoring module are removed from the corrosion-prone equipment when the unit ends its shutdown and standby state.

[0028] In order to avoid the need to install metal corrosion samples, corrosion area measurement modules and metal corrosion rate monitoring modules every time the unit is shut down for standby, preferably, the environmental atmosphere monitoring module is set at the same position as the corrosive equipment, and the environmental atmosphere of the metal parts, including O2, SO2, NO x , H2S, HCl, temperature, humidity, etc., for continuous measurement.

[0029] The corrosion rate of metal materials is affected by the ambient atmosphere in which they are located. Different ambient atmospheres exhibit different corrosion rates, and there is a certain correspondence between the ambient atmosphere and the corrosion rate. Therefore, based on the metal test strip resistance value collected and calculated by the metal corrosion rate monitoring module and the ambient atmosphere quantitative data measured by the ambient atmosphere monitoring module, the present invention constructs a mathematical model based on the ambient atmosphere quantitative data and the metal test strip corrosion rate (resistance value) using a random forest regression algorithm. This model serves as the basis for subsequent corrosion rate evaluation of the metal component based on the ambient atmosphere in which it is located.

[0030] Furthermore, the industrial computer continuously collects digital signals of the ambient atmosphere in which the metal parts of the easily corroded equipment are located, and calculates the corrosion rate of the metal parts in real time based on the constructed quantitative data of the ambient atmosphere and the mathematical model of the corrosion rate of the metal test piece. According to the corrosion rate of the metal parts of different easily corroded equipment, the nitrogen generator system and the nitrogen filling valve group in the nitrogen filling module are controlled. When the corrosion rate of the metal parts exceeds the set threshold, the nitrogen generator system and the corresponding valve group are automatically turned on.

[0031] In order to avoid the nitrogen generator system from increasing its power consumption due to continuous long-term operation, preferably, the industrial control computer continuously monitors the nitrogen filling pressure of each corrosive equipment at the same time, and controls the start and stop of the nitrogen generator system and the nitrogen filling valve group according to the nitrogen filling pressure of the corrosive equipment and the corrosion rate of the metal parts. When the nitrogen filling pressure of the corrosive equipment is higher than the set threshold and the corrosion rate of the metal parts is lower than the set threshold, the nitrogen generator system and the corresponding valve group are automatically shut down; when the nitrogen filling pressure of the corrosive equipment is lower than the set threshold and the corrosion rate of the metal parts is higher than the set threshold again, the nitrogen generator system and the corresponding valve group are automatically opened again.

[0032] The present invention also provides a method for monitoring the corrosion rate during shutdown and nitrogen filling maintenance of a gas-steam combined cycle unit. The method uses the above-mentioned system for monitoring the corrosion rate during shutdown and nitrogen filling maintenance of a gas-steam combined cycle unit. The specific process is as follows:

[0033] (1) When the gas-steam combined cycle unit enters the shutdown standby state, metal corrosion samples are fixed on the metal parts of the unit's easily corroded equipment, and a corrosion area measurement module and a metal corrosion rate monitoring module are set;

[0034] The ambient atmosphere monitoring module is placed near the metal corrosion sample to obtain continuous quantitative data of the ambient atmosphere near the metal parts of the corrosion-prone equipment;

[0035] (2) Use the industrial CCD of the corrosion area measurement module to take interval pictures of the corrosion of the metal specimen surface in the metal corrosion sample, and obtain quantitative data of the change value of the corrosion area ratio on the metal specimen surface through image processing;

[0036] (3) Based on the voltage value provided by the regulated power supply of the metal corrosion rate monitoring module and the current value collected in real time by the data acquisition instrument, the resistance value and resistance change rate of the metal test piece are calculated in real time to characterize the corrosion rate of the metal component;

[0037] (4) Using the corrosion area measurement module to obtain the percentage change value of the metal specimen surface corrosion area, verify the resistance value and resistance value change rate data measured by the metal corrosion rate monitoring module;

[0038] (5) When the gas-steam combined cycle unit ends its standby state, take out the metal corrosion sample, corrosion area measurement module and metal corrosion rate monitoring module;

[0039] (6) Ambient atmosphere O2, SO2, NO measured by the ambient atmosphere monitoring module x , H2S, HCl and temperature, humidity continuous quantitative data, based on the random forest regression algorithm, to establish the relationship model between the quantitative data of the ambient atmosphere and the corrosion rate of the metal specimen, that is, the mathematical model of the resistance value change rate;

[0040] (7) When the gas-steam combined cycle unit is shut down for standby again, continuously monitor the changes in the ambient atmosphere near the metal parts of the corrosive equipment;

[0041] (8) Based on the relationship model between the quantitative data of the ambient atmosphere and the corrosion rate of the metal specimen, the resistance value and the resistance value change rate of the metal parts of the corrosive equipment are calculated according to the changes in the ambient atmosphere near the metal parts of the corrosive equipment;

[0042] (9) According to the corrosion rate of metal parts, that is, the resistance value change rate, the corrosion rate threshold for the nitrogen filling protection module is set. The industrial computer controls the operation of the nitrogen generator system and the nitrogen filling valve group in the nitrogen filling protection module based on the calculated resistance value change rate of the metal parts of the corrosive equipment;

[0043] (10) Continuously monitor the ambient atmosphere and nitrogen filling pressure near the metal parts of the corrosive equipment, and automatically control the start and stop of the nitrogen filling protection module on demand;

[0044] (11) By monitoring the environmental atmosphere of different corrosive equipment and calculating the metal corrosion rate index, a mathematical model of the quantitative data of the environmental atmosphere of each corrosive equipment and the metal corrosion rate index is established, and nitrogen filling maintenance is carried out on demand for each corrosive equipment.

[0045] Furthermore, in step (3), when corrosion occurs on the surface of the metal test piece, the metal material is oxidized and insulated, the conductive cross-sectional area of the metal test piece decreases, and the resistance increases.

[0046] Furthermore, in step (6), the metal test piece has different corrosion rates under different environmental atmospheres, showing different surface corrosion area ratio change values and resistance values.

[0047] Furthermore, in step (11), when it is monitored that the metal parts of the corrosive equipment are in an environment with a high corrosion rate, that is, the environment atmosphere is higher than the set threshold, the nitrogen generator system and the nitrogen charging valve group at the corresponding position are automatically put into operation; when it is monitored that the nitrogen charging pressure and the environment atmosphere reach a certain threshold, the operation of the nitrogen generator system and the nitrogen charging valve group at the corresponding position is automatically suspended; when it is monitored that the environment atmosphere is higher than the set threshold again, the nitrogen generator system and the nitrogen charging valve group at the corresponding position are automatically put into operation again.

[0048] Compared with the prior art, the present invention has the following beneficial effects: the system and method provided by the present invention, by constructing a relationship model between metal corrosion area, corrosion rate and ambient atmosphere, can dynamically invert the corrosion condition of corrosive equipment during the shutdown and maintenance of a gas-steam combined cycle unit, thereby achieving shutdown and maintenance of corrosive equipment in the gas-steam combined cycle unit by controlling the on-demand startup and shutdown of nitrogen filling protection modules at corresponding locations. The system and method have good application prospects, specifically:

[0049] 1. The corrosion area measurement module and metal corrosion rate measurement module can observe and quantitatively monitor the corrosion status of corrosive components during downtime maintenance. Combined with continuous monitoring of the surrounding ambient atmosphere and the application of the random forest regression algorithm, they can effectively link the ambient atmosphere with the corrosion status of corrosive equipment, providing a theoretical basis for evaluating the corrosion status of corrosive equipment. Compared with the corrosion area measurement module and metal corrosion rate measurement module, the ambient atmosphere monitoring module has a simpler structure and is easier to set up, reducing the system setup workload for each downtime maintenance.

[0050] 2. The nitrogen filling protection module and the nitrogen generator system automatically start and stop according to the corrosion status of the easily corrosive equipment monitored by the ambient atmosphere monitoring module and the set corrosion rate threshold. On the one hand, this avoids the increase in energy consumption caused by the continuous operation of the nitrogen generator system. On the other hand, it ensures the effective shutdown maintenance of the easily corrosive equipment and improves the metal corrosion problem during the shutdown maintenance of the gas-steam combined cycle unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a layout diagram of a shutdown corrosion rate monitoring and nitrogen filling maintenance system for a gas-steam combined cycle unit according to an embodiment of the present invention.

[0052] Figure 2 This is a layout diagram of a metal corrosion sample, a corrosion area measurement module, a metal corrosion rate monitoring module, and an environmental atmosphere monitoring module installed on corrosion-prone equipment in an embodiment of the present invention.

[0053] Figure 3 The corrosion image of the exposed surface of the metal specimen observed by the corrosion area measurement module in the embodiment of the present invention and the image processing result.

[0054] Figure 4 The figures show the resistance value and resistance change rate of the metal test piece continuously measured in the embodiment of the present invention, and the quantitative data results of the corrosion area ratio of the exposed surface of the metal test piece taken at intervals.

[0055] Figure 5 The relationship between the resistance value of the metal test piece and the quantitative data of the ratio of the corrosion area of the exposed surface of the metal test piece established in the embodiment of the present invention is shown in FIG. DETAILED DESCRIPTION

[0056] The present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be noted that the following examples are intended to facilitate understanding of the present invention and do not have any limiting effect on the present invention.

[0057] A gas-steam combined cycle unit shutdown corrosion rate monitoring and nitrogen filling maintenance system is used to monitor and maintain the easily corrosive equipment in the gas-steam combined cycle unit. Figure 1 As shown, the easily corrosive equipment includes the low-pressure economizer 101 at the tail end of the waste heat boiler flue, the waste heat boiler drum 102, the condenser 103 and the TCA 104.

[0058] like Figure 1 and Figure 2 As shown, the entire system specifically includes a monitoring module 1, a nitrogen filling protection module 6 and an industrial control computer 7, wherein the monitoring module 1 includes a metal corrosion sample 2, a corrosion area measurement module 3, a metal corrosion rate monitoring module 4, and an environmental atmosphere monitoring module 5.

[0059] The metal parts of the corrosion-prone equipment in the long-term standby state (the flue gas side finned tubes of the low-pressure economizer 101 at the tail end of the waste heat boiler flue, the steam-water side inner wall and internal steel frame of the waste heat boiler drum 102, the steam-water side inner wall and internal steel frame of the condenser 103, and the steam side of TCA104) are affected by the surrounding atmosphere (including O2, SO2, NO x , H2S, HCl, temperature, humidity, etc.), the metal surface will corrode, causing the surface to rust and the conductive performance to deteriorate.

[0060] The metal corrosion sample 2 is used to simulate the corrosion condition of the metal parts of the unit's easily corroded equipment; the corrosion area measurement module 3 is used to observe the corrosion condition of the metal corrosion sample surface; the metal corrosion rate monitoring module 4 is used to monitor the corrosion rate of the metal parts of the unit's easily corroded equipment; the environmental atmosphere monitoring module 5 is used to continuously monitor the environmental atmosphere near the metal parts of the unit's easily corroded equipment for a long time; the nitrogen filling protection module 6 operates intermittently and is used to perform nitrogen filling maintenance on the unit's easily corroded equipment; the industrial control computer 7 judges the corrosion rate condition of the metal parts of the easily corroded equipment according to changes in the environmental atmosphere and remotely controls the intermittent use of the nitrogen filling protection module 6.

[0061] like Figure 2 As shown, the metal corrosion sample 2 includes a metal test piece 201, an insulating protective sleeve 202, and a fixing screw 203. The metal test piece 201 is fixed in the insulating protective sleeve 202; one end of the fixing screw 203 is threadedly connected to the insulating protective sleeve 202, and the other end is fixed to the metal component of the unit's corrosion-prone equipment by welding or other methods.

[0062] The metal test piece 201 is made of the same metal material as the metal components of the unit's easily corroded equipment (the flue gas side finned tubes of the low-pressure economizer 101 at the tail end of the waste heat boiler flue, the steam-water side inner wall and internal steel frame of the waste heat boiler drum 102, the steam-water side inner wall and internal steel frame of the condenser 103, and the steam side of the TCA 104). The front side of the metal test piece 201 is polished, cleaned, and low-temperature dried.

[0063] In order to prevent the resistance value measurement result of the metal test piece from being affected by the metal parts in the corrosion-prone area of the unit, the insulating protective cover 202 wraps the metal test piece 201 inside, and the front side of the insulating protective cover 202 is exposed, ensuring that the front side of the metal test piece 201 is exposed to the ambient atmosphere. A bolt hole is also provided on one side of the insulating protective cover 202, which is connected to the external thread of the fixing bolt 203 through threaded cooperation. The insulating protective cover and the metal test piece are installed on the metal parts of the corrosion-prone equipment through the fixing bolt 203.

[0064] The corrosion area measurement module 3 includes an industrial CCD 301 and a data line 302 . The industrial CCD 301 faces the exposed side of the metal test piece 201 and transmits the captured image to the industrial computer 7 via the data line 302 .

[0065] In order to obtain quantitative data on the surface corrosion condition of the metal test piece 201 in the metal corrosion sample 2, the corrosion area measurement module 3 is installed opposite to the exposed surface of the metal test piece 201, monitors the corrosion condition of the exposed surface of the metal test piece 201, captures an image of the surface corrosion, and through image processing, utilizes the difference between the metal color after the surface of the metal test piece 201 is polished and cleaned and the metal color after the surface corrosion, identifies the color value of each pixel in the image, and obtains quantitative data on the change value of the proportional corrosion area of the surface of the metal test piece 201.

[0066] To obtain more precise quantitative corrosion rate data for the metal test piece, a metal corrosion rate monitoring module 4 is installed and connected to the metal test piece 201 via a wire 402. This module continuously measures quantitative resistance data for the metal test piece 201. The module includes a stabilized power supply 401, a wire 402, a constant-value resistor 403, and a data acquisition device 404. The stabilized power supply 401 is connected to the two exposed surfaces of the metal test piece 201, the constant-value resistor 403, and the data acquisition device 404 via wires 402. The module transmits the measured voltage and current values to the industrial computer 7.

[0067] To avoid the need to install metal corrosion coupon 2, corrosion area measurement module 3, and metal corrosion rate monitoring module 4 during each standby shutdown, an ambient atmosphere monitoring module 5 is positioned near metal corrosion coupon 2 to continuously monitor the ambient atmosphere near the metal components of the unit's corrosion-prone equipment. Changes in the ambient atmosphere will also affect the corrosion rate of metal coupon 201. Based on the metal coupon resistance value obtained by the metal corrosion rate monitoring module 4 and the ambient atmosphere continuously monitored by the ambient atmosphere monitoring module 5, a mathematical model is constructed using a random forest regression algorithm to link the quantitative ambient atmosphere data with the metal coupon corrosion rate (resistance value). This model serves as the basis for subsequent corrosion rate evaluation of the metal components based on the ambient atmosphere they are exposed to.

[0068] like Figure 1 and Figure 2 As shown, the nitrogen filling protection module 6 shares a nitrogen generator system 601 (including an air compressor, a cold dryer, a nitrogen-oxygen separation device, a gas storage tank, and a dust filter); the prepared nitrogen is delivered to each easily corrosive component through a nitrogen filling port 603 via a connecting pipe 602; the flow rate of the charged nitrogen is measured by a flow meter 604; the nitrogen filling pressure of each easily corrosive component is measured using a pressure gauge 605; and nitrogen filling is performed on demand to different easily corrosive components according to the corrosion rate of their metal parts by switching a nitrogen filling valve group 606.

[0069] The industrial computer 7 simultaneously records the quantitative data of the surface corrosion area ratio of the metal test piece 201 measured by the metal corrosion rate monitoring module 4, the resistance value and the quantitative data of the ambient atmosphere near the metal test piece 201 measured by the ambient atmosphere monitoring module 5, establishes a mathematical relationship model, judges the corrosion rate status of the metal parts of the corrosive equipment by monitoring the changes in the ambient atmosphere, and remotely controls the intermittent use of the nitrogen preparation and nitrogen filling protection modules.

[0070] A method for monitoring the corrosion rate of a gas-steam combined cycle unit during shutdown and nitrogen filling maintenance includes the following steps:

[0071] (1) When the gas-steam combined cycle unit enters the shutdown standby state, a metal corrosion sample 2 is fixed on the metal parts of the unit's easily corroded equipment, and a corrosion area measurement module 3 and a metal corrosion rate monitoring module 4 are set.

[0072] (2) The exposed surface of the metal test piece 201 is photographed at intervals using the industrial CCD 301 of the corrosion area measurement module 3 to obtain a corrosion image of the exposed surface of the metal test piece 201. Quantitative data of the change value of the corrosion area ratio on the metal test piece surface is obtained through image processing.

[0073] like Figure 3 As shown, the corrosion area measurement module 3 obtains quantitative data of the corrosion area ratio after imaging the surface image of the metal test piece 201. As the downtime and standby time increase, the corrosion area ratio of the metal test piece 201 obtained by image processing gradually increases, and the increase is most obvious from the 15th day to the 30th day.

[0074] (3) Based on the voltage provided by the voltage-stabilized power supply 401 of the metal corrosion rate monitoring module 4, the data acquisition device 404 collects the current data in the loop in real time, and calculates the resistance value and resistance value change rate of the metal test piece 201 in real time to characterize the corrosion rate of the metal component.

[0075] like Figure 4 As shown, the metal corrosion rate monitoring module 4 continuously measures and calculates the continuous data of the resistance value of the metal test piece 201 and obtains quantitative data of the ratio of the corrosion area of the exposed surface of the metal test piece by interval shooting. As the shutdown standby time increases, the resistance value of the metal test piece 201 measured by the metal corrosion rate monitoring module 4 gradually increases, and the increase is most obvious from the 23rd day to the 25th day. The calculated resistance value increases most significantly, and the resistance value change rate is the highest.

[0076] (4) The resistance value and resistance value change rate data measured by the metal corrosion rate monitoring module 4 are verified by using the corrosion area measurement module 3 to obtain the proportional change value of the corrosion area of the metal test piece 201.

[0077] like Figure 5 As shown, the metal corrosion rate monitoring module 4 continuously measures and calculates the relationship between the continuous data of the resistance value of the metal test piece 201 and the quantitative data of the ratio of the corrosion area of the exposed surface of the metal test piece obtained by interval shooting, and the fitting relationship between the ratio of the corrosion area of the metal test piece surface Y and the resistance value X of the metal test piece is obtained as follows:

[0078]

[0079] (5) At the same time as steps (2) and (3), place the ambient atmosphere monitoring module at the same location as the metal corrosion sample to obtain the ambient atmosphere near the metal parts of the corroded equipment, including O2, SO2, NO x , H2S, HCl, temperature, humidity and other continuous quantitative data are recorded in the industrial computer 7.

[0080] (6) When the gas-steam combined cycle unit ends its standby state, the metal corrosion sample 2, the corrosion area measurement module 3, and the metal corrosion rate monitoring module 4 are taken out.

[0081] (7) Ambient atmosphere O2, SO2, NO measured by ambient atmosphere monitoring module 5 x , H2S, HCl, temperature, humidity and other continuous quantitative data, and based on the random forest regression algorithm, a mathematical model of the environmental atmosphere quantitative data and the metal corrosion rate, that is, the resistance value change rate, is established.

[0082] (8) When the gas-steam combined cycle unit is shut down for standby again, the ambient atmosphere monitoring module 5 is used to continuously monitor the changes in the ambient atmosphere near the metal parts of the corrosion-prone equipment.

[0083] (9) Based on the mathematical model of the quantitative data of the ambient atmosphere and the corrosion rate of the metal specimen, i.e., the rate of change of the resistance value, the resistance value and the rate of change of the resistance value of the metal parts of the corrosion-prone equipment are calculated according to the changes in the ambient atmosphere near the metal parts of the corrosion-prone equipment.

[0084] (10) According to the calculated resistance value change rate of the metal parts, the corrosion rate threshold of the nitrogen filling protection module 6 is set, for example, when the resistance value change rate of the metal parts reaches 0.05×10 -6 Ω / min is used as the judgment condition for nitrogen filling maintenance. Based on the established mathematical model, the industrial computer 7 calculates the resistance value change rate of each corrosion-prone component according to the monitored ambient atmosphere of each corrosion-prone component. When the resistance value change rate of a corrosion-prone component reaches the threshold value of 0.05×10 -6 Ω / min, the nitrogen generator system 601 and the corresponding nitrogen filling valve group 606 are controlled to be put into operation.

[0085] (11) The ambient atmosphere monitoring module 5 continuously monitors the ambient atmosphere and nitrogen filling pressure near the metal parts of the corrosive equipment. The industrial computer 7 automatically controls the nitrogen filling protection module on demand. When the resistance value change rate of a corrosive part is lower than the threshold value of 0.05×10 -6 Ω / min, the nitrogen generator system 601 and the corresponding nitrogen filling valve group 606 are shut down to reduce the power consumption of the nitrogen generator system 601 during long-term continuous operation.

[0086] (12) The environmental atmosphere monitoring module 5 monitors the environmental atmosphere of different corrosive equipment and calculates the metal corrosion rate index, and establishes a mathematical model of the quantitative data of the environmental atmosphere of each corrosive equipment and the metal corrosion rate index, and performs nitrogen filling maintenance on demand for each corrosive equipment.

[0087] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for monitoring the corrosion rate during shutdown and nitrogen filling maintenance of a gas-steam combined cycle unit, which is used to monitor and maintain corrosive equipment in a gas-steam combined cycle unit, and is characterized in that: The gas-steam combined cycle unit shutdown corrosion rate monitoring and nitrogen filling maintenance system used includes: A metal corrosion coupon is placed on a metal component of a corrosion-prone device to simulate the corrosion conditions of the metal component in the corrosion-prone device. The metal corrosion coupon comprises a metal test piece, an insulating protective cover, and a fixing bolt. The metal test piece is installed inside the insulating protective cover, with the front side of the insulating protective cover exposed, ensuring that the front side of the metal test piece is exposed to the ambient atmosphere. One end of the fixing bolt is connected to the bolt hole in the insulating protective cover, and the other end is fixed to the metal component of the corrosion-prone device by welding. The metal test piece is made of the same metal material as the corresponding corrosion-prone device, and the front side of the metal test piece is polished, cleaned, and low-temperature dried. The corrosion area measurement module is installed on the corrosion-prone equipment to observe the corrosion condition of the metal corrosion sample surface and serve as a verification of the resistance value measured by the metal corrosion rate monitoring module; A metal corrosion rate monitoring module is installed near metal parts of corrosive equipment and is used to continuously measure the corrosion rate of metal parts of corrosive equipment during the shutdown and standby period of the gas-steam combined cycle unit. The metal corrosion rate monitoring module includes a regulated power supply, a wire, a fixed resistor, and a data acquisition instrument. The regulated power supply is connected to the two ends of the front surface of the metal test piece via a wire, is connected in series with a fixed resistor, and is connected to the data acquisition instrument for continuously measuring the resistance value of the metal test piece. The ambient atmosphere monitoring module is installed near the metal corrosion sample and is used to continuously measure the ambient atmosphere near the metal parts of the corrosion-prone equipment during the shutdown and standby period of the gas-steam combined cycle unit; A nitrogen filling protection module, comprising a nitrogen generator system, a nitrogen filling valve group, a flow meter, a pressure gauge and a nitrogen filling port connected in sequence by a connecting pipe, is used to prepare nitrogen and regularly fill it into the corrosive equipment that requires maintenance; The industrial computer is connected to the metal corrosion rate monitoring module, the environmental atmosphere monitoring module, and the nitrogen filling protection module respectively, and is used to receive signals from the metal corrosion rate monitoring module and the environmental atmosphere monitoring module, and send control instructions to the nitrogen filling protection module; The specific process is as follows: (1) When the gas-steam combined cycle unit enters the shutdown standby state, metal corrosion samples are fixed on the metal parts of the unit's easily corroded equipment, and a corrosion area measurement module and a metal corrosion rate monitoring module are set; The ambient atmosphere monitoring module is placed near the metal corrosion sample to obtain continuous quantitative data of the ambient atmosphere near the metal parts of the corrosion-prone equipment; (2) Using the industrial CCD of the corrosion area measurement module to take interval pictures of the corrosion surface of the metal specimen in the metal corrosion sample, quantitative data of the change value of the corrosion area ratio of the metal specimen surface is obtained through image processing; (3) Calculate the resistance value and resistance change rate of the metal test piece in real time based on the voltage value provided by the regulated power supply of the metal corrosion rate monitoring module and the current value collected in real time by the data acquisition instrument to characterize the corrosion rate of the metal component; (4) Using the corrosion area measurement module to obtain the percentage change value of the metal specimen surface corrosion area, verify the resistance value and resistance value change rate data measured by the metal corrosion rate monitoring module; (5) When the gas-steam combined cycle unit ends its standby state, remove the metal corrosion sample, the corrosion area measurement module, and the metal corrosion rate monitoring module; (6) Ambient atmosphere O2, SO2, NO measured by the ambient atmosphere monitoring module x , H2S, HCl, temperature, and humidity continuous quantitative data, and based on the random forest regression algorithm, a relationship model between the quantitative data of the ambient atmosphere and the corrosion rate of the metal specimen, that is, a mathematical model of the resistance value change rate, is established; (7) When the gas-steam combined cycle unit is shut down for standby again, continuously monitor the changes in the ambient atmosphere near the metal parts of the corrosive equipment; (8) Based on the relationship model between the quantitative data of the ambient atmosphere and the corrosion rate of the metal specimen, the resistance value and the resistance value change rate of the metal parts of the corrosive equipment are calculated according to the changes in the ambient atmosphere near the metal parts of the corrosive equipment; (9) According to the corrosion rate of the metal parts, that is, the resistance value change rate, the corrosion rate threshold for the nitrogen filling protection module is set. The industrial computer controls the operation of the nitrogen generator system and the nitrogen filling valve group in the nitrogen filling protection module according to the calculated resistance value change rate of the metal parts of the corrosive equipment; (10) Continuously monitor the ambient atmosphere and nitrogen filling pressure near the metal parts of the corrosive equipment, and automatically control the start and stop of the nitrogen filling protection module as needed; (11) By monitoring the environmental atmosphere of different susceptible equipment and calculating the metal corrosion rate index, a mathematical model of the quantitative data of the environmental atmosphere of each susceptible equipment and the metal corrosion rate index is established, and nitrogen filling maintenance is carried out on demand for each susceptible equipment.

2. The method for monitoring the shutdown corrosion rate and nitrogen filling maintenance of a gas-steam combined cycle unit according to claim 1, characterized in that: The corrosive equipment includes the low-pressure economizer at the tail end of the waste heat boiler flue, the waste heat boiler steam drum, the condenser and the TCA.

3. The method for monitoring the shutdown corrosion rate and nitrogen filling maintenance of a gas-steam combined cycle unit according to claim 1, characterized in that: The ambient atmosphere monitored by the ambient atmosphere monitoring module includes O2, SO2, NO x , H2S, HCl and temperature and humidity.

4. The method for monitoring the shutdown corrosion rate and nitrogen filling maintenance of a gas-steam combined cycle unit according to claim 1, characterized in that: In step (3), when corrosion occurs on the surface of the metal test piece, the metal material is oxidized and insulated, the conductive cross-sectional area of the metal test piece decreases, and the resistance increases.

5. The method for monitoring the shutdown corrosion rate and nitrogen filling maintenance of a gas-steam combined cycle unit according to claim 1, characterized in that: In step (6), the metal test piece has different corrosion rates under different environmental atmospheres, showing different surface corrosion area ratio change values and resistance values.

6. The method for monitoring the shutdown corrosion rate and nitrogen filling maintenance of a gas-steam combined cycle unit according to claim 1, characterized in that: In step (11), when it is monitored that the metal parts of the corrosive equipment are in an environment with a high corrosion rate, that is, the environment atmosphere is higher than the set threshold, the nitrogen generator system and the nitrogen charging valve group at the corresponding position are automatically put into operation; when it is monitored that the nitrogen charging pressure and the environment atmosphere reach a certain threshold, the operation of the nitrogen generator system and the nitrogen charging valve group at the corresponding position is automatically suspended; when it is monitored that the environment atmosphere is higher than the set threshold again, the nitrogen generator system and the nitrogen charging valve group at the corresponding position are automatically put into operation again.

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