Method for evaluating service life of metal heating surface of boiler

Abstract

The invention relates to the technical field of boiler metal tubes, in particular to a boiler metal heating surface service life evaluation method which comprises an online boiler data system, an online monitoring device server and a client. A plurality of medium pressure sensors, a plurality of temperature sensors, a plurality of element wall temperature sensors, a plurality of time timers and a plurality of load sensors are distributed and arranged at corresponding measuring point positions of a boiler superheat pipe, and the creep fracture time of a metal material under specific temperature and stress is obtained through calculation; according to the boiler metal heating surface service life evaluation method, reasonable medium pressure, temperature, element wall temperature, time and load value range are set, and through the setting, the boiler metal heating surface service life evaluation method is used for evaluating the service life of a boiler superheat pipe only by adopting calculation modes of high-temperature creep and high-temperature corrosion damage; and meanwhile, reasonable data real-time monitoring of medium pressure, temperature, element wall temperature, time and load is provided, and real-time monitoring and early warning processing can be conveniently carried out on the boiler overheating pipe.

Description

Technical Field

[0001] The invention relates to the technical field of boiler metal tubes, in particular to a method for evaluating the life of a boiler metal heating surface. Background Art

[0002] The life assessment of the boiler heating surface should be based on its damage pattern over time. The main causes of damage to the superheater metal tubes include creep, fatigue damage, etc. Take the metal tube damage pattern mainly caused by long-term high-temperature creep, stress fatigue damage on the working fluid side, and high-temperature corrosion thinning on the fire side as an example.

[0003] Some boiler metal heating surface life assessment methods only use the calculation method of high-temperature creep and high-temperature corrosion damage to assess the life of boiler superheater tubes. There is a lack of reasonable real-time monitoring of medium pressure, temperature, component wall temperature, time and load data, which makes it inconvenient to perform real-time monitoring and early warning of boiler superheater tubes. Therefore, a boiler metal heating surface life assessment method is proposed to address the above problems. Summary of the invention

[0004] The purpose of the present invention is to provide a method for evaluating the life of a boiler metal heating surface, which is used to solve the problem that some methods for evaluating the life of a boiler metal heating surface only use the calculation method of high-temperature creep and high-temperature corrosion damage to evaluate the life of a boiler superheater tube, and lack reasonable real-time monitoring of medium pressure, temperature, component wall temperature, time and load data, making it inconvenient to perform real-time monitoring and early warning processing of the boiler superheater tube.

[0005] To achieve the above object, the present invention provides the following technical solutions: A boiler metal heating surface life assessment method includes an online boiler data system, an online monitoring device server and a client, wherein the online boiler data system includes a DCS configuration system IT communication module and a measuring point monitoring data module; The online monitoring device server provides data processing services for data screening module, preprocessing module, over-limit alarm module, component monitoring database module, creep fatigue damage calculation module and life damage result database module. The component monitoring database module includes data collection and storage of medium pressure, temperature, component wall temperature, time and load. The life damage result database module includes statistics on creep and fatigue damage conditions. The client includes a client terminal module, which is used for monitoring and life damage data query, printing and backup processing.

[0006] Boiler metal heating surface life assessment method: S1. Install several medium pressure sensors, temperature sensors, component wall temperature sensors, time counters and load sensors at the corresponding measuring points of the boiler superheater tubes, and establish a DCS configuration system IT communication within the factory to collect the sensor data in real time and upload it to the subsequent server.

[0007] S2. Select several critical temperature values ​​of the boiler superheater tube when it is heated, and simulate and calculate the stress creep rupture time of the tube wall material at the above temperature values. The Larson-Miller formula is the most widely used in the time-temperature parameter method.

[0008] The creep rate can be described by the following formula: (1) Where: A——empirical constant; R——gas constant; T——absolute temperature of metal; Q – Creep activation energy; The creep rupture time τ is inversely proportional to the creep velocity v, so: (2) Taking the logarithm of both sides of the equation gives: (3) Assuming A is a material constant and Q is a function of stress, let , then the above formula can be rewritten as: (4) P(σ) in the above formula is called the thermal intensity parameter, also known as the Larson-Miller parameter; The functional relationship between thermal parameters and stress and the constant C related to metal materials are generally obtained through creep rupture tests. In the test, a higher temperature is selected to shorten the test time. When the stress magnitude remains constant: (5) Under the condition of equal stress, choose two different temperatures By conducting separate tests, two different break times can be obtained. , and substitute it into formula (5) and calculate to get the C value; (6) (7) By selecting n different stresses σ for creep rupture tests, n different C values ​​C (=1, 2, 3..n) can be obtained according to formula (6). The C value of the metal material can also be obtained by averaging these n values. According to the test data, a functional relationship of P(σ) is fitted. Under normal conditions, the empirical function form of P(σ) is considered to be a high-order polynomial with lgσ as the independent variable: (8) Combining equation (8) with equation (4): (9) Then it is organized into the form of f(τ,σ,T), then: (10) Substitute the stress values ​​under different test conditions into equation (8), and use the statistical regression method to solve the various parameters in the above equation using a computer. The value of In order to carry out creep rupture tests under different stresses σ, the C value of the metal material is averaged, and equation (8) and equation (4) are combined and sorted out to obtain the specific form of equation (10). According to this equation, the creep rupture time of various metal materials under specific temperature and stress conditions can be estimated; In the calculation process of the creep life of the metal of the high-temperature convection heating surface of the power station boiler, only the change of the metal wall temperature is considered under stable working conditions, and the stress σ is converted with reference to the working fluid pressure in the pipeline under rated working conditions. In this way, formula (10) can be further simplified as follows: (11) From the above formula, we can find that the creep life of metal is only related to the C value and its working temperature, and the C value is only related to the material type itself. Therefore, in actual calculation, as long as the type of steel and the metal wall temperature used for the heating surface of this level can be determined, the corresponding creep rupture time can be easily estimated. In engineering calculations, the heated surface circular tube section can be approximately regarded as a thin-walled cylinder. Therefore, when using the Larson-Miller formula to calculate the creep rupture life of the pipe under a certain working condition, the following formula can be used to calculate the equivalent stress σ of the pipe wall: (12) Where: p is the working fluid pressure in the calibration tube, MPa; d is the actual outer diameter of the calibration tube at the calculation time, mm; δ is the actual wall thickness of the calibration tube at the calculation time, mm; d o is the original design outer diameter of the calibration tube, mm; δ w To check the wall thickness of the pipe due to corrosion, mm; δ n To check the wall thickness of the inner wall of the tube reduced due to oxidation, mm; δ m Check the thickness of the outer wall of the tube reduced due to the wear of flue gas and fly ash, mm; Since the working fluid pressure measurement points of the boiler are mostly arranged in the inlet and outlet manifolds of each level of heating surface, the average pressure of the working fluid at the inlet and outlet of the heating surface is measured instead of the working fluid pressure required in the calculation formula (5). Therefore, it is necessary to perform an approximate conversion on this measurement to obtain the working fluid pressure in the calibration pipe section. The estimation method is shown in the following formula: (13) Where: p i 、p o is the pressure measurement value in the inlet (outlet) header of the heated surface where the calibration pipe is located, MPa; x is the distance between the calibration pipe section and the inlet header of the heated surface, m; l is the distance between the inlet and outlet headers of the heated surface where the calibration pipe is located, m; Then the creep rupture time of the boiler superheater tube at the temperature and pressure can be estimated. By calculating the operating time and creep rupture time at various temperatures, the life loss of the metal tube can be obtained, and the medium pressure, temperature, component wall temperature, time and load value ranges can be set.

[0009] S3. The online monitoring device server performs data screening and preprocessing on the real-time uploaded data. If there are data values ​​outside the set data range in the uploaded real-time data, the online monitoring device server performs a buzzer alarm for the expiration of the life of the measuring point location area where the corresponding data is uploaded, and replaces the boiler superheat tubes in the area.

[0010] Preferably, in steps S1-S3, the overall communication structure of the data system consists of five major parts: a DCS system, a DAS system, a SIS system, a wall temperature online monitoring system server and a wall temperature online monitoring system client terminal.

[0011] Preferably, in steps S1-S3, the collected data of the measuring point position is first entered into the DCS database for real-time storage and recording, and then uploaded to the application server. Finally, the above measuring point data is displayed on the dedicated software of the display device of the client workstation.

[0012] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, a plurality of medium pressure sensors, temperature sensors, component wall temperature sensors, time counters and load sensors are distributed and installed at the corresponding measuring points of the boiler superheater tube, and a DCS configuration system IT communication is established within the plant area to collect the data of the sensors in real time and upload them to the subsequent server, calculate the creep rupture time of the metal material under a specific temperature and stress, and then estimate the creep rupture time of the boiler superheater tube under the temperature and pressure. By calculating the operating time and creep rupture time at various temperatures, the life loss of the metal tube can be obtained, and reasonable medium pressure, temperature, component wall temperature, time and load data are set. Value range, the online monitoring device server performs data screening and preprocessing on the real-time uploaded data. If there are data values ​​outside the set data range in the uploaded real-time data, the online monitoring device server performs a buzzer alarm for the expiration of the life of the measuring point location area where the corresponding data is uploaded, and replaces the boiler superheater tubes in this area. Through the above settings, the boiler metal heating surface life assessment method only uses the calculation method of high-temperature creep and high-temperature corrosion damage to assess the life of the boiler superheater tubes. At the same time, it is equipped with reasonable real-time monitoring of medium pressure, temperature, component wall temperature, time and load data, which is convenient for real-time monitoring and early warning of the boiler superheater tubes. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the basic principle architecture of online monitoring of the present invention; Figure 2 It is a schematic diagram of the principle architecture of the online monitoring data acquisition and transmission system of the present invention; Figure 3 It is a schematic diagram of the communication system architecture of the present invention. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] See also Figure 1-3 , the present invention provides a technical solution: A boiler metal heating surface life assessment method includes an online boiler data system, an online monitoring device server and a client, wherein the online boiler data system includes a DCS configuration system IT communication module and a measuring point monitoring data module; The online monitoring device server provides data processing services for data screening module, preprocessing module, over-limit alarm module, component monitoring database module, creep fatigue damage calculation module and life damage result database module. The component monitoring database module includes data collection and storage of medium pressure, temperature, component wall temperature, time and load. The life damage result database module includes statistics on creep and fatigue damage conditions. The client includes a client terminal module, which is used for monitoring and life damage data query, printing and backup processing.

[0016] Boiler metal heating surface life assessment method: S1. Install several medium pressure sensors, temperature sensors, component wall temperature sensors, time counters and load sensors at the corresponding measuring points of the boiler superheater tubes, and establish a DCS configuration system IT communication within the factory to collect the sensor data in real time and upload it to the subsequent server.

[0017] S2. Select several critical temperature values ​​of the boiler superheater tube when it is heated, and simulate and calculate the stress creep rupture time of the tube wall material at the above temperature values. The Larson-Miller formula is the most widely used in the time-temperature parameter method.

[0018] The creep rate can be described by the following formula: (1) Where: A——empirical constant; R——gas constant; T——absolute temperature of metal; Q – Creep activation energy.

[0019] The creep rupture time τ is inversely proportional to the creep velocity v, so: (2) Taking the logarithm of both sides of the equation gives: (3) Assuming A is a material constant and Q is a function of stress, let , then the above formula can be rewritten as: (4) P(σ) in the above formula is called the thermal intensity parameter, also known as the Larson-Miller parameter.

[0020] The functional relationship between thermal parameters and stress and the constant C related to metal materials are generally obtained through creep rupture tests. In the test, a higher temperature is selected to shorten the test time. When the stress magnitude remains constant: (5) Under the condition of equal stress, choose two different temperatures By conducting separate tests, two different break times can be obtained. , and substitute it into formula (5) and calculate to get the C value; (6) (7) By selecting n different stresses σ for creep rupture tests, n different C values ​​C (=1, 2, 3..n) can be obtained according to formula (6). The C value of the metal material can also be obtained by averaging these n values.

[0021] According to the test data, a functional relationship of P(σ) is fitted. Under normal conditions, the empirical function form of P(σ) is considered to be a high-order polynomial with lgσ as the independent variable: (8) Combining equation (8) with equation (4): (9) Then it is organized into the form of f(τ,σ,T), then: (10) Substitute the stress values ​​under different test conditions into equation (8), and use the statistical regression method to solve the various parameters in the above equation using a computer. The value of In order to carry out creep rupture tests under different stresses σ, the C value of the metal material is averaged, and equation (8) and equation (4) are combined and sorted out to obtain the specific form of equation (10). According to this equation, the creep rupture time of various metal materials under specific temperature and stress conditions can be estimated; In the calculation process of the creep life of the metal of the high-temperature convection heating surface of the power station boiler, only the change of the metal wall temperature is considered under stable working conditions, and the stress σ is converted with reference to the working fluid pressure in the pipeline under rated working conditions. In this way, formula (10) can be further simplified as follows: (11) From the above formula, we can find that the creep life of metal is only related to the C value and its operating temperature, and the C value is only related to the type of material itself. Therefore, in actual calculations, as long as the type of steel and the metal wall temperature used in the heating surface of this level can be determined, the corresponding creep rupture time can be easily estimated.

[0022] In engineering calculations, the heated surface circular tube section can be approximately regarded as a thin-walled cylinder. Therefore, when using the Larson-Miller formula to calculate the creep rupture life of the pipe under a certain working condition, the following formula can be used to calculate the equivalent stress σ of the pipe wall: (12) Where: p is the working fluid pressure in the calibration tube, MPa; d is the actual outer diameter of the calibration tube at the calculation time, mm; δ is the actual wall thickness of the calibration tube at the calculation time, mm; d o is the original design outer diameter of the calibration tube, mm; δ w To check the wall thickness of the pipe due to corrosion, mm; δ n To check the wall thickness of the inner wall of the tube reduced due to oxidation, mm; δ m Check the thickness of the outer wall of the tube reduced due to the wear of flue gas and fly ash, mm; Since the working fluid pressure measurement points of the boiler are mostly arranged in the inlet and outlet manifolds of each level of heating surface, the average pressure of the working fluid at the inlet and outlet of the heating surface is measured instead of the working fluid pressure required in the calculation formula (5). Therefore, it is necessary to perform an approximate conversion on this measurement to obtain the working fluid pressure in the calibration pipe section. The estimation method is shown in the following formula: (13) Where: p i 、p o is the pressure measurement value in the inlet (outlet) header of the heated surface where the calibration pipe is located, MPa; x is the distance between the calibration pipe section and the inlet header of the heated surface, m; l is the distance between the inlet and outlet headers of the heated surface where the calibration pipe is located, m; Then the creep rupture time of boiler superheater tube under the temperature and pressure is estimated. By calculating the operation time and creep rupture time under various temperatures, the life loss of the metal tube can be obtained. The medium pressure, temperature, component wall temperature, time and load value range are set. The wall thickness reduction value of the high-temperature convection heating surface caused by the corrosion of the smoke outside the tube and the high-temperature steam inside the tube is generally calculated according to the algorithm provided in the "Mechanical and Electrical Engineering Metal Materials Manual". The following is a calculation method based on commonly used steel Take this as an example to briefly describe the calculation process: (14)

[0023] (15)

[0024] (16)

[0025] The reduction in wall thickness of the outer wall of the heating surface tube due to flue gas and fly ash abrasion The empirical formula can be used for estimation: (17)

[0026] Then the creep rupture time of the boiler superheater tube at the temperature and pressure can be estimated. By calculating the operating time and creep rupture time at various temperatures, the life loss of the metal tube can be obtained, and the medium pressure, temperature, component wall temperature, time and load value ranges can be set.

[0027] S3. The online monitoring device server performs data screening and preprocessing on the real-time uploaded data. If there are data values ​​outside the set data range in the uploaded real-time data, the online monitoring device server performs a buzzer alarm for the expiration of the life of the measuring point location area where the corresponding data is uploaded, and replaces the boiler superheat tubes in the area.

[0028] In steps S1-S3, the overall communication structure of the data system consists of five parts: DCS system, DAS system, SIS system, wall temperature online monitoring system server and wall temperature online monitoring system client terminal. Among them, the DAS system collects the measurement point data signal to the front-end machine through sensors and timers connected to the on-site thermal measurement points, and connects to the DCS system through the communication card of the front-end machine. Then the measurement parameters are sent to the SIS system database by the interface machine between the DCS system and the SIS system. The wall temperature online monitoring system server located in the power plant information center is connected to the database server through the SIS network, reads the original data of the thermal measurement points from the database, and stores the results in the database of the server side of this system after calculation by the wall temperature monitoring system model, and returns the results to the system client terminal in the control room in the form of dynamic curves and chart data, providing guidance and reference for the operating personnel to adjust the control.

[0029] In steps S1-S3, the collected data of the measuring point location is first entered into the DCS database for real-time storage and recording, and then uploaded to the application server. Finally, the above measuring point data is displayed on the dedicated software of the display device of the client workstation.

[0030] The life assessment of the boiler heating surface should be based on its damage pattern over time. The damage to the superheater metal tube is mainly caused by long-term high-temperature creep, stress fatigue damage on the working fluid side, and high-temperature corrosion thinning on the fire side.

[0031] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for evaluating the life of a boiler metal heating surface, comprising an online boiler data system, an online monitoring device server and a client, characterized in that: The online boiler data system includes the DCS configuration system IT communication module and the measurement point monitoring data module; The online monitoring device server provides data processing services for data screening module, preprocessing module, over-limit alarm module, component monitoring database module, creep fatigue damage calculation module and life damage result database module. The component monitoring database module includes data collection and storage of medium pressure, temperature, component wall temperature, time and load. The life damage result database module includes statistics of creep and fatigue damage conditions. The client includes a client terminal module, which is used for monitoring and life damage data query, printing and backup processing. Boiler metal heating surface life assessment method: S1. Install several medium pressure sensors, temperature sensors, component wall temperature sensors, time counters and load sensors at the corresponding measuring points of the boiler superheater tubes, and establish a DCS configuration system IT communication within the plant to collect sensor data in real time and upload it to the subsequent server; S2. Select several critical temperature values ​​of the boiler superheater tube when it is heated, and simulate and calculate the stress creep rupture time of the tube wall material at the above temperature values. The Larson-Miller formula is widely used in the time-temperature parameter method; The creep rate can be described by the following formula: （1） Where: A——empirical constant; R——gas constant; T——absolute temperature of metal; Q – Creep activation energy; The creep rupture time τ is inversely proportional to the creep velocity v, so: （2） Taking the logarithm of both sides of the equation gives: （3） Assuming A is a material constant and Q is a function of stress, let , then the above formula can be rewritten as: （4） P(σ) in the above formula is called the thermal intensity parameter, also known as the Larson-Miller parameter; The functional relationship between thermal parameters and stress and the constant C related to metal materials are generally obtained through creep rupture tests. In the test, a higher temperature is selected to shorten the test time. When the stress magnitude remains constant: （5） Under the condition of equal stress, choose two different temperatures By conducting separate tests, two different break times can be obtained. , and substitute it into formula (5) and calculate to get the C value; （6） （7） By selecting n different stresses σ for creep rupture tests, n different C values ​​C (=1, 2, 3..n) can be obtained according to formula (6). The C value of the metal material can also be obtained by averaging these n values. According to the test data, a functional relationship of P(σ) is fitted. Under normal conditions, the empirical function form of P(σ) is considered to be a high-order polynomial with lgσ as the independent variable: （8） Combining equation (8) with equation (4): （9） Then it is organized into the form of f(τ,σ,T), then: （10） Substitute the stress values ​​under different test conditions into equation (8), and use the statistical regression method to solve the various parameters in the above equation using a computer. The value of In order to carry out creep rupture tests under different stresses σ, the C value of the metal material is averaged, and equation (8) and equation (4) are combined and sorted out to obtain the specific form of equation (10). According to this equation, the creep rupture time of various metal materials under specific temperature and stress conditions can be estimated; In the calculation process of the creep life of the metal of the high-temperature convection heating surface of the power station boiler, only the change of the metal wall temperature is considered under stable working conditions, and the stress σ is converted with reference to the working fluid pressure in the pipeline under rated working conditions. In this way, formula (10) can be further simplified as follows: （11） From the above formula, we can find that the creep life of metal is only related to the C value and its working temperature, and the C value is only related to the material type itself. Therefore, in actual calculation, as long as the type of steel and the metal wall temperature used for the heating surface of this level can be determined, the corresponding creep rupture time can be easily estimated. In engineering calculations, the heated surface circular tube section can be approximately regarded as a thin-walled cylinder. Therefore, when using the Larson-Miller formula to calculate the creep rupture life of the pipe under a certain working condition, the following formula can be used to calculate the equivalent stress σ of the pipe wall: （12） Where: p is the working fluid pressure in the calibration tube, MPa; d is the actual outer diameter of the calibration tube at the calculation time, mm; δ is the actual wall thickness of the calibration tube at the calculation time, mm; d o is the original design outer diameter of the calibration tube, mm; δ w To check the wall thickness of the pipe due to corrosion, mm; δ n To check the wall thickness of the inner wall of the tube reduced due to oxidation, mm; δ m Check the thickness of the outer wall of the tube reduced due to the wear of flue gas and fly ash, mm; Since the working fluid pressure measurement points of the boiler are mostly arranged in the inlet and outlet manifolds of each level of heating surface, the average pressure of the working fluid at the inlet and outlet of the heating surface is measured instead of the working fluid pressure required in the calculation formula (5). Therefore, it is necessary to perform an approximate conversion on this measurement to obtain the working fluid pressure in the calibration pipe section. The estimation method is shown in the following formula: （13） Where: p i 、p o is the pressure measurement value in the inlet (outlet) header of the heated surface where the calibration pipe is located, MPa; x is the distance between the calibration pipe section and the inlet header of the heated surface, m; l is the distance between the inlet and outlet headers of the heated surface where the calibration pipe is located, m; Then the creep rupture time of boiler superheater tube under the temperature and pressure is estimated. By calculating the operation time and creep rupture time under various temperatures, the life loss of the metal tube can be obtained. The medium pressure, temperature, component wall temperature, time and load value range are set. S3. The online monitoring device server performs data screening and preprocessing on the real-time uploaded data. If there are data values ​​outside the set data range in the uploaded real-time data, the online monitoring device server performs a buzzer alarm for the expiration of the life of the measuring point location area where the corresponding data is uploaded, and replaces the boiler superheat tubes in the area.

2. A method for evaluating the life of a boiler metal heating surface according to claim 1, characterized in that: In steps S1-S3, the overall communication structure of the data system consists of five parts: DCS system, DAS system, SIS system, wall temperature online monitoring system server and wall temperature online monitoring system client terminal.

3. The method for evaluating the life of a boiler metal heating surface according to claim 1, characterized in that: In steps S1-S3, the collected data of the measuring point location is first entered into the DCS database for real-time storage and recording, and then uploaded to the application server. Finally, the above measuring point data is displayed on the dedicated software of the display device of the client workstation.

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