A real-time calculation method for leakage amount of boiler four tubes

Abstract

The application discloses a kind of boiler four tube leakage amount real-time calculation method, comprising: four parts of water vapor source in flue gas at economizer outlet, which are water vapor produced by moisture of coal into furnace, water vapor generated after hydrogen element combustion, water vapor contained in air and water vapor generated after boiler four tube leakage, respectively calculate the water vapor content of each part, and the boiler four tube leakage amount can be calculated using material balance principle.The method can calculate the leakage amount of boiler four tube by automatically collecting the coal quality test results of unit into furnace and the flue gas data at economizer outlet, and carry out graded early warning according to the calculation results.The application realizes the calculation and early warning of boiler four tube leakage, and can be used for boiler four tube state monitoring and related fault diagnosis, etc., to facilitate the operation personnel to master the state of boiler four tube in real time, arrange maintenance work in time, and improve the operation safety of unit.

Description

Technical Field

[0001] This invention belongs to the power engineering industry, specifically relating to a method for real-time calculation of leakage in four boiler tubes, which can be applied to boiler tube condition monitoring and related fault diagnosis. Background Technology

[0002] As the single-unit capacity of coal-fired power plants gradually increases, boiler design and manufacturing are also developing towards higher parameters and larger capacity. As the heating surface is sandwiched between the working medium and flue gas, the pressure and temperature of the boiler's four tubes are gradually increasing, which leads to increased erosion and wear on the boiler's four tubes.

[0003] Currently, power plant staff primarily assess the equipment's condition based on signs of leaks in the boiler's four main tubes, such as abnormally increased feedwater flow exceeding steam flow, unusual noises at the leak point, increased furnace pressure, and increased induced draft fan current. These methods require extensive experience, are difficult to apply, and lack quantifiable and controllable data support. This makes it challenging to detect and address minor leaks promptly, potentially leading to escalating losses. Summary of the Invention

[0004] The purpose of this invention is to provide a real-time calculation method for the leakage of four boiler tubes. By utilizing online monitoring data of the composition of flue gas at the economizer outlet, chemical analysis data of coal entering the boiler, and atmospheric environmental data, the change in the amount of water vapor in the boiler flue gas is calculated online, thereby obtaining the leakage of the four boiler tubes. This solves the problem that it was previously impossible to accurately measure the degree of leakage of the four boiler tubes, and realizes online monitoring of the leakage of the four boiler tubes, providing a basis for power plant operation and management personnel to make relevant maintenance decisions.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for real-time calculation of leakage in four boiler tubes, comprising:

[0007] The water vapor in the economizer outlet flue gas comes from four sources: water vapor produced by the moisture in the coal entering the furnace, water vapor generated after the combustion of hydrogen, water vapor contained in the air, and water vapor generated from leaks in the boiler's four tubes. The water vapor content of each source is calculated, and the leakage rate of the boiler's four tubes can be calculated using the material balance principle. The specific steps include:

[0008] (1) Calculate the water vapor flow rate in the flue gas at the economizer outlet; the specific calculation formula is as follows:

[0009]

[0010] In the formula:

[0011] —Water vapor flow rate in the economizer outlet flue gas, t / h;

[0012] —The percentage of water vapor partial pressure in the economizer outlet flue gas, %

[0013] p eco,out —Absolute pressure of flue gas at economizer outlet, kPa;

[0014] —Average flue gas velocity at the economizer outlet section, m / s;

[0015] A eco,out — Economizer outlet cross-sectional area, m² 2 ;

[0016] R g,H2O —Water vapor gas constant, taken as 461.92, J / (kg·K);

[0017] t eco,out — Economizer outlet flue gas temperature, °C;

[0018] (2) Calculate the steam flow rate generated by the moisture content of the coal entering the furnace;

[0019] (3) Calculate the steam flow rate generated by hydrogen elements in the coal entering the furnace;

[0020] (4) Calculate the steam flow rate in the boiler intake air;

[0021] (5) The leakage of the four tubes of the boiler was calculated;

[0022] (6) Early warning of leakage in four tubes of boiler

[0023] Considering that the changes in various parameters have different lag effects under the variable load conditions of the unit, a boiler four-tube leakage early warning system is implemented for the stable operation conditions of the unit.

[0024] First, the load change rate of the computer group before and after each minute is as follows:

[0025]

[0026] In the formula:

[0027] α — Unit load change rate, %

[0028] —Unit load at time i, MW;

[0029] —Unit load at time i-1, MW;

[0030] If the current unit load change rate is greater than 1%, the boiler four-tube leakage calculation program will not be triggered; if the current unit load change rate is less than 1%, the boiler four-tube leakage calculation program will be automatically triggered, and data will be captured to calculate the current boiler four-tube leakage. Based on the calculated boiler four-tube leakage value, a graded warning will be issued.

[0031] A further improvement of this invention is that, in step (2), the specific calculation formula is as follows:

[0032]

[0033] In the formula:

[0034] —The amount of water vapor generated by the moisture content of the coal fed into the furnace, in t / h;

[0035] — Boiler coal feed rate, t / h;

[0036] —Base moisture content of coal received into the furnace, %.

[0037] A further improvement of the present invention is that, in step (3), the specific calculation formula is as follows:

[0038]

[0039] In the formula:

[0040] — The amount of water vapor generated by the hydrogen element in the coal fed into the furnace, t / h;

[0041] — Boiler coal feed rate, t / h;

[0042] —Base moisture content of coal received into the furnace, %.

[0043] A further improvement of the present invention is that, in step (4), the specific calculation formula is as follows:

[0044] First, calculate the boiler inlet saturated steam pressure based on the boiler inlet air temperature;

[0045] When the intake air temperature At <0℃, the boiler inlet saturated steam pressure P air,b for:

[0046]

[0047] Where T is the thermodynamic temperature of the air at the boiler inlet, taken as T= +273.15, C1=-5674.5359, C2=6.3925247, C3=-0.9677843 10 -2 C4 = -0.62215701 10 -6 C5 = 0.20747825 10 -18 C6 = -0.9484024 10 -12 C7 = 4.1635019;

[0048] When the intake air temperature At >=0℃, the boiler inlet saturated steam pressure P air,b for:

[0049]

[0050] Where, C8 = -5800.2206, C9 = 1.3914993, C 10 =-0.048640239, C 11 =0.41764768 10 -4 C 12 =-0.14452093 10 -7 C 13 =6.5459673;

[0051] Then, calculate the steam flow rate in the boiler intake air.

[0052]

[0053] In the formula:

[0054] —Steam flow rate in boiler intake air, t / h;

[0055] —Relative humidity of boiler inlet air, %

[0056] — Boiler inlet air-water vapor saturation pressure, kPa;

[0057] —Boiler inlet air volumetric flow rate, km 3 / h;

[0058] —Air leakage coefficient from boiler furnace to economizer;

[0059] —Water vapor gas constant, taken as 461.92, J / (kg·K).

[0060] A further improvement of this invention is that, in step (5), the specific calculation formula is as follows:

[0061]

[0062] In the formula:

[0063] — The amount of steam generated by leakage in the four tubes of the boiler, in t / h.

[0064] The present invention has at least the following beneficial technical effects:

[0065] Compared to traditional methods that rely on abnormal parameters or phenomena and experience to diagnose boiler tube leaks after a tube rupture, this invention can calculate the leakage of all four boiler tubes in real time. It can detect and alert operators in the early stages of abnormalities, unaffected by operator experience levels, and the calculation results are real-time, accurate, and reliable. By employing the above technical solution and mathematical model, it overcomes the difficulties of traditional boiler tube anti-wear and anti-explosion monitoring, providing data support for unit operators to accurately grasp the status of the boiler tubes. Detailed Implementation

[0066] Exemplary embodiments of this disclosure will now be described in more detail. While exemplary embodiments of this disclosure are shown, it should be understood that this disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this disclosure and to fully convey its scope to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The invention will now be described in detail with reference to the embodiments.

[0067] This invention provides a real-time calculation method for boiler four-tube leakage, comprising: The water vapor in the economizer outlet flue gas originates from four sources: water vapor produced from the moisture in the incoming coal, water vapor generated after hydrogen combustion, water vapor contained in the air, and water vapor generated after leakage from the boiler four tubes. The water vapor content of each source is calculated, and the leakage of the boiler four tubes can be calculated using the material balance principle. The specific steps are as follows:

[0068] (1) Calculate the water vapor flow rate in the flue gas at the economizer outlet.

[0069]

[0070] In the formula:

[0071] —Water vapor flow rate in the economizer outlet flue gas, t / h;

[0072] —The percentage of water vapor partial pressure in the economizer outlet flue gas, %

[0073] p eco,out —Absolute pressure of flue gas at economizer outlet, kPa;

[0074] —Average flue gas velocity at the economizer outlet section, m / s;

[0075] A eco,out — Economizer outlet cross-sectional area, m² 2 ;

[0076] R g,H2O —Water vapor gas constant, taken as 461.92, J / (kg·K);

[0077] t eco,out — Economizer outlet flue gas temperature, °C;

[0078] (2) Calculate the steam flow rate generated by the moisture content of the coal fed into the furnace.

[0079]

[0080] In the formula:

[0081] —The amount of water vapor generated by the moisture content of the coal fed into the furnace, in t / h;

[0082] — Boiler coal feed rate, t / h;

[0083] —Base moisture content of coal received into the furnace, %.

[0084] (3) Calculate the steam flow rate generated by hydrogen elements in the coal fed into the furnace.

[0085]

[0086] In the formula:

[0087] — The amount of water vapor generated by the hydrogen element in the coal fed into the furnace, t / h;

[0088] — Boiler coal feed rate, t / h;

[0089] —Base moisture content of coal received into the furnace, %.

[0090] (4) Calculate the steam flow rate in the boiler intake air.

[0091] First, calculate the boiler inlet saturated steam pressure based on the boiler inlet air temperature.

[0092] When the intake air temperature At <0℃, the boiler inlet saturated steam pressure P air,b for:

[0093]

[0094] Where T is the thermodynamic temperature of the air at the boiler inlet, taken as T= +273.15, C1=-5674.5359, C2=6.3925247, C3=-0.9677843 10 -2 C4 = -0.62215701 10 -6 C5 = 0.20747825 10 -18 C6 = -0.9484024 10 -12 C7 = 4.1635019;

[0095] When the intake air temperature At >=0℃, the boiler inlet saturated steam pressure P air,b for:

[0096]

[0097] Where, C8 = -5800.2206, C9 = 1.3914993, C 10 =-0.048640239, C 11 =0.41764768 10 -4 C 12 =-0.14452093 10 -7 C 13 =6.5459673.

[0098] Then, calculate the steam flow rate in the boiler intake air.

[0099]

[0100] In the formula:

[0101] —Steam flow rate in boiler intake air, t / h;

[0102] —Relative humidity of boiler inlet air, %

[0103] — Boiler inlet air-water vapor saturation pressure, kPa;

[0104] —Boiler inlet air volumetric flow rate, km 3 / h;

[0105] —Air leakage coefficient from boiler furnace to economizer;

[0106] —Water vapor gas constant, taken as 461.92, J / (kg·K).

[0107] (5) Calculate the leakage of the four tubes of the boiler.

[0108]

[0109] In the formula:

[0110] — The amount of steam generated by leakage in the four tubes of the boiler, in t / h.

[0111] (6) Early warning of leakage in four tubes of boiler

[0112] Considering that the changes in various parameters have different lag effects under variable load conditions, the boiler four-tube leakage early warning is mainly aimed at the stable operation conditions of the unit.

[0113] First, the load change rate of the computer group before and after each minute is as follows:

[0114]

[0115] In the formula:

[0116] α — Unit load change rate, %

[0117] —Unit load at time i, MW;

[0118] —Unit load at time i-1, MW.

[0119] If the current unit load change rate is greater than 1%, the boiler four-tube leakage calculation program will not be triggered; if the current unit load change rate is less than 1%, the boiler four-tube leakage calculation program will be automatically triggered, and data will be captured to calculate the current boiler four-tube leakage. Based on the calculated boiler four-tube leakage value, a graded warning will be issued, as shown in Table 1.

[0120] Table 1. Early Warning Classification Table for Leakage in Four Boiler Tubes

[0121]

[0122] Different ranges can be set according to the unit capacity to achieve real-time online graded early warning of boiler four-tube leakage.

[0123] Application example:

[0124] The following table illustrates the calculations using the operating data of a 350,000 kW unit at a power plant at 10:45 AM on April 16, 2023:

[0125]

[0126] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for real-time calculation of leakage in four boiler tubes, characterized in that, include: The water vapor in the economizer outlet flue gas comes from four sources: water vapor produced by the moisture in the coal entering the furnace, water vapor generated after the combustion of hydrogen, water vapor contained in the air, and water vapor generated from leaks in the boiler's four tubes. The water vapor content of each source is calculated, and the leakage rate of the boiler's four tubes can be calculated using the material balance principle. The specific steps include: (1) Calculate the water vapor flow rate in the flue gas at the economizer outlet; the specific calculation formula is as follows: In the formula: —Water vapor flow rate in the economizer outlet flue gas, t / h; —The percentage of water vapor partial pressure in the economizer outlet flue gas, % p eco,out —Absolute pressure of flue gas at economizer outlet, kPa; —Average flue gas velocity at the economizer outlet section, m / s; A eco,out — Economizer outlet cross-sectional area, m² 2 ; R g,H2O —Water vapor gas constant, taken as 461.92, J / (kg·K); t eco,out — Economizer outlet flue gas temperature, °C; (2) Calculate the steam flow rate generated by the moisture content of the coal entering the furnace; (3) Calculate the steam flow rate generated by the hydrogen element in the coal entering the furnace; (4) Calculate the steam flow rate in the boiler intake air; (5) The leakage of the four tubes of the boiler was calculated; (6) Early warning of leakage in four tubes of boiler Considering that the changes in various parameters have different lag effects under the variable load conditions of the unit, a boiler four-tube leakage early warning system is implemented for the stable operation conditions of the unit. First, the load change rate of the computer group before and after each minute is as follows: In the formula: α — Unit load change rate, % —Unit load at time i, MW; —Unit load at time i-1, MW; If the current unit load change rate is greater than 1%, the boiler four-tube leakage calculation program will not be triggered; if the current unit load change rate is less than 1%, the boiler four-tube leakage calculation program will be automatically triggered, and data will be captured to calculate the current boiler four-tube leakage. Based on the calculated boiler four-tube leakage value, a graded warning will be issued.

2. The method for real-time calculation of leakage in a boiler's four tubes according to claim 1, characterized in that, In step (2), the specific calculation formula is as follows: In the formula: —The amount of water vapor generated by the moisture content of the coal fed into the furnace, in t / h; — Boiler coal feed rate, t / h; —Base moisture content of coal received into the furnace, %.

3. The method for real-time calculation of leakage in a boiler four-tube system according to claim 2, characterized in that, In step (3), the specific calculation formula is as follows: In the formula: — The amount of water vapor generated by the hydrogen element in the coal fed into the furnace, t / h; — Boiler coal feed rate, t / h; —Base moisture content of coal received into the furnace, %.

4. The method for real-time calculation of leakage in a boiler four-tube system according to claim 3, characterized in that, In step (4), the specific calculation formula is as follows: First, calculate the boiler inlet saturated steam pressure based on the boiler inlet air temperature; When the intake air temperature At <0℃, the boiler inlet saturated steam pressure P air,b for: Where T is the thermodynamic temperature of the air at the boiler inlet, taken as T= +273.15, C1=-5674.5359, C2=6.3925247, C3=-0.9677843 10 -2 C4 = -0.62215701 10 -6 C5 = 0.20747825 10 -18 C6 = -0.9484024 10 -12 C7 = 4.1635019; When the intake air temperature At >=0℃, the boiler inlet saturated steam pressure P air,b for: Where, C8 = -5800.2206, C9 = 1.3914993, C 10 =-0.048640239, C 11 =0.41764768 10 -4 C 12 =-0.14452093 10 -7 C 13 =6.5459673; Then, calculate the steam flow rate in the boiler intake air. In the formula: —Steam flow rate in boiler intake air, t / h; —Relative humidity of boiler inlet air, % — Boiler inlet air-water vapor saturation pressure, kPa; —Boiler inlet air volumetric flow rate, km 3 / h; —Air leakage coefficient from boiler furnace to economizer; —Water vapor gas constant, taken as 461.92, J / (kg·K).

5. The method for real-time calculation of leakage in a boiler's four tubes according to claim 4, characterized in that, In step (5), the specific calculation formula is as follows: In the formula: — The amount of steam generated by leakage in the four tubes of the boiler, in t / h.

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