Online pressure monitoring and automatic purging system and method for induced draft fan of thermal power plant

Abstract

The invention discloses an on-line pressure monitoring and automatic purging system and method for an induced draft fan of a thermal power plant. The system comprises a heat tracing pipe, a temperature controller B and an air pipe electromagnetic valve C, the heat tracing pipe is used for leading out smoke from the pressure measuring point A. A temperature controller B and an air pipe electromagnetic valve C are arranged at the tail end of the heat tracing pipe, the temperature controller B is used for measuring the temperature of the smoke in the heat tracing pipe, and the air pipe electromagnetic valve C is used for measuring the pressure of the smoke in the heat tracing pipe. The flue gas temperature and pressure in the heat tracing pipeline are respectively controlled to maintain normal levels, and pipeline blockage is prevented. The method comprises the steps that the normal temperature of flue gas in a flue is t1, and the temperature t2 of the flue gas in a heat tracing pipe is counted every 30 minutes; and if t2 is less than (t1-10) DEG C and the time exceeds 30 minutes, the heat tracing pipeline starts to heat until the temperature rises to (t1 + 10) DEG C. The problem that a pressure on-line monitoring system is prone to blockage is mainly solved.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal power generation, and in particular relates to an online pressure monitoring and automatic purging system and method for an induced draft fan in a thermal power plant. Background Art

[0002] Flue gas pressure is an important parameter in the operation of thermal power plants, and its stability is directly related to the safe operation of equipment. By real-time monitoring of flue gas pressure, abnormal pressure fluctuations, such as sudden increases or decreases, can be discovered in time. These abnormal conditions are often precursors to equipment failures or safety hazards. Timely measures can effectively prevent accidents and ensure the safety of personnel and equipment. The induced draft fan is an important equipment in a thermal power plant, and its operating status directly affects the safety and stability of the entire unit. By online monitoring of the pressure of the induced draft fan, the stability of the system where the induced draft fan is located can be judged in real time, which serves as an important basis for operation adjustment.

[0003] Due to the complexity of the induced draft fan operating environment and the characteristics of the monitoring system, the online monitoring of induced draft fan pressure is prone to blockage. There are two main reasons: 1. High temperature and high humidity environment: The flue gas in thermal power plants often contains high temperature and humidity. These factors can easily lead to condensation or water vapor condensation inside the monitoring equipment, which in turn affects the accuracy of the monitoring data and may increase the risk of blockage. 2. High concentration of dust: A large amount of dust is generated during the coal combustion process. When these dusts circulate inside the induced draft fan, they are easy to adhere to the surface or internal channels of the monitoring probe, and will cause blockage after long-term accumulation. Therefore, it is necessary to focus on solving the above two problems. Summary of the invention

[0004] The purpose of the present invention is to provide an online pressure monitoring and automatic purge system and method for induced draft fans in thermal power plants, which mainly solves the problem that the online pressure monitoring system is easily blocked. The system monitors the temperature and pressure of the pressure pipeline, and selects whether to heat or purge the pressure pipeline with air according to the judgment conditions set in advance, thereby solving the hidden dangers or problems of pipeline blockage.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: The present invention provides an online pressure monitoring and automatic purge system for induced draft fans in thermal power plants, comprising a heat tracing pipe, a temperature controller B and an air pipe solenoid valve C; The heating pipe is used to lead the flue gas from the pressure measuring point A. A temperature controller B and an air pipe solenoid valve C are set at the end of the heating pipe. The temperature controller B is used to measure the flue gas temperature in the heating pipe, and the air pipe solenoid valve C is used to measure the flue gas pressure in the heating pipe. According to the measured flue gas temperature and flue gas pressure, the flue gas temperature and pressure in the heating pipeline are controlled to maintain normal levels to prevent pipeline blockage.

[0006] A further improvement of the present invention is that the pressure measuring point A is located on a straight pipe section, and the straight pipe length before the measuring point is not less than 4 times the equivalent diameter, and the straight pipe length after the measuring point is not less than 3 times the equivalent diameter.

[0007] A further improvement of the present invention is that the pressure measuring point A can be set in the contraction pipe section where the contraction angle α is greater than 60°, while satisfying that the length of the contraction pipe section before the measuring point is not less than 2 times the equivalent diameter, and the length of the contraction pipe section after the measuring point is not less than 1 times the equivalent diameter.

[0008] The present invention also provides an online pressure monitoring and automatic purging method for an induced draft fan in a thermal power plant. The method is based on the online pressure monitoring and automatic purging system for an induced draft fan in a thermal power plant, and comprises: The normal temperature of flue gas in the flue is t1, and the flue gas temperature t2 in the heating pipe is measured every 30 minutes; If t2 is less than (t1-10)℃ and the time exceeds 30 minutes, the heating pipeline will start to heat until the temperature reaches (t1+10)℃.

[0009] A further improvement of the present invention is that it also includes: The relationship between the flue gas flow rate Q and the pressure P in the smoke and air system pipeline of a thermal power plant is P=k1Q+A1. When the pipeline system is normal, the slope k1 is a constant. When the pipeline is blocked, the slope gradually increases to the slope k1. Perform a pressure test every 30 seconds. When k2 / k1 is greater than 1.2, open solenoid valve C for air purge for 30 seconds.

[0010] A further improvement of the present invention is that, when the flue gas pipeline is normal, k1 and A1 in the formula P=k1Q+A1 are calculated by monitoring the system flow Q under two different working conditions displayed on the dial and the pressure P obtained by the test.

[0011] A further improvement of the present invention is that after the system has been running for a period of time, k and A gradually change, and when the system resistance increases, the k value gradually increases.

[0012] A further improvement of the present invention is that k2 and A2 in the formula P=k2Q+A2 are calculated by monitoring the system flow Q under two different working conditions displayed on the dial and the pressure P obtained by the test.

[0013] A further improvement of the present invention is that a thermocouple is used to test the flue gas temperature t2 in the heating pipe.

[0014] A further improvement of the present invention is that a pressure gauge is used to test the flue gas pressure in the heating pipe.

[0015] Compared with the prior art, the present invention has at least the following beneficial technical effects: The on-line pressure monitoring and automatic purging system for the induced draft fan of a thermal power plant provided by the present invention monitors the temperature and pressure parameters in real time by setting a temperature controller and an air pipe solenoid valve, keeps the deviation of the temperature and pressure level of the sampling pipeline from the temperature and pressure level of the main pipeline always within a controllable range, and greatly reduces the probability of pipeline blockage caused by water vapor condensation and smoke solidification.

[0016] The method for online pressure monitoring and automatic purging of the induced draft fan of a thermal power plant provided by the present invention creatively introduces a key judgment parameter K (P=k1Q+A1). Since the pressure P changes with the system flow Q, if the pipeline is judged to be blocked only by detecting the pressure parameter, the error will be large. The principle on which the present invention is based is: if the system is blocked, the corresponding pressure rises at the same flow, and the K value becomes larger. Therefore, the coefficient K can more accurately and sensitively reflect the system blockage situation under dynamic conditions. When the ratio k2 / k1 of K2 to the initial K1 value corresponding to the system is greater than 1.2, it is judged that the pipeline may be blocked and purging is performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 The present invention is a flow chart of the on-line pressure monitoring and automatic purging method of the induced draft fan in a thermal power plant. DETAILED DESCRIPTION

[0019] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0020] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0021] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0022] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0024] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0025] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0026] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0027] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0028] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0029] Example 1 The invention provides an online pressure monitoring and automatic purging system for an induced draft fan in a thermal power plant, comprising a heating pipe, a temperature controller B and an air pipe solenoid valve C; the heating pipe is used to lead out flue gas from a pressure measuring point A, the temperature controller B and the air pipe solenoid valve C are arranged at the end of the heating pipe, the temperature controller B is used to measure the flue gas temperature in the heating pipe, the air pipe solenoid valve C is used to measure the flue gas pressure in the heating pipe, and according to the measured flue gas temperature and flue gas pressure, the flue gas temperature and pressure in the heating pipeline are respectively controlled to maintain normal levels to prevent pipeline blockage.

[0030] The system of the present invention can monitor the flue gas temperature and pressure in the heating pipe in real time to ensure the accuracy and timeliness of the data. Through the feedback of the temperature controller B and the air pipe solenoid valve C, the temperature and pressure state of the flue gas can be quickly understood, providing a basis for subsequent control and adjustment. By maintaining the flue gas temperature and pressure in the heating pipeline at a normal level, the system can effectively prevent the problem of pipeline blockage. This not only improves the operating efficiency of the equipment, but also reduces the downtime and maintenance time and cost caused by pipeline blockage. The system adopts an automated control method, which can automatically adjust the temperature and pressure of the heating pipeline according to the measured flue gas temperature and pressure. This automated control reduces manual intervention and improves the stability and reliability of the system. Through real-time monitoring and automatic adjustment, the system can promptly detect and deal with potential safety hazards, such as excessive flue gas temperature or pressure. This helps to reduce the risk of safety accidents caused by equipment failure or improper operation.

[0031] In this embodiment, the pressure measuring point A is located on the straight pipe section, and the straight pipe length before the measuring point is not less than 4 times the equivalent diameter, and the straight pipe length after the measuring point is not less than 3 times the equivalent diameter. The present invention sets the pressure measuring point A on the straight pipe section, which can ensure that the measured pressure value is closer to the actual flue gas flow pressure. The flow on the straight pipe section is more stable, reducing the flow disturbance caused by factors such as pipe bending and diameter change, thereby improving the accuracy of the measurement. The straight pipe length before the measuring point is not less than 4 times the equivalent diameter, and the straight pipe length after the measuring point is not less than 3 times the equivalent diameter. It helps to reduce the measurement error caused by local resistance of the pipeline, eddy current, etc. These length requirements ensure that the flow state before and after the measurement area is relatively stable, reducing the measurement error caused by changes in the flow state. A stable flow state helps to maintain the stability of the measured value. By ensuring that there is enough straight pipe section length before and after the measuring point, the measured value can be made more stable, reducing the fluctuation of the measured value caused by the fluctuation of the flow state. Accurate measurement values ​​are crucial for the control and regulation of the system. By ensuring the rationality of the measurement point location, the reliability and stability of the system can be improved, ensuring that the system can accurately and timely respond to changes in the flue gas flow state. The present invention sets the measurement point on the straight pipe section and ensures that there is sufficient straight pipe section length, which can make the installation and maintenance of the measurement point more convenient. It avoids the installation difficulties and maintenance complexity caused by factors such as pipe bending and diameter change.

[0032] In this embodiment, the pressure measuring point A can set the pressure measuring point on the contraction pipe section with a contraction angle α greater than 60°, and at the same time meet the requirements that the length of the contraction pipe section before the measuring point is not less than 2 times the equivalent diameter, and the length of the contraction pipe section after the measuring point is not less than 1 times the equivalent diameter. The present invention allows the pressure measuring point to be set on the contraction pipe section with a contraction angle α greater than 60°, so that the system can adapt to more complex pipeline layouts. By ensuring that the length of the contraction pipe section before the measuring point is not less than 2 times the equivalent diameter, and the length of the contraction pipe section after the measuring point is not less than 1 times the equivalent diameter, the influence of the contraction section on the flow state can be minimized. In this way, it can be ensured that the pressure value obtained at the measuring point is closer to the actual flow pressure, and the accuracy of the measurement is improved. When setting the measuring point on the contraction pipe section, if the contraction angle is too large or the contraction section length is insufficient, the flow state may be unstable, thereby introducing a measurement error. By limiting the contraction angle and the contraction section length, this error can be reduced, making the measurement result more reliable. Even in areas where the flow state is relatively complex such as the contraction pipe section, the system can still maintain stable measurement performance through reasonable measurement point position and length requirements. This enhances the robustness of the system, allowing the system to accurately reflect the flow state under various working conditions. At the same time, it allows the measurement points to be set on the contraction pipe section, which helps to simplify the pipeline layout and reduce the number of pipeline connections and brackets. This not only reduces the complexity of system integration, but also facilitates subsequent debugging and maintenance work.

[0033] Example 2 The thermal power plant induced draft fan online pressure monitoring and automatic purging system provided by the present invention draws out flue gas from the pressure measuring point A through a heat tracing pipe. A temperature controller B and an air pipe solenoid valve C are arranged at the end of the heat tracing pipe to respectively control the flue gas temperature and pressure in the heat tracing pipe to maintain normal levels. When the flue gas temperature is lower than the normal value, heating is performed to prevent water vapor condensation; when the pressure is high, purging is performed to remove dust and prevent pipeline blockage.

[0034] The specific implementation methods are as follows: 1. Determine the location of the flue pressure measuring point A. According to relevant specifications, it is recommended that the pressure measuring point be located on the straight pipe section, and the straight pipe length before the measuring point is not less than 4 times the equivalent diameter, and the straight pipe section length after the measuring point is not less than 3 times the equivalent diameter. Due to the actual conditions on site, the present invention proposes to set a pressure measuring point on a contraction pipe section with a contraction angle α greater than 60°, and at the same time, the contraction pipe section length before the measuring point is not less than 2 times the equivalent diameter, and the contraction pipe section length after the measuring point is not less than 1 times the equivalent diameter.

[0035] 2. Temperature control loop: The normal temperature of flue gas in the flue is t1. By setting a thermocouple in the heating pipe section, the flue gas temperature t2 in the heating pipe is measured every 30 minutes. If t2 is less than (t1-10)℃ and the time exceeds 30 minutes, the heating pipe starts to heat until the temperature rises to (t1+10)℃.

[0036] 3. Determine the slope of the characteristic curve of the pipeline system: The relationship between the flue gas flow rate Q and the pressure P of the smoke and air system pipeline of a thermal power plant can be simplified to P=k1Q+A1. When the pipeline system is normal, the slope k1 is a constant. When the pipeline is blocked, the slope will gradually increase to k2.

[0037] 4. Pressure control circuit: Perform a pressure test every 30 seconds. When the k2 / k1 calculated by the algorithm is greater than 1.2, open the solenoid valve C for air purge for 30 seconds.

[0038] 5. When the temperature control circuit or the pressure control circuit meets the purging conditions, purging will be performed.

[0039] Example 3 like Figure 1 As shown, the method for online pressure monitoring and automatic purging of induced draft fans in thermal power plants provided by the present invention comprises: The normal temperature of flue gas in the flue is t1, and the flue gas temperature t2 in the heating pipe is measured every 30 minutes; If t2 is less than (t1-10)℃ and the time exceeds 30 minutes, the heating pipeline will start to heat until the temperature reaches (t1+10)℃.

[0040] In this embodiment, it also includes: the relationship between the flue gas flow Q and the pressure P of the smoke and air system pipeline of the thermal power plant is P=k1Q+A1, when the pipeline system is normal, the slope k1 is a constant, and when the pipeline is blocked, the slope gradually increases to the slope k1; a pressure test is performed every 30 seconds, and when k2 / k1 is greater than 1.2, the solenoid valve C is opened for air blowing for 30 seconds.

[0041] In this embodiment, when the flue gas pipeline is normal, k1 and A1 in the formula P=k1Q+A1 are calculated by monitoring the system flow Q under two different working conditions displayed on the dial and the pressure P obtained by the test.

[0042] In this embodiment, after the system runs for a period of time, k and A gradually change, and when the system resistance increases, the k value gradually increases.

[0043] In this embodiment, k2 and A2 in the formula P=k2Q+A2 are calculated by monitoring the system flow Q under two different working conditions displayed on the dial and the pressure P obtained by the test.

[0044] In this embodiment, a thermocouple is used to test the flue gas temperature t2 in the heating pipe.

[0045] In this embodiment, a pressure gauge is used to test the flue gas pressure in the heating pipe.

[0046] Example 4 The air and smoke system of a 660MW unit in China is equipped with a single induced draft fan with a rated speed of 990r / min. During normal operation, the pressure measuring pipe is often blocked, resulting in inaccurate data. According to the method proposed in the present invention, the pressure measuring point is first determined at a suitable place where the flue contracts. After the installation of this system, there has been no pressure pipe blockage problem in operation for half a year, and good results have been achieved. The specific data are as follows: Pressure determination: First, the system was calibrated, and the flow and pressure parameters under two working conditions were obtained as follows: (307m 3 / s, 5612Pa)(321m 3 / s, 6710Pa), then according to the relationship P=k1Q+A1, k1=78.4, A1=-17289. According to this patent, when the system parameters change and the calculated k value is greater than 94, purge is performed.

[0047] Temperature judgment: Under normal circumstances, the system temperature varies between 110℃ and 130℃. The difference between the real-time monitored pipeline temperature data and the system temperature data determines whether to perform purging. Assuming that the system temperature is 115℃ at this time, if the pipeline temperature monitored within 30 minutes is less than 105℃, the purging action is performed. At the same time, the heating pipe starts heating until the pipeline temperature reaches 125℃.

[0048] The on-site installation is shown in the figure: the flue gas is led out through a pressure pipe, and the flue gas temperature and pressure are tested in the heating pipe to determine whether to heat or purge according to the method proposed by the present invention.

[0049] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0050] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. The online pressure monitoring and automatic purge system of the induced draft fan in a thermal power plant is characterized by: Including heating pipe, temperature controller B and air pipe solenoid valve C; The heating pipe is used to lead the flue gas from the pressure measuring point A. A temperature controller B and an air pipe solenoid valve C are set at the end of the heating pipe. The temperature controller B is used to measure the flue gas temperature in the heating pipe, and the air pipe solenoid valve C is used to measure the flue gas pressure in the heating pipe. According to the measured flue gas temperature and flue gas pressure, the flue gas temperature and pressure in the heating pipeline are controlled to maintain normal levels to prevent pipeline blockage.

2. The on-line pressure monitoring and automatic purge system for induced draft fans in thermal power plants according to claim 1 is characterized in that: The location of pressure measuring point A is on the straight pipe section, and the straight pipe length before the measuring point is not less than 4 times the equivalent diameter, and the straight pipe length after the measuring point is not less than 3 times the equivalent diameter.

3. The on-line pressure monitoring and automatic purging system for induced draft fans in thermal power plants according to claim 1 is characterized in that: Pressure measuring point A can be set at a contraction pipe section where the contraction angle α is greater than 60°, while satisfying that the length of the contraction pipe section before the measuring point is not less than 2 times the equivalent diameter, and the length of the contraction pipe section after the measuring point is not less than 1 times the equivalent diameter.

4. A method for online pressure monitoring and automatic purging of induced draft fans in thermal power plants, characterized in that: The method is based on the on-line pressure monitoring and automatic purge system for induced draft fans in thermal power plants as described in claim 1, comprising: The normal temperature of flue gas in the flue is t1, and the flue gas temperature t2 in the heating pipe is measured every 30 minutes; If t2 is less than (t1-10)℃ and the time exceeds 30 minutes, the heating pipeline will start to heat until the temperature reaches (t1+10)℃.

5. The method for online pressure monitoring and automatic purging of induced draft fans in thermal power plants according to claim 4, characterized in that: Also includes: The relationship between the flue gas flow rate Q and the pressure P in the smoke and air system pipeline of a thermal power plant is P=k1Q+A1. When the pipeline system is normal, the slope k1 is a constant. When the pipeline is blocked, the slope gradually increases to the slope k1. Perform a pressure test every 30 seconds. When k2 / k1 is greater than 1.2, open solenoid valve C for air purge for 30 seconds.

6. The method for online pressure monitoring and automatic purging of induced draft fans in thermal power plants according to claim 5, characterized in that: When the flue gas pipeline is normal, the system flow Q under two different working conditions displayed on the monitoring dial and the pressure P obtained by the test are used to calculate k1 and A1 in the formula P=k1Q+A1.

7. The method for online pressure monitoring and automatic purging of induced draft fans in thermal power plants according to claim 6, characterized in that: After the system has been running for a period of time, k and A gradually change. When the system resistance increases, the k value gradually increases.

8. The method for online pressure monitoring and automatic purging of induced draft fans in thermal power plants according to claim 6, characterized in that: By monitoring the system flow Q under two different working conditions displayed on the dial and the pressure P obtained by the test, k2 and A2 in the formula P=k2Q+A2 are calculated.

9. The method for online pressure monitoring and automatic purging of induced draft fans in thermal power plants according to claim 4, characterized in that: The flue gas temperature t2 in the heating pipe is tested using a thermocouple.

10. The method for online pressure monitoring and automatic purging of induced draft fans in thermal power plants according to claim 4, characterized in that: Use a pressure gauge to test the flue gas pressure in the heating pipe.

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