Method and system for controlling over-fire air door of coal-fired boiler

Abstract

The invention discloses a coal-fired boiler over-fire air door control method and system, comprehensive parameters such as unit load, boiler total secondary air volume, air door opening degree of each layer, NOx concentration, steam temperature, oxygen amount, coal amount and the like are obtained from a unit DCS or SIS system, over-fire air multi-target comprehensive control is achieved, key parameters such as NOx emission, steam temperature, oxygen amount distribution and the like are taken into consideration in the mode, and the control method and system have the advantages of being simple in structure and convenient to operate. The overall combustion performance of the boiler is improved, nonlinear modeling is adopted, the function relation between the openness of the over-fire air doors and multiple parameters is established, differential control over all the over-fire air doors can be achieved according to the actual operation condition of the boiler, accurate air distribution and combustion adjustment are achieved, an initial control instruction is dynamically corrected through PID operation, and a final control instruction is obtained. The over-fire air door can be adjusted according to the real-time condition of the boiler, the optimal combustion performance under all working conditions is ensured, accurate control over the overall combustion performance of the boiler is comprehensively considered, the content of combustible matter in fly ash and incomplete combustion loss are effectively reduced, steam temperature and oxygen distribution is optimized, and heat efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of burnout damper control technology, and in particular to a method and system for controlling burnout dampers in coal-fired boilers. Background Technology

[0002] During the operation of coal-fired boilers, the control of burnout air plays a crucial role in optimizing combustion performance, reducing pollutant emissions, and improving the unit's economy. Currently, most boilers still rely on manual operation by operators or simple load function control for burnout air control. Although some boilers have incorporated burnout air into the furnace wind box differential pressure control, the control method is relatively simple and fails to fully consider the uniformity of NOx concentration and combustion distribution. This single-objective control method often only optimizes NOx emissions while neglecting the improvement of the overall combustion performance of the boiler, such as the balance of key parameters like steam temperature distribution and oxygen distribution. Summary of the Invention

[0003] In view of this, the present invention proposes a method and system for controlling the burnout damper of a coal-fired boiler, which can effectively solve the defects of the existing technology, such as relatively simple control methods and neglect of the overall combustion performance improvement of the boiler.

[0004] The technical solution of this invention is implemented as follows: A method for controlling the burnout damper of a coal-fired boiler, specifically including: The unit parameters are obtained from the DCS or SIS system of the unit. The unit parameters include the unit load, the total secondary air volume of the boiler, the opening of the perimeter damper of each burner, the opening of the auxiliary damper above and below the burner, the opening of the burnout damper, the NOx concentration at the inlet of the SCR denitrification unit, the main steam temperature on both sides of the boiler, the reheat steam temperature on both sides of the boiler, the oxygen content at the air preheater inlet, and the coal content of each burner. Based on the boiler design drawings, obtain the area of ​​the peripheral air nozzle of each burner, the area of ​​the auxiliary air nozzle of each layer, and the area of ​​each burnout air nozzle. The burnout air ratio is calculated based on the total secondary air volume of the boiler, the opening of the perimeter damper of each burner, the opening of the auxiliary damper above and below the burner, the opening of the burnout damper, the perimeter air nozzle area of ​​each burner, the auxiliary air nozzle area of ​​each layer, and the burnout air nozzle area. Calculate the ratio of the main steam temperatures on both sides of the boiler based on the main steam temperatures on both sides of the boiler; Calculate the ratio of reheat steam temperatures on both sides of the boiler based on the reheat steam temperatures on both sides of the boiler. Calculate the oxygen ratio on both sides of the boiler based on the oxygen content at the air preheater inlet; Calculate the height of the combustion center based on the coal quantity in each burner layer; Using unit load, total secondary air volume of boiler, NOx concentration at the inlet of denitrification system, burnout air ratio, main steam temperature ratio, reheat steam temperature ratio, oxygen ratio, and combustion center height as independent variables and burnout damper opening as dependent variable, nonlinear modeling was performed to obtain the functional relationship between burnout damper opening and each parameter. Based on the modeling results and the desired NOx concentration control target value, the initial control command for each burnout damper is calculated. The initial control command is corrected by PID calculation to obtain the final control command for each burnout damper; The burnout dampers are controlled according to the final control commands of each burnout damper.

[0005] As a further optional scheme of the aforementioned coal-fired boiler burnout damper control method, the calculation of the burnout air ratio based on the total secondary air volume of the boiler, the opening degree of the perimeter dampers of each burner layer, the opening degree of the auxiliary dampers above and below the burners, the opening degree of the burnout damper, the perimeter air nozzle area of ​​each burner, the area of ​​each auxiliary air nozzle layer, and the area of ​​each burnout air nozzle specifically includes: Based on the total secondary air volume of the boiler, the opening of the perimeter damper of each burner, the opening of the auxiliary damper above and below the burner, the opening of the burnout damper, the perimeter air nozzle area of ​​each burner, the auxiliary air nozzle area of ​​each layer, and the burnout air nozzle area, calculate the air volume corresponding to each burnout damper. Calculate the burnout air ratio based on the air volume corresponding to each burnout damper and the total secondary air volume of the boiler.

[0006] As a further optional solution to the aforementioned coal-fired boiler burnout damper control method, the specific calculation formula for calculating the air volume corresponding to each burnout damper is as follows: ; Where Q2sk is the air volume of the kth burnout air, Ask is the area of ​​each burnout air nozzle, Psk is the opening degree of the burnout air damper, Ar is the area of ​​the peripheral air nozzle of each burner in the boiler, Pri is the opening degree of the peripheral air damper of each layer of burners, Afj is the area of ​​each auxiliary air nozzle, Pfj is the opening degree of the auxiliary air damper above and below the burner, and n is the damper characteristic index. The specific formula for calculating the burnout air ratio is as follows: ; in, Q1 represents the burnout air ratio, and Q2 represents the total secondary air volume of the boiler.

[0007] As a further optional scheme of the aforementioned coal-fired boiler burnout damper control method, the specific calculation formula for the ratio of main steam temperatures on both sides of the boiler is as follows: ; in, The main steam temperature ratio is TsA and TsB, which represent the main steam temperatures on both sides of the boiler.

[0008] As a further optional scheme of the aforementioned coal-fired boiler burnout damper control method, the specific calculation formula for the ratio of reheat steam temperatures on both sides of the boiler is as follows: ; in, TrA and TrB represent the reheat steam temperature ratios, and the reheat steam temperatures on both sides of the boiler.

[0009] As a further optional solution to the aforementioned coal-fired boiler burnout damper control method, the specific calculation formula for the oxygen ratio on both sides of the boiler is as follows: ; in, O2Al and O2Bl represent the oxygen content at the air preheater inlet, while AL and BL represent the number of oxygen measurement points on both sides of the boiler.

[0010] As a further optional solution to the aforementioned coal-fired boiler burnout damper control method, the specific calculation formula for calculating the combustion center height is as follows: ; Where H is the height of the combustion center, Hi is the elevation of each burner layer, and Gi is the amount of coal in each burner layer.

[0011] As a further optional scheme of the aforementioned coal-fired boiler burnout damper control method, the functional relationship between the burnout damper opening and various parameters is specifically as follows: ; Where ki is the modeling coefficient, ni is the modeling exponent, Xi is the modeling independent variable, and B is the modeling constant term.

[0012] As a further optional scheme of the coal-fired boiler burnout damper control method, the specific calculation formula for calculating the initial control command of each burnout damper is as follows: ; Where Psk-sp0 is the initial control command for each burnout damper, and Xisp is the expected value of each modeling independent variable.

[0013] A coal-fired boiler burnout damper control system includes: The data acquisition module is used to obtain unit parameters from the unit's DCS system or SIS system. The unit parameters include unit load, total secondary air volume of boiler, perimeter damper opening of each burner layer, auxiliary damper opening above and below the burner, burnout damper opening, NOx concentration at the inlet of SCR denitrification unit, main steam temperature on both sides of boiler, reheat steam temperature on both sides of boiler, oxygen content at the air preheater inlet, and coal quantity of each burner layer. The boiler design parameter acquisition module is used to obtain the area of ​​the peripheral air nozzles of each burner, the area of ​​the auxiliary air nozzles of each layer, and the area of ​​each burnout air nozzle based on the boiler design drawings. The burnout air ratio calculation module is used to calculate the burnout air ratio based on the total secondary air volume of the boiler, the opening of the perimeter damper of each layer of burners, the opening of the auxiliary damper above and below the burners, the opening of the burnout damper, the perimeter air nozzle area of ​​each burner of the boiler, the area of ​​each layer of auxiliary air nozzle, and the area of ​​each burnout air nozzle. The main steam temperature ratio calculation module is used to calculate the ratio of the main steam temperatures on both sides of the boiler based on the main steam temperatures on both sides of the boiler. The reheat steam temperature ratio calculation module is used to calculate the reheat steam temperature ratio on both sides of the boiler based on the reheat steam temperatures on both sides of the boiler. The oxygen ratio calculation module is used to calculate the oxygen ratio on both sides of the boiler based on the oxygen content at the air preheater inlet. The combustion center height calculation module is used to calculate the combustion center height based on the coal quantity of each burner layer. The modeling module is used to perform nonlinear modeling with unit load, total secondary air volume of boiler, NOx concentration at the inlet of denitrification system, burnout air ratio, main steam temperature ratio, reheat steam temperature ratio, oxygen ratio, and combustion center height as independent variables and burnout damper opening as dependent variable, so as to obtain the functional relationship between burnout damper opening and each parameter. The control command calculation module is used to calculate the initial control command of each burnout damper based on the modeling results and the expected NOx concentration control target value. The initial control command is corrected through PID calculation to obtain the final control command of each burnout damper. The burnout damper control module is used to control the burnout dampers according to the final control commands of each burnout damper.

[0014] The beneficial effects of this invention are as follows: By acquiring comprehensive unit parameters from the unit's DCS or SIS system, including unit load, total secondary air volume of the boiler, perimeter damper opening of each burner layer, auxiliary damper opening above and below the burner, burnout damper opening, NOx concentration at the inlet of the SCR denitrification unit, main steam temperature on both sides of the boiler, reheat steam temperature on both sides of the boiler, oxygen content at the air preheater inlet, and coal quantity at each burner layer, multi-objective comprehensive control of burnout air is achieved. This control method not only focuses on NOx emissions but also comprehensively considers key parameters such as steam temperature distribution and oxygen distribution, thereby improving the overall combustion performance of the boiler. Simultaneously, through nonlinear modeling, a relationship is established between burnout damper opening and unit load, total secondary air volume of the boiler, NOx concentration at the denitrification system inlet, burnout air ratio, main steam temperature ratio, and reheat steam temperature. Based on the functional relationships of multiple parameters such as temperature ratio, oxygen ratio, and combustion center height, this model allows for differentiated control of each burnout damper according to the actual operating conditions of the boiler. This enables more precise airflow distribution and combustion adjustment. Furthermore, through PID calculations, the initial control commands are dynamically corrected to obtain the final control commands for each burnout damper. This mechanism allows the burnout dampers to dynamically adjust according to the real-time operating conditions of the boiler, ensuring that the boiler maintains optimal combustion performance under various operating conditions. In addition, by comprehensively considering the overall combustion performance of the boiler, precise control of the burnout air is achieved, effectively reducing the combustible content in fly ash and incomplete combustion losses. At the same time, by optimizing the steam temperature and oxygen distribution, the boiler's thermal efficiency is improved, further enhancing the boiler's economic efficiency. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart illustrating a method for controlling the burnout damper of a coal-fired boiler according to the present invention. Figure 2 This is a schematic diagram of the composition of a coal-fired boiler burnout damper control system according to the present invention. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] refer to Figures 1 to 2 A method for controlling the burnout damper of a coal-fired boiler, specifically including: The unit parameters are obtained from the DCS or SIS system of the unit. The unit parameters include the unit load, the total secondary air volume of the boiler, the opening of the perimeter damper of each burner, the opening of the auxiliary damper above and below the burner, the opening of the burnout damper, the NOx concentration at the inlet of the SCR denitrification unit, the main steam temperature on both sides of the boiler, the reheat steam temperature on both sides of the boiler, the oxygen content at the air preheater inlet, and the coal content of each burner. Based on the boiler design drawings, obtain the area of ​​the peripheral air nozzle of each burner, the area of ​​the auxiliary air nozzle of each layer, and the area of ​​each burnout air nozzle. The burnout air ratio is calculated based on the total secondary air volume of the boiler, the opening of the perimeter damper of each burner, the opening of the auxiliary damper above and below the burner, the opening of the burnout damper, the perimeter air nozzle area of ​​each burner, the auxiliary air nozzle area of ​​each layer, and the burnout air nozzle area. Calculate the ratio of the main steam temperatures on both sides of the boiler based on the main steam temperatures on both sides of the boiler; Calculate the ratio of reheat steam temperatures on both sides of the boiler based on the reheat steam temperatures on both sides of the boiler. Calculate the oxygen ratio on both sides of the boiler based on the oxygen content at the air preheater inlet; Calculate the height of the combustion center based on the coal quantity in each burner layer; Using unit load, total secondary air volume of boiler, NOx concentration at the inlet of denitrification system, burnout air ratio, main steam temperature ratio, reheat steam temperature ratio, oxygen ratio, and combustion center height as independent variables and burnout damper opening as dependent variable, nonlinear modeling was performed to obtain the functional relationship between burnout damper opening and each parameter. Based on the modeling results and the desired NOx concentration control target value, the initial control command for each burnout damper is calculated. The initial control command is corrected by PID calculation to obtain the final control command for each burnout damper; The burnout dampers are controlled according to the final control commands of each burnout damper.

[0019] In this embodiment, comprehensive unit parameters are obtained from the unit's DCS or SIS system, including unit load, total secondary air volume of the boiler, perimeter damper opening of each burner layer, auxiliary damper opening above and below the burner, burnout damper opening, NOx concentration at the SCR denitrification unit inlet, main steam temperature on both sides of the boiler, reheat steam temperature on both sides of the boiler, oxygen content at the air preheater inlet, and coal quantity at each burner layer. This enables multi-objective integrated control of the burnout air. This control method not only focuses on NOx emissions but also comprehensively considers key parameters such as steam temperature distribution and oxygen distribution, thereby improving the overall combustion performance of the boiler. Furthermore, through nonlinear modeling, a relationship is established between the burnout damper opening and unit load, total secondary air volume of the boiler, NOx concentration at the denitrification system inlet, burnout air ratio, main steam temperature ratio, and reheat steam temperature. Based on the functional relationships of multiple parameters such as proportion, oxygen proportion, and combustion center height, this model allows for differentiated control of each burnout damper according to the actual operating conditions of the boiler, achieving more precise airflow distribution and combustion adjustment. Furthermore, through PID calculations, the initial control commands are dynamically corrected to obtain the final control commands for each burnout damper. This mechanism enables the burnout dampers to dynamically adjust according to the real-time operating conditions of the boiler, ensuring optimal combustion performance under various operating conditions. In addition, by comprehensively considering the overall combustion performance of the boiler, precise control of the burnout air is achieved, effectively reducing the combustible content in fly ash and incomplete combustion losses. Simultaneously, by optimizing steam temperature and oxygen distribution, the boiler's thermal efficiency is improved, further enhancing its economic efficiency.

[0020] Preferably, the calculation of the burnout air ratio based on the total secondary air volume of the boiler, the opening of the perimeter dampers of each burner layer, the opening of the auxiliary dampers above and below the burners, the opening of the burnout dampers, the perimeter air nozzle area of ​​each burner, the area of ​​each auxiliary air nozzle, and the area of ​​each burnout air nozzle specifically includes: Based on the total secondary air volume of the boiler, the opening of the perimeter damper of each burner, the opening of the auxiliary damper above and below the burner, the opening of the burnout damper, the perimeter air nozzle area of ​​each burner, the auxiliary air nozzle area of ​​each layer, and the burnout air nozzle area, calculate the air volume corresponding to each burnout damper. Calculate the burnout air ratio based on the air volume corresponding to each burnout damper and the total secondary air volume of the boiler.

[0021] In this embodiment, by comprehensively considering the total secondary air volume of the boiler, the opening of the perimeter dampers of each burner layer, the opening of the auxiliary dampers above and below the burners, the opening of the burnout dampers, and the area of ​​each nozzle, the air volume corresponding to each burnout damper can be accurately calculated. This precise air volume calculation provides a solid foundation for the subsequent burnout air ratio calculation, ensuring the accuracy of burnout air control. Calculating the burnout air ratio based on the air volume corresponding to each burnout damper and the total secondary air volume of the boiler makes the distribution of burnout air more reasonable. This reasonable distribution method helps optimize the boiler's combustion process, improve combustion efficiency, and reduce... Incomplete combustion losses and pollutant emissions; since the burnout air ratio is calculated based on real-time parameters such as the total secondary air volume of the boiler and the opening degree of each damper, this technical solution can automatically adapt to changes in boiler load. When the boiler load increases or decreases, the burnout air ratio will be adjusted accordingly to maintain optimal combustion performance and emission levels. By accurately calculating the burnout air ratio and accordingly controlling the burnout dampers, the overall combustion performance of the boiler can be significantly improved. This includes optimizing steam temperature distribution, reducing fly ash combustible content, and improving thermal efficiency, thereby further enhancing the boiler's economy and environmental friendliness.

[0022] Preferably, the specific formula for calculating the air volume corresponding to each burnout damper is as follows: ; Where Q2sk is the air volume of the kth burnout air, Ask is the area of ​​each burnout air nozzle, Psk is the opening degree of the burnout air damper, Ar is the area of ​​the peripheral air nozzle of each burner in the boiler, Pri is the opening degree of the peripheral air damper of each layer of burners, Afj is the area of ​​each auxiliary air nozzle, Pfj is the opening degree of the auxiliary air damper above and below the burner, and n is the damper characteristic index. The specific formula for calculating the burnout air ratio is as follows: ; in, Q1 represents the burnout air ratio, and Q2 represents the total secondary air volume of the boiler.

[0023] In this embodiment, the formula for calculating the air volume of the burnout damper comprehensively considers multiple key parameters, including the burnout air nozzle area Ask, the burnout damper opening Psk, the perimeter air nozzle area Ar of each burner in the boiler, the perimeter damper opening Pri of each layer of burners, the auxiliary air nozzle area Afj of each layer, and the auxiliary damper opening Pfj above and below the burner. This ensures that the air volume calculation for each burnout damper fully considers the overall air volume distribution of the boiler and the operating status of the burners, thereby achieving precise air volume distribution and meeting the combustion needs of different areas where burnout dampers are located. For example, the burnout dampers in different locations may differ due to factors such as burner combustion conditions and furnace temperature distribution. Depending on the required airflow, this formula can calculate the optimal airflow for each burnout damper based on the actual conditions of each parameter, avoiding problems such as incomplete combustion or localized overheating caused by uneven airflow distribution. During actual boiler operation, the load constantly changes, and the burner's operating status also adjusts. Because this formula incorporates multiple combustion-related parameters, it can adapt to these complex and variable operating conditions. When the boiler load increases or decreases, each parameter changes accordingly, and the formula can accurately and promptly calculate the new burnout damper airflow, ensuring efficient and stable combustion under different operating conditions. Precise airflow supply helps the fuel burn completely in the furnace. The reasonable airflow calculated by this formula ensures thorough mixing of burnout air and unburned fuel, promoting complete combustion and reducing incomplete combustion losses, such as carbon monoxide (CO) and unburned carbon, thereby improving boiler thermal efficiency and reducing fuel consumption.

[0024] The formula for calculating the burnout air ratio links the sum of the air volume of each burnout damper to the total secondary air volume of the boiler, enabling precise calculation of the proportion of burnout air in the total secondary air volume. This helps to coordinate the distribution relationship between burnout air and other secondary air, ensuring the coordinated operation of the boiler's secondary air system. By accurately calculating the burnout air ratio, the supply of burnout air can be adjusted to better match the air volume of the main combustion zone. This helps to control the combustion temperature and flame shape, reduce the generation of pollutants such as nitrogen oxides (NOx), and ensure complete combustion of fuel, thereby improving the environmental and economic performance of the boiler.

[0025] It should be noted that F represents the upper limit of the summation of the perimeter damper opening Pri of each burner in the boiler. It indicates the range of the number of burner layers involved in the calculation of the contribution of the peripheral wind volume of each burner in the boiler. For example, if the boiler has multiple burner layers, F determines the maximum number of the burner layer corresponding to the perimeter damper opening that participates in the summation calculation. J represents the upper limit of the summation of the product of the area Afj of each auxiliary air nozzle and the corresponding opening Pfj of the auxiliary air damper. It reflects the number of auxiliary air layers considered when calculating the impact of each auxiliary air layer on the total air volume. For example, a boiler may have auxiliary air layers in different locations. J determines the number of auxiliary air layers participating in the summation calculation. K is the upper limit related to burnout air in the summation term, and is used in the formula to determine the number of burnout air dampers that contribute to the calculation of burnout air volume.

[0026] Preferably, the specific formula for calculating the ratio of main steam temperatures on both sides of the boiler is as follows: ; in, The main steam temperature ratio is TsA and TsB, which represent the main steam temperatures on both sides of the boiler.

[0027] In this embodiment, the ratio of the main steam temperatures TsA and TsB on both sides of the boiler is calculated. This can intuitively reflect the relative difference in the main steam temperature on both sides. When the value is close to 1, it indicates that the main steam temperatures on both sides are relatively close, while when... A significant deviation of 1 indicates a substantial difference in the main steam temperature between the two sides. This helps operators quickly understand the temperature balance on both sides of the boiler. Differences in the main steam temperature between the two sides are often related to uneven combustion distribution. Monitoring... This allows for the assessment of whether combustion is uniform across the burner area. For example, if the main steam temperature on one side is significantly higher than on the other, it may indicate that the burner on that side is firing too hard or the airflow distribution is unreasonable. Operators can use this information to adjust parameters such as airflow and coal volume to optimize combustion distribution and bring the main steam temperatures on both sides closer to equilibrium. A uniform combustion distribution helps improve the overall combustion efficiency of the boiler. When the main steam temperatures on both sides are balanced, the heat distribution within the boiler is more uniform, reducing localized overheating or undercooling, thereby improving fuel utilization and reducing energy consumption. Excessive differences in main steam temperatures on both sides may lead to excessive localized thermal stress on the boiler's heating surfaces, increasing the risk of equipment damage. Real-time calculation and monitoring can help address this issue. This allows for the timely detection of potential safety hazards and the implementation of corresponding adjustments, preventing equipment failures caused by steam temperature imbalances and extending the boiler's service life. Stable steam temperature is a crucial guarantee for the safe operation of a boiler. Calculation and application help maintain stable steam temperatures on both sides of the boiler, ensuring that the boiler operates under safe conditions and reducing operational accidents caused by steam temperature fluctuations.

[0028] Preferably, the specific formula for calculating the ratio of reheat steam temperatures on both sides of the boiler is as follows: ; in, TrA and TrB represent the reheat steam temperature ratios, and the reheat steam temperatures on both sides of the boiler.

[0029] In this embodiment, the reheat steam temperature ratio is calculated. This clearly shows the relative relationship between the reheat steam temperatures TrA and TrB on both sides of the boiler. When the value is close to 1, it indicates that the reheat steam temperatures on both sides are basically equal, while when... A significant deviation of 1 indicates a substantial difference in reheat steam temperatures on both sides. This intuitive reflection helps operators quickly understand the thermal balance of the boiler's reheat systems. The reheat steam temperature ratio is closely related to the boiler's combustion. For example, if one side's reheat steam temperature is too high, it may be due to excessive burner power, insufficient airflow, or slagging on localized heating surfaces. Operators can adjust the burner's airflow and coal distribution, or perform soot blowing, to optimize the combustion process, restore the reheat steam temperatures on both sides to a balanced state, and improve the boiler's combustion efficiency. Uniform reheat steam temperature helps ensure steam quality. When the reheat steam temperatures on both sides are unbalanced, it may lead to inconsistent superheat, affecting the steam's work capacity and the safe operation of the equipment. Combustion adjustments can improve steam quality and enhance the unit's economy and reliability. Excessive differences in reheat steam temperature between the two sides may cause significant thermal stress on the boiler's heating surfaces, increasing the risk of fatigue damage and rupture in the heating surface tubes. Real-time monitoring and timely adjustment of the reheat steam temperature deviation between the two sides can effectively prevent equipment damage caused by excessive thermal stress and extend the service life of the boiler's heating surfaces.

[0030] Preferably, the specific formula for calculating the oxygen ratio on both sides of the boiler is as follows: ; in, O2Al and O2Bl represent the oxygen content at the air preheater inlet, while AL and BL represent the number of oxygen measurement points on both sides of the boiler.

[0031] In this embodiment, by summing and averaging the oxygen content (O2Al and O2Bl) at the air preheater inlet at different measuring points on both sides of the boiler (AL and BL represent the number of oxygen measuring points on both sides, respectively), the overall oxygen level on both sides of the boiler can be comprehensively and holistically reflected. This calculation method avoids the errors and limitations that may exist with data from a single measuring point, and more accurately represents the actual distribution of oxygen on both sides of the boiler. The calculated oxygen ratio It can clearly quantify the degree of difference in oxygen levels on both sides of the boiler, when When the value is close to 1, it indicates that the oxygen levels on both sides are relatively similar, while when... A significant deviation from 1 indicates a clear imbalance in oxygen levels on both sides, providing a clear basis for subsequent adjustments and control. Oxygen level is a crucial indicator of boiler combustion; an imbalance in the oxygen ratio on both sides often signifies an unreasonable airflow distribution during combustion. Operators can adjust their settings accordingly. By adjusting the oxygen content on both sides of the boiler, the output of the forced draft fan and induced draft fan can be controlled, or the damper opening of each burner layer can be adjusted to achieve a balance in oxygen levels. This optimizes the combustion process, improves combustion efficiency, and reduces incomplete combustion losses. A reasonable oxygen distribution helps reduce the generation of pollutants during boiler combustion. For example, by adjusting the oxygen ratio, localized oxygen deficiency or excess can be avoided, reducing emissions of pollutants such as nitrogen oxides (NOx) and carbon monoxide (CO), thus meeting environmental protection requirements. An imbalance in oxygen levels on both sides may lead to excessively high or low temperatures on the boiler's heating surfaces, increasing thermal stress on the equipment and affecting its service life and safety. Real-time monitoring and adjustment of the oxygen ratio are crucial for achieving this balance. It can promptly detect and correct uneven oxygen distribution, and prevent equipment failures caused by excessive thermal stress, such as damage to the heated surface pipes.

[0032] Preferably, the specific formula for calculating the combustion center height is as follows: ; Where H is the height of the combustion center, Hi is the elevation of each burner layer, and Gi is the amount of coal in each burner layer.

[0033] In this embodiment, by weighted summing of the elevation Hi of each burner layer and its corresponding coal quantity Gi, and then dividing by the total coal quantity, the height position of the burners and the fuel distribution are comprehensively considered. This method can more accurately reflect the actual combustion center position during combustion, avoiding errors caused by considering only a single factor such as burner position or fuel distribution. In actual boiler operation, the coal quantity of burners in different layers may be adjusted according to factors such as load and coal quality. This formula can dynamically calculate the height of the combustion center in real time based on the changes in the coal quantity of each burner layer, adapting to complex and changing combustion conditions and providing operators with accurate combustion center position information; combustion Determining the center height is crucial for proper air distribution. Operators can adjust the airflow distribution of each burner layer based on the calculated combustion center height, ensuring thorough mixing of air and fuel near the combustion center, improving combustion efficiency, and reducing incomplete combustion losses. For example, if the combustion center is too high, the airflow to the lower burners can be increased to make combustion more uniform. By monitoring changes in the combustion center height, operators can also adjust the coal distribution to each burner layer in a timely manner. When the combustion center deviates from the ideal position, the coal quantity to certain burners can be increased or decreased accordingly to restore the combustion center to a suitable height, thereby optimizing the combustion process and improving the boiler's thermal efficiency.

[0034] It should be noted that F usually represents an upper limit identifier for the number of boiler burner layers, indicating the number of the highest burner layer involved in the calculation of the combustion center height. For example, if the boiler has burners numbered 1-5 from bottom to top, F may be 5, meaning that the relevant parameters of burners from layer A to layer 5 will be considered during the calculation. A: Represents a lower limit identifier for the number of boiler burner layers, indicating the lowest burner number involved in the calculation of the combustion center height. Continuing with the example above, A could be 1, meaning that the elevation and coal quantity data of burners from layer 1 up to layer F will be used in the calculation of this formula.

[0035] Preferably, the functional relationship between the burnout damper opening and each parameter is as follows: ; Where ki is the modeling coefficient, ni is the modeling exponent, Xi is the modeling independent variable, and B is the modeling constant term.

[0036] In this embodiment, the formula considers multiple modeling independent variables Xi, which may cover various key factors affecting the burnout damper opening, such as boiler load, fuel characteristics, and burner operating parameters. By comprehensively considering these factors, the appropriate burnout damper opening Psk can be calculated more accurately, achieving precise control of the burnout damper and meeting the boiler combustion needs under different operating conditions. Different modeling coefficients ki, modeling exponents ni, and modeling constants B can be determined according to specific boiler characteristics and operating conditions. This means that the functional relationship can be individually adjusted for different types of boilers and different operating states, improving the accuracy and adaptability of burnout damper opening control. Precise control of the burnout damper opening helps optimize air distribution within the boiler, allowing fuel to mix fully with air during combustion and improving combustion efficiency. A reasonable burnout air supply can reduce the generation of incomplete combustion products, such as carbon monoxide (CO) and unburned carbon, thereby reducing fuel consumption and improving boiler thermal efficiency. Appropriate burnout damper opening can control combustion temperature and flame shape, reducing the generation of pollutants such as nitrogen oxides (NOx). Precise control of the burnout damper through this functional relationship allows the boiler to meet environmental emission requirements while maintaining combustion efficiency. This functional relationship can serve as part of the boiler's automated control system, providing a mathematical model for the automatic adjustment of the burnout damper. The control system can automatically calculate the appropriate burnout damper opening Psk based on the real-time monitored modeling variable Xi, and control the actuator to adjust it, achieving automated control of the burnout damper, reducing manual intervention, and improving control efficiency and accuracy.

[0037] It should be noted that I represents the upper limit of the summation, that is, the number of independent variables Xi involved in constructing the calculation model of the burnout damper opening Psk.

[0038] Preferably, the specific calculation formula for calculating the initial control command of each burnout damper is as follows: ; Where Psk-sp0 is the initial control command for each burnout damper, and Xisp is the expected value of each modeling independent variable.

[0039] In this embodiment, the formula considers multiple modeling independent variables Xisp and their corresponding modeling coefficients ki and ni, as well as a modeling constant term B. These independent variables may cover various key factors affecting the control of the burnout damper, such as boiler load, burner operating status, and flue gas composition. By comprehensively considering these factors, the initial control command Psk−spO for each burnout damper can be calculated more accurately, making the initial setting of the burnout damper more in line with actual combustion requirements. Under different boilers or different operating conditions, the modeling coefficients ki, modeling exponents ni, and modeling constant term B can be adjusted accordingly. This means that the formula can be personalized according to specific equipment and operating conditions, improving the initial control... This formula ensures the accuracy and applicability of control commands, avoiding unreasonable adjustments caused by uniform control commands. It can serve as part of the boiler's automated control system, providing a mathematical model for the initial control of the burnout damper. The control system can automatically calculate the initial control command based on the expected value of the modeling independent variable Xisp, which is monitored in real time. This enables intelligent initialization control of the burnout damper, reducing manual intervention and improving control efficiency and accuracy. By analyzing and processing a large amount of operating data, the modeling coefficients ki, modeling exponent ni, and modeling constant term B can be continuously optimized, making the formula more consistent with the actual operating conditions of the boiler and further improving the calculation accuracy of the initial control command and the overall automation control level of the boiler.

[0040] It should be noted that the initial control commands are modified to obtain the final control commands for each burnout damper. The specific formula is as follows: Psk = Psk - sp0 ± DPsk; The value of ±DPsk is determined based on the steam temperature ratio. Reheat steam temperature ratio Oxygen ratio The modeling coefficient ki and the weight coefficient of these three parameters are determined by multiplying them.

[0041] A coal-fired boiler burnout damper control system includes: The data acquisition module is used to obtain unit parameters from the unit's DCS system or SIS system. The unit parameters include unit load, total secondary air volume of boiler, perimeter damper opening of each burner layer, auxiliary damper opening above and below the burner, burnout damper opening, NOx concentration at the inlet of SCR denitrification unit, main steam temperature on both sides of boiler, reheat steam temperature on both sides of boiler, oxygen content at the air preheater inlet, and coal quantity of each burner layer. The boiler design parameter acquisition module is used to obtain the area of ​​the peripheral air nozzles of each burner, the area of ​​the auxiliary air nozzles of each layer, and the area of ​​each burnout air nozzle based on the boiler design drawings. The burnout air ratio calculation module is used to calculate the burnout air ratio based on the total secondary air volume of the boiler, the opening of the perimeter damper of each layer of burners, the opening of the auxiliary damper above and below the burners, the opening of the burnout damper, the perimeter air nozzle area of ​​each burner of the boiler, the area of ​​each layer of auxiliary air nozzle, and the area of ​​each burnout air nozzle. The main steam temperature ratio calculation module is used to calculate the ratio of the main steam temperatures on both sides of the boiler based on the main steam temperatures on both sides of the boiler. The reheat steam temperature ratio calculation module is used to calculate the reheat steam temperature ratio on both sides of the boiler based on the reheat steam temperatures on both sides of the boiler. The oxygen ratio calculation module is used to calculate the oxygen ratio on both sides of the boiler based on the oxygen content at the air preheater inlet. The combustion center height calculation module is used to calculate the combustion center height based on the coal quantity of each burner layer. The modeling module is used to perform nonlinear modeling with unit load, total secondary air volume of boiler, NOx concentration at the inlet of denitrification system, burnout air ratio, main steam temperature ratio, reheat steam temperature ratio, oxygen ratio, and combustion center height as independent variables and burnout damper opening as dependent variable, so as to obtain the functional relationship between burnout damper opening and each parameter. The control command calculation module is used to calculate the initial control command of each burnout damper based on the modeling results and the expected NOx concentration control target value. The initial control command is corrected through PID calculation to obtain the final control command of each burnout damper. The burnout damper control module is used to control the burnout dampers according to the final control commands of each burnout damper.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling the burnout damper of a coal-fired boiler, characterized in that, Specifically include: The unit parameters are obtained from the DCS or SIS system of the unit. The unit parameters include the unit load, the total secondary air volume of the boiler, the opening of the perimeter damper of each burner, the opening of the auxiliary damper above and below the burner, the opening of the burnout damper, the NOx concentration at the inlet of the SCR denitrification unit, the main steam temperature on both sides of the boiler, the reheat steam temperature on both sides of the boiler, the oxygen content at the air preheater inlet, and the coal content of each burner. Based on the boiler design drawings, obtain the area of ​​the peripheral air nozzle of each burner, the area of ​​the auxiliary air nozzle of each layer, and the area of ​​each burnout air nozzle. The burnout air ratio is calculated based on the total secondary air volume of the boiler, the opening of the perimeter damper of each burner, the opening of the auxiliary damper above and below the burner, the opening of the burnout damper, the perimeter air nozzle area of ​​each burner, the auxiliary air nozzle area of ​​each layer, and the burnout air nozzle area. Calculate the ratio of the main steam temperatures on both sides of the boiler based on the main steam temperatures on both sides of the boiler; Calculate the ratio of reheat steam temperatures on both sides of the boiler based on the reheat steam temperatures on both sides of the boiler. Calculate the oxygen ratio on both sides of the boiler based on the oxygen content at the air preheater inlet; Calculate the height of the combustion center based on the coal quantity in each burner layer; Using unit load, total secondary air volume of boiler, NOx concentration at the inlet of denitrification system, burnout air ratio, main steam temperature ratio, reheat steam temperature ratio, oxygen ratio, and combustion center height as independent variables and burnout damper opening as dependent variable, nonlinear modeling was performed to obtain the functional relationship between burnout damper opening and each parameter. Based on the modeling results and the desired NOx concentration control target value, the initial control command for each burnout damper is calculated. The initial control command is corrected by PID calculation to obtain the final control command for each burnout damper; The burnout dampers are controlled according to the final control commands of each burnout damper.

2. The method for controlling the burnout damper of a coal-fired boiler according to claim 1, characterized in that, The calculation of the burnout air ratio is based on the total secondary air volume of the boiler, the opening of the perimeter dampers of each burner, the opening of the auxiliary dampers above and below the burners, the opening of the burnout dampers, the perimeter air nozzle area of ​​each burner, the area of ​​each auxiliary air nozzle, and the area of ​​each burnout air nozzle. Specifically, this includes: Based on the total secondary air volume of the boiler, the opening of the perimeter damper of each burner, the opening of the auxiliary damper above and below the burner, the opening of the burnout damper, the perimeter air nozzle area of ​​each burner, the auxiliary air nozzle area of ​​each layer, and the burnout air nozzle area, calculate the air volume corresponding to each burnout damper. Calculate the burnout air ratio based on the air volume corresponding to each burnout damper and the total secondary air volume of the boiler.

3. The method for controlling the burnout damper of a coal-fired boiler according to claim 2, characterized in that, The specific formula for calculating the air volume corresponding to each burnout damper is as follows: ； Where Q2sk is the air volume of the kth burnout air, Ask is the area of ​​each burnout air nozzle, Psk is the opening degree of the burnout air damper, Ar is the area of ​​the peripheral air nozzle of each burner in the boiler, Pri is the opening degree of the peripheral air damper of each layer of burners, Afj is the area of ​​each auxiliary air nozzle, Pfj is the opening degree of the auxiliary air damper above and below the burner, and n is the damper characteristic index. The specific formula for calculating the burnout air ratio is as follows: ； in, Q1 represents the burnout air ratio, and Q2 represents the total secondary air volume of the boiler.

4. The method for controlling the burnout damper of a coal-fired boiler according to claim 3, characterized in that, The specific formula for calculating the ratio of main steam temperatures on both sides of the boiler is as follows: ； in, The main steam temperature ratio is TsA and TsB, which represent the main steam temperatures on both sides of the boiler.

5. The method for controlling the burnout damper of a coal-fired boiler according to claim 4, characterized in that, The specific formula for calculating the ratio of reheat steam temperatures on both sides of the boiler is as follows: ； Wherein, is the reheat steam temperature ratio, and TrA and TrB are the reheat steam temperatures on both sides of the boiler.

6. The method for controlling the burnout damper of a coal-fired boiler according to claim 5, characterized in that, The specific formula for calculating the oxygen ratio on both sides of the boiler is as follows: ； in, O2Al and O2Bl represent the oxygen content at the air preheater inlet, while AL and BL represent the number of oxygen measurement points on both sides of the boiler.

7. The method for controlling the burnout damper of a coal-fired boiler according to claim 6, characterized in that, The specific formula for calculating the height of the combustion center is as follows: ； Where H is the height of the combustion center, Hi is the elevation of each burner layer, and Gi is the amount of coal in each burner layer.

8. The method for controlling the burnout damper of a coal-fired boiler according to claim 7, characterized in that, The functional relationship between the burnout damper opening and each parameter is as follows: ； Where ki is the modeling coefficient, ni is the modeling exponent, Xi is the modeling independent variable, and B is the modeling constant term.

9. A method for controlling the burnout damper of a coal-fired boiler according to claim 8, characterized in that, The specific calculation formula for calculating the initial control command of each burnout damper is as follows: ； Where Psk-sp0 is the initial control command for each burnout damper, and Xisp is the expected value of each modeling independent variable.

10. A control system for a burnout damper in a coal-fired boiler, characterized in that, include: The data acquisition module is used to obtain unit parameters from the unit's DCS system or SIS system. The unit parameters include unit load, total secondary air volume of boiler, perimeter damper opening of each burner layer, auxiliary damper opening above and below the burner, burnout damper opening, NOx concentration at the inlet of SCR denitrification unit, main steam temperature on both sides of boiler, reheat steam temperature on both sides of boiler, oxygen content at the air preheater inlet, and coal quantity of each burner layer. The boiler design parameter acquisition module is used to obtain the area of ​​the peripheral air nozzles of each burner, the area of ​​the auxiliary air nozzles of each layer, and the area of ​​each burnout air nozzle based on the boiler design drawings. The burnout air ratio calculation module is used to calculate the burnout air ratio based on the total secondary air volume of the boiler, the opening of the perimeter damper of each layer of burners, the opening of the auxiliary damper above and below the burners, the opening of the burnout damper, the perimeter air nozzle area of ​​each burner of the boiler, the area of ​​each layer of auxiliary air nozzle, and the area of ​​each burnout air nozzle. The main steam temperature ratio calculation module is used to calculate the ratio of the main steam temperatures on both sides of the boiler based on the main steam temperatures on both sides of the boiler. The reheat steam temperature ratio calculation module is used to calculate the reheat steam temperature ratio on both sides of the boiler based on the reheat steam temperatures on both sides of the boiler. The oxygen ratio calculation module is used to calculate the oxygen ratio on both sides of the boiler based on the oxygen content at the air preheater inlet. The combustion center height calculation module is used to calculate the combustion center height based on the coal quantity of each burner layer. The modeling module is used to perform nonlinear modeling with unit load, total secondary air volume of boiler, NOx concentration at the inlet of denitrification system, burnout air ratio, main steam temperature ratio, reheat steam temperature ratio, oxygen ratio, and combustion center height as independent variables and burnout damper opening as dependent variable, so as to obtain the functional relationship between burnout damper opening and each parameter. The control command calculation module is used to calculate the initial control command of each burnout damper based on the modeling results and the expected NOx concentration control target value. The initial control command is corrected through PID calculation to obtain the final control command of each burnout damper. The burnout damper control module is used to control the burnout dampers according to the final control commands of each burnout damper.

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