Method and system for regulating and controlling variable load rate of supercritical carbon dioxide coal-fired power generation system

Abstract

The invention discloses a supercritical carbon dioxide coal-fired power generation system variable load rate regulation and control method and system, and the method comprises the steps: building a multi-field coupling three-dimensional model of a cooling wall in a transient variable load process; based on the multi-field coupling three-dimensional model, carrying out sensitivity analysis on the operation parameters of the cooling wall to obtain an analysis result; the change rate of the operation parameters is subjected to matching regulation and control, and the load changing process of the supercritical carbon dioxide coal-fired power generation system is achieved; based on the analysis result, the variable load rate of the supercritical carbon dioxide coal-fired power generation system is adjusted, the variable load rate is made to be matched with the system load, and regulation and control are completed. According to sensitivity parameter analysis of the performance of the boiler cooling wall, different operation parameters are regulated and controlled respectively, collaborative matching of the parameters is achieved, the variable load rate is jointly regulated, the highest temperature, the temperature change rate and the stress change rate of the cooling wall in the variable load process are reduced, the operation stability of the cooling wall is improved, and the service life of the cooling wall is prolonged.

Description

Technical Field

[0001] This invention relates to the field of coal-fired power generation systems, and specifically to a method and system for regulating the variable load rate of a supercritical carbon dioxide coal-fired power generation system. Background Technology

[0002] The peak-shaving and load-changing capabilities of boilers play a crucial role in modern power systems. With the vigorous development of renewable energy generation, the demand for rapid load change rates and deep peak-shaving capabilities in power generation systems is constantly increasing. Flexible peak-shaving refers to the ability of unit output to meet the load requirements of the power system. Power units must improve their capabilities for rapid start-up, rapid load changes, and low-load operation. Flexible peak-shaving operations involve frequent load changes, which can lead to rapid temperature fluctuations in boiler cooling walls. These fluctuations can cause thermal stress and fatigue, increasing the risk of cracks and fractures, posing a severe challenge to boiler flexibility. Traditional boiler designs are primarily designed for stable load operation and struggle to adapt quickly to large load fluctuations. For example, in wind and solar power generation, due to their intermittent and unpredictable nature, power systems require traditional boilers to rapidly adjust loads within a short period to fill gaps in renewable energy generation or reduce excess power. However, under rapid load-changing conditions, the instability of combustion within the furnace and rapid temperature and stress shocks significantly increase the risk of water-cooled wall overheating and tube rupture accidents. Similarly, the cooling walls of sCO2 boilers also face complex thermal shocks during rapid load changes. Therefore, it is urgent to study the impact of key parameters on the performance of cooling walls during transient processes under varying loads, and to optimize the control methods for varying load processes to improve the stability, safety, and lifespan of cooling wall tubes. Summary of the Invention

[0003] The purpose of this invention is to address the problems of deformation, fatigue, creep, and even tube rupture of the cooling wall of supercritical carbon dioxide coal-fired boilers under high temperature, high pressure, and thermal shock during the transient process of load shaving and peak regulation. The invention proposes a load shaving rate control method and a load shaving regulation optimization method for supercritical carbon dioxide coal-fired power generation systems based on sensitivity analysis and operating condition matching.

[0004] The variable load rate control method for supercritical carbon dioxide coal-fired power generation systems based on sensitivity analysis and operating condition matching can propose reasonable control strategies for boiler variable load transient processes through sensitivity analysis of operating parameters, effectively reducing thermal shock, fatigue, and creep of the cooling wall, and improving the operating stability, flexibility, and service life of the cooling wall.

[0005] The variable load rate control method for supercritical carbon dioxide coal-fired power generation systems based on sensitivity analysis and operating condition matching can achieve stable operation and improve flexibility under partial load conditions of the boiler by reasonably adjusting the matching mechanism of heat flux and mass flow rate.

[0006] To achieve the above objectives, the present invention provides a method for variable load rate regulation in a supercritical carbon dioxide coal-fired power generation system, comprising the following steps:

[0007] Establish a three-dimensional model of the cooling wall with multi-field coupling during transient load changes;

[0008] Based on the multi-field coupled three-dimensional model, sensitivity analysis of the operating parameters of the cooling wall was performed, and the analysis results were obtained.

[0009] The rate of change of the operating parameters is matched and controlled to realize the load change process in the supercritical carbon dioxide coal-fired power generation system.

[0010] Based on the analysis results, the load rate of the supercritical carbon dioxide coal-fired power generation system is adjusted to match the system load, thus completing the regulation.

[0011] Preferably, the multi-field coupled three-dimensional model is constructed and meshed, the physical properties of the fluid field, heat transfer field and mechanical field are defined, and the corresponding boundary conditions and initial conditions are set; the time step and total time of fluid-structure coupling, heat-fluid coupling and transient analysis are set; a numerical solver is selected for iterative solution, and finally the multi-field coupled three-dimensional model of the cooling wall in transient variable load process is established.

[0012] Preferably, the operating parameters include: operating pressure, mass flux, inlet temperature, and wall heat flux; the method for performing the sensitivity analysis includes: based on the multi-field coupled three-dimensional model, performing single-factor perturbation tests, calculating the cross-sectional temperature difference corresponding to each operating parameter; quantifying the sensitivity of each operating parameter by a dimensionless temperature difference ratio, and sorting them according to the ratio value.

[0013] Preferably, the method for adjusting the load change rate includes: analyzing the power system load curve, dividing the load change process into several stages, and setting different load change rates for each stage to achieve matching optimization between the load change rate and the system load; the control strategy includes: coordinating the matching of the operating parameters according to the load increase or decrease process to reduce the maximum temperature of the cooling wall tube, the cross-sectional temperature difference, and maintain the stability of the heat exchange medium temperature change during the transient load change process.

[0014] Preferably, a method of segmented adjustment of the variable load rate and a quadratic parabolic function is used to match the variable load rate with the system load, so that the supercritical carbon dioxide coal-fired power generation system uses a large variable load rate when the load is high and a small variable load rate when the load is low.

[0015] Preferably, the segmented adjustment method includes: dividing the system load into different intervals, setting different variable load rates in each interval; and flexibly adjusting the variable load rates according to the characteristics of different load intervals so that the system can maintain a good operating state in each load segment.

[0016] Preferably, a quadratic parabola function is used to describe the relationship between the load change rate and the system load. By adjusting the parameters of the quadratic parabola function, the shape of the curve is changed to adapt to various load change scenarios and operational requirements, thereby realizing power dispatch.

[0017] The present invention also provides a variable load rate control system for a supercritical carbon dioxide coal-fired power generation system, the system being used to implement the above method, comprising: a construction module, an analysis module, a matching module, and a control module;

[0018] The building module is used to establish a multi-field coupled three-dimensional model of the cooling wall during transient load changes;

[0019] The analysis module is used to perform sensitivity analysis on the operating parameters of the cooling wall based on the multi-field coupled three-dimensional model, and obtain the analysis results.

[0020] The matching module is used to match and regulate the rate of change of the operating parameters to realize the load change process in the supercritical carbon dioxide coal-fired power generation system.

[0021] The control module is used to adjust the variable load rate of the supercritical carbon dioxide coal-fired power generation system based on the analysis results, so that the variable load rate matches the system load, thereby completing the control.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The variable load rate control method of supercritical carbon dioxide coal-fired power generation system based on sensitivity analysis and operating condition matching of the present invention, in the process of boiler operating under different operating conditions, analyzes the sensitivity parameters of boiler cooling wall performance, and controls different operating parameters respectively to achieve coordinated matching between parameters, jointly regulate the variable load rate, reduce the maximum temperature, temperature change rate and stress change rate of the cooling wall during the variable load process, and improve the operating stability and life of the cooling wall.

[0024] (2) The variable load rate control method for supercritical carbon dioxide coal-fired power generation system based on sensitivity analysis and operating condition matching of the present invention matches the variable load rate with the system load. When the load is high, a large variable load rate is used, and when the load is low, a small variable load rate is used. For example, segmented adjustment of the variable load rate or a quadratic parabolic function is used, so that the variable load rate is matched and optimized with the system load, further reducing the creep damage and fatigue damage of the cooling wall and improving the service life of the cooling wall. Attached Figure Description

[0025] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are 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.

[0026] Figure 1 This is a schematic diagram of the method flow according to an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the segmented adjustment of the variable load rate of the cooling wall of a supercritical carbon dioxide coal-fired boiler under different operating conditions, according to an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the variable load rate of a quadratic parabolic function for the cooling wall of a supercritical carbon dioxide coal-fired boiler under varying operating conditions, according to an embodiment of the present invention. Detailed Implementation

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Example 1

[0032] like Figure 1 The diagram shown is a schematic representation of the method flow in this embodiment, and the steps include:

[0033] S1. Establish a three-dimensional model of the cooling wall with multi-field coupling during transient load changes.

[0034] First, a geometric model of the cooling wall is constructed using 3D modeling software, considering its detailed features. Then, mesh generation is performed, selecting an appropriate mesh type and refining key areas while ensuring mesh quality. Next, the physical properties of the fluid field, heat transfer field, and mechanical field are defined, and corresponding boundary and initial conditions are set. Based on this, the time steps and total time for fluid-structure interaction, heat-fluid interaction, and transient analysis are set to achieve multi-field coupling. An appropriate numerical solver is selected for iterative solving, ultimately completing the establishment of a multi-field coupled 3D model of the cooling wall during transient variable load processes.

[0035] Using the established three-dimensional model of the cooling wall with multi-field coupling under transient variable load, the flow and heat transfer processes of the cooling wall are calculated. It is necessary to set the relevant operating parameters and geometric features of the cooling wall flow channels according to the actual situation.

[0036] The specific calculation process for heat transfer in the cooling wall flow is as follows:

[0037] Continuity equation:

[0038]

[0039] Momentum equation:

[0040]

[0041] Energy equation:

[0042]

[0043] Where ρ is density, u is flow velocity, and C p For specific heat capacity, μ t For turbulent dynamic viscosity, λ t δ is the turbulent thermal conductivity. ij For Kronecker notation, x i x j x k The coordinates are represented by x, j, and k (representing the horizontal, vertical, and longitudinal directions, respectively); the superscript "—" indicates the average; the superscript "~" indicates the turbulent fluctuation part; h represents the convective heat transfer coefficient; and g represents the gravitational acceleration.

[0044] This embodiment uses a single supercritical carbon dioxide (sCO2) tube as the research object to study the flow and heat transfer characteristics of the cooling wall tube. Considering the computational workload and accuracy, the length (L) of the cooling wall tube is selected as 1m, the outer diameter D is 35mm, the inner diameter d is 22mm, and the wall thickness is 6.5mm. The flow and heat transfer process of the cooling wall is simulated, and the temperature difference of the cooling wall cross section under the reference operating conditions is calculated.

[0045] S2. Based on the multi-field coupled three-dimensional model, sensitivity analysis of the operating parameters of the cooling wall was performed, and the analysis results were obtained.

[0046] In this embodiment, the operating parameters include operating pressure (P), mass flux (G), inlet temperature (Tin), and wall heat flux (q). Sensitivity analysis is performed to determine the degree to which these parameters affect the cooling wall performance.

[0047] Sensitivity analysis of operating parameters includes:

[0048] (1) Using the established three-dimensional model of multi-field coupling of the cooling wall during transient variable load process, the flow and heat transfer process of the cooling wall are simulated, and the temperature difference of the cooling wall section under the reference working condition is calculated.

[0049] ΔT=T max -T min

[0050] Among them, T max 、T min These represent the highest and lowest temperatures on the cross-section of the cooling wall, respectively.

[0051] (2) Single-factor sensitivity test design: By changing a single parameter variable while keeping the other parameters unchanged, the settings of the running parameters in the model are changed respectively, and the model is used again to calculate the temperature difference of the corresponding sensitivity section to construct a sensitive parameter dataset.

[0052] First, identify the sensitive parameters that may affect the temperature difference across the cooling wall cross-section, such as operating pressure (P), mass flux (G), inlet temperature (Tin), and wall heat flux (q). Next, set the variation factor for each parameter while keeping other parameters constant, and calculate the corresponding cross-sectional temperature difference. Record each parameter and its corresponding cross-sectional temperature difference to form a sensitive parameter dataset.

[0053] (3) Sensitivity quantification and ranking: Calculate the ratio of the cross-sectional temperature difference after changing a single parameter variable to the reference cross-sectional temperature difference under the reference working condition, normalize it to a dimensionless temperature difference ratio, and plot the response curve of each parameter change factor and the cross-sectional temperature difference ratio to obtain the priority ranking of the sensitivity of the key parameters of the cooling wall.

[0054] Calculate the temperature difference at the reference section of the cooling wall:

[0055] ΔT ref =T max，ref -T min，ref

[0056] Among them, T max,ref 、T min,ref These represent the highest and lowest temperatures on the cooling wall cross-section under the reference operating conditions.

[0057] For each sensitive parameter, calculate the corresponding cross-sectional temperature difference while keeping other parameters constant:

[0058] ΔT i =T i，max -T i，min

[0059] Among them, T i,max 、T i,min These represent the highest and lowest temperatures on the cross-section of the cooling wall after the parameters were changed.

[0060] Calculate the ratio of the cross-sectional temperature difference after changing a single parameter variable to the temperature difference of the reference cross-section under the reference working condition, and normalize it to a dimensionless temperature difference ratio. For each changed parameter value, calculate its corresponding dimensionless temperature difference ratio R:

[0061]

[0062] Plot the response curve for each parameter with the parameter change factor on the x-axis and the dimensionless temperature difference ratio R on the y-axis. The parameter change factor is defined as:

[0063] Change factor = changed parameter value / parameter value under reference operating conditions.

[0064] Sensitivity assessment is based on the dimensionless temperature difference ratio principle. The specific method includes: when the dimensionless temperature difference ratio is greater than 1.2 or less than 0.8, it indicates that the parameter is sensitive to the performance of the water-cooled wall; while when the dimensionless temperature difference ratio is between 0.8 and 1.2, it is considered that the parameter is not sensitive to the performance of the water-cooled wall.

[0065] The sensitivity judgment criteria include the principle of sensitivity direction judgment, which includes: if the dimensionless difference ratio is greater than 1, then this parameter has a positive sensitivity relationship with the performance of the water-cooled wall; if the dimensionless difference ratio is less than 1, then this parameter has a negative sensitivity relationship with the performance of the water-cooled wall.

[0066] The priority ranking of the degree of sensitivity is based on the following principle: If the ratio of the cross-sectional temperature difference after changing a single parameter variable to the reference cross-sectional temperature difference under the reference working condition is normalized to a dimensionless temperature difference ratio and compared with the dimensionless difference ratio calculated by changing another single parameter variable, the parameter with a larger dimensionless difference ratio has a strong sensitivity relationship with the water-cooled wall performance, and the parameter with a smaller dimensionless difference ratio has a weak sensitivity relationship with the water-cooled wall performance.

[0067] S3. Match and regulate the rate of change of operating parameters to realize the load change process in the supercritical carbon dioxide coal-fired power generation system.

[0068] For example, the load change process includes load reduction (from 100% to 25%), steady state (25% load), and load increase process (from 25% to 100%).

[0069] During boiler operation, the system load changes according to actual demand. The load change rate refers to how quickly the boiler load changes per unit time. If the load change rate does not match the system load, it may lead to unstable boiler operation or even damage to the equipment. If the load change rate is too low when the load is high, it may not be able to meet the system demand in a timely manner; if the load change rate is too high when the load is low, it may cause excessive thermal stress to the equipment. Matching the load rate with the system load means that during load changes, the system can respond to load changes in a timely and effective manner, maintaining the stability of the cooling wall temperature, cross-sectional temperature difference, and heat exchange medium temperature.

[0070] Specifically, a high load change rate is used when the load is high: When the system load is high, a rapid response to load changes is usually required to meet the demand for high power output. By increasing the load change rate, the boiler can be adjusted to the required high load state more quickly, reducing response time and improving the system's flexibility and efficiency.

[0071] Use a small load change rate when the load is low: When operating at low load, the boiler's thermal load is low, combustion stability is poor, and the equipment is more susceptible to thermal stress. Using a small load change rate can avoid excessive thermal stress on the equipment caused by rapid load changes, thereby reducing creep damage and fatigue damage to the equipment.

[0072] The specific matching optimization is explained below:

[0073] By analyzing the load curve of the power system, dividing the load change process into several stages, and setting different load change rates for each stage, the matching optimization between the load change rate and the system load can be achieved.

[0074] When operating under low load conditions, setting a lower load change rate allows the equipment to adjust at a more stable rate.

[0075] During high-load operation: Set a higher load change rate to quickly respond to rapid load changes and ensure power supply reliability;

[0076] Transition phase: Set an appropriate load change rate according to the rate of load change to ensure the system's continuous response to load changes.

[0077] S4. Based on the analysis results, adjust the load rate of the supercritical carbon dioxide coal-fired power generation system to match the load rate with the system load, thus completing the regulation.

[0078] Based on the results of sensitivity analysis, different operating parameters are adjusted to achieve synergistic matching between parameters, jointly regulate the load change rate, reduce the maximum temperature, temperature change rate, and stress change rate of the cooling wall during the load change process, and improve the stability and flexibility of the cooling wall operation.

[0079] The control strategy is to coordinate and match operating parameters according to the load increase or decrease process in order to reduce the maximum temperature of the cooling wall tube, the cross-sectional temperature difference, and maintain the stability of the temperature change of the heat exchange medium during the transient load change process.

[0080] Cooperative matching methods include: Cooperative matching between parameters can avoid the adverse effects of adjusting a single parameter. By reasonably adjusting the rate of change of different parameters, the parameters can cooperate with each other and work together to achieve the best operating effect.

[0081] During transient load changes in a cooling wall, parameter coordination is a key strategy for optimizing system performance. By appropriately adjusting the rate of change of different parameters, the adverse effects of adjusting a single parameter can be avoided. Specifically, when the load changes, the interrelationships of parameters such as cooling wall operating pressure (P), mass flux (G), inlet temperature (Tin), and wall heat flux (q) need to be comprehensively considered. During load changes, adjusting the rate of change of key parameters such as mass flux (G) and wall heat flux (q) ensures their synergistic effect, thereby achieving efficient operation of the cooling wall during transient load changes, reducing thermal stress, and extending the service life of the cooling wall.

[0082] Subsequently, the load rate was further matched with the system load, so that the supercritical carbon dioxide coal-fired power generation system uses a large load rate when the load is high and a small load rate when the load is low. For example, segmented adjustment of the load rate or a quadratic parabolic function can be used to optimize the matching between the load rate and the system load, thereby further reducing creep damage and fatigue damage to the cooling wall and improving the flexibility and life of the cooling wall.

[0083] (1) Segmented adjustment

[0084] A segmented load rate adjustment method is used to match the load rate with the system load, allowing the supercritical carbon dioxide coal-fired power generation system to use a larger load rate when the load is high and a smaller load rate when the load is low. For example:

[0085] The segmented variable load region can be defined as:

[0086] High-load areas: 100% to 50% of full load;

[0087] Low to medium load area: 50% to 40% load;

[0088] Low load area: 40% load to 30% load;

[0089] Ultra-low load area: 30% load to 25% load.

[0090] During system operation, excessively high load increase / decrease rates can cause instability in the performance of the CO2 cooling wall, leading to localized overheating and excessive stress. Therefore, the load rate is optimized to match the system load using a segmented adjustment method: a larger load rate is used during high loads, and a smaller load rate is used during low loads. This segmented adjustment method effectively reduces the maximum cooling wall temperature and maximum cross-sectional stress throughout the entire load change process, while maintaining a consistent overall outlet fluid temperature trend, thus ensuring system operational stability.

[0091] The steps for segmented load rate adjustment include: dividing the system load into different intervals and setting different load rates in each interval. Based on the characteristics of different load intervals, the load rate is flexibly adjusted to ensure the system maintains a good operating condition in each load segment. For example:

[0092] High-load area: The load is reduced from 100% to 50% at a rate of 5% / min;

[0093] In medium-low load areas: the load is reduced from 50% to 40%, with a load change rate of 4% / min;

[0094] Low load area: The load is reduced from 40% to 30% at a rate of 3% / min;

[0095] Ultra-low load area: 30% load is reduced to 25% load, and the load change rate is 2% / min.

[0096] The schematic diagram of the variable load rate segmented adjustment of the cooling wall under varying operating conditions in this embodiment of the supercritical carbon dioxide coal-fired boiler is shown below. Figure 2 As shown.

[0097] (2) Quadratic parabola function

[0098] Describing the relationship between load variation rate and system load using a quadratic parabolic function is a mathematical model-based optimization method that enables smoother load variation rate adjustments, thereby better matching changes in system load and making system operation more stable. The following is a detailed explanation of this method:

[0099] A quadratic parabola function refers to the change of system load over time, while the rate of change of load refers to the slope of the curve representing this change. Using a quadratic parabola function to describe the relationship between the rate of change of load and system load is an optimization method based on a mathematical model. This method achieves smoother regulation by simulating the slope of the curve representing the change of system load over time, i.e., the rate of change of load. This regulation method can more accurately match the dynamic changes in system load, thereby ensuring more stable operation of the power system.

[0100] The schematic diagram of the variable load rate quadratic parabolic function of the cooling wall under variable operating conditions of the supercritical carbon dioxide coal-fired boiler in this embodiment is shown below. Figure 3 As shown.

[0101] Example 2

[0102] This embodiment also provides a variable load rate control system for a supercritical carbon dioxide coal-fired power generation system, including: a construction module, an analysis module, a matching module, and a control module; the construction module is used to establish a multi-field coupled three-dimensional model of the cooling wall during transient load changes; the analysis module is used to perform sensitivity analysis on the operating parameters of the cooling wall based on the multi-field coupled three-dimensional model to obtain analysis results; the matching module is used to match and control the rate of change of operating parameters to realize the variable load process of the supercritical carbon dioxide coal-fired power generation system; the control module is used to adjust the variable load rate of the supercritical carbon dioxide coal-fired power generation system based on the analysis results, so that the variable load rate matches the system load, thus completing the control.

[0103] The following section will explain in detail how this invention solves technical problems in practical work, taking into account the establishment of this city.

[0104] A multi-field coupled three-dimensional model of the cooling wall during transient load changes was established using building blocks.

[0105] First, a geometric model of the cooling wall is constructed using 3D modeling software, considering its detailed features. Then, mesh generation is performed, selecting an appropriate mesh type and refining key areas while ensuring mesh quality. Next, the physical properties of the fluid field, heat transfer field, and mechanical field are defined, and corresponding boundary and initial conditions are set. Based on this, the time steps and total time for fluid-structure interaction, heat-fluid interaction, and transient analysis are set to achieve multi-field coupling. An appropriate numerical solver is selected for iterative solving, ultimately completing the establishment of a multi-field coupled 3D model of the cooling wall during transient variable load processes.

[0106] Using the established three-dimensional model of the cooling wall with multi-field coupling under transient variable load, the flow and heat transfer processes of the cooling wall are calculated. It is necessary to set the relevant operating parameters and geometric features of the cooling wall flow channels according to the actual situation.

[0107] The specific calculation process for heat transfer in the cooling wall flow is as follows:

[0108] Continuity equation:

[0109]

[0110] Momentum equation:

[0111]

[0112] Energy equation:

[0113]

[0114] Where ρ is density, u is flow velocity, and C p For specific heat capacity, μ t For turbulent dynamic viscosity, λ t δ is the turbulent thermal conductivity. ij For Kronecker notation, x i x j x k The coordinates are represented by x, j, and k (representing the horizontal, vertical, and longitudinal directions, respectively); the superscript "—" indicates the average; the superscript "~" indicates the turbulent fluctuation part; h represents the convective heat transfer coefficient; and g represents the gravitational acceleration.

[0115] This embodiment uses a single supercritical carbon dioxide (sCO2) tube as the research object to study the flow and heat transfer characteristics of the cooling wall tube. Considering the computational workload and accuracy, the length (L) of the cooling wall tube is selected as 1m, the outer diameter D is 35mm, the inner diameter d is 22mm, and the wall thickness is 6.5mm. The flow and heat transfer process of the cooling wall is simulated, and the temperature difference of the cooling wall cross section under the reference operating conditions is calculated.

[0116] The sensitivity analysis of the operating parameters of the cooling wall was performed using the analysis module based on a multi-field coupled three-dimensional model, and the analysis results were obtained.

[0117] In this embodiment, the operating parameters include operating pressure (P), mass flux (G), inlet temperature (Tin), and wall heat flux (q). Sensitivity analysis is performed to determine the degree to which these parameters affect the cooling wall performance.

[0118] Sensitivity analysis of operating parameters includes:

[0119] (1) Using the established three-dimensional model of multi-field coupling of the cooling wall during transient variable load process, the flow and heat transfer process of the cooling wall are simulated, and the temperature difference of the cooling wall section under the reference working condition is calculated.

[0120] ΔT=T max -T min

[0121] Among them, T max 、T min These represent the highest and lowest temperatures on the cross-section of the cooling wall, respectively.

[0122] (2) Single-factor sensitivity test design: By changing a single parameter variable while keeping the other parameters unchanged, the settings of the running parameters in the model are changed respectively, and the model is used again to calculate the temperature difference of the corresponding sensitivity section to construct a sensitive parameter dataset.

[0123] First, identify the sensitive parameters that may affect the temperature difference across the cooling wall cross-section, such as operating pressure (P), mass flux (G), inlet temperature (Tin), and wall heat flux (q). Next, set the variation factor for each parameter while keeping other parameters constant, and calculate the corresponding cross-sectional temperature difference. Record each parameter and its corresponding cross-sectional temperature difference to form a sensitive parameter dataset.

[0124] (3) Sensitivity quantification and ranking: Calculate the ratio of the cross-sectional temperature difference after changing a single parameter variable to the reference cross-sectional temperature difference under the reference working condition, normalize it to a dimensionless temperature difference ratio, and plot the response curve of each parameter change factor and the cross-sectional temperature difference ratio to obtain the priority ranking of the sensitivity of the key parameters of the cooling wall.

[0125] Calculate the temperature difference at the reference section of the cooling wall:

[0126] ΔT ref =T max，ref -T min，ref

[0127] Among them, T max,ref 、T min,ref These represent the highest and lowest temperatures on the cooling wall cross-section under the reference operating conditions.

[0128] For each sensitive parameter, calculate the corresponding cross-sectional temperature difference while keeping other parameters constant:

[0129] ΔT=T i，max -T i，min

[0130] Among them, T i,max 、T i,min These represent the highest and lowest temperatures on the cross-section of the cooling wall after the parameters were changed.

[0131] Calculate the ratio of the cross-sectional temperature difference after changing a single parameter variable to the temperature difference of the reference cross-section under the reference working condition, and normalize it to a dimensionless temperature difference ratio. For each changed parameter value, calculate its corresponding dimensionless temperature difference ratio R:

[0132]

[0133] Plot the response curve for each parameter with the parameter change factor on the x-axis and the dimensionless temperature difference ratio R on the y-axis. The parameter change factor is defined as:

[0134] Change factor = changed parameter value / parameter value under reference operating conditions.

[0135] Sensitivity assessment is based on the dimensionless temperature difference ratio principle. The specific method includes: when the dimensionless temperature difference ratio is greater than 1.2 or less than 0.8, it indicates that the parameter is sensitive to the performance of the water-cooled wall; while when the dimensionless temperature difference ratio is between 0.8 and 1.2, it is considered that the parameter is not sensitive to the performance of the water-cooled wall.

[0136] The sensitivity judgment criteria include the principle of sensitivity direction judgment, which includes: if the dimensionless difference ratio is greater than 1, then this parameter has a positive sensitivity relationship with the performance of the water-cooled wall; if the dimensionless difference ratio is less than 1, then this parameter has a negative sensitivity relationship with the performance of the water-cooled wall.

[0137] The priority ranking of the degree of sensitivity is based on the following principle: If the ratio of the cross-sectional temperature difference after changing a single parameter variable to the reference cross-sectional temperature difference under the reference working condition is normalized to a dimensionless temperature difference ratio and compared with the dimensionless difference ratio calculated by changing another single parameter variable, the parameter with a larger dimensionless difference ratio has a strong sensitivity relationship with the water-cooled wall performance, and the parameter with a smaller dimensionless difference ratio has a weak sensitivity relationship with the water-cooled wall performance.

[0138] By utilizing a matching module to control the rate of change of operating parameters, the variable load process in a supercritical carbon dioxide coal-fired power generation system can be realized. For example:

[0139] The load change process includes load reduction (from 100% to 25%), steady state (25% load), and load increase process (from 25% to 100%).

[0140] During boiler operation, the system load changes according to actual demand. The load change rate refers to how quickly the boiler load changes per unit time. If the load change rate does not match the system load, it may lead to unstable boiler operation or even damage to the equipment. If the load change rate is too low when the load is high, it may not be able to meet the system demand in a timely manner; if the load change rate is too high when the load is low, it may cause excessive thermal stress to the equipment. Matching the load rate with the system load means that during load changes, the system can respond to load changes in a timely and effective manner, maintaining the stability of the cooling wall temperature, cross-sectional temperature difference, and heat exchange medium temperature.

[0141] Specifically, a high load change rate is used when the load is high: When the system load is high, a rapid response to load changes is usually required to meet the demand for high power output. By increasing the load change rate, the boiler can be adjusted to the required high load state more quickly, reducing response time and improving the system's flexibility and efficiency.

[0142] Use a small load change rate when the load is low: When operating at low load, the boiler's thermal load is low, combustion stability is poor, and the equipment is more susceptible to thermal stress. Using a small load change rate can avoid excessive thermal stress on the equipment caused by rapid load changes, thereby reducing creep damage and fatigue damage to the equipment.

[0143] The specific matching optimization is explained below:

[0144] By analyzing the load curve of the power system, dividing the load change process into several stages, and setting different load change rates for each stage, the matching optimization between the load change rate and the system load can be achieved.

[0145] When operating under low load conditions, setting a lower load change rate allows the equipment to adjust at a more stable rate.

[0146] During high-load operation: Set a higher load change rate to quickly respond to rapid load changes and ensure power supply reliability;

[0147] Transition phase: Set an appropriate load change rate according to the rate of load change to ensure the system's continuous response to load changes.

[0148] Based on the analysis results, the control module adjusts the variable load rate of the supercritical carbon dioxide coal-fired power generation system to match the variable load rate with the system load, thus completing the control.

[0149] Based on the results of sensitivity analysis, different operating parameters are adjusted to achieve synergistic matching between parameters, jointly regulate the load change rate, reduce the maximum temperature, temperature change rate, and stress change rate of the cooling wall during the load change process, and improve the stability and flexibility of the cooling wall operation.

[0150] The control strategy is to coordinate and match operating parameters according to the load increase or decrease process in order to reduce the maximum temperature of the cooling wall tube, the cross-sectional temperature difference, and maintain the stability of the temperature change of the heat exchange medium during the transient load change process.

[0151] Cooperative matching methods include: Cooperative matching between parameters can avoid the adverse effects of adjusting a single parameter. By reasonably adjusting the rate of change of different parameters, the parameters can cooperate with each other and work together to achieve the best operating effect.

[0152] During transient load changes in a cooling wall, parameter coordination is a key strategy for optimizing system performance. By appropriately adjusting the rate of change of different parameters, the adverse effects of adjusting a single parameter can be avoided. Specifically, when the load changes, the interrelationships of parameters such as cooling wall operating pressure (P), mass flux (G), inlet temperature (Tin), and wall heat flux (q) need to be comprehensively considered. During load changes, adjusting the rate of change of key parameters such as mass flux (G) and wall heat flux (q) ensures their synergistic effect, thereby achieving efficient operation of the cooling wall during transient load changes, reducing thermal stress, and extending the service life of the cooling wall.

[0153] Subsequently, the load rate was further matched with the system load, so that the supercritical carbon dioxide coal-fired power generation system uses a large load rate when the load is high and a small load rate when the load is low. For example, segmented adjustment of the load rate or a quadratic parabolic function can be used to optimize the matching between the load rate and the system load, thereby further reducing creep damage and fatigue damage to the cooling wall and improving the flexibility and life of the cooling wall.

[0154] (1) Segmented adjustment

[0155] A segmented load rate adjustment method is used to match the load rate with the system load, allowing the supercritical carbon dioxide coal-fired power generation system to use a larger load rate when the load is high and a smaller load rate when the load is low. For example:

[0156] The segmented variable load region can be defined as:

[0157] High-load areas: 100% to 50% of full load;

[0158] Low to medium load area: 50% to 40% load;

[0159] Low load area: 40% load to 30% load;

[0160] Ultra-low load area: 30% load to 25% load.

[0161] During system operation, excessively high load increase / decrease rates can cause instability in the performance of the CO2 cooling wall, leading to localized overheating and excessive stress. Therefore, the load rate is optimized to match the system load using a segmented adjustment method: a larger load rate is used during high loads, and a smaller load rate is used during low loads. This segmented adjustment method effectively reduces the maximum cooling wall temperature and maximum cross-sectional stress throughout the entire load change process, while maintaining a consistent overall outlet fluid temperature trend, thus ensuring system operational stability.

[0162] The steps for segmented load rate adjustment include: dividing the system load into different intervals and setting different load rates in each interval. Based on the characteristics of different load intervals, the load rate is flexibly adjusted to ensure the system maintains a good operating condition in each load segment. The adjustment process is as follows:

[0163] High-load area: The load is reduced from 100% to 50% at a rate of 5% / min;

[0164] In medium-low load areas: the load is reduced from 50% to 40%, with a load change rate of 4% / min;

[0165] Low load area: The load is reduced from 40% to 30% at a rate of 3% / min;

[0166] Ultra-low load area: 30% load is reduced to 25% load, and the load change rate is 2% / min.

[0167] The schematic diagram of the variable load rate segmented adjustment of the cooling wall under varying operating conditions in this embodiment of the supercritical carbon dioxide coal-fired boiler is shown below. Figure 2 As shown.

[0168] (2) Quadratic parabola function

[0169] Describing the relationship between load variation rate and system load using a quadratic parabolic function is a mathematical model-based optimization method that enables smoother load variation rate adjustments, thereby better matching changes in system load and making system operation more stable. The following is a detailed explanation of this method:

[0170] A quadratic parabola function refers to the change of system load over time, while the rate of change of load refers to the slope of the curve representing this change. Using a quadratic parabola function to describe the relationship between the rate of change of load and system load is an optimization method based on a mathematical model. This method achieves smoother regulation by simulating the slope of the curve representing the change of system load over time, i.e., the rate of change of load. This regulation method can more accurately match the dynamic changes in system load, thereby ensuring more stable operation of the power system.

[0171] The schematic diagram of the variable load rate quadratic parabolic function of the cooling wall under variable operating conditions of the supercritical carbon dioxide coal-fired boiler in this embodiment is shown below. Figure 3 As shown.

[0172] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for regulating the variable load rate of a supercritical carbon dioxide coal-fired power generation system, characterized by the following steps: include: Establish a three-dimensional model of the cooling wall with multi-field coupling during transient load changes; Based on the multi-field coupled three-dimensional model, sensitivity analysis of the operating parameters of the cooling wall was performed, and the analysis results were obtained. The rate of change of the operating parameters is matched and controlled to realize the load change process in the supercritical carbon dioxide coal-fired power generation system. Based on the analysis results, the load rate of the supercritical carbon dioxide coal-fired power generation system is adjusted to match the system load, thus completing the regulation.

2. The method for variable load rate control of a supercritical carbon dioxide coal-fired power generation system according to claim 1, characterized in that, The multi-field coupled three-dimensional model is constructed and meshed. The physical properties of the fluid field, heat transfer field and mechanical field are defined, and the corresponding boundary conditions and initial conditions are set. Set the time step and total time for fluid-structure interaction, thermal-fluid interaction, and transient analysis; select a numerical solver for iterative solution, and finally complete the establishment of a three-dimensional model of the cooling wall with multi-field coupling during transient variable load process.

3. The method for variable load rate control of a supercritical carbon dioxide coal-fired power generation system according to claim 1, characterized in that, The operating parameters include: operating pressure, mass flux, inlet temperature, and wall heat flux; the method for performing the sensitivity analysis includes: based on the multi-field coupled three-dimensional model, performing single-factor perturbation tests, calculating the cross-sectional temperature difference corresponding to each operating parameter; quantifying the sensitivity of each operating parameter by the dimensionless temperature difference ratio, and sorting them according to the ratio value.

4. The method for variable load rate control of a supercritical carbon dioxide coal-fired power generation system according to claim 1, characterized in that, The method for adjusting the load change rate includes: analyzing the power system load curve, dividing the load change process into several stages, and setting different load change rates for each stage to achieve matching optimization between the load change rate and the system load; the control strategy includes: coordinating the matching of the operating parameters according to the load increase or decrease process to reduce the maximum temperature of the cooling wall tube, the cross-sectional temperature difference, and maintain the stability of the heat exchange medium temperature change during the transient load change process.

5. The method for regulating the load rate of a supercritical carbon dioxide coal-fired power generation system according to claim 4, characterized in that, By employing segmented adjustment of the variable load rate and a quadratic parabolic function, the variable load rate is matched with the system load, allowing the supercritical carbon dioxide coal-fired power generation system to use a large variable load rate when the load is high and a small variable load rate when the load is low.

6. The method for variable load rate control of a supercritical carbon dioxide coal-fired power generation system according to claim 5, characterized in that, The segmented adjustment method includes: dividing the system load into different intervals and setting different variable load rates in each interval; flexibly adjusting the variable load rates according to the characteristics of different load intervals so that the system can maintain a good operating state in each load segment.

7. The method for regulating the load rate of a supercritical carbon dioxide coal-fired power generation system according to claim 5, characterized in that, A quadratic parabola function is used to describe the relationship between the load change rate and the system load. By adjusting the parameters of the quadratic parabola function, the shape of the curve is changed to adapt to various load change scenarios and operational requirements, thereby completing power dispatch.

8. A variable load rate control system for a supercritical carbon dioxide coal-fired power generation system, said system being used to implement the method described in any one of claims 1-7, characterized in that, include: Modules include: construction module, analysis module, matching module, and control module. The building module is used to establish a multi-field coupled three-dimensional model of the cooling wall during transient load changes; The analysis module is used to perform sensitivity analysis on the operating parameters of the cooling wall based on the multi-field coupled three-dimensional model, and obtain the analysis results. The matching module is used to match and regulate the rate of change of the operating parameters to realize the load change process in the supercritical carbon dioxide coal-fired power generation system. The control module is used to adjust the variable load rate of the supercritical carbon dioxide coal-fired power generation system based on the analysis results, so that the variable load rate matches the system load, thereby completing the control.

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