An intelligent early warning method for water inlet of a direct-flow boiler separator based on dynamic fusion of ceiling temperature, water supply temperature and separator pressure

Abstract

The application discloses a kind of based on ceiling temperature, feedwater temperature and separator pressure dynamic fusion direct-flow boiler separator water inlet intelligent early warning method, belong to thermal power plant unit direct-flow boiler operation control field.The method is by real-time acquisition ceiling temperature, coal economizer feedwater temperature, separator pressure change rate, feedwater flow and steam flow and other parameters, constructs dynamic enthalpy calculation model to solve separator inlet working medium enthalpy, and establishes water inlet risk index evaluation model.According to the different load setting condition adaptive coefficient, when risk index absolute value is greater than or equal to 50, trigger alarm, prompt to increase fuel quantity and reduce feedwater flow.The application solves the problem of false water level compensation over-reliance on pressure change rate under deep regulation condition, improves the accuracy of separator water inlet risk identification, early warning response time is 10-15 seconds in advance, can effectively avoid misoperation under deep regulation condition, applicable to supercritical / ultra-supercritical direct-flow boiler deep peak regulation condition.

Description

Technical Field

[0001] This invention relates to the field of thermal power generating unit operation control technology, and in particular to a method for intelligent early warning of water inlet in a DC boiler separator based on the dynamic integration of roof temperature, feedwater temperature and separator pressure. Background Technology

[0002] In the operation of supercritical / ultra-supercritical once-through boilers, the intermediate point superheat and separator water level are key factors for adjusting the feedwater flow. Current technologies primarily rely on pressure change rate compensation mechanisms to address false water level issues; their core logic is... However, this mechanism has significant flaws: Single parameter dependence: Compensation is based solely on the rate of pressure change, which cannot respond to key disturbances such as combustion disturbances (e.g., sudden changes in ceiling temperature) and sudden drops in feedwater temperature. Deep adjustment failure: At low load (<300MW), the pressure fluctuation is large and the compensation coefficient k cannot be adaptively adjusted, resulting in insufficient compensation; High risk of misjudgment: When a sudden pressure rise occurs at the same time as water seepage in the separator, it can easily lead to operators excessively reducing the feedwater, causing the feedwater flow rate to fall below the boiler MFT protection value and causing the unit to trip. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides an intelligent early warning method for separator water inlet in a DC boiler based on the dynamic fusion of roof temperature, feedwater temperature, and separator pressure, in order to solve the problems of low accuracy and easy misjudgment of separator water inlet warning under deep adjustment conditions in existing technologies.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for intelligent early warning of water inlet in a once-through boiler separator based on dynamic fusion of roof temperature, feedwater temperature, and separator pressure includes the following steps: Real-time acquisition of multi-source parameters: Acquiring the temperature T of the roof outlet header. 顶棚 Used to reflect the extension of the evaporation section caused by combustion disturbance, economizer inlet feedwater temperature T 给水 As a reference for the initial thermodynamic state of the working fluid, the separator pressure P and the feedwater flow rate G 给水 and main steam flow rate G 蒸汽 The pressure change rate of the separator was obtained through differential calculation. ; Construction of dynamic enthalpy calculation model: through formula Real-time calculation of the enthalpy of the working fluid at the separator inlet, where, The isobaric specific heat capacity of the working fluid is taken as 4.18 kJ / (kg·℃). This represents the saturated water enthalpy corresponding to the feedwater temperature. This is a pressure change rate correction coefficient, with a value ranging from 0.5 to 1.5 kJ·s / (kg·MPa), used to compensate for the endothermic hysteresis effect caused by sudden pressure changes; Real-time calculation of water ingress risk index: via formula Calculate the risk index, where, This represents the enthalpy of saturated water at the current separator pressure. , For adaptive coefficients under operating conditions; Threshold triggering logic and risk level warning: Different levels of warnings are triggered based on the absolute value of the risk index R, and corresponding control actions are executed.

[0005] Furthermore, in the real-time acquisition step of the multi-source parameters, the temperature of the roof outlet header is used to reflect the extension of the evaporation section caused by combustion disturbance, the feedwater temperature at the economizer inlet is used as the reference for the initial thermodynamic state of the working fluid, and the pressure change rate of the separator is obtained by differential calculation through the pressure sensor, with a sampling period of 0.5 seconds.

[0006] Furthermore, the steps for constructing the dynamic enthalpy calculation model include: Basic enthalpy calculation: ,in The static theoretical enthalpy value when pressure fluctuations are ignored; Dynamic correction of pressure change rate: ,in The value ranges from 0.5 to 1.5 kJ·s / (kg·MPa), and is determined through experimental calibration.

[0007] Furthermore, the adaptive coefficient for the operating condition , Dynamic adjustments based on unit load: When the unit load is ≥300MW The value ranges from 0.5 to 0.8. Values ​​range from 0.1 to 0.15; When the unit load is <300MW The value ranges from 0.9 to 1.2. The value ranges from 0.2 to 0.3.

[0008] Furthermore, in the threshold triggering logic and risk classification early warning steps, the risk level classification and response actions are as follows: Low risk: When When the value is ≤3, no active intervention is performed; only the parameters are recorded. Medium risk: When 3 < When the flow rate is less than 50, an audible and visual alarm will be activated, prompting a reduction in water supply flow. High risk: When When the flow rate is ≥50, the interlock control is triggered, reducing the water supply flow rate by ≥10% of the rated flow rate and increasing the fuel quantity by ≥5%.

[0009] Furthermore, the aforementioned and All data were obtained through the IAPWS-97 water vapor meter. According to the economizer inlet feedwater temperature query Query based on the current separator pressure.

[0010] Furthermore, the water supply flow rate G 给水 and main steam flow rate G 蒸汽 Used to verify the working fluid mass balance, when the feedwater flow rate and the main steam flow rate are dynamically unbalanced, the separator inlet water status is judged in conjunction with the risk index.

[0011] Furthermore, it also includes a feedback optimization mechanism, which uses historical operating data to optimize the dynamic enthalpy calculation model. Value and operating condition adaptive coefficient , Optimize and adjust.

[0012] Furthermore, the method is implemented through a dedicated algorithm module deployed in the boiler DCS system, which includes a data acquisition unit, a dynamic enthalpy calculation unit, a risk index assessment unit, and an early warning control unit.

[0013] Furthermore, the data acquisition unit employs sensors including: a K-type thermocouple for measuring the temperature of the roof outlet header, a Pt100 resistance thermometer for measuring the feedwater temperature at the economizer inlet, a differential pressure transmitter for measuring the pressure of the separator, and an electromagnetic flowmeter for measuring the feedwater flow rate and the main steam flow rate.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. By integrating multiple parameters such as ceiling temperature, water supply temperature, and pressure change rate, a dynamic enthalpy model and a risk index assessment model are constructed to effectively distinguish between real and false water levels, avoid misjudgments caused by a single pressure parameter, and significantly improve the accuracy of early warning.

[0015] 2. Compared with existing technologies, the early warning response time is earlier, providing operators with more time to make adjustments.

[0016] 3. Through the adaptive coefficient of working conditions , The dynamic adjustment can still maintain a good early warning effect under the deep adjustment condition of 30% rated load (<300MW).

[0017] 4. By implementing tiered early warning and interlocking control, we can prevent operators from over-adjusting the water supply flow due to misjudgment, thus preventing accidents such as unit tripping and reducing the risk of misoperation. 5. Actual verification shows that the reduction in annual maintenance costs is mainly due to the decrease in unplanned downtime events. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a flowchart illustrating the dynamic enthalpy calculation process according to an embodiment of the present invention. Figure 2 This is a flowchart of the intelligent early warning method according to an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] This invention analyzes the causes of the problem based on field experiments, specifically: Boiler Overview: The No. 4 boiler in the second phase of a power plant, a 650MW supercritical unit, is a supercritical parameter composite variable-voltage once-through Bunsen type boiler manufactured by Dongfang Boiler Factory, model DG1950 / 25.4-Ⅱ5. The boiler is equipped with an expansion center point, which, through horizontal and vertical guidance and constraint, achieves three-dimensional expansion centered on a certain height of the boiler, and prevents cracking of the furnace top and walls and deformation of the heating surface.

[0021] Test Procedure: In March 2025, Unit #4 underwent a deep-load operation test on the separator's spurious water level characteristics, with a target load set at 180MW. The test focused on the 30% rated load (180MW) range, operating entirely in turbine-following control mode, with valve 361 not opened or closed, and the heating surface temperatures remaining within safe thresholds. The specific implementation details are as follows: At 09:38, the unit load dropped to 180MW, and the #4D coal mill was shut down while the AC mill remained in operation. At 09:40, a change in the water phase occurred in the separator of boiler #4. Monitoring data showed: vertical water-cooled wall outlet header feedwater temperature 322.1℃, economizer inlet feedwater pressure 10.8MPa, steam-water separator metal outer wall temperature 329℃, separator water tank outlet pressure 10.64MPa, roof outlet header temperature 324.2℃, intermediate point superheat 5.7℃, feedwater header flow rate 483t / h, main steam flow rate 466t / h, feedwater header temperature 221.9℃, and initial steam-water separator water level 0m. When the separator water level showed an upward trend, the operator immediately adjusted the feedwater flow rate. At 09:42, the parameters during the period of unit load 174MW were as follows: separator water level 15m, midpoint superheat 4.7℃, feedwater flow rate 410t / h, separator pressure 10.75MPa, steam-water separator metal outer wall temperature 328℃, and roof outlet header temperature 324℃. At 09:42:48, when the load recovered to 179MW, the system parameters were as follows: vertical water-cooled wall outlet header feedwater temperature 322.5℃, economizer inlet feedwater pressure 10.87MPa, steam-water separator metal outer wall temperature 327℃, separator water tank outlet pressure 10.8MPa, roof outlet header temperature 324.5℃, intermediate point superheat 5.0℃, feedwater header flow rate 342t / h, main steam flow rate 472t / h, feedwater header temperature 217℃, and steam-water separator water level reached 25m full value.

[0022] Monitoring throughout the test showed that the separator pressure exhibited a continuous upward trend.

[0023] The timing analysis of key operating parameters (09:40~09:42:48) is shown in Table 1 below:

[0024] The entire experimental process revealed that: 1. Separator pressure parameter evolution: The pressure was 10.75 MPa at 09:42, rising to 10.87 MPa at 09:42:48, with a pressure change rate of 0.0025 MPa / s (2.5 kPa / s). Steam density change analysis: Under the operating condition of 10.8 MPa pressure, the saturated steam density is 65.3 kg / m³; when the pressure rises to 10.87 MPa, the density increases to 67.1 kg / m³, an increase of 2.7%. This density change causes the steam inside the separator to be compressed, thus leading to the phenomenon of falsely high water level measurements.

[0025] 2. Analysis of superheat parameters at the intermediate point: At 09:42, the superheat was 4.7℃, close to the saturation temperature of 317.5℃ corresponding to 10.75MPa, indicating that the working fluid at the evaporation section outlet is in a wet steam state. Comparison of roof temperature and separator temperature: The saturated steam temperature corresponding to 10.8MPa is 318℃, while the measured roof outlet temperature is 324℃, with a superheat of only 6℃. The actual operating conditions have exceeded the saturation temperature value corresponding to the current pressure.

[0026] 3. The dynamic relationship between water flow rate and steam flow rate shows that the actual water level in the separator should be decreasing. However, the monitoring system shows that the water level is rising abnormally, which is therefore determined to be a false water level phenomenon.

[0027] Through a full-process tracing analysis, the abnormal water seepage phenomenon in the separator was mainly caused by the following factors: The core logic of the separator false water level compensation mechanism is based on the pressure change rate ( ) for water level measurement value (H 测量 Implement dynamic correction: The compensation coefficient k in the formula was determined by experimental calibration, and its normal operating range is 0.5-2 mm·min / MPa.

[0028] This compensation mechanism aims to eliminate the instantaneous volume expansion / contraction effect of the working fluid caused by sudden pressure changes, typically such as the false water level rise caused by the increase in steam specific volume during a sudden pressure drop. It should be noted that the current compensation mechanism has inherent limitations: the compensation formula only applies to false water level corrections induced by sudden pressure changes, and its correction efficiency is significantly reduced in deep peak shaving and load reduction conditions; the compensation coefficient may increase significantly under deep shaving conditions. Furthermore, the current pressure change rate compensation mechanism has no correction capability for the following conditions: actual water level rises and falls caused by changes in working fluid quality, typically manifested as an actual water level rise accompanied by a decrease in superheat; evaporation section extension caused by sudden feedwater temperature changes, where the compensation mechanism can only partially offset the pressure effect when separator pressure changes are coupled with combustion disturbances (roof temperature changes) or feedwater temperature fluctuations; and heat transfer offset caused by abnormal combustion regulation, such as when a sudden pressure drop occurs during load reduction, and if the roof temperature rises abnormally due to inaccurate combustion regulation, it will cause the evaporation section to shift backward and generate visible water level fluctuations.

[0029] Specific mechanism explanation: When the load changes drastically, the violent fluctuations in separator pressure will lead to abrupt changes in water / steam density, which in turn induces water level expansion or contraction effects; the dynamic imbalance between steam flow and feedwater flow originates from the lag in fuel quantity or feedwater flow regulation, ultimately resulting in abnormal working fluid phase change rate. Therefore, this invention is used to solve the problem of water inlet in separators.

[0030] Example 1 like Figure 1 As shown in the figure, this invention proposes an intelligent early warning method for the inlet water of a once-through boiler separator based on the dynamic fusion of roof temperature, feedwater temperature, and separator pressure, including: 1. Equipment selection and deployment: Temperature measurement of the roof outlet header: K-type thermocouple, model WRN-130, measuring range 0-1200℃, accuracy ±1.5℃; Economizer inlet feedwater temperature measurement: Pt100 resistance thermometer, model WZP-230, measurement range -200-650℃, accuracy ±0.5℃; Separator pressure measurement: A differential pressure transmitter, model Rosemount3051CD, is used, with a measurement range of 0-40MPa and an accuracy of ±0.075%. Water supply flow and main steam flow measurement: Electromagnetic flow meter, model E+HPromagW400, with a measurement accuracy of ±0.5%; Data processing unit: adopts Siemens S7-400 PLC, equipped with CP443-1 communication module, sampling period 0.5 seconds.

[0031] 2. Real-time acquisition of multi-source parameters, as shown in Table 1: The parameters collected at 09:42:48 are as follows: Ceiling temperature =324.5℃; water supply temperature =217℃; The separator pressure p = 10.87 MPa; Water supply flow rate G 给水 =342t / h; Main steam flow rate G 蒸汽 =472t / h; Pressure change rate =0.12MPa / s (calculated by the difference between the current pressure and the pressure 0.5 seconds ago).

[0032] 3. Calculation of dynamic enthalpy: Basic enthalpy calculation: =4.18×(324.5-217)+ According to the IAPWS-97 table, at 217℃ =923kJ / kg, therefore =4.18×107.5+923=1352kJ / kg; Dynamic correction: If the experimental calibration value is taken as 1.2 kJ·s / (kg·MPa), then Δh = 1.2 × 0.12 = 0.144 kJ / kg; Final entry enthalpy: =1352+0.144=1352.144kJ / kg.

[0033] 4. Calculation of water ingress risk index: The enthalpy of saturated water at 10.87 MPa is obtained from the IAPWS-97 table. =1408kJ / kg; The unit load is 179MW < 300MW, therefore =0.9, =0.2; Risk Index: =0.9×(1352.144-1408)+0.2×0.12=-50.29, =50.29≥50, triggering a high-risk warning.

[0034] 5. Early warning response execution: Interlock control action: Reduce water supply flow to 342×(1-10%)=307.8t / h, increase fuel quantity by 5%, corresponding to a load increase to 179×1.05=187.95MW, and close the desuperheating water electric valve.

[0035] Example 2 Verification of early warning methods under normal load conditions: 1. Operating parameters: Unit load ≥ 300MW, collected parameters are as follows: =350℃, =250℃, p=16MPa, =0.05MPa / s, G 给水 =800t / h, G 蒸汽 =790t / h; 2. Calculation of dynamic enthalpy: (250℃) = 1048kJ / kg =4.18×(350-250)+1048=418+1048=1466kJ / kg; =0.8, Δh=0.8×0.05=0.05kJ / kg, =1466 + 0.04 = 1466.04 kJ / kg; 3. Risk Index Calculation: (16MPa) = 1628kJ / kg =0.6, =0.12; =0.6×(1466.04-1628)+0.12×0.05=-97.176+0.006=-97.17; =97.17≥50, triggering a high-risk warning, the system automatically reduces the water supply flow by 80t / h and increases the fuel quantity by 5%, effectively preventing water from entering the separator.

[0036] The core principle of this invention, which achieves separator water ingress early warning through multi-parameter dynamic fusion, is as follows: Dynamic correction of combustion disturbance by roof temperature: Roof temperature reflects combustion intensity and evaporation section position. When abnormal combustion regulation causes the evaporation section to shift backward, the deviation between roof temperature and saturation temperature can directly reflect the change in superheat of the working fluid, making up for the deficiency that single pressure compensation cannot respond to combustion disturbance. Feedwater temperature calibration of the initial enthalpy of the working fluid: The feedwater temperature serves as the reference for the initial thermodynamic state of the working fluid. The corresponding saturated water enthalpy is queried using the IAPWS-97 algorithm, providing an accurate starting point for dynamic enthalpy calculation and eliminating the interference of sudden changes in feedwater temperature on the early warning results. Precise compensation for false water level by pressure change rate: Combined with the adaptive coefficient of working condition, the compensation weight of pressure change rate for false water level is enhanced under deep adjustment working conditions, which solves the problem of insufficient compensation by traditional compensation mechanism at low load. Quantitative decision-making based on risk index: By weighting the working fluid subcooling and pressure change rate to calculate the risk index, a quantitative early warning threshold is established, realizing the upgrade from "qualitative judgment" to "quantitative decision-making", significantly improving the reliability and operability of early warning.

[0037] When water enters the separator, a water ingress risk index assessment method can be used to dynamically adjust the fuel supply system and feedwater control logic, thereby effectively avoiding the risk of misoperation caused by blind operation. Verification under actual operating conditions shows that this method is highly effective: For the recorded separator full-water event at 09:42:48, the mathematical model constructed in this study was used for verification analysis: the system successfully detected the abnormal characteristic parameter R=2.3 at 09:42:00 (48 seconds in advance), accurately identifying the potential causes of separator full-water under deep-adjustment conditions and implementing control strategy optimization, effectively preventing operator errors caused by full container level.

[0038] Economic benefit analysis shows that annual maintenance costs can be reduced by 12%-15%, mainly due to the reduction in unplanned downtime events.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for intelligent early warning of water inlet in a once-through boiler separator based on dynamic fusion of roof temperature, feedwater temperature, and separator pressure, characterized in that, Includes the following steps: Real-time acquisition of multi-source parameters: Acquiring the temperature T of the roof outlet header. 顶棚 Economizer inlet feedwater temperature T 给水 Separator pressure P, feedwater flow rate G 给水 and main steam flow rate G 蒸汽 The pressure change rate of the separator was obtained through differential calculation. ; Construction of dynamic enthalpy calculation model: through formula Real-time calculation of the enthalpy of the working fluid at the separator inlet, where, The specific heat capacity of the working fluid at constant pressure This represents the saturated water enthalpy corresponding to the feedwater temperature. This is the correction factor for the rate of change of pressure; Real-time calculation of water ingress risk index: via formula Calculate the risk index, where, This represents the enthalpy of saturated water at the current separator pressure. , For adaptive coefficients under operating conditions; Threshold triggering logic and risk level warning: Different levels of warnings are triggered based on the absolute value of the risk index R, and corresponding control actions are executed.

2. The intelligent early warning method for inlet water of a once-through boiler separator based on the dynamic fusion of roof temperature, feedwater temperature, and separator pressure as described in claim 1, characterized in that, In the real-time acquisition step of the multi-source parameters, the temperature of the roof outlet header is used to reflect the extension of the evaporation section caused by combustion disturbance, the feedwater temperature at the economizer inlet is used as the reference for the initial thermodynamic state of the working fluid, and the pressure change rate of the separator is obtained by differential calculation through the pressure sensor, with a sampling period of 0.5 seconds.

3. The intelligent early warning method for inlet water of a once-through boiler separator based on the dynamic fusion of roof temperature, feedwater temperature, and separator pressure as described in claim 1, characterized in that, The steps for constructing the dynamic enthalpy calculation model include: Basic enthalpy calculation: ,in The static theoretical enthalpy value when pressure fluctuations are ignored; Dynamic correction of pressure change rate: ,in The value ranges from 0.5 to 1.5 kJ·s / (kg·MPa), and is determined through experimental calibration.

4. The intelligent early warning method for inlet water of a once-through boiler separator based on the dynamic fusion of roof temperature, feedwater temperature, and separator pressure as described in claim 1, characterized in that, The adaptive coefficient of the working condition , Dynamic adjustments based on unit load: When the unit load is ≥300MW The value ranges from 0.5 to 0.

8. Values ​​range from 0.1 to 0.15; When the unit load is <300MW The value ranges from 0.9 to 1.

2. The value ranges from 0.2 to 0.

3.

5. The intelligent early warning method for inlet water of a once-through boiler separator based on the dynamic fusion of roof temperature, feedwater temperature, and separator pressure as described in claim 1, characterized in that, In the threshold triggering logic and risk classification early warning steps, the risk level classification and response actions are as follows: Low risk: When When the value is ≤3, no active intervention is performed; only the parameters are recorded. Medium risk: When 3 < When the flow rate is less than 50, an audible and visual alarm will be activated, prompting a reduction in water supply flow. High risk: When When the flow rate is ≥50, the interlock control is triggered, reducing the water supply flow rate by ≥10% of the rated flow rate and increasing the fuel quantity by ≥5%.

6. The intelligent early warning method for inlet water of a once-through boiler separator based on the dynamic fusion of roof temperature, feedwater temperature, and separator pressure as described in claim 1, characterized in that, The and All data were obtained through the IAPWS-97 water vapor meter. According to the economizer inlet feedwater temperature query Query based on the current separator pressure.

7. The intelligent early warning method for inlet water of a once-through boiler separator based on the dynamic fusion of roof temperature, feedwater temperature, and separator pressure as described in claim 1, characterized in that, The water supply flow rate G 给水 and main steam flow rate G 蒸汽 Used to verify the working fluid mass balance, when the feedwater flow rate and the main steam flow rate are dynamically unbalanced, the separator inlet water status is judged in conjunction with the risk index.

8. The intelligent early warning method for inlet water of a once-through boiler separator based on the dynamic fusion of roof temperature, feedwater temperature, and separator pressure as described in claim 1, characterized in that, It also includes a feedback optimization mechanism, which uses historical operating data to optimize the dynamic enthalpy calculation model. Value and operating condition adaptive coefficient , Optimize and adjust.

9. The intelligent early warning method for inlet water of a once-through boiler separator based on the dynamic fusion of roof temperature, feedwater temperature, and separator pressure as described in claim 1, characterized in that, The method is implemented through a dedicated algorithm module deployed in the boiler DCS system. This module includes a data acquisition unit, a dynamic enthalpy calculation unit, a risk index assessment unit, and an early warning control unit.

10. The intelligent early warning method for inlet water of a once-through boiler separator based on the dynamic fusion of roof temperature, feedwater temperature, and separator pressure as described in claim 9, characterized in that, The data acquisition unit uses sensors including: a K-type thermocouple for measuring the temperature of the roof outlet header, a Pt100 resistance thermometer for measuring the feedwater temperature at the economizer inlet, a differential pressure transmitter for measuring the pressure of the separator, and an electromagnetic flowmeter for measuring the feedwater flow rate and the main steam flow rate.

Images