Intelligent once-through boiler separator water inlet early warning method based on dynamic fusion of ceiling temperature, feed water temperature and separator pressure

Abstract

The invention discloses a once-through boiler separator water inlet intelligent early warning method based on dynamic fusion of ceiling temperature, feed water temperature and separator pressure, and belongs to the field of thermal power plant unit once-through boiler operation control. According to the method, parameters such as the ceiling temperature, the economizer feed water temperature, the separator pressure change rate, the feed water flow and the steam flow are collected in real time, a dynamic enthalpy value calculation model is built to solve the separator inlet working medium enthalpy, and a water inlet risk index evaluation model is built. Setting a working condition self-adaptive coefficient according to different loads, and when the risk index absolute value is greater than or equal to 50, triggering an alarm to prompt to increase the fuel quantity and reduce the feed water flow. According to the method, the problem of misjudgment caused by excessive dependence of false water level compensation on the pressure change rate under the deep adjustment working condition is solved, the water inlet risk identification precision of the separator is improved, the early warning response time is advanced by 10-15 seconds, misoperation under the deep adjustment working condition can be effectively avoided, and the method is suitable for the deep peak regulation working condition of the supercritical / ultra-supercritical once-through boiler.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal power generation unit operation control, and in particular to an intelligent early warning method for water inflow into a once-through boiler separator based on dynamic fusion of ceiling temperature, feed water temperature and separator pressure. Background Art

[0002] In the operation of supercritical / ultra-supercritical once-through boilers, the intermediate point superheat and the separator water level are the key basis for regulating the water supply. The existing technology mainly relies on the pressure change rate compensation mechanism to solve the false water level problem. Its core logic is , but this mechanism has significant flaws: Single parameter dependence: compensation is based only on the pressure change rate, which cannot respond to key interference factors such as combustion disturbances (such as sudden changes in ceiling temperature) and sudden drops in feed water temperature; Failure of deep adjustment conditions: At low load (<300MW), the pressure fluctuation amplitude is large and the compensation coefficient k cannot be adaptively adjusted, resulting in insufficient compensation; High risk of misjudgment: When a sudden pressure rise and water seepage in the separator occur simultaneously, it is easy for operators to reduce the feed water excessively, causing the feed water flow rate to fall below the boiler MFT protection value and cause the unit to trip. Summary of the Invention

[0003] In response to the shortcomings of the existing technology, the present invention provides an intelligent early warning method for water inlet of a direct current boiler separator based on the dynamic fusion of ceiling temperature, feed water temperature and separator pressure, so as to solve the problems of low accuracy and easy misjudgment of separator water inlet warning under deep adjustment conditions in the existing technology.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: An intelligent early warning method for water inflow into a once-through boiler separator based on dynamic fusion of ceiling temperature, feed water temperature, and separator pressure includes the following steps: Real-time collection of multi-source parameters: collecting the ceiling outlet header temperature T 顶棚 , used to reflect the evaporation section extension caused by combustion disturbance, economizer inlet feed water temperature T 给水 , as the initial thermodynamic state benchmark of the working fluid, the separator pressure , water flow G 给水 And main steam flow G 蒸汽 , and the separator pressure change rate is obtained by differential calculation; Dynamic enthalpy calculation model construction: through the formula Solve the separator inlet working medium enthalpy in real time, where: is the specific heat capacity of the working fluid at constant pressure, which is 4.18 kJ / (kg·℃). is the saturated water enthalpy corresponding to the feed water temperature, is the correction coefficient of pressure change rate, the value range is 0.5-1.5kJ·s / (kg·MPa), which is used to compensate the heat absorption hysteresis effect caused by pressure mutation; Real-time calculation of water inlet risk index: through the formula Calculate the risk index, wherein, is the saturated water enthalpy value under the current separator pressure, , is the working condition adaptive coefficient; Threshold trigger logic and risk grading warning: according to the absolute value of risk index R, trigger different levels of warning, and perform corresponding control actions.

[0005] Further, in the multi-source parameter real-time acquisition step, the ceiling outlet header temperature is used to reflect the evaporation section extension caused by combustion disturbance, the coal economizer inlet feedwater temperature is used as the initial thermodynamic state benchmark of the working medium, and the separator pressure change rate is obtained by differential calculation through the pressure sensor, and the sampling period is 0.5 seconds.

[0006] Further, the dynamic enthalpy value calculation model construction step includes: Basic enthalpy value calculation: , is the static theoretical enthalpy value when pressure fluctuation is ignored; Pressure change rate dynamic correction: , The value range of is 0.5-1.5KJ·s / (kg·Mpa), which is determined by experimental calibration.

[0007] Further, the working condition adaptive coefficient , According to the dynamic adjustment of unit load: When the unit load is greater than or equal to 300MW, The value is 0.5-0.8, The value is 0.1-0.15; When the unit load is less than 300MW, The value is 0.9-1.2, The value is 0.2-0.3.

[0008] Further, in the threshold trigger logic and risk grading warning step, the risk level division and response action are as follows: Low risk: when <3, no active intervention, only record parameters; Medium risk: when 3< R <50, activate audible and visual alarm and prompt to reduce feedwater flow; High risk: when <50, activate audible and visual alarm and prompt to reduce feedwater flow; When the value is greater than 50, interlocking control is triggered, the feed water flow is reduced by more than 10% of the rated flow, and the fuel amount is increased by more than 5%.

[0009] Further, the and are obtained by querying the IAPWS-97 water vapor table, wherein the feed water temperature at the inlet of the economizer is queried, and the current separator pressure is queried.

[0010] Further, the feed water flow G 给水 and the main steam flow G 蒸汽 are used to verify the working medium mass balance, and when the dynamic imbalance of the feed water flow and the main steam flow occurs, the risk index is combined to judge the water inlet state of the separator.

[0011] Further, the feedback optimization mechanism is further included, and the value and the working condition adaptive coefficient , in the dynamic enthalpy calculation model are optimized and adjusted through historical operation data.

[0012] Further, the method is implemented by deploying a special algorithm module in the DCS system of the boiler, and the module includes a data acquisition unit, a dynamic enthalpy calculation unit, a risk index evaluation unit and a pre-warning control unit.

[0013] Further, the sensors used by the data acquisition unit include a K-type thermocouple for measuring the temperature of the ceiling outlet header, a Pt100 thermal resistance for measuring the feed water temperature at the inlet of the economizer, a differential pressure pressure transmitter for measuring the separator pressure, and an electromagnetic flowmeter for measuring the feed water flow and the main steam flow.

[0014] Compared with the prior art, the present application has the following beneficial effects: 1. By fusing the ceiling temperature, the feed water temperature and the pressure change rate multi-parameters, the dynamic enthalpy model and the risk index evaluation model are constructed, the real water level and the false water level are effectively distinguished, the misjudgment caused by a single pressure parameter is avoided, and the pre-warning accuracy is significantly improved.

[0015] 2. Compared with the prior art, the pre-warning response time is advanced, and more sufficient adjustment time is provided for the operating personnel.

[0016] 3. By dynamically adjusting the working condition adaptive coefficient , , good pre-warning effect can still be maintained under the deep regulation working condition of 30% rated load (<300 MW).

[0017] 4. By hierarchical early warning and interlocking control, over-adjustment of feedwater flow by operation personnel due to misjudgment is avoided, and accidents such as unit trip are prevented, thereby reducing the risk of misoperation; 5. It is verified by practice that annual maintenance cost is reduced, mainly due to the reduction of unplanned shutdown events. BRIEF DESCRIPTION OF DRAWINGS

[0018] The application will be further described below in combination with the drawings and embodiments: Figure 1 The dynamic enthalpy calculation flowchart for the embodiment of the application; Figure 2 The intelligent early warning method flowchart for the embodiment of the application. DETAILED DESCRIPTION

[0019] The technical solutions in the application will be further described below in combination with the drawings and embodiments.

[0020] The application is based on field experiment analysis of the causes of the problems, specifically: Boiler overview: The 650MW supercritical unit boiler of the 4th boiler of the second phase of a power plant is a supercritical parameter composite variable pressure once-through boiler of the Dongfang Boiler Factory, and the model is DG1950 / 25.4-Ⅱ5. The boiler is provided with an expansion center point, and through the guidance and constraint in the horizontal and vertical directions, three-dimensional expansion is realized with the height of the boiler as the center, and the cracking of the boiler roof and the wall and the deformation of the heating surface are prevented.

[0021] Test process: The 4th unit carried out a deep regulation condition separator false water level characteristic test in March 2025, and the target load was set to 180MW. The test focused on the 30% rated load (180MW) interval, and the whole process was operated in the turbine following control mode, and the 361 valve was not started and stopped and the heating surface temperature was within the safety threshold. The specific implementation of the test is as follows: Time 09:38, the unit load is reduced to 180MW, and the #4 D coal mill shutdown operation is performed to maintain the AC mill running state; Time 09:40, the water phase of the #4 furnace separator changes, and the monitoring data shows that the vertical water cooling wall outlet header feedwater temperature is 322.1℃, the coal economizer inlet feedwater pressure is 10.8MPa, the steam-water separator metal outer wall temperature is 329℃, the separator water storage tank outlet pressure is 10.64MPa, the ceiling outlet header temperature is 324.2℃, the intermediate point superheat is 5.7℃, the feedwater main pipe flow is 483t / h, the main steam flow is 466t / h, the feedwater main pipe temperature is 221.9℃, and the steam-water separator initial water level is 0m. When the separator water level shows an upward trend, the operator immediately adjusts the feedwater flow; Time 09:42, unit load 174MW, during parameters: separator water level 15m, intermediate point superheat 4.7℃, feedwater flow 410t / h, separator pressure 10.75MPa, steam-water separator metal outer wall temperature 328℃, ceiling outlet header temperature 324℃; Time 09:42:48, load rises to 179MW, each system parameter: vertical water cooling wall outlet header feedwater temperature 322.5℃, coal economizer inlet feedwater pressure 10.87MPa, steam-water separator metal outer wall temperature 327℃, separator water storage tank outlet pressure 10.8MPa, ceiling outlet header temperature 324.5℃, intermediate point superheat 5.0℃, feedwater main pipe flow 342t / h, main steam flow 472t / h, feedwater main pipe temperature 217℃, steam-water separator water level reaches 25m full value.

[0022] The whole process monitoring shows that the separator pressure presents a continuous rising characteristic.

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

[0024] From the whole test process, it is found that: 1. Separator pressure parameter evolution: the pressure is 10.75MPa at 09:42, and rises to 10.87MPa at 09:42:48, with a pressure change rate of 0.0025MPa / s (2.5kPa / s). Steam density change analysis: at a pressure of 10.8MPa, the saturated steam density is 65.3kg / m³; when the pressure rises to 10.87MPa, the density increases to 67.1kg / m³, with an increase of 2.7%. This density change causes the steam in the separator to be compressed, thereby causing the water level measurement value to be false high.

[0025] 2. Intermediate point superheat parameter analysis: the superheat is 4.7℃ at 09:42, close to the saturation temperature of 317.5℃ corresponding to 10.75MPa, indicating that the outlet working medium of the evaporation section is in a wet steam state. Ceiling temperature and separator temperature comparison: the saturated steam temperature corresponding to 10.8MPa is 318℃, and the actual measured ceiling outlet temperature is 324℃, with a superheat of only 6℃, which has already exceeded the saturation temperature value corresponding to the current pressure.

[0026] 3. The dynamic relationship between feedwater flow and steam flow shows that the real separator water level should show a downward trend, but the monitoring system shows an abnormal rise in water level at this time, which is determined to be a false water level phenomenon.

[0027] Through the whole process of tracing analysis, the separator abnormal water phenomenon is mainly caused by the following reasons: The core logic of the separator false water level compensation mechanism is based on the pressure change rate ) water level measurement (H 测量 ) dynamic correction is implemented: , wherein the compensation coefficient k is determined by experiment calibration, and the conventional operation interval is 0.5-2 mm·min / MPa.

[0028] The compensation mechanism aims to eliminate the instantaneous volume expansion / contraction effect of the working medium caused by the sudden change of pressure, and the typical false water level rise phenomenon caused by the increase of steam specific volume when the pressure suddenly drops. It should be particularly pointed out that the existing compensation mechanism has inherent limitations: the compensation formula is only applicable to the correction of false water level caused by sudden pressure change, and the correction efficiency is significantly reduced in deep peak shaving load reduction conditions; the compensation coefficient may increase significantly in deep load reduction conditions. In addition, the existing pressure change rate compensation mechanism has no correction ability for the following conditions: real water level rise caused by working medium mass change, typical performance is actual water level rise accompanied by superheat degree reduction; evaporation section extension caused by sudden change of feedwater temperature; when the separator pressure mutation is coupled with combustion disturbance (ceiling temperature change) or feedwater temperature fluctuation, the compensation mechanism can only partially offset the pressure influence; heat transfer deviation caused by abnormal combustion regulation, for example, during load reduction, if the ceiling temperature abnormally rises due to inaccurate combustion regulation, it will cause the evaporation section to move backward and produce significant water level fluctuation.

[0029] Specific mechanism explanation: when the load changes sharply, the pressure of the separator will fluctuate sharply, which will cause the water / steam density to change suddenly, and then induce water level expansion or contraction effect; the dynamic imbalance between steam flow and feedwater flow is caused by the lag of fuel quantity or feedwater quantity regulation, which eventually leads to abnormal phase change rate of the working medium. Therefore, the present application is used to solve the problem of separator water inlet.

[0030] Embodiment 1 As shown in Figure 1 , the embodiment of the present application proposes a direct-flow boiler separator water inlet intelligent early warning method based on dynamic fusion of ceiling temperature, feedwater temperature and separator pressure, which comprises: 1. Equipment selection and deployment: Ceiling outlet header temperature measurement: K-type thermocouple, model WRN-130, measurement range 0-1200℃, accuracy ±1.5℃; Economizer inlet feedwater temperature measurement: Pt100 thermal resistance, model WZP-230, measurement range -200-650℃, accuracy ±0.5℃; Separator pressure measurement: differential pressure pressure transmitter, model Rosemount3051CD, measurement range 0-40MPa, accuracy ±0.075%; Feedwater flow and main steam flow measurement: electromagnetic flowmeter, model E+HPromagW400, measurement accuracy ±0.5%; Data processing unit: 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: Under the condition of 09:42:48, the acquired parameters are as follows: Ceiling temperature =324.5℃; Feedwater temperature =217℃; Separator pressure p=10.87MPa; Feedwater flow G 给水 =342t / h; Main steam flow 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. Dynamic enthalpy calculation: Basic enthalpy calculation: =4.18×(324.5-217)+ , 217℃, IAPWS-97 table =923kJ / kg, so =4.18×107.5+923=1352kJ / kg; Dynamic correction: Take the experimental calibration value 1.2kJ·s / (kg·MPa), then Δh=1.2×0.12=0.144kJ / kg; Final inlet enthalpy: =1352+0.144=1352.144kJ / kg.

[0033] 4. Inlet water risk index calculation: IAPWS-97 table shows that the saturated water enthalpy at 10.87MPa is =1408kJ / kg; Unit load 179MW<300MW, so =0.9, =0.2; Risk index: =0.9×(1352.144-1408)+0.2×0.12=-50.29, =50.29≥50, triggering high-risk early warning.

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

[0035] Example 2 Early warning method verification under normal load working condition: 1. Working condition parameters: unit load 350 MW ≥ 300 MW, the collected parameters are as follows: = 350℃, = 250℃, p = 16 MPa, = 0.05 MPa / s, G 给水 = 800 t / h, G 蒸汽 = 790 t / h; 2. Dynamic enthalpy value calculation: (250℃) = 1048 kJ / kg, = 4.18*(350-250) + 1048 = 418 + 1048 = 1466 kJ / kg; = 0.8, Δh = 0.8*0.05 = 0.05 kJ / kg, = 1466 + 0.04 = 1466.04 kJ / kg; 3. Risk index calculation: (16 MPa) = 1628 kJ / kg, = 0.6, = 0.12; = 0.6*(1466.04-1628) + 0.12*0.05 = -97.176 + 0.006 = -97.17; = 97.17 ≥ 50, trigger high-risk early warning, the system automatically reduces the feed water flow by 80 t / h and increases the fuel quantity by 5%, effectively avoiding the separator water inlet.

[0036] The core principle of the separator water inlet early warning realized by the multi-parameter dynamic fusion of the application is as follows: Ceiling temperature dynamic correction combustion disturbance: the ceiling temperature reflects the combustion intensity and the evaporation section position, when the combustion adjustment is abnormally caused to move backward, the deviation of the ceiling temperature and the saturation temperature can directly reflect the working medium superheat degree change, which makes up for the defect that single pressure compensation cannot respond to combustion disturbance; The feedwater temperature calibrates the initial enthalpy value of the working medium. The feedwater temperature is used as the reference of the initial thermodynamic state of the working medium. The corresponding saturated water enthalpy value is obtained by IAPWS-97 algorithm, which provides an accurate starting point for dynamic enthalpy calculation and eliminates the interference of sudden changes in feedwater temperature on the early warning results. The pressure change rate accurately compensates for the false water level. In combination with the working condition adaptive coefficient, the compensation weight of the pressure change rate on the false water level is enhanced in the deep regulation condition, solving the problem of insufficient compensation of the traditional compensation mechanism at low load. Risk index quantification decision: The risk index is calculated by weighting the supercooling degree of the working medium and the pressure change rate, and a quantitative early warning threshold is established to realize the upgrade from "qualitative judgment" to "quantitative decision", significantly improving the reliability and operability of early warning.

[0037] When the separator is filled with water, the water inflow risk index evaluation method can be used to dynamically adjust the fuel supply system and the feedwater control logic, thereby effectively avoiding the risk of misoperation caused by blindness. According to the actual working condition verification, the application effect of this method is remarkable: for the recorded 09:42:48 separator full water working condition event, the mathematical model constructed by this research is used for verification analysis: the system successfully captures the R=2.3 characteristic parameter anomaly at 09:42:00 (48 seconds in advance), which can accurately identify the potential cause of the separator full water in the deep regulation condition, and implement control strategy optimization, effectively preventing the operation error caused by the full liquid level of the container.

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

[0039] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the purpose and scope of the present application, which should be covered by the claims of the present application.

Claims

1. An intelligent early warning method for water inflow into a once-through boiler separator based on dynamic fusion of ceiling temperature, feed water temperature and separator pressure, characterized in that: The following steps are involved: Real-time collection of multi-source parameters: collecting the ceiling outlet header temperature T 顶棚 , economizer inlet feed water temperature T 给水 , separator pressure , water flow G 给水 And main steam flow G 蒸汽 , and the separator pressure change rate is obtained by differential calculation; Dynamic enthalpy calculation model construction: through the formula Solve the separator inlet working medium enthalpy in real time, where: is the specific heat capacity of the working fluid at constant pressure, is the saturated water enthalpy corresponding to the feed water temperature, is the pressure change rate correction coefficient; Real-time calculation of water ingress risk index: through the formula Calculate the risk index, where is the saturated water enthalpy at the current separator pressure, 、 is the working condition adaptive coefficient; Threshold trigger logic and risk classification warning: trigger different levels of warnings according to the absolute value of the risk index R, and perform corresponding control actions.

2. The intelligent early warning method for water inflow of a once-through boiler separator based on dynamic fusion of ceiling temperature, feed water temperature and separator pressure according to claim 1, characterized in that: In the multi-source parameter real-time acquisition step, the ceiling outlet header temperature is used to reflect the extension of the evaporation section caused by combustion disturbances, the economizer inlet feed water temperature is used as the initial thermodynamic state benchmark of the working medium, and the separator pressure change rate is obtained by differential calculation of the pressure sensor. The sampling period is 0.5 seconds.

3. The intelligent early warning method for water inflow of a once-through boiler separator based on dynamic fusion of ceiling temperature, feed water temperature and separator pressure according to claim 1, characterized in that: The dynamic enthalpy calculation model construction step includes: Basic enthalpy calculation: ,in is the static theoretical enthalpy when pressure fluctuations are ignored; Dynamic correction of pressure change rate: ,in The value range is 0.5-1.5KJ·s / (kg·Mpa), which is determined by experimental calibration.

4. The intelligent early warning method for water inflow of a once-through boiler separator based on dynamic fusion of ceiling temperature, feed water temperature and separator pressure according to claim 1, characterized in that: The working condition adaptive coefficient 、 Dynamic adjustment based on unit load: When the unit load is ≥300MW, The value is 0.5-0.8, The value range is 0.1-0.15; When the unit load is less than 300MW, The value range is 0.9-1.2, The value is 0.2-0.

3.

5. The intelligent early warning method for water inflow of a once-through boiler separator based on dynamic fusion of ceiling temperature, feed water temperature and separator pressure according to claim 1, characterized in that: In the threshold trigger logic and risk classification warning steps, the risk level classification and response actions are as follows: Low risk: When When <3, there is no active intervention and only parameters are recorded; Medium risk: When 3< When the temperature is less than 50, the sound and light alarm will be activated and the user will be prompted to reduce the water flow rate. High risk: When When it is greater than 50, the interlock control is triggered, the feed water flow is reduced by ≥10% of the rated flow, and the fuel amount is increased by ≥5%.

6. The intelligent early warning method for water inflow of a once-through boiler separator based on dynamic fusion of ceiling temperature, feed water temperature and separator pressure according to claim 1, characterized in that: described and All are obtained through the IAPWS-97 water vapor table, where According to the economizer inlet water temperature query, Query based on current separator pressure.

7. The intelligent early warning method for water inflow of a once-through boiler separator based on dynamic fusion of ceiling temperature, feed water temperature and separator pressure according to claim 1, characterized in that: The water flow rate G 给水 And main steam flow G 蒸汽 Used to verify the mass balance of the working fluid. When there is a dynamic imbalance between the feed water flow and the main steam flow, the water inlet status of the separator is judged in combination with the risk index.

8. The intelligent early warning method for water inflow of a once-through boiler separator based on dynamic fusion of ceiling temperature, feed water temperature and separator pressure according to claim 1, characterized in that: It also includes a feedback optimization mechanism, which uses historical operating data to calculate the dynamic enthalpy value in the model. Value and working condition adaptive coefficient 、 Make optimization adjustments.

9. The intelligent early warning method for water inflow into a once-through boiler separator based on dynamic fusion of ceiling temperature, feed water temperature and separator pressure according to claim 1, characterized in that: The method is implemented by a dedicated algorithm module deployed in the boiler DCS system, which includes a data acquisition unit, a dynamic enthalpy value calculation unit, a risk index evaluation unit and an early warning control unit.

10. The intelligent early warning method for water inflow into a once-through boiler separator based on dynamic fusion of ceiling temperature, feed water temperature and separator pressure according to claim 9, characterized in that: The sensors used in the data acquisition unit include: a K-type thermocouple for measuring the temperature of the ceiling outlet header, a Pt100 thermal resistor for measuring the economizer inlet feed water temperature, a differential pressure transmitter for measuring the separator pressure, and an electromagnetic flowmeter for measuring the feed water flow and main steam flow.

Images