Method and system for controlling sealing water of water feeding pump of thermal power plant

Abstract

The invention discloses a thermal power plant feed pump sealing water control method and system, and belongs to the technical field of thermal power generation. The method comprises the steps that according to obtained sealing water data, the sealing water inlet and return water temperature difference, the sealing water inlet and return water pressure difference, the sealing water inlet and return water flow difference and the water feeding pump leakage water flow are calculated; when the sealing water inlet and return water temperature difference is smaller than the first preset temperature, the sealing water outlet temperature is smaller than the second preset temperature, the sealing water inlet unloading water pressure difference is larger than the preset pressure, the sealing water inlet and return water flow difference is larger than the preset flow, and the water feeding pump leakage water flow is larger than the preset flow, the opening degree of sealing water is adjusted to be smaller; when the sealing water inlet and return water temperature difference is not smaller than the first preset temperature, the sealing water outlet temperature is not smaller than the second preset temperature, the sealing water inlet unloading water pressure difference is not larger than the preset pressure, the sealing water inlet and return water flow difference is not larger than the preset flow or the water feeding pump leakage water flow is not larger than the preset flow, the opening degree of sealing water is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal power generation, and in particular to a control method and system for the sealing water of a feed water pump in a thermal power plant. Background Art

[0002] As a key device in the thermal power generation system, the operating state of the feed water pump directly affects the safety and efficiency of the unit. The feed water pump sealing water system is an important part to ensure the normal operation of the feed water pump. Generally, there are two forms of feed water pump sealing, labyrinth seal and mechanical seal. The mechanical seal relies on the contact surface of the stationary and rotating rings to remain in contact under the action of spring force and fluid pressure to form a sealing end face, and the fluid leakage is prevented through the liquid film between the end faces. The labyrinth seal forms a series of throttling gaps and expansion cavities between teeth by setting multiple annular sealing teeth around the rotating shaft. When the sealed medium passes through these tortuous labyrinth gaps, a throttling effect is generated, thereby achieving the purpose of leakage prevention.

[0003] The feed water for the feed water pump sealing water is generally taken from the outlet water of the condensate pump, and the sealing water flow rate and pressure are controlled by a regulating valve. There are two return paths for the sealing water. The first path is the unloading water, which is a mixture of the leakage water and the sealing water of the feed water pump, and enters the inlet of the booster pump together. The second path is the condensate return to the condenser.

[0004] If the opening of the sealing water regulating valve is small, it will lead to insufficient sealing water flow rate. Insufficient mechanical seal water flow rate cannot form an effective water film on the sealing surface and cannot play a good sealing role. Insufficient labyrinth seal water flow rate cannot form sufficient pressure and flow rate between the sealing teeth and the rotating shaft. In short, a small opening of the sealing regulating valve will lead to a poor sealing effect. The leakage of high-temperature and high-pressure feed water at the shaft end of the feed water pump will not only cause the loss of working medium, but also cause local overheating of the equipment, affecting the normal operation of the equipment. If the opening of the regulating valve is large, a large sealing water flow rate can enhance the sealing effect, but the sealing water with too high pressure may enter the pump body, resulting in a decrease in the outlet temperature of the feed water pump and an increase in the energy consumption of the unit. In addition, when the opening of the regulating valve is too large, the sealing water flow rate will increase significantly, causing the feed water pump sealing water to enter the inlet of the booster pump. According to the equivalent enthalpy drop theory, it is equivalent to the condensate directly entering the high-pressure heater inlet without passing through the shaft seal heater, low-pressure heater and deaerator, resulting in an increase in the system energy consumption.

[0005] Therefore, whether the opening of the feed water pump sealing water regulating valve is too large or too small will cause an increase in the energy consumption of the unit. The best opening of the sealing water regulating valve is to ensure the smallest flow rate of the sealing water entering the system through the unloading water on the premise of ensuring the safe operation of the feed water pump without leakage of the feed water.

[0006] At present, the existing sealed water control system mainly installs a differential pressure controller on the sealed water regulating valve. Relying on the differential pressure controller, the pressure difference between the sealed water pressure and the unloading water pressure is maintained at 0.1 MPa. Temperature transmitters are set in the sealed water inlet and return pipes. By adjusting the opening of the sealed water inlet regulating valve, it is ensured that the temperature difference between the sealed water inlet and return pipes is less than 35 °C and the return water temperature is less than 80 °C.

[0007] However, these systems and control methods have many limitations. Only indirect parameter control can be used to adjust the opening of the feed pump sealed water regulating valve, and the existing measuring devices are difficult to adapt to the complex and changeable working conditions during the thermal power generation process. In addition, as the equipment ages, the performance of the sealing system will gradually decline, and the existing measuring devices cannot accurately capture the changes in the sealed water flow caused by these factors, making it difficult to achieve precise control of the sealed water and unable to keep the sealed water system operating at the lowest energy consumption state. Summary of the Invention

[0008] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a control method and system for the sealed water of the feed pump in a thermal power plant, which can effectively improve the operating efficiency of the feed pump, reduce system energy consumption, and ensure the safe and stable operation of the equipment.

[0009] To achieve the above object, the present invention is implemented by the following technical solutions: On the one hand, the present invention provides a control method for the sealed water of the feed pump in a thermal power plant, including: According to the obtained sealed water data, calculate the temperature difference between the sealed water inlet and return water, the pressure difference between the sealed water inlet and unloading water, the flow difference between the sealed water inlet and return water, and the leakage water flow of the feed pump respectively; the sealed water data includes the sealed water inlet temperature, the sealed water inlet pressure, the sealed water inlet flow, the sealed water outlet temperature, the sealed water outlet flow, the unloading water pressure, and the unloading water flow; In response to the temperature difference between the sealed water inlet and return water being less than the first preset temperature, the sealed water outlet temperature being less than the second preset temperature, the pressure difference between the sealed water inlet and unloading water being greater than the preset pressure, the flow difference between the sealed water inlet and return water being greater than the preset flow, and the leakage water flow of the feed pump being greater than the preset flow, the sealed water meets the sealing condition, and the opening of the sealed water is adjusted smaller within the preset optimal opening range to obtain the optimal opening of the sealed water; In response to the temperature difference between the sealed water inlet and return water being not less than the first preset temperature, the sealed water outlet temperature being not less than the second preset temperature, the pressure difference between the sealed water inlet and unloading water being not greater than the preset pressure, the flow difference between the sealed water inlet and return water being not greater than the preset flow, or the leakage water flow of the feed pump being not greater than the preset flow, the sealed water does not meet the sealing condition, and the opening of the sealed water is adjusted larger within the preset optimal opening range to obtain the optimal opening of the sealed water.

[0010] Optionally, based on the obtained sealed water data, calculate the temperature difference between the inlet and return sealed water, the pressure difference between the inlet and unloading of the sealed water, the flow difference between the inlet and return of the sealed water, and the leakage water flow of the feed pump, including: △T = T2 - T1; △P = P1 - P3; △Q1 = Q1 - Q2; △Q2 = Q2 + Q3 - Q1; Wherein, △T represents the temperature difference between the inlet and return of the sealed water; △P represents the pressure difference between the inlet and unloading of the sealed water; △Q1 represents the flow difference between the inlet and return of the sealed water; △Q2 represents the leakage water flow of the feed pump; T1 represents the inlet temperature of the sealed water; P1 represents the inlet pressure of the sealed water; Q1 represents the inlet flow of the sealed water; T2 represents the outlet temperature of the sealed water; Q2 represents the outlet flow of the sealed water; P3 represents the unloading water pressure; Q3 represents the unloading water flow.

[0011] Optionally, the acquisition of the preset optimal opening range includes: Record the optimal opening of the sealed water when the feed pump operates safely under different unit loads and main steam pressures; Take the range formed by the optimal openings of all the sealed water as the optimal opening range of the sealed water.

[0012] Optionally, reducing the opening of the sealed water within the preset optimal opening range to obtain the optimal opening of the sealed water includes: Gradually reduce the opening of the sealed water within the preset optimal opening range, obtain the sealed water working conditions corresponding to each opening under the same unit load and main steam pressure conditions until the opening of the sealed water is less than the preset opening or the sealed water does not meet the sealing conditions, and take the opening corresponding to the optimal sealed water working condition as the optimal opening of the sealed water.

[0013] Optionally, the acquisition of the optimal sealed water working condition under the same unit load and main steam pressure conditions includes: If the sealed water is a mechanical seal, select the working condition with the sealed water inlet and return flow difference closest to zero under the same unit load and main steam pressure conditions as the optimal sealed water working condition; If the sealed water is a labyrinth seal, select the working condition with the smallest sealed water inlet and return flow difference under the same unit load and main steam pressure conditions as the optimal sealed water working condition.

[0014] Optionally, increasing the opening of the sealed water within the preset optimal opening range to obtain the optimal opening of the sealed water includes: Gradually increase the opening of the sealed water within the preset optimal opening range until the sealed water flow meets the mechanical seal or labyrinth seal, and obtain the optimal opening of the sealed water.

[0015] On the other hand, the present invention also provides a sealing water control system for a feed water pump in a thermal power plant, which adjusts the opening of the sealing water by using the control method described in the first aspect. The system includes: Flow meters are respectively installed at the sealing water inlet, the sealing water return port, and the unloading water port of the sealing water control system for the feed water pump.

[0016] Optionally, the flow meter is a multi-channel ultrasonic flow meter.

[0017] Optionally, the range of the multi-channel ultrasonic flow meter is [0, 200 t / h], the measurement error is within [-0.5%, +0.5%], the applicable temperature range is [-30°C, 300°C], and the applicable pipe diameter range is [50 mm, 3000 mm].

[0018] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: 1. By obtaining the sealing water data, the present invention calculates the temperature difference between the inlet and return of the sealing water, the pressure difference between the inlet and unloading of the sealing water, the flow difference between the inlet and return of the sealing water, and the leakage water flow of the feed water pump, and judges whether the feed water inside the feed water pump leaks to the shaft end and whether the sealing water enters the inside of the feed water pump to judge the sealing effect. It can achieve accurate measurement of the sealing water flow and precise control of its dynamic change, ensure that the sealing water system of the feed water pump is always in a safe operating state with the lowest energy consumption, effectively improve the operating efficiency of the feed water pump, and reduce system energy consumption. 2. The present invention uses a multi-channel ultrasonic flow meter for flow measurement. Compared with the commonly used differential pressure flow meter, the multi-channel ultrasonic flow meter generally has the advantage of a large range ratio, and the range ratio can generally reach 100:1 or even higher, and can adapt to different measurement requirements from tiny flow to super-large flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The figure shows a schematic flow chart of the sealing water control method for a feed water pump in a thermal power plant according to the present invention in an embodiment. Figure 2 The figure shows a schematic structural diagram of the sealing water control system for a feed water pump in a thermal power plant according to the present invention in an embodiment.

[0020] In the figure: 1. Condenser; 2. Condensate pump; 3. Feed water pump; 4. Booster pump; 5. Pneumatic regulating valve for sealing water; 6. First shaft end seal of the feed water pump; 7. Second shaft end seal of the feed water pump; 8. Differential pressure controller for the sealing water regulating valve; 9. Ultrasonic flow meter at the sealing water inlet; 10. Temperature transmitter at the sealing water inlet; 11. Pressure transmitter at the sealing water inlet; 12. Ultrasonic flow meter for the return water of the unloading water; 13. Pressure transmitter for the unloading water; 14. Temperature transmitter for the return water of the sealing water; 15. Ultrasonic flow meter for the return water of the sealing water. DETAILED DESCRIPTION OF THE INVENTION

[0021] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. Without conflict, the technical features in the embodiments of the present invention and the embodiments can be combined with each other.

[0022] The term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " generally represents an "or" relationship between the associated objects before and after.

[0023] Embodiment 1

[0024] As Figure 1 shown, this embodiment introduces a control method for the sealing water of the feed water pump in a thermal power plant, including the following steps: Step 1: According to experience or preliminary debugging, input the initial valve position of the regulating valve, and obtain the sealing water data, that is, real-time monitor the sealing water inlet temperature T1, the sealing water inlet pressure P1, the sealing water inlet flow rate Q1, the sealing water outlet temperature T2, the sealing water outlet flow rate Q2, the unloading water pressure P3, and the unloading water flow rate Q3.

[0025] Step 2: According to the obtained sealing water data, calculate the temperature difference between the inlet and return water of the sealing water, the pressure difference between the inlet and unloading water of the sealing water, the flow rate difference between the inlet and return water of the sealing water, and the leakage water flow rate of the feed water pump, specifically: △T = T2 - T1; △P = P1 - P3; △Q1 = Q1 - Q2; △Q2 = Q2 + Q3 - Q1; Among them, △T represents the temperature difference between the inlet and return water of the sealing water, reflecting the temperature difference between the inlet and return water of the sealing water. △T < 35°C and T2 < 80°C are the safety thresholds for the sealing water control of the feed water pump 3; △P represents the pressure difference between the inlet and unloading water of the sealing water, reflecting the difference between the sealing water pressure and the unloading water pressure. △P > 0.06 MPa indicates that the unloading water of the feed water pump 3 can flow normally; △Q1 represents the flow rate difference between the inlet and return water of the sealing water, used to judge whether the internal feed water of the feed water pump 3 leaks to the shaft end. When △Q1 > 0, it indicates that the internal feed water of the feed water pump 3 does not leak to the shaft end; △Q2 represents the leakage water flow rate of the feed water pump, used to judge whether the sealing water enters the inside of the feed water pump 3. When △Q2 > 0, it indicates that the sealing water does not enter the inside of the feed water pump 3; Step 3: Record the optimal opening of the sealing water when the feed water pump operates safely under different unit loads and main steam pressure conditions; take the range formed by the optimal openings of all the sealing water as the optimal opening range of the sealing water, and adjust the opening of the sealing water within the optimal opening range of the sealing water. In this embodiment, the pneumatic regulating valve 5 of the sealing water is used to adjust the opening of the sealing water. In a specific embodiment, record the optimal opening of the pneumatic regulating valve 5 of the sealing water when the feed water pump operates safely under different unit loads and main steam pressure conditions. After multiple tests and operation verifications, determine the range formed by these optimal openings of the pneumatic regulating valve 5 of the sealing water, which is the optimal opening range of the pneumatic regulating valve 5 of the sealing water, and adjust the opening of the sealing water within the optimal opening range of the pneumatic regulating valve 5 of the sealing water.

[0026] Step 4: In response to the temperature difference △T between the inlet and return water of the sealing water being less than the first preset temperature, the outlet water temperature T2 of the sealing water being less than the second preset temperature, the pressure difference △P between the inlet and unloading water of the sealing water being greater than the preset pressure, the flow rate difference △Q1 between the inlet and return water of the sealing water being greater than the preset flow rate, and the leakage water flow rate △Q2 of the feed water pump being greater than the preset flow rate, when the sealing water meets the sealing condition, gradually reduce the opening of the sealing water within the preset optimal opening range, and obtain the sealing water working conditions corresponding to each opening under the same unit load and main steam pressure conditions until the opening of the sealing water is less than the preset opening or the sealing water does not meet the sealing condition. Take the opening corresponding to the optimal sealing water working condition as the optimal opening of the sealing water; the obtaining of the optimal sealing water working condition under the same unit load and main steam pressure conditions includes: If the sealing water is a mechanical seal, select the working condition with the flow rate difference between the inlet and return water of the sealing water closest to zero under the same unit load and main steam pressure conditions as the optimal sealing water working condition; If the sealing water is a labyrinth seal, select the working condition with the minimum flow rate difference between the inlet and return water of the sealing water under the same unit load and main steam pressure conditions as the optimal sealing water working condition; In a specific embodiment, in response to △T < 35°C, T2 < 80°C, △P > 0.06 MPa, △Q1 > 0 t / h, and △Q2 > 0 t / h, when the sealing water meets the sealing condition, gradually reduce the opening of the pneumatic regulating valve 5 of the sealing water within the preset optimal opening range, and record the opening of the pneumatic regulating valve 5 of the sealing water and the value of △Q1 under the current unit load and main steam pressure conditions until the pneumatic regulating valve 5 of the sealing water is less than the lowest limit opening of 30% or the sealing water can no longer meet the sealing condition. Select the optimal working condition of the pneumatic regulating valve of the sealing water under the same load and main steam pressure conditions as the optimal opening of the pneumatic regulating valve 5 of the sealing water under the current operating condition; if the opening of the sealing water is not less than 30% or the sealing water meets the sealing condition, reduce the opening of the pneumatic regulating valve 5 of the sealing water by 5%, and re-obtain the sealing water data; Among them, when the best operating condition of the sealing water regulating valve is mechanical seal, select the operating condition where ΔQ1 is closest to 0; when the best operating condition of the sealing water regulating valve is labyrinth seal, select the operating condition where ΔQ1 is the smallest.

[0027] Step Five: In response to the temperature difference between the inlet and return of the sealing water being not less than the first preset temperature, the outlet temperature of the sealing water being not less than the second preset temperature, the pressure difference between the inlet and unloading of the sealing water being not greater than the preset pressure, the flow difference between the inlet and return of the sealing water being not greater than the preset flow, or the leakage water flow of the feed pump being not greater than the preset flow, when the sealing water does not meet the sealing condition, gradually increase the opening of the sealing water within the preset optimal opening range until the sealing water flow meets the mechanical seal or labyrinth seal, and obtain the optimal opening of the sealing water. In a specific embodiment, in response to △T≥35°C, T2 ≥80°C, △P≤0.06MPa, △Q1≤0 t / h, and △Q2≤ 0 t / h, when the sealing water does not meet the sealing condition, gradually increase the opening of the pneumatic regulating valve 5 of the sealing water within the preset optimal opening range, increase the opening of the pneumatic regulating valve 5 of the sealing water by 5% and the opening of the pneumatic regulating valve 5 of the sealing water should be less than 100% at most. At the same time, continuously monitor the above sealing water data until the sealing water flow can meet the mechanical seal to form an effective water film or the labyrinth seal can form sufficient pressure and flow between the sealing teeth and the rotating shaft to ensure △T<35°C, T2<80°C, △P>0.06MPa, △Q1>0 t / h, and △Q2>0 t / h; if the opening of the pneumatic regulating valve 5 of the sealing water is above 100%, send an alarm signal and intervene manually.

[0028] Step Six: If the performance of the feed pump sealing water system changes, obtain the sealing water data in real time, and dynamically adjust the optimal opening of the sealing water with reference to Steps One to Five according to the sealing water data. In a specific embodiment, if the performance of the feed pump sealing water system changes with the aging of the equipment, obtain the sealing water data in real time, and the optimal opening of the pneumatic regulating valve 5 of the sealing water can be dynamically adjusted in real time according to the sealing water data, so that the sealing water always maintains the best operating state.

[0029] Embodiment 2

[0030] Based on Embodiment 1, this embodiment introduces a sealing water control system for a feed pump in a thermal power plant, and uses the control method described in Embodiment 1 to adjust the opening of the sealing water. Such as Figure 1As shown in the figure, the system includes a condenser 1, a condensate pump 2, a feed water pump 3, a booster pump 4, a pneumatic control valve 5 for seal water, a first shaft end seal 6 of the feed water pump, a second shaft end seal 7 of the feed water pump, a differential pressure controller 8 for the seal water control valve, an ultrasonic flowmeter 9 for the seal water inlet, a temperature transmitter 10 for the seal water inlet, a pressure transmitter 11 for the seal water inlet, an ultrasonic flowmeter 12 for the return water of the unloading water, a pressure transmitter 13 for the unloading water, a temperature transmitter 14 for the return water of the seal water, and an ultrasonic flowmeter 15 for the return water of the seal water; The outlet of the condenser 1 is connected to the inlet of the condensate pump 2. The outlet of the condensate pump 2 is respectively connected to the first shaft end seal 6 of the feed water pump and the second shaft end seal 7 of the feed water pump. The feed water pump 3 is installed between the first shaft end seal 6 of the feed water pump and the second shaft end seal 7 of the feed water pump. The inlet of the feed water pump 3 is also connected to the outlet of the booster pump 4; Between the condensate pump 2 and the first shaft end seal 6 of the feed water pump and the second shaft end seal 7 of the feed water pump, a pneumatic control valve 5 for seal water, an ultrasonic flowmeter 9 for the seal water inlet, and a temperature transmitter 10 for the seal water inlet are respectively installed. Between the first shaft end seal 6 of the feed water pump and the inlet of the booster pump 4, an ultrasonic flowmeter 12 for the return water of the unloading water and a pressure transmitter 13 for the unloading water are installed. Between the first shaft end seal 6 of the feed water pump and the inlet of the condenser 1, a temperature transmitter 14 for the return water of the seal water and an ultrasonic flowmeter 15 for the return water of the seal water are installed. The differential pressure controller 8 for the seal water control valve is installed on the pneumatic control valve 5 for seal water.

[0031] The seal water inlet is divided into two paths, namely the return water of the seal water and a part of the unloading water; the unloading water includes the seal water and the leakage water of the feed water pump. In this embodiment, ultrasonic flowmeters are respectively installed at the seal water inlet, the seal water return port, and the unloading water port of the seal water control system for the feed water pump.

[0032] The condenser 1 serves as the convergence point of the condensate water in the control system and provides a water source for the subsequent process.

[0033] The condensate pump 2 extracts condensate water from the condenser 1, provides initial power for the seal water system of the feed water pump, and transports the water to the subsequent links.

[0034] The feed water pump 3 is a key device in the thermal power generation system, and its operating state directly affects the safety and efficiency of the unit.

[0035] The booster pump 4 cooperates with the feed water pump 3 to preliminarily pressurize the water and ensure the stable operation of the feed water pump 3.

[0036] The pneumatic control valve 5 for seal water is used to adjust the flow rate and pressure of the seal water and is a key actuator for achieving precise control.

[0037] The first shaft end seal 6 of the feed water pump and the second shaft end seal 7 of the feed water pump prevent the leakage of high-temperature and high-pressure feed water in the feed water pump 3, and there are two forms: labyrinth seal and mechanical seal.

[0038] The differential pressure controller 8 of the sealing water regulating valve assists in controlling the sealing water regulating valve 5, so that a certain differential pressure is maintained between the sealing water pressure and the unloading water pressure.

[0039] Sealing water inlet ultrasonic flowmeter 9: It is used to accurately measure the inlet flow rate Q1 of the sealing water. In this embodiment, a multi-channel ultrasonic flowmeter is adopted. The range of the multi-channel ultrasonic flowmeter is [0, 200 t / h], the measurement error is within [-0.5%, +0.5%], the applicable temperature range is [-30°C, 300°C], and the applicable pipe diameter range is [50 mm, 3000 mm]. Compared with the common differential pressure flowmeter, the multi-channel ultrasonic flowmeter generally has the advantage of a large range ratio, and the range ratio can generally reach 100:1 or even higher, and it can adapt to different measurement requirements from tiny flow rates to extremely large flow rates.

[0040] The sealing water inlet temperature transmitter 10 monitors the inlet temperature T1 of the sealing water in real time.

[0041] The sealing water inlet pressure transmitter 11 measures the inlet pressure P1 of the sealing water.

[0042] The unloading water pressure transmitter 12 monitors the pressure P3 of the unloading water.

[0043] The unloading water return ultrasonic flowmeter 13 measures the flow rate Q3 of the unloading water.

[0044] The sealing water return temperature transmitter 14 monitors the return temperature T2 of the sealing water.

[0045] The sealing water return ultrasonic flowmeter 15 measures the outlet flow rate Q2 of the sealing water.

[0046] The system of this embodiment can judge the sealing effect, accurately control the flow rate and pressure of the sealing water, ensure that the sealing water system of the feed pump is always in a safe operating state with the lowest energy consumption, can effectively improve the operating efficiency of the feed pump, and reduce the system energy consumption.

[0047] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit and scope protected by the claims of the present invention. These all fall within the protection scope of the present invention.

Claims

1. A method for controlling sealing water of a feedwater pump in a thermal power plant, characterized in that: include: According to the acquired sealing water data, the sealing water inlet and return water temperature difference, the sealing water inlet and unloading water pressure difference, the sealing water inlet and return water flow difference and the leakage water flow of the water supply pump are calculated respectively; the sealing water data includes the sealing water inlet temperature, the sealing water inlet pressure, the sealing water inlet flow, the sealing water outlet temperature, the sealing water outlet flow, the unloading water pressure and the unloading water flow; In response to the sealing water inlet and return water temperature difference being less than the first preset temperature, the sealing water outlet temperature being less than the second preset temperature, the sealing water inlet and return water pressure difference being greater than the preset pressure, the sealing water inlet and return water flow difference being greater than the preset flow, and the water flow rate of the water supply pump leakage being greater than the preset flow rate, the sealing water meets the sealing condition, and the sealing water opening is reduced within the preset optimal opening range to obtain the optimal opening of the sealing water; In response to the sealing water inlet and return water temperature difference being not less than the first preset temperature, the sealing water outlet temperature being not less than the second preset temperature, the sealing water inlet and return water pressure difference being not greater than the preset pressure, the sealing water inlet and return water flow difference being not greater than the preset flow or the water feed pump leakage water flow being not greater than the preset flow, the sealing water does not meet the sealing conditions, and the sealing water opening is increased within the preset optimal opening range to obtain the optimal opening of the sealing water.

2. The method for controlling sealing water of a feedwater pump in a thermal power plant according to claim 1, characterized in that: According to the acquired sealing water data, the sealing water inlet and return water temperature difference, the sealing water inlet and return water pressure difference, the sealing water inlet and return water flow difference and the water leakage flow of the water pump are calculated respectively, including: △T=T2-T1; △P=P1-P3; △Q1=Q1-Q2; △Q2=Q2+Q3-Q1; Among them, △T represents the sealing water inlet and return water temperature difference; △P represents the sealing water inlet and unloading water pressure difference; △Q1 represents the sealing water inlet and return water flow difference; △Q2 represents the leakage water flow of the water feed pump; T1 represents the sealing water inlet temperature; P1 represents the sealing water inlet pressure; Q1 represents the sealing water inlet flow; T2 represents the sealing water outlet temperature; Q2 represents the sealing water outlet flow; P3 represents the unloading water pressure; Q3 represents the unloading water flow.

3. The method for controlling sealing water of a feedwater pump in a thermal power plant according to claim 1, characterized in that: The acquisition of the preset optimal opening range includes: Record the optimal opening of the sealing water to ensure safe operation of the feedwater pump under different unit load and main steam pressure conditions; The range formed by the optimal opening degrees of all sealing waters is taken as the optimal opening range of sealing water.

4. The method for controlling sealing water of a feedwater pump in a thermal power plant according to claim 1, characterized in that: Reduce the opening of the sealing water within the preset optimal opening range to obtain the optimal opening of the sealing water, including: Gradually reduce the opening of the sealing water within the preset optimal opening range to obtain the sealing water conditions corresponding to each opening under the same unit load and main steam pressure conditions, until the sealing water opening is less than the preset opening or the sealing water does not meet the sealing conditions, and take the opening corresponding to the optimal sealing water condition as the optimal opening of the sealing water.

5. The method for controlling sealing water of a feedwater pump in a thermal power plant according to claim 4, characterized in that: The acquisition of the optimal sealing water working condition under the same unit load and main steam pressure conditions includes: If the sealing water is mechanically sealed, the condition where the difference in the sealing water inlet and return flow rate is closest to zero under the same unit load and main steam pressure conditions is selected as the optimal sealing water condition; If the sealing water is a labyrinth seal, the operating condition with the smallest sealing water inlet and return flow rate difference under the same unit load and main steam pressure conditions is selected as the optimal sealing water operating condition.

6. The method for controlling sealing water of a feedwater pump in a thermal power plant according to claim 1, characterized in that: Increase the opening of the sealing water within the preset optimal opening range to obtain the optimal opening of the sealing water, including: The sealing water opening is gradually increased within the preset optimal opening range until the sealing water flow meets the mechanical seal or labyrinth seal, thereby obtaining the optimal sealing water opening.

7. A sealing water control system for a feedwater pump in a thermal power plant, characterized in that: The control method according to any one of claims 1 to 6 is used to adjust the sealing water opening, and the system comprises: Flow meters are installed at the sealing water inlet, sealing water return port and unloading water port of the water supply pump sealing water control system respectively.

8. The sealing water control system for feedwater pumps in thermal power plants according to claim 7, characterized in that: The flow meter is a multi-channel ultrasonic flow meter.

9. The sealing water control system for feedwater pumps in thermal power plants according to claim 8, characterized in that: The multi-channel ultrasonic flowmeter has a measuring range of [0, 200 t / h], a measurement error within [-0.5%, 0.5%], a temperature applicable range of [-30°C, 300°C], and a pipe diameter applicable range of [50mm, 3000mm].

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