Low-power platform cooling method for high and medium pressure cylinders of nuclear turbine

Abstract

The invention provides a low-power platform cooling method for a high-pressure cylinder and a medium-pressure cylinder of a nuclear turbine. The low-power platform cooling method for the high-pressure cylinder and the medium-pressure cylinder of the nuclear turbine comprises the steps that the power of a steam turbine generator unit is reduced to 24% Pn at the power reduction rate of 3 MW / min; the power of the steam turbine generator unit is reduced from 24% Pn to 10% Pn at the power reduction rate of 2 MW / min; when the power of the steam turbine generator unit is 10% Pn-8% Pn, the steam turbine generator unit stays and operates for 2 h; the power of the steam turbine generator unit is reduced from 8% Pn to 5% Pn at the power reduction rate of 1 MW / min; and splitting when the power of the steam turbine generator unit is 5% Pn. Through the design of the power rate decline strategy, the problem that in the prior art, the cooling time of a high-pressure cylinder and a medium-pressure cylinder of a nuclear turbine is too long is solved.

Description

Technical Field

[0001] This application belongs to the field of nuclear power turbine technology, specifically relating to a cooling method for the low-power platform of the high-pressure cylinder of a nuclear power turbine. Background Technology

[0002] During major overhauls, minor repairs, and emergency shutdowns of nuclear power turbines, maintenance of related systems on the conventional island turbines must wait until the intermediate and high-pressure cylinders have cooled to 120°C before it can be carried out. Natural cooling of nuclear power turbines after major overhaul shutdowns often takes 4-5 days. If the unit is shut down in an emergency, the cylinder temperature will be even higher, and natural cooling will take 8-9 days to wait for the turbine to cool down to the required temperature.

[0003] Conventional thermal power plants often employ sliding shutdown technology, which reduces steam parameters during load reduction, resulting in a decrease in cylinder temperature. However, due to the stable main steam pressure in the nuclear island of nuclear power turbines, sliding shutdown technology cannot be used. Conventional nuclear power turbines typically use forced air cooling technology for rapid cooling. This technology introduces an external cold source, using air as a medium to remove heat from the cylinder. This technology is highly complex, requiring strict control during the cooling process; even slight errors can lead to serious defects such as cylinder deformation or even shaft bending.

[0004] Therefore, during major and minor overhauls of nuclear power turbines, especially during shutdowns due to malfunctions, there is an urgent need for a safe, reliable, and rapid cooling method to save time during turbine shutdowns and improve unit availability. Summary of the Invention

[0005] In view of this, the embodiments of this application aim to provide a cooling method for the low-power platform of the high-pressure cylinder of a nuclear power turbine, which solves the problem of excessively long cooling time of the high-pressure cylinder of a nuclear power turbine in the prior art by designing a power rate reduction strategy.

[0006] This application provides a method for cooling the low-power platform of the intermediate-pressure cylinder of a nuclear power turbine. The method includes: reducing the power of the turbine generator set to 24%Pn at a power reduction rate of 3MW / min; reducing the power of the turbine generator set from 24%Pn to 10%Pn at a power reduction rate of 2MW / min; maintaining the turbine generator set at a power of 10%Pn-8%Pn for 2 hours; reducing the power of the turbine generator set from 8%Pn to 5%Pn at a power reduction rate of 1MW / min; and disconnecting the turbine generator set when the power is 5%Pn.

[0007] In one specific embodiment of this application, after the turbine generator set power is disconnected at 5%Pn, the cooling method for the low-power platform of the high-pressure cylinder of the nuclear power turbine further includes: after disconnection, keeping the turning gear in operation, turning on the roof fan, partially removing the turbine cylinder insulation, and reducing the shaft seal steam supply pressure from 7.0 kPa to 5.0 kPa.

[0008] In one specific embodiment of this application, after disconnection, keeping the turning gear in operation, turning on the roof fan, partially removing the turbine cylinder insulation, and reducing the shaft seal steam supply pressure from 7.0 kPa to 5.0 kPa, the cooling method for the low-power platform of the high-pressure cylinder of the nuclear power turbine further includes: breaking the vacuum when the high-pressure cylinder temperature drops to 150℃-145℃, with a high-pressure cylinder temperature cooling rate ≤2℃ / h; and stopping the turning gear when the high-pressure cylinder temperature drops to 120℃.

[0009] In one specific embodiment of this application, keeping the turning gear in operation includes: maintaining the turning gear speed at 8 rpm.

[0010] In one specific embodiment of this application, before the power of the steam turbine generator set is reduced from 8%Pn to 5%Pn at a power reduction rate of 1MW / min, the cooling method for the low-power platform of the high-pressure cylinder of the nuclear power steam turbine further includes: when the power of the steam turbine generator set is 8%, cutting off the steam source for the secondary reheat of the steam-water separator reheater, isolating the secondary reheat of the steam-water separator reheater, and controlling the isolation time to within 2 hours.

[0011] In one specific embodiment of this application, the cooling method for the low-power platform of the intermediate and high-pressure cylinder of a nuclear power turbine further includes: real-time monitoring of key parameters of the turbine, including turbine bearing temperature, vibration parameters, rotor eccentricity, differential expansion, shaft displacement, rotor expansion, and cooling rate of the intermediate and high-pressure cylinder; determining whether the key parameters of the turbine are abnormal; if the key parameters of the turbine are abnormal, stopping the cooling of the low-power platform of the intermediate and high-pressure cylinder of the nuclear power turbine; if the key parameters of the turbine are not abnormal, proceeding to the next step.

[0012] The beneficial effects of this application's technical solution are as follows: By implementing a power rate reduction strategy at specific power stages (3MW / min, 2MW / min, 1MW / min) and limiting the operating time (2h) at a specific power platform (10%Pn-8%Pn), a power rate reduction strategy is proposed. This strategy achieves efficient, safe, and controllable cooling of the nuclear power turbine at low power platforms and even during shutdown. It also protects the equipment from thermal stress and rubbing damage caused by expansion, reduces the turbine's shutdown cooling time, improves the efficiency of planned shutdown maintenance, ensures the operational efficiency and safety of the nuclear power plant turbine, and enhances the plant's availability and economic benefits. Furthermore, the embodiments of this application provide a clear and orderly low-power platform cooling operation procedure, which facilitates accurate execution by on-site operators, reduces the risk of human error, and also facilitates training, drills, and troubleshooting for power plant maintenance personnel, improving the standardization level and emergency response capabilities of maintenance work. Attached Figure Description

[0013] Figure 1 The diagram shows a connection structure of a nuclear power turbine and related systems.

[0014] Figure 2 The diagram shown is a flow chart of a method for cooling the low-power platform of the high-pressure cylinder of a nuclear power turbine, according to an embodiment of this application.

[0015] Figure 3 The diagram shown is a flow chart of a method for cooling the low-power platform of the high-pressure cylinder of a nuclear power turbine, according to another embodiment of this application.

[0016] Figure 4 The diagram shown is a flow chart of a method for cooling the low-power platform of the high-pressure cylinder of a nuclear power turbine, according to another embodiment of this application.

[0017] Figure 5 The diagram shown is a flow chart of a method for cooling the low-power platform of the high-pressure cylinder of a nuclear power turbine, according to another embodiment of this application. Figure 6 The figure shown is an experimental data graph obtained using existing conventional shutdown methods. Figure 7 The figure shown is an experimental data graph obtained by using the optimized shutdown method of the low-power platform cooling method of the high-pressure cylinder of a nuclear power turbine provided in the embodiments of this application. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] refer to Figure 1 A nuclear power turbine includes a turbine cylinder system and a steam-water separator-reheater system. The turbine cylinder system includes the high-pressure cylinder 1 and the intermediate-pressure cylinder 2. The steam-water separator-reheater system includes a Moisture Separator Reheater (MSR) 7, which comprises a steam-water separator 4, a primary reheater 5, and a secondary reheater 6. Part of the steam in the high-pressure cylinder 1 enters the primary reheater 5 as a steam source, while part of the main steam enters the secondary reheater 6 as a steam source. After performing work in the high-pressure cylinder 1, the steam passes through the steam-water separator-reheater 7. The steam-water separator-reheater 7 first separates the steam from the water, then performs two-stage heating to convert the steam into superheated steam, which then enters the intermediate-pressure cylinder 2 to continue performing work.

[0020] It should be noted that the high-pressure cylinder 1 and the intermediate-pressure cylinder 2 of the steam turbine are hereinafter referred to as the intermediate-high-pressure cylinder or intermediate-high-pressure cylinder of the steam turbine. In addition, Figure 1 The CNNC power turbine may also include a high-pressure cylinder exhaust pipe 3, a reheat steam pipe 8, a primary reheat steam supply pipe 9, a secondary reheat steam supply pipe 10, a reheat valve 11, an extraction valve 12, a secondary reheat steam supply valve 13, a secondary reheat drain pipe for the steam-water separator reheater 14, a primary reheat drain pipe for the steam-water separator reheater 15, and a shell-side drain pipe for the steam-water separator reheater 16.

[0021] At least one embodiment of this application provides a method for cooling the low-power platform of the intermediate and high-pressure cylinder of a nuclear power turbine. This method for cooling the low-power platform of the intermediate and high-pressure cylinder of a nuclear power turbine can be applied to... Figure 1 The nuclear power turbine system shown. (Reference) Figure 2 The cooling method for the low-power platform of the high-pressure cylinder of the nuclear power turbine includes the following steps.

[0022] S1: Reduce the power of the steam turbine generator set to 24%Pn at a power reduction rate of 3MW / min.

[0023] S2: Reduce the power of the steam turbine generator set from 24%Pn to 10%Pn at a power reduction rate of 2MW / min.

[0024] Specifically, in steps S1 and S2, the turbine begins to reduce power at a rate of 3 MW / min, and after the power is reduced to 24% Pn, the power reduction rate is reduced to 2 MW / min. Thus, the cooling rate of the high- and intermediate-pressure cylinders is increased by increasing the unit's power reduction rate.

[0025] S3: The turbine generator set will remain in operation for 2 hours when its power is between 10%Pn and 8%Pn.

[0026] Specifically, in step S3, after the unit reduces its power to 10%-8% at a power reduction rate of 2MW / min, it stops reducing power and stays on the platform for 2 hours.

[0027] S5: Reduce the power of the steam turbine generator set from 8%Pn to 5%Pn at a power reduction rate of 1MW / min.

[0028] S6: Decouple the turbine generator set when its power is 5%Pn.

[0029] Specifically, in steps S5 and S6, the unit power reduction rate is reduced to 1MW / min, and the unit disconnection operation is performed when the power is reduced to 5%.

[0030] According to the technical solution provided in this application, a power rate reduction strategy is proposed by setting a power reduction rate (3MW / min, 2MW / min, 1MW / min) at specific power stages and limiting the operating time (2h) at a specific power platform (10%Pn-8%Pn). This power rate reduction strategy achieves efficient, safe, and controllable cooling of nuclear power turbines at low power platforms and even during shutdown. It also protects the equipment from thermal stress and rubbing damage caused by expansion, reduces the shutdown cooling time of nuclear power turbines, improves the efficiency of planned shutdown maintenance, ensures the operating efficiency and safety of nuclear power plant turbines, and enhances the availability and economic benefits of the power plant. In addition, this application provides a clear and orderly low-power platform cooling operation procedure, which is conducive to accurate execution by on-site operators, reduces the risk of human error, and facilitates training, drills, and troubleshooting for power plant operation and maintenance personnel, thereby improving the standardization level and emergency response capabilities of operation and maintenance work.

[0031] In at least one embodiment of this application, reference is made to Figure 3 Following step S6 above, the cooling method for the low-power platform of the high-pressure cylinder of the nuclear power turbine also includes step S7.

[0032] S7: After disconnection, keep the turning gear in operation, turn on the roof fan, partially remove the turbine cylinder insulation, and reduce the shaft seal steam supply pressure from 7.0 kPa to 5.0 kPa.

[0033] In this embodiment, by maintaining the turning gear in operation after disconnection, the roof fan is turned on to promote airflow in the turbine building and promote heat exchange between the cylinder wall and the air in the high and medium pressure cylinder; by selectively removing the cylinder insulation, cylinder heat dissipation can be promoted; and by adjusting the parameter setting of the shaft seal steam supply pressure (from 7.0 kPa to 5.0 kPa), the hot steam entering the turbine cylinder is reduced.

[0034] In at least one embodiment of this application, the above-mentioned keeping the turning gear in operation includes: maintaining the turning gear speed at 8 rpm.

[0035] In at least one embodiment of this application, reference is made to Figure 3 Following S7 above, the cooling method for the low-power platform of the high-pressure cylinder of the nuclear power turbine also includes the following steps S8 and S9.

[0036] S8: The vacuum is broken when the temperature of the high-pressure cylinder drops to 150℃-145℃. The cooling rate of the high-pressure cylinder is ≤2℃ / h.

[0037] S9: Stop the turning gear when the temperature of the high and medium pressure cylinder drops to 120℃.

[0038] It should be noted that the cylinder temperature of the intermediate and high-pressure cylinder can be measured through the temperature measuring point in the intermediate cylinder body of the intermediate and high-pressure cylinder.

[0039] In this embodiment, the timing of vacuum failure is precisely controlled based on the intermediate cylinder temperature of the high-pressure cylinder (150℃-145℃), and the timing of turning gear shutdown is precisely controlled based on the intermediate cylinder temperature of the high-pressure cylinder (120℃). In addition, strict cooling rate control (≤2℃ / h) helps to prevent thermal stress concentration and equipment damage caused by excessively rapid cooling, further enhancing the safety margin of the equipment.

[0040] In at least one embodiment of this application, reference is made to Figure 4 Prior to S5 above, the cooling method for the low-power platform of the high-pressure cylinder of the nuclear power turbine also includes the following step S4.

[0041] S4: When the power of the steam turbine generator set is 8%, cut off the steam source for the secondary reheat of the steam-water separator reheater and isolate the secondary reheat of the steam-water separator reheater. The isolation time shall be controlled within 2 hours.

[0042] Specifically, step S4 can be performed simultaneously with S3. For example, during the dwell period, the steam supply to the secondary reheater 6 of the steam-water separator reheater is cut off, and the secondary reheater 6 of the steam-water separator reheater is isolated. Under the condition that the steam supply to the secondary reheater of the steam-water separator reheater is cut off, the power operation time does not exceed 2 hours.

[0043] It should be noted that step S4 may be omitted depending on the on-site equipment conditions. If the secondary reheat steam supply to the steam-water separator reheater is not cut off, then step S5 should be executed directly. Reducing the power reduction rate and lingering at the low-power platform can both increase the duration of the unit's low-power operation, thereby increasing the cooling rate of the high- and intermediate-pressure cylinders.

[0044] In this embodiment of the application, the specific operation method and time limit (within 2 hours) for cutting off the secondary reheat steam source and isolating the secondary heating of the steam-water separator reheater are described.

[0045] In at least one embodiment of this application, reference is made to Figure 5 The cooling method for the low-power platform of the high-pressure cylinder of the nuclear power turbine also includes the following steps.

[0046] S01: Real-time monitoring of key turbine parameters. Key turbine parameters include turbine bearing temperature, vibration parameters, rotor eccentricity, differential expansion, shaft displacement, rotor expansion, and cooling rate of the high- and intermediate-pressure cylinders.

[0047] S02: Determine if there are any abnormalities in the key parameters of the steam turbine.

[0048] S03: If the key parameters of the steam turbine are abnormal, stop the cooling of the low-power platform of the high-pressure cylinder of the nuclear power steam turbine.

[0049] S04: If the key parameters of the steam turbine are not abnormal, proceed to the next step.

[0050] In this embodiment, by monitoring the temperature and vibration of the turbine bearing throughout the process, and monitoring key parameters such as turbine rotor eccentricity, differential expansion, shaft displacement, and rotor expansion, if the above parameters change abnormally to the alarm value and show a trend of continued deterioration, the implementation of the low-power platform cooling method for nuclear power turbines will be stopped. In this way, potential problems can be detected and dealt with in a timely manner, ensuring the safety and stability of the equipment during low-power operation and shutdown.

[0051] The beneficial effects of the embodiments of this application will be illustrated below with specific experimental data. Experimental data obtained using existing conventional shutdown methods are shown in the figure below. Figure 6 As shown in the figure, the experimental data obtained from the shutdown method of this optimized method for cooling the low-power platform of the high-pressure cylinder of a nuclear power turbine, as provided in the embodiments of this application, are shown in the figure. Figure 7 As shown. According to Figure 6 and Figure 7 The comparative experimental data obtained are shown in Table 1 below.

[0052] Table 1. Comparison of experimental data between conventional shutdown methods and optimized shutdown methods.

[0053]

[0054] In Table 1, 023MT, also known as GME023MT, represents the temperature of the lower half of the cylinder intake intermediate block; 024MT, also known as GME024MT, represents the temperature of the upper half of the cylinder intake intermediate block.

[0055] As shown in Table 1, the optimized shutdown method provided in this application extends the low-power dwell time by 85 minutes and reduces the cylinder temperature by 5.1°C during disconnection compared to the conventional shutdown method. The optimized shutdown method increases the shutdown (disconnection to stopping the disc carriage) rate by 0.18°C / h and reduces the shutdown time by 1.51 days.

[0056] It should be noted that the combination of the technical features in the embodiments of this application is not limited to the combination methods described in the embodiments of this application or the combination methods described in specific embodiments. All technical features described in this application can be freely combined or combined in any way, unless they contradict each other.

[0057] As indicated in this application specification and claims, unless the context clearly indicates otherwise, the words "a," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0058] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications or equivalent substitutions made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for cooling a low-power platform of a high- and medium-pressure cylinder of a nuclear power steam turbine, characterized in that: include: Reduce the power of the steam turbine generator set to 24% Pn at a power reduction rate of 3MW / min; Reduce the power of the steam turbine generator set from 24% Pn to 10% Pn at a power reduction rate of 2 MW / min; When the power of the steam turbine generator set is 10% Pn-8% Pn, it will stop and run for 2 hours; Reduce the power of the steam turbine generator set from 8% Pn to 5% Pn at a power reduction rate of 1 MW / min; The steam turbine generator set is decoupled when the power is 5% Pn.

2. The method for cooling the low-power platform of the high- and medium-pressure cylinder of a nuclear power steam turbine according to claim 1, characterized in that: After the steam turbine generator set is disconnected when the power is 5% Pn, the method further comprises: After decoupling, keep the cranking gear in operation, turn on the roof fan, partially remove the turbine cylinder insulation, and reduce the shaft seal steam supply pressure from 7.0 kPa to 5.0 kPa.

3. The method for cooling the low power platform of the high and medium pressure cylinder of a nuclear power steam turbine according to claim 2, characterized in that: After the decoupling, the turning gear is kept in operation, the roof fan is turned on, the turbine cylinder insulation is partially removed, and the shaft seal steam supply pressure is reduced from 7.0 kPa to 5.0 kPa, and the following is also included: When the temperature of high and medium pressure cylinder drops to 150℃-145℃, the vacuum is destroyed, and the cooling rate of high and medium pressure cylinder temperature is ≤2℃ / h; When the temperature of high and medium pressure cylinders drops to 120℃, stop turning.

4. The method for cooling the low power platform of the high and medium pressure cylinder of a nuclear power steam turbine according to claim 2, characterized in that: The method of keeping the turning gear in operation includes: Maintain the cranking speed at 8 rpm.

5. The method for cooling the low power platform of the high and medium pressure cylinder of a nuclear power steam turbine according to claim 1, characterized in that: Before reducing the power of the steam turbine generator set from 8% Pn to 5% Pn at a power reduction rate of 1 MW / min, the method further includes: When the power of the steam turbine generator set is 8%, cut off the steam supply source for the secondary reheat of the steam-water separator reheater, isolate the secondary reheat of the steam-water separator reheater, and control the isolation time within 2 hours.

6. The method for cooling the low power platform of the high and medium pressure cylinder of a nuclear power steam turbine according to any one of claims 1 to 5, characterized in that: Also includes: Real-time monitoring of key parameters of steam turbines, including turbine bearing temperature, vibration parameters, rotor eccentricity, expansion difference, shaft displacement, rotor expansion and high and medium pressure cylinder temperature cooling rate; Determine whether the key parameters of the steam turbine are abnormal; If the key parameters of the steam turbine are abnormal, the low-power platform cooling of the high- and medium-pressure cylinders of the nuclear power steam turbine will be stopped; If there is no abnormality in the key parameters of the turbine, proceed to the next step.

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