A steam-water separation reheat system and exhaust method for a nuclear power plant

Abstract

This invention relates to a steam-water separation reheat system and venting method for nuclear power plants. The steam-water separation reheat system connects a condensate drain system, a condensing unit, and a high-pressure heater, and includes: an extraction reheater, a first venting line, and a second venting line. The extraction reheater is connected to the high-pressure heater via the first venting line and to the condensing unit via the second venting line. The extraction reheater is also connected to the condensate drain system, controlling the condensate delivery to the condensate drain system. Under a first operating condition, steam is delivered to the steam side of the high-pressure heater via the first venting line. Under a second operating condition, a portion of the steam is delivered to the steam side of the high-pressure heater via the first venting line, and the remaining steam is delivered to the condensing unit via the second venting line. Implementing the technical solution of this invention, by adding a second venting line and combining it with the first venting line according to actual conditions, allows for flexible responses to different operating conditions and emergency situations, improving the reliability of the entire steam-water separation reheat system and optimizing venting efficiency.

Description

Technical Field

[0001] This invention relates to the field of conventional island equipment in nuclear power plants, and more particularly to a steam-water separation reheat system and exhaust method for a nuclear power plant. Background Technology

[0002] During normal operation, the gas-water separation reheat system (GSS) of a nuclear power plant in my country vents gas through normal exhaust pipelines. However, since 2012, the plant has experienced fluctuations in various parameters, including the inlet flow rate and pressure of the extraction reheater, the condensate level in the condensate receiving tank, and the condensate valve position. This manifests as fluctuations in the downstream regulating valve position and the condensate level in the receiving tank, which in turn causes synchronous fluctuations in the extraction flow rate and pressure of the first-stage reheater in the gas-water separation reheat system. The fluctuation amplitude of the regulating valve position started at approximately 10% and increased annually, occasionally reaching a maximum fluctuation of 0–100%, resulting in loss of regulation. The condensate level in the receiving tank fluctuated by a maximum of -0.26m to -0.02m, and the increased fluctuation amplitude led to frequent low-level alarms triggered by the main control system.

[0003] This problem severely disrupted the safe and stable operation of the system, causing fluctuations in the control valve position, frequently triggering low level alarms in the condensate receiving tank, and consequently affecting the normal operation of the steam-water separation reheat system's extraction reheater. This resulted in excessive wear of the control valve packing, creating a vicious cycle that required frequent on-site intervention, inspections, and contingency plan implementation by operations and professional personnel. The affected equipment underwent continuous inspections during routine maintenance and five major overhauls, consuming significant manpower and resources.

[0004] Large fluctuations in the condensate receiving tank level are a more serious problem. The consequences are that when level control fluctuates, especially to very high levels, it can cause isolation of the steam-water separation reheat system, affecting unit output by more than 10%. Frequent and large fluctuations (30%–100%) in the regulating valves cause wear on the valve stem packing. If this leads to packing leakage, the packing needs to be repaired during normal condensate isolation in the condensate receiving tank, which will also affect unit output by at least 10%. Furthermore, it causes the load on the steam-water separation reheater (MSR) in the steam-water separation reheat system to be too low in the first stage and too high in the second stage, deviating from the design load distribution and increasing the scouring of the heat transfer tubes of the second stage reheater. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a steam-water separation and reheat system and exhaust method for a nuclear power plant.

[0006] The technical solution adopted by the present invention to solve its technical problem is: a steam-water separation and reheating system for a nuclear power plant, wherein the steam-water separation and reheating system is connected to a condensate system, a condensing device, and a high-pressure heater, and the steam-water separation and reheating system includes: an extraction reheater and an exhaust pipeline, wherein the exhaust pipeline includes a first exhaust pipeline and a second exhaust pipeline, wherein the extraction reheater is connected to the high-pressure heater through the first exhaust pipeline and to the condensing device through the second exhaust pipeline, and the extraction reheater is also connected to the condensate system for transporting condensate to the condensate system;

[0007] Under the first operating condition, the condensate discharged from the extraction reheater is transported to the condensate system, and the steam discharged from the extraction reheater is transported to the steam side of the high-pressure heater through the first exhaust pipeline.

[0008] Under the second operating condition, the condensate discharged from the extraction reheater is transported to the condensate system, a portion of the steam discharged from the extraction reheater is transported to the steam side of the high-pressure heater through the first exhaust pipeline, and the remaining steam is controlled to be transported to the condenser through the second exhaust pipeline.

[0009] Preferably, the first exhaust pipeline is provided with a valve for controlling the opening and closing of the fluid passage and an orifice plate disposed downstream of the valve. The valve is used to open and close the fluid passage, and the orifice plate adjusts the flow rate of steam in the first exhaust pipeline by changing the diameter of the orifice.

[0010] Preferably, the second exhaust pipeline is equipped with an electric valve, which is used to regulate the steam flow rate in the second exhaust pipeline.

[0011] Preferably, the exhaust pipeline further includes a third exhaust pipeline, and the extraction reheater and the condenser are also connected through the third exhaust pipeline. Under the third operating condition, the condensate discharged by the extraction reheater is transported to the condensate system, and the steam discharged by the extraction reheater is transported to the condenser through the third exhaust pipeline.

[0012] The present invention also provides an exhaust method for a nuclear power plant steam-water separation and reheat system, applied to the nuclear power plant steam-water separation and reheat system, comprising:

[0013] S1. Determine whether the conditions of the first operating condition are met. If so, control the steam to be delivered to the steam side of the high-pressure heater through the first exhaust pipeline.

[0014] S2. Determine whether the conditions for the second operating condition are met. If so, control a portion of the steam to be transported to the steam side of the high-pressure heater through the first exhaust pipeline, and control the remaining steam to be transported to the condenser through the second exhaust pipeline.

[0015] S3. Determine whether the conditions of the third operating condition are met. If so, control the steam to be transported to the condenser through the third exhaust pipeline.

[0016] Preferably, the hydrophobic system includes a hydrophobic receiving tank, and the conditions for determining whether the second operating condition is met include:

[0017] Monitor the liquid level in the hydrophobic receiving tank and determine whether the liquid level exceeds a preset height threshold. If so, determine that the conditions of the second operating condition are met.

[0018] Preferably, the drainage system discharges drainage through a drainage pipeline, and the drainage pipeline is equipped with a drainage control valve. The conditions for determining whether the second operating condition is met include:

[0019] Monitor the valve position fluctuation of the drainage control valve, determine whether the valve position fluctuation exceeds the preset first fluctuation threshold and does not converge within a preset time. If so, determine that the conditions of the second operating condition are met.

[0020] Preferably, the drainage system discharges drainage through a drainage pipeline, and the drainage pipeline is equipped with a drainage control valve. The conditions for determining whether the second operating condition is met include:

[0021] Monitor the valve position fluctuation of the drainage control valve and determine whether the valve position fluctuation exceeds the preset second fluctuation threshold. If so, determine that the conditions of the second operating condition are met.

[0022] Preferably, the conditions for determining whether the third operating condition is met include:

[0023] Monitor the reactor's operating power and determine whether the operating power is lower than a preset power threshold. If so, determine that the conditions for the third operating condition are met.

[0024] Preferably, the control of the steam portion being transported to the steam side of the high-pressure heater via the first exhaust pipeline, and the control of the remaining steam being transported to the condenser via the second exhaust pipeline, comprises:

[0025] S21: Keep the steam flow rate of the first exhaust pipeline constant, increase the steam flow rate of the second exhaust pipeline until the second operating condition ends, and maintain the steam flow rate of the second exhaust pipeline at the flow rate at the end of the second operating condition.

[0026] Implementing this invention has the following beneficial effects: A second exhaust pipeline is added, which can be combined with the first exhaust pipeline for operation according to actual conditions. The exhaust volume can be flexibly adjusted according to the actual needs of the system, thereby adapting to different operating conditions and load changes, improving the system's flexibility and adaptability; the exhaust volume can be controlled more effectively, reducing energy loss, improving the system's thermal efficiency, and optimizing system performance; when the first exhaust pipeline cannot meet the exhaust demand, the second exhaust pipeline can intervene to ensure continuous system operation, reduce downtime, enhance system reliability, ensure that the steam-water separation reheat system can operate more effectively, successfully solve the problem of fluctuations in some parameters of the condensate system, avoid frequent on-site inspections and interventions by various professionals during routine operations, thereby reducing maintenance costs. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0028] Figure 1 This is a schematic diagram of an embodiment of a steam-water separation and reheat system for a nuclear power plant according to the present invention;

[0029] Figure 2 This is a schematic diagram of an embodiment of a steam-water separation and reheat system for a nuclear power plant according to the present invention;

[0030] Figure 3 This is a schematic diagram of an embodiment of a steam-water separation and reheat system for a nuclear power plant according to the present invention. Detailed Implementation

[0031] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the invention will now be described in detail with reference to the accompanying drawings. Features specified with "first," "second," "third," etc., may explicitly or implicitly include one or more of those features. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0032] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0033] like Figure 1As shown, in one embodiment of a nuclear power plant steam-water separation reheat system according to the present invention, a steam-water separation reheat system for a nuclear power plant is provided, which connects a condensate system, a condensing unit, and a high-pressure heater. The condensate system is used to collect and transport condensate separated from the extraction reheater, including a condensate receiving tank connected to the water side of the high-pressure heater via a pipeline, on which a condensate regulating valve is installed. This condensate is returned to the water side of the high-pressure heater through a drain pipeline, utilizing the residual heat of the condensate to heat the feedwater, thereby achieving recycling. The high-pressure heater is used to heat the feedwater or recover heat from the steam. It receives exhaust steam from the extraction reheater to increase the temperature of the feedwater. Exhaust steam refers to steam that has completed its work in the turbine, with its pressure and temperature reduced, becoming wet steam or saturated steam with lower temperature and pressure. The condensing unit typically refers to a condenser, used to condense the excess exhaust steam discharged from the extraction reheater into water, thereby completing the collection of excess exhaust steam. It receives excess exhaust steam from the extraction reheater and condenses it.

[0034] The steam-water separation reheat system includes: a steam extraction reheater and an exhaust pipeline, which includes a first exhaust pipeline and a second exhaust pipeline.

[0035] The extraction reheater is connected to the high-pressure heater via a first exhaust line and to the condenser via a second exhaust line. The extraction reheater is also connected to a condensate drain system for transferring condensate to the system. The extraction reheater extracts a portion of the steam from the turbine and then heats the exhaust gas from the high-pressure cylinder within the reheater to reduce its humidity. This process increases the temperature and decreases the humidity of the high-pressure cylinder exhaust gas, thereby improving the overall thermal efficiency of the cycle. The tube side of the extraction reheater uses steam extracted from the turbine to heat the exhaust gas from the high-pressure cylinder. After heat exchange, most of this extracted steam condenses into water and is discharged through the condensate drain line; a small portion of non-condensable gases and steam is discharged through the exhaust line.

[0036] Under the first operating condition, the condensate discharged from the extraction reheater is sent to the condensate system, and the steam discharged from the extraction reheater is sent to the steam side of the high-pressure heater through the first exhaust pipeline. The first operating condition refers to a condition where the liquid level in the condensate receiving tank does not exceed a preset height threshold, the valve position fluctuation of the condensate regulating valve does not exceed a preset first fluctuation threshold, and the first exhaust pipeline is operating normally to meet the steam discharge requirements. Under this operating condition, the second exhaust pipeline is not in use. The first exhaust pipeline is a normal exhaust pipeline, connecting the extraction reheater and the high-pressure heater. Under the first operating condition, the exhaust steam after work is delivered to the steam side of the high-pressure heater through the first exhaust pipeline, where it may be further utilized to heat the feedwater.

[0037] In the second operating condition, the condensate discharged from the extraction reheater is sent to the condensate system. A portion of the steam discharged from the extraction reheater is sent to the steam side of the high-pressure heater via the first exhaust line, and the remaining steam is sent to the condenser via the second exhaust line. The second operating condition includes abnormal fluctuations in the condensate level in the condensate receiving device (e.g., condensate receiving tank) of the condensate system, and valve position fluctuations in the condensate regulating valve of the condensate receiving device, leading to malfunctions in the steam-water separation reheater. The second exhaust line is a backup exhaust line connecting the extraction reheater and the condenser. In the second operating condition, a portion of the steam is sent to the condenser via the second exhaust line, where it is condensed into water.

[0038] The technical solution of this embodiment adds a second exhaust pipeline, which is then combined with the first exhaust pipeline for operation according to the actual situation. This overcomes the problem of system parameter fluctuations caused by the limitation of the exhaust volume adjustment of the exhaust pipeline to the orifice plate diameter when using a single exhaust pipeline. This embodiment combines two solutions, flexibly adjusting the exhaust volume according to the actual needs of the system to adapt to different operating conditions and load changes, thereby improving the system's flexibility and adaptability. It can more effectively control the exhaust volume, reduce energy loss, improve system thermal efficiency, and optimize system performance. When the first exhaust line cannot meet the exhaust demand, causing fluctuations in parameters such as the intake flow rate, intake pressure, condensate level in the condensate receiving tank, and condensate valve position of the extraction steam reheater, the second exhaust line can intervene to increase the exhaust volume of the extraction steam reheater, reducing the fluctuations in parameters such as the intake flow rate, intake pressure, condensate level in the condensate receiving tank, and condensate valve position. This ensures continuous system operation, reduces downtime, enhances system reliability, and ensures more efficient operation of the steam-water separation reheat system. It successfully solves the problem of fluctuations in some parameters of the condensate system, avoiding frequent on-site inspections and interventions by various professionals during routine operations, thereby reducing maintenance costs.

[0039] In one specific embodiment, a valve for controlling the opening and closing of a fluid passage and an orifice plate located downstream of the valve are installed on the first exhaust pipeline. The valve is used to open and close the fluid passage, and the orifice plate regulates the steam flow rate in the first exhaust pipeline by changing the orifice diameter. In this embodiment, the valve and orifice plate are jointly installed on the first exhaust pipeline. The valve is mainly used to open and close the fluid passage in the first exhaust pipeline, achieving rapid response and precise control of the flow rate. During overhauls, the orifice diameter can be changed to regulate the steam flow rate in the first exhaust pipeline. The flow coefficient of the orifice plate and the ratio of the orifice diameter to the pipe diameter determine the upper limit of the flow rate. By adjusting the orifice diameter, the maximum flow rate of the fluid in the first exhaust pipeline can be controlled. The orifice plate is used for continuous flow control, providing stable flow regulation. The valve and orifice plate work together; the valve is used to open and close the fluid flow in the first exhaust pipeline, and the orifice plate is used to limit the fluid flow rate, avoiding system overload caused by sudden flow increases, and ensuring the stability and reliability of the system under high concurrency conditions.

[0040] During the overhaul, the required increase in exhaust volume is calculated based on the daily valve opening. The orifice plate of the first exhaust pipeline is enlarged to ensure system stability after the overhaul, relying solely on the first exhaust pipeline. In this embodiment, the total exhaust volume of the first and second exhaust pipelines during daily operation can be calculated using the formula Q1 / Q2=(D1 / D2). 2 Calculate the required increase in orifice plate diameter, where Q1 and Q2 are the fluid flow rates of the first and second exhaust pipelines, and D1 and D2 are the diameters of the orifice plate on the first exhaust pipeline before and after the overhaul. Based on the calculation results, enlarge the orifice plate of the first exhaust pipeline so that the system can operate stably after the overhaul using only the first exhaust pipeline.

[0041] Implementing the technical solution of this embodiment, reasonably increasing the exhaust volume of the first exhaust pipeline, helps to better control the pressure and temperature inside the reactor, thereby optimizing the system performance; by pre-adjusting the exhaust orifice plate, the additional maintenance requirements caused by system instability can be reduced, thus lowering maintenance costs; ensuring the system can operate stably helps to reduce potential safety risks and improve the safety of the nuclear power plant.

[0042] In one specific embodiment, an electric valve is installed on the second exhaust pipeline to regulate the steam flow rate within it. In this embodiment, the second exhaust pipeline serves as a backup exhaust pipeline, allowing for gradual increase in flow rate as needed. Therefore, valve control is employed. The electric valve enables precise flow regulation; by changing the valve opening, the flow rate of the fluid within the second exhaust pipeline is adjusted. This regulation is more precise and flexible than traditional orifice plate regulation. By gradually increasing the flow rate of the second exhaust pipeline, the system's exhaust capacity can be utilized more effectively, reducing energy loss and improving the overall system's thermal efficiency.

[0043] like Figure 2 As shown, in one specific embodiment, the exhaust pipeline further includes a third exhaust pipeline. The extraction reheater and the condensing unit are also connected through the third exhaust pipeline. Under the third operating condition, the condensate discharged from the extraction reheater is transported to the condensate system, and the steam discharged from the extraction reheater is transported to the condensing unit through the third exhaust pipeline.

[0044] In this embodiment, the third operating condition refers to the state when the power of the nuclear power plant turbine is lower than a certain preset power threshold. In this state, the third exhaust pipeline is put into use as a low-load exhaust pipeline, connecting the extraction reheater and the condensing unit, and transporting steam to the condensing unit through the third exhaust pipeline.

[0045] The technical solution implemented in this embodiment can ensure that the steam-water separation reheat system can operate effectively under low power conditions of the steam turbine, so as to prevent safety hazards caused by excessive pressure or steam accumulation, ensure the safe operation of the reactor and steam turbine, improve the efficiency of the thermodynamic cycle, reduce energy loss, and maintain high thermal economy even under low power conditions.

[0046] The steam-water separation and reheating system of this embodiment can be applied to steam-water separation and reheating systems, such as... Figure 3 As shown, the steam-water separation reheat system connects to the high-pressure heater, condenser, and condensate system. The steam-water separation reheat system includes an extraction reheater, a first exhaust line ①, a second exhaust line ②, and a third exhaust line ③. The condensate system includes a condensate receiving tank, a drain line ④, and a drain line ⑤.

[0047] The extraction reheater is connected to the high-pressure heater via the first exhaust line ①, which is equipped with valve 226VV and orifice plate 204DI. The extraction reheater is connected to the condenser via the second exhaust line ② and the third exhaust line ③, which is equipped with electric valve 225VV and orifice plate 204DI, and electric valve 206VV and orifice plate 202DI, respectively. The condenser is connected to the condensate receiving tank via the drain line ⑤, and the extraction reheater is connected to the condensate receiving tank via the drain line ⑥. A dedicated exhaust line ⑦ is also designed between the extraction reheater and the condensate receiving tank to provide continuous exhaust flow, keeping the temperature difference of the heat transfer tubes at an acceptable level. The condensate receiving tank is connected to the water side of the high-pressure heater via the drain line ④, which is equipped with a condensate regulating valve 212VL.

[0048] The extraction reheat system extracts a portion of steam from the turbine and heats the exhaust gas from the high-pressure cylinder in the extraction reheater. After completing the work, it produces exhaust steam and condensate. The exhaust steam is discharged to the steam side of the high-pressure heater through the first exhaust pipeline. If the amount of steam discharged is too large, a portion of it is discharged to the condenser through the second exhaust pipeline. The condensate is discharged to the water side of the high-pressure heater through the condensate receiving tank and drain pipeline ④. If the amount of condensate discharged is too large, a portion of it is discharged to the condenser through the drain pipeline ⑤.

[0049] Furthermore, the first, second, and third exhaust lines are all connected to the same output port of the extraction reheater to facilitate flow distribution. In other embodiments, they can also be connected to different output ports of the extraction reheater.

[0050] The present invention also provides an exhaust method for a nuclear power plant steam-water separation and reheat system, applied to the steam-water separation and reheat system of the nuclear power plant described in the above embodiments, comprising the following steps:

[0051] S1. Determine whether the conditions of the first operating condition are met. If so, control the steam to be delivered to the steam side of the high-pressure heater through the first exhaust pipeline.

[0052] In this step, it should be noted that the first operating condition refers to the operating condition in which the liquid level in the condensate receiving tank does not exceed the preset height threshold, the valve position fluctuation of the condensate regulating valve does not exceed the preset first fluctuation threshold, and the first exhaust pipeline can meet the steam emission requirements when it is working normally. Under this operating condition, the second and third exhaust pipelines are not put into use.

[0053] S2. Determine whether the conditions for the second operating condition are met. If so, control a portion of the steam to be transported to the steam side of the high-pressure heater through the first exhaust pipeline, and control the remaining steam to be transported to the condenser through the second exhaust pipeline.

[0054] Under the second operating condition, since the flow rate of the first exhaust pipeline is not adjustable, the exhaust volume of the first exhaust pipeline alone cannot meet the requirements, and both the first and second exhaust pipelines need to be used simultaneously. Therefore, while keeping the opening of the first exhaust pipeline constant, the opening of the second exhaust pipeline needs to be gradually increased to increase the steam discharge of the entire steam-water separation reheat system.

[0055] In one specific embodiment, a second exhaust pipeline is added, and the opening degree of the backup pipeline is increased according to the fluctuation of system parameters to bring the system to a new stable state. The first and second exhaust pipelines are put into operation in combination according to the actual situation.

[0056] In this embodiment, the second exhaust pipeline is put into use according to actual needs. By adjusting the opening of the second exhaust pipeline, the exhaust volume can be flexibly adjusted according to the actual needs of the system, thereby adapting to different operating conditions and load changes, improving the system's flexibility and adaptability; it can more effectively control the exhaust volume, reduce energy loss, improve the system's thermal efficiency, and optimize system performance; when the first exhaust pipeline cannot meet the exhaust demand, the second exhaust pipeline can intervene to ensure continuous system operation, reduce downtime, and enhance system reliability.

[0057] In an optional embodiment, controlling a portion of the steam to be delivered to the steam side of the high-pressure heater through the first exhaust pipeline and controlling the remaining steam to be delivered to the condenser through the second exhaust pipeline includes: S21: keeping the steam discharge of the first exhaust pipeline constant, gradually increasing the steam flow rate of the second exhaust pipeline until the second operating condition ends, and maintaining the steam flow rate of the second exhaust pipeline at the flow rate at the end of the second operating condition.

[0058] In this embodiment, the valve on the second exhaust pipeline is an electrically operated valve. When the second operating condition is met, the valve is opened by 5%, and the fluctuations in liquid level and valve position are observed. Once the fluctuations return to normal, the current opening is maintained. Implementing the technical solution of this embodiment ensures that the steam-water separation and reheat system maintains safety and efficiency while meeting the operating conditions, avoiding potential risks caused by excessively large or small valve openings. It also allows for better control of the steam-water separation and reheat system, ensuring system stability and safety under different operating conditions. Furthermore, this helps extend the service life of the equipment and reduces the likelihood of malfunctions.

[0059] The conditions for the second operating condition include the following three, and the second operating condition is considered to be met when any one of the conditions is met.

[0060] In one specific embodiment, determining whether the conditions for the second operating condition are met includes: monitoring the liquid level in the hydrophobic receiving tank, determining whether the liquid level exceeds a preset height threshold, and if so, determining that the conditions for the second operating condition are met.

[0061] In this embodiment, the steam-water separation reheat system is connected to the condensate collection system, enabling the measurement of the condensate level in the condensate receiving tank. The steam-water separation reheat system in a nuclear power plant primarily utilizes the exhaust steam from the turbine. This exhaust steam is used to heat the exhaust gas from the high-pressure cylinder via an extraction reheater, increasing its temperature and reducing its humidity. After performing its work in the extraction reheater, the remaining steam and condensate are discharged to the steam and water sides of the high-pressure heater, respectively, for recycling.

[0062] In this embodiment, after the liquid level in the condensate receiving tank exceeds the preset liquid level threshold, the steam-water separation reheat system puts the second exhaust pipeline into use, controlling a portion of the exhaust steam to be directly discharged to the condenser, ensuring that the rate of increase of the liquid level in the condensate receiving tank is reduced, and avoiding potential safety risks and equipment damage.

[0063] In another specific embodiment, the drainage system discharges drainage through a drainage pipeline, which is equipped with a drainage control valve. Determining whether the second operating condition is met includes: monitoring the valve position fluctuation of the drainage control valve, determining whether the valve position fluctuation exceeds a preset first fluctuation threshold and fails to converge within a preset time; if so, the second operating condition is determined to be met.

[0064] In this embodiment, if the valve position fluctuation of the condensate regulating valve exceeds a preset first fluctuation threshold and fails to converge within a specified time, the steam-water separation reheat system will determine that the condensate regulating valve has lost its regulation and output an alarm to remind staff to intervene in advance and eliminate risks. Specifically, if the valve position fluctuation of the condensate regulating valve is less than the first fluctuation threshold, it is determined that the condensate regulating valve has not lost its regulation. If the valve position fluctuation exceeds the first fluctuation threshold but converges again within a specified time, it is determined that the condensate regulating valve has not lost its regulation. If the valve position fluctuation exceeds the first fluctuation threshold and fails to converge within a specified time, it is determined that the condensate regulating valve has lost its regulation. Implementing the technical solution of this embodiment can promptly remind staff to intervene in advance when the condensate regulating valve may lose its regulation, so as to detect potential faults in a timely manner and repair them, thereby avoiding the problem of excessively high liquid levels in the condensate receiving tank.

[0065] In another specific embodiment, the drainage system discharges drainage through a drainage pipeline, which is equipped with a drainage control valve. Determining whether the second operating condition is met includes: monitoring the valve position fluctuation of the drainage control valve, determining whether the valve position fluctuation exceeds a preset second fluctuation threshold; if so, the second operating condition is deemed met, wherein the second fluctuation threshold is greater than the first fluctuation threshold.

[0066] In this embodiment, when the valve position fluctuation of the condensate regulating valve exceeds a preset second fluctuation threshold, it frequently triggers a low liquid level alarm in the condensate receiving tank, affecting the normal operation of the extraction reheater of the steam-water separation reheat system and causing excessive wear on the valve packing of the condensate regulating valve, creating a vicious cycle. Implementing the technical solution of this embodiment can promptly adjust the liquid level in the condensate receiving tank when the valve position fluctuation of the condensate regulating valve exceeds the preset second fluctuation threshold, reducing the discharge burden on the condensate regulating valve and avoiding the problem of frequent alarms in the steam-water separation reheat system, requiring frequent maintenance by personnel.

[0067] S3. Determine whether the conditions for the third operating condition are met. If so, control the steam to be delivered to the condensing unit through the third exhaust pipeline. In a specific embodiment, when the power of the nuclear power plant turbine is lower than a certain preset power threshold, the third exhaust pipeline is automatically put into use under the control of the steam-water separation reheat system, and control the steam to be delivered to the condensing unit through the third exhaust pipeline.

[0068] The technical solution implemented in this embodiment can ensure that the steam-water separation reheat system can operate effectively under low power conditions of the steam turbine, so as to prevent safety hazards caused by excessive pressure or steam accumulation, ensure the safe operation of the reactor and steam turbine, improve the efficiency of the thermodynamic cycle, reduce energy loss, and maintain high thermal economy even under low power conditions.

[0069] In existing technology, a nuclear power plant in my country experienced oscillations and fluctuations in various parameters of its steam-water separation reheat system, including inlet air flow rate, inlet air pressure, condensate level, and condensate valve position. These fluctuations manifested as fluctuations in the downstream regulating valve position of the condensate receiving tank, fluctuations in the condensate receiving tank level, and simultaneous fluctuations in the extraction air flow rate and pressure of the first-stage reheater in the steam-water separation reheat system. Through long-term on-site monitoring and routine overhauls, the cause of the problem was found to be low extraction air pressure and condensate pressure in the exhaust pipeline of the steam-water separation reheat system. Insufficient and unstable exhaust caused the system parameter fluctuations.

[0070] This nuclear power plant applies the technical solution of this invention to gradually increase the opening of the second exhaust pipeline and the exhaust volume during normal operation by optimizing the operation of existing equipment, while maintaining the opening of the second exhaust pipeline when the fluctuation range is acceptable. During major overhauls, the exhaust volume of the first exhaust pipeline is increased by enlarging the orifice plate so that the exhaust volume of the first exhaust pipeline can meet the daily needs.

[0071] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A steam-water separation reheating system of a nuclear power plant, which is connected to a drain system, a condensing device and a high-pressure heater, characterized in that, The steam-water separation reheating system comprises: a steam extraction reheater, and exhaust pipelines, the exhaust pipelines comprising a first exhaust pipeline and a second exhaust pipeline, wherein the steam extraction reheater is connected to the high-pressure heater through the first exhaust pipeline, the steam extraction reheater is connected to the condensing device through the second exhaust pipeline, and the steam extraction reheater is also connected to the drain system for conveying drain water to the drain system; In the first operating condition, the drain water discharged from the steam extraction reheater is conveyed to the drain system, and the steam discharged from the steam extraction reheater is conveyed to the steam side of the high-pressure heater through the first exhaust pipeline; In the second operating condition, the drain water discharged from the steam extraction reheater is conveyed to the drain system, part of the steam discharged from the steam extraction reheater is conveyed to the steam side of the high-pressure heater through the first exhaust pipeline, and the remaining steam is conveyed to the condensing device through the second exhaust pipeline.

2. The steam-water separation and reheating system according to claim 1, characterized in that, A valve for opening and closing the fluid passage is arranged on the first exhaust pipeline, and an orifice plate is arranged downstream of the valve, the valve is used for opening and closing the fluid passage, and the orifice plate adjusts the flow of the steam in the first exhaust pipeline by changing the hole diameter.

3. The steam-water separation and reheating system according to claim 1, characterized in that, An electric valve is arranged on the second exhaust pipeline, and the electric valve is used for adjusting the flow of the steam in the second exhaust pipeline.

4. The steam-water separation and reheating system according to claim 1, characterized in that, The exhaust pipelines further comprise a third exhaust pipeline, the steam extraction reheater is also connected to the condensing device through the third exhaust pipeline, and in the third operating condition, the drain water discharged from the steam extraction reheater is conveyed to the drain system, and the steam discharged from the steam extraction reheater is conveyed to the condensing device through the third exhaust pipeline.

5. A method for exhausting steam-water separation and reheating system of nuclear power plant, applied to the steam-water separation and reheating system of any one of claims 1-3, characterized in that, Comprise: S1, judging whether the condition of the second operating condition is met, if not, controlling the steam to be conveyed to the steam side of the high-pressure heater through the first exhaust pipeline; if yes, executing step S2; S2, controlling part of the steam to be conveyed to the steam side of the high-pressure heater through the first exhaust pipeline, and controlling the remaining steam to be conveyed to the condensing device through the second exhaust pipeline; The second fluctuation threshold is greater than the first fluctuation threshold; The drain system comprises a drain receiving tank, and the judging whether the condition of the second operating condition is met comprises: monitoring the liquid level of the liquid in the drain receiving tank, judging whether the liquid level exceeds a preset height threshold, and if yes, determining that the condition of the second operating condition is met; Or, the drain system discharges drain water through a drain pipeline, a drain control valve is arranged on the drain pipeline, and the judging whether the condition of the second operating condition is met comprises: monitoring the valve position fluctuation of the drain control valve, judging whether the valve position fluctuation exceeds a preset first fluctuation threshold and does not converge within a preset time, and if yes, determining that the condition of the second operating condition is met; Or, the drain system discharges drain water through a drain pipeline, a drain control valve is arranged on the drain pipeline, and the judging whether the condition of the second operating condition is met comprises: monitoring the valve position fluctuation of the drain control valve, judging whether the valve position fluctuation exceeds a preset second fluctuation threshold, and if yes, determining that the condition of the second operating condition is met.

6. The exhaust gas method according to claim 5, characterized by, The exhaust pipeline further comprises a third exhaust pipeline, the extraction reheater is further connected with the condenser through the third exhaust pipeline, in the third operation condition, the steam exhausted by the extraction reheater is transported to the condenser through the third exhaust pipeline; The exhaust method further comprises: S3, judging whether the condition of the third operation condition is met, if yes, controlling the steam to be transported to the condenser through the third exhaust pipeline; the judging whether the condition of the third operation condition is met comprises: Monitoring the operation power of the reactor, judging whether the operation power is lower than a preset power threshold, if yes, it is determined that the condition of the third operation condition is met.

7. The exhaust gas method of claim 5, wherein, The controlling part of the steam to be transported to the high-pressure heater steam side through the first exhaust pipeline and the remaining steam to be transported to the condenser through the second exhaust pipeline comprises: S21: keeping the steam flow of the first exhaust pipeline unchanged, increasing the steam flow of the second exhaust pipeline until the second operation condition ends, and maintaining the steam flow of the second exhaust pipeline as the flow at the end of the second operation condition.

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