Steam-water separation reheating system of nuclear power station and exhaust method

Abstract

The invention relates to a steam-water separation reheating system of a nuclear power plant and an exhaust method, the steam-water separation reheating system is connected with a drainage system, a steam condensing device and a high-pressure heater and comprises a steam extraction reheater, a first exhaust pipeline and a second exhaust pipeline, and the steam extraction reheater is connected with the high-pressure heater through the first exhaust pipeline. The steam extraction reheater is connected with the condensing device through a second exhaust pipeline and further connected with a drainage system, drainage is controlled to be conveyed to the drainage system, and under the first operation working condition, steam is conveyed to the steam side of the high-pressure heater through the first exhaust pipeline; and under the second operation working condition, part of steam is conveyed to the steam side of the high-pressure heater through the first exhaust pipeline, and the remaining steam is conveyed to the steam condensing device through the second exhaust pipeline. According to the technical scheme, the second exhaust pipeline is additionally arranged, the second exhaust pipeline and the first exhaust pipeline are combined and put into operation according to the actual situation, different operation conditions and emergency situations can be flexibly coped with, the reliability of the whole steam-water separation reheating system is improved, and the exhaust efficiency is optimized.

Description

Technical Field

[0001] The invention relates to the field of conventional island equipment of nuclear power plants, and in particular to a steam-water separation reheating system and an exhaust method of a nuclear power plant. Background Art

[0002] During the normal period, the steam separation reheat system (GSS) of a nuclear power plant in my country exhausts air through the normal exhaust pipeline. However, since 2012, the nuclear power plant has experienced fluctuations in various parameters, including the air intake flow rate, air intake pressure, drain level of the drain receiving tank, and drain valve position of the extraction reheater. The fluctuations are manifested in the downstream regulating valve position of the drain receiving tank and the liquid level of the drain receiving tank, which in turn leads to the synchronous fluctuations of the extraction flow rate and extraction pressure of the first-stage reheater of the steam separation reheat system. The fluctuation amplitude of the regulating valve position has increased year by year since about 10%, and occasionally the maximum fluctuation amplitude is 0~100%, and the regulation is lost; the maximum fluctuation amplitude of the drain receiving tank liquid level is -0.26m to -0.02m, and the main control frequently triggers the low liquid level alarm after the fluctuation amplitude increases.

[0003] This problem greatly interfered with the safe and stable operation of the system, causing the valve position of the regulating valve to fluctuate, frequently triggering the low liquid level alarm of the drain receiving tank, and thus affecting the normal operation of the air extraction reheater of the steam-water separation reheat system, causing excessive wear of the regulating valve packing, forming a vicious cycle, and causing the operation and professional personnel to frequently intervene, inspect, and implement the plan on site. After daily and 5 major overhauls, the equipment involved was constantly inspected, consuming a lot of manpower and material resources.

[0004] The problem of large fluctuations in the liquid level of the drain receiving tank is more serious. The consequence is that when the liquid level control fluctuates and the liquid level fluctuates to a high level, the steam-water separation reheat system is isolated, affecting the unit output by more than 10%; the frequent and large fluctuations of the regulating valve (30% to 100%) cause the valve stem packing to wear. If the packing leaks, the packing needs to be repaired when the drain receiving tank is normally drained and isolated, and the unit output is affected by no less than 10%. It also causes the load of the steam-water separation reheater (MSR) in the steam-water separation reheat system to be low at the first level and high at the second level, and the load distribution deviates from the design, which increases the scouring of the heat transfer tubes of the second-level reheater. Summary of the invention

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

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

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

[0008] Under the second operating condition, the steam discharged from the extraction reheater is transported to the drain system, part 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 condensing device 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 channel and a orifice plate arranged downstream of the valve, the valve is used to open and close the fluid channel, and the orifice plate adjusts the flow rate of steam in the first exhaust pipeline by changing the diameter of the expansion hole.

[0010] Preferably, an electric valve is provided on the second exhaust pipeline, and the electric valve is used to adjust the steam flow in the second exhaust pipeline.

[0011] Preferably, the exhaust pipeline also includes: a third exhaust pipeline, the extraction steam reheater and the condensing device are also connected through the third exhaust pipeline, and under the third operating condition, the drain discharged from the extraction steam reheater is transported to the drain system, and the steam discharged from the extraction steam reheater is transported to the condensing device through the third exhaust pipeline.

[0012] The present invention also provides an exhaust method for a steam-water separation and reheating system of a nuclear power plant, which is applied to the steam-water separation and reheating system of the nuclear power plant, and comprises:

[0013] S1, determining whether the conditions of the first operating condition are met, and if so, controlling the steam to be transported to the steam side of the high-pressure heater through the first exhaust pipeline;

[0014] S2, judging whether the conditions of the second operating condition are met, and if so, controlling part of the steam to be transported to the steam side of the high-pressure heater through the first exhaust pipeline, and controlling the remaining steam to be transported to the condensing device 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 condensing device through the third exhaust pipeline.

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

[0017] Monitor the liquid level of the liquid in the hydrophobic receiving tank to determine whether the liquid level exceeds a preset height threshold, and 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 a drainage control valve is provided on the drainage pipeline. The conditions for determining whether the second operating condition is met include:

[0019] Monitor the valve position fluctuation of the drainage control valve to determine whether the valve position fluctuation exceeds a preset first fluctuation threshold and fails to converge within a preset time. If so, determine that the conditions for the second operating condition are met.

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

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

[0022] Preferably, the determination of whether the condition for the third operating condition is met includes:

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

[0024] Preferably, controlling part 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 condensing device through the second exhaust pipeline comprises:

[0025] S21: Keep the steam flow rate of the first exhaust pipeline unchanged, 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 when the second operating condition ends.

[0026] The implementation of the present invention has the following beneficial effects: a second exhaust pipeline is added, and it is combined with the first exhaust pipeline for operation according to actual conditions, and the exhaust volume is flexibly adjusted according to the actual needs of the system, so as to adapt to different operating conditions and load changes, and improve the flexibility and adaptability of the system; the exhaust volume can be more effectively controlled, energy loss can be reduced, the thermal efficiency of the system can be improved, and the system performance can be optimized; when the first exhaust pipeline cannot meet the exhaust demand, the second exhaust pipeline can intervene to ensure the continuous operation of the system, reduce downtime, enhance the reliability of the system, ensure that the steam-water separation reheat system can operate more efficiently, successfully solve the problem of fluctuations in some parameters of the drain system, and avoid frequent on-site inspections and interventions by various professionals during daily work, thereby reducing maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0030] Figure 3 The present invention is a schematic structural diagram of a steam-water separation and reheating system for a nuclear power plant according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described in detail with reference to the accompanying drawings. Features defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of the features. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0033] like Figure 1As shown, in one embodiment of a steam-water separation and reheating system of a nuclear power plant of the present invention, a steam-water separation and reheating system of a nuclear power plant is provided, wherein the steam-water separation and reheating system is connected to a drain system, a condensing device and a high-pressure heater. The drain system is used to collect and transport condensed water separated from the extraction steam reheater, and includes a drain receiving tank, which is connected to the water side of the high-pressure heater through a pipeline, and a drain regulating valve is arranged on the pipeline. These condensed waters are sent back to the water side of the high-pressure heater through a drainage pipeline, and the residual heat of the drain is used to heat the feed water, thereby realizing recycling. The high-pressure heater is used to heat the feed water or recover the heat of steam, and it receives the exhaust steam from the extraction steam reheater to increase the temperature of the feed water. Exhaust steam refers to steam that has completed work in the steam turbine, and its pressure and temperature are reduced to become wet steam or saturated steam with lower temperature and pressure. The condensing device generally refers to a condenser, which is used to condense the excess exhaust steam discharged from the extraction steam reheater into water, thereby completing the collection of the excess exhaust steam. It receives the excess exhaust steam from the extraction steam reheater and condenses it.

[0034] The steam-water separation reheating system comprises: a steam extraction reheater and an exhaust pipeline, wherein the exhaust pipeline comprises a first exhaust pipeline and a second exhaust pipeline.

[0035] The extraction steam reheater is connected to the high-pressure heater through the first exhaust pipeline and to the condensing device through the second exhaust pipeline. The extraction steam reheater is also connected to the drain system for conveying the drain to the drain system. The extraction steam reheater extracts part of the steam from the steam turbine and then heats the exhaust of the high-pressure cylinder in the extraction steam reheater to reduce the humidity of the exhaust of the high-pressure cylinder. This process can increase the temperature of the exhaust of the high-pressure cylinder and reduce the humidity of the exhaust of the high-pressure cylinder, thereby improving the overall thermal efficiency of the cycle. The tube side of the extraction steam reheater is the steam extracted from the steam turbine to heat the exhaust of the high-pressure cylinder. Most of this extracted steam is condensed into water after heat exchange and discharged from the drain pipeline, and a small amount of non-condensable gas and steam is discharged from the exhaust pipeline.

[0036] Under the first operating condition, the drain discharged from the extraction steam reheater is transported to the drain system, and the steam discharged from the extraction steam reheater is transported to the steam side of the high-pressure heater through the first exhaust pipeline. Among them, the first operating condition refers to the operating condition in which the liquid level in the drain receiving tank does not exceed the preset height threshold, the valve position fluctuation of the drain regulating valve does not exceed the preset first fluctuation threshold, and the first exhaust pipeline works normally to meet the steam discharge demand. Under this operating condition, the second exhaust pipeline is not put into use. The first exhaust pipeline is a normal exhaust pipeline, connecting the extraction steam reheater and the high-pressure heater. Under the first operating condition, the exhaust steam that has done work is transported to the steam side of the high-pressure heater through the first exhaust pipeline, where it may be further utilized to heat the feed water.

[0037] Under the second operating condition, the steam discharged from the extraction reheater is transported to the steam drain system, part 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 condensing device through the second exhaust pipeline. Among them, the second operating condition includes abnormal operation of the steam-water separation reheater caused by abnormal level fluctuation of the steam in the steam drain receiving device (such as the steam drain receiving tank) in the steam drain system, fluctuation of the valve position of the steam drain regulating valve of the steam drain receiving device, etc. The second exhaust pipeline is a spare exhaust pipeline, connecting the extraction reheater and the condensing device. Under the second operating condition, part of the steam is transported to the condensing device through the second exhaust pipeline, where the part of the steam is condensed into water.

[0038] By implementing the technical solution of this embodiment, a second exhaust pipeline is added, and it is put into operation in combination with the first exhaust pipeline according to actual conditions, thereby overcoming the problem of system parameter fluctuations caused by the inability to adjust a larger flow rate when a single exhaust pipeline is used because the exhaust volume adjustment of the exhaust pipeline is limited by the orifice plate diameter. This embodiment combines the two schemes together, and flexibly adjusts the exhaust volume according to the actual needs of the system, so as to adapt to different operating conditions and load changes, and improve the flexibility and adaptability of the system; the exhaust volume can be more effectively controlled, energy loss can be reduced, the thermal efficiency of the system can be improved, and the system performance can be optimized; when the first exhaust pipeline cannot meet the exhaust demand, causing oscillation and fluctuation of parameters such as the intake flow rate, intake pressure, drain liquid level of the drain receiving tank, and drain valve position of the extraction steam reheater, the second exhaust pipeline can intervene to increase the exhaust volume of the extraction steam reheater, and reduce the oscillation and fluctuation of parameters such as the intake flow rate, intake pressure, drain liquid level of the drain receiving tank, and drain valve position of the extraction steam reheater, thereby ensuring the continuous operation of the system, reducing downtime, enhancing the reliability of the system, ensuring that the steam-water separation reheat system can operate more efficiently, successfully solving the problem of fluctuation of some parameters of the drain system, and avoiding frequent on-site inspections and interventions by various professionals during daily work, thereby reducing maintenance costs.

[0039] In a specific embodiment, a valve for controlling the opening and closing of a fluid channel and an orifice plate arranged downstream of the valve are arranged on the first exhaust pipeline. The valve is used to open and close the fluid channel, and the orifice plate adjusts the flow rate of steam in the first exhaust pipeline by changing the diameter of the expansion hole. In this embodiment, the valve and the orifice plate are arranged together on the first exhaust pipeline. The valve is mainly used to open and close the fluid channel in the first exhaust pipeline to achieve rapid response and precise control of the flow rate. The orifice plate can change the expansion hole diameter during overhaul to adjust the flow rate of steam in the first exhaust pipeline. The flow coefficient of the orifice plate and the ratio of the aperture to the pipe diameter determine the upper limit of the flow rate. The maximum flow rate of the fluid in the first exhaust pipeline can be controlled by adjusting the aperture. The orifice plate is used for continuous flow control and provides stable flow regulation. The valve and the orifice plate are combined. 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 to avoid system overload caused by sudden increase in flow rate, and ensure the stability and reliability of the system under high concurrency.

[0040] During the overhaul, the exhaust volume that needs to be increased is calculated based on the daily valve opening, and the exhaust orifice plate of the first exhaust pipeline is expanded, so that only the first exhaust pipeline can stabilize the system after the overhaul. In this embodiment, according to the total exhaust volume of the first exhaust pipeline and the second exhaust pipeline during daily operation, according to the formula Q1 / Q2=(D1 / D2) 2 Calculate the orifice plate diameter that needs to be increased, where Q1 and Q2 are the fluid flow rates of the first exhaust pipeline and the second exhaust pipeline, 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, expand the orifice plate of the first exhaust pipeline so that after the overhaul, only the first exhaust pipeline can make the system run stably.

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

[0042] In a specific embodiment, an electric valve is provided on the second exhaust pipeline, and the electric valve is used to adjust the steam flow in the second exhaust pipeline. In this embodiment, the second exhaust pipeline is used as a spare exhaust pipeline, and the flow can be gradually increased when needed. Therefore, the electric valve can achieve precise flow regulation by using valve control. The flow of the fluid in the second exhaust pipeline is adjusted by changing the opening of the valve. This regulation is more accurate and flexible than the traditional orifice plate regulation. By gradually increasing the flow of the second exhaust pipeline, the exhaust capacity of the system can be more effectively utilized, energy loss can be reduced, and the thermal efficiency of the entire system can be improved.

[0043] like Figure 2 As shown, in a specific embodiment, the exhaust pipeline also includes: a third exhaust pipeline, the extraction steam reheater and the condensing device are also connected through the third exhaust pipeline, and under the third operating condition, the drain discharged from the extraction steam reheater is transported to the drain system, and the steam discharged from the extraction steam reheater is transported to the condensing device 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 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 device, and transporting steam to the condensing device through the third exhaust pipeline.

[0045] Implementation of the technical solution of this embodiment can ensure that the steam-water separation reheat system can operate effectively when the turbine is in a low-power state, thereby preventing safety hazards caused by excessive pressure or steam accumulation, ensuring the safe operation of the reactor and the turbine, improving the efficiency of the thermal cycle, reducing energy losses, and maintaining a high thermal economy even in a low-power state.

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

[0047] The extraction steam reheater is connected to the high-pressure heater through the first exhaust pipeline ①, and the first exhaust pipeline ① is provided with a valve 226VV and an orifice plate 204DI; the extraction steam reheater is connected to the condenser through the second exhaust pipeline ② and the third exhaust pipeline ③, and the second exhaust pipeline ② is provided with an electric valve 225VV and an orifice plate 204DI, and the third exhaust pipeline ③ is provided with an electric valve 206VV and an orifice plate 202DI; the condenser is connected to the drain receiving tank through the drainage pipeline ⑤, and the extraction steam reheater is connected to the drain receiving tank through the drainage pipeline ⑥. A special exhaust pipeline ⑦ is also designed between the extraction steam reheater and the drain receiving tank to provide continuous exhaust flow so that the temperature difference of the heat transfer tube is maintained at an acceptable level; the drain receiving tank is connected to the water side of the high-pressure heater through the drainage pipeline ④, and a drain regulating valve 212VL is provided on the drainage pipeline.

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

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

[0050] The present invention further provides an exhaust method for a steam-water separation and reheating system of a nuclear power plant, which is applied to the steam-water separation and reheating system of the nuclear power plant in the above embodiment and comprises the following steps:

[0051] S1. Determine whether the conditions of the first operating condition are met. If so, control the steam to be transported 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 an operating condition in which the liquid level in the drain receiving tank does not exceed the preset height threshold, the valve position fluctuation of the drain regulating valve does not exceed the preset first fluctuation threshold, and the first exhaust pipeline works normally to meet the steam emission demand. Under this operating condition, the second exhaust pipeline and the third exhaust pipeline are not put into use.

[0053] S2. Determine whether the conditions of the second operating condition are met. If so, control part 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 condensing device through the second exhaust pipeline.

[0054] Under the second operating condition, since the flow rate of the first exhaust pipeline cannot be adjusted, the exhaust volume of the first exhaust pipeline alone cannot meet the requirements, and the first and second exhaust pipelines need to be used at the same time. Therefore, it is necessary to gradually increase the opening of the second exhaust pipeline while keeping the opening of the first exhaust pipeline unchanged, so as to increase the steam exhaust volume of the entire steam-water separation reheat system.

[0055] In a specific embodiment, a second exhaust pipeline is added, and the opening of the standby pipeline is increased according to the fluctuation of system parameters, so that the system reaches a new stable state. The first exhaust pipeline and the second exhaust pipeline are put into operation in combination according to actual conditions.

[0056] In this embodiment, the second exhaust pipeline is put into use according to actual needs. The exhaust volume can be flexibly adjusted according to the actual needs of the system by adjusting the opening of the second exhaust pipeline, so as to adapt to different operating conditions and load changes and improve the flexibility and adaptability of the system; the exhaust volume can be more effectively controlled, energy loss can be reduced, the thermal efficiency of the system can be improved, and the system performance can be optimized; when the first exhaust pipeline cannot meet the exhaust demand, the second exhaust pipeline can intervene to ensure the continuous operation of the system, reduce downtime, and enhance the reliability of the system.

[0057] In an optional embodiment, controlling part of the steam to be transported to the steam side of the high-pressure heater through the first exhaust pipeline, and controlling the remaining steam to be transported to the condensing device through the second exhaust pipeline includes: S21: keeping the steam discharge amount of the first exhaust pipeline unchanged, 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 of the second exhaust line is an electric valve. When the second operating condition is met, the valve is opened at a 5% amplitude, and the fluctuation of the liquid level and valve position is observed at the same time. The fluctuation returns to normal to maintain the current opening. The technical solution of this embodiment can ensure that the steam-water separation reheat system maintains safety and efficiency while meeting the operating conditions, avoid potential risks caused by excessive or insufficient valve opening, and better control the steam-water separation reheat system to ensure the stability and safety of the system under different operating conditions. At the same time, this also helps to extend the service life of the equipment and reduce the possibility of failure.

[0059] The conditions for the second operating condition include the following three. When any one of the conditions is met, it is considered that the second operating condition is met.

[0060] In a 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 drain system, and the height of the drain in the drain receiving tank in the drain system can be obtained. The steam-water separation reheat system of the nuclear power plant is mainly responsible for utilizing the exhaust steam discharged from the steam turbine. This part of the exhaust steam will heat the exhaust gas of the high-pressure cylinder through the extraction steam reheater, increase the temperature of the exhaust gas, and reduce the humidity of the exhaust gas. After completing the work in the extraction steam reheater, the remaining steam and drain are discharged to the steam side and water side of the high-pressure heater respectively for recycling.

[0062] In this embodiment, after the liquid level in the drain receiving tank exceeds the preset liquid level threshold, the steam-water separation reheat system puts the second exhaust pipeline into use, controls part of the exhaust steam to be discharged directly to the condensing device, ensures that the rate of increase of the liquid level in the drain receiving tank is reduced, and avoids potential safety risks and equipment damage.

[0063] In another specific embodiment, the drainage system discharges drainage through a drainage pipeline, and a drainage control valve is provided on the drainage pipeline. Determining whether the condition of 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 does not converge within a preset time, and if so, determining that the condition of the second operating condition is met.

[0064] In this embodiment, when the valve position fluctuation of the drain regulating valve exceeds the preset first fluctuation threshold and cannot converge within the specified time, the steam-water separation reheat system will determine that the drain regulating valve has lost regulation, and output an alarm at this time to remind the staff to intervene in advance, so as to eliminate risks in advance. Among them, if the valve position fluctuation of the drain regulating valve is less than the first fluctuation threshold, it is judged that the drain regulating valve has not lost regulation. If the valve position fluctuation of the drain regulating valve exceeds the first fluctuation threshold, but converges again within the specified time, it is judged that the drain regulating valve has not lost regulation. If the valve position fluctuation of the drain regulating valve exceeds the first fluctuation threshold and does not converge within the specified time, it is judged that the drain regulating valve has lost regulation. The technical solution of this embodiment can timely remind the staff to intervene in advance when the drain regulating valve may lose regulation, so as to timely discover potential faults and repair them, thereby avoiding the problem of excessive liquid level in the drain receiving tank.

[0065] In another specific embodiment, the drainage system discharges drainage through a drainage pipeline, and a drainage control valve is provided on the drainage pipeline. Determining whether the condition of 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, and if so, determining that the condition of the second operating condition is met, wherein the second fluctuation threshold is greater than the first fluctuation threshold.

[0066] In this embodiment, when the valve position fluctuation of the steam trap regulating valve exceeds the preset second fluctuation threshold, the low liquid level alarm in the steam trap receiving tank will be frequently triggered, affecting the normal operation of the steam extraction reheater of the steam-water separation reheat system, causing excessive wear of the valve packing of the steam trap regulating valve, and forming a vicious cycle. The technical solution of this embodiment can timely adjust the liquid level height in the steam trap receiving tank when the valve position fluctuation of the steam trap regulating valve exceeds the preset second fluctuation threshold, reduce the discharge burden of the steam trap regulating valve, and avoid frequent alarms in the steam-water separation reheat system, which requires frequent maintenance by staff.

[0067] S3. Determine whether the conditions of the third operating condition are met. If so, control the steam to be transported to the condensing device through the third exhaust pipeline. In a specific embodiment, when the power of the steam turbine of the nuclear power plant is lower than a 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 transported to the condensing device through the third exhaust pipeline.

[0068] Implementation of the technical solution of this embodiment can ensure that the steam-water separation reheat system can operate effectively when the turbine is in a low-power state, thereby preventing safety hazards caused by excessive pressure or steam accumulation, ensuring the safe operation of the reactor and the turbine, improving the efficiency of the thermal cycle, reducing energy losses, and maintaining a high thermal economy even in a low-power state.

[0069] In the existing technology, the steam-water separation reheat system of a nuclear power plant in my country has experienced oscillations and fluctuations in various parameters including air intake flow, air intake pressure, drain level, drain valve position, etc., which are manifested as fluctuations in the downstream regulating valve position of the drain receiving tank, fluctuations in the drain receiving tank liquid level, and synchronous fluctuations in the exhaust flow and exhaust pressure of the first-stage reheater of the steam-water separation reheat system. After long-term on-site tracking and routine overhaul and maintenance, it was found that the cause of the accident was the low exhaust pressure and drain pressure of the exhaust pipeline of the steam-water separation reheat system, insufficient exhaust, and unstable exhaust, which caused fluctuations in system parameters.

[0070] The nuclear power plant applies the technical solution of the present invention, optimizes the operation mode of existing equipment during daily operation, gradually increases the opening of the second exhaust pipeline, increases the exhaust volume, and maintains the opening of the second exhaust pipeline when the fluctuation range is acceptable. During the overhaul, the exhaust volume of the first exhaust pipeline is increased by expanding the orifice plate, so that the exhaust volume of the first exhaust pipeline can meet daily needs.

[0071] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, the above technical features can be freely combined without departing from the concept of the present invention, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the coverage of the claims of the present invention.

Claims

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

2. The steam-water separation and reheating system according to claim 1, characterized in that: The first exhaust pipeline is provided with a valve for controlling the opening and closing of a fluid channel and an orifice plate arranged downstream of the valve, wherein the valve is used to open and close the fluid channel, and the orifice plate adjusts the flow rate of steam in the first exhaust pipeline by changing the diameter of the expanded hole.

3. The steam-water separation and reheating system according to claim 1, characterized in that: The second exhaust pipeline is provided with an electric valve, and the electric valve is used to adjust the flow rate of steam in the second exhaust pipeline.

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

5. An exhaust method for a steam-water separation and reheating system of a nuclear power plant, applied to the steam-water separation and reheating system of a nuclear power plant according to any one of claims 1 to 4, characterized in that: include: S1, determining whether the conditions of the first operating condition are met, and if so, controlling the steam to be transported to the steam side of the high-pressure heater through the first exhaust pipeline; S2, judging whether the conditions of the second operating condition are met, and if so, controlling part of the steam to be transported to the steam side of the high-pressure heater through the first exhaust pipeline, and controlling the remaining steam to be transported to the condensing device through the second exhaust pipeline; S3. Determine whether the conditions of the third operating condition are met. If so, control the steam to be transported to the condensing device through the third exhaust pipeline.

6. The exhaust method according to claim 5, characterized in that: The drain system includes a drain receiving tank, and the condition for determining whether the second operating condition is met includes: Monitor the liquid level of the liquid in the hydrophobic receiving tank to determine whether the liquid level exceeds a preset height threshold, and if so, determine that the conditions of the second operating condition are met.

7. The exhaust method according to claim 5, characterized in that: The drainage system discharges drainage through a drainage pipeline, and a drainage control valve is provided on the drainage pipeline. The conditions for determining whether the second operating condition is met include: Monitor the valve position fluctuation of the drainage control valve to determine whether the valve position fluctuation exceeds a preset first fluctuation threshold and fails to converge within a preset time. If so, determine that the conditions for the second operating condition are met.

8. The exhaust method according to claim 5, characterized in that: The drainage system discharges drainage through a drainage pipeline, and a drainage control valve is provided on the drainage pipeline. The conditions for determining whether the second operating condition is met include: Monitor the valve position fluctuation of the drainage control valve to determine whether the valve position fluctuation exceeds a preset second fluctuation threshold, and if so, determine that the conditions for the second operating condition are met.

9. The exhaust method according to claim 5, characterized in that: The condition for determining whether the third operating condition is met includes: Monitor the operating power of the reactor to determine whether the operating power is lower than a preset power threshold, and if so, determine that the conditions for the third operating condition are met.

10. The exhaust method according to claim 5, characterized in that: The controlling part of the steam to be transported to the steam side of the high pressure heater through the first exhaust pipeline, and the controlling the remaining steam to be transported to the condensing device through the second exhaust pipeline comprises: S21: Keep the steam flow rate of the first exhaust pipeline unchanged, 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 when the second operating condition ends.

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