A method and system for starting up and shutting down a nuclear power plant steam-water separation reheater

Abstract

The application relates to a method and system for starting and stopping a nuclear power plant steam-water separation reheater, which comprises the following steps when starting and stopping a secondary reheater: after starting a steam turbine in a nuclear power unit, monitoring the power of the unit to obtain real-time starting power of the unit; controlling the operation of the secondary reheater according to the real-time starting power and a set power; the set power is less than 900 MW; after the secondary reheater is put into operation, monitoring the running power of the unit to obtain real-time running power of the unit; and controlling the stopping of the secondary reheater according to the real-time running power and a preset stopping method. The secondary reheater is put into operation in advance when the power of the unit is less than 900 MW, which can effectively solve the problem of high steam temperature at the outlet of the steam-water separation reheater, improve the steam quality at the inlet of the low-pressure cylinder of the steam turbine, and significantly shorten the shutdown time by adopting the preset stopping method to control the secondary reheater to exit, thereby effectively improving the economic benefits of the nuclear power plant.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear power plant steam-water separation, and more particularly to a method and system for putting into operation and withdrawing a nuclear power plant steam-water separation reheater. BACKGROUND

[0002] The new steam generated by a pressurized water reactor nuclear power plant steam generator is saturated steam, and the steam continuously increases in humidity as it expands in the high-pressure cylinder, with the exhaust steam humidity of the high-pressure cylinder reaching 10% to 15%. If the exhaust steam of the high-pressure cylinder directly enters the low-pressure cylinder to do work, it will cause serious erosion and corrosion to the blades of the low-pressure cylinder, and also increase the wet steam loss, so a steam-water separation reheater is arranged between the high-pressure cylinder and the low-pressure cylinder of the nuclear power plant steam-water separation reheater system. The main functions of the steam-water separation reheater system are: 1) removing almost 98% of the water in the exhaust steam of the high-pressure cylinder; and 2) increasing the steam temperature entering the low-pressure cylinder so as to make it superheated steam.

[0003] The steam-water separation reheater is an important device in a nuclear power turbine unit, and is located after the high-pressure cylinder and before the low-pressure cylinder. The wet steam discharged from the high-pressure cylinder first passes through the separator of the steam-water separation reheater to remove water, so that the steam becomes dry saturated steam, and the separated water is discharged in time through the drain system, while the dry saturated steam enters the reheater part of the steam-water separation reheater to be reheated. The steam of the first-stage reheater (low-pressure) is sourced from the steam turbine high-pressure cylinder extraction, and the steam of the second-stage reheater (high-pressure) is sourced from the main steam. The steam-water separation reheater is arranged on both sides of the low-pressure cylinder, and the temperature difference of the steam in the outlet pipelines of the two steam-water separation reheaters during normal operation of the unit should not be greater than 17℃, and the maximum temperature difference should not exceed 28℃. The start of the second-stage reheater needs to wait for 250 min after the unit power is 30% of the load (at this time, the unit power is about 900 MW), and the unit power is lower than 35% of the load to lock the operation of the second-stage reheater. The second-stage reheater is withdrawn at a power platform between 35% and 100% of the load. This way will cause two problems in actual operation of the unit: 1) the second-stage reheater of the steam-water separation reheater is put into operation too late and withdrawn too early, which will reduce the steam quality entering the low-pressure cylinder of the nuclear power turbine; and 2) the second-stage reheater of the steam-water separation reheater is completely withdrawn at a power platform of 95% of the unit power, and still needs to wait for 6 hours, which prolongs the shutdown time, reduces the power generation of the power plant, and reduces the economic benefits. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a method and system for putting into operation and withdrawing a nuclear power plant steam-water separation reheater.

[0005] The technical scheme adopted by the present application to solve its technical problems is: a method for putting into operation or taking out of operation of a nuclear power plant steam-water separation reheater, the steam-water separation reheater comprising: a first reheater and a second reheater, the first reheater and the second reheater being connected in series between an outlet of a high-pressure cylinder and an inlet of a low-pressure cylinder, the method for putting into operation or taking out of operation of the nuclear power plant steam-water separation reheater performing the following steps when putting into operation or taking out of operation of the second reheater:

[0006] After the steam turbine in the nuclear power unit is started, the power of the unit is monitored to obtain a real-time starting power of the unit;

[0007] The second reheater is controlled to be put into operation according to the real-time starting power and in combination with a set power, the set power being less than 900 MW;

[0008] After the second reheater is put into operation, the running power of the unit is monitored to obtain a real-time running power of the unit;

[0009] The second reheater is controlled to be stopped according to the real-time running power and by using a preset shutdown method.

[0010] In the method for putting into operation or taking out of operation of the nuclear power plant steam-water separation reheater, the second reheater is controlled to be put into operation according to the real-time starting power and in combination with a set power, and the method comprises:

[0011] The real-time starting power is compared with the set power;

[0012] If the real-time starting power is greater than or equal to the set power, the second reheater is controlled to be put into operation.

[0013] In the method for putting into operation or taking out of operation of the nuclear power plant steam-water separation reheater, the method further comprises:

[0014] After the second reheater is controlled to be put into operation, the real-time starting power of the unit is continuously monitored;

[0015] It is judged whether the real-time starting power is greater than or equal to a threshold value;

[0016] If yes, a sequence control program is controlled to be started.

[0017] In the method for putting into operation or taking out of operation of the nuclear power plant steam-water separation reheater, the second reheater is controlled to be stopped according to the real-time running power and by using a preset shutdown method, and the method comprises:

[0018] It is judged whether the real-time running power decreases to a preset value;

[0019] If yes, the second reheater is controlled to be stopped by using the preset shutdown method.

[0020] In the method for starting and stopping the steam-water separation reheater of the nuclear power plant, the step of controlling the secondary reheater to stop by using the preset shutdown method comprises:

[0021] When the real-time operation power drops to the preset value, the secondary reheater is controlled to exit operation, and after a preset time period, the secondary reheater is controlled to stop operation in combination with the unit power.

[0022] In the method for starting and stopping the steam-water separation reheater of the nuclear power plant, the step of controlling the secondary reheater to stop in combination with the unit power after a preset time period comprises:

[0023] After the preset time period, the secondary reheater is controlled to exit by following the real-time operation power while dropping power until stopping by using the sequential control logic.

[0024] The application further provides a system for starting and stopping the steam-water separation reheater of the nuclear power plant, which comprises a steam-water separation reheater, wherein the steam-water separation reheater comprises a primary reheater and a secondary reheater, and the primary reheater and the secondary reheater are sequentially connected in series between the outlet of a high-pressure cylinder and the inlet of a low-pressure cylinder; and the system further comprises a control unit, wherein the control unit performs the following steps when starting and stopping the secondary reheater:

[0025] After the steam turbine in the nuclear unit is started, the power of the unit is monitored to obtain the real-time starting power of the unit;

[0026] The secondary reheater is controlled to operate according to the real-time starting power and in combination with a set power; and the set power is less than 900 MW.

[0027] After the secondary reheater is operated, the operation power of the unit is monitored to obtain the real-time operation power of the unit;

[0028] The secondary reheater is controlled to stop according to the real-time operation power and by using a preset shutdown method.

[0029] In the system for starting and stopping the steam-water separation reheater of the nuclear power plant, the control unit is specifically used for:

[0030] The real-time starting power is compared with the set power;

[0031] If the real-time starting power is greater than or equal to the set power, the secondary reheater is controlled to operate.

[0032] In the system for starting and stopping the steam-water separation reheater of the nuclear power plant, the control unit is further used for:

[0033] After the secondary reheater is controlled to operate, the real-time starting power of the unit is continuously monitored;

[0034] determining whether the real-time startup power is greater than or equal to a threshold value;

[0035] If yes, a sequence control program is started.

[0036] In the nuclear power plant steam-water separation reheater switching system, the control unit is specifically used for:

[0037] determining whether the real-time operation power drops to a preset value;

[0038] If yes, a preset shutdown method is used to control the secondary reheater to stop.

[0039] The nuclear power plant steam-water separation reheater switching method and system have the following beneficial effects: the switching method performs the following steps when switching the secondary reheater: after the steam turbine in the nuclear power unit is started, the power of the unit is monitored to obtain the real-time startup power of the unit; the secondary reheater is controlled to be put into operation according to the real-time startup power and in combination with the set power; the set power is less than 900 MW; after the secondary reheater is put into operation, the operation power of the unit is monitored to obtain the real-time operation power of the unit; and the secondary reheater is controlled to stop by using a preset shutdown method according to the real-time operation power. The secondary reheater is put into operation in advance when the power of the unit is less than 900 MW, which can effectively solve the problem of high steam temperature at the outlet of the steam-water separation reheater, improve the steam quality at the inlet of the low-pressure cylinder of the steam turbine, and significantly shorten the shutdown time by using the preset shutdown method to control the secondary reheater to exit, thereby effectively improving the economic benefits of the nuclear power plant. BRIEF DESCRIPTION OF DRAWINGS

[0040] The present application will be further described below in combination with the drawings and examples, in which:

[0041] Figure 1 is a flowchart of the nuclear power plant steam-water separation reheater switching method provided by the present application;

[0042] Figure 2 is a secondary reheater operation curve diagram of the existing nuclear power plant steam-water separation reheater;

[0043] Figure 3 is a secondary reheater exit curve diagram of the existing nuclear power plant steam-water separation reheater;

[0044] Figure 4 is a secondary reheater operation curve diagram of the nuclear power plant steam-water separation reheater provided by the present application;

[0045] Figure 5 is a secondary reheater exit curve diagram of the nuclear power plant steam-water separation reheater provided by the present application. DETAILED DESCRIPTION

[0046] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0047] Figure 1 A flow chart of a preferred embodiment of the method for starting and stopping the nuclear power plant steam-water separation reheater provided by the present application is shown. The method for starting and stopping the nuclear power plant steam-water separation reheater can solve the problem of large steam temperature difference at the outlet of the steam-water separation reheater during the start and stop of the nuclear power plant (steam turbine), and can also improve the economic benefits of the nuclear power plant.

[0048] Specifically, the steam-water separation reheater comprises a first reheater and a second reheater. The first reheater and the second reheater are connected in series between the outlet of the high-pressure cylinder and the inlet of the low-pressure cylinder. It should be noted that the starting and stopping of the first reheater will not cause the problem of large steam temperature difference at the outlet of the steam-water separation reheater, and therefore, the control of the starting and stopping of the nuclear power plant steam-water separation reheater in the present embodiment is mainly for the second reheater.

[0049] Specifically, as shown in Figure 1 the following steps are performed when the second reheater is started and stopped:

[0050] Step S101, after the steam turbine in the nuclear power unit is started, the power of the unit is monitored to obtain the real-time starting power of the unit.

[0051] In the present embodiment, the power monitoring and obtaining of the unit can be performed in the existing manner, which is not limited in the present application.

[0052] Step S102, the starting of the second reheater is controlled according to the real-time starting power and in combination with the set power. The set power is less than 900 MW.

[0053] Specifically, in the present embodiment, the starting of the steam turbine in the nuclear power unit includes normal starting after overhaul and starting after temporary stop. After the steam turbine in the nuclear power unit is started, the power of the nuclear power unit is in a gradually rising state, at this time, the real-time power (i.e. the real-time starting power) of the unit needs to be monitored in real time, and then the starting time node of the second reheater of the steam-water separation reheater is determined according to the real-time starting power of the unit.

[0054] In the present embodiment, the starting of the second reheater is controlled according to the real-time starting power and in combination with the set power, which includes comparing the real-time starting power with the set power, and if the real-time starting power is greater than or equal to the set power, the starting of the second reheater is controlled. Optionally, in the present embodiment, the set power can be 500 MW.

[0055] Further, after the secondary reheater is controlled to be put into operation, the real-time starting power of the unit is continuously monitored; it is judged whether the real-time starting power is greater than or equal to a threshold value; if yes, the sequence control program is started. Optionally, the threshold value can be set to 750 MW.

[0056] Specifically, since the secondary reheater is put into operation to heat steam when the unit power reaches 500 MW. Since the exhaust quality of the high-power platform high-pressure cylinder is reduced, the steam quality can be improved by putting the secondary reheater into operation in advance at 500 MW, thereby preventing the temperature difference high alarm in the high-power platform long load process, and effectively solving the problem of steam quality reduction caused by late input of the secondary reheater. It should be noted that in the embodiment, the start of the sequence control program can use one-key start of the steam turbine, that is, one-key starting sequence control.

[0057] Step S103, after the secondary reheater is put into operation, the operating power of the unit is monitored to obtain the real-time operating power of the unit.

[0058] Step S104, controlling the secondary reheater to stop according to the real-time operating power and using a preset shutdown method.

[0059] Specifically, in the embodiment, controlling the secondary reheater to stop according to the real-time operating power and using a preset shutdown method includes: judging whether the real-time operating power has decreased to a preset value; if yes, using the preset shutdown method to control the secondary reheater to stop. Optionally, in the embodiment, the preset value can be set to 95% of the rated power, that is, when the real-time operating power of the unit decreases to 95% load, the exit operation of the secondary reheater is performed.

[0060] Specifically, in the embodiment, using the preset shutdown method to control the secondary reheater to stop includes: when the real-time operating power decreases to the preset value, starting to control the secondary reheater to exit, and after a preset time period, controlling the secondary reheater to stop running in combination with the unit power. Wherein, after the preset time period, using sequence control logic to control the secondary reheater to exit while following the real-time operating power to decrease power until stopping.

[0061] Optionally, in this embodiment, the preset time period is 1 hour. Specifically, when the unit's real-time operating power drops to 95% load, the secondary reheater shutdown operation is initiated. After initiating the shutdown operation, the secondary reheater is controlled to maintain a slow shutdown process. Furthermore, the unit's real-time operating power remains at 95% load for 1 hour before further power reduction. During this process, the secondary reheater follows the unit's real-time operating power, simultaneously reducing power and shutting down until operation ceases. It should be noted that in this embodiment, the secondary reheater has completely shut down (i.e., completely stopped) before the unit's real-time operating power drops to 35% load.

[0062] This invention can effectively solve the problem of high steam inlet temperature in the low-pressure cylinder. At the same time, by adopting this invention, the dwell time at 95% power platform can be shortened by nearly 5 hours, and the power generation can be increased by 275MWh per shutdown, thus improving the economic efficiency of nuclear power plant operation.

[0063] Implementing this invention can shorten nuclear power turbine downtime, increase power plant output, and improve plant economics. It also solves the problem of large steam temperature differences at the outlet of the steam-water separator reheater, improves the quality of the inlet steam to the low-pressure cylinder of the nuclear power turbine, increases the superheat of the reheat steam, reduces the humidity of the exhaust steam from the low-pressure cylinder, and enhances equipment safety and reliability. Through innovative practice, the optimized operation mode of the secondary reheater has improved both the reliability of the nuclear power turbine and the steam-water separator reheater, and enhanced the operational economy of the nuclear power plant.

[0064] Specifically, such as Figure 2 The figure shown is a commissioning curve of a two-stage reheater using the existing method. Figure 4 This is a commissioning curve diagram for the two-stage reheater using the present invention.

[0065] like Figure 2 As shown, the secondary reheater was only put into operation when the unit's power reached 900MW. However, with this invention, the secondary reheater is put into operation when the unit's power reaches approximately 500MW (e.g., Figure 4 (As shown).

[0066] Figure 3 The exit curve for a two-stage reheater using the existing method. Figure 5 This is a commissioning curve of the secondary regenerator using the present invention.

[0067] Figure 3 As shown, when the unit's power drops to 95% load, the secondary reheater is shut down. However, approximately 6 hours pass before the unit's power continues to decrease. Furthermore, before the unit's power drops again after the 6-hour wait, the secondary reheater has completely shut down, further reducing the quality of the steam entering the low-pressure cylinder. With this invention, as...Figure 5 As shown, when the power of the unit is reduced to 95% load, that is, the exit operation of the secondary reheater is started, and only about 1 hour is needed to continue to reduce the power, and in the process of reducing the power of the unit, the secondary reheater is followed by the unit power to reduce the power and exit, thereby ensuring the steam quality of the low-pressure cylinder.

[0068] The application further provides a start and stop system of a nuclear power plant steam-water separation reheater, which comprises: a steam-water separation reheater, which comprises: a primary reheater and a secondary reheater, and the primary reheater and the secondary reheater are sequentially connected between the outlet of a high-pressure cylinder and the inlet of a low-pressure cylinder.

[0069] Further, the start and stop system further comprises: a control unit, which performs the following steps when starting and stopping the secondary reheater: after the steam turbine in the nuclear power unit is started, the power of the unit is monitored to obtain the real-time starting power of the unit; the secondary reheater is controlled to be put into operation according to the real-time starting power and in combination with a set power; the set power is less than 900 MW; after the secondary reheater is put into operation, the running power of the unit is monitored to obtain the real-time running power of the unit; the secondary reheater is controlled to stop by using a preset stop method according to the real-time running power.

[0070] In this embodiment, the control unit is specifically used for: comparing the real-time starting power with the set power; if the real-time starting power is greater than or equal to the set power, the secondary reheater is controlled to be put into operation.

[0071] In this embodiment, the control unit is further used for: after the secondary reheater is controlled to be put into operation, the real-time starting power of the unit is continuously monitored; it is judged whether the real-time starting power is greater than or equal to a threshold value;

[0072] If yes, the sequence control program is started.

[0073] In this embodiment, the control unit is specifically used for: judging whether the real-time running power is reduced to a preset value; if yes, the secondary reheater is controlled to stop by using a preset stop method.

[0074] Specifically, the specific cooperation operation process between each unit in the start and stop system of the nuclear power plant steam-water separation reheater can refer to the above-mentioned start and stop method of the nuclear power plant steam-water separation reheater, which will not be described here.

[0075] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts of each embodiment can be referred to each other. For the device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the related parts can be referred to the method part.

[0076] Those skilled in the art will further realize that the mere conception of the examples described herein is not inducing any patentable instrument, and that each example presents only one illustrative aspect of the present application. The present application is thus deemed to cover any and all adaptations or variations of preferred examples. It is intended to embrace each and every possible modification and change as fall within the scope of the present application. However, it is to be understood that no limitation of the scope of the application is intended by the method or algorithm steps disclosed herein. It is contemplated that those steps can be implemented by either hardware, software, or a combination of both. The order of any steps is not limited to the order disclosed herein unless specified by the context.

[0077] The steps of a method or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in RAM, flash memory, ROM, electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The processor and the storage medium can reside in an ASIC.

[0078] The embodiments described above are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it accordingly, and cannot limit the protection scope of the present application. Any equivalent changes and modifications made within the scope of the claims of the present application shall be within the scope of the claims of the present application.

Claims

1. A method for commissioning and decommissioning a steam-water separator reheater in a nuclear power plant, the steam-water separator reheater comprising: A primary reheater and a secondary reheater, wherein the primary reheater and the secondary reheater are connected in series between the outlet of the high-pressure cylinder and the inlet of the low-pressure cylinder, characterized in that the commissioning and decommissioning method of the nuclear power plant's steam-water separation reheater performs the following steps when commissioning or decommissioning the secondary reheater: After the steam turbine in the nuclear power unit is started, the power of the unit is monitored to obtain the real-time start-up power of the unit; The operation of the secondary reheater is controlled based on the real-time start-up power and a set power; the control of the secondary reheater based on the real-time start-up power and a set power includes: comparing the real-time start-up power with the set power; if the real-time start-up power is greater than or equal to the set power, then the secondary reheater is controlled to start; the set power is 500MW, wherein the unit power corresponding to waiting 250 minutes after the unit power reaches 30% load is 900MW; After the secondary reheater is put into operation, the operating power of the unit is monitored to obtain the real-time operating power of the unit; The second-stage reheater is controlled to stop based on the real-time operating power and a preset shutdown method; the step of controlling the second-stage reheater to stop based on the real-time operating power and a preset shutdown method includes: determining whether the real-time operating power has dropped to a preset value; if so, the second-stage reheater is controlled to stop using the preset shutdown method; The method of controlling the shutdown of the secondary reheater using a preset shutdown method includes: When the real-time operating power drops to a preset value, the secondary reheater is controlled to exit operation, and after a preset time period, the secondary reheater is controlled to stop operating in conjunction with the unit power; the preset value is 95% load, and the preset time period is 1 hour. The method further includes: After the secondary reheater is put into operation, the real-time start-up power of the unit continues to be monitored; Determine whether the real-time start-up power is greater than or equal to a threshold; the threshold is 750MW. If so, the control sequence program will be started.

2. The method for starting and stopping a nuclear power plant steam-water separator reheater according to claim 1, characterized in that, The step of controlling the power of the secondary reheater combined with the unit to stop operating after a preset time period includes: After a preset time period, sequential control logic is used to control the secondary reheater to gradually reduce power and exit the circuit, following the real-time operating power, until it stops.

3. A commissioning / decommissioning system for a steam-water separator reheater in a nuclear power plant, the system comprising: A steam-water separator reheater, comprising a primary reheater and a secondary reheater, wherein the primary and secondary reheaters are connected in series between the outlet of a high-pressure cylinder and the inlet of a low-pressure cylinder, characterized in that the activation / deactivation system further comprises a control unit, wherein the control unit performs the following steps when activating or deactivating the secondary reheater: After the steam turbine in the nuclear power unit is started, the power of the unit is monitored to obtain the real-time start-up power of the unit; The operation of the secondary reheater is controlled based on the real-time start-up power and a set power; the control of the secondary reheater based on the real-time start-up power and a set power includes: comparing the real-time start-up power with the set power; if the real-time start-up power is greater than or equal to the set power, then the secondary reheater is controlled to start; the set power is 500MW, wherein the unit power corresponding to waiting 250 minutes after the unit power reaches 30% load is 900MW; After the secondary reheater is put into operation, the operating power of the unit is monitored to obtain the real-time operating power of the unit; The secondary reheater is controlled to stop based on the real-time operating power and using a preset shutdown method. The step of controlling the secondary reheater to stop based on the real-time operating power and using a preset shutdown method includes: determining whether the real-time operating power has dropped to a preset value; if so, controlling the secondary reheater to stop using the preset shutdown method. The method of controlling the shutdown of the secondary reheater using a preset shutdown method includes: When the real-time operating power drops to a preset value, the secondary reheater is controlled to exit operation, and after a preset time period, the secondary reheater is controlled to stop operating in conjunction with the unit power; the preset value is 95% load, and the preset time period is 1 hour. The control unit is also used for: After the secondary reheater is put into operation, the real-time start-up power of the unit continues to be monitored; Determine whether the real-time start-up power is greater than or equal to a threshold; the threshold is 750MW. If so, the control sequence program will be started.

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