Water supply control system and method for coupling power generation device of thermal power plant

Abstract

The invention belongs to the technical field of steam turbine water supply systems, and discloses a water supply control system and method for a coupling power generation device of a thermal power plant. The water supply control system comprises a steam-driven water supply pump driven by a water supply pump steam turbine, a water supply pipeline connected with a boiler is arranged at an outlet of the steam-driven water supply pump, and the steam-driven water supply pump is used for conveying water in a deaerator to the boiler; the water supply pipeline is connected with a recirculation pipeline serving as a branch, the other end of the recirculation pipeline is communicated and connected with the interior of the deaerator, and a first regulating valve is arranged on the recirculation pipeline; the water-turbine generator set comprises a water turbine and a first generator, the water turbine is arranged on the recirculation pipeline in series, and the water turbine is located on the side, away from the deaerator, of the first adjusting valve; the problems that in the prior art, when a recirculation pipeline adjusting valve is opened for guaranteeing safe operation of the water feeding pump under the low load, high-pressure water feeding energy is wasted, and the recirculation pipeline adjusting valve is eroded and damaged are effectively solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steam turbine feedwater system, and particularly relates to a feedwater control system and method for a cogeneration device of a thermal power plant. BACKGROUND

[0002] Under the requirements of the "double carbon" goal and the new generation of coal-fired power plant upgrading policy, thermal power units are more frequently deep peak shaving and start-stop peak shaving. In order to ensure the safety of operation, the speed of the steam-driven feedwater pump should be higher than the critical speed of the steam turbine driving the steam-driven feedwater pump during operation. This results in the need to open the feedwater pump recirculation valve when the unit is running at low load (e.g. below 50% rated load), thereby causing a large amount of loss. In addition, in order to ensure the efficient operation of the unit, the newly built units currently use a single 100% capacity steam-driven feedwater pump, but the deep peak shaving operating condition is not considered during construction. Therefore, in order to ensure the efficient operation of the feedwater pump, the feedwater pump head curve is designed to be relatively flat, which causes the feedwater flow to fluctuate greatly when the unit load decreases to a certain extent, which directly threatens the safety of the boiler, especially for the 1000MW unit with secondary reheat, which often needs to open the recirculation valve when the load decreases to 65% or below to ensure the safety of the unit operation. However, the opening of the regulating valve will result in the waste of the potential energy of the high-pressure feedwater, causing large throttling loss and increasing the energy consumption of the feedwater pump turbine, thereby reducing the economy of the unit. Secondly, the valve core of the recirculation valve is eroded due to long-term scouring, resulting in a loose valve and serious internal leakage, which not only causes energy loss, but also threatens the reliability and safety of the system. Therefore, in the prior art, when the recirculation pipe regulating valve is opened to ensure the safe operation of the feedwater pump at low load, there are problems of waste of high-pressure feedwater energy and erosion damage of the recirculation pipe regulating valve. SUMMARY

[0003] In view of the deficiencies of the prior art, the purpose of the present application is to provide a feedwater control system and method for a cogeneration device of a thermal power plant, which solves the problem of waste of high-pressure feedwater energy and erosion damage of the recirculation pipe regulating valve when the recirculation pipe regulating valve is opened to ensure the safe operation of the feedwater pump at low load in the prior art.

[0004] The purpose of the present application can be achieved by the following technical solutions: A feedwater control system for a cogeneration device of a thermal power plant, comprising a steam-driven feedwater pump driven by a feedwater pump turbine, a feedwater pipe connected to a boiler is arranged at the outlet of the steam-driven feedwater pump, the steam-driven feedwater pump is used to deliver water in a deaerator to the boiler, a recirculation pipe as a branch is connected to the feedwater pipe, the other end of the recirculation pipe is connected to the inside of the deaerator, a first regulating valve is arranged on the recirculation pipe, and the feedwater control system further comprises a hydroelectric generating unit, a monitoring module and a control unit. The water turbine generator set comprises a water turbine and a first generator, the water turbine is arranged in series on a recirculation pipeline, and the water turbine is located on a side of the first regulating valve away from the deaerator, water flowing through the recirculation pipeline can drive the water turbine to rotate, and an output shaft of the water turbine is coaxially connected with an input shaft of the first generator; The monitoring module is installed at the outlet of the steam-driven feed water pump and is used to monitor the flow data of the outlet of the steam-driven feed water pump. The control unit is in communication connection with the monitoring module and is in electrical connection with the first regulating valve and the water turbine, is used to receive the flow data collected by the monitoring module, and controls the opening degree of the first regulating valve and the opening degree of the guide vane in the water turbine according to the flow data.

[0005] Further, the output shaft of the water turbine and the input shaft of the first generator are connected through an SSS clutch.

[0006] Further, the first generator is a double-shaft generator, one end of the output shaft of the feed water pump turbine is connected with the steam-driven feed water pump, and the other end of the output shaft of the feed water pump turbine is coaxially connected with the input shaft of the first generator away from the SSS clutch through a shaft coupling.

[0007] Further, a recirculation bypass as a bypass is further connected on the recirculation pipeline, both ends of the recirculation bypass are in through connection with the recirculation pipeline, and a second regulating valve is arranged on the recirculation bypass. The two connection positions of the recirculation bypass and the recirculation pipeline are respectively a first node and a second node, and the first node is located on a side close to the outlet of the steam-driven feed water pump. The first recirculation pipeline is provided with a first stop valve and a second stop valve located between the first node and the second node, and the water turbine and the first regulating valve are located between the first stop valve and the second stop valve.

[0008] Further, a third stop valve is further arranged on the recirculation pipeline, and the third stop valve is located on a side close to the outlet of the steam-driven feed water pump.

[0009] Further, the monitoring module comprises a flow sensor and a pressure sensor fixedly installed at the outlet of the steam-driven feed water pump.

[0010] Further, one end of the output shaft of the feed water pump turbine is connected with the steam-driven feed water pump, and the other end of the output shaft of the feed water pump turbine is coaxially connected with the second generator.

[0011] A feed water control method of a coupled power generation device of a thermal power plant, adopts the feed water control system of the coupled power generation device of the thermal power plant to control feed water, comprising the following steps: Real-time monitoring and collection of flow data at the outlet of the steam-driven feed water pump are acquired; A recirculation starting condition is preset, and when the flow data meets the recirculation starting condition, the following steps are executed: opening the first regulating valve to a preset opening degree, so that the water at the outlet of the steam-driven feed water pump can flow back to the deaerator through the recirculation pipeline; starting the hydro-generator unit, so that the water flow in the recirculation pipeline drives the water turbine to rotate; when the water turbine reaches a predetermined rotating speed, the clutch is engaged, so that the water turbine drives the first generator to generate electricity; during the electricity generation, the following coordinated regulation steps are performed according to the real-time monitored flow data at the outlet of the steam-driven feed water pump: adjusting the opening degree of the guide vane in the water turbine, so as to control the output of the water turbine and reduce the pressure in the recirculation pipeline near the deaerator end of the water turbine; adjusting the opening degree of the first regulating valve, so as to control the flow of the steam-driven feed water pump to be stably maintained in a range higher than a preset minimum protection flow threshold value.

[0012] Further, the recirculation starting condition includes that the flow data at the outlet of the steam-driven feed water pump is lower than a preset minimum protection flow threshold value, or the flow fluctuation value of the steam-driven feed water pump outlet is greater than a preset fluctuation threshold value; Further, when the hydro-generator unit fails, the part of the recirculation pipeline between the first node and the second node is physically blocked; opening the second regulating valve in the recirculation bypass, so that the water at the outlet of the steam-driven feed water pump can flow back to the deaerator through the recirculation bypass; adjusting the opening degree of the second regulating valve, so as to control the flow of the steam-driven feed water pump to be stably maintained in a range higher than a preset minimum protection flow threshold value.

[0013] Advantages of the present application: The present application connects the hydro-generator unit in series with the recirculation pipeline, and the water turbine bears most of the pressure drop, so that the first regulating valve can work in a nearly full opening or small pressure difference condition, which fundamentally eliminates the erosion and cavitation problems of the valve core caused by high-speed water flow, greatly prolongs the service life of the valve, improves the reliability and safety of the system, and reduces the maintenance cost; at the same time, through the cooperation of the water turbine and the first generator, the pressure energy wasted by throttling through the first regulating valve in the traditional system is converted into electric energy for recycling, which directly reduces the plant power rate and significantly improves the economic efficiency of the system operation. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description, and obviously, other drawings can also be obtained by those skilled in the art without creative labor.

[0015] Figure 1This is a schematic diagram of the overall structure of the water supply control system according to Embodiment 2 of the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] like Figure 1 As shown, a feedwater control system for a coupled power generation unit in a thermal power plant includes a steam-driven feedwater pump 1 driven by a feedwater pump turbine 9. The outlet of the steam-driven feedwater pump 1 is provided with a feedwater pipeline 2 connected to the boiler 4. The steam-driven feedwater pump 1 is used to transport water from the deaerator 3 to the boiler 4. A recirculation pipeline 5, which serves as a branch line, is connected to the feedwater pipeline 2. The other end of the recirculation pipeline 5 is connected to the interior of the deaerator 3. A first regulating valve 6 is provided on the recirculation pipeline 5. The system also includes a hydro-generator set, a monitoring module 8, and a control unit. The hydro-generator set includes a turbine 71 and a first generator 72. The turbine 71 is connected in series on the recirculation pipeline 5 and is located on the side of the first regulating valve 6 away from the deaerator 3. The water flow through the recirculation pipeline 5 can drive the turbine 71 to rotate. The output shaft of the turbine 71 is coaxially connected to the input shaft of the first generator 72. The monitoring module 8 is installed at the outlet of the steam-driven feedwater pump 1 to monitor the flow rate data at the outlet of the steam-driven feedwater pump 1. The control unit is communicatively connected to the monitoring module 8, and electrically connected to the first regulating valve 6 and the turbine 71. It is used to receive the flow data collected by the monitoring module 8, and control the opening degree of the first regulating valve 6 and the opening degree of the guide vanes in the turbine 71 according to the flow data. This application connects the hydro-generator unit in series with the recirculation pipeline 5, so that the turbine 71 bears most of the pressure drop, allowing the first regulating valve 6 to operate under near-full opening or small pressure differential conditions. This fundamentally eliminates the erosion and cavitation problems of the valve core caused by high-speed water flow, significantly extends the valve's service life, improves the system's reliability and safety, and reduces maintenance costs. Meanwhile, this invention effectively recovers the high-quality pressure energy that was originally wasted by the regulating valve in the recirculation pipeline 5. The hydro-generator unit converts the 10-20MPa pressure energy that was originally consumed by the valve into electrical energy. Based on a recirculation flow rate of 400t / h for a 1000MW unit, the recoverable power reaches several thousand kilowatts. The recovered energy is converted into electrical energy and used directly for the plant power system, reducing the self-consumption rate of the unit and thus directly improving the operating economy of the thermal power unit under deep peak shaving conditions.

[0018] Preferably, the water turbine 71 can be a multi-stage centrifugal water turbine 71.

[0019] Preferably, the control unit comprises a PLC or a DCS controller.

[0020] Since the water feed pump turbine 9 will cause part of the excess power to be wasted when it is running, the water feed pump turbine 9 can be connected to a generator for secondary utilization. In this application, two different embodiments are provided, which are as follows: Embodiment one The output shaft of the water feed pump turbine 9 is connected to the steam feed pump 1 at one end, and the other end of the output shaft of the water feed pump turbine 9 is coaxially connected to the second generator; the second generator is used to utilize the excess power of the water feed pump turbine 9 and convert it into electrical energy; wherein the second generator and the output shaft of the water feed pump turbine 9 can be connected by a shaft coupling; In embodiment one, the independent first generator 72 and the second generator are used to generate electricity by the water turbine 71 and the water pump turbine, respectively.

[0021] Embodiment two As shown in Figure 1 the output shaft of the water turbine 71 is connected to the input shaft of the first generator 72 through the SSS clutch 73; the SSS clutch 73 allows the water turbine 71 arranged on the recirculation pipeline 5 to be freely put into and withdrawn without affecting the normal operation of the water feed pump turbine 9 generator set, effectively improving the flexibility of the operation mode; The first generator 72 is a double-shaft generator, the output shaft of the water feed pump turbine 9 is connected to the steam feed pump 1 at one end, and the other end of the output shaft of the water feed pump turbine 9 is coaxially connected to the input shaft of the first generator 72 away from the SSS clutch 73 through a shaft coupling; In embodiment two, due to the setting of the SSS clutch 73, the same first generator 72 can be shared and used to generate electricity by the water turbine 71 and the water feed pump turbine 9.

[0022] Preferably, the first generator 72 and the second generator can both be a permanent magnet synchronous generator.

[0023] The recirculation pipeline 5 is also connected to the recirculation bypass 10 as a bypass, both ends of the recirculation bypass 10 are connected through the recirculation pipeline 5, and the second adjusting valve 11 is arranged on the recirculation bypass 10; The two connection parts of the recirculation bypass 10 and the recirculation pipeline 5 are the first node and the second node, respectively, and the first node is located on the side close to the outlet of the steam feed pump 1; The recirculation pipeline 5 is provided with a first stop valve 12 and a second stop valve 13 between the first junction and the second junction, and the water turbine 71 and the first regulating valve 6 are located between the first stop valve 12 and the second stop valve 13. The first stop valve 12 and the second stop valve 13 are used to physically isolate the recirculation pipeline 5 between the first junction and the second junction during maintenance of the hydro-generator set. The recirculation bypass 10 and the second regulating valve 11 are used as an emergency bypass during maintenance of the hydro-generator set to ensure minimum flow protection of the feedwater pump and the feedwater flow requirement of the boiler 4.

[0024] The recirculation pipeline 5 is further provided with a third stop valve 14 located on the side of the first junction close to the outlet of the steam-driven feedwater pump 1.

[0025] Preferably, the connection part of the recirculation pipeline 5 and the feedwater pipeline 2 is taken as the circulation junction, and the feedwater pipeline 2 is further provided with a fourth stop valve 15 located on the side of the circulation junction close to the boiler 4.

[0026] The monitoring module 8 includes a flow sensor and a pressure sensor fixedly installed at the outlet of the steam-driven feedwater pump 1.

[0027] A feedwater control method of a thermal power plant coupled with a power generation device, which adopts a feedwater control system of the thermal power plant coupled with the power generation device to control feedwater, and includes the following steps: Real-time monitoring and collection of flow data at the outlet of the steam-driven feedwater pump 1 are acquired; A recirculation starting condition is preset, and when the flow data meet the recirculation starting condition, the following steps are executed: The first regulating valve 6 is opened to a preset opening degree, so that the water at the outlet of the steam-driven feedwater pump 1 can flow back to the deaerator 3 through the recirculation pipeline 5; The hydro-generator set is started, so that the water flow in the recirculation pipeline 5 drives the water turbine 71 to rotate; When the water turbine 71 reaches a predetermined rotating speed, the clutch is engaged, so that the water turbine 71 drives the first generator 72 to generate electricity; During electricity generation, the following coordinated regulation steps are executed according to the real-time monitoring of the flow data at the outlet of the steam-driven feedwater pump 1: The opening degree of the guide vane in the water turbine 71 is regulated to control the output of the water turbine 71 and reduce the pressure in the recirculation pipeline 5 close to the deaerator 3 end of the water turbine 71; The opening degree of the first regulating valve 6 is regulated to control the flow of the steam-driven feedwater pump 1 to be stably maintained in a range higher than a preset minimum protection flow threshold value; Preferably, the first regulating valve 6 is opened to a preset opening degree, and the preset opening degree is 30% opening degree; The preset minimum protection flow threshold value is 25% of the rated flow.

[0028] The recirculation start condition includes that the flow data at the outlet of the steam feed water pump 1 is lower than a preset minimum protection flow threshold value, or the fluctuation value of the outlet flow of the steam feed water pump 1 is greater than a preset fluctuation threshold value; Preferably, the fluctuation threshold value is 50 t / h.

[0029] When the hydro-generator unit fails, the partial recirculation pipeline 5 between the first node and the second node is physically blocked; The second regulating valve 11 in the recirculation bypass 10 is opened, so that the water at the outlet of the steam feed water pump 1 can flow back to the deaerator 3 through the recirculation bypass 10; The opening degree of the second regulating valve 11 is adjusted to control the flow of the steam feed water pump 1 to be stably maintained in a range higher than the preset minimum protection flow threshold value.

[0030] Taking a 1000 MW double-reheat unit with a single steam pump arrangement as an example, the unit is generally deep-regulated to a 30% load condition. Considering the critical speed of the small steam turbine and the feed water flow fluctuation problem under the low load condition, the pump inlet flow is about 1000 t / h, the pump recirculation valve is opened, the boiler 4 needs about 600 t / h of feed water, the pipeline passes through about 400 t / h of working fluid, the working fluid parameters are 140℃ and 14MPa, the equivalent power is about 1500kW, and after passing through the added hydro-generator unit, considering the comprehensive efficiency of the hydro-generator unit is about 75%, the electric energy generated per hour is about 1125kW.h, which is transmitted to the 380V bus of the auxiliary power supply to supply power to the auxiliary equipment such as lighting and water pump in the plant, realizing energy recovery and reducing the auxiliary power consumption. According to the annual deep-regulation operation hours of the unit, about 1500 hours, it is expected that the annual energy saving cost will be about 800,000 yuan. With the gradual increase of the proportion of new energy, the deep-regulation time of the basic power plant will gradually increase, and the benefits brought by the present application will be more obvious.

[0031] When the unit load increases and the feed water pump outlet flow is greater than the minimum protection flow, the control unit reverses the order, first closes the guide vane of the hydro-generator unit, and then completely closes the first regulating valve 6. The SSS clutch 73 gradually exits the recirculation mode due to the decrease of the rotating speed of the water turbine 71, and the system returns to normal operation.

[0032] When the hydro-generator unit fails, the second regulating valve 11 automatically adjusts the opening degree to track the feed water pump flow, ensuring the minimum flow protection of the feed water pump and the requirement of the boiler 4 feed water flow.

[0033] In the description of the specification, the description of the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate way in one or more embodiments or examples.

[0034] The basic principles, main features and advantages of the present application are shown and described above. Those skilled in the art should understand that the present application is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A feedwater control system for a coupled power generation unit in a thermal power plant, comprising a steam-driven feedwater pump (1) driven by a feedwater pump turbine (9), wherein the outlet of the steam-driven feedwater pump (1) is provided with a feedwater pipeline (2) connected to a boiler (4), the steam-driven feedwater pump (1) is used to transport water from a deaerator (3) to the boiler (4), a recirculation pipeline (5) serving as a branch line is connected to the feedwater pipeline (2), the other end of the recirculation pipeline (5) is connected through the interior of the deaerator (3), and a first regulating valve (6) is provided on the recirculation pipeline (5), characterized in that, It also includes a hydro-generator set, a monitoring module (8), and a control unit; The hydro-generator set includes a water turbine (71) and a first generator (72). The water turbine (71) is connected in series on the recirculation pipeline (5), and the water turbine (71) is located on the side of the first regulating valve (6) away from the deaerator (3). The water flow through the recirculation pipeline (5) can drive the water turbine (71) to rotate. The output shaft of the water turbine (71) is coaxially connected to the input shaft of the first generator (72). The monitoring module (8) is installed at the outlet of the steam-driven feedwater pump (1) to monitor the flow rate data at the outlet of the steam-driven feedwater pump (1); The control unit is connected to the monitoring module (8) and electrically connected to the first regulating valve (6) and the turbine (71) to receive the flow data collected by the monitoring module (8) and control the opening degree of the first regulating valve (6) and the opening degree of the guide vanes in the turbine (71) according to the flow data.

2. The water supply control system for the coupled power generation device in a thermal power plant according to claim 1, characterized in that, The output shaft of the water turbine (71) is connected to the input shaft of the first generator (72) via an SSS clutch (73); The control unit is also electrically connected to the SSS clutch (73) and is used to control the engagement / disengagement state of the SSS clutch (73).

3. The water supply control system for the coupled power generation device in a thermal power plant according to claim 2, characterized in that, The first generator (72) is a dual-shaft generator. One end of the output shaft of the feedwater pump turbine (9) is connected to the steam-driven feedwater pump (1), and the other end of the output shaft of the feedwater pump turbine (9) is coaxially connected to the input shaft of the first generator (72) away from the SSS clutch (73) through a coupling.

4. The water supply control system for the coupled power generation device in a thermal power plant according to claim 3, characterized in that, The recirculation pipeline (5) is also connected to a recirculation bypass (10) as a bypass. Both ends of the recirculation bypass (10) are connected to the recirculation pipeline (5). A second regulating valve (11) is provided on the recirculation bypass (10). The two connection points of the recirculation bypass (10) and the recirculation pipeline (5) are the first node and the second node, respectively. The first node is located on the side near the outlet of the steam-driven feedwater pump (1). The recirculation pipeline (5) is equipped with a first shut-off valve (12) and a second shut-off valve (13) located between the first node and the second node. The turbine (71) and the first regulating valve (6) are both located between the first shut-off valve (12) and the second shut-off valve (13).

5. The water supply control system for the coupled power generation device in a thermal power plant according to claim 4, characterized in that, A third shut-off valve (14) is also installed on the recirculation pipeline (5). The third shut-off valve (14) is located on the side of the first node near the outlet of the steam-driven feedwater pump (1).

6. The water supply control system for a thermal power plant coupled power generation device according to claim 5, characterized in that, The monitoring module (8) includes a flow sensor and a pressure sensor that are fixedly installed at the outlet of the steam-driven feedwater pump (1).

7. The water supply control system for a thermal power plant coupled power generation device according to claim 1, characterized in that, One end of the output shaft of the feedwater pump turbine (9) is connected to the steam-driven feedwater pump (1), and the other end of the output shaft of the feedwater pump turbine (9) is coaxially connected to the second generator.

8. A method for controlling the feedwater of a coupled power generation unit in a thermal power plant, comprising using the feedwater control system of the coupled power generation unit in a thermal power plant as described in claim 6, characterized in that, Includes the following steps: Obtain the flow rate data collected in real time at the outlet of the steam-driven feedwater pump (1); The pre-defined recycle restart conditions are set. When the traffic data meets the recycle restart conditions, the following steps are executed: Open the first regulating valve (6) to the preset opening degree so that the water at the outlet of the steam-driven feedwater pump (1) can flow back to the deaerator (3) through the recirculation pipeline (5). Start the water turbine generator set so that the water flow in the recirculation pipeline (5) drives the water turbine (71) to rotate; When the water turbine (71) reaches the predetermined speed, the clutch is engaged, so that the water turbine (71) drives the first generator (72) to generate electricity; During power generation, based on the real-time monitored outlet flow data of the steam-driven feedwater pump (1), the following coordinated adjustment steps are performed: Adjust the opening of the guide vanes in the turbine (71) to control the output of the turbine (71) and reduce the pressure in the recirculation pipeline (5) near the deaerator (3) of the turbine (71); Adjust the opening of the first regulating valve (6) to control the flow rate of the steam-driven feedwater pump (1) to be stably maintained within a range higher than the preset minimum protection flow threshold.

9. The water supply control method for a coupled power generation device in a thermal power plant according to claim 8, characterized in that, The recirculation start-up conditions include the flow rate data at the outlet of the steam-driven feedwater pump (1) being lower than the preset minimum protection flow rate threshold, or the fluctuation value of the outlet flow rate of the steam-driven feedwater pump (1) being greater than the preset fluctuation threshold.

10. The water supply control method for a coupled power generation device in a thermal power plant according to claim 9, characterized in that, When the hydro-generator unit fails, the recirculation pipeline (5) between the first node and the second node is physically disconnected; Open the second regulating valve (11) in the recirculation bypass (10) so that the water at the outlet of the steam-driven feedwater pump (1) can flow back to the deaerator (3) through the recirculation bypass (10). Adjust the opening of the second regulating valve (11) to control the flow rate of the steam-driven feedwater pump (1) to be stably maintained within a range higher than the preset minimum protection flow threshold.

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