Multi-loop injection feed water recycling energy recovery system and method for nuclear power station

Abstract

The invention discloses a multi-loop injection feed water recycling energy recovery system and method for a nuclear power station. An outlet of a deaerator is communicated with a drainage medium inlet of a secondary ejector through an electric feed pump, an auxiliary steam input pipeline is communicated with an inlet of a primary ejector, and an outlet of the primary ejector is communicated with an inlet of the deaerator; a heat release side outlet of the high-pressure heater is divided into two paths, one path is communicated with an inlet of a second-stage ejector through an eighth valve group, the other path is communicated with an inlet of a deaerator through a drainage pump and a third valve group, an outlet of the drainage pump is communicated with the inlet of the second-stage ejector through a ninth valve group, an outlet of the second-stage ejector is communicated with the inlet of the deaerator, and an outlet of the second-stage ejector is communicated with the inlet of the deaerator. According to the system and the method, the high pressure of the recirculating fluid is used as power to eject the fluid with lower pressure, so that the pressure energy of the fluid is partially recovered, and the system and the method play an important role in energy conservation, consumption reduction and safety of the nuclear power station.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power engineering technology and relates to a feedwater recirculation energy recovery system and method for nuclear power plants using multi-loop ejectors. Background Technology

[0002] The secondary loop feedwater system of a nuclear power plant transfers heat from the primary loop to the feedwater via a steam generator, generating steam to drive a turbine and generate electricity. After performing work in the turbine, the steam enters the condenser and condenses into water. This water is then processed through a series of stages—condensate pump, low-pressure heater, deaerator, and high-pressure heater—before returning to the steam generator, forming a closed loop. In terms of the power unit configuration for the secondary loop feedwater system, electric feedwater pumps offer advantages over steam-driven pumps, including faster start-up and shutdown, less maintenance, and higher reliability. However, electric feedwater pumps rely on plant power, while steam-driven pumps can utilize steam generated during power generation (such as steam extracted from the high-pressure cylinder) as a power source. This results in significantly higher energy consumption for electric feedwater pumps compared to steam-driven pumps. From an economic perspective, with the continuous increase in installed capacity of nuclear power plants, improving economic efficiency has become a key issue for the sustainable development of large nuclear power units. However, given that nuclear power units prioritize safety, it is not currently feasible to completely replace electric feedwater pumps with steam-driven feedwater pumps. For example, advanced nuclear power units such as the "Hualong One," "Guohe One" large pressurized water reactors, and high-temperature gas-cooled reactors all use electric feedwater pumps. How to achieve energy-saving optimization of nuclear power plants under the existing electric feedwater pump operation mode has become a key research focus in the field of nuclear power plant operation.

[0003] The main functions of a nuclear power plant feedwater recirculation system include: 1) Ensuring the minimum flow rate of the main feedwater pump: The electric feedwater pump needs a continuous flow of a certain amount of water to remove the heat generated during operation. If the flow rate is too low, the water inside the pump will locally boil, generating bubbles. When these bubbles collapse in the high-pressure area, they will generate a huge impact force, damaging the pump impeller and casing. This phenomenon is called "cavitation." Cavitation will seriously damage the pump's performance and lifespan; 2) Adapting to variable operating conditions of the unit: During the startup, shutdown, or low-power operation of the nuclear power plant, the steam required by the turbine is very small. This flow rate may be lower than the safe operating limit of the main feedwater pump. By opening the recirculation pipeline, the small flow rate requirement of the steam generator can be met, while ensuring that the pump itself has a sufficiently large flow rate. The existing feedwater recirculation system operates as follows: feedwater is led back to the deaerator through a recirculation pipeline and recirculation regulating valve connected in parallel with the electric feedwater pump. This process irreversibly degrades the high-pressure hydraulic energy generated by the high-grade electrical energy consumed by the electric feedwater pump into low-grade heat energy through a throttling valve, and then dissipates it in the deaerator. This not only causes huge energy losses, directly translating into a waste of plant power, but also reduces the overall thermal economy of the unit. Based on the above analysis, there is currently significant room for optimization in the energy-saving, consumption-reducing, and safe operation of the secondary loop feedwater system in nuclear power plants. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a feedwater recirculation energy recovery system and method for nuclear power plants using multi-loop ejection. This system and method utilize the high pressure of the recirculated fluid as power to eject fluid at a lower pressure, thereby partially recovering its pressure energy, which plays an important role in energy saving, consumption reduction and safety of nuclear power plants.

[0005] To achieve the above objectives, this invention discloses a feedwater recirculation energy recovery system for nuclear power plants using multi-loop ejectors, comprising a deaerator, a high-pressure heater, a steam generator, an auxiliary steam input pipeline, a condensate pump, a steam turbine, a third valve group, a first-stage ejector, and a second-stage ejector. The outlet of the deaerator is divided into four paths after passing through the electric feedwater pump. The first path is connected to the heat absorption side inlet of the high-pressure heater via the first valve group; the second path is connected to the inlet of the deaerator via the second valve group; the third path is connected to the priming medium inlet of the first-stage ejector via the fourth valve group; the fourth path is connected to the priming medium inlet of the second-stage ejector via the fifth valve group; the auxiliary steam input pipeline is connected to the inlet of the first-stage ejector; and the outlet of the first-stage ejector is connected to the inlet of the deaerator. The first-stage extraction port of the steam turbine is connected to the inlet of the deaerator via the sixth valve group. The second-stage extraction port of the steam turbine is connected to the heat release side inlet of the high-pressure heater via the seventh valve group. The heat absorption side outlet of the high-pressure heater is connected to the steam generator. The heat release side outlet of the high-pressure heater is divided into two paths. One path is connected to the inlet of the second-stage ejector via the eighth valve group, and the other path is connected to the inlet of the deaerator via the condensate pump and the third valve group. The outlet of the condensate pump is connected to the inlet of the second-stage ejector via the ninth valve group. The outlet of the second-stage ejector is connected to the inlet of the deaerator.

[0006] Furthermore, both the primary ejector and the secondary ejector include an inlet section, a drainage section, an intake contraction tube, a mixing chamber, and a diffuser tube. One end of the drainage section is the inlet for the drainage medium, and the other end of the drainage section is connected to the side of the inlet section. An electric baffle is provided inside the drainage section. One end of the inlet section is the inlet, and the other end of the inlet section is inserted into the intake contraction tube and is equipped with a nozzle. The intake contraction tube is connected to the diffuser tube through the mixing chamber.

[0007] This invention discloses a method for energy recovery of feedwater recirculation in nuclear power plants using multi-loop ejectors, including unit start-up operation, unit low-load operation, unit high-load operation, first-stage ejector failure, second-stage ejector normal operation, first-stage ejector normal operation, second-stage ejector failure, and first-stage and second-stage ejector failure.

[0008] Furthermore, under the initial conditions of group startup and operation, the deaerator stores the feedwater required for unit startup, the electric feedwater pump is shut down, the auxiliary steam is shut down, the drain pump is shut down, the turbine is shut down, and the first valve group, the second valve group, the third valve group, the fourth valve group, the fifth valve group, the sixth valve group, the seventh valve group, the eighth valve group, and the ninth valve group are closed. The nuclear power plant begins startup, starting the electric feedwater pumps and activating auxiliary steam. The first, second, and fourth valve groups open and become automatic. Feedwater from the deaerator is pumped by the electric feedwater pumps and divided into three paths. The first path passes through the first valve group and the high-pressure heater before being delivered to the steam generator. The second path passes through the fourth valve group and enters the first-stage ejector, ejecting auxiliary steam before being delivered to the deaerator. The third path passes through the second valve group and is delivered to the deaerator. The first valve group automatically regulates the flow rate through the steam generator to meet the feedwater flow requirements during the unit startup phase. The fourth valve group automatically regulates the flow rate through the first-stage ejector to match the auxiliary steam supply. The remaining feedwater recirculation flow returns to the deaerator via the second valve group.

[0009] Furthermore, under the startup and operation conditions, the working process of the first-stage ejector is as follows: auxiliary steam expands and accelerates through the nozzle, and is then injected into the mixing chamber of the first-stage ejector to form a low-pressure zone. This low-pressure zone draws one line of feedwater from the electric feedwater pump through the outlet of the fourth valve group into the mixing chamber through the suction contraction pipe. High-temperature steam and low-temperature water undergo intense direct contact heat exchange and mass exchange in the mixing chamber. The steam completely condenses into the water, transferring all its heat and enthalpy to the water. The mixed water slows down in the diffuser, converting kinetic energy into pressure energy, and the pressure is restored to a level sufficient to enter the deaerator. The pressure and flow rate of the ejector feedwater are controlled by adjusting the opening of the electric baffle of the first-stage ejector to meet the feedwater pressure and temperature requirements delivered to the deaerator.

[0010] Furthermore, under low-load operating conditions, the initial state is as follows: the electric feedwater pump is running, the auxiliary steam is running, the condensate pump is shut down, the steam turbine is running, the first and fourth valve groups are put into automatic operation, and the second, third, fifth, sixth, seventh, eighth, and ninth valve groups are closed. When the unit enters a low-load operation state, the first valve group automatically adjusts the flow rate through the steam generator to meet the feedwater flow requirements under low-load operation. The fourth valve group automatically adjusts the feedwater flow rate into the first-stage ejector and adjusts the opening of the electric damper of the first-stage ejector to match the auxiliary steam supply in order to meet the feedwater pressure and temperature requirements delivered to the deaerator. When the secondary extraction steam pressure of the steam turbine reaches the pressure required to supply the high-pressure heater, the seventh valve group is opened. The secondary extraction steam from the steam turbine enters the heat release side of the high-pressure heater through the seventh valve group to heat the feedwater flowing through the tube side of the high-pressure heater, further increasing the inlet feedwater temperature of the steam generator. The fifth valve group is opened and put into automatic operation. The fifth valve group automatically regulates the feedwater flow rate entering the secondary ejector. The eighth valve group is opened to transport the condensate in the high-pressure heater to the secondary ejector. The pressure and flow rate of the ejector feedwater are controlled by adjusting the opening of the electric damper of the secondary ejector to match the condensate flow rate and pressure requirements to be supplied to the deaerator.

[0011] Furthermore, under high-load operating conditions, the initial state is as follows: the electric feedwater pump is running, the auxiliary steam is running, the condensate pump is shut down, the steam turbine is running, the first, fourth, and fifth valve groups are put into automatic operation, the seventh and eighth valve groups are open, and the second, third, sixth, and ninth valve groups are closed. When the unit enters a high-load operation state, the first valve group automatically adjusts the flow rate through the steam generator to meet the feedwater flow requirements under high-load operation of the unit. When the first-stage extraction steam pressure of the steam turbine reaches the required pressure to supply the deaerator, the sixth valve group is opened, and the first-stage extraction steam of the steam turbine enters the deaerator through the sixth valve group to meet the feedwater pressure and temperature requirements of the deaerator. The auxiliary steam is shut down, the fourth valve group is interlocked and closed, the first-stage ejector stops operating, and the electric damper of the first-stage ejector is closed. The secondary extraction steam from the turbine enters the heat release side of the high-pressure heater via the seventh valve group to heat the feedwater flowing through the heat absorption side of the high-pressure heater, further increasing the inlet feedwater temperature of the steam generator. As the amount of condensate in the high-pressure heater increases, the feedwater flow rate entering the secondary ejector is automatically adjusted by the fifth valve group. The condensate pump starts running, the ninth valve group opens, and the condensate from the outlet of the condensate pump is delivered to the secondary ejector via the ninth valve group. The eighth valve group closes, and the pressure and flow rate of the ejector feedwater are controlled by adjusting the opening of the electric damper of the secondary ejector to match the condensate flow rate and pressure requirements delivered to the deaerator. The remaining feedwater flow rate returns to the deaerator via the second valve group.

[0012] Furthermore, under the condition of a first-stage ejector failure and a second-stage ejector operating normally, the initial state is as follows: the electric feedwater pump is running, the auxiliary steam is running, the condensate pump is running, the steam turbine is running, the first valve group, the second valve group, the fourth valve group, and the fifth valve group are put into automatic operation, the seventh valve group and the ninth valve group 1 are open, and the eighth valve group, the third valve group, and the sixth valve group are closed. When a fault is detected in the primary ejector and needs to be cut off, the fourth valve group is closed, the auxiliary steam is stopped, the primary ejector is taken out of operation, and the outlet water supply of the electric feedwater pump is divided into three paths. The first path automatically adjusts the flow rate through the steam generator via the first valve group, the second path automatically adjusts the flow rate of the feedwater entering the secondary ejector via the fifth valve group, and the third path enters the deaerator via the second valve group.

[0013] Furthermore, under the condition that the first-stage ejector is operating normally and the second-stage ejector is malfunctioning, the initial state is as follows: the electric feedwater pump is running, the auxiliary steam is running, the condensate pump is running, the steam turbine is running, the first valve group, the second valve group, the fourth valve group, and the fifth valve group are put into automatic operation, the seventh valve group and the ninth valve group are open, and the eighth valve group, the third valve group, and the sixth valve group are closed. When a fault is detected in the secondary ejector and it needs to be disconnected, the third valve group is opened and put into automatic mode, the fifth and ninth valve groups are closed, the secondary ejector is taken out of operation, and the outlet condensate of the condensate pump is automatically regulated by the third valve group to deliver the condensate flow and pressure to the deaerator.

[0014] Furthermore, under the condition of failure of the first-stage ejector and the second-stage ejector, the initial state is as follows: the electric feedwater pump is running, the auxiliary steam is running, the condensate pump is running, the steam turbine is running, the first valve group, the second valve group, the fourth valve group, and the fifth valve group are put into automatic operation, the seventh valve group and the ninth valve group are open, and the eighth valve group, the third valve group, and the sixth valve group are closed. When both the primary and secondary ejectors are detected to be malfunctioning and require disconnection, the fourth valve group is closed, the auxiliary steam is stopped, and the primary ejector is taken out of operation; the fifth and ninth valve groups are closed, the secondary ejector is taken out of operation, the third valve group is opened, and the outlet water supply of the electric feedwater pump is divided into two paths: one path automatically regulates the flow rate through the steam generator via the first valve group, and the other path returns to the deaerator via the second valve group. All the outlet condensate of the condensate pump is transported to the deaerator via the third valve group.

[0015] The present invention has the following beneficial effects: The nuclear power plant energy recovery system and method using a multi-loop ejector feedwater recirculation system, as described in this invention, involves two connections at the feedwater pump recirculation outlet: a primary ejector and a secondary ejector. The primary ejector ejects auxiliary steam, while the secondary ejector ejects high-pressure heater condensate. Its working principle is as follows: after expanding and accelerating through nozzles, the heater condensate or auxiliary steam enters the intake contraction section, where it undergoes intense direct contact heat and mass exchange with a certain flow rate of recirculated feedwater in the mixing chamber. Furthermore, kinetic energy is converted into pressure energy in the diffuser, achieving successful recovery and full utilization of the recirculated feedwater's heat, resulting in significant energy savings.

[0016] Meanwhile, after some of the high-pressure recirculated feedwater flows through the first-stage ejector and the second-stage ejector to perform work, the pressure is significantly reduced before entering the deaerator. This overcomes the large impact caused by the original design of high-pressure recirculated feedwater directly entering the deaerator, which caused the deaerator water level to fluctuate.

[0017] This invention's ejector has no power unit, eliminates mechanical seal issues, and has an extremely low failure rate. The pressure and flow rate of the ejector feedwater are controlled by adjusting the opening of an electric baffle, resulting in high ejector efficiency. Under low-load operating conditions, the kinetic energy generated by the secondary ejector transports condensate to the deaerator, replacing the original design's use of a condensate pump, saving energy and improving the reliability of the condensate system. Furthermore, the multi-loop ejector system can be seamlessly connected and disconnected. If the primary or secondary ejector fails, the multi-loop ejector system can be quickly disconnected without affecting the normal operation of the original system, demonstrating high reliability and flexibility. Attached Figure Description To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flow chart of the water supply recirculation energy recovery system using multi-loop ejectors according to the present invention; Figure 2 A schematic diagram of an ejector structure with an electric baffle 1-1; Among them, 1 is the deaerator, 2 is the electric feedwater pump, 3 is the high-pressure heater, 4 is the steam generator, 5 is the auxiliary steam input pipeline, 6 is the condensate pump, 7 is the steam turbine, 8 is the first valve group, 9 is the second valve group, 10 is the third valve group, 11 is the first-stage ejector, 12 is the second-stage ejector, 13 is the fourth valve group, 14 is the fifth valve group, 15 is the sixth valve group, 16 is the seventh valve group, 17 is the eighth valve group, 18 is the ninth valve group, 1-1 is the electric baffle, 2-2 is the nozzle, 3-3 is the suction contraction pipe, 4-4 is the mixing chamber, and 5-5 is the diffuser. Detailed Implementation

[0019] 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, not all, of the embodiments of the present invention. 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.

[0020] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0021] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0022] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this invention generally indicates that the preceding and following objects have an "or" relationship.

[0023] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0024] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0027] refer to Figure 1 The nuclear power plant energy recovery system using multi-loop ejector feedwater recirculation according to the present invention includes a deaerator 1, an electric feedwater pump 2, a high-pressure heater 3, a steam generator 4, an auxiliary steam input pipeline 5, a drain pump 6, a steam turbine 7, a first valve group 8, a second valve group 9, a third valve group 10, a first-stage ejector 11, a second-stage ejector 12, a fourth valve group 13, a fifth valve group 14, a sixth valve group 15, a seventh valve group 16, an eighth valve group 17, and a ninth valve group 18; The outlet of deaerator 1 is divided into four paths after passing through electric feedwater pump 2. The first path is connected to the heat absorption side inlet of high-pressure heater 3 via first valve group 8. The second path is connected to the inlet of deaerator 1 via second valve group 9. The third path is connected to the priming medium inlet of primary ejector 11 via fourth valve group 13. The fourth path is connected to the priming medium inlet of secondary ejector 12 via fifth valve group 14. Auxiliary steam input pipe 5 is connected to the inlet of primary ejector 11. The outlet of primary ejector 11 is connected to the inlet of deaerator 1.

[0028] The first-stage extraction port of the steam turbine 7 is connected to the inlet of the deaerator 1 via the sixth valve group 15. The second-stage extraction port of the steam turbine 7 is connected to the heat release side inlet of the high-pressure heater 3 via the seventh valve group 16. The heat absorption side outlet of the high-pressure heater 3 is connected to the steam generator 4. The heat release side outlet of the high-pressure heater 3 is divided into two paths. One path is connected to the inlet of the second-stage ejector 12 via the eighth valve group 17, and the other path is connected to the inlet of the deaerator 1 via the condensate pump 6 and the third valve group 10. The outlet of the condensate pump 6 is connected to the inlet of the second-stage ejector 12 via the ninth valve group 18. The outlet of the second-stage ejector 12 is connected to the inlet of the deaerator 1.

[0029] refer to Figure 2 Both the primary ejector 11 and the secondary ejector 12 include an inlet section, a drainage section, an intake contraction tube 3-3, a mixing chamber 4-4, and a diffuser tube 5-5. One end of the drainage section is the inlet of the drainage medium, and the other end of the drainage section is connected to the side of the inlet section. An electric baffle 1-1 is provided in the drainage section. One end of the inlet section is the inlet, and the other end of the inlet section is inserted into the intake contraction tube 3-3 and then a nozzle 2-2 is provided. The intake contraction tube 3-3 is connected to the diffuser tube 5-5 through the mixing chamber 4-4.

[0030] The nuclear power plant energy recovery method using multi-loop ejector feedwater recirculation described in this invention includes the following steps: 1) Unit startup and operation conditions; Initial state: The deaerator 1 stores the feedwater required for unit startup, electric feedwater pump 2 is shut down, auxiliary steam is shut down, condensate pump 6 is shut down, steam turbine 7 is shut down, and valve groups 1, 2, 9, 3, 10, 4, 13, 5, 14, 6, 15, 7, 16, 8, and 9 are closed.

[0031] The nuclear power plant begins startup, starting the electric feedwater pump 2 and activating auxiliary steam. Valve groups 8, 9, and 13 are opened and put into automatic operation. Feedwater from deaerator 1 is pumped by electric feedwater pump 2 and divided into three paths. The first path passes through valve group 8 and high-pressure heater 3 before being delivered to steam generator 4. The second path passes through valve group 13 and enters the first-stage ejector 11, ejecting auxiliary steam before being delivered to deaerator 1. The third path passes through valve group 9 before being delivered to deaerator 1. Valve group 8 automatically regulates the flow rate through steam generator 4 to meet the feedwater flow requirements during the unit startup phase. Valve group 13 automatically regulates the flow rate through the first-stage ejector 11 to match the auxiliary steam supply. The remaining feedwater recirculation flow returns to deaerator 1 via valve group 9.

[0032] The working process of the first-stage ejector 11 is as follows: Auxiliary steam expands and accelerates through nozzle 2-2, and is injected into the mixing chamber 4-4 of the first-stage ejector 11 at extremely high speed, forming a low-pressure zone. This low-pressure zone draws one path of feedwater from the electric feedwater pump 2 through the outlet of the fourth valve group 13 into the mixing chamber 4-4 via the suction contraction pipe 3-3. High-temperature steam and low-temperature water undergo intense direct contact heat exchange and mass exchange within the mixing chamber 4-4. The steam completely condenses into the water, transferring all its heat and enthalpy to the water. The mixed water decelerates in the diffuser 5-5, converting kinetic energy into pressure energy, and the pressure is restored to a level sufficient to enter the deaerator 1. The pressure and flow rate of the ejected feedwater are controlled by adjusting the opening of the electric damper 1-1 of the first-stage ejector 11 to meet the pressure and temperature requirements of the feedwater delivered to the deaerator 1.

[0033] 2) Low-load operation of the unit; Initial state: Electric feedwater pump 2 is running, auxiliary steam is running, condensate pump 6 is stopped, steam turbine 7 is running, first valve group 8 and fourth valve group 13 are put into automatic operation, and second valve group 9, third valve group 10, fifth valve group 14, sixth valve group 15, seventh valve group 16, eighth valve group 17 and ninth valve group 18 are closed.

[0034] When the unit enters a low-load operation state, the flow rate through the steam generator 4 is automatically adjusted by the first valve group 8 to meet the feedwater flow requirements under low-load operation. The feedwater flow rate entering the first-stage ejector 11 is automatically adjusted by the fourth valve group 13, and the opening of the electric damper of the first-stage ejector 11 is adjusted to match the auxiliary steam supply in order to meet the feedwater pressure and temperature requirements delivered to the deaerator 1. When the secondary extraction steam pressure of turbine 7 reaches the pressure required to supply high-pressure heater 3, the seventh valve group 16 is opened. The secondary extraction steam of turbine 7 enters the heat release side of high-pressure heater 3 through the seventh valve group 16 to heat the feedwater flowing through the tube side of high-pressure heater 3, further increasing the inlet feedwater temperature of steam generator 4. The fifth valve group 14 is opened and put into automatic operation. The feedwater flow rate entering the secondary ejector 12 is automatically adjusted by the fifth valve group 14. The eighth valve group 17 is opened, and the condensate in high-pressure heater 3 is transported to the secondary ejector 12 through the eighth valve group 17. The pressure and flow rate of the ejected feedwater are controlled by adjusting the opening of the electric damper 1-1 of the secondary ejector 12 to match the condensate flow rate and pressure requirements of the deaerator 1.

[0035] The working process of the secondary ejector 12 is as follows: the outlet condensate of the high-pressure heater 3 expands and accelerates through nozzle 2-2, and is injected into the mixing chamber 4-4 of the secondary ejector 12 at extremely high speed, forming a low-pressure zone. This low-pressure zone draws one path of feedwater from the outlet of the electric feedwater pump 2 through the fourth valve group 13 into the mixing chamber 4-4 via the suction contraction section. The condensate and feedwater undergo intense direct contact heat exchange and mass exchange in the mixing chamber 4-4. The mixed water decelerates in the diffuser 5-5, converting kinetic energy into pressure energy. The pressure and temperature of the condensate are both increased to the target values ​​and sent to the deaerator 1. The remaining feedwater flow returns to the deaerator 1 through the second valve group 9.

[0036] 3) High-load operation of the unit; Initial state: Electric feedwater pump 2 is running, auxiliary steam is running, condensate pump 6 is stopped, steam turbine 7 is running, valve group 8, valve group 13 and valve group 14 are put into automatic operation, valve group 16 and valve group 17 are open, valve group 9, valve group 10, valve group 15 and valve group 18 are closed.

[0037] When the unit enters a high-load operation state, the flow rate through the steam generator 4 is automatically adjusted by the first valve group 8 to meet the feedwater flow requirements under high-load operation of the unit.

[0038] When the primary extraction steam pressure of turbine 7 reaches the required pressure to supply deaerator 1, the sixth valve group 15 is opened, and the primary extraction steam of turbine 7 enters deaerator 1 through the sixth valve group 15, meeting the feedwater pressure and temperature requirements of deaerator 1. Auxiliary steam is shut down, the fourth valve group 13 is interlocked and closed, the primary ejector 11 stops operating, and the electric damper of the primary ejector 11 is closed.

[0039] The secondary extraction steam from turbine 7 enters the heat release side of high-pressure heater 3 via the seventh valve group 16 to heat the feedwater flowing through the heat absorption side of high-pressure heater 3, further increasing the inlet feedwater temperature of steam generator 4. As the condensate in high-pressure heater 3 increases, the feedwater flow rate entering the secondary ejector 12 is automatically adjusted by the fifth valve group 14. Condensate pump 6 starts running, the ninth valve group 18 opens, and the outlet condensate of condensate pump 6 is delivered to the secondary ejector 12 via the ninth valve group 18. The eighth valve group 17 closes, and the pressure and flow rate of the ejected feedwater are controlled by adjusting the opening of the electric damper 1-1 of the secondary ejector 12 to match the condensate flow rate and pressure requirements delivered to deaerator 1. The remaining feedwater flow rate returns to deaerator 1 via the second valve group 9.

[0040] 4) The first-stage ejector 11 is malfunctioning, while the second-stage ejector 12 is operating normally; Initial state: Electric feedwater pump 2 is running, auxiliary steam is running, condensate pump 6 is running, steam turbine 7 is running, valve group 8, valve group 9, valve group 13, and valve group 14 are in automatic operation, valve group 16 and valve group 18 are open, valve group 17, valve group 10, and valve group 15 are closed.

[0041] When a fault is detected in the primary ejector 11 requiring disconnection, the fourth valve group 13 is closed, auxiliary steam is stopped, and the primary ejector 11 is taken out of operation. The outlet feedwater of the electric feedwater pump 2 is divided into three paths: the first path automatically regulates the flow rate through the steam generator 4 via the first valve group 8; the second path automatically regulates the feedwater flow rate into the secondary ejector 12 via the fifth valve group 14; and the third path enters the deaerator 1 via the second valve group 9.

[0042] 5) The first-stage ejector 11 is operating normally, while the second-stage ejector 12 is malfunctioning; Initial state: Electric feedwater pump 2 is running, auxiliary steam is running, condensate pump 6 is running, steam turbine 7 is running, valve group 8, valve group 9, valve group 13, and valve group 14 are in automatic operation, valve group 16 and valve group 18 are open, valve group 17, valve group 10, and valve group 15 are closed.

[0043] When a fault is detected in the secondary ejector 12 and it needs to be disconnected, the third valve group 10 is opened and put into automatic mode, the fifth valve group 14 and the ninth valve group 18 are closed, the secondary ejector 12 is taken out of operation, and the outlet condensate of the condensate pump 6 is automatically regulated by the third valve group 10 to deliver the condensate flow and pressure to the deaerator 1 to meet the condensate flow and pressure requirements.

[0044] 6) Failure condition of primary ejector 11 and secondary ejector 12; Initial state: Electric feedwater pump 2 is running, auxiliary steam is running, condensate pump 6 is running, steam turbine 7 is running, valve group 8, valve group 9, valve group 13, and valve group 14 are in automatic operation, valve group 16 and valve group 18 are open, valve group 17, valve group 10, and valve group 15 are closed.

[0045] When both primary ejector 11 and secondary ejector 12 are detected to be malfunctioning and require disconnection, the fourth valve group 13 is closed to stop the auxiliary steam operation, and the primary ejector 11 is taken out of service; the fifth valve group 14 and the ninth valve group 18 are closed, and the secondary ejector 12 is taken out of service. The third valve group 10 is opened, and the outlet water supply of the electric feedwater pump 2 is divided into two paths: one path automatically regulates the flow rate through the steam generator 4 via the first valve group 8, and the other path returns to the deaerator 1 via the second valve group 9. All the outlet condensate of the condensate pump 6 is transported to the deaerator 1 via the third valve group 10.

[0046] Example 1 Taking the 1500MW "Guohe-1" pressurized water reactor as an example, the feedwater system includes three parallel 33.3% electric constant-speed feedwater pumps, operating with two pumps in operation and one on standby. To prevent cavitation of the feedwater pumps at low flow rates, the feedwater system is equipped with a feedwater recirculation pipeline from the main feedwater pump outlet to deaerator 1 to ensure the minimum flow rate required by the feedwater pump set (approximately 886 t / h). When the feedwater flow rate is less than the minimum flow rate of the feedwater pump set, the feedwater recirculation valve automatically adjusts its opening to maintain the pump's minimum flow rate.

[0047] Under rated operating conditions, the outlet flow rate of electric feedwater pump 2 is 2735 t / h, the rated power is 2600kW, the outlet pressure is 25MPa, the operating liquid level of deaerator 1 is 1.5-2.2m, the operating pressure is 0.35-0.8MPa, the operating temperature is 130-180℃, the auxiliary steam pressure is 1.0MPa, the temperature is 180℃, and the flow rate is 30t / h.

[0048] 1) Unit startup and operation conditions Initial state: The deaerator 1 stores the required feedwater volume for unit startup (liquid level reaches 1.8m), electric feedwater pump 2 is shut down, auxiliary steam is shut down, condensate pump 6 is shut down, turbine 7 is shut down, and valve groups 1, 2, 9, 3, 10, 4, 13, 5, 14, 6, 15, 7, 16, 8, and 9 are closed.

[0049] The nuclear power plant begins startup. Electric feedwater pump 2 starts, with a power of 2600kW. Auxiliary steam is put into operation at a pressure of 1.0MPa and a temperature of 180℃. Valve group 8, valve group 9, and valve group 13 open and are put into automatic operation. Feedwater at 130℃ in deaerator 1 is pumped by electric feedwater pump 2 (pressure of 28MPa, total flow rate of 2735 t / h) and divided into three paths: The first path is pumped to steam generator 4 through valve group 8 and high-pressure heater 3. The flow rate through steam generator 4 is automatically regulated by valve group 8 to meet the feedwater flow requirements during the unit startup phase (approximately 1400 t / h). The second path enters the first-stage ejector 11 (flow rate of approximately 100 t / h) through valve group 13, ejecting auxiliary steam (flow rate of approximately 10 t / h) and pumping it to deaerator 1. The third path returns the remaining feedwater flow (approximately 1235 t / h) to deaerator 1 through valve group 9. Based on the supply of auxiliary steam, the pressure (approximately 10 MPa) and flow rate (approximately 100 t / h) of the ejector feedwater are controlled by adjusting the opening (approximately 15%) of the electric damper 1-1 of the first-stage ejector 11 to meet the feedwater pressure (approximately 0.35 MPa) and temperature (approximately 140°C) requirements delivered to the deaerator 1.

[0050] Energy-saving effect calculation of the first-stage ejector 11: The original design used an electric feedwater pump 2 to raise the pressure of 100 t / h of water from deaerator 1 (0.35 MPa) to 10 MPa, requiring approximately 268 kW of actual electrical power. Assuming a pump efficiency (pump + motor) of 80%, the actual power consumption was 335 kW. All of this 335 kW of electrical energy was wasted in the throttling valve. In the ejector design of this invention, approximately 20% (67 kW) of this 335 kW of electrical energy is used for useful work (transporting steam). The ejector design saves 107 kW of power consumption. If it operates continuously for 1000 hours / year during the start-up phase, the annual power saving is approximately 107,000 kWh, demonstrating a significant energy-saving effect.

[0051] 2) Low-load operation of the unit (load is 10%-50% of the unit's full power) Initial state: Electric feedwater pump 2 is running, auxiliary steam is running, condensate pump 6 is stopped, steam turbine 7 is running, valve group 8, valve group 9, and valve group 13 are put into automatic operation, and valve group 10, valve group 14, valve group 15, valve group 16, valve group 17, and valve group 18 are closed.

[0052] When the unit enters a low-load operation state, the electric feedwater pump 2 has a power of 2600kW. The first valve group 8 automatically adjusts the flow rate through the steam generator 4 (approximately 1400 t / h - 2000 t / h) to meet the feedwater flow requirements under low-load operation. The fourth valve group 13 automatically adjusts the feedwater flow rate into the first-stage ejector 11 (approximately 100 t / h - 150 t / h). The opening degree of the electric damper 1-1 of the first-stage ejector 11 is adjusted (approximately 15% - 30%) to match the auxiliary steam supply, so as to meet the feedwater pressure (approximately 0.5 MPa) and temperature (approximately 150℃) requirements of the feedwater delivered to the deaerator 1. When the secondary extraction steam pressure of turbine 7 reaches the required pressure to supply high-pressure heater 3 (approximately 0.5 MPa), the seventh valve group 16 is opened. The secondary extraction steam of turbine 7 (flow rate approximately 30 t / h - 70 t / h, temperature 180℃) enters the steam side of high-pressure heater 3 through the seventh valve group 16 to heat the feedwater flowing through the tube side of high-pressure heater 3, further increasing the feedwater temperature at the inlet of steam generator 4 to 180℃. The fifth valve group 14 is put into automatic operation. It automatically regulates the feedwater flow rate into the secondary ejector 12 and opens the eighth valve group 17, allowing the condensate (flow rate approximately 30 t / h - 70 t / h) from the high-pressure heater 3 to be transported to the secondary ejector 12 via the eighth valve group 17. The pressure (approximately 10 MPa) and flow rate (approximately 100 t / h - 200 t / h) of the ejector feedwater are controlled by adjusting the opening degree (approximately 10% - 20%) of the electric baffle 1-1 of the secondary ejector 12 to match the condensate flow rate (approximately 30 t / h - 70 t / h) and pressure (approximately 0.6 MPa) required for delivery to the deaerator 1. The remaining feedwater flow rate (approximately 335 t / h ~ 1235 t / h) is returned to the deaerator 1 via the second valve group 9.

[0053] Energy-saving effect calculation of the first-stage ejector 11: The original design used an electric feedwater pump 2 to raise the pressure of 100-150 t / h of water from the deaerator 1 (0.5 MPa) to 10 MPa, requiring an actual power consumption of approximately 348-548 kW. Assuming a pump efficiency (pump + motor) of 80%, the actual power consumption was 435-685 kW. The pressure energy generated by this power consumption was entirely wasted in the throttling valve. In the ejector design of this invention, approximately 20% (87-137 kW) of the pressure energy generated by this power consumption is used for useful work (steam transport). The first-stage ejector 11 design saves 130-200 kW of power consumption. If it operates continuously for 3000 hours / year during low-load operation, the annual power saving would be approximately 390,000-600,000 kWh.

[0054] Energy-saving effect calculation of the second-stage ejector 12: In the original design, the electric feedwater pump 2 delivers 200-250 t / h of water by gravity to the deaerator 1 after being throttled by a regulating valve. This energy, approximately 550-650 kW, is wasted entirely in the throttling valve. In the ejector design of this invention, about 25% (137.5-162.5 kW) of the pressure energy generated by this energy consumption is used for useful work (drainage). The two-stage ejector 12 design saves 200-250 kW of energy. If it operates continuously for 3000 hours / year during the start-up phase, the annual energy saving is approximately 600,000-750,000 kWh.

[0055] During low-load operation, the primary ejector 11 and the secondary ejector 12 can save approximately 1.04-1.35 million kWh of electricity per year. As the load increases, the energy-saving effect becomes more significant.

[0056] 3) High-load operation of the unit (load is 50%-100% of the unit's full power). Initial state: Electric feedwater pump 2 is running, auxiliary steam is running, condensate pump 6 is stopped, steam turbine 7 is running, valve group 8, valve group 9, valve group 13, and valve group 14 are put into automatic operation, valve group 16 and valve group 17 are open, valve group 10, valve group 15, and valve group 18 are closed.

[0057] When the unit enters a high-load operation state, the electric feedwater pump 2 has a power of 2600kW, and the flow rate through the steam generator 4 is automatically adjusted by the first valve group 8 (approximately 2000 t / h - 2400 t / h) to meet the feedwater flow requirements under high-load operation of the unit.

[0058] After the primary extraction steam pressure of turbine 7 reaches the required pressure to supply deaerator 1 (approximately 1.0 MPa at a temperature of 300°C), the sixth valve group 15 is opened. The primary extraction steam from turbine 7 (flow rate approximately 100 t / h - 150 t / h) enters deaerator 1 through the sixth valve group 15, meeting the feedwater pressure (approximately 0.8 MPa) and temperature (approximately 180°C) requirements of deaerator 1. Auxiliary steam is shut down, the fourth valve group 13 is closed, the primary ejector 11 stops operating, and the electric damper 1-1 of the primary ejector 11 is closed.

[0059] The secondary extraction steam from turbine 7 (flow rate approximately 70 t / h - 100 t / h, temperature 230℃) enters the heat release side of high-pressure heater 3 through the seventh valve group 16, and is used to heat the feedwater flowing through the heat absorption side of high-pressure heater 3, further increasing the inlet feedwater temperature of steam generator 4 to 200℃. As the condensate flow in the high-pressure heater 3 increases (>70 t / h), the feedwater flow rate into the secondary ejector 12 is automatically adjusted by the fifth valve group 14. The condensate pump 6 starts running, the ninth valve group 18 opens, and the condensate from the outlet of the condensate pump 6 is delivered to the secondary ejector 12 via the ninth valve group 18. The eighth valve group 17 closes, and the pressure (approximately 10 MPa) and flow rate (approximately 200 t / h - 250 t / h) of the ejector feedwater are controlled by adjusting the opening of the electric baffle 1-1 of the secondary ejector 12 to match the condensate flow rate (approximately 70 t / h - 90 t / h) and pressure (approximately 0.8 MPa) required to be delivered to the deaerator 1. The remaining feedwater flow rate (approximately 135 t / h ~ 635 t / h) is returned to the deaerator 1 via the second valve group 9.

[0060] Energy-saving effect calculation of the second-stage ejector 12: In the original design, the electric feedwater pump 2, with a flow rate of 100-200 t / h, flows by gravity into the deaerator 1 after being throttled by a regulating valve. This energy, approximately 250-350 kW, is wasted entirely in the throttling valve. In the ejector design of this invention, about 25% (62.5-87.5 kW) of the pressure energy generated by this energy consumption is used for useful work (drainage). The two-stage ejector 12 design saves 80-135 kW of energy consumption. If it operates continuously for 4000 hours / year during the start-up phase, the annual energy saving is approximately 320,000-540,000 kWh, demonstrating a significant energy-saving effect.

[0061] 4) First-stage ejector 11 malfunction, second-stage ejector 12 operating normally. Initial state: Electric feedwater pump 2 is running, auxiliary steam is running, condensate pump 6 is running, steam turbine 7 is running, valve group 8, valve group 9, valve group 13, and valve group 14 are in automatic operation, valve group 16 and valve group 18 are open, valve group 17, valve group 10, and valve group 15 are closed.

[0062] When a fault is detected in the primary ejector 11 and it needs to be shut off, the fourth valve group 13 is quickly closed, the auxiliary steam is stopped, the primary ejector 11 is taken out of operation, and the outlet water supply of the electric feedwater pump 2 is divided into three paths: the first path automatically adjusts the flow rate through the steam generator 4 (approximately 1400t / h-2400t / h) via the first valve group 8; the second path automatically adjusts the flow rate of the feedwater entering the secondary ejector 12 (approximately 100t / h-200t / h) via the fifth valve group 14; and the third path (approximately 235t / h-1235t / h) enters the deaerator 1 via the second valve group 9.

[0063] 5) Normal operation of primary ejector 11 and failure of secondary ejector 12 Initial state: Electric feedwater pump 2 is running, auxiliary steam is running, condensate pump 6 is running, steam turbine 7 is running, valve group 8, valve group 9, valve group 13, and valve group 14 are in automatic operation, valve group 16 and valve group 18 are open, valve group 17, valve group 10, and valve group 15 are closed.

[0064] When a malfunction is detected in the secondary ejector 12 requiring disconnection, the third valve group 10 is opened and put into automatic mode, while the fifth valve group 14 and the ninth valve group 18 are quickly closed, and the secondary ejector 12 is taken out of operation. The condensate from the outlet of the condensate pump 6 is automatically regulated by the third valve group 10 to deliver condensate to the deaerator 1 at a flow rate (approximately 30t / h-90t / h) and pressure (approximately 0.6 MPa-0.8 MPa).

[0065] 6) Failure conditions of primary ejector 11 and secondary ejector 12 Initial state: Electric feedwater pump 2 is running, auxiliary steam is running, condensate pump 6 is running, steam turbine 7 is running, valve group 8, valve group 9, valve group 13, and valve group 14 are in automatic operation, valve group 16 and valve group 18 are open, valve group 17, valve group 10, and valve group 15 are closed.

[0066] When both primary ejector 11 and secondary ejector 12 are detected to be malfunctioning and require disconnection, the fourth valve 13 is quickly closed, auxiliary steam is stopped, and primary ejector 11 is taken out of operation; the fifth valve group 14 and the ninth valve group 18 are quickly closed, and secondary ejector 12 is taken out of operation. The third valve group 10 is quickly opened, and the outlet feedwater of the electric feedwater pump 2 is divided into two paths. One path automatically regulates the flow rate through the steam generator 4 (approximately 1400t / h-2400t / h) via the first valve group 8, and the other path (approximately 335t / h-1335t / h) returns to the deaerator 1 via the second valve group 9. All the outlet condensate (approximately 30t / h-90t / h) of the condensate pump 6 is transported to the deaerator 1 via the third valve group 10.

[0067] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and disclosure of the invention. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0068] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

[0069] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A nuclear power plant feedwater recirculation energy recovery system employing multiple loop eduction, characterized by, The device comprises a deaerator (1), a high-pressure heater (3), a steam generator (4), an auxiliary steam input pipeline (5), a steam pump (6), a steam turbine (7), a third valve group (10), a first-stage ejector (11) and a second-stage ejector (12). The outlet of the deaerator (1) is connected to the inlet of the high-pressure heater (3) through the first valve group (8) after being pumped by the electric feed water pump (2), and is connected to the inlet of the deaerator (1) through the second valve group (9), is connected to the inlet of the first-stage ejector (11) through the fourth valve group (13), is connected to the inlet of the second-stage ejector (12) through the fifth valve group (14), and is connected to the inlet of the first-stage ejector (11) through the auxiliary steam input pipeline (5). The first-stage steam extraction port of the steam turbine (7) is connected to the inlet of the deaerator (1) through the sixth valve group (15), the second-stage steam extraction port of the steam turbine (7) is connected to the inlet of the high-pressure heater (3) through the seventh valve group (16), the heat-absorbing side outlet of the high-pressure heater (3) is connected to the steam generator (4), the heat-releasing side outlet of the high-pressure heater (3) is connected to the inlet of the second-stage ejector (12) through the eighth valve group (17), and the outlet of the steam pump (6) is connected to the inlet of the second-stage ejector (12) through the third valve group (10) and the ninth valve group (18).

2. The nuclear power plant feedwater recirculation energy recovery system employing multiple loops of ejectors of claim 1, wherein, The first-stage ejector (11) and the second-stage ejector (12) each comprise an inlet section, a flow guiding section, an air suction contraction pipe (3-3), a mixing chamber (4-4) and a diffuser pipe (5-5), one end of the flow guiding section is a flow guiding medium inlet, the other end of the flow guiding section is connected to the side surface of the inlet section, the flow guiding section is provided with an electric baffle (1-1), one end of the inlet section is an inlet, the other end of the inlet section is provided with a nozzle (2-2) after being inserted into the air suction contraction pipe (3-3), and the air suction contraction pipe (3-3) is connected to the diffuser pipe (5-5) through the mixing chamber (4-4).

3. A method for energy recovery of feedwater recirculation by multiple loop eduction in a nuclear power plant, characterized by, The nuclear power plant adopts the multi-loop ejector-based feed water recirculation energy recovery system according to claim 2, which comprises a group start-up operation condition, a unit low-load operation condition, a unit high-load operation condition, a first-stage ejector (11) fault, a second-stage ejector (12) normal operation condition, a first-stage ejector (11) normal operation, a second-stage ejector (12) fault condition and a first-stage ejector (11) and second-stage ejector (12) fault condition.

4. The method for feedwater recirculation energy recovery using multiple loops induction of a nuclear power plant according to claim 3, characterized in that, In the unit startup operation condition, the initial state: the deaerator (1) stores the feed water required for unit startup, the electric feed water pump (2) is stopped, the auxiliary steam is stopped, the drain pump (6) is stopped, the steam turbine (7) is stopped, the first valve group (8), the second valve group (9), the third valve group (10), the fourth valve group (13), the fifth valve group (14), the sixth valve group (15), the seventh valve group (16), the eighth valve group (17) and the ninth valve group (18) are closed; The nuclear power plant starts to start, the electric feed water pump (2) is started, the auxiliary steam is put into operation, the first valve group (8), the second valve group (9) and the fourth valve group (13) are opened and put into automatic, the feed water in the deaerator (1) is delivered by the electric feed water pump (2) and then divided into three paths, wherein the first path is delivered to the steam generator (4) through the first valve group (8) and the high-pressure heater (3), the second path enters the primary ejector (11) through the fourth valve group (13), and the auxiliary steam is delivered to the deaerator (1) after being injected, and the third path is delivered to the deaerator (1) through the second valve group (9); the flow through the steam generator (4) is automatically adjusted by the first valve group (8) to meet the feed water flow demand of the steam generator (4) in the unit startup stage; the flow in the primary ejector (11) is automatically adjusted by the fourth valve group (13) to match the supply amount of the auxiliary steam, and the remaining feed water recirculation flow is returned to the deaerator (1) through the second valve group (9).

5. The method for feedwater recirculation energy recovery using multiple loops of nuclear power plant employing eductors as claimed in claim 3 wherein, In the unit startup operation condition, the working process of the primary ejector (11) is as follows: the auxiliary steam expands and accelerates through the nozzle (2-2) and is injected into the mixing chamber (4-4) of the primary ejector (11), forming a low-pressure area, which sucks the feed water from the outlet of the fourth valve group (13) through the suction contraction pipe (3-3) into the mixing chamber (4-4), and the high-temperature steam and the low-temperature water are in the mixing chamber (4-4) for intense direct contact heat exchange and mass exchange, the steam completely condenses into the water, and the heat and the enthalpy of the steam are completely transferred to the water, and the mixed water is slowed down in the diffuser (5-5), the kinetic energy is converted into pressure energy, the pressure is recovered, and the pressure is sufficient to enter the deaerator (1), the pressure and flow of the injected feed water are controlled by adjusting the opening of the electric baffle (1-1) of the primary ejector (11) to meet the pressure and temperature requirements of the feed water delivered to the deaerator (1).

6. The method for feedwater recirculation energy recovery using multiple loops of nuclear power plant employing eductors as claimed in claim 3 wherein, In the unit low load operation condition, the initial state: the electric feed water pump (2) is running, the auxiliary steam is running, the drain pump (6) is stopped, the steam turbine (7) is running, the first valve group (8) and the fourth valve group (13) are put into automatic operation, the second valve group (9), the third valve group (10), the fifth valve group (14), the sixth valve group (15), the seventh valve group (16), the eighth valve group (17) and the ninth valve group (18) are closed; When the unit enters low load operation state, the first valve group (8) automatically adjusts the flow through the steam generator (4) to meet the feed water flow demand under low load operation of the unit, the fourth valve group (13) automatically adjusts the feed water flow into the primary ejector (11), and the electric baffle opening of the primary ejector (11) is adjusted to match the auxiliary steam supply amount so as to meet the feed water pressure and temperature demand delivered to the deaerator (1); When the secondary steam extraction pressure of the steam turbine (7) reaches the demand pressure of the high-pressure heater (3), the seventh valve group (16) is opened, the secondary steam extraction of the steam turbine (7) enters the heat releasing side of the high-pressure heater (3) through the seventh valve group (16) to heat the tube side feed water flowing through the high-pressure heater (3), and the inlet feed water temperature of the steam generator (4) is further increased; the fifth valve group (14) is opened and put into automatic operation, the feed water flow into the secondary ejector (12) is automatically adjusted by the fifth valve group (14), the eighth valve group (17) is opened, and the drain water in the high-pressure heater (3) is delivered to the secondary ejector (12) through the eighth valve group (17), the electric baffle (1-1) opening of the secondary ejector (12) is adjusted to control the pressure and flow of the ejecting feed water, so as to match the drain water flow and pressure demand delivered to the deaerator (1).

7. The method for feedwater recirculation energy recovery using multiple loops of nuclear power plant employing eductors as claimed in claim 3 wherein, Under the high load operation condition of the unit, the initial state is that the electric feed water pump (2) is running, the auxiliary steam is running, the drain water pump (6) is stopped, the steam turbine (7) is running, the first valve group (8), the fourth valve group (13) and the fifth valve group (14) are put into automatic operation, the seventh valve group (16) and the eighth valve group (17) are opened, and the second valve group (9), the third valve group (10), the sixth valve group (15) and the ninth valve group (18) are closed. When the unit enters high load operation state, the first valve group (8) automatically adjusts the flow through the steam generator (4) to meet the feed water flow demand under high load operation of the unit; When the primary steam extraction pressure of the steam turbine (7) reaches the demand pressure of the deaerator (1), the sixth valve group (15) is opened, the primary steam extraction of the steam turbine (7) enters the deaerator (1) through the sixth valve group (15) to meet the feed water pressure and temperature demand of the deaerator (1), the auxiliary steam is stopped, the fourth valve group (13) is interlocked closed, and the primary ejector (11) stops running, and the electric baffle of the primary ejector (11) is closed; The secondary steam extraction of the steam turbine (7) enters the heat releasing side of the high pressure heater (3) through the seventh valve group (16) to heat the feed water flowing through the heat absorbing side of the high pressure heater (3), further increasing the inlet feed water temperature of the steam generator (4), with the increase of the amount of drain in the high pressure heater (3), the feed water flow entering the secondary ejector (12) is automatically adjusted by the fifth valve group (14), the drain pump (6) is started to operate, the ninth valve group (18) is opened, the outlet drain of the drain pump (6) is delivered to the secondary ejector (12) through the ninth valve group (18), the eighth valve group (17) is closed, the pressure and flow of the ejector feed water are controlled by adjusting the opening of the electric baffle (1-1) of the secondary ejector (12) to match the drain flow and pressure demand delivered to the deaerator (1), and the remaining feed water flow is returned to the deaerator (1) through the second valve group (9).

8. The method for feedwater recirculation energy recovery using multiple loops of nuclear power plant employing eductors as claimed in claim 3 wherein, In the case of failure of the primary ejector (11) and normal operation of the secondary ejector (12), the initial state is that the electric feed water pump (2) operates, the auxiliary steam operates, the drain pump (6) operates, the steam turbine (7) operates, the first valve group (8), the second valve group (9), the fourth valve group (13), and the fifth valve group (14) are put into automatic operation, the seventh valve group (16) and the ninth valve group (18) are opened, and the eighth valve group (17), the third valve group (10), and the sixth valve group (15) are closed. When it is monitored that the primary ejector (11) needs to be removed, the fourth valve group (13) is closed, the auxiliary steam is stopped, the primary ejector (11) is removed, the outlet feed water of the electric feed water pump (2) is divided into three paths, of which the first path automatically adjusts the flow through the steam generator (4) through the first valve group (8), the second path automatically adjusts the feed water flow entering the secondary ejector (12) through the fifth valve group (14), and the third path enters the deaerator (1) through the second valve group (9).

9. The method for feedwater recirculation energy recovery using multiple loops of nuclear power plant employing eductors as claimed in claim 3 wherein, In the case of normal operation of the primary ejector (11) and failure of the secondary ejector (12), the initial state is that the electric feed water pump (2) operates, the auxiliary steam operates, the drain pump (6) operates, the steam turbine (7) operates, the first valve group (8), the second valve group (9), the fourth valve group (13), and the fifth valve group (14) are put into automatic operation, the seventh valve group (16) and the ninth valve group (18) are opened, and the eighth valve group (17), the third valve group (10), and the sixth valve group (15) are closed. When it is monitored that the secondary ejector (12) needs to be removed, the third valve group (10) is opened and put into automatic operation, the fifth valve group (14) and the ninth valve group (18) are closed, the secondary ejector (12) is removed, and the outlet drain of the drain pump (6) is automatically adjusted to deliver the drain flow and pressure demand to the deaerator (1) through the third valve group (10).

10. The method for feedwater recirculation energy recovery using multiple loops of nuclear power plant employing eductors as claimed in claim 3 wherein, In the primary ejector (11), the secondary ejector (12) fault condition, the initial state: electric feed water pump (2) operation, auxiliary steam operation, drainage pump (6) operation, steam turbine (7) operation, the first valve group (8), the second valve group (9), the fourth valve group (13), the fifth valve group (14) put into automatic operation, the seventh valve group (16), the ninth valve group (18) open, the eighth valve group (17), the third valve group (10), the sixth valve group (15) close; When monitoring the primary ejector (11), the secondary ejector (12) all occur failure need to cut off, then the fourth valve group (13) is closed, the auxiliary steam is stopped, the primary ejector (11) is out of operation; The fifth valve group (14), the ninth valve group (18) is closed, the secondary ejector (12) is out of operation, the third valve group (10) is opened, the outlet feed water of electric feed water pump (2) is divided into two ways: one way is automatically adjusted through the first valve group (8) to flow through the steam generator (4), the other way is returned to the deaerator (1) through the second valve group (9), the outlet drainage of drainage pump (6) is all delivered to the deaerator (1) through the third valve group (10).

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