A desalted water supply device for a nuclear power plant and a method for controlling operation thereof

Abstract

This invention provides a demineralized water supply device for nuclear power plants and its operation control method, comprising: a water tank; a water pump suction main pipe connected to the water tank; a pump set connected to the outlet of the water pump suction main pipe, including at least two pumps connected in parallel, the pumps being variable frequency pumps; a water pump outlet main pipe connected to the outlet of the pump set; a pressure tank connected to the water pump outlet main pipe; a detection unit including several detectors respectively installed on the water tank, the pump set, and the water pump outlet main pipe; and a control unit connected to the variable frequency pumps and the detection unit. This invention creatively eliminates the essential return pipe in traditional water supply systems, solving the two major problems of energy waste and noise pollution at the source, achieving the goal of energy conservation and environmental protection, and possessing good economic and social benefits. It can be widely applied in nuclear power plants and other related fields.

Description

Technical Field

[0001] This invention belongs to the technical field of nuclear power plant water supply systems, specifically relating to a demineralized water supply device for nuclear power plants and its operation control method. Background Technology

[0002] Currently, the alkaline demineralized water distribution system in nuclear power plants generally employs a method of parallel operation of multiple high-flow-rate pumps with a return pipeline installed on the outlet header. Because the actual water consumption of demineralized water users in nuclear power plants fluctuates greatly, and the pumps cannot efficiently regulate flow, when water consumption falls below the rated flow of a single pump, the excess flow must be returned to the water tank via the return pipeline to protect the pumps. This method results in a large amount of excess flow being returned year-round, causing significant energy waste. Furthermore, excessive return flow can trigger cavitation at the upper flow limit orifice plate of the return pipeline, generating strong noise and polluting the environment.

[0003] Existing technologies mainly address low flow protection by adding a return pipe, but they fail to fundamentally overcome the shortcomings of inflexible adjustment during power frequency operation and the waste and noise caused by return flow. Summary of the Invention

[0004] This invention is made to solve the above-mentioned problems, and its purpose is to provide a demineralized water supply device for nuclear power plants and its operation control method.

[0005] This invention provides a demineralized water supply device for a nuclear power plant, characterized by comprising: a water tank; a water pump suction main pipe connected to the water tank; a pump set connected to the outlet of the water pump suction main pipe, including at least two pumps connected in parallel, the pumps being variable frequency pumps; a water pump outlet main pipe connected to the outlet of the pump set; a pressure water tank connected to the water pump outlet main pipe; a detection unit including several detectors respectively installed on the water tank, the pump set, and the water pump outlet main pipe; and a control unit connected to the variable frequency pumps and the detection unit.

[0006] In one embodiment of the present invention, the pump set includes at least one high-flow-rate variable frequency pump and at least one low-flow-rate variable frequency pump, wherein the rated flow rate of the low-flow-rate variable frequency pump is less than the rated flow rate of the high-flow-rate variable frequency pump.

[0007] In one embodiment of the present invention, the rated flow rate of the small flow variable frequency pump is 15 to 45% of the rated flow rate of the large flow variable frequency pump.

[0008] In one embodiment of the present invention, the inlet end of the variable frequency pump is provided with a water pump inlet isolation valve, and the outlet end of the variable frequency pump is provided with a water pump outlet check valve and a water pump outlet isolation valve in sequence. The pressure tank is connected to the water pump outlet main pipe through the pressure tank isolation valve, and a drain valve is provided at the lowest point of the pipeline between the pressure tank isolation valve and the pressure tank.

[0009] In one embodiment of the present invention, the detector includes: a water pump outlet main pipe pressure switch, disposed on the water pump outlet main pipe; a water pump outlet main pipe flow meter, disposed on the water pump outlet main pipe; a water pump outlet main pipe pressure transmitter, disposed on the water pump outlet main pipe; a water tank level transmitter, disposed on the water tank; and a pipeline remote pressure transmitter, connected to the remote end of the water pump outlet main pipe.

[0010] In one embodiment of the present invention, the control unit includes a microcomputer and a frequency converter connected to each other. The microcomputer is connected to the water pump outlet main pipe pressure switch, the water tank level transmitter, the pipeline remote pressure transmitter, the water pump outlet main pipe flow meter, and the water pump outlet main pipe pressure transmitter, respectively, for receiving detection information. The frequency converter is connected to the frequency converter pump and is used to control the frequency converter pump based on the detection information.

[0011] The present invention also provides an operation control method for a demineralized water supply device in a nuclear power plant, characterized by: real-time detection of flow and pressure signals of the pump outlet header via a flow meter and a pressure transmitter, and transmission to a control unit; the control unit determining the load status of the demineralized water supply device based on the flow and pressure signals; and, based on the load status, adjusting the speed and operation of the variable frequency pump via a frequency converter, wherein the variable frequency pump includes a high-flow variable frequency pump and a low-flow variable frequency pump.

[0012] In one embodiment of the present invention, the control unit adjusts the speed and operation of the variable frequency pump through the frequency converter, including the following steps: preset a flow threshold; when the flow signal is lower than the flow threshold, start the small flow variable frequency pump; when the flow signal is higher than the flow threshold, start the large flow variable frequency pump to operate in conjunction with the small flow variable frequency pump; when the flow signal continues to rise, gradually increase the number of large flow variable frequency pumps in operation.

[0013] In one embodiment of the present invention, the control unit adjusts the speed and operation of the variable frequency pump through the frequency converter, including the following steps: the control unit receives the remote pressure signal from the remote pressure detection unit of the pipeline network, and corrects and adjusts the speed of the variable frequency pump according to the remote pressure signal.

[0014] In one embodiment of the present invention, the control unit adjusts the speed and operation of the variable frequency pump through the frequency converter, including the following steps: the control unit receives the liquid level signal from the water tank level transmitter and the overpressure protection signal from the pressure switch of the water pump outlet main pipe, presets the liquid level threshold and the pressure threshold, and when the liquid level signal is lower than the liquid level threshold or the overpressure protection signal exceeds the pressure threshold, the control unit issues an alarm or shutdown command.

[0015] The role and effect of invention According to the demineralized water supply device and its operation control method for nuclear power plants involved in this invention, the invention systematically integrates large-flow and small-flow variable frequency pumps, stabilizes the pressure through a pressure tank, and controls the system through a detection unit and a control unit. This invention creatively eliminates the essential return pipe in traditional water supply systems, solving the two major problems of energy waste and noise pollution at the source, achieving the goal of energy conservation and environmental protection, and has good economic and social benefits. It can be widely applied in nuclear power plants and other related fields. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the demineralized water supply device for a nuclear power plant in an embodiment of the present invention.

[0018] Figure 2 This is a flowchart illustrating the operation control method of a demineralized water supply device in a nuclear power plant, as described in an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of the demineralized water supply system in a nuclear power plant in the prior art.

[0020] Explanation of reference numerals in the attached figures: 100-Demineralized water supply device for nuclear power plant; 101-Water tank; 102-Water tank level transmitter; 103-Water pump suction main pipe; 104-Water pump inlet isolation valve; 105-Pump set; 106-High flow variable frequency pump; 107-Small flow variable frequency pump; 108-Water pump outlet check valve; 109-Water pump outlet isolation valve; 110-Water pump outlet main pipe; 111-Pressure tank isolation valve; 112-Pressure tank; 113-Drain valve; 114-Water pump outlet main pipe flow meter; 115-Water pump outlet main pipe pressure transmitter; 116-Water pump outlet main pipe pressure switch; 117-Pipeline remote pressure transmitter; 118-Control unit; 200-Existing water supply device; 201-High flow industrial frequency pump; 202-Return pipeline. Detailed Implementation

[0021] The technical solutions disclosed in this invention will be described in detail below with reference to specific embodiments.

[0022] 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.

[0023] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0024] In this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used only for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0025] To make the technical means, creative features, objectives and effects of this invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the demineralized water supply device for nuclear power plants and its operation control method.

[0026] The demineralized water supply device and its operation control method for nuclear power plants provided by this invention can be widely applied to various industrial and civil water supply systems with stringent requirements for water supply reliability, energy efficiency, and environmental protection. It is particularly suitable for alkaline demineralized water distribution systems in the nuclear island, conventional island, and supporting facilities of nuclear power plants, as well as other industrial circulating water systems and municipal water supply systems that require continuous operation and experience significant fluctuations in water consumption. Specifically, the application scenarios of the demineralized water supply device 100 for nuclear power plants include, but are not limited to, the new design of the conventional island demineralized water distribution system (SER) or the energy-saving and noise-reduction retrofit of existing systems. For example, in the application of the conventional island demineralized water distribution system, it can be used to provide continuous, stable, and high-quality demineralized water to important nuclear island equipment such as steam generators, main pumps, and pressurizers, as well as conventional island equipment such as steam turbines and condensers, and users in various plant buildings of the nuclear power plant's supporting facilities.

[0027] like Figure 1As shown, the demineralized water supply device 100 for a nuclear power plant of the present invention includes a water tank 101, a water pump suction main pipe 103, a pump set 105, a water pump outlet main pipe 110, a pressurized water tank 112, a detection unit, and a control unit 118. The detection unit includes several detectors, respectively installed on the water tank 101, the pump set 105, and the water pump outlet main pipe 110, for real-time monitoring of the operating status of the demineralized water supply device 100 of the nuclear power plant and obtaining detection signals. Specifically, the detection unit may include one or more of the following instruments: a water pump outlet main pipe flow meter 114, a water pump outlet main pipe pressure transmitter 115, a water pump outlet main pipe pressure switch 116, a water tank level transmitter 102, and a pipeline remote pressure transmitter 117. The detection unit transmits the detection signals to the input terminal of the control unit 118, and the output terminal of the control unit 118 is connected to the pump set 105 via a cable and control signal to achieve precise control of the water pump.

[0028] like Figure 1 As shown, water tank 101 is used to receive and store demineralized water, serving as an upstream container for pump set 105 to provide the working medium for the demineralized water supply unit 100 of the entire nuclear power plant. A water tank level transmitter 102 is installed on water tank 101 for real-time monitoring of the water level within water tank 101. Pump suction main pipe 103 is connected to the outlet of water tank 101, and its function is to collect the demineralized water flowing out of water tank 101 and distribute water to pump set 105, which consists of multiple pumps connected in parallel. Pump suction main pipe 103 is connected to pump set 105 through multiple parallel branches. Specifically, pump set 105 includes at least two pumps connected in parallel through parallel branches, and each pump is a variable frequency pump. In each parallel branch, a water pump inlet isolation valve 104 and a variable frequency pump are sequentially installed. The outlet end of the variable frequency pump is sequentially connected to a water pump outlet check valve 108 and a water pump outlet isolation valve 109. These parallel branches are then connected to the water pump outlet header 110. The water pump outlet check valve 108 prevents backflow of the medium, protecting the water pump. The water pump inlet isolation valve 104 and the water pump outlet isolation valve 109 are used for isolation during maintenance of the corresponding water pump.

[0029] In one preferred embodiment, to more accurately adapt to the drastic fluctuations in demineralized water usage at nuclear power plants, pump unit 105 may include at least one high-flow-rate variable frequency pump 106 and at least one low-flow-rate variable frequency pump 107. The rated flow rate of the low-flow-rate variable frequency pump 107 is less than that of the high-flow-rate variable frequency pump 106. This invention does not limit the specific rated flow rates of the high-flow-rate variable frequency pump 106 and the low-flow-rate variable frequency pump 107. Preferably, the rated flow rate of the low-flow-rate variable frequency pump 107 can be 15% to 45% of the rated flow rate of the high-flow-rate variable frequency pump 106. This combination of rated flow rates allows only the low-flow-rate variable frequency pump 107 to operate during periods of low water usage, ensuring it operates in its high-efficiency zone and avoiding energy waste. During periods of peak water usage, the high-flow-rate variable frequency pump 106 and the low-flow-rate variable frequency pump 107 can be activated in tandem, or even multiple high-flow-rate variable frequency pumps 106 can be activated to meet peak flow demands. In one specific embodiment of the present invention, the pump set 105 includes three high-flow variable frequency pumps 106 and one low-flow variable frequency pump 107. The three high-flow variable frequency pumps 106 are configured as two in use and one as a backup to ensure the redundancy and reliability of the demineralized water supply device 100 of the nuclear power plant.

[0030] This invention does not limit the specific number or function of the variable frequency pumps. There can be one or more variable frequency pumps, and their functions can be the same or different, specifically designed to achieve the water supply device's adjustment function. The variable frequency speed control technology of the water pump utilizes the principle of changing the motor's input current frequency to change the motor's speed, thereby changing the pump's performance parameters. When the speed n changes, the pump's flow rate Q, head H, and shaft power N change with the speed according to the following formulas: Equation (1) In equation (1), n ​​represents the rotational speed, the subscript 0 indicates the power frequency parameter, Q represents the flow rate, H represents the head, and N represents the shaft power. Equation (1) shows that when the rotational speed n decreases, the decrease in flow rate Q is proportional to the decrease in rotational speed, the decrease in head H is proportional to the square of the decrease in rotational speed, and the decrease in shaft power N is proportional to the cube of the decrease in rotational speed. Therefore, it can be concluded that using frequency conversion to reduce the rotational speed can decrease the pump's flow rate, but the pump's head will also decrease. Simultaneously, the required shaft power of the pump is also greatly reduced. Thus, the frequency conversion pump of this invention adjusts the motor speed by changing the power supply frequency, thereby changing the flow rate and head of the frequency conversion pump, achieving energy-saving regulation.

[0031] The water pump outlet header 110 is connected to the outlet of the pump set 105. Its function is to collect the demineralized water output by the pump set 105 and transport it to downstream demineralized water users. A water pump outlet header flow meter 114, a water pump outlet header pressure transmitter 115, and a water pump outlet header pressure switch 116 are sequentially installed on the water pump outlet header 110. The water pump outlet header flow meter 114 is installed on the water pump outlet header 110 to detect the total water flow rate of downstream users. The water pump outlet header pressure transmitter 115 is installed on the water pump outlet header 110 to detect the pressure of the water pump outlet header 110. The water pump outlet header pressure switch 116 is installed on the water pump outlet header 110 to provide an overpressure protection signal when the pressure of the water pump outlet header 110 exceeds a set value.

[0032] like Figure 1 As shown, the water pump outlet header 110 is also connected to the pressure tank 112 via a pressure tank isolation valve 111. A drain valve 113 is installed at the lowest point of the pipe between the pressure tank isolation valve 111 and the pressure tank 112. The pressure tank 112 is connected to the water pump outlet header 110. The pressure tank 112 is pre-filled with gas, utilizing the compressibility of the gas to store and release energy, thereby providing a constant pressure water supply function, compensating for instantaneous pressure fluctuations caused by the pump unit 105 during variable frequency speed regulation, and ensuring stable water supply pressure. This invention does not impose specific limitations on the specific model or size of the pressure tank 112; it is determined based on the actual operating parameters of the demineralized water supply device 100 in the nuclear power plant. The pressure tank 112 can adopt different forms such as diaphragm type, bladder type, or air-water contact type, as long as it can achieve pressure stabilization and compensation functions. In one implementation, the regulating water volume of the pressure tank 112 should not be less than the water supply of the maximum working pump under the device head and operating at power frequency for 90 seconds, to ensure that it can effectively absorb pressure shocks. The pressure tank 112 is connected to the water pump outlet header 110 through the pressure tank isolation valve 111 for easy maintenance and isolation. At the lowest point of the pipeline between the pressure tank isolation valve 111 and the pressure tank 112, a drain valve 113 is installed to drain the water stored in the pressure tank 112 and the connecting pipeline during maintenance or shutdown.

[0033] like Figure 1As shown, a network remote pressure transmitter 117 is installed at the far end of the water pump outlet header 110. Typically, the far end of the water pump outlet header 110 is located near important users or the end of the network, enabling the network remote pressure transmitter 117 to detect the pressure at the far end of the network and achieve precise control of the remote pressure. The aforementioned detector transmits the real-time acquired analog or digital signals to the control unit 118. It is worth noting that the demineralized water supply device 100 for nuclear power plants of this invention eliminates the return pipe 202 installed on the water pump outlet header 110 for returning excess flow to the water tank 101. This structural change physically eliminates energy waste and noise pollution caused by return flow.

[0034] like Figure 1 As shown, the control unit 118 is connected to the high-flow variable frequency pump 106, the low-flow variable frequency pump 107, and the detection unit. Specifically, the control unit 118 includes a microcomputer and a frequency converter connected to each other. The microcomputer, as an input terminal, is connected to the pressure switch 116 at the pump outlet header, the water tank level transmitter 102, the remote pressure transmitter 117 of the pipeline network, the flow meter 114 at the pump outlet header, and the pressure transmitter 115 at the pump outlet header, thereby receiving and processing various detection signals. The frequency converter is connected to the motor of each variable frequency pump and is used to precisely control the speed and start / stop of the variable frequency pump based on the instructions issued by the microcomputer.

[0035] It is worth noting that this application does not limit the type of microcomputer, but specifically refers to the microcomputer capable of realizing automatic control, data processing, and logical operation functions of the water supply device. As one implementation, the microcomputer may be, for example, but not limited to, a programmable logic controller (PLC). Examples also include industrial control computers, embedded microprocessors, digital signal processors (DSPs), microcontrollers (MCUs), or field-programmable gate arrays (FPGAs)—electronic devices with computing and control capabilities. The microcomputer employs any form of computing device capable of receiving multiple detection signals, executing preset constant-voltage frequency conversion control strategies, and outputting real-time speed adjustment commands and start / stop commands. In practical applications, depending on the complexity, a single-core or multi-core processor can be selected, and redundant configurations can be used to improve reliability.

[0036] like Figure 2 As shown, the present invention also discloses an operation control method for a demineralized water supply device 100 in a nuclear power plant, comprising the following steps: S1, the control unit 118 receives flow and pressure signals from the pump outlet header 110, which are collected in real time by the pump outlet header flow meter 114 and the pump outlet header pressure transmitter 115, via its built-in microcomputer. Simultaneously, the control unit 118 may also receive remote pressure signals from the remote pressure transmitter 117 in the pipeline network, level signals from the water tank level transmitter 102, and overpressure protection signals from the pump outlet header pressure switch 116.

[0037] S2, the microcomputer built into the control unit 118 comprehensively judges the current load status of downstream users based on the received flow signal, pressure signal and other multi-dimensional information. For example, a first flow threshold and a second flow threshold are preset as the basis for judging the load status of the demineralized water supply device 100 of the nuclear power plant. When the detected flow signal is lower than the preset first flow threshold, it is judged that the demineralized water supply device 100 of the nuclear power plant is in a low load state; when the flow signal is higher than the first flow threshold but lower than the second flow threshold, it is judged that the demineralized water supply device 100 of the nuclear power plant is in a medium load state; when the flow signal continues to rise and exceeds the second flow threshold, it is judged that the demineralized water supply device 100 of the nuclear power plant is in a high load state.

[0038] S3, based on the determined load state, the control unit 118 executes the corresponding control strategy, precisely adjusting the speed and operating combination of the variable frequency pumps through the frequency converter. It is worth noting that the core control logic of this invention lies in flexibly adjusting the number and speed of the large-flow variable frequency pump 106 and the small-flow variable frequency pump 107 to achieve on-demand water supply.

[0039] In one implementation, when the demineralized water supply unit 100 of the nuclear power plant is under low load, i.e., the flow signal is lower than a preset first flow threshold, the control unit 118 prioritizes and independently starts and operates the small-flow variable frequency pump 107. Since the rated flow of the small-flow variable frequency pump 107 is relatively small, it can operate in the high-efficiency range under low load conditions. By adjusting its speed via a frequency converter, it can accurately match the downstream's small flow demand, eliminating the need to start the large-flow variable frequency pump 106. When the load increases and the flow signal exceeds the preset first flow threshold, the control unit 118 starts the large-flow variable frequency pump 106, which operates in conjunction with the small-flow variable frequency pump 107. At this time, the large-flow variable frequency pump 106 provides the basic flow, while the small-flow variable frequency pump 107 is finely adjusted through variable frequency speed control to jointly meet the load demand. When the load continues to rise and the flow signal exceeds a higher second flow threshold, the control unit 118 will gradually increase the number of large-flow variable frequency pumps 106 as needed. For example, the number of large-flow variable frequency pumps 106 may be increased from one to two to meet peak flow demand. Throughout the adjustment process, the pressure tank 112 is always connected to the pump set 105. Therefore, when the speed of the pump set 105 changes or the user's water consumption changes suddenly, causing pressure fluctuations in the water pump outlet header 110, the pressure tank 112 can quickly absorb or release water through the compression and expansion of its air bladder, thereby effectively buffering the pressure shock and ensuring the stability of the water supply pressure, thus compensating for the pressure fluctuations caused by speed adjustment.

[0040] As one implementation method, the control unit 118 also utilizes other detection signals for correction and protection. For example, the control unit 118 receives a remote pressure signal from the remote pressure transmitter 117 of the pipeline network. If the remote pressure is lower than a set value, it indicates insufficient pressure at the end of the pipeline network. The control unit 118 will then appropriately increase the speed of the variable frequency pump to perform pressure compensation correction. The control unit 118 also presets liquid level and pressure thresholds. When the liquid level signal from the water tank level transmitter 102 is lower than the low liquid level threshold, the control unit 118 will issue an alarm to prevent the water pump from running dry. When the water pump outlet main pipe pressure switch 116 experiences overpressure, or the pressure transmitter signal exceeds the high pressure threshold, the control unit 118 can also issue an alarm or shutdown command to protect the safety of the nuclear power plant's demineralized water supply system 100 and pipelines. Throughout the entire operation, thanks to the cooperation of the control unit 118 and the detection unit, precise frequency conversion regulation and the combination of large and small pump groups 105 are adopted, the water supply flow rate always matches the user's needs, and there is no excess flow. Therefore, the demineralized water supply device 100 for nuclear power plants of the present invention can achieve flow regulation without any return pipe 202.

[0041] like Figure 3The diagram shows a water supply device for a pre-existing alkaline demineralized water distribution system in a nuclear power plant. The existing water supply device 200 primarily utilizes three high-flow-rate industrial frequency pumps 201, and a return pipe 202 connected to the water tank 101 via the pump outlet header 110. The three high-flow-rate industrial frequency pumps 201 operate in parallel, with two in use and one on standby. The operation control method mainly involves: using three identical high-flow-rate industrial frequency pumps 201 as the water supply unit to provide the required demineralized water to downstream users; adjusting the number of operating pumps based on changes in downstream water consumption using a single flow control method via the pump outlet header 110; and using the return pipe 202 to return excess flow from the high-flow-rate industrial frequency pumps 201 to the water tank 101 when the downstream water consumption does not match the total flow rate of the operating pumps, or when the downstream water consumption is less than the flow rate of a single pump. However, this method cannot efficiently and economically regulate the flow rate, and there is always a large amount of excess flow returning to the water tank 101 through the return pipe 202. Such uneconomical operation over the years results in a large amount of energy waste. Furthermore, due to the excessive return flow, the flow limiting orifice plate on the return pipe 202 causes cavitation due to excessive flow restriction, generating a huge noise and causing serious noise pollution to the surrounding environment.

[0042] The demineralized water supply device 100 for nuclear power plants of the present invention combines variable frequency speed regulation technology, constant pressure water supply technology, microcomputer control technology and new operation control methods, which can flexibly, efficiently and economically adjust the flow rate, while eliminating the return pipe 202 that wastes a lot of energy. Under the premise of meeting the needs of users of alkaline demineralized water in nuclear power plants, the energy consumption of the demineralized water supply device 100 for nuclear power plants is greatly reduced, and a large amount of energy can be saved compared with the existing technical solutions.

[0043] In addition, the present invention combines microcomputer-controlled variable frequency speed regulation constant pressure water supply technology with a new operation control method, eliminating the return pipe 202, thus fundamentally eliminating the noise pollution of the return pipe 202.

[0044] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0045] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A demineralized water supply device for a nuclear power plant, characterized in that, include: Water tank; The water pump's main suction pipe is connected to the water tank. A pump set, connected to the outlet of the water pump suction main pipe, includes at least two water pumps connected in parallel, and the water pumps are variable frequency pumps; The water pump outlet header is connected to the outlet of the pump unit; A pressure water tank is connected to the outlet header of the water pump; The detection unit includes several detectors, which are respectively installed on the water tank, the pump set and the water pump outlet header; The control unit is connected to the variable frequency pump and the detection unit.

2. The demineralized water supply device for a nuclear power plant according to claim 1, characterized in that: The pump set includes at least one high-flow variable frequency pump and at least one low-flow variable frequency pump, wherein the rated flow rate of the low-flow variable frequency pump is less than the rated flow rate of the high-flow variable frequency pump.

3. The demineralized water supply device for a nuclear power plant according to claim 2, characterized in that: The rated flow rate of the small-flow variable frequency pump is 15-45% of the rated flow rate of the large-flow variable frequency pump.

4. The demineralized water supply device for a nuclear power plant according to claim 1, characterized in that: The variable frequency pump is equipped with a pump inlet isolation valve at its inlet end, and a pump outlet check valve and a pump outlet isolation valve are sequentially installed at its outlet end. The pressure water tank is connected to the outlet main pipe of the water pump through the pressure water tank isolation valve, and a drain valve is installed at the lowest point of the pipeline between the pressure water tank isolation valve and the pressure water tank.

5. The demineralized water supply device for a nuclear power plant according to claim 1, characterized in that, The detector includes: A pressure switch for the water pump outlet header is installed on the water pump outlet header. A flow meter for the water pump outlet header is installed on the water pump outlet header. A pressure transmitter for the water pump outlet header is installed on the water pump outlet header. A water tank level transmitter is installed on the water tank; The pipeline remote pressure transmitter is connected to the far end of the outlet header of the water pump.

6. The demineralized water supply device for a nuclear power plant according to claim 5, characterized in that: The control unit includes a microcomputer and a frequency converter that are interconnected. The microcomputer is connected to the pressure switch on the water pump outlet main pipe, the water tank level transmitter, the remote pressure transmitter in the pipeline network, the flow meter on the water pump outlet main pipe, and the pressure transmitter on the water pump outlet main pipe, respectively, for receiving detection information. The frequency converter is connected to the frequency converter pump and is used to control the frequency converter pump based on the detection information.

7. A method for operating and controlling a demineralized water supply device for a nuclear power plant according to any one of claims 1 to 6, characterized in that, Includes the following steps: The flow and pressure signals of the water pump outlet header are detected in real time by the water pump outlet header flow meter and the water pump outlet header pressure transmitter, and then transmitted to the control unit. The control unit determines the load status of the demineralized water supply system of the nuclear power plant based on the flow signal and the pressure signal. Based on the load condition, the control unit adjusts the speed and operation of the variable frequency pump via the frequency converter. The variable frequency pumps include high-flow variable frequency pumps and low-flow variable frequency pumps.

8. The operation control method according to claim 7, characterized in that, The control unit regulates the speed and operation of the variable frequency pump via the frequency converter, including the following steps: A preset flow rate threshold is set, and when the flow rate signal is lower than the flow rate threshold, the low-flow variable frequency pump is activated. When the flow rate signal is higher than the flow rate threshold, the high-flow-rate variable frequency pump and the low-flow-rate variable frequency pump are started to operate in coordination. As the flow rate signal continues to rise, the number of high-flow-rate variable frequency pumps in operation is gradually increased.

9. The operation control method according to claim 7, characterized in that, The control unit regulates the speed and operation of the variable frequency pump via the frequency converter, including the following steps: The control unit receives the remote pressure signal from the pipeline remote pressure detection unit and adjusts the speed of the variable frequency pump according to the remote pressure signal.

10. The operation control method according to claim 7, characterized in that, The control unit regulates the speed and operation of the variable frequency pump via the frequency converter, including the following steps: The control unit receives a level signal from the water tank level transmitter and an overpressure protection signal from the water pump outlet main pipe pressure switch. It presets a level threshold and a pressure threshold. When the level signal is lower than the level threshold or the overpressure protection signal exceeds the pressure threshold, the control unit issues an alarm or shutdown command.

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