A seawater desalination system and method based on high temperature seawater in nuclear power plants

Abstract

The present invention discloses a seawater desalination system and method based on the high temperature of nuclear power plant seawater. The system comprises a nuclear power plant cold water component, a heat pump unit and a seawater desalination component. The nuclear power plant cold water component is coupled to the evaporation end of the heat pump unit, and the seawater desalination component is coupled to the condensation end of the heat pump unit. After the seawater passes through the evaporation end of the heat pump unit and is cooled, it provides cooling capacity for the nuclear power plant cold water. After the circulating water passes through the condenser of the heat pump unit and is heated, it enters a flash tank. Part of it is vaporized into steam and enters a low-temperature multi-effect distillation component to provide steam for the low-temperature multi-effect distillation component, and part of it is condensed into liquid water. The present invention couples the heat pump technology, the flash evaporation technology and the low-temperature multi-effect distillation technology. While the heat pump cools the plant water system of the nuclear power unit, it can produce high-temperature water. After the high-temperature water passes through the flash evaporation, it forms low-temperature steam of about 70°C. Coupled with the low-temperature multi-effect distillation seawater desalination technology, seawater desalination can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of water use and seawater desalination in nuclear power plants, and in particular relates to a seawater desalination system and method based on high-temperature seawater in nuclear power plants. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Seawater is the ultimate heat sink for coastal nuclear power plants. As the global climate warms, the seawater temperature is also rising year by year. In addition, the discharge of warm wastewater from nuclear power plants directly affects the seawater temperature at the water intake of nuclear power plants.

[0004] The rise in seawater temperature has the following two main impacts on nuclear power plants:

[0005] (1) For in-service units, when seawater temperature exceeds the original design benchmark, the operation of the plant water system, the cooling water system, and downstream user equipment will be affected. Under extreme operating conditions, the nuclear power unit needs to reduce power operation or even trigger a shutdown.

[0006] (2) For newly built units, rising seawater temperatures directly impact system design, especially for upstream and downstream users of the cold chain system. Excessively high seawater temperatures increase the difficulty of cold chain equipment design and affect the economic viability of the power plant.

[0007] In addition, the inventors found that the evaporation technologies currently used for seawater desalination mainly include multi-effect evaporation (MED), multi-stage flash evaporation (MSF), mechanical vapor compression evaporation (MVC) and mechanical vapor recompression (MVR). However, multi-effect evaporation and multi-stage flash evaporation require a large amount of raw steam as a heat source, which is generally used for cogeneration of water and power in thermal power plants. They are not very applicable to areas with scarce steam resources; mechanical vapor compression evaporation also requires continuous introduction of steam as a heat source, but the compressor can be used to increase the energy head of the steam, thereby reducing the use of steam resources with the consumption of electricity; the mechanical vapor recompression system only needs to input raw steam into the system for heating when it is turned on, and then the steam generated by the system is recycled as a heat source through the steam compressor to increase the energy head. Electric energy is the main energy provided to the system by the outside world. The above-mentioned evaporation systems all need to be connected to a steam generator as an external energy source, which has a certain system complexity and operation difficulty. Summary of the Invention

[0008] The purpose of the present invention is to provide a seawater desalination system and method based on the high temperature of nuclear power plant seawater, which can reduce the water supply temperature of the plant water system under high temperature weather in summer and realize seawater desalination at the same time.

[0009] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0010] In the first aspect, an embodiment of the present invention provides a seawater desalination system based on the high temperature of nuclear power plant seawater, including a nuclear power plant cold water component, a heat pump unit and a seawater desalination component. The nuclear power plant cold water component is coupled with the evaporation end of the heat pump unit, and the seawater desalination component is coupled with the condensation end of the heat pump unit. After the seawater is cooled by the evaporation end of the heat pump unit, it provides cooling capacity for the nuclear power plant cold water; after the circulating water is heated by the condenser of the heat pump unit, it enters the flash tank, part of which is vaporized into steam and enters the low-temperature multi-effect distillation component to provide steam for the low-temperature multi-effect distillation component, and part of it is condensed into liquid water.

[0011] As a further technical solution, the heat pump unit includes a compressor, a condenser, a throttle valve and an evaporator which are sequentially connected through pipelines. The evaporator is also connected to the compressor to form a refrigerant circulation loop.

[0012] As a further technical solution, the nuclear power plant cold water assembly includes a cold water heat exchanger, the seawater intake is connected to the evaporator through a pipeline, and the seawater outlet of the evaporator is connected to the cold water heat exchanger through a pipeline.

[0013] As a further technical solution, the cold water heat exchanger adopts a plate-type heat tube heat exchanger, a shell-and-tube heat exchanger or a sleeve-and-tube heat exchanger.

[0014] As a further technical solution, the seawater desalination assembly includes a flash tank and a low-temperature multi-effect distillation seawater desalination device.

[0015] As a further technical solution, a circulating water inlet, a condensed water outlet and a steam outlet are provided on the flash tank, wherein the circulating water inlet and the condensed water outlet are connected to the condenser through pipelines, and the steam outlet is connected to the low-temperature multi-effect distillation seawater desalination device.

[0016] As a further technical solution, the condensate outlet of the low-temperature multi-effect distillation seawater desalination device is connected to a condenser.

[0017] As a further technical solution, the evaporator and condenser adopt shell and tube heat exchangers.

[0018] In a second aspect, an embodiment of the present invention provides a method for desalination of seawater based on high temperature of seawater in a nuclear power plant, comprising:

[0019] After the seawater is cooled by the evaporator of the heat pump unit, it enters the cold water heat exchanger to provide a cold source for the cold water of the nuclear power plant; after the circulating water is heated by the condenser of the heat pump unit, it enters the flash tank. Under the action of the flash tank, part of the heated circulating water is vaporized into steam and enters the low-temperature multi-effect distillation component to provide steam for the seawater desalination process, and part of it is condensed into liquid water.

[0020] As a further technical solution, the liquid water produced by the flash tank and the condensed water produced by the low-temperature multi-effect distillation component are used as circulating water.

[0021] The beneficial effects of the above embodiments of the present invention are as follows:

[0022] The desalination system, designed for high-temperature nuclear power plant seawater, incorporates a heat pump unit. This system utilizes heat pump technology to pump heat from a low-temperature heat source to a high-temperature heat source at the expense of a small amount of high-grade energy. Considering the high temperatures of seawater in nuclear power plants, heat pump technology can be used to cool summer seawater, ensuring the proper operation of the plant's cold chain system.

[0023] The seawater desalination system based on the high temperature of nuclear power plant seawater provided by the present invention couples heat pump technology, flash evaporation technology and low-temperature multi-effect distillation technology. While the heat pump cools the plant water system of the nuclear power unit, it can produce high-temperature water. After flash evaporation, the high-temperature water forms low-temperature steam of about 70°C. Coupled with the low-temperature multi-effect distillation seawater desalination technology, seawater desalination can be achieved.

[0024] The present invention provides a seawater desalination system based on the high temperature of nuclear power plant seawater. In extremely hot weather, this system uses heat pump technology to reduce the water supply temperature of the nuclear power plant's water system, preventing the nuclear power unit from operating at reduced power or even shutting down due to the high temperature of the seawater, thereby ensuring the normal operation of the nuclear power unit's cold chain system. At the same time, the low-grade heat extracted by the heat pump is coupled with flash evaporation technology to generate low-temperature steam, which drives the operation of the low-temperature multi-effect distillation desalination device and realizes seawater desalination production. Under the action of this system, the seawater temperature in extremely hot weather is reduced, and seawater desalination production is realized, ensuring the normal operation of the nuclear power unit and improving the economy and safety of the nuclear power unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 It is a schematic diagram of the seawater desalination system based on the high temperature of nuclear power plant seawater of the present invention.

[0027] The diagram is for illustrative purposes only;

[0028] Among them, 1. Evaporator; 2. Compressor; 3. Condenser; 4. Throttle valve; 5. Cold water heat exchanger; 6. Flash tank; 7. Low-temperature multi-effect distillation seawater desalination device. DETAILED DESCRIPTION

[0029] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0030] Example 1

[0031] In a typical embodiment of the present invention, Figure 1 As shown, a seawater desalination system based on the high temperature of nuclear power plant seawater is provided, including a nuclear power plant cold water component, a heat pump unit and a seawater desalination component. The nuclear power plant cold water component is coupled with the evaporation end of the heat pump unit to cool the seawater used by the nuclear power plant. The seawater desalination component is coupled with the condensation end of the heat pump unit to provide steam for the seawater desalination component to achieve seawater desalination.

[0032] Specifically, the heat pump unit includes a compressor 2, a condenser 3, a throttle valve 4, and an evaporator 1, which are sequentially connected via pipelines. The evaporator 1 is also connected to the compressor, forming a refrigerant circulation loop. The heat pump unit operates as follows: the working fluid inside the evaporator 1 absorbs heat and vaporizes, which is then drawn into the compressor 2. The compressor 2 compresses this low-pressure working fluid gas into a high-temperature, high-pressure gas, which is then fed into the condenser 3. Inside the condenser 3, the working fluid is cooled into a liquid. This liquid is then throttled and cooled by the throttle valve 4 before flowing back into the evaporator 1 for evaporation. Therefore, the evaporator acts as the evaporation end of the heat pump unit, releasing cooling energy, while the condenser acts as the condensation end of the heat pump unit, releasing heat energy.

[0033] In this embodiment, the nuclear power plant's chiller assembly includes a chiller heat exchanger 5. The seawater intake is connected to the evaporator 1 via a pipeline, and the seawater outlet of the evaporator 1 is also connected to the chiller heat exchanger 5 via a pipeline. Specifically, the evaporator 1 can be a shell-and-tube heat exchanger, with the refrigerant flowing through the tubes and the seawater flowing through the shell. In the evaporator 1, the refrigerant and seawater exchange heat, lowering the seawater temperature. The cooled seawater then enters the chiller heat exchanger 5, where it exchanges heat with the cold water required by the nuclear power plant's chiller system, removing heat from the cold water.

[0034] In this embodiment, the cold water heat exchanger may be a plate-type heat exchanger, a shell-and-tube heat exchanger, or a double-tube heat exchanger.

[0035] In this embodiment, the seawater desalination assembly includes a flash tank 6 and a low-temperature multi-effect distillation seawater desalination device 7. The flash tank 6 is provided with a circulating water inlet, a condensed water outlet, and a steam outlet. The circulating water inlet and the condensed water outlet are connected to the condenser via pipelines. Specifically, the condenser 3 can be a shell-and-tube heat exchanger, with the refrigerant flowing through the tube side and the circulating water flowing through the shell side. In the condenser, the refrigerant and the circulating water exchange heat, the circulating water temperature increases, and the heated circulating water enters the flash tank 6. In the flash tank, part of the circulating water vaporizes into steam and enters the low-temperature multi-effect distillation seawater desalination device, while part condenses into liquid water. The working principle is: after high-pressure saturated water enters a relatively low-pressure container, the sudden drop in pressure causes this saturated water to become saturated water vapor and saturated water at a portion of the container pressure. The steam outlet of the flash tank is connected to the low-temperature multi-effect distillation seawater desalination device to provide steam for the seawater desalination process.

[0036] Since the condenser of the heat pump unit cannot directly heat the circulating water into steam, this embodiment uses a flash tank to flash the heated circulating water into steam that can be directly used, so that the low-temperature multi-effect distillation seawater desalination device does not require additional steam equipment, thereby improving the economy of the system.

[0037] In this embodiment, the condensed water outlet of the low-temperature multi-effect distillation seawater desalination device is connected to the condenser, and the condensed water outlet of the flash tank is also connected to the condenser. Therefore, the condensed water after the steam condensation in the low-temperature multi-effect distillation seawater desalination device and the condensed water generated by the flash tank are merged and enter the condenser to be circulated and used as circulating water.

[0038] In this embodiment, a low-temperature multi-effect distillation seawater desalination device is provided with a multi-effect evaporator. The evaporator adopts a horizontal tube spray falling film evaporator. A certain amount of steam is input into the first effect. The evaporation temperature of the subsequent effect is lower than that of the previous effect. Then, through multiple evaporation and condensation, a desalination process of distilled water with a volume multiple times the steam volume is obtained. The low-temperature multi-effect distillation seawater desalination device used in this embodiment includes a steam supply system, a water distribution system, an evaporator, a fresh water tank and a concentrated water tank. The raw steam inlet of the steam supply system is placed on the middle effect evaporator. The working method is as follows: (1) the water distribution system sprays seawater; (2) raw steam is input into the evaporation tube of the middle effect evaporator; (3) the steam condenses in the evaporation tube and transmits heat, and the outside of the evaporation tube absorbs heat to produce evaporation; (4) the new steam is transported to the evaporation tubes on both sides. The outside of the tube absorbs heat and produces evaporation; (6) each effect evaporator repeats the evaporation and condensation process; (7) the distilled water enters the fresh water tank; (8) the concentrated brine enters the concentrated water tank.

[0039] The working principle of the seawater desalination system based on the high temperature of nuclear power plant seawater provided in this embodiment is as follows:

[0040] During hot seasons, the plant water supply for nuclear power units flows through the heat pump unit evaporator, where the heat pump medium absorbs heat, lowering the plant water temperature. The cooled plant water then passes through the chiller heat exchanger, removing the heat load from the chiller system and ensuring the normal operation of the nuclear power unit's cold chain system.

[0041] The heat pump medium flowing through the evaporator, after the compressor performs work, further increases its temperature and pressure, and then enters the condenser to heat the desalinated circulating water. The heat pump medium flowing out of the condenser is cooled by the throttle valve and then re-enters the evaporator to absorb heat, forming a closed cycle.

[0042] After the desalinated circulating water heated in the condenser enters the flash tank, part of it vaporizes into steam and enters the low-temperature multi-effect desalination component, and part of it condenses into liquid water.

[0043] The steam entering the low-temperature multi-effect desalination unit is condensed and releases heat to form condensed water, which re-enters the heat pump condenser together with the condensed water in the flash tank to form a closed cycle.

[0044] The steam entering the low-temperature multi-effect desalination component heats the raw seawater to form first-effect steam, which drives the operation of the low-temperature multi-effect distillation desalination component to achieve seawater desalination.

[0045] Example 2

[0046] In a typical embodiment of the present invention, a method for desalination of seawater based on high temperature of nuclear power plant seawater is provided, comprising:

[0047] After the seawater is cooled by the evaporator of the heat pump unit, it enters the cold water heat exchanger to provide a cold source for the cold water of the nuclear power plant; after the circulating water is heated by the condenser of the heat pump unit, it enters the flash tank. Under the action of the flash tank, part of the heated circulating water is vaporized into steam and enters the low-temperature multi-effect distillation component to provide steam for the seawater desalination process, and part of it is condensed into liquid water.

[0048] This embodiment uses the principle that the evaporator of the heat pump unit absorbs heat and the condenser releases heat to cool the seawater used in the nuclear power plant, providing heat for seawater desalination, and then generates steam through flash evaporation technology to provide steam for the seawater desalination process.

[0049] Furthermore, the liquid water produced by the flash tank and the condensed water produced by the low-temperature multi-effect distillation component are used as circulating water.

[0050] The seawater desalination method provided in this embodiment is proposed based on the high temperature of seawater used in nuclear power plants. It couples seawater desalination technology with heat pump technology and flash evaporation technology. This method reduces the seawater temperature in extremely high temperature weather and realizes seawater desalination production, ensuring the normal operation of nuclear power units and improving the economy and safety of nuclear power units.

[0051] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A seawater desalination system based on high temperature seawater from a nuclear power plant, characterized in that: It includes a nuclear power plant chiller assembly, a heat pump unit, and a seawater desalination assembly. The nuclear power plant chiller assembly is coupled to the evaporation end of the heat pump unit, and the seawater desalination assembly is coupled to the condensation end of the heat pump unit. The nuclear power plant chiller assembly includes a chilled water heat exchanger, the seawater intake is connected to the evaporator via a pipeline, and the seawater outlet of the evaporator is connected to the chilled water heat exchanger via a pipeline. After the seawater is cooled by the evaporation end of the heat pump unit, it provides cooling capacity for the nuclear power plant chiller. After the circulating water is heated by the condenser of the heat pump unit, it enters the flash tank. Part of it is vaporized into steam and enters the low-temperature multi-effect distillation assembly to provide steam for the seawater desalination process, and part of it is condensed into liquid water. The condensed water after the steam condensation in the low-temperature multi-effect distillation seawater desalination device and the condensed water generated in the flash tank are merged and then enter the condenser to be circulated and used as circulating water. The heat pump unit includes a compressor, a condenser, a throttle valve and an evaporator connected in sequence through pipelines, and the evaporator is also connected to the compressor to form a refrigerant circulation loop; the seawater desalination component includes a flash tank and a low-temperature multi-effect distillation seawater desalination device; the flash tank is provided with a circulating water inlet, a condensed water outlet and a steam outlet, wherein the circulating water inlet and the condensed water outlet are connected to the condenser through pipelines, and the steam outlet is connected to the low-temperature multi-effect distillation seawater desalination device; the condensed water outlet of the low-temperature multi-effect distillation seawater desalination device is connected to the condenser.

2. The seawater desalination system based on high temperature seawater of a nuclear power plant according to claim 1, characterized in that: The cold water heat exchanger adopts a plate-type heat tube heat exchanger, a shell and tube heat exchanger or a sleeve-type heat exchanger.

3. The seawater desalination system based on high temperature seawater of a nuclear power plant according to claim 1, characterized in that: The evaporator and condenser are shell and tube heat exchangers.

4. A method for desalination of seawater based on high temperature seawater in a nuclear power plant, implemented by using the seawater desalination system according to any one of claims 1 to 3, characterized in that: include: After the seawater is cooled by the evaporator of the heat pump unit, it enters the cold water heat exchanger to provide a cold source for the cold water of the nuclear power plant; after the circulating water is heated by the condenser of the heat pump unit, it enters the flash tank. Under the action of the flash tank, part of the heated circulating water is vaporized into steam and enters the low-temperature multi-effect distillation component to provide steam for the seawater desalination process, and part of it is condensed into liquid water.

5. The seawater desalination method based on high temperature seawater in a nuclear power plant according to claim 4, characterized in that: The liquid water produced by the flash tank and the condensed water produced by the low-temperature multi-effect distillation component are used as circulating water.

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