Seawater desalination system and method based on heat film coupling

Abstract

This application relates to a seawater desalination system and method based on thermal-membrane coupling. The system includes a flue gas waste heat extraction device, a thermal desalination device, and a membrane desalination device; the flue gas waste heat extraction device is connected to both the thermal and membrane desalination devices; the flue gas waste heat extraction device is used to absorb the heat from the flue gas generated during the operation of the coal-fired power unit and generate a heat transfer medium adapted to the heat of the flue gas; the thermal desalination device is used to convert seawater entering the thermal desalination device into concentrated brine and primary freshwater using the heat transfer medium as the driving heat source; the membrane desalination device is used to desalinate the seawater entering the membrane desalination device to obtain secondary freshwater; the temperature of the concentrated brine is higher than that of the seawater entering the membrane desalination device; the seawater is preheated by the heat transfer medium and concentrated brine before entering the membrane desalination device, and the use of this system can improve the system energy efficiency.

Description

Technical Field

[0001] This application relates to the field of industrial energy-saving technology, and in particular to a seawater desalination system and method based on thermal film coupling. Background Technology

[0002] With the escalating global energy crisis and the growing scarcity of freshwater resources, seawater desalination technology, as a key means of solving the freshwater supply problem in coastal areas, has attracted widespread attention in its research and application. Among them, thermal seawater desalination technology and membrane seawater desalination technology are the mainstream technical routes. Thermal technology achieves desalination by driving seawater evaporation and condensation with thermal energy, and has the characteristics of stable water quality and strong resistance to pollution, but it requires a large amount of fossil energy or high-quality steam, resulting in high operating costs. Membrane technology achieves desalination by driving seawater through a reverse osmosis membrane with a high-pressure pump, and has the advantages of relatively low energy consumption and high modularity, but it is sensitive to the feed water temperature. Under low temperature conditions, the membrane flux decreases significantly, requiring additional heating to improve efficiency.

[0003] In traditional seawater desalination systems, thermal and membrane methods typically operate independently. The concentrated brine and waste heat from flue gas generated by the thermal unit are not effectively utilized, resulting in energy waste. Meanwhile, the membrane unit requires separate preheating of seawater via boiler or electric heater, further increasing energy consumption. This "thermal-membrane separation" operating mode leads to low overall system energy efficiency. Summary of the Invention

[0004] Therefore, it is necessary to provide a seawater desalination system and method based on thermal film coupling that can improve system energy efficiency in response to the above-mentioned technical problems.

[0005] In a first aspect, this application provides a seawater desalination system based on thermal membrane coupling, the system comprising a flue gas waste heat extraction device, a thermal desalination device, and a membrane desalination device; the flue gas waste heat extraction device is connected to the thermal desalination device and the membrane desalination device respectively;

[0006] The flue gas waste heat extraction equipment is used to absorb the heat from the flue gas generated during the operation of the coal-fired power unit and generate a heat medium that is compatible with the heat from the flue gas.

[0007] The thermal desalination equipment is used to convert seawater entering the thermal desalination equipment into concentrated brine and primary freshwater using the thermal medium as a driving heat source.

[0008] The membrane desalination equipment is used to desalinate seawater entering the membrane desalination equipment to obtain desalinated secondary freshwater; the temperature of the concentrated brine is higher than that of the seawater entering the membrane desalination equipment; the seawater is preheated by the heat transfer medium and the concentrated brine before entering the membrane desalination equipment.

[0009] In one embodiment, the system further includes a vapor compression heating device connected to the membrane desalination equipment;

[0010] The steam compression heating device is used to reheat the seawater that has been preheated based on the heat medium and the concentrated brine, and then transport the reheated seawater to the membrane desalination device.

[0011] In one embodiment, the heat medium includes a first heat medium;

[0012] The thermal desalination equipment is specifically used to convert seawater entering the thermal desalination equipment into concentrated brine and primary freshwater, using the first heat medium as the driving heat source.

[0013] In one embodiment, the flue gas waste heat extraction device includes a first flue gas heat exchange component;

[0014] The first flue gas heat exchange component is connected to the thermal desalination equipment and is used to extract the heat generated by the first flue gas during the operation of the coal-fired power unit and generate a first heat medium that is compatible with the heat of the first flue gas.

[0015] The first heat medium is transferred to the thermal desalination device.

[0016] In one embodiment, the heat medium further includes a second heat medium;

[0017] The membrane desalination equipment is specifically used to desalinate seawater entering the membrane desalination equipment to obtain desalinated secondary freshwater; the seawater is preheated by the second heat medium and the concentrated brine before entering the membrane desalination equipment; the temperature of the first heat medium is higher than the temperature of the second heat medium.

[0018] In one embodiment, the flue gas waste heat extraction device further includes a second flue gas heat exchange component;

[0019] The second flue gas heat exchange component is connected to the membrane desalination equipment and is used to extract the heat generated by the second flue gas during the operation of the coal-fired power unit and generate a second heat medium that is compatible with the heat of the second flue gas.

[0020] The second heat medium is transferred to the membrane desalination device.

[0021] In one embodiment, the system further includes an intelligent coordination control device;

[0022] The intelligent coordination and control device is connected to the first flue gas heat exchange component and the second flue gas heat exchange component, and is used to obtain the position information of the first flue gas heat exchange component and the second flue gas heat exchange component respectively.

[0023] The first flue gas heat extraction amount corresponding to the first flue gas heat exchange component and the second flue gas heat extraction amount corresponding to the second flue gas heat exchange component are determined based on the location information.

[0024] The first flue gas heat exchange component is controlled to extract the first flue gas heat generated during the operation of the coal-fired power unit according to the first flue gas heat extraction amount.

[0025] The second flue gas heat exchange component is controlled to extract the second flue gas heat generated during the operation of the coal-fired power unit based on the second flue gas heat extraction amount.

[0026] In one embodiment, the intelligent coordination control device is also connected to the thermal desalination device and the membrane desalination device, respectively;

[0027] The intelligent coordination and control equipment is used to acquire freshwater generation and unit information of the coal-fired power unit;

[0028] By combining the freshwater production rate with the unit information, adjustments are made to the first flue gas heat extraction rate, the second flue gas heat extraction rate, and the operating information corresponding to the thermal desalination equipment and the membrane desalination equipment, respectively.

[0029] In one embodiment, the thermal desalination equipment is specifically a low-temperature multi-effect distillation equipment.

[0030] Secondly, this application also provides a seawater desalination method based on thermal film coupling, the method comprising:

[0031] The waste heat extraction equipment absorbs the heat from the flue gas generated during the operation of the coal-fired power unit and generates a heat medium that is compatible with the heat from the flue gas.

[0032] The thermal desalination equipment uses the aforementioned heat medium as a driving heat source to convert seawater entering the thermal desalination equipment into concentrated brine and primary freshwater;

[0033] The membrane desalination equipment desalinates the seawater entering the equipment to obtain desalinated secondary freshwater; the temperature of the concentrated brine is higher than that of the seawater entering the membrane desalination equipment; the seawater is preheated by the heat transfer medium and the concentrated brine before entering the membrane desalination equipment.

[0034] Thirdly, this application also provides a seawater desalination device, comprising:

[0035] The flue gas heat absorption module is used by the flue gas waste heat extraction equipment to absorb the flue gas heat generated during the operation of the coal-fired power unit and generate a heat medium that is compatible with the flue gas heat.

[0036] The first seawater conversion module is used in the thermal desalination equipment to convert seawater entering the thermal desalination equipment into concentrated brine and primary freshwater using the heat medium as the driving heat source.

[0037] The second seawater conversion module is used by the membrane desalination equipment to desalinate the seawater entering the membrane desalination equipment to obtain desalinated secondary freshwater; the temperature of the concentrated brine is higher than that of the seawater entering the membrane desalination equipment; the seawater is preheated by the heat medium and the concentrated brine before entering the membrane desalination equipment.

[0038] Fourthly, this application also provides a computer device. The computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the method described above.

[0039] Fifthly, this application also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program thereon, which, when executed by a processor, implements the steps of the method described above.

[0040] Sixthly, this application also provides a computer program product. The computer program product includes a computer program that, when executed by a processor, implements the steps of the method described above.

[0041] The aforementioned seawater desalination system and method based on thermal-membrane coupling achieves efficient cascaded energy utilization through the coupled design of flue gas waste heat extraction equipment and thermal-membrane desalination equipment. The waste heat from coal-fired power unit flue gas is used to generate a heat transfer medium to drive thermal desalination, avoiding the high energy consumption problem of traditional boiler heating. Simultaneously, the high-temperature brine discharged from the thermal desalination equipment, along with the heat transfer medium, provides dual preheating for the membrane desalination feedwater, significantly increasing the feedwater temperature of the membrane desalination equipment, thereby increasing membrane flux and reducing high-pressure pump power consumption. The brine waste heat recovery step replaces the electric heater in the traditional membrane unit, reducing additional energy consumption. The closed-loop circulation of the heat transfer medium between the flue gas waste heat extraction equipment and the thermal desalination equipment greatly improves the flue gas waste heat recovery rate. This design, through the thermal-mass coupling of the thermal and membrane desalination equipment, significantly improves the overall energy efficiency of the system. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1This is a schematic diagram of the structure of a seawater desalination system in one embodiment;

[0044] Figure 2 This is a schematic diagram of the seawater desalination system in another embodiment;

[0045] Figure 3 This is a schematic diagram showing the connection relationship of the first flue gas heat exchange component in one embodiment;

[0046] Figure 4 This is a schematic diagram showing the connection relationship of the second flue gas heat exchange component in one embodiment;

[0047] Figure 5 This is a schematic diagram of the connection relationship of the intelligent coordination control devices in one embodiment;

[0048] Figure 6 This is a schematic diagram of the connection relationship of the intelligent coordination control devices in another embodiment;

[0049] Figure 7 This is a schematic diagram of the seawater desalination system in yet another embodiment;

[0050] Figure 8 This is a schematic diagram of a seawater desalination method in one embodiment;

[0051] Figure 9 This is a structural block diagram of a seawater desalination device in one embodiment;

[0052] Figure 10 This is an internal structural diagram of a computer device in one embodiment.

[0053] Figure reference numerals: Flue gas waste heat extraction equipment-10; First flue gas heat exchange component-11; First flue gas heat exchange component-12; Thermal desalination equipment-20; Membrane desalination equipment-30; Steam compression heating equipment-40; Intelligent coordination control equipment-50. Detailed Implementation

[0054] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0056] It should be noted that when one element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediary element. Furthermore, in the following embodiments, "connection" should be understood as "electrical connection," "communication connection," etc., if there is transmission of electrical signals or data between the connected objects.

[0057] When used herein, the singular forms of “a,” “an,” and “ / the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0058] As the background technology suggests, with the escalating global energy crisis and the increasing prominence of freshwater resource shortages, seawater desalination technology, as a key means of solving the freshwater supply problem in coastal areas, has received widespread attention for its research and application. Among them, thermal seawater desalination technology and membrane seawater desalination technology are the mainstream technical routes. Thermal technology achieves desalination by driving seawater evaporation and condensation with thermal energy, and has the characteristics of stable water quality and strong anti-pollution ability, but it requires the consumption of a large amount of fossil energy or high-quality steam, resulting in high operating costs. Membrane technology achieves desalination by driving seawater through a reverse osmosis membrane with a high-pressure pump, and has the advantages of relatively low energy consumption and high modularity, but it is sensitive to the feed water temperature. Under low temperature conditions, the membrane flux decreases significantly, requiring additional heating to improve efficiency.

[0059] In traditional seawater desalination systems, thermal and membrane methods typically operate independently. The concentrated brine and waste heat from flue gas generated by the thermal unit are not effectively utilized, resulting in energy waste. Meanwhile, the membrane unit requires separate preheating of seawater via boiler or electric heater, further increasing energy consumption. This "thermal-membrane separation" operating mode leads to low overall system energy efficiency.

[0060] For the reasons mentioned above, such as Figure 1As shown, this application provides a seawater desalination system based on thermal membrane coupling. The system includes a flue gas waste heat extraction device 10, a thermal desalination device 20, and a membrane desalination device 30. The flue gas waste heat extraction device 10 is connected to the thermal desalination device 20 and the membrane desalination device 30, respectively. The flue gas waste heat extraction device 10 is used to absorb the heat from the flue gas generated during the operation of the coal-fired power unit and generate a heat medium adapted to the heat of the flue gas. The thermal desalination device 20 is used to convert the seawater entering the thermal desalination device 20 into concentrated brine and primary freshwater using the heat medium as the driving heat source. The membrane desalination device 30 is used to desalinate the seawater entering the membrane desalination device 30 to obtain secondary freshwater. The temperature of the concentrated brine is higher than that of the seawater entering the membrane desalination device 30. The seawater is preheated by the heat medium and concentrated brine before entering the membrane desalination device 30.

[0061] Among them, the flue gas waste heat extraction equipment 10 is a device used to absorb heat from the flue gas generated during the operation of the coal-fired power unit and convert it into a heat medium suitable for subsequent equipment.

[0062] The thermal desalination unit 20 uses a heat transfer medium as the driving heat source to convert seawater entering it into concentrated brine and primary freshwater through heating and evaporation. Examples of thermal desalination units 20 include multistage flash distillation (MSF), multiple effect distillation (MED), and mechanical vapor compression distillation (MVC). The membrane desalination unit 30 uses the selective permeability of a membrane to desalinate the incoming seawater, thereby obtaining secondary freshwater. Examples of membrane desalination units 30 include reverse osmosis (RO), membrane distillation (MD), and nanofiltration (NF). The concentrated brine is the salt water formed after the seawater has been treated in the thermal desalination unit 20, and its temperature is higher than that of the seawater entering the membrane desalination unit 30. The heat transfer medium is generated by the flue gas waste heat extraction device 10 after absorbing heat from the flue gas. It is a substance that can transfer heat and provide a driving heat source for the thermal desalination device 20. It can indirectly extract heat through a heat exchanger, isolate impurities in the flue gas, and generate a clean and stable heat transfer medium (such as heat transfer oil or softened water) that can be directly input into downstream equipment (such as the preheater of a membrane desalination device) to reduce the risk of equipment corrosion.

[0063] Specifically, in this embodiment, the seawater desalination system mainly consists of a flue gas waste heat extraction device 10, a thermal desalination device 20, and a membrane desalination device 30, with the flue gas waste heat extraction device 10 connected to both the thermal desalination device 20 and the membrane desalination device 30. During system operation, the flue gas waste heat extraction device 10 begins operation, absorbing the heat carried by the flue gas generated during the operation of the coal-fired power unit. After processing, it generates a heat transfer medium adapted to the heat of the flue gas. This heat transfer medium is then transported to the thermal desalination device 20, serving as a driving heat source to cause physical changes in the seawater entering the device. Part of the seawater is converted into concentrated brine, and the other part becomes primary freshwater. The membrane desalination device 30 then desalinates the seawater entering it, producing secondary freshwater. Simultaneously, because the temperature of the concentrated brine is higher than that of the seawater entering the membrane desalination device 30, the seawater is preheated by the heat transfer medium and concentrated brine before entering the membrane desalination device 30 to improve the efficiency of the subsequent membrane desalination process.

[0064] In this embodiment, the coupled design of the flue gas waste heat extraction device 10 and the thermal-membrane desalination device 30 achieves efficient cascaded energy utilization: the waste heat from the flue gas of the coal-fired power unit is used to generate a heat medium to drive the thermal desalination, avoiding the high energy consumption problem of traditional boiler heating. Simultaneously, the high-temperature concentrated brine discharged from the thermal desalination device 20, along with the heat medium, provides dual preheating for the membrane desalination feedwater, significantly increasing the feedwater temperature of the membrane desalination device 30, thereby increasing membrane flux and reducing high-pressure pump power consumption. The concentrated brine waste heat recovery step replaces the electric heater of the traditional membrane unit, reducing additional energy consumption. The heat medium circulation between the flue gas waste heat extraction device 10 and the thermal desalination device 20 forms a closed loop, significantly improving the flue gas waste heat recovery rate. This design, through the thermo-mass coupling of the thermal desalination device 20 and the membrane desalination device 30, significantly improves the overall energy efficiency of the system.

[0065] In one embodiment, such as Figure 2 As shown, the system also includes a steam compression heating device 40 connected to the membrane desalination device 30; the steam compression heating device 40 is used to reheat the seawater after it has been preheated based on the heat medium and concentrated brine, and to transport the reheated seawater to the membrane desalination device 30.

[0066] The vapor compression heating device 40 is connected to the membrane desalination device 30. It is a device that reheats the seawater after it has been preheated by the heat medium and concentrated brine, and then transports the heated seawater to the membrane desalination device 30. For example, the vapor compression heating device 40 can precisely raise the temperature of the seawater to the optimal operating temperature range (25-35℃) of the reverse osmosis membrane.

[0067] Specifically, the system in this embodiment also includes a vapor compression heating device 40 connected to the membrane desalination unit 30. After the seawater is preheated by the heat medium and concentrated brine, it enters the vapor compression heating device 40. The vapor compression heating device 40 reheats the seawater, further increasing its temperature to precisely reach the optimal operating temperature range of the reverse osmosis membrane (25-35°C), making it more suitable for membrane desalination. The reheated seawater is then transported to the membrane desalination unit 30 for desalination treatment to obtain secondary freshwater.

[0068] In this embodiment, the steam compression heating device 40 reheats the preheated seawater, further increasing the inlet water temperature of the membrane desalination device 30, enhancing the membrane desalination effect, and improving the freshwater yield and quality.

[0069] In one embodiment, the heat medium includes a first heat medium; the thermal desalination device 20 is specifically used to use the first heat medium as a driving heat source to convert seawater entering the thermal desalination device 20 into concentrated brine and primary freshwater.

[0070] The first heat medium is generated by extracting heat from the first flue gas in a specific part of the flue gas waste heat extraction device 10, and is specifically used as the driving heat source for the thermal desalination device 20. For example, the flue gas waste heat extraction device 10 can recover high-grade heat energy in the high-temperature section (about 120-200°C) of the coal-fired power unit during operation, and generate hot water or low-pressure steam at 90-150°C as the first heat medium.

[0071] Specifically, in this embodiment, the heat medium is specifically divided into a first heat medium. When the flue gas waste heat extraction device 10 is working, it extracts heat from the flue gas generated by the coal-fired power unit to generate the heat medium. The heat medium specifically used in the thermal desalination device 20 is defined as the first heat medium. The thermal desalination device 20 uses the first heat medium as its driving heat source. When seawater enters the thermal desalination device 20, the first heat medium transfers heat to the seawater, causing physical changes such as evaporation, ultimately converting the seawater into concentrated brine and primary freshwater.

[0072] In this embodiment, the first heat medium is clearly distinguished for use in thermal desalination, which makes the distribution and utilization of heat more precise and improves the stability and efficiency of the thermal desalination process.

[0073] In one embodiment, such as Figure 3 As shown, the flue gas waste heat extraction device 10 includes a first flue gas heat exchange component 11; the first flue gas heat exchange component 11 is connected to the thermal desalination device 20 and is used to extract the heat generated by the first flue gas during the operation of the coal-fired power unit and generate a first heat medium adapted to the heat of the first flue gas; and to transfer the first heat medium to the thermal desalination device 20.

[0074] The first flue gas heat exchange component 11 is connected to the thermal desalination device 20 in the flue gas waste heat extraction device 10. It is used to extract the heat from the first flue gas generated during the operation of the coal-fired power unit and generate a first heat medium adapted to the heat from the first flue gas. For example, the first flue gas heat exchange component 11 can be a high-temperature flue gas heat exchanger installed in the high-temperature section (about 120-200°C) after the air preheater and before the dust collector to recover higher-grade heat energy and generate hot water or low-pressure steam at 90-150°C as the first heat medium.

[0075] Specifically, in this embodiment, the flue gas waste heat extraction device 10 includes a first flue gas heat exchange component 11. The first flue gas heat exchange component 11 is connected to the thermal desalination device 20. During the operation of the coal-fired power unit, it captures heat from the first flue gas generated by the unit. Through a specific heat exchange process, the heat of the first flue gas is extracted, and a first heat medium matching the heat of the first flue gas is generated. The generated first heat medium is then transferred to the thermal desalination device 20 to provide the necessary heat source for the thermal desalination process, enabling the seawater entering the thermal desalination device 20 to be converted into concentrated brine and primary freshwater.

[0076] In this embodiment, the first flue gas heat exchange component 11 can selectively extract heat from the first flue gas and generate a first heat medium, providing a stable heat source for thermal desalination and ensuring the normal operation of thermal desalination.

[0077] In one embodiment, the heat medium further includes a second heat medium; the membrane desalination device 30 is specifically used to desalinate seawater entering the membrane desalination device 30 to obtain desalinated secondary freshwater; the seawater is preheated by the second heat medium and concentrated brine before entering the membrane desalination device 30; the temperature of the first heat medium is higher than the temperature of the second heat medium.

[0078] The second heat medium is generated by the waste heat extraction device 10 after extracting heat from the second flue gas, and is used to preheat the seawater entering the membrane desalination device 30.

[0079] Specifically, in this embodiment, the heat medium also includes a second heat medium. When the membrane desalination device 30 desalinates seawater, the seawater needs to be preheated before entering the device. In addition to preheating with concentrated brine, preheating is also performed using a second heat medium. The flue gas waste heat extraction device 10 extracts heat from the second flue gas generated by the coal-fired power unit and generates a second heat medium compatible with the heat from the second flue gas. The second heat medium and the concentrated brine work together to preheat the seawater entering the membrane desalination device 30, raising its temperature to improve the efficiency of membrane desalination. Furthermore, the temperature of the first heat medium is higher than that of the second heat medium to meet the heat and temperature requirements of different devices.

[0080] In this embodiment, the second heat medium participates in the preheating of seawater and works synergistically with concentrated brine to further increase the inlet water temperature of the membrane desalination equipment 30. At the same time, the heat medium at different temperatures is rationally distributed, which improves the rationality of energy utilization.

[0081] In one embodiment, such as Figure 4 As shown, the flue gas waste heat extraction device 10 also includes a second flue gas heat exchange component 12; the second flue gas heat exchange component 12 is connected to the membrane desalination device 30 and is used to extract the second flue gas heat generated during the operation of the coal-fired power unit and generate a second heat medium adapted to the second flue gas heat; and transfer the second heat medium to the membrane desalination device 30.

[0082] The second flue gas heat exchange component 12 is used to extract the heat generated by the second flue gas during the operation of the coal-fired power unit and generate a second heat medium adapted to the heat of the second flue gas. For example, the second flue gas heat exchange component 12 can be a low-temperature flue gas heat exchanger installed in the low-temperature section (about 80-120℃) before the desulfurization tower, which recovers low-grade heat energy through corrosion-resistant design and generates hot water at 50-85℃ as the second heat medium.

[0083] Specifically, the flue gas waste heat extraction device 10 in this embodiment also includes a second flue gas heat exchange component 12, which is connected to the membrane desalination device 30. During the operation of the coal-fired power unit, the second flue gas heat exchange component 12 is responsible for capturing the heat in the second flue gas generated by the unit. Through a specific heat exchange mechanism, the heat of the second flue gas is extracted, thereby generating a second heat medium adapted to the heat of the second flue gas. The generated second heat medium is transferred to the relevant part of the membrane desalination device 30 to preheat the seawater entering the membrane desalination device 30, raising the seawater temperature together with the concentrated brine, creating favorable conditions for the subsequent membrane desalination process. For example, the first flue gas heat exchange component 11 can be a high-temperature flue gas heat exchanger installed in the high-temperature section (about 120-200°C) after the air preheater and before the dust collector, recovering higher-grade heat energy to generate hot water or low-pressure steam at 90-150°C as the first heat medium. The second flue gas heat exchange component 12 can be a low-temperature flue gas heat exchanger installed in the low-temperature section (approximately 80-120℃) before the desulfurization tower. Through corrosion-resistant design, it recovers low-grade heat energy and generates hot water at 50-85℃ as the second heat medium. This design solves the problems of low-temperature flue gas corrosion and heat extraction, achieving complete utilization of waste heat.

[0084] In this embodiment, the second flue gas heat exchange component 12 is specifically designed to extract heat from the second flue gas to generate a second heat medium for seawater preheating, thereby expanding the utilization range of flue gas waste heat and improving the energy utilization efficiency of the entire system.

[0085] In one embodiment, such as Figure 5As shown, the system also includes an intelligent coordination control device 50; the intelligent coordination control device 50 is connected to the first flue gas heat exchange component 11 and the second flue gas heat exchange component 12, and is used to acquire the position information corresponding to the first flue gas heat exchange component 11 and the second flue gas heat exchange component 12 respectively; determine the first flue gas heat extraction amount corresponding to the first flue gas heat exchange component 11 and the second flue gas heat extraction amount corresponding to the second flue gas heat exchange component 12 based on the position information; control the first flue gas heat exchange component 11 to extract the first flue gas heat generated during the operation of the coal-fired power unit according to the first flue gas heat extraction amount; and control the second flue gas heat exchange component 12 to extract the second flue gas heat generated during the operation of the coal-fired power unit according to the second flue gas heat extraction amount.

[0086] Among them, the intelligent coordination and control device 50 is connected to the first flue gas heat exchange component 11 and the second flue gas heat exchange component 12. It can obtain their position information and determine the first flue gas heat extraction amount and the second flue gas heat extraction amount based on this information. It can also control the flue gas heat exchange component to extract flue gas heat based on the extraction amount. At the same time, it is connected to the thermal desalination device 20 and the membrane desalination device 30, and can obtain the freshwater generation amount and unit information and make adjustments.

[0087] Specifically, in this embodiment, the system is equipped with an intelligent coordination control device 50, which is connected to the first flue gas heat exchange component 11 and the second flue gas heat exchange component 12. The intelligent coordination control device 50 first acquires the location information of each of the first and second flue gas heat exchange components 11 and 12. Based on this location information, it can accurately determine the first flue gas heat extraction amount corresponding to the first flue gas heat exchange component 11 and the second flue gas heat extraction amount corresponding to the second flue gas heat exchange component 12. Then, based on the determined first flue gas heat extraction amount, it controls the first flue gas heat exchange component 11 to extract the first flue gas heat generated during the operation of the coal-fired power unit, and controls the second flue gas heat exchange component 12 to extract the second flue gas heat based on the second flue gas heat extraction amount. For example, the first flue gas heat exchange component 11 is installed in the high-temperature section (approximately 120-200℃) after the air preheater and before the dust collector, and the second flue gas heat exchange component 12 is installed in the low-temperature section (approximately 80-120℃) before the desulfurization tower. After the intelligent coordination control device 50 obtains the position information of the two components, it can determine how much flue gas heat the first flue gas heat exchange component 11 and the second flue gas heat exchange component 12 need to absorb based on the specific positions represented by the position information. Thus, it controls the first flue gas heat exchange component 11 to extract the first flue gas heat generated during the operation of the coal-fired power unit based on the first flue gas heat extraction amount, and controls the second flue gas heat exchange component 12 to extract the second flue gas heat generated during the operation of the coal-fired power unit based on the second flue gas heat extraction amount.

[0088] In this embodiment, the intelligent coordination control device 50 achieves precise control and coordination of flue gas heat extraction and equipment operation, and dynamically adjusts parameters according to actual conditions, thereby improving the stability and operating efficiency of the system.

[0089] In one embodiment, such as Figure 6 As shown, the intelligent coordination control device 50 is also connected to the thermal desalination device 20 and the membrane desalination device 30 respectively; the intelligent coordination control device 50 is used to acquire the freshwater generation amount and the unit information of the coal-fired power unit; and to perform information analysis by combining the freshwater generation amount and the unit information, and to adjust the first flue gas heat extraction amount, the second flue gas heat extraction amount, and the corresponding operating information of the thermal desalination device 20 and the membrane desalination device 30 respectively.

[0090] Among them, the freshwater production volume is the total amount of freshwater produced by the thermal desalination unit 20 and the membrane desalination unit 30 during operation. Unit information refers to various relevant data and information generated by the coal-fired power unit during operation, such as unit load and operating status.

[0091] Specifically, the intelligent coordination and control device 50 is connected not only to the flue gas heat exchange components but also to the thermal desalination unit 20 and the membrane desalination unit 30, respectively. During operation, it continuously acquires information on freshwater production and the coal-fired power unit's unit status. Through comprehensive analysis of this information, the intelligent coordination and control device 50 can understand the overall operation of the seawater desalination system and the working status of the coal-fired power unit. Based on the analysis results, it can further optimize and adjust the heat extraction rates of the first and second flue gas, and also adjust the corresponding operating information of the thermal desalination unit 20 and the membrane desalination unit 30, such as the equipment's operating parameters and operating time, to ensure that the entire system maintains optimal operating conditions under different operating conditions, achieving efficient and stable freshwater production.

[0092] In this embodiment, the system is analyzed and adjusted based on the freshwater production and unit information, enabling it to better adapt to different operating conditions and further improving the overall performance and freshwater production efficiency of the system.

[0093] In one embodiment, the thermal desalination device 20 is specifically a low-temperature multi-effect distillation device.

[0094] Among them, the low-temperature multi-effect distillation equipment is a thermal desalination device 20, which realizes seawater desalination by evaporating and condensing seawater in multiple effects with gradually decreasing temperatures.

[0095] Specifically, in this embodiment, the thermal desalination device 20 employs a low-temperature multi-effect distillation system. During the operation of the seawater desalination system, the low-temperature multi-effect distillation system uses a first heat medium as the driving heat source. After seawater enters the system, it undergoes evaporation and condensation processes sequentially in multiple effects with gradually decreasing temperatures. In each effect, the seawater absorbs heat transferred by the first heat medium and evaporates. The resulting steam condenses into fresh water in subsequent effects, while the remaining seawater gradually concentrates its salt content to form brine. Through this multi-effect evaporation and condensation cycle, the low-temperature multi-effect distillation system can efficiently convert seawater into brine and primary fresh water, achieving the purpose of seawater desalination.

[0096] In this embodiment, a low-temperature multi-effect distillation device is used as the thermal desalination device 20, which has the advantages of low energy consumption and good water quality. It can stably provide primary fresh water to the system and improve the performance of the entire seawater desalination system.

[0097] In one embodiment, such as Figure 8 As shown, a seawater desalination method based on thermal film coupling is also provided, including:

[0098] Step S802: The flue gas waste heat extraction equipment absorbs the heat generated by the flue gas during the operation of the coal-fired power unit and generates a heat medium that is compatible with the heat of the flue gas.

[0099] Step S804: The thermal desalination equipment uses a heat transfer medium as the driving heat source to convert seawater entering the thermal desalination equipment into concentrated brine and primary freshwater.

[0100] Step S806: The membrane desalination equipment desalinates the seawater entering the membrane desalination equipment to obtain desalinated secondary freshwater; the temperature of the concentrated brine is higher than that of the seawater entering the membrane desalination equipment; the seawater is preheated by a heat transfer medium and concentrated brine before entering the membrane desalination equipment.

[0101] Specifically, the core of this embodiment lies in achieving cascaded energy utilization and maximizing system energy efficiency through multi-stage energy coupling: First, a waste heat recovery device (such as a finned tube heat exchanger or a heat pipe heat exchanger) is used to extract the heat energy from the high-temperature flue gas emitted by the coal-fired power unit, converting it into a heat medium (such as heat transfer oil or steam). This avoids thermal pollution caused by direct flue gas emissions and reduces the dependence of traditional heat sources on fossil fuels. Subsequently, the heat medium, as the driving heat source, enters a low-temperature multi-effect distillation device or a mechanical compression distillation device to heat seawater to the evaporation temperature. After this heating, high-purity primary freshwater is produced through a multi-stage flash evaporation and condensation process, while simultaneously generating concentrated brine with high salt content and high temperature. At the same time, the feed seawater first flows through a second heat medium for heat exchange, and then flows through a concentrated brine preheater to exchange heat with concentrated brine at a temperature of 35°C to 50°C, significantly increasing the feed water temperature and thus greatly reducing the power consumption of the high-pressure pump in the reverse osmosis membrane system. The pretreated seawater (a combination of multi-media filtration and ultrafiltration processes) then enters the reverse osmosis membrane system. The reverse osmosis membrane module, under high pressure, achieves a desalination rate exceeding standard requirements, producing secondary freshwater that meets drinking water standards. The reverse osmosis concentrate can be reused in the thermal system or used as industrial salt feedstock, forming a closed-loop energy flow chain: "flue gas waste heat → heat transfer medium → thermal water production → concentrated brine preheating → membrane deepening." This method effectively solves engineering challenges such as flue gas corrosion and membrane fouling by employing corrosion-resistant heat exchanger materials, ultrasonic anti-scaling technology, and an online chemical cleaning system. A heat transfer medium storage tank smooths temperature fluctuations, ensuring stable system operation under complex conditions. Its significant advantages lie in its significantly improved overall energy efficiency compared to traditional single-thermal or single-membrane methods, and a substantial reduction in operating costs. Furthermore, it reduces carbon dioxide emissions by a large amount per ton of freshwater produced, making it particularly suitable for coastal thermal power plants, industrial parks, and island scenarios. Through modular design, it can flexibly adapt to different scales of waste heat resources, achieving the dual goals of "zero-carbon" freshwater supply and concentrated brine resource utilization, providing an innovative integrated solution for energy-water coupling systems.

[0102] In one embodiment, the seawater desalination method further includes:

[0103] The steam compression heating equipment reheats the seawater that has been preheated with heat medium and concentrated brine, and then transports the reheated seawater to the membrane desalination equipment.

[0104] In one embodiment, the heat medium includes a first heat medium. In this embodiment, the thermal desalination device uses the first heat medium as a driving heat source to convert seawater entering the thermal desalination device into concentrated brine and primary freshwater.

[0105] In one embodiment, the flue gas waste heat extraction device includes a first flue gas heat exchange component. In this embodiment, the first flue gas heat exchange component is connected to a thermal desalination device to extract the heat generated by the first flue gas during the operation of the coal-fired power unit and generate a first heat medium adapted to the heat of the first flue gas; the first heat medium is then transferred to the thermal desalination device.

[0106] In one embodiment, the heat medium further includes a second heat medium. In this embodiment, the membrane desalination equipment desalinates the seawater entering the membrane desalination equipment to obtain desalinated secondary freshwater. The seawater is preheated by the second heat medium and concentrated brine before entering the membrane desalination equipment. The temperature of the first heat medium is higher than the temperature of the second heat medium.

[0107] In one embodiment, the flue gas waste heat extraction device further includes a second flue gas heat exchange component. In this embodiment, the second flue gas heat exchange component is connected to the membrane desalination device, extracts the second flue gas heat generated during the operation of the coal-fired power unit, and generates a second heat medium adapted to the second flue gas heat; the second heat medium is then transferred to the membrane desalination device.

[0108] In one embodiment, the intelligent coordination and control device is connected to the first flue gas heat exchange component and the second flue gas heat exchange component to obtain the location information corresponding to each of the first and second flue gas heat exchange components; based on the location information, it determines the first flue gas heat extraction amount corresponding to the first flue gas heat exchange component and the second flue gas heat extraction amount corresponding to the second flue gas heat exchange component; it controls the first flue gas heat exchange component to extract the first flue gas heat generated during the operation of the coal-fired power unit according to the first flue gas heat extraction amount; and it controls the second flue gas heat exchange component to extract the second flue gas heat generated during the operation of the coal-fired power unit according to the second flue gas heat extraction amount.

[0109] In one embodiment, the intelligent coordination control device is also connected to the thermal desalination device and the membrane desalination device respectively. In this embodiment, the intelligent coordination control device acquires the freshwater generation amount and the unit information of the coal-fired power unit; it performs information analysis by combining the freshwater generation amount and the unit information, and adjusts the first flue gas heat extraction amount, the second flue gas heat extraction amount, and the corresponding operating information of the thermal desalination device and the membrane desalination device respectively.

[0110] In one specific embodiment, a seawater desalination system based on thermal film coupling is also provided, such as... Figure 7 As shown, it consists of three main pieces of equipment: flue gas waste heat extraction equipment 10, thermal film coupling desalination main equipment 20, and intelligent coordination and control equipment 30.

[0111] Waste heat extraction equipment for flue gas: In view of the characteristic that the temperature of flue gas from coal-fired power units gradually decreases along the process, heat extraction devices are set up in two key temperature zones, high and low.

[0112] A first flue gas heat exchange component 11 is installed in the high-temperature section (approximately 120-200℃) after the air preheater and before the dust collector to recover higher-grade heat energy and generate hot water or low-pressure steam at 90-150℃ as the first heat medium.

[0113] A second flue gas heat exchange component 12 is installed in the low-temperature section (approximately 80-120℃) before the desulfurization tower. Through corrosion-resistant design, low-grade heat energy is recovered to generate hot water at 50-85℃ as the second heat medium. This design solves the problems of low-temperature flue gas corrosion and heat extraction, achieving complete utilization of waste heat.

[0114] Thermal film coupling desalination main equipment: This is the core innovation of this embodiment, which adopts a deep series coupling process route of "thermal method drive - waste heat cascade preheating - membrane method efficiency improvement".

[0115] The main equipment for thermal-film coupled desalination includes thermal desalination equipment and membrane desalination equipment. Among them, the thermal desalination equipment preferably uses a low-temperature multi-effect distillation device, and its first-effect heat source directly adopts the aforementioned first-grade heat source (high-temperature flue gas waste heat). This unit uses a low-grade heat source to produce high-quality freshwater and is the first step in energy conversion.

[0116] A unique three-stage preheating process was designed for membrane desalination equipment:

[0117] a) Primary preheating (low-temperature flue gas waste heat): The raw seawater first passes through the second flue gas heat exchange component and absorbs heat from the second heat medium.

[0118] b) Secondary preheating (residual heat from concentrated brine): The seawater after primary preheating enters the concentrated brine preheater, where it exchanges heat with the concentrated brine discharged from the last stage of the thermal desalination equipment, which is still maintained at a temperature of 35-50℃, to recover its sensible heat.

[0119] c) Three-stage preheating (precise temperature boosting by heat pump): After two-stage preheating, the seawater can selectively enter the heat pump heater, where heat is provided by the steam compression heating equipment 40 driven by plant power, precisely raising its temperature to the optimal operating temperature range of the reverse osmosis membrane (25-35℃).

[0120] Membrane desalination equipment: After the seawater has undergone the above three-stage preheating process, it enters the reverse osmosis unit. The significant increase in feed water temperature can greatly reduce the required operating pressure, increase membrane flux, and thus reduce its energy consumption per unit of produced water.

[0121] Intelligent Coordination and Control Equipment 50: Based on real-time monitoring of unit load, flue gas parameters, heat source temperature, and freshwater demand, it dynamically optimizes the operation of the entire system. For example, when the unit is in deep peak shaving or the high-temperature heat source is insufficient, it can adjust the distribution of low-temperature heat sources and start the heat pump to supplement, ensuring the stability of the RO inlet water temperature, thereby maintaining the efficient operation of the entire system.

[0122] For example, the solution in this embodiment can be implemented by the following embodiments, wherein:

[0123] Example 1: Medium-scale water production applicable to 300MW subcritical units.

[0124] Scenario and objective: A 30MW subcritical coal-fired power plant in a coastal area needs to be equipped with a freshwater production facility with a daily capacity of 15,000 tons, and needs to meet the peak-shaving requirements of the unit at 40%-100% load.

[0125] System Configuration:

[0126] Flue gas heat extraction: A high-temperature heat exchanger is installed in the 130℃ flue gas section to produce 95℃ hot water; a low-temperature heat exchanger is installed in the 105℃ flue gas section to produce 70℃ hot water.

[0127] De-preciation unit: Equipped with a triple-effect MED device (210) and a single-stage SWRO device (220).

[0128] Coupling method: 95℃ hot water drives the MED. The final effect of the MED, 45℃ concentrated brine, enters the concentrated brine preheater (E1). The raw seawater flows sequentially through the low-temperature flue gas preheater (E2, heat source 70℃ hot water) and the concentrated brine preheater (E1), and is heated to about 22℃. Then, it is heated to 30℃ by the heat pump heater (E3) driven by the steam compression heat pump (300) before entering the RO unit.

[0129] Example 2: Large-scale combined hydropower applicable to 600MW supercritical units.

[0130] Scenario and objectives: A 600MW supercritical unit is planned to be constructed as a cogeneration project with a daily freshwater production capacity of 30,000 tons, requiring high water recovery rate and optimal economic scale effect.

[0131] System Configuration:

[0132] Flue gas heat recovery: recovering heat from 180℃ flue gas to generate 0.15MPa saturated steam; recovering heat from 115℃ flue gas to produce 85℃ hot water.

[0133] Desalination unit: Equipped with a five-effect MED device and a two-stage RO device (first-stage RO + second-stage RO).

[0134] Coupling method: Low-pressure steam drives a five-effect MED. MED brine (50℃) and 85℃ hot water are connected in series to preheat the feed to the first-stage RO. The concentrate from the first-stage RO enters the second-stage RO, where the feed is further preheated by the MED brine. A heat pump is used to precisely control the inlet temperature of the second-stage RO.

[0135] Example 3: Resource utilization applicable to near "zero emission" requirements.

[0136] Scenario and Objective: Based on Example 1, the region has high environmental protection requirements and needs to further treat the concentrated brine for resource utilization, with the goal of achieving near-zero wastewater discharge.

[0137] System Configuration: Following the system in Example 1, a concentrated brine evaporation and crystallization unit is added. The heat source required for this evaporator and crystallizer is preferentially driven by 70-85°C hot water (after being cooled by E2) generated by a low-temperature flue gas heat exchanger. If the heat is insufficient, it can be supplemented by a small amount of high-temperature heat source.

[0138] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0139] Based on the same inventive concept, this application also provides a seawater desalination apparatus for implementing the seawater desalination method described above. The solution provided by this apparatus is similar to the solution described in the above method; therefore, the specific limitations of one or more seawater desalination apparatus embodiments provided below can be found in the limitations of the seawater desalination method described above, and will not be repeated here.

[0140] In one exemplary embodiment, such as Figure 9 As shown, a seawater desalination device 900 based on thermal film coupling is provided, including: a flue gas heat absorption module 902, a first seawater conversion module 904, and a second seawater conversion module 906, wherein:

[0141] The flue gas heat absorption module 902 is used by the flue gas waste heat extraction equipment to absorb the flue gas heat generated during the operation of the coal-fired power unit and generate a heat medium that is compatible with the flue gas heat.

[0142] The first seawater conversion module 904 is used in thermal desalination equipment to convert seawater entering the thermal desalination equipment into concentrated brine and primary freshwater using a heat medium as the driving heat source.

[0143] The second seawater conversion module 906 is used by the membrane desalination equipment to desalinate the seawater entering the membrane desalination equipment to obtain desalinated secondary freshwater; the temperature of the concentrated brine is higher than that of the seawater entering the membrane desalination equipment; the seawater is preheated by heat medium and concentrated brine before entering the membrane desalination equipment.

[0144] Each module in the aforementioned seawater desalination device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the operations corresponding to each module.

[0145] In one exemplary embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 10 As shown, the computer device includes a processor, memory, input / output interfaces, a communication interface, a display unit, and an input device. The processor, memory, and input / output interfaces are connected via a system bus, and the communication interface, display unit, and input device are also connected to the system bus via the input / output interfaces. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The input / output interfaces are used for exchanging information between the processor and external devices. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, Near Field Communication (NFC), or other technologies. When the computer program is executed by the processor, it implements a seawater desalination method. The display unit is used to form a visually visible image and can be a display screen, a projection device, or a virtual reality imaging device. The display screen can be an LCD screen or an e-ink screen. The input device of the computer device can be a touch layer covering the display screen, or buttons, trackballs, or touchpads set on the casing of the computer device, or external keyboards, touchpads, or mice, etc.

[0146] Those skilled in the art will understand that Figure 10 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0147] In one embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the method described above.

[0148] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0149] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps of the method described above.

[0150] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0151] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these.

[0152] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0153] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A seawater desalination system based on thermal film coupling, characterized in that, The system includes a flue gas waste heat extraction device, a thermal desalination device, and a membrane desalination device; the flue gas waste heat extraction device is connected to the thermal desalination device and the membrane desalination device respectively; The flue gas waste heat extraction equipment is used to absorb the heat from the flue gas generated during the operation of the coal-fired power unit and generate a heat medium that is compatible with the heat from the flue gas. The thermal desalination equipment is used to convert seawater entering the thermal desalination equipment into concentrated brine and primary freshwater using the thermal medium as a driving heat source. The membrane desalination equipment is used to desalinate seawater entering the membrane desalination equipment to obtain desalinated secondary freshwater; the temperature of the concentrated brine is higher than that of the seawater entering the membrane desalination equipment; the seawater is preheated by the heat transfer medium and the concentrated brine before entering the membrane desalination equipment.

2. The system according to claim 1, characterized in that, The system also includes a steam compression heating device connected to the membrane desalination equipment; The steam compression heating device is used to reheat the seawater that has been preheated based on the heat medium and the concentrated brine, and then transport the reheated seawater to the membrane desalination device.

3. The system according to claim 1, characterized in that, The heat medium includes a first heat medium; The thermal desalination equipment is specifically used to convert seawater entering the thermal desalination equipment into concentrated brine and primary freshwater, using the first heat medium as the driving heat source.

4. The system according to claim 3, characterized in that, The flue gas waste heat extraction device includes a first flue gas heat exchange component; The first flue gas heat exchange component is connected to the thermal desalination equipment and is used to extract the heat generated by the first flue gas during the operation of the coal-fired power unit and generate a first heat medium that is compatible with the heat of the first flue gas. The first heat medium is transferred to the thermal desalination device.

5. The system according to claim 4, characterized in that, The heat medium also includes a second heat medium; The membrane desalination equipment is specifically used to desalinate seawater entering the membrane desalination equipment to obtain desalinated secondary freshwater; the seawater is preheated by the second heat medium and the concentrated brine before entering the membrane desalination equipment; the temperature of the first heat medium is higher than the temperature of the second heat medium.

6. The system according to claim 5, characterized in that, The flue gas waste heat extraction equipment also includes a second flue gas heat exchange component; The second flue gas heat exchange component is connected to the membrane desalination equipment and is used to extract the heat generated by the second flue gas during the operation of the coal-fired power unit and generate a second heat medium that is compatible with the heat of the second flue gas. The second heat medium is transferred to the membrane desalination device.

7. The system according to claim 6, characterized in that, The system also includes intelligent coordination and control equipment; The intelligent coordination and control device is connected to the first flue gas heat exchange component and the second flue gas heat exchange component, and is used to obtain the position information of the first flue gas heat exchange component and the second flue gas heat exchange component respectively. The first flue gas heat extraction amount corresponding to the first flue gas heat exchange component and the second flue gas heat extraction amount corresponding to the second flue gas heat exchange component are determined based on the location information. The first flue gas heat exchange component is controlled to extract the first flue gas heat generated during the operation of the coal-fired power unit according to the first flue gas heat extraction amount. The second flue gas heat exchange component is controlled to extract the second flue gas heat generated during the operation of the coal-fired power unit based on the second flue gas heat extraction amount.

8. The system according to claim 7, characterized in that, The intelligent coordination and control device is also connected to the thermal desalination device and the membrane desalination device respectively; The intelligent coordination and control equipment is used to acquire freshwater generation and unit information of the coal-fired power unit; By combining the freshwater production rate with the unit information, adjustments are made to the first flue gas heat extraction rate, the second flue gas heat extraction rate, and the operating information corresponding to the thermal desalination equipment and the membrane desalination equipment, respectively.

9. The system according to claim 1, characterized in that, The thermal desalination equipment is specifically a low-temperature multi-effect distillation equipment.

10. A seawater desalination method based on thermal film coupling, characterized in that, The method includes: The waste heat extraction equipment absorbs the heat from the flue gas generated during the operation of the coal-fired power unit and generates a heat medium that is compatible with the heat from the flue gas. The thermal desalination equipment uses the aforementioned heat medium as a driving heat source to convert seawater entering the thermal desalination equipment into concentrated brine and primary freshwater; The membrane desalination equipment desalinates the seawater entering the equipment to obtain desalinated secondary freshwater; the temperature of the concentrated brine is higher than that of the seawater entering the membrane desalination equipment; the seawater is preheated by the heat transfer medium and the concentrated brine before entering the membrane desalination equipment.

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