A multi-stage enhanced co2 hydrate method seawater desalination system and method based on LNG cold energy cascade utilization

Abstract

The application discloses a kind of based on LNG cold energy cascade utilization's multistage enhanced CO2 hydrate method seawater desalination system and method, belong to seawater desalination technical field, system includes following module: cold energy cascade module: using LNG cold energy will seawater precooling freeze desalination, and provide cold energy for hydrate generation;Microbubble enhanced generation module: improve gas mass transfer efficiency, by two-stage generation chamber cascade generation high-purity CO2 hydrate;Waste heat-flash decomposing module: high-purity CO2 hydrate is preheated by flue gas waste heat and decomposed, then CO2 and fresh water are obtained by using vacuum flash instantaneous decomposition.The application adopts the above-mentioned one based on LNG cold energy cascade utilization's multistage enhanced CO2 hydrate method seawater desalination system and method, by cold energy cascade utilization, mass transfer enhancement and energy coupling, so that fresh water production is improved, energy consumption is reduced, CO2 capture rate is higher, and is suitable for large-scale industrial application.

Description

Technical Field

[0001] This invention relates to the field of seawater desalination technology, and in particular to a multi-stage enhanced CO2 hydrate seawater desalination system and method based on the cascade utilization of LNG cold energy. Background Technology

[0002] Seawater desalination is a crucial approach to addressing global water scarcity. Among these technologies, hydrate-based desalination has become a research hotspot due to its ability to combine with CO2-rich industrial waste gas to achieve the dual goals of desalination and carbon capture. This technology separates water molecules from salt in seawater by forming cage-like hydrates (CO2·nH2O) with CO2, and then obtains fresh water by decomposing the hydrates. However, traditional hydrate-based seawater desalination technology faces three major bottlenecks in its industrial application:

[0003] 1) Low efficiency of cold energy utilization: LNG cold energy is only used for hydrate formation, and the potential of cryogenic temperature is not fully realized;

[0004] 2) Mass transfer limitation: The slow CO2 dissolution rate during the traditional bubbling process for hydrate formation results in a large volume of the formation chamber;

[0005] 3) High energy consumption in decomposition: The efficiency of single thermal decomposition or depressurization decomposition is insufficient, and the utilization rate of waste heat from flue gas is insufficient.

[0006] Although the patent with patent number CN106629903B proposes a two-stage generation chamber and refrigerant circulation, it does not solve the problems of poor cold energy utilization efficiency, slow hydrate generation kinetics, and insufficient waste heat utilization. Summary of the Invention

[0007] The purpose of this invention is to provide a multi-stage enhanced CO2 hydrate seawater desalination system and method based on the cascade utilization of LNG cold energy. Through the cascade utilization of cold energy, enhanced mass transfer and energy coupling, the freshwater production is increased, energy consumption is reduced, and CO2 capture rate is increased, making it suitable for large-scale industrial applications.

[0008] To achieve the above objectives, the present invention provides a multi-stage enhanced CO2 hydrate seawater desalination system based on the cascade utilization of LNG cold energy, comprising the following modules:

[0009] Cold energy cascade module: Utilizes LNG cold energy to precool seawater for freezing and desalination, and provides cold energy to support hydrate formation;

[0010] Microbubble enhanced generation module: Improves gas mass transfer efficiency and generates high-purity CO2 hydrate through a two-stage generation chamber;

[0011] Waste heat-flash decomposition module: High-purity CO2 hydrate is preheated and decomposed by waste heat from flue gas, and then instantaneously decomposed by vacuum flash evaporation to obtain CO2 and fresh water.

[0012] Preferably, the system also includes the following modules:

[0013] Intelligent control module: Real-time dynamic adjustment of refrigerant distribution, microbubble flow rate, and flash chamber vacuum.

[0014] Preferably, the cold energy cascade module includes an LNG storage tank, a first vaporization chamber, a second vaporization chamber, a dual refrigerant circuit, a spiral scrubber, and a seawater tank. The LNG storage tank is connected to the first vaporization chamber, the first vaporization chamber is connected to the second vaporization chamber, the second vaporization chamber is connected to a natural gas pipeline, the spiral scrubber is connected to the seawater tank, and the first and second vaporization chambers are respectively connected to the dual refrigerant circuit.

[0015] Preferably, the microbubble enhancement generation module includes a primary generation chamber, a gas separation chamber, a secondary generation chamber, a liquid separation chamber, a flue gas microbubble generator, and a high-purity CO2 microbubble generator. The flue gas microbubble generator is located in the primary generation chamber, the high-purity CO2 microbubble generator is located in the secondary generation chamber, the primary generation chamber is connected to the gas separation chamber, the gas separation chamber is connected to the secondary generation chamber, and the secondary generation chamber is connected to the liquid separation chamber.

[0016] Preferably, the primary generation chamber is connected to the spiral washer.

[0017] Preferably, the waste heat flash evaporation-decomposition module includes a flue gas waste heat exchange decomposition chamber, a vacuum flash evaporation chamber, a water storage tank, a steam jet pump, a flue gas tank, and a CO2 tank. The flue gas waste heat exchange decomposition chamber is connected in series with the vacuum flash evaporation chamber. The vacuum flash evaporation chamber is connected to the steam jet pump and the CO2 tank respectively. The outlet end of the vacuum flash evaporation chamber is connected to the water storage tank.

[0018] Preferably, the inlet end of the flue gas waste heat exchange decomposition chamber is connected to the liquid separation chamber, the CO2 gas tank is connected to the secondary generation chamber, the flue gas tank is connected to the flue gas waste heat exchange decomposition chamber, and the flue gas waste heat exchange decomposition chamber is connected to the primary generation chamber.

[0019] This invention also provides a multi-stage enhanced CO2 hydrate desalination method based on LNG cold energy cascade utilization, employing the aforementioned multi-stage enhanced CO2 hydrate desalination system based on LNG cold energy cascade utilization, comprising the following steps:

[0020] Step 1: In the LNG storage tank, the LNG absorbs heat and vaporizes into a gaseous state in the first and second vaporization chambers. During the vaporization process, cold energy is released and transferred to the environment of the spiral scrubber, the primary generation chamber and the secondary generation chamber through a dual refrigerant loop. The seawater is pre-cooled by the cold energy of LNG in the spiral scrubber, and the water in the seawater condenses into ice crystals. The salt remains in the liquid phase. The ice crystals are separated by the spiral scrubber to obtain high-salt seawater.

[0021] Step 2: The flue gas enters the flue gas waste heat exchange decomposition chamber to exchange heat with the hydrate to be decomposed. After heat exchange, the flue gas is pre-cooled by a refrigerant and enters the primary generation chamber. The high-salt seawater obtained in Step 1 is introduced into the primary generation chamber. The high-salt seawater reacts with CO2 generated by the flue gas microbubble generator in the primary generation chamber to generate low-concentration CO2 hydrate containing mixed gas. The low-concentration CO2 hydrate containing mixed gas enters the gas separation chamber. The mixed gas in the low-concentration CO2 hydrate containing mixed gas is separated in the gas separation chamber. The separated mixed gas enters the flue gas tank. The remaining CO2 hydrate and residual seawater are separated.

[0022] Step 3: CO2 hydrates and residual seawater enter the secondary generation chamber. The residual seawater reacts with the CO2 microbubbles injected by the high-purity CO2 microbubble generator installed in the secondary generation chamber to generate high-purity hydrates and waste liquid.

[0023] Step 4: High-purity hydrates and waste liquid enter the liquid separation chamber to separate the waste liquid. The high-purity hydrates separated from the waste liquid enter the flue gas waste heat exchange decomposition chamber, where preliminary decomposition is performed using the waste heat of the flue gas. Afterward, the remaining hydrates enter the vacuum flash evaporation chamber, where rapid decomposition is achieved by depressurization. The steam jet pump is driven by the waste heat of the flue gas to maintain the vacuum in the vacuum flash evaporation chamber. The flash decomposition is completed instantaneously. Fresh water is collected in a water storage tank, and CO2 is collected in a CO2 gas tank.

[0024] Therefore, the present invention employs the above-mentioned multi-stage enhanced CO2 hydrate method for seawater desalination based on the cascade utilization of LNG cold energy, which has the following beneficial effects:

[0025] (1) By utilizing LNG cold energy in stages, the dual application of seawater pre-cooling and desalination and hydrate generation can be realized, thereby improving the efficiency of cold energy utilization.

[0026] (2) Microbubble enhanced generation technology is used to solve the traditional mass transfer limitation problem and improve the efficiency of hydrate generation and purification.

[0027] (3) By combining waste heat preheating with vacuum flash evaporation to decompose hydrates in stages, energy coupling and recovery can be achieved, reducing the overall energy consumption of the system.

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of an embodiment of a multi-stage enhanced CO2 hydrate method seawater desalination system and method based on the cascade utilization of LNG cold energy according to the present invention.

[0030] Figure Labels

[0031] 1. LNG storage tank; 2. First vaporization chamber; 3. Second vaporization chamber; 4. Spiral scrubber; 5. Primary generation chamber; 6. Secondary generation chamber; 7. Flue gas waste heat exchange decomposition chamber; 8. Vacuum flash chamber; 9. Steam jet pump; 10. Seawater tank; 11. Natural gas pipeline; 12. CO2 tank; 13. Flue gas tank; 14. Gas separation chamber; 15. Liquid separation chamber; 16. Water storage tank. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0034] Example 1

[0035] This invention provides a multi-stage enhanced CO2 hydrate seawater desalination system based on the cascade utilization of LNG cold energy, comprising the following modules:

[0036] Cold energy cascade module: Utilizes LNG cold energy to precool seawater for freezing and desalination, and provides cold energy to support hydrate formation;

[0037] Microbubble enhanced generation module: Improves gas mass transfer efficiency and generates high-purity CO2 hydrate through a two-stage generation chamber;

[0038] Waste heat-flash decomposition module: High-purity CO2 hydrate is preheated and decomposed by waste heat from flue gas, and then instantaneously decomposed by vacuum flash evaporation to obtain CO2 and fresh water;

[0039] Intelligent control module: Real-time dynamic adjustment of refrigerant distribution, microbubble flow rate, and flash chamber vacuum.

[0040] The cascaded cooling module includes an LNG storage tank 1, a first vaporization chamber 2, a second vaporization chamber 3, a dual refrigerant circuit, a spiral scrubber 4, and a seawater tank 10. The LNG storage tank 1 is connected to the first vaporization chamber 2, and a cryogenic pump and a rotary valve are installed between them to control and transport cryogenic LNG. The first vaporization chamber 2 is connected to the second vaporization chamber 3, and both are equipped with cryogenic pumps and rotary valves to control the transfer of LNG from the first vaporization chamber 2 to the second vaporization chamber 3. The second vaporization chamber 3 is connected to a natural gas pipeline 11, and a one-way valve is installed between it and the pipeline to prevent natural gas backflow. The spiral scrubber 4 is connected to the seawater tank 10, and a transfer pump and a one-way valve are installed between them to transport seawater to the scrubber and prevent backflow. The first vaporization chamber 2 and the second vaporization chamber 3 are each connected to the dual refrigerant circuit.

[0041] LNG storage tank 1 is used to store cryogenic LNG, providing a source of cold energy for the system. The first vaporization chamber 2 and the second vaporization chamber 3 are used to allow LNG to absorb heat and vaporize into a gaseous state, releasing cold energy. The cold energy provides a pre-cooling environment for the spiral scrubber 4 and the microbubble enhancement generation module through a dual refrigerant loop. The spiral scrubber 4 is used to separate ice crystals and high-salinity seawater, achieving preliminary desalination.

[0042] The microbubble enhancement generation module includes a primary generation chamber 5, a gas separation chamber 14, a secondary generation chamber 6, a liquid separation chamber 15, a flue gas microbubble generator, and a high-purity CO2 microbubble generator. The flue gas microbubble generator is located within the primary generation chamber 5. The primary generation chamber 5 is connected to both the spiral scrubber 4 and the gas separation chamber 14. A transfer pump and a check valve are installed between the primary generation chamber 5 and the spiral scrubber 4 to transfer the high-salinity seawater output from the spiral scrubber 4 and prevent backflow of the high-salinity seawater. A transfer pump and a butterfly valve are also installed between the primary generation chamber 5 and the gas separation chamber 14 to transfer the low-purity CO2 hydrate containing mixed gas generated in the primary generation chamber 5 to the gas separation chamber 14 and prevent backflow of the low-purity CO2 hydrate containing mixed gas. Gas separation chamber 14 is connected to secondary generation chamber 6. A transfer pump and butterfly valve are installed between gas separation chamber 14 and secondary generation chamber 6 to transfer the low-purity CO2 hydrate separated from the gas separation chamber 14 to secondary generation chamber 6 and prevent the low-purity CO2 hydrate from flowing back. A high-purity CO2 microbubble generator is located inside secondary generation chamber 6. Secondary generation chamber 6 is connected to liquid separation chamber 15. A transfer pump and butterfly valve are installed between secondary generation chamber 6 and liquid separation chamber 15 to transfer the high-purity CO2 hydrate and waste liquid from secondary generation chamber 6 to liquid separation chamber 15 and prevent the high-purity CO2 hydrate and waste liquid from flowing back.

[0043] The primary generation chamber 5 receives high-salinity seawater from the spiral scrubber 4 and mixes it with flue gas generated by the flue gas microbubble generator within the chamber to generate low-purity CO2 hydrate containing a mixed gas and residual seawater. The gas separation chamber 14 separates the mixed gas from the low-purity CO2 hydrate containing the mixed gas. The separated mixed gas enters the flue gas tank 13. The CO2 hydrate and residual seawater enter the secondary generation chamber 6, where the high-purity CO2 microbubble generator generates CO2 microbubbles from the CO2 tank 12 and mixes them with the residual seawater to generate high-purity CO2 hydrate and waste liquid. The liquid separation chamber 15 separates the waste liquid from the high-purity CO2 hydrate and waste liquid. The flue gas microbubble generator and the high-purity CO2 microbubble generator can be installed using existing equipment and parameters.

[0044] The flue gas microbubble generator uses a titanium alloy ultrasonic vibrating membrane with a pore size ≤50μm, which is resistant to salt corrosion and can accelerate the dissolution of CO2 and the formation of hydrates. The high-purity CO2 microbubble generator converts high-purity CO2 into microbubbles, which come into full contact with low-purity CO2 hydrates, purifying the hydrates through gas displacement. The flue gas microbubble generator can be directly replaced with a high-purity CO2 microbubble generator, directly dissolving high-purity CO2 in water in high-salinity seawater to generate high-purity CO2 hydrates.

[0045] The waste heat flash evaporation-decomposition module includes a flue gas waste heat exchange decomposition chamber 7, a vacuum flash chamber 8, a water storage tank 16, a steam jet pump 9, a flue gas tank 13, and a CO2 tank 12. The flue gas waste heat exchange decomposition chamber 7 is connected in series with the vacuum flash chamber 8. The vacuum flash chamber 8 is connected to both the steam jet pump 9 and the CO2 tank 12. A vacuum pump and a pressure reducing valve are installed between the vacuum flash chamber 8 and the CO2 tank 12 to draw the CO2 generated in the vacuum flash chamber 8 to the CO2 tank 12 for recovery and reuse, and to stabilize the pressure. The outlet end of the vacuum flash chamber 8 is connected to the water storage tank 16. A transfer pump and a check valve are installed between the vacuum flash chamber 8 and the water storage tank 16 to transfer the separated fresh water to the water storage tank 16 for collection and to prevent fresh water backflow.

[0046] The inlet of the flue gas waste heat exchange decomposition chamber 7 is connected to the liquid separation chamber 15. A transfer pump and a butterfly valve are provided between the flue gas waste heat exchange decomposition chamber 7 and the liquid separation chamber 15 to transport high-purity CO2 hydrate from the liquid separation chamber 15 to the flue gas waste heat exchange decomposition chamber 7. The CO2 tank 12 is connected to the secondary generation chamber 6. Two passages are provided between the CO2 tank 12 and the secondary generation chamber 6. Each passage is equipped with a suction pump and a one-way valve. The suction pump in one passage is used to draw CO2 from the CO2 tank 12 to the secondary generation chamber 6 and prevent CO2 backflow. The suction pump in the other passage is used to draw CO2 generated in the secondary generation chamber 6 to the CO2 tank and prevent CO2 backflow. The flue gas tank 13 is connected to the flue gas waste heat exchange decomposition chamber 7. A fan is installed between the flue gas tank 13 and the flue gas waste heat exchange decomposition chamber 7 to transport the flue gas in the flue gas tank 13 to the flue gas waste heat exchange decomposition chamber 7 for waste heat recovery. The flue gas waste heat exchange decomposition chamber 7 is connected to the primary generation chamber 5. A suction pump and a one-way valve are installed between the flue gas waste heat exchange decomposition chamber 7 and the primary generation chamber 5 to draw the flue gas with recovered waste heat into the primary generation chamber 5 to provide CO2 and prevent CO2 backflow.

[0047] The waste heat exchange decomposition chamber 7 utilizes industrial waste heat to heat high-purity hydrates, causing partial decomposition. This preheating decomposition reduces subsequent flash evaporation energy consumption and simultaneously enables the resource utilization of waste heat. The vacuum flash evaporation chamber 8 instantly decomposes the remaining high-purity hydrates into fresh water and CO2, achieving rapid decomposition and shortening reaction time. The steam jet pump 9, driven by waste heat, maintains the vacuum environment in the vacuum flash evaporation chamber 8, further reducing decomposition energy consumption. The CO2 tank 12 collects the CO2 generated during the process and provides high-purity CO2 to the secondary generation chamber 6. The flue gas tank 13 stores the flue gas and collects the separated mixed gas (containing CO2 and N2) during the process, then transports the flue gas to the waste heat exchange decomposition chamber 7 for waste heat recovery and reuse.

[0048] The aforementioned butterfly valves, rotary valves, check valves, fans, transfer pumps, cryogenic pumps, and vacuum pumps are all controlled by an intelligent control module, which can effectively control the opening and closing of each pipeline and the transport of fluids in each pipeline.

[0049] like Figure 1 As shown, the present invention also provides a multi-stage enhanced CO2 hydrate desalination method based on LNG cold energy cascade utilization. The method employs the aforementioned multi-stage enhanced CO2 hydrate desalination system based on LNG cold energy cascade utilization, and includes the following steps:

[0050] Step 1: The LNG in LNG storage tank 1 absorbs heat and vaporizes into a gaseous state in the first vaporization chamber 2 and the second vaporization chamber 3. During the vaporization process, cold energy is released. The cold energy is transferred to the environment of the spiral scrubber 4, the primary generation chamber 5 and the secondary generation chamber 6 through the dual refrigerant loop. The seawater is pre-cooled by the cold energy of LNG in the spiral scrubber 4. The water in the seawater condenses into ice crystals, and the salt remains in the liquid phase. The ice crystals are separated by the spiral scrubber 4 to obtain high-salt seawater.

[0051] Step 2: The flue gas enters the flue gas waste heat exchange decomposition chamber 7 to exchange heat with the hydrate to be decomposed. After heat exchange, the flue gas is pre-cooled by a refrigerant and enters the primary generation chamber 5. The high-salt seawater obtained in Step 1 is introduced into the primary generation chamber 5. The high-salt seawater reacts with the CO2 generated by the flue gas microbubble generator in the primary generation chamber 5 to generate low-concentration CO2 hydrate containing mixed gas. The low-concentration CO2 hydrate containing mixed gas enters the gas separation chamber 14. The mixed gas in the low-concentration CO2 hydrate containing mixed gas is separated in the gas separation chamber 14. The separated mixed gas enters the flue gas tank 13. The remaining CO2 hydrate and residual seawater are separated.

[0052] Step 3: CO2 hydrate and residual seawater enter the secondary generation chamber 6. The residual seawater reacts with the CO2 microbubbles injected by the high-purity CO2 microbubble generator installed in the secondary generation chamber 6 to generate high-purity hydrate and waste liquid.

[0053] Step 4: High-purity hydrates and waste liquid enter the liquid separation chamber 15 to separate the waste liquid. The high-purity hydrates separated from the waste liquid enter the flue gas waste heat exchange decomposition chamber 7. The flue gas waste heat exchange decomposition chamber 7 uses the waste heat of the flue gas for preliminary decomposition. Then, the remaining hydrates enter the vacuum flash evaporation chamber 8, where the pressure is reduced to rapidly decompose the hydrates. The steam jet pump 9 uses the waste heat of the flue gas to maintain the vacuum in the vacuum flash evaporation chamber 8. The flash decomposition is completed instantly. Fresh water enters the water storage tank 16 for collection, and CO2 enters the CO2 gas tank 12 for collection.

[0054] The pressure in the flue gas waste heat exchange decomposition chamber 7 is 0.1 MPa and the temperature is 50℃, while the pressure in the vacuum flash evaporation chamber 8 is 0.01 MPa.

[0055] Therefore, the present invention adopts the above-mentioned multi-stage enhanced CO2 hydrate method seawater desalination system and method based on the cascade utilization of LNG cold energy. Through the graded utilization of cold energy, enhanced mass transfer and energy coupling, the freshwater production is increased, energy consumption is reduced, and CO2 capture rate is increased, which is suitable for large-scale industrial applications.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A multi-stage enhanced CO2 hydrate seawater desalination system based on LNG cold energy cascade utilization, characterized in that: Includes the following modules: Cold energy cascade module: Utilizes LNG cold energy to precool seawater for freezing and desalination, and provides cold energy to support hydrate formation; The cold energy cascade module includes an LNG storage tank, a first vaporization chamber, a second vaporization chamber, a dual refrigerant circuit, a spiral scrubber, and a seawater tank. The LNG storage tank is connected to the first vaporization chamber, the first vaporization chamber is connected to the second vaporization chamber, the second vaporization chamber is connected to a natural gas pipeline, the spiral scrubber is connected to the seawater tank, and the first and second vaporization chambers are respectively connected to the dual refrigerant circuit. In the LNG storage tank, LNG absorbs heat and vaporizes into a gaseous state in the first and second vaporization chambers. During the vaporization process, cold energy is released. The cold energy is transferred to the environment of the spiral scrubber, the primary generation chamber and the secondary generation chamber through a dual refrigerant loop. Seawater is pre-cooled by the cold energy of LNG in the spiral scrubber. The water in the seawater condenses into ice crystals, and the salt remains in the liquid phase. The ice crystals are separated by the spiral scrubber to obtain high-salt seawater. Microbubble enhanced generation module: Improves gas mass transfer efficiency and generates high-purity CO2 hydrate through a cascade of primary and secondary generation chambers; The primary generation chamber is connected to the spiral washer; Waste heat-flash decomposition module: High-purity CO2 hydrate is preheated and decomposed by waste heat from flue gas, and then instantaneously decomposed by vacuum flash evaporation to obtain CO2 and fresh water. Vacuum during vacuum flash evaporation is maintained by a steam jet pump, which is driven by waste heat from flue gas.

2. The multi-stage enhanced CO2 hydrate seawater desalination system based on LNG cold energy cascade utilization as described in claim 1, characterized in that: The system also includes the following modules: Intelligent control module: Real-time dynamic adjustment of refrigerant distribution, microbubble flow rate, and flash chamber vacuum.

3. A multi-stage enhanced CO2 hydrate seawater desalination system based on LNG cold energy cascade utilization as described in claim 2, characterized in that: The microbubble enhancement generation module includes a primary generation chamber, a gas separation chamber, a secondary generation chamber, a liquid separation chamber, a flue gas microbubble generator, and a high-purity CO2 microbubble generator. The flue gas microbubble generator is located in the primary generation chamber, and the high-purity CO2 microbubble generator is located in the secondary generation chamber. The primary generation chamber is connected to the gas separation chamber, the gas separation chamber is connected to the secondary generation chamber, and the secondary generation chamber is connected to the liquid separation chamber.

4. A multi-stage enhanced CO2 hydrate seawater desalination system based on LNG cold energy cascade utilization as described in claim 3, characterized in that: The waste heat flash decomposition module includes a flue gas waste heat exchange decomposition chamber, a vacuum flash chamber, a water storage tank, a steam jet pump, a flue gas tank, and a CO2 tank. The flue gas waste heat exchange decomposition chamber is connected in series with the vacuum flash chamber. The vacuum flash chamber is connected to the steam jet pump and the CO2 tank respectively. The outlet end of the vacuum flash chamber is connected to the water storage tank.

5. A multi-stage enhanced CO2 hydrate seawater desalination system based on LNG cold energy cascade utilization as described in claim 4, characterized in that: The inlet of the flue gas waste heat exchange decomposition chamber is connected to the liquid separation chamber, the CO2 gas tank is connected to the secondary generation chamber, the flue gas tank is connected to the flue gas waste heat exchange decomposition chamber, and the flue gas waste heat exchange decomposition chamber is connected to the primary generation chamber.

6. A multi-stage enhanced CO2 hydrate method for seawater desalination based on the cascade utilization of LNG cold energy, characterized in that: The multi-stage enhanced CO2 hydrate method seawater desalination system based on LNG cold energy cascade utilization, as described in claim 5, includes the following steps: Step 1: In the LNG storage tank, the LNG absorbs heat and vaporizes into a gaseous state in the first and second vaporization chambers. During the vaporization process, cold energy is released and transferred to the environment of the spiral scrubber, the primary generation chamber and the secondary generation chamber through a dual refrigerant loop. The seawater is pre-cooled by the cold energy of LNG in the spiral scrubber, and the water in the seawater condenses into ice crystals. The salt remains in the liquid phase. The ice crystals are separated by the spiral scrubber to obtain high-salt seawater. Step 2: The flue gas enters the flue gas waste heat exchange decomposition chamber to exchange heat with the hydrate to be decomposed. After heat exchange, the flue gas is pre-cooled by a refrigerant and enters the primary generation chamber. The high-salt seawater obtained in Step 1 is introduced into the primary generation chamber. The high-salt seawater reacts with CO2 generated by the flue gas microbubble generator in the primary generation chamber to generate low-concentration CO2 hydrate containing mixed gas. The low-concentration CO2 hydrate containing mixed gas enters the gas separation chamber. The mixed gas in the low-concentration CO2 hydrate containing mixed gas is separated in the gas separation chamber. The separated mixed gas enters the flue gas tank. The remaining CO2 hydrate and residual seawater are separated. Step 3: CO2 hydrates and residual seawater enter the secondary generation chamber. The residual seawater reacts with the CO2 microbubbles injected by the high-purity CO2 microbubble generator installed in the secondary generation chamber to generate high-purity hydrates and waste liquid. Step 4: High-purity hydrates and waste liquid enter the liquid separation chamber to separate the waste liquid. The high-purity hydrates separated from the waste liquid enter the flue gas waste heat exchange decomposition chamber, where preliminary decomposition is performed using the waste heat of the flue gas. Afterward, the remaining hydrates enter the vacuum flash evaporation chamber, where rapid decomposition is achieved by depressurization. The steam jet pump is driven by the waste heat of the flue gas to maintain the vacuum in the vacuum flash evaporation chamber. The flash decomposition is completed instantaneously. Fresh water is collected in a water storage tank, and CO2 is collected in a CO2 gas tank.

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