Multi-stage enhanced CO2 hydrate method seawater desalination system and method based on LNG (Liquefied Natural Gas) cold energy gradient utilization

Abstract

The invention discloses a multistage enhanced CO2 hydrate method sea water desalination system and method based on LNG cold energy gradient utilization, and belongs to the technical field of sea water desalination, the system comprises the following modules: a cold energy gradient module, which uses LNG cold energy to precool sea water for freezing desalination, and provides cold energy for hydrate generation; the micro-bubble enhanced generation module is used for improving the gas mass transfer efficiency and generating high-purity CO2 hydrate in a stepped manner through two stages of generation chambers; according to the waste heat-flash evaporation decomposition module, the high-purity CO2 hydrate is preheated and decomposed through flue gas waste heat, and then CO2 and fresh water are obtained through instant decomposition through vacuum flash evaporation. According to the multistage enhanced CO2 hydrate method seawater desalination system and method based on LNG cold energy gradient utilization, through cold energy graded utilization, mass transfer enhancement and energy coupling, the fresh water yield is increased, energy consumption is reduced, the CO2 capture rate is increased, and the system and method are suitable for large-scale industrial application.

Description

Technical Field

[0001] The present invention relates to the technical field of seawater desalination, 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 Art

[0002] Desalination is an important approach to addressing global water shortages. Hydrate desalination technology has become a research hotspot because it can be combined with CO2-rich industrial waste gas to achieve the dual goals of "desalination + carbon capture." This technology separates water molecules from salt in seawater by forming cage-type hydrates (CO2·nH2O) with CO2, and then decomposes the hydrates to produce fresh water. However, traditional hydrate desalination technology faces three core bottlenecks in industrial application:

[0003] 1) Low cold energy utilization efficiency: LNG cold energy is only used for hydrate formation, and the ultra-low temperature potential is not fully released;

[0004] 2) Mass transfer limitation: The CO2 dissolution rate is slow when generating hydrates by the traditional bubbling method, resulting in a large generation chamber volume;

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

[0006] Although patent number CN106629903B proposes a two-stage generation chamber and a refrigerant cycle, 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 the present 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 graded utilization of cold energy, mass transfer enhancement and energy coupling, the fresh water production is increased, the energy consumption is reduced, and the CO2 capture rate is increased, which is suitable for large-scale industrial applications.

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

[0009] Cold energy cascade module: uses LNG cold energy to pre-cool seawater for freezing and desalination, and provides cold energy for hydrate formation;

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

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

[0012] Preferably, the system further comprises the following modules:

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

[0014] Preferably, the cold energy cascade module comprises an LNG storage tank, a first gasification chamber, a second gasification chamber, a double refrigerant circuit, a spiral scrubber and a seawater tank, wherein the LNG storage tank is connected to the first gasification chamber, the first gasification chamber is connected to the second gasification chamber, the second gasification chamber is connected to a natural gas pipeline, the spiral scrubber is connected to the seawater tank, and the first gasification chamber and the second gasification chamber are respectively connected to the double refrigerant circuit.

[0015] Preferably, the microbubble reinforced generation module comprises 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, wherein the flue gas microbubble generator is arranged in the primary generation chamber, the high-purity CO2 microbubble generator is arranged 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 scrubber.

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

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

[0019] The application also provides a multi-stage reinforced CO2 hydrate method for seawater desalination based on LNG cold energy cascade utilization, which adopts the multi-stage reinforced CO2 hydrate method for seawater desalination based on LNG cold energy cascade utilization system.

[0020] Step one, the LNG in the LNG storage tank is gasified into a gaseous state by absorbing heat in the first gasification chamber and the second gasification chamber, and releases cold energy in the gasification process, which is transmitted to the spiral scrubber, the primary generation chamber and the secondary generation chamber through the double refrigerant circuit, the seawater is pre-cooled by the LNG cold energy 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, and high-salt seawater is obtained.

[0021] Step two, the flue gas enters the flue gas waste heat heat exchange type decomposition chamber and exchanges heat with the hydrate to be endothermically decomposed, and after heat exchange, the flue gas is pre-cooled by the refrigerant and enters the primary generation chamber, the high-salt seawater obtained in step one is introduced into the primary generation chamber, the high-salt seawater reacts with CO2 generated by the CO2 micro-bubble 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 out in the gas separation chamber, the separated mixed gas enters the flue gas tank, and the remaining CO2 hydrate and residual seawater;

[0022] Step three, the CO2 hydrate and residual seawater enter the secondary generation chamber, the residual seawater reacts with the CO2 micro-bubbles injected by the high-purity CO2 micro-bubble generator arranged in the secondary generation chamber to generate high-purity hydrate and waste liquid;

[0023] Step four, the high-purity hydrate and waste liquid enter the liquid separation chamber to separate out the waste liquid, the high-purity hydrate separated out from the waste liquid enters the flue gas waste heat heat exchange type decomposition chamber, the flue gas waste heat heat exchange type decomposition chamber utilizes flue gas waste heat for preliminary decomposition, and then the remaining hydrate enters the vacuum flash chamber to rapidly decompose the hydrate by decompression, the steam jet pump is driven by flue gas waste heat to maintain the vacuum of the vacuum flash chamber, the flash decomposition is completed instantaneously, the fresh water enters the water storage tank for collection, and the CO2 enters the CO2 tank for collection.

[0024] Therefore, the application adopts the above-mentioned multi-stage enhanced CO2 hydrate method seawater desalination system and method based on LNG cold energy cascade utilization, which has the following beneficial effects:

[0025] (1) By utilizing the LNG cold energy cascade, the dual cold energy application of seawater pre-cooling desalination and hydrate generation is realized, and the cold energy utilization efficiency is improved;

[0026] (2) The micro-bubble enhanced generation technology is adopted to solve the traditional mass transfer limitation problem and improve the hydrate generation and purification efficiency;

[0027] (3) The residual heat preheating and vacuum flash decomposition are combined to decompose the hydrate in stages, energy coupling recovery is realized, and the overall energy consumption of the system is reduced.

[0028] The technical solutions of the application will be further described in detail below through the drawings and examples. DESCRIPTION OF DRAWINGS

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

[0030] REFERENCE NUMERALS

[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 DESCRIPTION

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

[0033] Unless otherwise defined, the technical or scientific terms used in the present invention shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0034] Example 1

[0035] 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:

[0036] Cold energy cascade module: uses LNG cold energy to pre-cool seawater for freezing and desalination, and provides cold energy for hydrate formation;

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

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

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

[0040] The cold energy cascade module includes an LNG storage tank 1, a first vaporizer 2, a second vaporizer 3, a dual refrigerant circuit, a spiral scrubber 4, and a seawater tank 10. The LNG storage tank 1 is connected to the first vaporizer 2. A cryogenic pump and rotary valve are located between the two chambers for controlling and delivering cryogenic LNG. The first vaporizer 2 is connected to the second vaporizer 3. Both chambers are equipped with cryogenic pumps and rotary valves for controlling the delivery of LNG from the first vaporizer 2 to the second vaporizer 3. The second vaporizer 3 is connected to a natural gas pipeline 11. A check valve is located between the two chambers to prevent natural gas backflow. The spiral scrubber 4 is connected to the seawater tank 10. A transfer pump and a check valve are located between the two chambers to deliver seawater to the scrubber and prevent backflow. The first vaporizer 2 and second vaporizer 3 are each connected to the dual refrigerant circuit.

[0041] LNG storage tank 1 stores cryogenic LNG, providing a cold energy source for the system. The first and second vaporizers 2 and 3 absorb heat and vaporize the LNG into a gaseous state, releasing cold energy. This cold energy, via a dual refrigerant circuit, provides a pre-cooling environment for the spiral scrubber 4 and the microbubble enhancement generation module. The spiral scrubber 4 separates ice crystals from high-salinity seawater, achieving initial 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, which is connected to the spiral scrubber 4 and the gas separation chamber 14, respectively. A delivery pump and a one-way valve are installed between the primary generation chamber 5 and the spiral scrubber 4 to transport the high-salinity seawater output from the spiral scrubber 4 and prevent its backflow. A delivery pump and a butterfly valve are installed between the primary generation chamber 5 and the gas separation chamber 14 to transport the low-purity CO2 hydrate containing the mixed gas generated in the primary generation chamber 5 to the gas separation chamber 14 and prevent its backflow. The gas separation chamber 14 is connected to the secondary generation chamber 6. A delivery pump and a butterfly valve are installed between the two chambers to transport the low-purity CO2 hydrate separated from the mixed gas in the gas separation chamber 14 to the secondary generation chamber 6 and prevent the low-purity CO2 hydrate from flowing back. A high-purity CO2 microbubble generator is installed in the secondary generation chamber 6. The secondary generation chamber 6 is connected to the liquid separation chamber 15. A delivery pump and a butterfly valve are installed between the two chambers to transport the high-purity CO2 hydrate and waste liquid from the secondary generation chamber 6 to the liquid separation chamber 15 and prevent the high-purity CO2 hydrate and waste liquid from flowing back.

[0043] The primary generation chamber 5 is used to receive the high-salt seawater output by the spiral washer 4, and to make the high-salt seawater generate low-purity CO2 hydrate containing mixed gas and residual seawater with the flue gas micro-bubble generator arranged in the primary generation chamber 5. The gas separation chamber 14 is used to separate the mixed gas in the low-purity CO2 hydrate containing mixed gas, and the separated mixed gas enters the flue gas tank 13, and the CO2 hydrate and residual seawater enter the secondary generation chamber 6. The high-purity CO2 micro-bubble generator in the secondary generation chamber 6 generates CO2 micro-bubbles from the CO2 tank 12 and generates high-purity CO2 hydrate and waste liquid with the residual seawater. The liquid separation chamber 15 is used to separate the waste liquid in the high-purity CO2 hydrate and waste liquid. The flue gas micro-bubble generator and the high-purity CO2 micro-bubble generator can be arranged by using the equipment in the prior art, and arranged by using the parameters in the prior art.

[0044] The flue gas micro-bubble generator uses a titanium alloy ultrasonic vibration membrane with a pore size of ≤50 μm, is resistant to salt corrosion, and can accelerate the dissolution of CO2 and the generation of hydrate. The high-purity CO2 micro-bubble generator converts high-purity CO2 into micro-bubbles, fully contacts the low-purity CO2 hydrate, and purifies the hydrate by gas replacement. The flue gas micro-bubble generator can be directly replaced by the high-purity CO2 micro-bubble generator to directly dissolve high-purity CO2 in the water in the high-salt seawater to generate high-purity CO2 hydrate.

[0045] The waste heat flash-decomposition module includes a flue gas waste heat exchange type 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 type decomposition chamber 7 is connected in series with the vacuum flash chamber 8. The vacuum flash chamber 8 is connected with the steam jet pump 9 and the CO2 tank 12, respectively. An exhaust pump and a pressure reducing valve are arranged between the vacuum flash chamber 8 and the CO2 tank 12, and are used to exhaust the CO2 generated in the vacuum flash chamber 8 to the CO2 tank 12 for recycling and pressure stabilization. The outlet end of the vacuum flash chamber 8 is connected with the water storage tank 16. A delivery pump and a one-way valve are arranged between the vacuum flash chamber 8 and the water storage tank 16, and are used to deliver the separated fresh water to the water storage tank 16 for collection, and to prevent backflow of the fresh water.

[0046] The inlet end of the flue gas waste heat exchange decomposition chamber 7 is connected to the liquid separation chamber 15. A delivery pump and a butterfly valve are provided between the flue gas waste heat exchange decomposition chamber 7 and the liquid separation chamber 15 to deliver the high-purity CO2 hydrate in the liquid separation chamber 15 to the flue gas waste heat exchange decomposition chamber 7. The CO2 gas tank 12 is connected to the secondary generation chamber 6. Two passages are provided between the CO2 gas tank 12 and the secondary generation chamber 6. Each passage is provided with an exhaust pump and a one-way valve. The exhaust pump on one passage is used to extract the CO2 in the CO2 gas tank 12 into the secondary generation chamber 6 and prevent the CO2 from flowing back. The exhaust pump on the other passage is used to extract the CO2 generated in the secondary generation chamber 6 into the CO2 gas tank and prevent the CO2 from flowing back. The flue gas tank 13 is connected to the flue gas waste heat exchange decomposition chamber 7. A fan is provided 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. An exhaust pump and a one-way valve are provided between the flue gas waste heat exchange decomposition chamber 7 and the primary generation chamber 5 to extract the flue gas with recovered waste heat into the primary generation chamber 5 to provide CO2 and prevent CO2 backflow.

[0047] The flue gas waste heat heat exchange decomposition chamber 7 is used to utilize the waste heat of industrial flue gas to heat the high-purity hydrates to partially decompose them. Through preheating decomposition, the energy consumption of subsequent flash evaporation is reduced, and at the same time, the resource utilization of flue gas waste heat is realized. The vacuum flash chamber 8 is used to instantly decompose the remaining high-purity hydrates into fresh water and CO2, achieving rapid decomposition and shortening the reaction time. The steam jet pump 9 is driven by the waste heat of flue gas to maintain the vacuum environment of the vacuum flash chamber 8 and reduce the energy consumption of decomposition. The CO2 gas tank 12 is used to collect the CO2 generated in the process and provide high-purity CO2 to the secondary generation chamber 6. The flue gas tank 13 is used to store flue gas and collect the mixed gas (containing CO2 and N2) separated in the process and transport the flue gas to the flue gas waste heat heat exchange decomposition chamber 7 to recover and reuse the flue gas waste heat.

[0048] The above-mentioned butterfly valves, rotary valves, one-way valves, fans, delivery 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 delivery of fluids in each pipeline.

[0049] like Figure 1 As shown, the present invention also provides a multi-stage enhanced CO2 hydrate method for seawater desalination based on the cascade utilization of LNG cold energy, which uses the above-mentioned multi-stage enhanced CO2 hydrate method for seawater desalination based on the cascade utilization of LNG cold energy, including the following steps:

[0050] Step 1: The LNG in the LNG storage tank 1 absorbs heat and vaporizes into a gaseous state in the first vaporization chamber 2 and the second vaporization chamber 3. Cold energy is released during the vaporization process. The cold energy is transferred to the environment of the spiral scrubber 4, the first generation chamber 5, and the second generation chamber 6 through a dual refrigerant circuit. The seawater is pre-cooled by the LNG cold energy 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-salinity 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 by endothermic decomposition. After the 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 passed 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 a mixed gas. The low-concentration CO2 hydrate containing a mixed gas enters the gas separation chamber 14. The mixed gas in the low-concentration CO2 hydrate containing a mixed gas is separated in the gas separation chamber 14. The separated mixed gas enters the flue gas tank 13, and the remaining CO2 hydrate and residual seawater are left.

[0052] Step 3: The CO2 hydrate and residual seawater enter the secondary generation chamber 6, where the residual seawater reacts with the CO2 microbubbles injected by the high-purity CO2 microbubble generator provided 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, and 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 flue gas waste heat to perform preliminary decomposition. Then, the remaining hydrates enter the vacuum flash chamber 8 and are rapidly decomposed by reducing the pressure. The steam jet pump 9 is driven by the flue gas waste heat to maintain the vacuum of the vacuum flash chamber 8. The flash decomposition is completed instantly, and the fresh water enters the water storage tank 16 for collection, and the 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° C., and the pressure in the vacuum flash 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, mass transfer enhancement and energy coupling, the fresh water production is increased, the energy consumption is reduced, and the 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 rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements 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 desalination system based on cascaded utilization of LNG cold energy, characterized by: Includes the following modules: Cold energy cascade module: uses LNG cold energy to pre-cool seawater for freezing and desalination, and provides cold energy for hydrate formation; Microbubble enhanced generation module: improves gas mass transfer efficiency and generates high-purity CO2 hydrate through a two-stage generation chamber cascade; Waste heat-flash decomposition module: High-purity CO2 hydrate is preheated and decomposed by flue gas waste heat, and then decomposed instantly by vacuum flash evaporation to produce CO2 and fresh water.

2. The multi-stage enhanced CO2 hydrate desalination system based on cascaded utilization of LNG cold energy according to claim 1 is characterized by: The system also includes the following modules: Intelligent control module: Real-time dynamic adjustment of refrigerant distribution, microbubble flow and flash chamber vacuum degree.

3. The multi-stage enhanced CO2 hydrate desalination system based on cascaded utilization of LNG cold energy according to claim 1 is characterized by: 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, wherein 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 vaporization chamber and the second vaporization chamber are respectively connected to the dual refrigerant circuit.

4. The multi-stage enhanced CO2 hydrate desalination system based on cascaded utilization of LNG cold energy according to claim 3 is characterized by: The microbubble enhanced 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 arranged in the primary generation chamber, and the high-purity CO2 microbubble generator is arranged 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.

5. The multi-stage enhanced CO2 hydrate desalination system based on cascaded utilization of LNG cold energy according to claim 4 is characterized in that: The first-stage generating chamber is connected to the spiral scrubber.

6. The multi-stage enhanced CO2 hydrate desalination system based on cascaded utilization of LNG cold energy according to claim 4 is characterized in that: The waste heat flash evaporation-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, and 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.

7. The multi-stage enhanced CO2 hydrate desalination system based on cascaded utilization of LNG cold energy according to claim 6, characterized in that: 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.

8. A multi-stage enhanced CO2 hydrate desalination method based on the cascaded utilization of LNG cold energy, characterized by: A multi-stage enhanced CO2 hydrate seawater desalination system based on cascaded utilization of LNG cold energy as described in any one of claims 1 to 7 comprises the following steps: Step 1: LNG in the LNG storage tank absorbs heat and vaporizes into gas in the first and second vaporization chambers. Cold energy is released during the vaporization process, and the cold energy is transferred to the environment of the spiral scrubber, the first generation chamber, and the second generation chamber through a dual refrigerant circuit. Seawater is pre-cooled by the LNG cold energy in the spiral scrubber, and the water in the seawater condenses into ice crystals, while the salt remains in the liquid phase. The ice crystals are separated by the spiral scrubber to obtain high-salinity seawater; Step 2: The flue gas enters a flue gas waste heat exchange decomposition chamber to exchange heat with the hydrate to be decomposed by endothermic decomposition. After the heat exchange, the flue gas is pre-cooled by a refrigerant and enters a primary generation chamber. The high-salt seawater obtained in step 1 is introduced into the primary generation chamber. The high-salt seawater reacts with the CO2 generated by the flue gas microbubble generator in the primary generation chamber to generate a low-concentration CO2 hydrate containing a mixed gas. The low-concentration CO2 hydrate containing a mixed gas enters a gas separation chamber. The mixed gas in the low-concentration CO2 hydrate containing a mixed gas is separated in the gas separation chamber. The separated mixed gas enters a flue gas tank, and the remaining CO2 hydrate and residual seawater are left. Step 3: CO2 hydrate and residual seawater enter the secondary generation chamber, and the residual seawater reacts with CO2 microbubbles injected by the high-purity CO2 microbubble generator set in the secondary generation chamber to generate high-purity hydrate and waste liquid; Step 4: High-purity hydrates and waste liquid enter the liquid separation chamber to separate the waste liquid, and the high-purity hydrates separated from the waste liquid enter the flue gas waste heat exchange decomposition chamber. The flue gas waste heat exchange decomposition chamber uses the flue gas waste heat to perform preliminary decomposition. After that, the remaining hydrates enter the vacuum flash chamber and are quickly decomposed by reducing the pressure. The steam jet pump is driven by the flue gas waste heat to maintain the vacuum in the vacuum flash chamber. The flash decomposition is completed instantly, and the fresh water enters the water storage tank for collection, and the CO2 enters the CO2 gas tank for collection.

Images