Seawater freezing desalination device, method and system based on multiphase flow regulation

Abstract

The present application relates to the technical field of seawater freezing desalination, and particularly relates to a seawater freezing desalination device based on multiphase flow regulation, a desalination method and a desalination system. The seawater freezing desalination device comprises a gas-liquid mixing box, a metal rotating drum and a gas injection part. The gas-liquid mixing box comprises an arc-shaped bottom disc and symmetrical side plates arranged on both sides of the arc-shaped bottom disc. One side edge of the top of the arc-shaped bottom disc is provided with a seawater inlet, and the other side edge of the top is provided with a seawater outlet. A gas injection chamber is arranged in the lower part of the arc-shaped bottom disc. A plurality of waterproof gas injection nozzles are arranged on the inner arc-shaped surface of the arc-shaped bottom disc. The arc-shaped bottom disc and the side plates on both sides form a seawater freezing crystallization cavity. The metal rotating drum is in a cylindrical drum shape, and low-temperature refrigerant is arranged in the drum. The lower part of the metal rotating drum is arranged in the seawater freezing crystallization cavity. The gas injection part is connected with the bottom of the arc-shaped bottom disc. The seawater freezing desalination device realizes efficient seawater freezing desalination.

Description

Technical Field

[0001] This invention relates to the field of seawater cryogenic desalination technology, and in particular to a seawater cryogenic desalination device, desalination method and desalination system based on multiphase flow control. Background Technology

[0002] With the advancement of industrialization and population growth, the world is facing a severe shortage of freshwater resources. A United Nations report predicts that by 2025, 1.4 billion people worldwide will face the threat of freshwater scarcity. Seawater desalination, as a crucial means of obtaining freshwater resources, is receiving increasing attention from various countries.

[0003] Currently, commercially available seawater desalination technologies mainly include multi-effect evaporation, reverse osmosis, and electrodialysis. Multi-effect evaporation improves seawater concentration efficiency through multi-stage evaporation, followed by condensation to obtain freshwater. This method produces high-quality freshwater, but it consumes a large amount of heat and has high operating costs. Reverse osmosis uses high pressure to force seawater through a semi-permeable membrane, blocking salt to obtain freshwater. This method consumes a significant amount of electricity, and the membrane is prone to clogging. Electrodialysis uses an electric field to remove ionic salts from seawater, but the process is complex and consumes extremely large amounts of electricity. Overall, existing mainstream commercial seawater desalination technologies have high equipment investment and operating costs, making large-scale promotion and application difficult.

[0004] In contrast, seawater cryo-desalination technology shows great application potential due to its low equipment investment and low operating costs. The technology's principle is simple: seawater is frozen into ice. Since water crystallizes before salt, desalinated ice crystals are obtained, which can then be melted to produce fresh water. However, the low freezing crystallization efficiency in current seawater cryo-desalination technology severely restricts its development and application.

[0005] Specifically, seawater cryo-desalination technology has two significant drawbacks: first, the slow ice crystal growth rate greatly prolongs the freezing time and process; second, the anisotropic crystallization process during ice crystal growth leads to the formation of salt cells, affecting the desalination rate of the freshwater after melting. How to improve the ice crystal formation rate and quality during seawater cryo-desalination is the core scientific challenge facing this technology. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned defects in the prior art and to propose a seawater cryogenic desalination device, method and system based on multiphase flow control, which achieves efficient seawater cryogenic desalination.

[0007] The technical solution of this invention is: a seawater cryogenic desalination device based on multiphase flow control, comprising:

[0008] The gas-liquid mixing chamber includes an arc-shaped chassis and symmetrically arranged side plates on both sides of the arc-shaped chassis. A seawater inlet is provided on one side of the top of the arc-shaped chassis, and a seawater outlet is provided on the corresponding top side of the other side. A jet chamber is provided in the lower part of the arc-shaped chassis, and several waterproof jet nozzles are provided on the arc-shaped inner surface of the arc-shaped chassis. The arc-shaped chassis and the two side plates together form a seawater freezing and crystallization chamber.

[0009] The metal rotating cylinder is cylindrical in shape and contains a low-temperature refrigerant. The lower part of the metal rotating cylinder is placed inside the seawater freezing and crystallization chamber.

[0010] The gas injection section is connected to the bottom of the arc-shaped chassis.

[0011] In this invention, the gas injection unit includes a gas storage tank, which is connected to the bottom of the arc-shaped chassis via an air intake pipe. An air pump and a control valve are provided on the air intake pipe, and the gas in the gas storage tank flows into the jet chamber through the air intake pipe.

[0012] The arc-shaped chassis is semi-cylindrical, with several seawater inlets and outlets symmetrically arranged on both sides of the top of the arc-shaped chassis. The seawater inlets and outlets are spaced apart along the axial direction of the arc-shaped chassis.

[0013] The present invention also includes a method for seawater cryo-desalination using the above-mentioned seawater cryo-desalination device based on multiphase flow control, comprising the following steps:

[0014] Seawater flows into the seawater freezing and crystallization chamber through the seawater inlet. At the same time, non-condensable gas in the gas storage tank enters the jet chamber through the air intake pipe. Non-condensable gas in the jet chamber enters the seawater freezing and crystallization chamber in the form of bubbles through the waterproof jet nozzle and mixes with the seawater.

[0015] The lower part of the metal rotating cylinder is immersed in seawater in the seawater freezing and crystallization chamber. The low-temperature refrigerant inside the cylinder causes the fresh seawater mixed with non-condensable gases to gradually crystallize on the outer surface of the metal rotating cylinder.

[0016] The ice layer on the outer surface of the metal drum is scraped off to achieve freshwater recycling.

[0017] During the ice crystal production process, the disturbance of non-condensable gases makes ice crystals grow faster and inhibits salinity during the crystallization process.

[0018] Concentrated seawater without crystallization flows out from the seawater outlet.

[0019] The present invention also discloses a seawater desalination system including the above-mentioned seawater desalination device based on multiphase flow control, wherein the system further includes: a refrigeration compressor, an auxiliary condenser, a main condenser, a throttling valve, a scraper, and a seawater precooling device;

[0020] The refrigeration compressor, auxiliary condenser, main condenser, expansion valve, and metal drum are connected in sequence to form the refrigeration cycle section.

[0021] After the refrigeration compressor cools the refrigerant, the refrigerant passes through the auxiliary condenser, the main condenser, and the expansion valve in sequence, and finally flows into the metal drum. The refrigerant in the metal drum exchanges heat with the seawater and then flows back into the refrigeration compressor, thus realizing the refrigerant cycle.

[0022] The ice layer scraped off the outer surface of the metal drum by a scraper falls directly into the main condenser, where heat exchange occurs between the refrigerant and the ice layer.

[0023] Ice enters the seawater precooling device from the main condenser. Concentrated seawater flowing out of the seawater desalination device enters the precooling device. After the desalinated seawater passes through the seawater precooling device, it enters the seawater desalination device.

[0024] Inside the seawater precooling device, heat exchange is achieved between the ice layer and the seawater to be desalinated, as well as between the concentrated seawater and the seawater to be desalinated, so that the seawater to be desalinated entering the seawater cryogenic desalination device is low-temperature seawater.

[0025] Related research indicates that adding appropriate exogenous substances during the freezing process can improve the growth rate and crystallization quality of ice crystals through perturbation. This provides a new approach to solving the problem of low crystallization efficiency in seawater cryopreservation. In particular, utilizing the perturbation effect of non-condensable gases can suppress salt content in ice crystals while ensuring the ice crystal growth rate, thereby achieving high-speed desalination cryopreservation crystallization. Furthermore, non-condensable gases are low-cost, non-polluting, and have no impact on the quality of the thawed freshwater. Developing efficient seawater cryopreservation technology utilizing the perturbation effect of non-condensable gases will greatly enhance the applicability and application prospects of this technology.

[0026] The beneficial effects of this invention are:

[0027] This application utilizes non-condensable gases to disturb seawater and freeze it to crystallize, thereby achieving seawater desalination during the freezing and crystallization process. This application effectively solves the technical pain points of slow crystallization rate and poor desalination effect in existing seawater freeze-desalination processes. It can not only significantly improve the growth rate of ice crystals during freezing, but also further reduce the salinity in the ice crystals, achieving efficient and energy-saving seawater freeze-desalination. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the KKS model;

[0029] Figure 2(a) shows the ice crystal morphology when the bubble incident velocity is 0.1 m / s;

[0030] Figure 2(b) shows the ice crystal morphology when the bubble incident velocity is 0.25 m / s;

[0031] Figure 2(c) shows the ice crystal morphology when the bubble incident velocity is 0.5 m / s;

[0032] Figure 3(a) is a line graph of salt cell area under different bubble injection velocities;

[0033] Figure 3(b) is a line graph of salt cell area under different bubble incident angles;

[0034] Figure 4 This is a schematic diagram of the main structure of a seawater cryogenic desalination device;

[0035] Figure 5 This is a top view of a seawater cryogenic desalination unit.

[0036] Figure 6 This is a cross-sectional schematic diagram of a seawater cryogenic desalination unit;

[0037] Figure 7 This is a three-dimensional structural diagram of a seawater cryogenic desalination device;

[0038] Figure 8 This is a schematic diagram of the connection structure of a seawater cryogenic desalination system.

[0039] In the diagram: 1. Gas storage tank; 2. Air pump; 3. Control valve; 4. Inlet pipe; 5. Gas-liquid mixing box; 6. Metal drum; 7. Waterproof jet nozzle; 8. Seawater inlet; 9. Seawater outlet; 10. Jet chamber; 11. Seawater freezing and crystallization chamber; 12. Side plate; 13. Arc-shaped chassis; 14. Seawater cleaner; 15. Scraper; 16. Main condenser; 17. Throttling valve; 18. Auxiliary condenser; 19. Refrigeration compressor; 20. Seawater precooling device; 21. Subcooled wall cylinder; 22. Bubble; 23. Seawater. Detailed Implementation

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0041] Specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many ways other than those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0042] The seawater desalination device based on multiphase flow control described in this application achieves high-speed desalination and freezing crystallization of seawater by utilizing the disturbance effect of non-condensable gases. Therefore, in this embodiment, the principle of the disturbance effect of non-condensable gases is first explained in detail.

[0043] Based on the KKS model, the anisotropic crystallization behavior of seawater on a supercooled metal cylinder wall at the mesoscale was modeled to explore the crystallization mechanism under different bubble incident velocities and angles. The main method of this experiment was to add incident bubbles to the original single-phase seawater freezing and crystallization process, and to control the seawater flow field using the flow characteristics of two-phase flow, such as... Figure 1 As shown.

[0044] Figures 2(a) to 2(c) The images show the morphology of ice crystals after seawater freezes under the disturbance of non-condensable gases. The red areas represent ice, the yellow areas represent bubbles, the areas within the dashed squares represent salt cell regions, and the closed circles within the dashed squares represent salt cells. The bubble velocity in Figure 2(a) is 0.1 m / s, the bubble velocity in Figure 2(b) is 0.25 m / s, and the bubble velocity in Figure 2(c) is 0.5 m / s.

[0045] according to Figures 2(a) to 2(c) As shown in Figure 3(a), increasing the bubble incident velocity can effectively reduce the area of ​​salt cells after crystallization and significantly improve the desalination rate of seawater. As shown in Figure 3(b), the effect is best when the bubble incident angle is parallel to and opposite to the crystallization direction.

[0046] The specific principle is that the movement of the incident bubble accelerates the movement of the surrounding seawater fluid in the opposite direction to the direction of bubble incidence, thereby enhancing the effect of convection on salt mass transfer in seawater. This allows the crystallized salt to be transported to areas away from ice crystals in a timely manner, preventing the accumulation of salt near dendrites and the formation of salt cells. On the other hand, the added non-condensable gas is inexpensive and pollution-free, and it can dissipate into the air on its own after melting, without placing any additional burden on the seawater desalination process.

[0047] like Figures 4 to 7 As shown, the seawater cryogenic desalination device of the present invention includes a gas storage tank 1, a gas-liquid mixing tank 5, and a metal rotating drum 6. The gas-liquid mixing tank 5 is connected to the gas storage tank 1 via an air inlet pipe 4. The lower part of the metal rotating drum 6 is located inside the gas-liquid mixing tank 5.

[0048] In this embodiment, the gas-liquid mixing box 5 is in the shape of a semi-cylindrical tube. The gas-liquid mixing box 5 includes an arc-shaped outer bottom plate located on the outer side, an arc-shaped inner bottom plate located on the inner side, side plates 12 disposed on the symmetrical sides of the arc-shaped outer bottom plate and the arc-shaped inner bottom plate, and two top plates connecting the top of the arc-shaped outer bottom plate and the top of the arc-shaped bottom plate.

[0049] In this embodiment, the arc-shaped outer bottom plate and the arc-shaped inner bottom plate are concentrically arranged, with the arc-shaped inner bottom plate located inside the arc-shaped outer bottom plate, meaning the radius of the arc-shaped inner bottom plate is smaller than that of the arc-shaped outer bottom plate. Therefore, an arc-shaped gap exists between the arc-shaped outer bottom plate and the arc-shaped inner bottom plate. This gap, together with the side plates and the two top plates, forms a relatively enclosed space, which is the jet chamber 10.

[0050] The arc-shaped inner bottom plate and the side plates on both sides form a semi-cylindrical cavity, which is the seawater cryogenic crystallization cavity 11. The metal rotating cylinder 6 is cylindrical and contains a low-temperature refrigerant. The lower part of the metal rotating cylinder 6 is located inside the seawater cryogenic crystallization cavity 11, and there is a gap between the outer wall of the metal rotating cylinder and the arc-shaped inner bottom plate. Non-condensable gases and seawater enter the seawater cryogenic crystallization cavity 11 simultaneously, and the lower part of the metal rotating cylinder 6 is immersed in the seawater in the seawater cryogenic crystallization cavity 11. Under the disturbance of the non-condensable gases, the fresh seawater condenses more rapidly on the outer surface of the metal rotating cylinder 6.

[0051] The bottom of the arc-shaped outer base plate is connected to the gas storage tank 1 via an air inlet pipe 4, and several waterproof jet nozzles 7 are spaced apart on the arc-shaped inner base plate. The purpose of these waterproof jet nozzles is twofold: firstly, to allow gas in the jet chamber to enter the seawater in the form of bubbles and mix with the seawater; and secondly, to prevent seawater from flowing back into the seawater freezing and crystallization chamber. Gas from the gas storage tank 1 enters the jet chamber 10 through the air inlet pipe 4. The jet chamber 10 is used to disperse non-condensable gases and control the gas injection. The non-condensable gases entering the jet chamber 10 are injected into the seawater freezing and crystallization chamber 11 through the waterproof jet nozzles 7 on the arc-shaped inner base plate.

[0052] An air pump 2 and a control valve 3 are installed on the air intake pipe 4. The gas storage tank 1 stores non-condensable gases, which are typically immiscible with water, such as carbon dioxide or nitrogen, and are low-cost and pollution-free. During operation, the air pump 2 draws the non-condensable gases from the storage tank 1 through the air intake pipe 4 into the gas-liquid mixing chamber. The control valve 3 precisely controls the gas flow rate in the air intake pipe, thereby adjusting and controlling the rising speed of the bubbles in the gas-liquid mixing chamber.

[0053] A seawater inlet 8 is located on the top of one side of the gas-liquid mixing tank 5, and a seawater outlet 9 is located on the top of the other side of the gas-liquid mixing tank. In this embodiment, several seawater inlets are spaced apart along the axial direction on the top of one side of the gas-liquid mixing tank, and several seawater outlets are spaced apart along the axial direction on the top of the other side of the gas-liquid mixing tank. Seawater flows into the seawater freezing and crystallization chamber 11 through the seawater inlet 8. Under the disturbance of non-condensable gas, the fresh seawater is rapidly frozen and crystallized on the outer surface of the metal rotating cylinder 6, and the remaining concentrated seawater is discharged through the seawater outlet 9 on the other side.

[0054] In this embodiment, the annular inner bottom plate and the annular outer bottom plate are integrally formed, thus creating an arc-shaped chassis 13. A seawater inlet 8 is located at the top edge of one side of the arc-shaped chassis 13, and a seawater outlet 9 is located at the top edge of the other side. A hollow cavity, which is the jet chamber 10, is located in the lower part of the arc-shaped chassis 13. The bottom of the outer side of the arc-shaped chassis 13 is connected to the gas storage tank 1. A waterproof jet nozzle 7 is located on the arc-shaped inner surface of the jet chamber 10 of the arc-shaped chassis 13. After the non-condensable gas enters the jet chamber 10, it is then ejected through the waterproof jet nozzle 7 into the seawater freezing and crystallization chamber 11.

[0055] The method for achieving seawater freezing and crystallization desalination using the above-mentioned device is as follows.

[0056] Seawater enters the seawater freezing and crystallization chamber 11 through the seawater inlet 8. At the same time, the air pump 2 is activated, drawing non-condensable gas from the gas storage tank 1 into the jet chamber 10. Then, the gas in the jet chamber 10 is injected into the seawater freezing and crystallization chamber 11 in a bubble-like manner through the waterproof jet nozzle 7, and is fully mixed with the seawater in the seawater freezing and crystallization chamber 11.

[0057] Since the lower part of the metal rotating cylinder 6 is submerged in seawater within the seawater crystallization chamber 11, the low-temperature refrigerant inside the metal rotating cylinder 6 causes the seawater outside the cylinder to gradually freeze. Therefore, the fresh seawater mixed with non-condensable gases gradually crystallizes on the outer surface of the metal rotating cylinder 6. As the metal rotating cylinder 6 rotates, the ice layer on the outer surface of the metal rotating cylinder gradually thickens.

[0058] Non-condensable gases play a crucial role in the ice crystal production process, promoting faster ice crystal growth and suppressing salinity during crystallization. This significantly improves the production efficiency and quality of ice crystals during seawater cryopreservation, thus enabling seawater cryopreservation and desalination.

[0059] Finally, the ice layer on the outer surface of the metal drum 6 was separated by a scraper, thus realizing the recycling of fresh water.

[0060] This application also discloses a seawater cryogenic desalination system including the aforementioned seawater cryogenic desalination device. For example... Figure 8 As shown, the system includes a refrigeration compressor 19, an auxiliary condenser 18, a main condenser 16, a throttling valve 17, a seawater desalination unit, and a seawater precooling unit 20. The refrigeration compressor 19, the auxiliary condenser 18, the main condenser 16, the throttling valve 17, and the seawater desalination unit are connected in sequence to form a refrigeration cycle.

[0061] The refrigerant enters the refrigeration compressor 19, undergoes refrigeration treatment, and then enters the auxiliary condenser 18 for further refrigeration. It then flows to the main condenser 16. After heat exchange in the main condenser 16, the refrigerant temperature decreases further. Then, the refrigerant flows through the expansion valve 17 into the metal drum 6. The refrigerant in the metal drum 6 exchanges heat with the seawater in the seawater freezing and crystallization chamber, providing cooling to the seawater, causing it to cool and crystallize on the outer surface of the metal drum 6. The refrigerant that has absorbed heat from the seawater is then guided back to the refrigeration compressor 19, forming a refrigeration cycle. Through the heat exchange of the refrigerant, the required cooling capacity is provided for seawater crystallization in the seawater desalination unit.

[0062] The seawater desalination system also includes a scraper 15. As the metal drum 6 rotates, the ice layer crystallizing on its outer wall gradually thickens. After the ice layer is cleaned by the seawater cleaner 14, the scraper 15 scrapes off the ice layer from the outer wall of the metal drum 6. The scraped-off ice layer is sent to the main condenser 16, where heat exchange occurs. The refrigerant in the main condenser 16 absorbs the cold energy from the ice layer, thereby further reducing the refrigerant temperature.

[0063] The ice layer flowing out of the main condenser 16 and the low-temperature concentrated seawater flowing out of the seawater desalination unit all flow into the seawater precooling device 20. In the seawater precooling device 20, the seawater that is about to flow into the seawater desalination unit exchanges heat with the ice crystals and the low-temperature concentrated seawater: the seawater absorbs the cold energy of the ice crystals and the low-temperature concentrated seawater, thereby further reducing the temperature of the seawater, so that the seawater flowing into the seawater desalination unit is low-temperature seawater.

[0064] The working principle of this seawater desalination system is as follows: A low-temperature refrigerant is supplied to the metal rotating drum in the seawater desalination unit through a refrigeration circulation section. During operation, seawater, which has undergone preliminary cooling by a pre-cooling device, enters the seawater freezing and crystallization chamber through the seawater inlet. Under the disturbance of non-condensable gases, the fresh seawater continuously crystallizes on the outer surface of the metal rotating drum, while the concentrated seawater is discharged from the seawater outlet of the seawater desalination unit.

[0065] The concentrated seawater flowing from the seawater desalination unit enters the seawater precooling unit 20 to provide cooling for the seawater inside. Ice crystals on the outer surface of the metal rotating drum 6 are continuously scraped off by the scraper 15. The scraped ice layer falls directly into the main condenser 16, providing cooling for the refrigerant inside. Afterward, it is transported back to the seawater precooling unit 20 to provide cooling for the seawater inside.

[0066] This seawater cryogenic desalination system enables the cryogenic desalination of seawater, the circulation of refrigerant, and the recycling of cooling capacity.

[0067] The above provides a detailed description of the seawater cryogenic desalination device, method, and system based on multiphase flow control provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention. The above description of the disclosed embodiments enables those skilled in the art to implement or use this invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this invention. Therefore, this invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A seawater cryogenic desalination device based on multiphase flow control, characterized in that, include: The gas-liquid mixing tank includes an arc-shaped chassis and symmetrically arranged side plates on both sides of the arc-shaped chassis. A seawater inlet is provided on one side of the top of the arc-shaped chassis, and a seawater outlet is provided on the corresponding top side of the other side. The arc-shaped chassis is semi-cylindrical in shape. Several seawater inlets and seawater outlets are symmetrically arranged on both sides of the top of the arc-shaped chassis. The seawater inlets and seawater outlets are spaced apart along the axial direction of the arc-shaped chassis. The lower part of the arc-shaped chassis is equipped with a jet chamber, and several waterproof jet nozzles are provided on the arc-shaped inner surface of the arc-shaped chassis. The arc-shaped chassis and the two side plates together form a seawater freezing and crystallization chamber. The incident angle of the bubble is parallel to and opposite to the crystallization direction; The metal rotating cylinder is cylindrical in shape and contains a low-temperature refrigerant. The lower part of the metal rotating cylinder is placed inside the seawater freezing and crystallization chamber. The gas injection section is connected to the bottom of the arc-shaped chassis.

2. The seawater cryogenic desalination device based on multiphase flow control according to claim 1, characterized in that, The gas injection unit includes a gas storage tank, which is connected to the bottom of the arc-shaped chassis via an air intake pipe. An air pump and a control valve are installed on the air intake pipe, and the gas in the gas storage tank flows into the jet chamber through the air intake pipe.

3. A method for seawater cryo-desalination using the seawater cryo-desalination device based on multiphase flow control as described in any one of claims 1-2, characterized in that, Includes the following steps: Seawater flows into the seawater freezing and crystallization chamber through the seawater inlet. At the same time, non-condensable gas in the gas storage tank enters the jet chamber through the air intake pipe. Non-condensable gas in the jet chamber enters the seawater freezing and crystallization chamber in the form of bubbles through the waterproof jet nozzle and mixes with the seawater. Increasing the bubble incident velocity reduces the area of ​​the salt cells after crystallization, thereby improving the desalination rate of seawater. The bubble incident angle is parallel to and opposite to the crystallization direction. The lower part of the metal rotating cylinder is immersed in seawater in the seawater freezing and crystallization chamber. The low-temperature refrigerant inside the cylinder causes the fresh seawater mixed with non-condensable gases to gradually crystallize on the outer surface of the metal rotating cylinder. The ice layer on the outer surface of the metal drum is scraped off to achieve freshwater recycling.

4. The method for seawater cryopreservation according to claim 3, characterized in that, During the ice crystal production process, the disturbance of non-condensable gases makes ice crystals grow faster and inhibits salinity during the crystallization process. Concentrated seawater without crystallization flows out from the seawater outlet.

5. A seawater desalination system comprising the seawater desalination apparatus based on multiphase flow control as described in any one of claims 1-2, characterized in that, Also includes: Refrigeration compressor, auxiliary condenser, main condenser, expansion valve, scraper and seawater precooling device; The refrigeration compressor, auxiliary condenser, main condenser, expansion valve, and metal drum are connected in sequence to form the refrigeration cycle section.

6. The seawater cryogenic desalination system according to claim 5, characterized in that, After the refrigeration compressor cools the refrigerant, the refrigerant passes through the auxiliary condenser, the main condenser, and the expansion valve in sequence, and finally flows into the metal drum. The refrigerant in the metal drum exchanges heat with the seawater and then flows back into the refrigeration compressor, thus realizing the refrigerant cycle.

7. The seawater cryogenic desalination system according to claim 5, characterized in that, The ice layer scraped off the outer surface of the metal drum by a scraper falls directly into the main condenser, where heat exchange occurs between the refrigerant and the ice layer.

8. The seawater cryogenic desalination system according to claim 6, characterized in that, Ice enters the seawater precooling device from the main condenser. Concentrated seawater flowing out of the seawater desalination device enters the precooling device. After the desalinated seawater passes through the seawater precooling device, it enters the seawater desalination device. Inside the seawater precooling device, heat exchange is achieved between the ice layer and the seawater to be desalinated, as well as between the concentrated seawater and the seawater to be desalinated, so that the seawater to be desalinated entering the seawater cryogenic desalination device is low-temperature seawater.

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