System for making fresh water by utilizing rotary drum sail and BOG (Boil Off Gas) cold energy for LNG (Liquefied Natural Gas) ship
By designing a rotor sail and BOG cold energy freshwater system on LNG ships, the problems of unused BOG cold energy and large energy consumption of ship freshwater acquisition methods are solved, and the effect of efficient use of BOG cold energy and reducing energy consumption is achieved.
Patent Information
- Application Number
- CN202411832582.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2025-03-07
AI Technical Summary
The BOG cold energy generated by traditional LNG transport ships during navigation has not been fully utilized, resulting in waste of energy. At the same time, the existing methods of obtaining freshwater in ships rely on electricity or heat energy to consume a large amount, which increases energy consumption and operation costs.
A system for producing freshwater by using rotor sails and BOG cold energy is designed. The outer surface of the rotor sail is accelerated by the BOG's cold energy, collecting ice crystals and processing it as the source of freshwater for the ship.
It realizes efficient utilization of BOG cooling energy, reduces dependence on other seawater desalination equipment, reduces the energy consumption and operating costs of ships, and provides an additional source of fresh water.
Smart Images
Figure CN119568390A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of ships and discloses a system for producing fresh water by using a rotary sail and BOG cold energy on an LNG ship. Background Art
[0002] As the global demand for liquefied natural gas (LNG) increases, the number of LNG carriers increases, and the International Maritime Organization (IMO) has higher and higher standards for ship carbon emissions. More and more ships are using rotor sails to use wind energy to propel the ships, reduce fuel consumption, and reduce carbon emissions.
[0003] However, there are many deficiencies in energy utilization in the traditional LNG carrier operation mode. The storage temperature of LNG is -163℃. During the voyage of the ship, the LNG cargo tank will exchange heat with the outside world, thereby generating a large amount of LNG boil-off gas (BOG). The conventional method of handling BOG is to heat the BOG and send it directly to the main engine for use as engine fuel. However, the rich cold energy contained in BOG is not fully utilized before it is sent to the main engine, resulting in a waste of cold energy. Therefore, in the process of pursuing efficient and green operation of ships, the traditional BOG handling method needs to be improved and optimized.
[0004] Ships sailing on the sea have a large demand for fresh water supply. For example, the main engine, boiler and other equipment on the ship, as well as the crew's living water, all rely on sufficient fresh water. At present, the mainstream way for ships to obtain fresh water is still through seawater desalination equipment, and seawater desalination equipment consumes a lot of electricity or heat energy to drive the seawater desalination process during operation, which in turn increases the energy consumption and operating costs of the ship. Therefore, in the context of pursuing overall energy efficiency and green operation, the existing ship fresh water acquisition model needs to be optimized and innovated.
[0005] When a ship is sailing at sea, the air humidity is high and the water vapor in the air does not contain salt. When the water vapor is cooled, it will condense into ice crystals. Therefore, it is possible to consider collecting these ice crystals and converting them into usable fresh water, which will become a good source of fresh water for the ship.
[0006] Based on the above problems, if a LNG ship can be designed to use the rotor sail and BOG cold energy to produce fresh water system. By using the cold energy of BOG to accelerate the freezing speed of the outer surface of the rotor sail, these ice crystals can be collected and used as an additional source of fresh water for the ship, which can not only achieve efficient use of BOG cold energy, but also reduce the ship's dependence on other seawater desalination equipment. Summary of the invention
[0007] The purpose of the present invention is to solve the above problems and propose a system for producing fresh water on an LNG ship using a rotary sail and BOG cold energy, the system comprising: an LNG cargo hold, a fresh water preparation unit, a fuel processing unit, an ice crystal collection unit, an ice crystal processing unit, and a fresh water collection cabinet. The fresh water preparation unit comprises: a rotary sail, a sail sleeve, a sail center shaft, a bottom bearing, a top bearing, a bearing sealing device, a bearing sealing cover, a bearing sealing ring, a sail return pipe, a return port, a bottom air inlet, an upper return port, an ice scraper, an ice scraper handle, an ice leaking port, an ice leaking port cover, an ice leaking pin, a telescopic device, a compressor, a compressor exhaust pipe, a scraper, an insulation layer, and a limit plate.
[0008] The rotary sail is placed on the deck at the bow of the ship, and uses the Magnus effect to assist in the propulsion of the ship. The rotary sail consists of a sail sleeve, a sail center shaft, a bottom bearing, a top bearing, a sail return air pipe, a bottom air inlet, and an upper air return port, wherein the outer wall of the sail center shaft is provided with an insulation layer to prevent the outer surface of the sail center shaft from freezing and affecting the operation of the equipment. The bearing sealing device consists of a bearing sealing cover and a bearing sealing ring, which ensures the sealing of the enclosed space composed of the inner wall of the sail sleeve, the outer wall of the sail center shaft and the bearing sealing device, and prevents BOG leakage.
[0009] The ice scraper is composed of an ice scraper handle, an ice outlet, an ice outlet cover, and a scraper. The bottom plane of the ice scraper forms an angle with the horizontal plane, and the angle is an acute angle. The ice outlet is located at the bottom of the ice scraper, which is convenient for collecting ice crystals. The scraper is in close contact with the central axis of the sail, which is conducive to scraping off ice crystals. The telescopic device is a hydraulic telescopic device, which uses hydraulic pressure to achieve the telescopic function.
[0010] The compressor is located below the deck of the ship, directly below the rotor sail, and is connected to the bottom air inlet located at the rotor sail base through the compressor exhaust pipe. The upper air return port is located above the sail center axis column, and is connected to the air return port at the bottom of the rotor sail through the sail air return pipe along the axis of the sail center axis. The top bearing and the bottom bearing are respectively located at the top and bottom of the rotor sail, and cooperate with the sail sleeve and the sail center axis. The limit plate is arranged below the sealing device of the top bearing and is in close contact with the sealing device, with the purpose of supporting the sealing device and preventing the sealing device from slipping. The ice scraper is sleeved on the sail sleeve and is connected to the telescopic device through the ice scraper handle. The scraper is in close contact with the sail center axis. The ice leakage port is located at the bottom of the ice scraper and is embedded with the ice leakage port cover. The ice leakage pin is located below the deck.
[0011] The fuel processing unit is connected to the bottom air inlet, the ice crystal processing unit is connected to the fresh water preparation unit, the ice crystal collection unit is connected to the ice crystal processing unit, and the fresh water collection cabinet is connected to the ice crystal processing unit.
[0012] During the voyage of LNG ships, a large amount of BOG will be generated in the LNG cargo hold due to the infiltration of external heat into the LNG cargo hold. After being compressed by the compressor, the BOG in the LNG cargo hold enters the closed space composed of the inner wall of the sail sleeve, the outer wall of the sail center shaft and the bearing sealing device. Through the heat exchange between BOG and water vapor in the outside air, the water vapor condenses into ice crystals on the outer wall of the sail sleeve. When the ice crystals on the outer surface of the rotary sail reach a certain thickness, the telescopic device begins to extend upward, driving the ice scraper to move upward. The scraper inside the ice scraper is in close contact with the outer surface of the rotary sail. When the ice scraper moves upward, the ice will be scraped into the ice scraper container. Because the bottom surface of the ice scraper is an inclined surface, the scraped ice crystals will gather at the bottom of the inclined surface of the ice scraper, that is, on the side of the ice leak. When the ice scraper moves to the top of the rotary sail, the telescopic device begins to contract, driving the ice scraper to move downward. A half-moon-shaped opening is provided at the bottom of the rotary sail, and the half-moon-shaped opening extends below the ship deck, forming a half-moon-shaped space, so that the ice leakage port of the ice scraper can be lowered below the ship deck. When the ice scraper moves into the half-moon-shaped space and contacts the ice leakage pin located below the ship deck and directly below the ice leakage port, the ice leakage pin props up the ice leakage port cover, and ice crystals slide from the ice leakage port into the ice crystal collection unit. Thus, an ice scraping process is completed.
[0013] Subsequently, the ice crystals are sent to the ice crystal processing unit for melting, filtering, and sterilization. After completing the above steps, the ice crystals become fresh water and are sent to the fresh water collection cabinet for storage. At the same time, BOG enters the sail return air pipe through the upper return air port, and then enters the fuel processing unit through the return air port for pressurization and heating, and then is sent to the main engine for combustion to provide power for the ship.
[0014] Beneficial effects of the present invention:
[0015] 1. The present invention passes BOG of LNG into the rotary sail, and uses the extremely low temperature BOG to exchange heat with water vapor in the outside air, so that the water vapor is quickly cooled and condensed into ice crystals on the surface of the sail sleeve, thereby efficiently utilizing the cold energy of BOG of LNG.
[0016] 2. The present invention passes BOG into the rotor sail, which not only fully utilizes the cold energy of BOG, but also increases the temperature of BOG during the heat exchange between BOG and water vapor in the outside air, thereby reducing the energy consumption when heating BOG before it is sent to the main engine for combustion.
[0017] 3. The present invention utilizes the advantages of the large circumference area of the rotor sail and its fast rotation speed, combined with the characteristics of high humidity and strong air flow disturbance at sea, so that more water vapor can be condensed into ice crystals through the rotor sail and BOG heat exchange, thereby producing more fresh water and reducing the ship's dependence on other seawater desalination equipment. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1Schematic diagram of the position of the rotor sail on a ship according to the present invention
[0019] Figure 2 The schematic diagram of the rotor sail structure of the present invention is
[0020] Figure 3 The schematic diagram of the assembly of the rotor sail structure of the present invention is
[0021] Figure 4 A cross-sectional view of the rotor sail of the present invention
[0022] Figure 5 Schematic diagram of the ice scraper of the present invention
[0023] Figure 6 The internal structure diagram of the ice scraper of the present invention
[0024] Figure 7 The system diagram of the present invention
[0025] Figure 8 Schematic diagram of the flow of BOG in the rotor sail of the present invention
[0026] Fig. 9 Schematic diagram of the ice scraper of the present invention starting to scrape ice
[0027] Fig.10 Schematic diagram of the ice scraper of the present invention during the half-process of scraping ice
[0028] Fig.11 Schematic diagram of the end of ice scraping by the ice scraper of the present invention
[0029] In the attached figure: 1. Rotor sail; 2. Sail sleeve; 3. Sail center axis; 4. Bottom bearing; 5. Top bearing; 6. Bearing sealing device; 601. Bearing sealing cover; 602. Bearing sealing ring; 7. Sail return air pipe; 8. Return air port; 9. Bottom air inlet; 10. Upper return air port; 11. Ice scraper; 12. Ice scraper handle; 13. Ice leak port; 14. Ice leak port cover; 15. Ice leak pin; 16. Telescopic device; 17. Compressor; 18. Compressor exhaust pipe; 19. Scraper; 20. Insulation layer; 21. Limit plate; 22. LNG cargo hold; 23. Fresh water preparation unit; 24. Fuel processing unit; 25. Ice crystal collection unit; 26. Ice crystal processing unit; 27. Fresh water collection cabinet DETAILED DESCRIPTION
[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings.
[0031] like Figure 1 , Figure 2 , Figure 3 , Figure 4As shown, the present invention proposes a system for producing fresh water by using a rotary sail and BOG cold energy on an LNG ship, and the system includes: an LNG cargo hold 22, a fresh water preparation unit 23, a fuel processing unit 24, an ice crystal collection unit 25, an ice crystal processing unit 26, and a fresh water collection cabinet 27. The fresh water preparation unit 23 includes: a rotary sail 1, a sail sleeve 2, a sail center shaft 3, a bottom bearing 4, a top bearing 5, a bearing sealing device 6, a bearing sealing cover 601, a bearing sealing ring 602, a sail return air pipe 7, a return air port 8, a bottom air inlet 9, an upper return air port 10, an ice scraper 11, an ice scraper handle 12, an ice leaking port 13, an ice leaking port cover 14, an ice leaking pin 15, a telescopic device 16, a compressor 17, a compressor exhaust pipe 18, a scraper 19, an insulation layer 20, and a limit plate 21.
[0032] like Figure 1 , Figure 2 As shown, the rotor sail 1 is placed on the deck at the bow of the ship, and uses the Magnus effect to assist in the propulsion of the ship. The rotor sail 1 is composed of a sail sleeve 2, a sail center shaft 3, a bottom bearing 4, a top bearing 5, a return air pipe 7, a bottom air inlet 9, and an upper return air inlet 10. Figure 3 As shown, the bearing sealing device 6 is composed of a bearing sealing cover 601 and a bearing sealing ring 602, which ensures the sealing of the closed space composed of the inner wall of the sail sleeve 2, the outer wall of the sail center shaft 3 and the bearing sealing device 6, and prevents the combustible gas BOG from leaking to the outside. Figure 3 This is a schematic diagram of the assembly of the rotor sail structure of the present invention. Figure 3 The arrow in the figure indicates that the sail sleeve 2 is split upward from the rotor sail 1 along the direction of the arrow, so as to show the internal structural connection and matching relationship of the rotor sail 1.
[0033] The compressor 17 is located below the ship deck, just above the rotor sail 1, and is connected to the bottom air inlet 9 located at the base of the rotor sail 1 through the compressor exhaust pipe 18. The upper air return port 10 is located above the column of the sail axis 3, and is connected to the air return port 8 located at the bottom of the rotor sail 1 through the sail air return pipe 7 along the axis direction of the sail axis 3. The top bearing 5 and the bottom bearing 4 are respectively located above and below the rotor sail 1, and their interiors and exteriors are respectively engaged with the outer surface of the sail axis 3 and the inner surface of the sail sleeve 2. The ice leakage pin 15 is located below the deck, just below the ice leakage port 13.
[0034] like Figure 4 , Figure 5 , Figure 6As shown, the ice scraper 11 is composed of an ice scraper handle 12, an ice outlet 13, an ice outlet cover 14, and a scraper 19. The bottom plane of the ice scraper 11 forms an angle with the horizontal plane, and the angle is an acute angle. The ice scraper handle 12 is connected to the telescopic device 16, and the scraper 19 is in close contact with the sail axis 3 to scrape off ice crystals. The ice outlet 13 is located at the bottom of the ice scraper 11 to facilitate the collection of ice crystals, and the ice outlet cover 14 is embedded with the ice outlet 13. Figure 4 As shown, the outer wall of the sail shaft 3 is provided with an insulation layer 20 to prevent the outer surface of the sail shaft 3 from icing and affecting the operation of the equipment, wherein: Figure 4 A in the figure represents ice crystals condensed on the outer surface of the rotor sail 1 . Figure 6 The arrow in the figure indicates the movement direction of the ice leakage cover 14 when it is lifted up by the ice leakage pin 15, and A indicates the ice crystals collected in the ice scraper 11. The telescopic device 16 is a hydraulic telescopic device, which realizes the telescopic function by using hydraulic pressure.
[0035] like Figure 7 As shown, the fuel processing unit 24 is connected to the air return port 8 , the ice crystal processing unit 26 is connected to the fresh water preparation unit 23 , the ice crystal collection unit 25 is connected to the ice crystal processing unit 26 , and the fresh water collection cabinet 27 is connected to the ice crystal processing unit 26 .
[0036] During the navigation of the LNG ship, due to the penetration of external heat into the LNG cargo hold 22, a large amount of BOG will be generated in the LNG cargo hold 22. The BOG in the LNG cargo hold 22 is compressed by the compressor 17 and enters the closed space composed of the inner wall of the sail sleeve 2, the outer wall of the sail center axis 3 and the bearing sealing device 6. Since the air humidity at sea is high, the air contains a lot of water vapor, and the BOG temperature of LNG can reach -150℃~-140℃, while the temperature of water vapor in the air at sea is usually 15℃, and can even reach above 30℃ in tropical areas near the equator. Generally, the higher the temperature in the air, the greater the moisture content. Therefore, there is a huge temperature difference between BOG and the large amount of water vapor in the air, so that the water vapor on the outer surface of the sail sleeve 2 of the rotary sail 1 can quickly form more ice crystals. When the ice crystals on the outer surface of the sail sleeve 2 of the rotary sail 1 reach a certain thickness, the telescopic device 16 begins to extend upward, driving the ice scraper 11 to move upward, such as Fig. 9 , Fig.10 , Fig.11 As shown, the scraper 19 inside the ice scraper 11 is in close contact with the outer surface of the rotor sail 1. Since the relative rotation speed between the rotor sail 1 and the scraper 19 is fast, ice crystals will be easily scraped into the container of the ice scraper 11 when the ice scraper 11 moves upward. Since the bottom surface of the ice scraper 11 is an inclined surface, the scraped ice crystals will gather at the bottom of the inclined surface of the ice scraper 11, that is, on the side of the ice leaking port 13. When the ice scraper 11 moves to the top of the rotor sail 1, the telescopic device 16 begins to shrink, driving the ice scraper 11 to move downward.
[0037] A half-moon-shaped opening is provided at the bottom of the rotor sail 1, and the half-moon-shaped opening extends below the ship deck to form a half-moon-shaped space, so that the ice leakage port 13 of the ice scraper 11 can be lowered below the ship deck. When the ice scraper 11 moves into the half-moon-shaped space and contacts the ice leakage pin 15 located below the ship deck and directly below the ice leakage port 13, the ice leakage pin 15 props up the ice leakage port cover 14, and ice crystals slide from the ice leakage port 13 into the ice crystal collection unit 25. Figure 6 As shown. Thus, one ice scraping process is completed.
[0038] Furthermore, considering that the telescopic device 16 and the ice scraper 11 will affect the wind field around the rotor sail 1, and thus affect the boosting effect of the rotor sail 1, a certain time interval needs to be set between each ice scraping operation, and the length of the time interval is adjusted according to the actual situation. For example, the ice scraping operation can be set every 5 minutes, or even longer. In addition, when the ice scraping device is not performing the ice scraping operation, the telescopic device 16 is lowered to the lowest position, that is, below the deck of the ship. At this time, the ice scraper 11 is at the bottom of the rotor sail 1 and will not affect the wind field around the rotor sail 1.
[0039] Subsequently, the ice crystals are sent to the ice crystal processing unit 26 for melting, filtering, and sterilization. After completing the above steps, the ice crystals become fresh water and are sent to the fresh water collection cabinet 27 for storage. Figure 7 , Figure 8 As shown, Figure 8 B in the middle represents BOG from the LNG cargo tank 22. The BOG enters the sail return pipe 7 through the upper return port 10, and then enters the fuel processing unit 24 through the return port 8 for pressurization and heating, and then is sent to the main engine for combustion to provide power for the ship. The usual way to process BOG is to directly pressurize and heat it and then send it to the main engine for combustion. In the present invention, BOG exchanges heat with water vapor in the outside air during the process of passing into the rotary sail 1, and part of the cold energy of BOG is used, and the temperature is increased, so the energy consumption of heating BOG is reduced during the process of heating BOG in the fuel processing unit 24.
[0040] The rotor sail 1 has a very large circumferential area. For example, the world's largest rotor sail 1 has a height of 35m, a diameter of 5m, and a circumferential area of about 550m. 2In the process of passing low-temperature BOG into the rotor sail 1 to make ice crystals, the heat exchange coefficient between the circumferential surface of the rotor sail 1 and the moist air at sea is increased due to the large circumferential area of the rotor sail 1. The large heat exchange coefficient enables water vapor in the air to condense more quickly on the surface of the rotor sail 1 to form a large number of ice crystals, and the ice crystals produced are used to make fresh water. The present invention cleverly uses the large circumferential area of the rotor sail 1 to make a large amount of fresh water, which can not only be used as a fresh water supplement for the main engine, boiler and other equipment on the ship and the crew's domestic water, but also efficiently utilizes the cold energy before the BOG is passed into the main engine, avoiding the waste of cold energy.
[0041] The air humidity at sea is high, and the air contains abundant water vapor, which provides favorable conditions for the formation of ice crystals. In addition, the linear velocity of the surface of the rotor sail 1 is very high, and the tangential linear velocity of the surface of the rotor sail 1 can usually reach 40m / s to 50m / s. When the rotor sail 1 rotates at high speed, it is like a powerful "stirrer", which enhances the air flow disturbance effect around the rotor sail 1, so that the rotor sail 1 can fully contact more water vapor in the air, prompting the water vapor to condense into a large number of ice crystals, greatly improving the efficiency of fresh water production.
[0042] Traditional seawater desalination technologies on ships, such as distillation and electrodialysis, consume too much energy per unit of water production. The present invention uses the cold energy of BOG before it is sent to the main engine to prepare fresh water, reducing dependence on seawater desalination equipment, which is in line with the development trend of the shipping industry.
[0043] The above is only a preferred implementation mode of the present invention, but it is not limited to the above embodiments when it is implemented. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A system for producing fresh water from a LNG ship using a rotary sail and BOG cold energy, characterized in that: The present invention comprises an LNG cargo hold (22), a fresh water preparation unit (23), a fuel processing unit (24), an ice crystal collection unit (25), an ice crystal processing unit (26), and a fresh water collection cabinet (27); the fresh water preparation unit (23) comprises a rotary sail (1), a sail sleeve (2), a sail center shaft (3), a bottom bearing (4), a top bearing (5), a bearing sealing device (6), a bearing sealing cover (601), a bearing sealing ring (602), a sail return air pipe (7), an air return port (8), a bottom air inlet (9), an upper air return port (10), an ice scraper (11), an ice scraper handle (12), an ice leakage port (13), an ice leakage port cover (14), an ice leakage pin (15), a telescopic device (16), a compressor (17), a compressor exhaust pipe (18), a scraper (19), an insulation layer (20), and a limit plate (21); The rotary sail (1) is composed of a sail sleeve (2), a sail center axis (3), a bottom bearing (4), a top bearing (5), a sail return air pipe (7), a bottom air inlet (9), and an upper return air port (10); the outer wall of the sail center axis (3) is provided with a heat preservation layer (20); the upper return air port (10) is located above the column of the sail center axis (3) and communicates with the return air port (8) located at the bottom of the rotary sail (1) through the sail return air pipe (7); the top bearing (5) and the bottom bearing (4) are respectively located at the top and the bottom of the rotary sail (1); the bearing sealing device (6) is composed of a bearing sealing cover (601) and a bearing sealing ring (602); The ice scraper (11) is sleeved on the sail sleeve (2) and connected to the telescopic device (16) via an ice scraper handle (12); the compressor (17) is located below the ship deck and directly below the rotary sail (1), and is connected to the air inlet (9) at the bottom of the rotary sail (1) via a compressor exhaust pipe (18); the air return port (8) is connected to the fuel processing unit (24) via a pipeline; and the ice crystal collection unit (25) is connected to the ice crystal processing unit (26) and the fresh water collection cabinet (27) in sequence via a pipeline.
2. The system for producing fresh water by using rotary sail and BOG cold energy of LNG carrier according to claim 1 is characterized in that: The ice scraper (11) is composed of an ice scraper handle (12), an ice outlet (13), an ice outlet cover (14), and a scraper (19). The scraper (19) is in close contact with the sail center axis (3). The bottom plane of the ice scraper (11) forms an angle with the horizontal plane, which is an acute angle. The ice outlet (13) is located at the bottom end of the ice scraper (11).
3. The system for producing fresh water by using rotary sail and BOG cold energy of LNG carrier according to claim 1 is characterized in that: The sail air return pipe (7) is opened inside the sail central axis (3) along the axial direction of the sail central axis (3); and the upper air return port (10) is opened in the circumferential direction of the sail central axis (3).
4. The system for producing fresh water by using rotary sail and BOG cold energy of LNG carrier according to claim 1 is characterized in that: A half-moon-shaped opening is provided at the bottom of the rotor sail (1), and the half-moon-shaped opening extends below the ship deck to form a half-moon-shaped space; the ice leaking pin (15) is located below the ship deck, directly below the ice leaking opening (13) of the ice scraper (11), and at the bottom of the half-moon-shaped space.
5. The system for producing fresh water by using rotary sail and BOG cold energy of LNG carrier according to claim 1 is characterized in that: During the voyage of the LNG ship, BOG in the LNG cargo hold (22) enters a closed space formed by the inner wall of the sail sleeve (2), the outer wall of the sail center shaft (3) and the bearing sealing device (6) through the compressor (17). The BOG exchanges heat with water vapor in the outside air, causing the water vapor to condense into ice crystals on the outer wall of the sail sleeve (2). Then, the telescopic device (16) extends upward, driving the ice scraper (11) to move upward, scraping the ice crystals into the ice scraper (11). The scraped ice crystals gather at the bottom of the inclined surface of the ice scraper (11). When the ice scraper (11) moves to the top of the rotary sail (1), the ice crystals are condensed into ice crystals. Afterwards, the telescopic device (16) contracts, driving the ice scraper (11) to move downward. When the ice scraper (11) contacts the ice leakage pin (15), the ice leakage pin (15) props up the ice leakage port cover (14), and ice crystals fall from the ice leakage port (13) into the ice crystal collection unit (25). The ice crystals are then sent to the ice crystal processing unit (26). The processed ice crystals are converted into fresh water and sent to the fresh water collection cabinet (27) for storage. The BOG after utilizing the cold energy enters the sail return air pipe (7) through the upper return air port (10), and then enters the fuel processing unit (24) through the return air port (8) for pressurization and heating, and then is sent to the main engine for combustion.