A cargo hold drying system and method for LNG powered ship

Abstract

The present invention discloses a cargo hold drying system and method for an LNG powered ship, the system mainly comprising: an LNG heat exchange system, an ethylene glycol solution heat exchange system, and a cargo hold ventilation drying system. When the cargo hold needs to be dried, the ethylene glycol solution is used as a refrigerant to cool and dehumidify the cargo hold by utilizing the cold energy of LNG, which can not only improve the utilization rate of the cold energy of LNG, but also reduce the consumption of heat sources in the process of LNG fuel vaporization, thereby realizing the rational utilization of energy. In addition, the system structure of the present invention is simple, easy to install, easy to implement, and does not need to install expensive dehumidification equipment. The investment cost and operation cost are very low, so the present invention has good economic and practical value.

Description

Technical Field

[0001] The present invention belongs to the technical field of ships, and in particular relates to a cargo hold drying system and method of an LNG powered ship. Background Art

[0002] Maritime transport is still one of the important modes of transport in international trade. According to statistics, more than two-thirds of cargo transportation is completed by sea transport. With the rapid development of the economy, the demand for maritime transport is increasing. General cargo ships and bulk carriers have large transportation volumes and are widely used in cargo transportation. The types of goods transported are becoming more and more abundant, such as soybeans, corn, wheat, etc., as well as some industrial products. Such items often require dry space during transportation and are easy to deteriorate under humid conditions. Once the goods are damaged, it will cause huge losses. Therefore, it is necessary to ensure that the cargo hold of the ship is in a relatively dry state when transporting such items.

[0003] At present, most general cargo ships and bulk carriers are not equipped with drying systems. Natural ventilation is usually used. In winter, natural ventilation can basically meet the requirements of cargo hold drying. However, in summer, the temperature is high and the air humidity is high. Natural ventilation alone often cannot meet the requirements of cargo hold drying. For this reason, some ships use silica gel drying. However, silica gel as a desiccant has the problems of large consumption, high cost and insufficient adsorption capacity. Therefore, it is particularly important to install a drying system in the cargo hold. In addition, cooling and dehumidification is also a good drying method. When the water vapor content in the air remains unchanged, the water vapor can be saturated by cooling, and the water in the air condenses into water droplets and is discharged overboard. However, cooling the air requires a separate refrigeration equipment. Since the cargo hold is relatively large, it will increase the power consumption of the system and greatly increase the load on the ship's power grid, which runs counter to the trend of energy conservation and emission reduction for ships.

[0004] Ships that use liquefied natural gas (LNG) as fuel are called "LNG-powered ships". LNG-powered ships include general cargo ships and bulk carriers. These types of ships have a large deadweight, so the power consumption is relatively large. LNG fuel releases a lot of cold energy during the vaporization process. Moreover, when the ship is sailing, LNG cold energy is always generated. If this part of cold energy is used to cool and dehumidify the air in the cargo hold to meet the air humidity requirements of the cargo in the cargo hold, then this method will have greater practical application significance. Summary of the invention

[0005] The purpose of the present invention is to address the above-mentioned problems and to provide a cargo hold drying system and method for an LNG powered ship.

[0006] The first object of the present invention is to provide a cargo hold drying system for an LNG powered ship, the system comprising an LNG heat exchange system, an ethylene glycol solution heat exchange system, and a cargo hold ventilation and drying system.

[0007] The LNG heat exchange system includes: booster pump, LNG heat exchanger, heating circulation pump and cylinder jacket water heater.

[0008] The ethylene glycol solution heat exchange system includes: ethylene glycol heat exchanger, dry circulation pump, fan, cargo hold air cooler, condensate tank and discharge valve.

[0009] The cargo hold ventilation and drying system includes: exhaust valve, return air valve, inlet valve, outside air dew point meter, outside air humidity meter, cargo hold air inlet, cargo hold air outlet, cargo hold air dew point meter, cargo hold air humidity meter, air inlet duct, return air duct and cargo hold.

[0010] In the LNG heat exchange system, the booster pump is connected to the LNG heat exchanger through a pipeline, the LNG heat exchanger is connected to the jacket water heater through a pipeline, and the heating circulation pump is connected to the LNG heat exchanger through a pipeline, wherein a high concentration of ethylene glycol solution circulates in the LNG heat exchange system as refrigerant A. The jacket water heater heats the refrigerant A, and the refrigerant A circulates under the action of the heating circulation pump. The LNG fuel is transferred out from the LNG fuel tank, reaches a certain pressure through the booster pump, flows through the LNG heat exchanger, and exchanges heat with the refrigerant A. The refrigerant A absorbs the cold energy from the LNG, and then the refrigerant A flows through the jacket water heater to be heated again, and the cycle is repeated. The LNG fuel passing through the LNG heat exchanger is vaporized to reach the required temperature of the ship's main power equipment and is sent to the ship's main engine for combustion.

[0011] In the glycol solution heat exchange system, the dry circulation pump is connected to the glycol heat exchanger through a pipeline, the cargo hold air cooler is connected to the condensate tank through a pipeline, a pipeline is arranged under the condensate tank, and a discharge valve is arranged on the pipeline, wherein the glycol solution with a lower concentration is used as the refrigerant B. Refrigerant B exchanges heat with refrigerant A through the glycol heat exchanger, and refrigerant B absorbs the cold energy carried by refrigerant A. Under the action of the dry circulation pump, refrigerant B enters the cargo hold air cooler.

[0012] In the cargo hold ventilation and drying system, a cargo hold air inlet, a cargo hold air outlet, a cargo hold air dew point meter and a cargo hold air humidity meter are provided in the cargo hold, an outside air dew point meter and an outside air humidity meter are provided at the air inlet duct, an exhaust valve is provided on the return air duct, an air inlet valve is provided on the air inlet duct, and a return air valve is provided at the connection between the air inlet duct and the return air duct.

[0013] The second object of the present invention is to provide a method for drying the cargo hold of an LNG powered ship based on the above-mentioned cargo hold drying system of an LNG powered ship.

[0014] The method proposes the following solution:

[0015] Solution 1: When the dew point temperature of the outside air detected by the outside air dew point meter is higher than the dew point temperature of the cargo hold air detected by the cargo hold air dew point meter, natural ventilation is no longer performed at this time, and only the cold energy of LNG is used to cool and dehumidify the air in the cargo hold.

[0016] In the LNG heat exchange system, the cylinder jacket water heater heats the refrigerant A, and the refrigerant A circulates under the action of the heating circulation pump. The LNG fuel is transferred from the LNG fuel tank, reaches a certain pressure through the booster pump, flows through the LNG heat exchanger, and exchanges heat with the refrigerant A. The refrigerant A absorbs the cold energy from the LNG, and then the refrigerant A flows through the cylinder jacket water heater to be heated again to prevent the refrigerant A from freezing due to the low temperature and provide the heat source required for the vaporization of LNG. In the ethylene glycol solution heat exchange system, the refrigerant B absorbs the refrigerant B. The cold energy carried by refrigerant A enters the cargo hold air cooler along the pipeline under the action of the drying circulation pump. At this time, the fan blows air to the cargo hold air cooler to reduce the temperature around the cargo hold air cooler, thereby reaching the dew point temperature of the surrounding air, causing water vapor to condense. The condensed water is first collected in the condensate tank. At this time, the discharge valve is opened, and the condensed water is discharged to the overboard through the pipeline, thereby reducing the air humidity and achieving the purpose of drying the cargo hold; at this time, in the cargo hold ventilation and drying system, the exhaust valve and the air inlet valve are closed, and the return air valve is opened, and the cargo hold is no longer ventilated with the outside world.

[0017] Option 2: When the dew point temperature of the outside air detected by the outside air dew point meter is lower than the dew point temperature of the cargo hold air detected by the cargo hold air dew point meter, if the outside air humidity detected by the outside air humidity meter is greater than the air humidity in the cargo hold detected by the cargo hold air humidity meter, the cargo hold should be dried and ventilated.

[0018] At this time, in the LNG heat exchange system, the cylinder jacket water heater heats the refrigerant A, and the refrigerant A circulates under the action of the heating circulation pump. The LNG fuel is transferred from the LNG fuel tank, reaches a certain pressure through the booster pump, flows through the LNG heat exchanger, and exchanges heat with the refrigerant A. The refrigerant A absorbs the cold energy from the LNG, and then the refrigerant A flows through the cylinder jacket water heater to be heated again to prevent the refrigerant A from freezing due to the low temperature and provide the heat source required for the LNG vaporization; in the ethylene glycol solution heat exchange system, the refrigerant B absorbs the cold energy carried by the refrigerant A in the dry circulation Under the action of the ring pump, it enters the cargo hold air cooler along the pipeline. At this time, the fan blows air to the cargo hold air cooler, so that the temperature around the cargo hold air cooler 8 is reduced, thereby reaching the dew point temperature of the surrounding air, causing water vapor to condense. The condensed water is first collected in the condensate tank. At this time, the discharge valve is opened, and the condensed water is discharged to the outside through the pipeline, thereby reducing the air humidity; in the cargo hold ventilation and drying system, the exhaust valve and the air inlet valve are opened, and the return air valve is closed, and the outside air enters the cargo hold from the air inlet duct through the cargo hold air inlet. At the same time, the air in the cargo hold is discharged into the atmosphere from the return air duct through the cargo hold air outlet.

[0019] Option 3: When the dew point temperature of the outside air detected by the outside air dew point meter is lower than the dew point temperature of the cargo hold air detected by the cargo hold air dew point meter, and if both the outside air temperature and humidity meet the requirements for cargo hold drying, the cargo hold can be ventilated naturally.

[0020] At this time, in the LNG heat exchange system, the cylinder jacket water heater heats the refrigerant A, and the refrigerant A absorbs the cold energy from the LNG. Then the refrigerant A flows through the cylinder jacket water heater to be heated again to prevent the refrigerant B from freezing and provide the heat source required for the vaporization of LNG. At the same time, the dry circulation pump is turned off, and the refrigerant B and the refrigerant A no longer exchange heat. At this time, the outside air enters the cargo hold from one side of the hatch cover and is discharged from the other side of the hatch cover to achieve the purpose of natural ventilation.

[0021] Solution 4: In special circumstances, such as when the ship is at anchor for inspection, the staff needs to enter the cargo hold. Without considering the humidity and temperature of the cargo hold, in order to meet the oxygen content requirements in the cargo hold, the cargo hold must be ventilated. However, natural ventilation alone cannot quickly meet the requirements. Mechanical ventilation can be used. At this time, the return air valve is closed, and the air inlet valve and exhaust valve are opened. Under the action of the fan, the outside air enters the cargo hold from the air inlet duct through the cargo hold air inlet, and the air in the cargo hold is discharged into the atmosphere through the cargo hold air outlet through the return air duct, thereby achieving rapid ventilation of the cargo hold.

[0022] Advantages of the present invention:

[0023] 1. The system of the present invention utilizes the cold energy of LNG to cool and dehumidify the air in the cargo hold of the ship, thereby achieving the purpose of drying the cargo hold, making full use of the cold energy of LNG fuel, and reducing the consumption of heat source during the vaporization process of LNG fuel, thereby realizing the rational use of energy.

[0024] 2. The system of the present invention can quickly achieve ventilation when the cargo hold needs sufficient oxygen, solving the problem of low efficiency of traditional natural ventilation.

[0025] 3. The system of the present invention has a simple structure, is easy to install and implement, and does not require the installation of expensive dehumidification equipment. The investment cost and operating cost are very low. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a system diagram of the present invention;

[0027] Figure 2 This is a schematic diagram of the circulation in the cargo hold;

[0028] Figure 3 This is a schematic diagram of cargo hold ventilation and drying;

[0029] Figure 4 This is a schematic diagram of natural ventilation in the cargo hold.

[0030] In the attached figure: 1. Booster pump; 2. LNG heat exchanger; 3. Heating circulation pump; 4. Cylinder jacket water heater; 5. Ethylene glycol heat exchanger; 6. Drying circulation pump; 7. Fan; 8. Cargo hold air cooler; 9. Condensate tank; 10. Discharge valve; 11. Exhaust valve; 12. Return air valve; 13. Inlet valve; 14. Outside air dew point meter; 15. Outside air humidity meter; 16. Cargo hold air inlet; 17. Cargo hold air outlet; 18. Cargo hold air dew point meter; 19. Cargo hold air humidity meter; 20. Air inlet duct; 21. Return air duct; 22. Cargo hold. DETAILED DESCRIPTION

[0031] 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 and embodiments.

[0032] A cargo hold drying system for an LNG powered ship, the system mainly includes an LNG heat exchange system, an ethylene glycol solution heat exchange system, and a cargo hold ventilation and drying system. Figure 1 , Figure 2 , Figure 3 shown.

[0033] The LNG heat exchange system includes: a booster pump 1, an LNG heat exchanger 2, a heating circulation pump 3, and a cylinder jacket water heater 4.

[0034] The ethylene glycol solution heat exchange system includes: an ethylene glycol heat exchanger 5, a drying circulation pump 6, a fan 7, a cargo hold air cooler 8, a condensate tank 9, and a discharge valve 10.

[0035] The cargo hold ventilation and drying system includes: an exhaust valve 11, a return air valve 12, an air inlet valve 13, an outside air dew point meter 14, an outside air humidity meter 15, a cargo hold air inlet 16, a cargo hold air outlet 17, a cargo hold air dew point meter 18, a cargo hold air humidity meter 19, an air inlet duct 20, a return air duct 21, and a cargo hold 22.

[0036] In the LNG heat exchange system, the booster pump 1 is connected to the LNG heat exchanger 2 through a pipeline, the LNG heat exchanger 2 is connected to the cylinder jacket water heater 4 through a pipeline, and the heating circulation pump 3 is connected to the LNG heat exchanger 2 through a pipeline, wherein a high concentration of ethylene glycol solution is used as a refrigerant A to circulate in the LNG heat exchange system. Refrigerant A flows through the cylinder jacket water heater 4, and the cylinder jacket water heater 4 heats the refrigerant A. Refrigerant A circulates under the action of the heating circulation pump 3. LNG fuel is transferred out from the LNG fuel tank, reaches a certain pressure through the booster pump 1, flows through the LNG heat exchanger 2, and exchanges heat with refrigerant A. Refrigerant A absorbs the cold energy from LNG, and then refrigerant A flows through the cylinder jacket water heater 4 to be heated again to prevent the refrigerant A from freezing due to the low temperature, and provide the heat source required for LNG vaporization. In this cycle, the LNG fuel is vaporized to the required temperature of the ship's main power equipment and sent to the ship's main engine for combustion.

[0037] In the ethylene glycol solution heat exchange system, the dry circulation pump 6 is connected to the ethylene glycol heat exchanger 5 through a pipeline. Figure 1 The middle dotted area is the cargo hold heat exchange equipment, which is installed in the cargo hold 22, including a fan 7, a condensate tank 9, and a cargo hold air cooler 8. Since the ship has multiple cargo holds 22, it has multiple such heat exchange equipment. Take cargo hold No. 1 as an example for explanation. The cargo hold air cooler 8 is connected to the condensate tank 9 through a pipeline. A pipeline is arranged under the condensate tank 9, and a discharge valve 10 is arranged on the pipeline. A lower concentration of ethylene glycol solution is used as the refrigerant B. Refrigerant B and refrigerant A are exchanged with heat through the ethylene glycol heat exchanger 5. Refrigerant B absorbs the cold energy carried by refrigerant A. Under the action of the drying circulation pump 6, refrigerant B enters the cargo hold air cooler 8, and the fan 7 blows air to the cargo hold air cooler 8 to reduce the ambient temperature of the cargo hold air cooler 8, thereby reaching the dew point temperature of the surrounding air, causing water vapor to condense, reducing air humidity, and achieving the purpose of drying the cargo hold 22.

[0038] In the cargo hold ventilation and drying system, a cargo hold air inlet 16, a cargo hold air outlet 17, a cargo hold air dew point meter 18, and a cargo hold air humidity meter 19 are provided in the cargo hold 22, an outside air dew point meter 14 and an outside air humidity meter 15 are provided at the air inlet duct 20, an exhaust valve 11 is provided on the return air duct 21, an air inlet valve 13 is provided on the air inlet duct 20, and a return air valve 12 is provided at the connection between the air inlet duct 20 and the return air duct 21.

[0039] The present invention proposes the following scheme:

[0040] Solution 1: When the dew point temperature of the outside air detected by the outside air dew point meter 14 is higher than the dew point temperature of the cargo hold air detected by the cargo hold air dew point meter 18, natural ventilation is no longer performed, and only the cold energy of LNG is used to cool and dehumidify the air in the cargo hold.

[0041] In the LNG heat exchange system, the cylinder jacket water heater 4 heats the refrigerant A, and the refrigerant A circulates under the action of the heating circulation pump 3. The LNG fuel is transferred from the LNG fuel tank, reaches a certain pressure through the booster pump 1, flows through the LNG heat exchanger 2, and exchanges heat with the refrigerant A. The refrigerant A absorbs the cold energy from the LNG, and then the refrigerant A flows through the cylinder jacket water heater 4 to be heated again to prevent the refrigerant A from freezing due to the low temperature and provide the heat source required for the vaporization of LNG. In the ethylene glycol solution heat exchange system, the refrigerant B The cold energy carried by the absorption refrigerant A enters the cargo hold air cooler 8 along the pipeline under the action of the drying circulation pump 6. At this time, the fan 7 blows air to the cargo hold air cooler 8 to reduce the temperature around the cargo hold air cooler 8, thereby reaching the dew point temperature of the surrounding air, causing water vapor to condense. The condensed water is first collected in the condensate tank 9. At this time, the discharge valve 10 is opened, and the condensed water is discharged to the overboard through the pipeline, thereby reducing the air humidity and achieving the purpose of drying the cargo hold; at this time, in the cargo hold ventilation and drying system, the exhaust valve 11 and the air inlet valve 13 are closed, and the return air valve 12 is opened. Figure 2 As shown, the cargo hold is no longer ventilated to the outside.

[0042] Solution 2: When the dew point temperature of the outside air detected by the outside air dew point meter 14 is lower than the dew point temperature of the cargo hold air detected by the cargo hold air dew point meter 18, if the outside air humidity detected by the outside air humidity meter 15 is greater than the air humidity in the cargo hold detected by the cargo hold air humidity meter 19, the cargo hold 22 must be dried and ventilated.

[0043] At this time, in the LNG heat exchange system, the cylinder jacket water heater 4 heats the refrigerant A, and the refrigerant A circulates under the action of the heating circulation pump 3. The LNG fuel is transferred from the LNG fuel tank, reaches a certain pressure through the booster pump 1, flows through the LNG heat exchanger 2, and exchanges heat with the refrigerant A. The refrigerant A absorbs the cold energy from the LNG, and then the refrigerant A flows through the cylinder jacket water heater 4 to be heated again to prevent the refrigerant A from freezing due to the low temperature and provide the heat source required for the vaporization of LNG; in the ethylene glycol solution heat exchange In the system, refrigerant B absorbs the cold energy carried by refrigerant A and enters cargo hold air cooler 8 along the pipeline under the action of drying circulation pump 6. At this time, fan 7 blows air to cargo hold air cooler 8 to reduce the temperature around cargo hold air cooler 8, thereby reaching the dew point temperature of the surrounding air, causing water vapor to condense. The condensed water is first collected in the condensate tank 9. At this time, the discharge valve 10 is opened, and the condensed water is discharged to the outside through the pipeline, thereby reducing the air humidity. In the cargo hold ventilation and drying system, the exhaust valve 11 and the air inlet valve 13 are opened, and the return air valve 12 is closed. Figure 3 As shown, outside air enters the cargo hold 22 from the air inlet duct 20 through the cargo hold air inlet 16 via the air inlet valve 13. At the same time, the air in the cargo hold 22 passes through the cargo hold air outlet 17, from the return air duct 21, and through the exhaust valve 11 to the atmosphere.

[0044] Solution three: When the dew point temperature of the outside air detected by the outside air dew point meter 14 is lower than the dew point temperature of the cargo hold air detected by the cargo hold air dew point meter 18, if the outside air temperature and humidity meet the requirements for cargo hold drying, the cargo hold can be naturally ventilated only.

[0045] At this time, the dry circulation pump 6 is turned off, which can save the electric energy consumed by the dry circulation pump. The refrigerant B and the refrigerant A no longer exchange heat. In the LNG heat exchange system, the cylinder jacket water heater 4 heats the refrigerant A, and the refrigerant A absorbs the cold energy from the LNG. Then the refrigerant A flows through the cylinder jacket water heater 4 to be heated again. At this time, the flow rate of the cylinder jacket water flowing through the cylinder jacket water heater 4 should be increased to prevent the refrigerant A from freezing and provide sufficient heat source for LNG vaporization. Figure 4 This is a natural ventilation diagram. The natural ventilation inlet and natural ventilation outlet are respectively arranged on both sides of the hatch cover. During natural ventilation, the natural ventilation inlet and natural ventilation outlet are opened. The left and right sides of the figure do not represent the left and right sides of the ship's side. Figure 4 It can be seen as a schematic diagram looking from the bow to the stern, or it can be seen as looking from the stern to the bow, which is only to indicate that the natural ventilation inlet and the natural ventilation outlet are not on the same side. At this time, the outside air enters the cargo hold from one side of the hatch cover and is discharged from the other side of the hatch cover, achieving the purpose of natural ventilation.

[0046] Solution 4: In special circumstances, such as when the ship is at anchor for inspection, the staff needs to enter the cargo hold 22. Without considering the humidity and temperature of the cargo hold 22, in order to meet the oxygen content requirement in the cargo hold 22, the cargo hold 22 must be ventilated. However, natural ventilation alone cannot quickly meet the requirement. Mechanical ventilation can be used. At this time, the return air valve 12 is closed, and the air inlet valve 13 and the exhaust valve 11 are opened. Under the action of the fan 7, the outside air enters the cargo hold 22 from the air inlet duct 20 through the cargo hold air inlet 16 through the air inlet valve 13. The air in the cargo hold 22 passes through the cargo hold air outlet 17, from the return air duct 21, and through the exhaust valve 11 to the atmosphere. In this way, the cargo hold 22 can be ventilated quickly to meet the oxygen concentration requirement in the cargo hold 22 as soon as possible.

[0047] The above is only a preferred embodiment of the present invention. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A cargo hold drying system for an LNG powered ship, characterized in that :The system includes LNG heat exchange system, ethylene glycol solution heat exchange system, and cargo hold ventilation and drying system; The LNG heat exchange system includes: a booster pump (1), an LNG heat exchanger (2), a heating circulation pump (3), and a cylinder jacket water heater (4): The ethylene glycol solution heat exchange system comprises: an ethylene glycol heat exchanger (5), a drying circulation pump (6), a fan (7), a cargo hold air cooler (8), a condensate tank (9), and a discharge valve (10); The cargo hold ventilation and drying system comprises: an exhaust valve (11), a return air valve (12), an inlet valve (13), an outside air dew point meter (14), an outside air humidity meter (15), a cargo hold air inlet (16), a cargo hold air outlet (17), a cargo hold air dew point meter (18), a cargo hold air humidity meter (19), an air inlet duct (20), a return air duct (21), and a cargo hold (22); the cargo hold air inlet (16), the cargo hold air outlet (17), the cargo hold air dew point meter (18), and the cargo hold air humidity meter (19) are arranged in the cargo hold (22); In the cargo hold ventilation system, the air inlet duct (20) is provided with an outside air dew point meter (14) and an outside air humidity meter (15), the return air duct (21) is provided with an exhaust valve (11), the air inlet duct (20) is provided with an air inlet valve (13), and a return air valve (12) is provided at the connection between the air inlet duct (20) and the return air duct (21); The drying circulation pump (6) is connected to the ethylene glycol heat exchanger (5) through a pipeline; The cargo hold air cooler (8) is connected to the condensate tank (9) via a pipeline, a pipeline is arranged below the condensate tank (9), and a discharge valve (10) is arranged on the pipeline; In the LNG heat exchange system, the booster pump (1) is connected to the LNG heat exchanger (2) through a pipeline, the LNG heat exchanger (2) is connected to the cylinder jacket water heater (4) through a pipeline, and the heating circulation pump (3) is connected to the LNG heat exchanger (2) through a pipeline.

2. A method for drying a cargo hold of an LNG powered ship, using a cargo hold drying system of an LNG powered ship according to claim 1, characterized in that When the dew point temperature of the outside air detected by the outside air dew point meter (14) is lower than the dew point temperature of the cargo hold air detected by the cargo hold air dew point meter (18), but the outside air humidity detected by the outside air humidity meter (15) is greater than the air humidity in the cargo hold detected by the cargo hold air humidity meter (19), the cargo hold (22) needs to be dried and ventilated. At this time, in the LNG heat exchange system, the cylinder jacket water heater (4) heats the refrigerant 1, and the refrigerant 1 circulates under the action of the heating circulation pump (3). The LNG fuel flows through the LNG heat exchanger (2) and exchanges heat with the refrigerant 1. The refrigerant 1 absorbs the cold energy from the LNG. Then the refrigerant 1 flows through the cylinder jacket water heater (4) and is heated again. In the ethylene glycol solution heat exchange In the system, the refrigerant 2 absorbs the cold energy carried by the refrigerant 1 and enters the cargo hold air cooler (8) along the pipeline under the action of the drying circulation pump (6). At this time, the fan (7) blows air to the cargo hold air cooler (8) to reduce the temperature around the cargo hold air cooler (8), thereby reaching the dew point temperature of the surrounding air, causing water vapor to condense and reduce the air humidity. In the cargo hold ventilation and drying system, the exhaust valve (11) and the air inlet valve (13) are opened, and the return air valve (12) is closed. The outside air enters the cargo hold (22) from the air inlet duct (20) through the cargo hold air inlet (16) through the air inlet valve (13). At the same time, the air in the cargo hold (22) is discharged into the atmosphere from the return air duct (21) through the exhaust valve (11) through the cargo hold air outlet (17).

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