System and method for preventing liquid accumulation at the bottom of a cryogenic liquid tank, and ship

Abstract

The present invention relates to the technical field of liquefied gas storage and transportation equipment. Specifically, it relates to a system and method for preventing liquid accumulation at the bottom of a cryogenic liquid tank, and a ship, including a cryogenic liquid tank, a gas phase pipe, a liquid phase pipe, a drainage pump, a connecting pipe, and a ventilation system; the internal space of the cryogenic liquid tank is a cabin, a pump well is arranged at the bottom of the cabin, a drainage pump is arranged in the pump well, a drainage pipe is arranged at the drainage port of the drainage pump, the drainage pipe leads to the outside of the cabin, and a drainage control valve is arranged on the drainage pipe; the liquid phase pipe includes a liquid phase main pipe and a pump well purging branch pipe, the liquid phase main pipe includes a front section pipe and a rear section pipe, and the gas phase pipe includes a gas phase main pipe, a first gas phase branch pipe, and a second gas phase branch pipe; it can solve the problem of liquid nitrogen accumulation in the pump well during the cold tank stage before the filling operation of a large cryogenic liquid tank, solve the problem that the liquid accumulation at the bottom of the liquid tank and in the pump well cannot be completely pumped out during the operation of clearing the liquid stored in the liquid tank, and solve the problem that the liquid accumulation in the pump well is not easily dried during the drying treatment of the inside of the liquid tank.

Description

Technical Field

[0001] The present invention relates to the technical field of liquefied gas storage and transportation equipment, and in particular, to a system and method for preventing liquid accumulation at the bottom of a cryogenic liquid tank, and a ship. Background Art

[0002] In recent years, driven by the need to protect the environment and meet regulatory requirements globally, the demand for clean energy has been continuously expanding worldwide. According to the International Convention for the Prevention of Pollution from Ships (MARPOL Annex VI - Regulations for the Prevention of Air Pollution from Ships), all ships passing through emission control areas must meet the emission requirements for sulfur oxides and nitrogen oxides, which will greatly stimulate the market demand for dual-fuel power ships using cryogenic liquid fuels such as LNG or methanol, LPG, LEG, and traditional fuel oils (LNG is natural liquefied gas). In addition, due to the significant increase in the demand for replacing oil, coal, etc. with LNG on land, this has also triggered a large demand for LNG carriers, etc.

[0003] As the main carrier for cryogenic liquefied gas storage, the suction port of the cryogenic pump used to pressurize and discharge cryogenic liquids such as LNG is installed in the pump well. Different from the external type of the pump well of small liquid tanks, the pump well of large liquid tanks is usually installed at the bottom of the liquid tank. The upper part of the pump well is provided with a mounting plate for cryogenic submersible pumps / deep well pumps, and the lower part protrudes from the bottom of the liquid tank, becoming the lowest point of the liquid tank, and is covered with thermal insulation materials for heat preservation.

[0004] Currently, before the first filling of a cryogenic liquid tank, generally liquid nitrogen is used to dry, inertize, and cool the tank body, and then LNG is used for replacement and filling.

[0005] During the tank cooling stage, due to the great difficulty of the top spraying operation, it is easy for the sprayed liquid nitrogen to directly fall on the bottom of the cabin before being completely vaporized and gather around the pump well. At this time, the liquid nitrogen (-196°C) directly contacts the bottom plate of the cabin, and the temperature of the bottom plate drops rapidly, while the temperature of other areas is relatively high. Such a large temperature difference is likely to cause excessive internal structural stress in the cabin wall of the liquid tank and cannot be effectively released, resulting in the insulation of the liquid tank being ruptured, and seriously affecting the normal use and lifespan of the liquid tank.

[0006] In addition, during the tank cleaning operation, due to the installation position limitation of the cryogenic pump, there is always some accumulated liquid that cannot be pumped out and needs to wait for natural vaporization, which takes a long time. If, due to improper operation, liquid nitrogen directly drips on the bottom of the liquid tank and finally gathers in and around the pump well, liquid accumulation will be formed.

[0007] During the drying stage, when nitrogen is used to dry the liquid tank, since the pump well is at the lowest point and is a closed small space, it is difficult for the drying nitrogen to reach, and the moisture in the pump well is not easily displaced. Moreover, if the dew point at the bottom has been difficult to meet the standard (lower than -40°), the main reason is the problem of liquid accumulation in the pump well. Summary of the Invention

[0008] The object of the present invention is to provide a system for preventing liquid accumulation at the bottom of a cryogenic liquid tank, which can solve the influence of liquid nitrogen accumulation in the pump well during the cold tank stage before the filling operation of a large cryogenic liquid tank, solve the problem that the liquid accumulation at the bottom of the liquid tank and in the pump well cannot be completely pumped out during the operation of removing the stored liquid in the liquid tank, and can solve the problem that the liquid accumulation in the pump well is not easily dried during the drying process of the inside of the liquid tank.

[0009] Another object of the present invention is to provide a method for preventing liquid accumulation at the bottom of a cryogenic liquid tank, which can solve the influence of liquid nitrogen accumulation in the pump well during the cold tank stage before the filling operation of a large cryogenic liquid tank, solve the problem that the liquid accumulation at the bottom of the liquid tank and in the pump well cannot be completely pumped out during the operation of removing the stored liquid in the liquid tank, and can solve the problem that the liquid accumulation in the pump well is not easily dried during the drying process of the inside of the liquid tank.

[0010] The technical solution of the present invention is realized as follows:

[0011] A system for preventing liquid accumulation at the bottom of a cryogenic liquid tank includes a cryogenic liquid tank, a vapor pipe, a liquid pipe, a drain pump, and a connecting pipe;

[0012] The internal space of the cryogenic liquid tank is a chamber, a pump well is arranged at the bottom of the chamber, the drain pump is arranged in the pump well, the suction port of the drain pump leads to the bottom inside the pump well, a drain pipe is arranged at the discharge port of the drain pump, the drain pipe leads to the outside of the chamber, and a drain control valve is arranged on the drain pipe;

[0013] The liquid pipe includes a liquid main pipe and a pump well purge branch pipe. The inlet of the pump well purge branch pipe is communicated with the liquid main pipe, the outlet of the pump well purge branch pipe leads to the bottom of the pump well, and the outlet of the pump well purge branch pipe is located below the suction port of the drain pump. A purge control valve is arranged on the pump well purge branch pipe;

[0014] The liquid main pipe includes a front section pipe and a rear section pipe which are connected in series. A liquid main valve is arranged on the front section pipe. One end of the connecting pipe is communicated with the drain pipe, and the other end is communicated with the rear section pipe. A connection control valve is arranged on the connecting pipe;

[0015] The gas phase pipe includes a main gas phase pipe, a first gas phase branch pipe, and a second gas phase branch pipe. The inlet ends of the first gas phase branch pipe and the second gas phase branch pipe are both connected to the main gas phase pipe. The first gas phase branch pipe leads to the top of the cabin, and a first control valve is provided on the first gas phase branch pipe. The outlet end of the second gas phase branch pipe is connected to the rear section pipe, and a second control valve is provided on the second gas phase branch pipe;

[0016] It further includes a ventilation system capable of ventilating the inside of the cabin to the outside. The liquid phase pipe is also connected to the ventilation system through a pipeline, and a third control valve capable of controlling the opening and closing of the ventilation system is provided on the pipeline.

[0017] Further, the liquid phase pipe further includes a spray branch pipe. The outlet of the main liquid phase pipe is also connected to the inlet of the spray branch pipe. The outlet of the spray branch pipe leads to the top of the cabin, and a spray control valve is provided on the spray branch pipe.

[0018] Further, it further includes a top spray pipe. The outlet of the spray branch pipe is connected to the inlet of the top spray pipe. The top spray pipe is horizontally arranged at the top of the cabin, and a plurality of spray heads are provided on the top spray pipe.

[0019] Further, the liquid phase pipe further includes an injection branch pipe. The outlet of the main liquid phase pipe is also connected to the inlet of the injection branch pipe. The outlet of the injection branch pipe leads to the bottom of the cabin, and an injection control valve is provided on the injection branch pipe.

[0020] Further, it further includes a bottom injection pipe. The outlet of the injection branch pipe is connected to the inlet of the bottom injection pipe. The bottom injection pipe is horizontally arranged at the bottom of the cabin, and a plurality of injection ports are provided on the bottom injection pipe.

[0021] Further, an adiabatic insulation layer is provided on the outer wall of the cryogenic liquid tank.

[0022] This application also provides a method for preventing liquid accumulation at the bottom of the cryogenic liquid tank. The method is realized by the system for preventing liquid accumulation at the bottom of the cryogenic liquid tank. The method is an evaporation elimination method, including the following steps:

[0023] S11: Close all valves in the system;

[0024] S12: Open the second control valve and the purge control valve;

[0025] S13: Introduce dry gas into the gas phase pipe;

[0026] S14: The dry gas passes through the pump well purge branch pipe and leads to the bottom of the pump well to purge the accumulated liquid.

[0027] The present application also provides a method for preventing liquid accumulation at the bottom of a cryogenic liquid tank. The method is implemented through the system for preventing liquid accumulation at the bottom of a cryogenic liquid tank, and the method is a pressure gasification method, including the following steps:

[0028] S21: Close all valves in the system;

[0029] S22: Open the purge control valve and the third control valve;

[0030] S23: Under the action of the gas pressure in the chamber, continuously push out the accumulated liquid at the bottom of the chamber in the reverse direction from the pump well and the bottom of the chamber;

[0031] S24: And gasify the accumulated liquid at the bottom of the chamber through the ventilation system.

[0032] The present application also provides a method for preventing liquid accumulation at the bottom of a cryogenic liquid tank. The method is implemented through the system for preventing liquid accumulation at the bottom of a cryogenic liquid tank, and the method is a pressure discharge method, including the following steps:

[0033] S31: Close all valves in the system;

[0034] S32: Open the purge control valve and the connection control valve;

[0035] S33: Under the action of the gas pressure in the chamber, continuously push out the accumulated liquid at the bottom of the chamber in the reverse direction from the pump well and the bottom of the chamber, and discharge it through the drain pipe.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] The present invention can, during the cold tank stage before the cryogenic liquid tank filling operation, by only opening the second control valve and the purge control valve, introduce dry gas into the gas phase pipe, and then lead it to the bottom of the pump well through the pump well purge pipe to accelerate the evaporation of the accumulated liquid by purging and eliminate the accumulated liquid; or during the tank cleaning operation, by only opening the purge control valve and the third control valve, under the action of the gas pressure in the chamber, continuously push out the accumulated liquid at the bottom of the chamber in the reverse direction from the pump well and the bottom of the chamber, and gasify and release the accumulated liquid at the bottom of the chamber through the ventilation system; or during the drying stage, by only opening the purge control valve and the connection control valve, under the action of the gas pressure in the chamber, continuously push out the accumulated liquid at the bottom of the chamber in the reverse direction from the pump well and the bottom of the chamber, and discharge it through the drain pipe, finally draining the accumulated liquid at the bottom of the chamber completely. Therefore, the present application can solve the problem of liquid nitrogen accumulation in the pump well during the cold tank stage before the filling operation, solve the problem that the accumulated liquid at the bottom of the liquid tank and in the pump well cannot be completely pumped out during the operation of clearing the liquid in the liquid tank, and solve the problem that the accumulated liquid in the pump well is not easily dried during the drying process of the inside of the liquid tank. Description of the Drawings

[0038] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0039] Figure 1 It is a schematic diagram of the overall structure of the system for preventing liquid accumulation at the bottom of a low-temperature liquid tank in the present invention.

[0040] In the figure: (Explanation of reference numerals)

[0041] 1 - Low-temperature liquid tank; 2 - Gas-phase pipe; 201 - Gas-phase main pipe; 202 - First gas-phase branch pipe; 203 - Second gas-phase branch pipe; 204 - First control valve; 205 - Second control valve;

[0042] 3 - Liquid-phase pipe; 3011 - Front-section pipe; 3012 - Rear-section pipe; 302 - Pump well purge branch pipe; 303 - Purge control valve; 304 - Liquid-phase main valve; 305 - Injection branch pipe; 306 - Injection control valve; 307 - Spray branch pipe; 308 - Spray control valve;

[0043] 4 - Drainage pump; 401 - Drainage pipe; 402 - Drainage control valve;

[0044] 5 - Connecting pipe; 501 - Connecting control valve;

[0045] 6 - Pump well; 8 - Top spray pipe; 801 - Spray head;

[0046] 9 - Bottom injection pipe; 901 - Injection port; 10 - Thermal insulation layer. Detailed implementation manners

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0048] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0049] It should be noted that like reference numerals and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0050] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present invention is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0051] In addition, terms such as "horizontal", "vertical", "hanging" do not mean that the components are required to be absolutely horizontal or hanging, but may be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but may be slightly inclined.

[0052] In the description of the present invention, it should also be noted that unless otherwise clearly specified and defined, the terms "set", "installed", "connected", "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] The following will describe in detail some embodiments of the present invention with reference to the drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0054] Embodiment 1

[0055] Refer to Figure 1 , this embodiment provides a technical solution as follows:

[0056] This embodiment provides a system for preventing liquid accumulation at the bottom of a cryogenic liquid tank, including a cryogenic liquid tank 1, a gas phase pipe 2, a liquid phase pipe 3, a drainage pump 4, and a connecting pipe 5. The type of the cryogenic liquid tank is a large cryogenic liquid tank (as mentioned in the background art).

[0057] The internal space of the cryogenic liquid tank 1 is a chamber. A pump well 6 is provided at the bottom of the chamber. The drain pump 4 is arranged in the pump well 6. The suction port of the drain pump 4 leads to the bottom inside the pump well 6. A drain pipe 401 is provided at the discharge port of the drain pump 4. The drain pipe 401 leads to the outside of the chamber, and a drain control valve 402 is provided on the drain pipe 401.

[0058] An installation seat plate is arranged at the upper part of the pump well 6. The drain pump 4 is installed on the installation seat plate. The bottom of the pump well 6 protrudes from the bottom of the liquid tank, becoming the lowest point of the liquid tank. The outer wall of the cryogenic liquid tank 1 is coated with a heat-insulating layer 10 for heat preservation.

[0059] It should be noted that the number of drain pumps 4 is at least one, and can also be set to two or more. And the number of drain pipes 401 corresponds to the number of drain pumps 4 one by one. A drain pipe 401 is provided at the outlet end of each drain pump 4. The preferred embodiment of this application is to set the drain pumps 4 to two. In addition, a drain main pipe is also provided. The outlet ends of the two drain pipes 401 provided on the two drain pumps 4 are both communicated with the inlet end of the drain main pipe. The two drain pipes 401 are equivalent to two drain branch pipes, and finally converge on the drain main pipe and are discharged.

[0060] The liquid phase pipe 3 includes a liquid phase main pipe and a pump well purging branch pipe 302. The pump well purging branch pipe 302 leads to the pump well 6 inside the chamber for purging the inside of the pump well 6. The outlet of the liquid phase main pipe is communicated with the inlet of the pump well purging branch pipe 302. The outlet of the pump well purging branch pipe 302 leads to the bottom of the pump well 6, and the outlet of the pump well purging branch pipe 302 is located below the drain pump 4. A purging control valve 303 is provided on the pump well purging branch pipe 302.

[0061] The liquid phase main pipe includes a front section pipe 3011 and a rear section pipe 3012 that are connected in the front and rear. The front section pipe 3011 is the front part of the liquid phase main pipe, and the rear section pipe 3012 is the rear part of the liquid phase main pipe. The fluid in the liquid phase main pipe first flows into the front section pipe 3011 and then into the rear section pipe 3012.

[0062] A liquid phase main valve 304 is provided on the front section pipe 3011. It should be noted here that when both the drain pump 4 and the drain pipe 401 are set to one, one end of the connecting pipe 5 is directly communicated with the drain pipe 401 and the other end is communicated with the rear section pipe 3012. In this embodiment, the number of drain pumps 4 and drain pipes 401 is preferably set to two. Therefore, one end of the connecting pipe 5 is communicated with the drain main pipe and the other end is communicated with the rear section pipe 3012. And a connection control valve 501 is provided on the connecting pipe 5. The connection control valve 501 can control the connection between the drain main pipe and the liquid phase pipe 3.

[0063] In a preferred embodiment of the present embodiment, the liquid phase pipe 3 further includes a spray branch pipe 307. The outlet of the liquid phase main pipe is also communicated with the inlet of the spray branch pipe 307. The outlet of the spray branch pipe 307 leads to the top of the cabin. A spray control valve 308 is provided on the spray branch pipe 307. By branching from the liquid phase main pipe to the spray branch pipe 307, the spray branch pipe 307 can spray the inside of the cabin at the top of the cabin.

[0064] More preferably, a top spray pipe 8 is also provided. The outlet of the spray branch pipe 307 is communicated with the inlet of the top spray pipe 8. The top spray pipe 8 is horizontally arranged at the top of the cabin. A plurality of spray heads 801 are provided on the top spray pipe 8. When implementing top spraying, the spraying area is enlarged through the plurality of spray heads 801 to improve the spraying effect.

[0065] In a preferred embodiment of the present embodiment, the liquid phase pipe 3 further includes an injection branch pipe 305. The outlet of the liquid phase main pipe is also communicated with the inlet of the injection branch pipe 305. The outlet of the injection branch pipe 305 leads to the bottom of the cabin. An injection control valve 306 is provided on the injection branch pipe 305. By branching from the liquid phase main pipe to the injection branch pipe 305, the injection branch pipe 305 can inject the bottom of the cabin.

[0066] More preferably, a bottom injection pipe 9 is also provided. The outlet of the injection branch pipe 305 is communicated with the inlet of the bottom injection pipe 9. The bottom injection pipe 9 is horizontally arranged at the bottom of the cabin. A plurality of injection ports 901 are provided on the bottom injection pipe 9. When implementing bottom injection, the injection area can be enlarged through the plurality of injection ports for uniform injection, thereby improving the injection efficiency.

[0067] The gas phase pipe 2 includes a gas phase main pipe 201, a first gas phase branch pipe 202 and a second gas phase branch pipe 203. The outlet end of the gas phase main pipe 201 is communicated with the inlet end of the first gas phase branch pipe 202 and the inlet end of the second gas phase branch pipe 203. The first gas phase branch pipe 202 leads to the top of the cabin. A first control valve 204 is provided on the first gas phase branch pipe 202. The outlet end of the second gas phase branch pipe 203 is communicated with the rear section pipe 3012. A second control valve 205 is provided on the second gas phase branch pipe 203. The second control valve 205 can control the connection between the gas phase pipe 2 and the liquid phase pipe 3.

[0068] The system for preventing liquid accumulation at the bottom of the cryogenic liquid tank further includes a ventilation system. The ventilation system can ventilate the inside of the cabin to the outside of the cabin. The liquid phase pipe 3 is also communicated with the ventilation system through a pipeline. And a third control valve capable of controlling the opening and closing of the ventilation system is provided on the pipeline (the ventilation system and the third control valve are not marked in the figure and belong to the prior art, so they will not be elaborated here).

[0069] It should be noted that the system for preventing liquid accumulation at the bottom of the cryogenic liquid tank in this application further includes a control system. All valves in the system for preventing liquid accumulation at the bottom of the cryogenic liquid tank in this application (all valves in the system: for example, the first control valve 204, the second control valve 205, the third control valve, the purge control valve 303, the liquid phase main valve 304, the injection control valve 306, the spray control valve 308, the liquid discharge control valve 402, the connection control valve 501) can be automatically controlled through this control system.

[0070] When the system for preventing liquid accumulation at the bottom of the cryogenic liquid tank in this application is actually applied, the following situations exist:

[0071] 1. During the cold tank stage before the filling operation of the cryogenic liquid tank, if due to improper operation, liquid nitrogen directly drips onto the bottom of the liquid tank and finally accumulates in and around the pump well 6, at this time, stop the cold tank operation, close the valves leading to the cabin, open the purge control valve 303 and the third control valve. At the same time, the first control valve 204 can also be in the open state or not. Under the action of the gas pressure in the cabin (at this time, the air pressure in the cabin is generally above 1.0 bar), the accumulated liquid at the bottom of the cabin is continuously pushed out of the pump well 6 and the bottom of the cabin in the reverse direction, and the accumulated liquid at the bottom of the cabin is vaporized and released through the ventilation system. Finally, the accumulated liquid at the bottom of the cabin can be drained completely.

[0072] 2. When drying the liquid tank, if the dew point at the bottom has been difficult to meet the standard (lower than -40°), the main reason is that there is accumulated liquid in the pump well 6. Close the valves leading to the cabin, and the second control valve 205 and the purge control valve 303 can be opened. Inject the drying gas (preferably nitrogen) into the bottom of the pump well 6 through the pump well purge branch pipe 302 to purge the accumulated liquid at the bottom and accelerate evaporation, so as to effectively eliminate the accumulated liquid.

[0073] 3. When performing the tank cleaning operation on the liquid tank, when part of the liquid cannot be sucked by the liquid discharge pump 4 and cannot be discharged due to the installation height of the liquid discharge pump 4, and there is accumulated liquid, the liquid discharge pump 4 can also be stopped and the liquid discharge control valve 402 can be closed. Then, the purge control valve 303 on the pump well purge branch pipe 302 and the connection control valve 501 between the liquid phase pipe 3 and the liquid discharge main pipe can be opened. Utilize the gas pressure inside the liquid tank to continuously push the accumulated liquid out of the pump well 6 and the bottom of the liquid tank in the reverse direction, and discharge it through the liquid discharge pipe 401 and the liquid discharge main pipe. Finally, the accumulated liquid at the bottom can be drained completely.

[0074] Embodiment 2

[0075] Refer to Figure 1, this embodiment provides a method for preventing liquid accumulation at the bottom of a cryogenic liquid tank. This method is implemented through the system for preventing liquid accumulation at the bottom of the cryogenic liquid tank. This method mainly aims at the problem that when drying the liquid tank, there is liquid accumulation at the bottom of the chamber, making it difficult to meet the dew point standard all the time. This method is the evaporation elimination method, including the following steps:

[0076] S11: Close all valves in the system;

[0077] S12: Open the second control valve 205 and the purge control valve 303;

[0078] S13: Introduce dry gas into the gas phase pipe 2;

[0079] S14: The dry gas passes through the pump well purge branch pipe 302 and leads to the bottom of the pump well 6 to purge the liquid accumulation.

[0080] Embodiment 3

[0081] Refer to Figure 1 , this embodiment provides a method for preventing liquid accumulation at the bottom of a cryogenic liquid tank. This method is implemented through the system for preventing liquid accumulation at the bottom of the cryogenic liquid tank. This method aims at the cold tank stage before the cryogenic liquid tank filling operation. If due to improper operation, liquid nitrogen directly drips onto the bottom of the liquid tank to form liquid accumulation. This method is the pressure gasification method, including the following steps:

[0082] S21: Close all valves in the system;

[0083] S22: Open the purge control valve 303 and the third control valve;

[0084] S23: Under the action of the gas pressure in the chamber, continuously push the liquid accumulation at the bottom of the chamber out of the pump well 6 and the bottom of the chamber in the reverse direction;

[0085] S24: And gasify and release the liquid accumulation at the bottom of the chamber through the ventilation system.

[0086] Embodiment 4

[0087] Refer to Figure 1 , this embodiment provides a method for preventing liquid accumulation at the bottom of a cryogenic liquid tank. This method is implemented through the system for preventing liquid accumulation at the bottom of the cryogenic liquid tank. This method aims at the situation when cleaning the liquid tank. Due to the installation height of the drain pump 4, part of the liquid cannot be sucked by the drain pump 4 and there is liquid accumulation when it cannot be discharged. This method is the pressure discharge method, including the following steps:

[0088] S31: Close all valves in the system;

[0089] S32: Open the purge control valve 303 and the connection control valve 501;

[0090] S33: Under the action of the gas pressure in the cabin, the accumulated liquid at the bottom of the cabin is continuously pushed out of the pump well 6 and the bottom of the cabin in the reverse direction and discharged through the liquid discharge pipe 401;

[0091] The effects brought by the methods in the above Embodiments 2, 3 and 4 are as follows:

[0092] 1. By adding the pump well purge branch pipe 302, the problem that liquid nitrogen accumulates in the pump well when pre-cooling the liquid tank before filling is solved, which causes local stress in the bottom of the liquid tank due to too rapid temperature drop, resulting in large internal stress in the tank wall, ultimately leading to the rupture of the outer wall insulation and affecting the structural strength and service life of the liquid tank.

[0093] 2. When performing the operation of removing the stored liquid in the liquid tank, through the added pump well purge branch pipe 302, the accumulated liquid at the bottom of the liquid tank and in the pump well can be discharged from the liquid tank as much as possible. Otherwise, one can only wait for these cryogenic liquids to vaporize and then blow them out of the liquid tank with inert gas, which is both time-consuming and energy-consuming. In addition, the method adopted can directly use the pressure in the tank to discharge the cryogenic liquid in the reverse direction from the liquid tank without the need for an external power source, and the solution is simple, feasible and energy-saving.

[0094] 3. At the same time, it is also beneficial to improve the drying efficiency of the liquid tank and shorten the drying and inerting time of the liquid tank when initially drying the liquid tank.

[0095] Embodiment 5

[0096] This embodiment provides a ship safety system, including the system for preventing liquid accumulation at the bottom of the cryogenic liquid tank described in Embodiment 1, which can solve the influence of liquid nitrogen accumulation in the pump well during the cold tank stage before the filling operation of the large cryogenic liquid tank, solve the problem that the accumulated liquid at the bottom of the liquid tank and in the pump well cannot be completely pumped out during the operation of removing the stored liquid in the liquid tank, and can solve the problem that the accumulated liquid in the pump well is not easily dried when drying the inside of the liquid tank.

[0097] Embodiment 6

[0098] This embodiment provides a ship, including the ship safety system described in Embodiment 3. The ship is a dual-fuel powered ship or a transport ship, which can solve the influence of liquid nitrogen accumulation in the pump well during the cold tank stage before the filling operation of the large cryogenic liquid tank, solve the problem that the accumulated liquid at the bottom of the liquid tank and in the pump well cannot be completely pumped out during the operation of removing the stored liquid in the liquid tank, and can solve the problem that the accumulated liquid in the pump well is not easily dried when drying the inside of the liquid tank.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

[0100] In addition, those skilled in the art can understand that although some of the embodiments herein include certain features included in other embodiments but not other features, the combination of the features of different embodiments means that it is within the scope of the present invention and forms different embodiments. For example, in the claims above, any one of the claimed embodiments can be used in any combination. The information disclosed in this background art section is only intended to deepen the understanding of the overall background art of the present invention, and should not be regarded as an admission or any form of suggestion that this information constitutes the prior art known to those skilled in the art.

[0101] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

[0102] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A system for preventing liquid accumulation at the bottom of a cryogenic liquid tank, characterized in that, It includes a cryogenic liquid tank (1), a vapor pipe (2), a liquid pipe (3), a drain pump (4) and a connecting pipe (5); The internal space of the cryogenic liquid tank (1) is a compartment, and a pump well (6) is arranged at the bottom of the compartment. The drain pump (4) is arranged in the pump well (6). The suction port of the drain pump (4) leads to the inner bottom of the pump well (6). A drain pipe (401) is arranged at the discharge port of the drain pump (4). The drain pipe (401) leads to the outside of the compartment, and a drain control valve (402) is arranged on the drain pipe (401); The liquid pipe (3) includes a liquid main pipe and a pump well purging branch pipe (302). The inlet of the pump well purging branch pipe (302) is communicated with the liquid main pipe. The outlet of the pump well purging branch pipe (302) leads to the bottom of the pump well (6), and the outlet of the pump well purging branch pipe (302) is located below the suction port of the drain pump (4). A purging control valve (303) is arranged on the pump well purging branch pipe (302); The liquid main pipe includes a front section pipe (3011) and a rear section pipe (3012) which are connected in the front and back. A liquid main valve (304) is arranged on the front section pipe (3011). One end of the connecting pipe (5) is communicated with the drain pipe (401), and the other end is communicated with the rear section pipe (3012). A communication control valve (501) is arranged on the connecting pipe (5); The vapor pipe (2) includes a vapor main pipe (201), a first vapor branch pipe (202) and a second vapor branch pipe (203). The inlet ends of the first vapor branch pipe (202) and the second vapor branch pipe (203) are both communicated with the vapor main pipe (201). The first vapor branch pipe (202) leads to the top of the compartment. A first control valve (204) is arranged on the first vapor branch pipe (202). The outlet end of the second vapor branch pipe (203) is communicated with the rear section pipe (3012). A second control valve (205) is arranged on the second vapor branch pipe (203); It further includes a ventilation system capable of ventilating the inside of the compartment to the outside. The liquid pipe (3) is also communicated with the ventilation system through a pipeline, and a third control valve capable of controlling the opening and closing of the ventilation system is arranged on the pipeline.

2. The system for preventing liquid accumulation at the bottom of a cryogenic liquid tank according to claim 1, characterized in that The liquid pipe (3) further includes a spray branch pipe (307). The outlet of the liquid main pipe is also communicated with the inlet of the spray branch pipe (307). The outlet of the spray branch pipe (307) leads to the top of the compartment. A spray control valve (308) is arranged on the spray branch pipe (307).

3. The system for preventing liquid accumulation at the bottom of a cryogenic liquid tank according to claim 2, wherein It further includes a top spray pipe (8). The outlet of the spray branch pipe (307) is communicated with the inlet of the top spray pipe (8). The top spray pipe (8) is horizontally arranged at the top of the compartment, and a plurality of spray heads (801) are arranged on the top spray pipe (8).

4. The system for preventing liquid accumulation at the bottom of a cryogenic liquid tank according to claim 1, wherein The liquid phase pipe (3) further includes an injection branch pipe (305). The outlet of the liquid phase main pipe is also communicated with the inlet of the injection branch pipe (305). The outlet of the injection branch pipe (305) leads to the bottom of the cabin, and an injection control valve (306) is provided on the injection branch pipe (305).

5. The system for preventing liquid accumulation at the bottom of a cryogenic liquid tank according to claim 4, characterized in that, It further includes a bottom injection pipe (9). The outlet of the injection branch pipe (305) is communicated with the inlet of the bottom injection pipe (9). The bottom injection pipe (9) is horizontally arranged at the bottom of the cabin, and a plurality of injection ports (901) are provided on the bottom injection pipe (9).

6. Method for preventing liquid accumulation at the bottom of a cryogenic liquid tank, characterized in that, The method is implemented by the system for preventing liquid accumulation at the bottom of a cryogenic liquid tank according to any one of claims 1-5. The method is an evaporation elimination method, including the following steps: S11: Close all valves in the system; S12: Open the second control valve (205) and the purge control valve (303); S13: Introduce dry gas into the gas phase pipe (2); S14: The dry gas passes through the pump well purge branch pipe (302) and leads to the bottom of the pump well (6) to purge the accumulated liquid.

7. Method for preventing liquid accumulation at the bottom of a cryogenic liquid tank, characterized in that, The method is implemented by the system for preventing liquid accumulation at the bottom of a cryogenic liquid tank according to any one of claims 1-5. The method is a pressure gasification method, including the following steps: S21: Close all valves in the system; S22: Open the purge control valve (303) and the third control valve; S23: Under the action of the gas pressure in the cabin, continuously push the accumulated liquid at the bottom of the cabin out of the pump well (6) and the bottom of the cabin in the reverse direction; S24: And gasify the accumulated liquid at the bottom of the cabin through the ventilation system.

8. A method for preventing liquid accumulation at the bottom of a cryogenic liquid tank, characterized in that, The method is implemented by the system for preventing liquid accumulation at the bottom of a cryogenic liquid tank according to any one of claims 1-5. The method is a pressure discharge method, including the following steps: S31: Close all valves in the system; S32: Open the purge control valve (303) and the connection control valve (501); S33: Under the action of the gas pressure in the cabin, continuously push the accumulated liquid at the bottom of the cabin out of the pump well (6) and the bottom of the cabin in the reverse direction, and discharge it through the drain pipe (401).

9. A ship safety system, characterized in that, It includes the system for preventing liquid accumulation at the bottom of a cryogenic liquid tank according to any one of claims 1-5.

10. A ship, characterized in that, It includes the on-board safety system according to claim 9.

Images