Liquefied natural gas (LNG) storage tank closed cold insulation system utilizing boil-off gas (BOG) cold energy

Abstract

The utility model relates to the technical field of cold insulation systems, in particular to an LNG (Liquefied Natural Gas) storage tank closed cold insulation system utilizing BOG (Boil Off Gas) cold energy. According to the technical scheme, mainly aiming at the problem of BOG cold energy waste caused by the fact that the cold energy of BOG is not utilized due to the fact that a direct compression process is adopted for BOG, the BOG cold energy recycling device comprises an LNG storage tank, an outer tank is arranged on the outer side of the LNG storage tank in a sleeving mode, a space is reserved between the LNG storage tank and the outer tank and used for flowing of cooling liquid, a liquid discharging pipe is arranged at the bottom of the outer tank, and the liquid discharging pipe is communicated with the LNG storage tank. A liquid inlet pipe is further mounted at the top of the outer tank; and the spraying assembly is arranged on the LNG storage tank and is used for uniformly discharging the cooling liquid. According to the LNG storage tank, the cooling capacity in BOG generated by evaporation of the liquefied natural gas in the LNG storage tank can be effectively utilized, meanwhile, the liquefied natural gas in the LNG storage tank is cooled, and potential safety hazards caused by the fact that the temperature of the liquefied natural gas is too high and the evaporation capacity is too large are effectively prevented.

Description

Technical Field

[0001] The utility model relates to the technical field of cryogenic insulation systems, and particularly relates to a closed cryogenic insulation system for an LNG storage tank utilizing BOG cold energy. Background Art

[0002] As an important device for LNG reception and storage, the cryogenic insulation performance of an LNG storage tank is directly related to the economy of the operation of the LNG storage tank. During the storage process of the LNG storage tank, the LNG inside the tank absorbs external heat and thus generates BOG (boil-off gas). The BOG evaporation rate of the LNG storage tank is a key indicator for judging whether the structural design of the LNG storage tank meets the contract requirements. During the operation of the LNG storage tank, the generation of BOG inside the tank will occupy the storage space of the LNG storage tank and increase the operating pressure of the storage tank. If not handled in time, it will bring risks to the safe operation of the LNG storage tank. When the BOG evaporation rate causes the LNG storage tank to be over-pressurized, the BOG inside the tank will be released through the BOG pipeline of the storage tank. The temperature of the BOG discharged from the LNG storage tank is -162°C, so the BOG has a large amount of cold energy.

[0003] In the existing BOG treatment processes of LNG receiving stations, there are mainly two types: direct compression of BOG and recondensation. The low-temperature BOG is compressed by a compressor and then enters the pipeline for downstream users. When the direct compression process is adopted for BOG, the cold energy of the BOG is not utilized, resulting in waste of the cold energy of the BOG. In view of this, the utility model proposes a closed cryogenic insulation system for an LNG storage tank utilizing BOG cold energy. Summary of the Utility Model

[0004] The purpose of the utility model is to address the problem in the background art that when the direct compression process is adopted for BOG, the cold energy of the BOG is not utilized, resulting in waste of the cold energy of the BOG, and to propose a closed cryogenic insulation system for an LNG storage tank utilizing BOG cold energy.

[0005] Technical solution of the utility model: An LNG storage tank closed cold insulation system using BOG cold energy, including an LNG storage tank, an outer tank is sleeved outside the LNG storage tank, a space is left between the LNG storage tank and the outer tank for the flow of coolant, a drain pipe is arranged at the bottom of the outer tank, and a liquid inlet pipe is also installed at the top of the outer tank; a spraying assembly arranged on the LNG storage tank, the spraying assembly is used to evenly discharge the coolant; an exhaust pipe installed on the top of the LNG storage tank, the exhaust pipe is used to discharge BOG gas; a heat exchanger connected to the exhaust pipe through a pipeline, the heat exchanger is used to cool the coolant with the cold energy of BOG; a supply pump, the output end of the supply pump is connected to the liquid inlet pipe through a pipeline, the input end of the supply pump is connected to a water inlet tank through a pipeline, and the water inlet tank is connected to the heat exchanger through a pipeline; a return water tank connected to the drain pipe through a pipeline, the return water tank is connected to the heat exchanger through a pipeline, and a supply pipeline is also connected to the pipeline between the heat exchanger and the return water tank.

[0006] Optionally, the spraying assembly includes a liquid storage box sleeved outside the LNG storage tank. The liquid storage box is annularly arranged and has an open top. The cross-section of the liquid storage box is arranged in a "U" shape. Fixed rings are installed on both the outer side and the inner side of the liquid storage box. First limit rings and second limit rings are respectively arranged above and below the fixed rings on both the inner and outer sides. The two groups of first limit rings are fixedly connected to the outer wall of the LNG storage tank, and the two groups of second limit rings are fixedly connected to the inner wall of the outer tank.

[0007] Optionally, a plurality of liquid flow pipes are fixedly connected to the bottom of the liquid storage box. The plurality of liquid flow pipes are annularly and arrayedly distributed. Sprayers are fixedly connected to the bottoms of the liquid flow pipes. The tops of the liquid flow pipes are slidably connected with a liquid pressing shell, and a plurality of liquid inlet holes are formed in the outer wall of the liquid pressing shell.

[0008] Optionally, a fixed frame is installed on the liquid pressing shell. A first inclined block is fixedly connected to the top of the fixed frame. The top of the first inclined block is inclined. A plurality of second inclined blocks are fixedly connected to the top wall of the outer tank. The bottom of the second inclined block is inclined and opposite to the first inclined block.

[0009] Optionally, a thickening ring is fixedly connected to the bottom of the liquid pressing shell. A spring is arranged between the thickening ring and the bottom of the liquid storage box. The spring is sleeved outside the liquid flow pipe.

[0010] Optionally, the spraying assembly further includes a servo motor installed on the top of the outer tank. The output end of the servo motor is fixedly connected with a gear. A toothed ring engaged with the gear is arranged on one side of the gear. The toothed ring is sleeved outside the liquid storage box.

[0011] Optionally, a filter screen is arranged in the return water tank. A stop valve installed on the return water tank is arranged on the side of the filter screen close to the drain pipe.

[0012] In summary, the present application includes at least one of the following beneficial technical effects:

[0013] The utility model recovers the cold energy of the BOG discharged from the LNG storage tank through the coolant. The coolant after absorbing the cold energy of the BOG is stored in the water inlet tank, pumped by the supply pump and conveyed to the spray assembly arranged on the top of the LNG storage tank, and sprayed out by the nozzles, evenly distributed on the outer wall surface of the LNG storage tank, cooling the temperature of the outer wall surface of the LNG storage tank, thereby reducing the evaporation amount of the BOG in the LNG storage tank;

[0014] Furthermore, through the setting of the spray assembly, multiple groups of nozzles distributed in an annular array make the spraying uniform. At the same time, it is convenient to control the spraying speed of the coolant, and ensure that the spraying amount of each group of nozzles is roughly the same, so as to obtain a good cooling effect;

[0015] In summary, the utility model can effectively utilize the cold energy in the BOG generated by the evaporation of liquefied natural gas in the LNG storage tank, and at the same time cool the liquefied natural gas in the LNG storage tank, effectively preventing potential safety hazards caused by excessive temperature and excessive evaporation of the liquefied natural gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of an LNG storage tank closed cold insulation system using BOG cold energy is given;

[0017] Figure 2 is a schematic diagram of the structure of the outer tank;

[0018] Figure 3 is Figure 1 an enlarged schematic diagram of part A in

[0019] Figure 4 is a schematic diagram of the structure of the liquid pressing shell;

[0020] Figure 5 is a schematic diagram of the structure of the gear ring.

[0021] Reference numerals:

[0022] 1. LNG storage tank; 11. First limit ring;

[0023] 2. Outer tank; 21. Drain pipe; 22. Liquid inlet pipe; 23. Second limit ring;

[0024] 3. Spray assembly; 301. Liquid holding box; 302. Fixed ring; 303. Liquid flow pipe; 304. Nozzle; 305. Liquid pressing shell; 306. Liquid inlet hole; 307. Fixed frame; 308. First inclined block; 309. Second inclined block; 310. Thickening ring; 311. Spring; 312. Servo motor; 313. Gear; 314. Gear ring;

[0025] 4. Exhaust pipe; 5. Heat exchanger; 6. Supply pump; 7. Water inlet tank;

[0026] 8. Water return tank; 81. Filter screen; 82. Stop valve;

[0027] 9. Make-up pipeline. Specific embodiments

[0028] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments.

[0029] The components of the embodiments of the present invention usually described and shown in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention.

[0030] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] 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 accompanying drawings, and 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 therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0032] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can 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.

[0033] Embodiment

[0034] As Figure 1As shown in the figure, a closed cold insulation system for an LNG storage tank using BOG cold energy proposed by the present utility model includes an LNG storage tank 1, which is hollow and used for storing liquefied natural gas. An outer tank 2 is sleeved outside the LNG storage tank 1, and a space is left between the LNG storage tank 1 and the outer tank 2 for the flow of a coolant, facilitating the cooling of the outer wall of the LNG storage tank 1, thereby cooling the liquefied natural gas and reducing the evaporation rate. A drain pipe 21 is provided at the bottom of the outer tank 2 to facilitate the discharge of the coolant. A liquid inlet pipe 22 is also installed at the top of the outer tank 2 to facilitate the entry of the coolant between the LNG storage tank 1 and the outer tank 2.

[0035] Further, please refer to Figures 2-5, the above-mentioned cold insulation system includes a spray component 3 arranged on the LNG storage tank 1, and the spray component 3 is used to evenly discharge the coolant. The spray component 3 includes a liquid storage box 301 sleeved on the outer ring of the LNG storage tank 1. The liquid storage box 301 is annularly arranged and has an open top. The cross-section of the liquid storage box 301 is arranged in a "U" shape, which is convenient for receiving the coolant flowing down from the liquid inlet pipe 22. Fixed rings 302 are installed on both the outer side and the inner side of the liquid storage box 301. First limit rings 11 and second limit rings 23 are respectively arranged above and below the fixed rings 302 on both the inner and outer sides. The two groups of first limit rings 11 are fixedly connected to the outer wall of the LNG storage tank 1, and the two groups of second limit rings 23 are fixedly connected to the inner wall of the outer tank 2, so that the liquid storage box 301 can rotate smoothly. A plurality of liquid flow pipes 303 are fixedly connected to the bottom of the liquid storage box 301. The plurality of liquid flow pipes 303 are arranged in an annular array. The bottom of the liquid flow pipe 303 is fixedly connected with a nozzle 304, which is convenient for spraying the coolant. The top of the liquid flow pipe 303 is slidably connected with a liquid pressing shell 305. A plurality of liquid inlet holes 306 are opened on the outer wall of the liquid pressing shell 305, which is convenient for the coolant in the liquid storage box 301 to enter the liquid pressing shell 305. Thus, when the liquid pressing shell 305 moves downward, after the liquid inlet holes 306 are blocked by the liquid flow pipes 303, as the liquid pressing shell 305 continues to move downward, the coolant in the liquid pressing shell 305 will be pressed down and sprayed out by the nozzle 304 after passing through the liquid flow pipes 303. A fixing frame 307 is installed on the liquid pressing shell 305. The top of the fixing frame 307 is fixedly connected with a first inclined block 308. The first inclined block 308 moves synchronously with the liquid pressing shell 305 through the fixing frame 307. The top of the first inclined block 308 is inclined. A plurality of second inclined blocks 309 are fixedly connected to the top wall of the outer tank 2. The bottom of the second inclined block 309 is inclined and opposite to the first inclined block 308. The first inclined block 308 contacts the second inclined block 309 after moving, thereby driving the liquid pressing shell 305 to move downward to drive the coolant to be sprayed out. A thickening ring 310 is fixedly connected to the bottom of the liquid pressing shell 305. A spring 311 is arranged between the thickening ring 310 and the bottom of the liquid storage box 301. The spring 311 is sleeved on the outer ring of the liquid flow pipe 303, which is convenient for the liquid pressing shell 305 to reset after the first inclined block 308 leaves the position of the second inclined block 309. The spray component 3 further includes a servo motor 312 installed on the top of the outer tank 2. The output end of the servo motor 312 is fixedly connected with a gear 313. A toothed ring 314 meshing with the gear 313 is arranged on one side of the gear 313. The toothed ring 314 is sleeved on the outer ring of the liquid storage box 301. After the servo motor 312 is started, it drives the gear 313 to rotate. At the same time, the gear 313 drives the toothed ring 314 to rotate, thereby driving the liquid storage box 301 to rotate smoothly.

[0036] Specifically, the above-mentioned cold insulation system further includes an exhaust pipe 4 installed on the top of the LNG storage tank 1, and the exhaust pipe 4 is used to discharge BOG gas. A heat exchanger 5 connected to the exhaust pipe 4 through a pipeline. The BOG generated in the LNG storage tank 1 enters the heat exchanger 5, and the heat exchanger 5 is used to cool the coolant with the cold energy of the BOG. The output end of the supply pump 6 is connected to the liquid inlet pipe 22 through a pipeline, and the input end of the supply pump 6 is connected to a water inlet tank 7 through a pipeline. The supply pump 6 is used to transport the coolant stored in the water inlet tank 7 to the outer tank 2. The water inlet tank 7 and the heat exchanger 5 are connected through a pipeline, facilitating the cooled coolant to enter the water inlet tank 7 for storage.

[0037] Finally, the above-mentioned cold insulation device further includes a return water tank 8 connected to the liquid discharge pipe 21 through a pipeline. The return water tank 8 is connected to the heat exchanger 5 through a pipeline, and a supply pipeline 9 is also connected to the pipeline between the heat exchanger 5 and the return water tank 8. The supply pipeline 9 is used to ensure the stability of the coolant volume and also ensure the stable operation of the supply pump 6. A filter screen 81 is provided in the return water tank 8 for filtering impurities in the coolant. A stop valve 82 installed on the return water tank 8 is provided on one side of the filter screen 81 close to the liquid discharge pipe 21 for discharging the impurities filtered by the filter screen 81.

[0038] In this embodiment, after the supply pump 6 is started, the coolant in the water inlet tank 7 is pumped into the liquid inlet pipe 22 and flows into the liquid holding box 301 through the liquid inlet pipe 22. At the same time, the coolant enters the liquid pressing shell 305 through the liquid inlet hole 306. At this time, the servo motor 312 is started, and the servo motor 312 drives the gear 313 to rotate and mesh with the gear ring 314. At this time, the gear ring 314 rotates and drives the liquid holding box 301 to rotate. The liquid holding box 301 rotates smoothly under the limiting action of the fixed ring 302, the first limiting ring 11 and the second limiting ring 23. When the first inclined block 308 moves to the contact position with the second inclined block 309, the first inclined block 308 is squeezed and moves downward, and at the same time drives the liquid pressing shell 305 to move downward. When the liquid inlet hole 306 is blocked by the liquid flow pipe 303, the liquid pressing shell 305 continues to move downward and squeezes the coolant in the liquid pressing shell 305 to be sprayed out by the nozzle 304 through the liquid flow pipe 303. The coolant sprayed by multiple nozzles 304 passes through the outer wall of the LNG storage tank 1, reducing the temperature of the outer wall of the LNG storage tank 1, thereby cooling the liquefied natural gas in the LNG storage tank 1.

[0039] At the same time, the BOG generated in the LNG storage tank 1 is discharged through the exhaust pipe 4 and enters the heat exchanger 5. Similarly, the coolant in the outer tank 2 also enters the heat exchanger 5 after being filtered by the filter screen 81. The coolant exchanges heat with the BOG, reducing the temperature of the coolant. After that, the coolant is stored in the water inlet tank 7 for circulating cooling.

[0040] The above specific embodiments are merely an optional embodiment of the present utility model. Based on the technical solution of the present utility model and the relevant revelations of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A closed cold insulation system for an LNG storage tank utilizing BOG cold energy, characterized in that, Comprising: An LNG storage tank (1), an outer tank (2) is sleeved outside the LNG storage tank (1), a space is left between the LNG storage tank (1) and the outer tank (2) for the flow of coolant, a drain pipe (21) is arranged at the bottom of the outer tank (2), and a liquid inlet pipe (22) is also installed at the top of the outer tank (2); A spraying assembly (3) arranged on the LNG storage tank (1), the spraying assembly (3) is used for uniformly discharging coolant; An exhaust pipe (4) installed at the top of the LNG storage tank (1), the exhaust pipe (4) is used for discharging BOG gas; A heat exchanger (5) connected to the exhaust pipe (4) through a pipeline, the heat exchanger (5) is used for cooling the coolant with the cold energy of BOG; A supply pump (6), the output end of the supply pump (6) is connected to the liquid inlet pipe (22) through a pipeline, the input end of the supply pump (6) is connected to a water inlet tank (7) through a pipeline, and the water inlet tank (7) is connected to the heat exchanger (5) through a pipeline; A return water tank (8) connected to the drain pipe (21) through a pipeline, the return water tank (8) is connected to the heat exchanger (5) through a pipeline, and a supply pipeline (9) is also connected to the pipeline between the heat exchanger (5) and the return water tank (8).

2. The closed cold insulation system for an LNG storage tank utilizing BOG cold energy according to claim 1, wherein The spraying assembly (3) includes a liquid storage box (301) sleeved outside the LNG storage tank (1), the liquid storage box (301) is annularly arranged and has an open top, the cross-section of the liquid storage box (301) is in a "U" shape, fixing rings (302) are installed on both the outer side and the inner side of the liquid storage box (301), a first limiting ring (11) and a second limiting ring (23) are respectively arranged above and below the fixing rings (302) on both the inner and outer sides, the two groups of first limiting rings (11) are fixedly connected to the outer wall of the LNG storage tank (1), and the two groups of second limiting rings (23) are fixedly connected to the inner wall of the outer tank (2).

3. The closed cold insulation system for LNG storage tank using BOG cold energy according to claim 2, wherein, A plurality of liquid flow pipes (303) are fixedly connected to the bottom of the liquid storage box (301), the plurality of liquid flow pipes (303) are arranged in an annular array, a nozzle (304) is fixedly connected to the bottom of the liquid flow pipe (303), a liquid pressing shell (305) is slidably connected to the top of the liquid flow pipe (303), and a plurality of liquid inlet holes (306) are formed in the outer wall of the liquid pressing shell (305).

4. A closed cryogenic insulation system for an LNG storage tank utilizing BOG cold energy according to claim 3, characterized in that, A fixing frame (307) is installed on the liquid pressing shell (305), a first inclined block (308) is fixedly connected to the top of the fixing frame (307), the top of the first inclined block (308) is inclined, a plurality of second inclined blocks (309) are fixedly connected to the top wall of the outer tank (2), and the bottom of the second inclined block (309) is inclined and opposite to the first inclined block (308).

5. The closed cold insulation system for LNG storage tank utilizing BOG cold energy according to claim 4, characterized in that, A thickening ring (310) is fixedly connected to the bottom of the liquid pressing shell (305), a spring (311) is arranged between the thickening ring (310) and the bottom of the liquid storage box (301), and the spring (311) is sleeved outside the liquid flow pipe (303).

6. The closed cold insulation system for LNG storage tank using BOG cold energy according to claim 5, characterized in that The spray assembly (3) further includes a servo motor (312) installed at the top of the outer tank (2). The output end of the servo motor (312) is fixedly connected to a gear (313). One side of the gear (313) is provided with a toothed ring (314) meshing with it. The toothed ring (314) is sleeved on the outer circle of the liquid storage box (301).

7. The closed cold insulation system for LNG storage tank using BOG cold energy according to claim 6, wherein A filter screen (81) is arranged in the water return tank (8). A stop valve (82) installed on the water return tank (8) is arranged on one side of the filter screen (81) close to the drain pipe (21).

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