A nitrogen replacement device for an LNG storage tank

Abstract

The present invention discloses a nitrogen replacement device for an LNG storage tank, which includes a tank body. One side of the bottom of the tank body is provided with a replacement pipe, and one end of the replacement pipe arranged inside the tank body is provided with a replacement mechanism. The replacement mechanism includes a sealing assembly, and the replacement mechanism can seal the replacement pipe through the sealing assembly to prevent the stored LNG from leaking. The beneficial effect of the present invention is that when nitrogen is introduced into the storage tank through the replacement pipe, an interval is generated between the sealing assembly and the replacement pipe, which facilitates the entry of nitrogen into the storage tank. When storing liquefied natural gas, due to the low temperature and high pressure of the storage environment, the sealing assembly passively further seals the replacement pipe in this environment, thereby reducing or even avoiding the occurrence of leakage during the storage of liquefied natural gas.

Description

Technical Field

[0001] The present invention relates to the technical field of nitrogen replacement, and particularly relates to a nitrogen replacement device for an LNG storage tank. Background Art

[0002] Liquefied natural gas is abbreviated as LNG, and its main component is methane. It is recognized as the cleanest fossil energy on the earth. It is colorless, odorless, non-toxic and non-corrosive, and its volume is about 1 / 625 of the volume of the same amount of gaseous natural gas. Liquefied natural gas is obtained by compressing and cooling natural gas to its freezing point (-161.5°C), and usually liquefied natural gas is stored in a low-temperature storage tank at about -162°C and 0.1 MPa. European standard EN14620 and national standard GB / T 26978 stipulate that for large LNG full containment storage tanks, the inner tank and the space above the ceiling must be dried to a dew point temperature lower than -20°C and inerted to a maximum oxygen content of 9%. For the annular space, it must be dried to a dew point temperature lower than -10°C and a maximum oxygen content of 9%. During the use of the storage tank, in order to maintain the pressure in the storage tank basically constant, nitrogen replacement must be carried out when the storage tank is emptied. After nitrogen replacement at the bottom of the tank, the dew point is 10°C lower than the initial dew point measurement value, and the maximum oxygen content is 9%.

[0003] For example, in the invention patent with the authorization announcement number CN104279421B, the authorization announcement date is April 13, 2016, and the name is "Nitrogen Replacement System for LNG Storage Tank", which includes a nitrogen inlet pipe, a tank top venting system for nitrogen drying and replacement in the inner tank, a nitrogen drying and replacement pipe above the bottom insulation layer of the tank, and a nitrogen drying and replacement pipe below the bottom insulation layer of the tank; the nitrogen inlet pipe extends along the wall plate of the inner tank of the LNG storage tank to the bottom of the inner tank; the tank top venting system for nitrogen drying and replacement in the inner tank is arranged at the top of the LNG storage tank; the nitrogen drying and replacement pipe above the bottom insulation layer of the tank extends along the insulation layer of the tank wall of the LNG storage tank to the upper concrete leveling layer of the bottom foam glass brick insulation layer of the tank; the nitrogen drying and replacement pipe below the bottom insulation layer of the tank extends along the insulation layer of the tank wall of the LNG storage tank to the bottom insulation layer of the tank; the nitrogen drying and replacement pipe below the bottom insulation layer of the tank is arranged in the channel of the lower concrete leveling layer of the bottom insulation layer of the tank. In the nitrogen replacement system of the LNG storage tank of the present invention, after the nitrogen replacement in the inner tank is completed, the nitrogen replacement of the annular space and the upper and lower parts of the bottom of the tank can be started simultaneously, the N2 gas flow rate increases, and the drying and inerting rate is accelerated.

[0004] The deficiencies of the prior art are that the nitrogen replacement devices in the prior art generally seal the pipes for nitrogen replacement only by valves or valves plus check valves, so that in the low-temperature and high-pressure environment during the storage of LNG, it is easy to cause leakage of the pipes for nitrogen replacement only under the sealing action of the valves and check valves. Summary of the Invention

[0005] The object of the present invention is to provide a nitrogen replacement device for an LNG storage tank to solve the above deficiencies in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solution: A nitrogen replacement device for an LNG storage tank, comprising a tank body, one side of the bottom of the tank body is provided with a replacement pipe, and one end of the replacement pipe arranged inside the tank body is provided with a replacement mechanism, the replacement mechanism includes a sealing component, and the sealing component is passively contracted when the temperature is lower than -50 degrees to seal the pipe orifice of the replacement pipe.

[0007] As above, the replacement mechanism further includes a replacement component, the replacement component includes a fixed exhaust plate and a movable exhaust plate, one movable exhaust plate is arranged on each side of the fixed exhaust plate through a guide pipe, and a plurality of exhaust holes are evenly arranged on the side of the fixed exhaust pipe and the movable exhaust plate away from the tank body, and the fixed exhaust pipe and the movable exhaust plate can evenly spray nitrogen into the interior of the tank body through a pushing mechanism.

[0008] As above, in the vertical direction, the diameters of a plurality of exhaust holes gradually increase from bottom to top.

[0009] As above, the pushing mechanism includes an extension pipe, and a plurality of first reset components are evenly arranged on the outer side of the extension pipe.

[0010] As above, a plurality of delivery pipes are arranged at the bottom of the tank body, and air injection holes are evenly arranged on the delivery pipes.

[0011] As above, the sealing component includes a telescopic structure and a sealing member, the telescopic structure is arranged inside the replacement pipe, the telescopic end of the telescopic structure is provided with the sealing member, and the telescopic structure can passively control the movement of the sealing member to seal the replacement pipe.

[0012] As above, the telescopic structure includes a support cylinder, a telescopic space is arranged inside the support cylinder, a telescopic rod is slidably arranged inside the telescopic space, a first elastic member is arranged on one side of the telescopic space, and gas is filled on the other side of the telescopic space.

[0013] As above, two circular holes are arranged in parallel on the telescopic rod, and a first channel is opened in the middle of the telescopic rod, the first channel is communicated with the circular holes, a rubber block is slidably arranged in each circular hole, a second elastic member is arranged between the rubber block and the circular hole, and one end of the first elastic member is provided with a ring.

[0014] As above, a second channel is arranged in the middle of the sealing member, an annular groove is arranged on the surface of the sealing member close to the replacement pipe, and a third channel is further arranged inside the edge of the sealing member, and the third channel is communicated with the annular groove.

[0015] As described above, the sealing assembly further includes two locking hooks. A second reset member is disposed on a side of each locking hook facing away from the other. The locking hooks can limit the sealing member during sealing.

[0016] In the above technical solution, the beneficial effect of the present invention is that when nitrogen is introduced into the storage tank through the replacement pipe, an interval is generated between the sealing assembly and the replacement pipe, facilitating the entry of nitrogen into the storage tank. When storing liquefied natural gas, due to the low-temperature and high-pressure storage environment, the sealing assembly passively further seals the replacement pipe in this environment, thereby reducing or even avoiding leakage during the storage of liquefied natural gas. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0018] Figure 1 Schematic three-dimensional structure diagram between the tank body and the replacement pipe provided by the embodiment of the present invention;

[0019] Figure 2 Top view between the tank body and the replacement pipe provided by the embodiment of the present invention;

[0020] Figure 3 Provided by another embodiment of the present invention Figure 2 A-A cross-sectional view;

[0021] Figure 4 Partial cross-sectional view between the tank body, the replacement pipe and the sealing assembly provided by another embodiment of the present invention;

[0022] Figure 5 Provided by another embodiment of the present invention Figure 4 Enlarged schematic view at position N;

[0023] Figure 6 Provided by another embodiment of the present invention Figure 3 Enlarged schematic view at position M;

[0024] Figure 7 Schematic three-dimensional structure diagram of the replacement assembly provided by another embodiment of the present invention;

[0025] Figure 8 Cross-sectional view between the fixed exhaust plate, the movable exhaust plate and the pushing mechanism provided by another embodiment of the present invention.

[0026] Description of the reference numerals:

[0027] 1. Tank body; 2. Replacement pipe; 3. Sealing assembly; 31. Telescopic structure; 310. Support cylinder; 311. Telescopic space; 3111. Installation part; 3112. Inflatable part; 312. Telescopic rod; 3120. First channel; 3121. Rubber block; 3122. Second elastic member; 3123. Ring; 3124. Disk part; 3125. Round rod part; 3126. Rectangular groove; 313. First elastic member; 314. Locking hook; 315. Second reset member; 32. Sealing member; 320. Second channel; 321. Annular groove; 322. Third channel; 323. Drain hole; 324. Drain groove; 4. Replacement assembly; 40. Delivery pipe; 401. Fan blade; 402. Turbine; 41. Fixed exhaust plate; 42. Air guide pipe; 43. Movable exhaust plate; 44. Exhaust hole; 45. Pushing mechanism; 451. Elongated pipe; 452. First reset member; 453. Through hole. Detailed implementation mode

[0028] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further introduced in detail below in conjunction with the accompanying drawings.

[0029] As Figures 1-8 shown, a nitrogen replacement device for an LNG storage tank provided by an embodiment of the present invention includes a tank body 1. One side of the bottom of the tank body 1 is provided with a replacement pipe 2. One end of the replacement pipe 2 arranged inside the tank body 1 is connected with a replacement mechanism. The replacement mechanism includes a sealing assembly 3. The sealing assembly 3 is passively contracted when the temperature is lower than -50°C to close the nozzle of the replacement pipe 2. Thus, when liquefied natural gas is filled into the tank body 1, since the temperature of the liquefied natural gas is much lower than -50°C, on the basis of the valve on the replacement pipe 2 being closed once, a passive secondary closure can also be carried out, reducing the probability of leakage.

[0030] Specifically, a liquid inlet valve (not shown in the figure) and a liquid discharge valve (not shown in the figure) are further provided on the side of the tank body 1, and a vent valve (not shown in the figure) is provided in the middle of the upper end of the dome of the tank body 1. These are all prior arts and will not be elaborated. A valve and a check valve are provided on the replacement pipe 2, and the sealing assembly 3 is arranged inside the replacement pipe 2. In this embodiment, when replacing nitrogen, a device for storing nitrogen (not shown in the figure) is connected to the tank body 1 through the replacement pipe 2. The check valve is opened to allow nitrogen to pass through the replacement pipe 2 and pass through the sealing assembly 3 into the interior of the tank body 1, so that the pressure in the tank body 1 becomes larger or basically constant after the nitrogen enters. At this time, the vent valve provided on the dome of the tank body 1 is opened, so that the nitrogen entering the interior of the tank body 1 discharges the mixed gas of oxygen and water vapor replaced inside the tank body 1 into the atmosphere. During the replacement process, the oxygen content and dew point (the "dew point" is a thermodynamics term. Generally, the lower the dew point, the less water vapor is contained in the air and the drier it is) inside the tank body 1 are detected; after the dew point and oxygen content in the tank body 1 meet the standards and the gas replacement in the tank body 1 is completed, first the vent valve is closed, then the valve on the replacement pipe 2 and other valve bodies are closed, and finally the liquefied natural gas is transported into the tank body 1 through the liquid inlet valve through a pipeline for storage. After the liquefied natural gas enters the tank body 1, due to its storage environment of low temperature and high pressure (-162 °C, 0.1 Mpa), the sealing assembly 3 undergoes a cold shrinkage phenomenon in the low-temperature environment, so that the sealing assembly 3 shrinks to seal the end of the replacement pipe 2 close to the tank body 1, thereby preventing the liquefied natural gas from leaking during storage.

[0031] When nitrogen is introduced into the storage tank through the replacement pipe 2 by the nitrogen replacement device for an LNG storage tank provided in the embodiment of the present invention, an interval is generated between the sealing assembly 3 and the replacement pipe 2, which facilitates the entry of nitrogen into the storage tank. When storing liquefied natural gas, due to the storage environment of low temperature and high pressure, the sealing assembly 3 passively further seals the replacement pipe 2 in this environment, thereby reducing or even avoiding the leakage of liquefied natural gas during storage.

[0032] In another embodiment provided by the present invention, the replacement mechanism further includes a replacement component 4. The replacement component 4 includes a fixed exhaust plate 41. On both sides of the fixed exhaust plate 41, a moving exhaust plate 43 is provided through a trachea 42 respectively. A plurality of exhaust holes 44 are evenly arranged on the sides of the fixed exhaust plate 41 and the moving exhaust plate 43 away from the tank body 1. The fixed exhaust plate 41 and the moving exhaust plate 43 can evenly spray nitrogen into the interior of the tank body 1 through a pushing mechanism 45. Specifically, the interiors of the fixed exhaust plate 41 and the moving exhaust plate 43 are cavity structures, and the cavity structures are connected to the interior of the tank body 1 through a plurality of the exhaust holes 44. Two arc-shaped grooves are provided at the bottom of the tank body 1, and a moving exhaust plate 43 is slidably arranged in each arc-shaped groove. The moving exhaust plate 43 is vertically arranged and its lower end is slidably arranged in a sliding groove. The arc-shaped grooves are arranged along the inner side of the bottom of the tank body 1 and along the side wall of the tank body 1. In this way, the moving exhaust plate 43 can move while fitting on the inner side wall of the tank body 1. The fixed exhaust plate 41 is connected to each moving exhaust plate 43 through a pushing mechanism 45, and the cavity structure of the fixed exhaust plate 41 is connected to the cavity structures of the two moving exhaust plates 43 through the trachea 42. In this embodiment, when nitrogen is filled into the tank body 1 through the replacement pipe 2, the nitrogen enters the fixed exhaust plate 41 through the replacement pipe 2 and is sprayed into the tank body 1 through a plurality of the exhaust holes 44 opened on the fixed exhaust plate 41. At the same time, the nitrogen enters the cavity structure of the moving exhaust plate 43 through the trachea 42, so that a plurality of the exhaust holes 44 opened on the moving exhaust plate 43 spray nitrogen into the tank body 1. When the nitrogen enters the moving exhaust plate 43 through the trachea 42, the gas can also enter the pushing mechanism 45, so that the pushing mechanism 45 pushes the moving exhaust plate 43 connected thereto to slide along the arc-shaped groove, so that the moving exhaust plate 43 evenly sprays nitrogen into the tank body 1 during the movement to discharge the original air in the tank body 1.

[0033] In another embodiment provided by the present invention, in the vertical direction, the diameters of a plurality of exhaust holes 44 gradually increase from bottom to top. Specifically, the replacement pipe 2 is located below the fixed exhaust plate 41, and the trachea 42 is located below the moving exhaust plate 43. In this way, the diameters of a plurality of exhaust holes 44 on the fixed exhaust plate 41 and the moving exhaust plate 43 gradually increase from bottom to top, which is convenient for nitrogen to be evenly sprayed from the fixed exhaust plate 41 and the moving exhaust plate 43.

[0034] In another embodiment provided by the present invention, the pushing mechanism 45 includes an extension tube 451. A plurality of first reset members 452, such as springs, are uniformly arranged on the outer side of the extension tube 451. Specifically, the extension tube 451 is a flexible through tube. The extension tube 451 includes a plurality of raised rings 4510. The raised rings 4510 can be deformed under force. The first reset members 452 are arranged between adjacent two raised rings 4510. Moreover, a plurality of first reset members 452, such as three, are uniformly arranged along the circumferential direction of the outer side of the raised ring 4510. One end of the extension tube 451 is connected to the fixed exhaust plate 41 and is in communication therewith. One end of the extension tube 451 connected to the movable exhaust plate 43 is not in communication therewith. And a through hole 453 is formed at the end of the extension tube 451 connected to the movable exhaust plate 43. The diameter of the through hole 453 is much smaller than the diameter of the extension tube 451. In this embodiment, when nitrogen enters the cavity structure in the fixed exhaust plate 41 through the replacement tube 2, the nitrogen entering the cavity structure in the fixed exhaust plate 41 has three directions: First, it directly sprays into the tank body 1 through a plurality of exhaust holes 44 provided on the fixed exhaust plate 41; Second, it is transported to the cavity structure in the movable exhaust plate 43 through the air guide tube 42 and then sprays into the tank body 1 through a plurality of exhaust holes 44 provided on the movable exhaust plate 43; Third, the nitrogen enters the extension tube 451. As the amount of nitrogen filled increases, and since the diameter of the through hole 453 is much smaller than the diameter of the extension tube 451, the nitrogen entering the extension tube 451 cannot be completely discharged in time. Thus, the nitrogen squeezes the raised ring 4510, causing the raised ring 4510 to pull the first reset member 452 to elongate, thereby causing the extension tube 451 to elongate. At the same time, the elongated extension tube 451 and the first reset member 452 drive the movable exhaust plate 43 to slide along the arc-shaped groove (since the extension tube 451 is a flexible through tube, the movable exhaust plate 43 can deflect to move along the arc-shaped groove), so that the movable exhaust plate 43 sprays nitrogen into the tank body 1 while moving; After the nitrogen replacement is completed, the pressure inside the tank body 1 remains constant and does not change. Thus, the inside of the extension tube 451 is in communication with the inside of the tank body 1 through the through hole 453, making the pressure inside the extension tube 451 the same as the pressure inside the tank body 1. At this time, under the action of the reset of the first reset member 452, the first reset member 452 can pull the extension tube 451 to reset, thereby causing the extension tube 451 to drive the movable exhaust plate 43 to reset.

[0035] In another embodiment provided by the present invention, a plurality of delivery pipes 40 are provided at the bottom of the tank body 1, and a plurality of air injection holes are uniformly arranged on the delivery pipes 40. Specifically, the delivery pipes 40 are communicated with the cavity structure of the fixed exhaust plate 41. Thus, during nitrogen replacement, nitrogen is ejected from the upper layer and the middle side of the tank body 1 through the fixed exhaust plate 41 and the movable exhaust plate 43, so as to orderly replace the gas in the upper layer and the middle layer. At the same time, after being transported through the delivery pipes 40, nitrogen is ejected from the bottom of the tank body 1 through the air injection holes, thereby facilitating the rapid replacement of the mixed gas of oxygen and water vapor inside the tank body 1.

[0036] Preferably, a fan blade 401 is rotatably arranged at the bottom of the tank body 1, and a turbine 402 is coaxially arranged at the lower end of the fan blade 401. Specifically, the turbine 402 is arranged inside the bottom of the tank body 1, and the middle part of the delivery pipe 40 located in the middle of the bottom of the tank body 1 passes through the side of the turbine 402 (that is, the nitrogen transported by the delivery pipe 40 located in the middle of the bottom of the tank body 1 can blow the turbine 402), and the fan blade 401 is located directly below the vent valve. Thus, during nitrogen replacement, when nitrogen is transported through the delivery pipe 40 and ejected from the air injection holes, the nitrogen transported by the delivery pipe 40 located in the middle of the bottom of the tank body 1 can drive the turbine 402 to rotate, so that the turbine 402 drives the fan blade 401 to rotate, thereby enabling the upward airflow generated by the rotation of the fan blade 401 to drive the nitrogen ejected from the air injection holes to rise rapidly, so that nitrogen can rapidly replace the mixed gas of oxygen and water vapor inside the tank body 1.

[0037] In another embodiment provided by the present invention, the sealing assembly 3 includes a telescopic structure 31 and a seal 32. The telescopic structure 31 is disposed inside the replacement pipe 2. A seal 32 is provided at the telescopic end of the telescopic structure 31. The telescopic structure 31 can passively control the movement of the seal 32 to seal the replacement pipe 2. Specifically, in the natural state, the telescopic structure 31 is in the extended state. At this time, the telescopic structure 31 can drive the seal 32 away from the pipe orifice of the replacement pipe 2, and the seal 32 does not seal the replacement pipe 2, so that it is convenient for nitrogen to enter the inside of the tank body 1 through the replacement pipe 2; when liquefied natural gas enters the tank body 1, due to the low-temperature and high-pressure storage environment of the liquefied natural gas, the telescopic structure 31 contracts in the low-temperature environment, so that the telescopic structure 31 drives the seal 32 to approach and closely fit on the end of the replacement pipe 2, so that the seal 32 seals the replacement pipe 2. Cooperating with the valves and check valves on the replacement pipe 2 to perform multiple seals on the replacement pipe 2, reducing or even avoiding the leakage of liquefied natural gas. Moreover, according to the temperature, the telescopic structure 31 can expand and contract, so that the contraction structure passively adjusts the seal 32 to open during nitrogen replacement and drying of the replacement pipe 2 and seal during the storage of liquefied natural gas, reducing manual control or electric control, and thus reducing the occurrence of accidents.

[0038] In another embodiment provided by the present invention, the telescopic structure 31 includes a support cylinder 310. The support cylinder 310 is arranged on the central axis of the replacement pipe 2 through a connection structure, and there is an annular channel for gas to pass between it and the inner wall of the replacement pipe 2. A telescopic space 311 is provided inside the support cylinder 310. A telescopic rod 312 is slidably arranged in the telescopic space 311. The other end of the telescopic rod 312 is located outside the replacement pipe 2, that is, inside the tank body 1, and is provided with the seal 32. A first elastic member 313 such as a spring is provided on one side of the telescopic space 311, and gas is filled on the other side of the telescopic space 311. Specifically, the support cylinder 310 is arranged inside the replacement pipe 2, and there is an annular channel between the support cylinder 310 and the inner wall of the replacement pipe 2, which facilitates the passage of nitrogen. The telescopic rod 312 is in dynamic seal with the support cylinder 310. The telescopic space 311 includes a mounting part 3111 and an air-filled part 3112 separated by a disc part 3124 provided at the end of the telescopic rod 312. The first elastic member 313 and the ring 3123 are both arranged in the mounting part 3111. Gas is filled in the air-filled part 3112, and the amount of gas filled can make the first elastic member 313 in a compressed state when nitrogen is introduced. At the same time, the amount of gas filled can ensure that when storing liquefied natural gas, due to the lower temperature, the gas shrinks, and the first elastic member 313 elongates or is in a natural state, so as to ensure that the telescopic rod 312 can slide under the phenomenon of thermal expansion and contraction of the gas, and at the end of the sliding stroke, the seal 32 seals the end of the replacement pipe 2. In this embodiment, during nitrogen replacement, nitrogen passes through the replacement pipe 2 and passes through the annular channel between the support cylinder 310 and the inner wall of the replacement pipe 2 to enter the inside of the tank body 1. Since the temperature of the nitrogen entering the replacement pipe 2 at this time is not enough to cause the gas in the air-filled part 3112 to contract or the contraction is not obvious, it is difficult for the first elastic member 313 to squeeze the telescopic rod 312 to make it move. Thus, the telescopic rod 312 does not move significantly, and the telescopic rod 312 does not drive the seal 32 to seal the end of the replacement pipe 2, ensuring that nitrogen can smoothly enter the inside of the tank body 1; after storing liquefied natural gas, the low-temperature and high-pressure environment causes the air in the air-filled part 3112 to be fully compressed when cooled, resulting in a negative pressure in the air-filled part 3112. At the same time, the first elastic member 313 recovers and squeezes the telescopic rod 312. Thus, the telescopic rod 312 can drive the seal 32 to move, so that the seal 32 performs a passive secondary seal on the end of the replacement pipe 2 (the valve of the replacement pipe 2 itself is a primary seal), avoiding the leakage of the stored liquefied natural gas from the replacement pipe 2.

[0039] In another embodiment provided by the present invention, two circular holes are arranged in parallel at one end of the telescopic rod 312 where the disc portion 3124 is provided. The two circular holes face the mounting portion 3111, and a first channel 3120 is formed on the central axis of the telescopic rod 312. The first channel 3120 is communicated with the two circular holes. A rubber block 3121 is slidably arranged in each circular hole. A second elastic member 3122 such as a spring is arranged between the rubber block 3121 and the bottom wall of the circular hole. One end of the first elastic member 313 is provided with a ring 3123. Specifically, the telescopic rod 312 includes a disc portion 3124 and a round rod portion 3125. Two circular holes are formed at one end of the disc portion 3124 close to the mounting portion 3111, and the two circular holes are communicated with each other. A rubber block 3121 is slidably arranged in each circular hole. A plurality of rectangular grooves 3126 are evenly formed in the circumferential direction at one end of the rubber block 3121 close to the disc portion 3124. A first channel 3120 is arranged in the round rod portion 3125. The axis between the round rod portion 3125 and the first channel 3120 coincides. The first channel 3120 is communicated with the two circular holes. One end of the first elastic member 313 close to the disc portion 3124 is provided with a ring 3123. The ring 3123 is slidably sleeved on the round rod portion 3125. In this embodiment, the ring 3123 has two states during the sliding process of the telescopic rod 312: In the first state, the gas in the inflation portion 3112 does not contract or expand, and the telescopic rod 312 does not move. At this time, the first elastic member 313 presses the ring 3123 against the surface of the disc portion 3124, so that it is convenient for the ring 3123 to press the rubber block 3121 and compress the second elastic member 3122, so that the rubber block 3121 is tightly pressed in the circular hole. The rectangular grooves 3126 provided on the rubber block 3121 are always in the circular hole. At this time, the rubber block 3121 seals the circular hole, and it is difficult for liquefied natural gas to enter the mounting portion 3111 through the first channel 3120 and the circular hole to squeeze the end of the disc portion 3124, and it is difficult for the telescopic rod 312 to move;Second state: When storing liquefied natural gas, the ambient temperature around the gas charging part 3112 drops, the gas in the gas charging part 3112 cools and contracts to generate negative pressure. Thus, the telescopic rod 312 moves in the direction close to the gas charging part 3112, and the first elastic member 313 begins to recover, so that the extrusion force of the first elastic member 313 on the ring 3123 becomes smaller. At this time, the second elastic member 3122 also begins to reset, so that the second elastic member 3122 extrudes the rubber block 3121 to move away from the disc part 3124 in the round hole, so that the rectangular groove 3126 on the rubber block 3121 is exposed. Thus, the liquefied natural gas can sequentially pass through the first channel 3120, the round hole, and the rectangular groove 3126 and enter the installation part 3111, so that the negative pressure generated by the gas charging part 3112, the extrusion of the first elastic member 313, and the extrusion generated by the liquefied natural gas entering the installation part 3111 jointly provide the power for the movement of the telescopic rod 312, facilitating the telescopic rod 312 to drive the seal 32 to move in the direction close to the end of the replacement pipe 2 to seal the end of the replacement pipe 2. Moreover, the greater the pressure and the lower the temperature of the stored liquefied natural gas, the tighter the seal 32 seals the end of the replacement pipe 2; when the liquefied natural gas gradually discharges from the tank body 1, the pressure generated by it becomes smaller. At this time, the liquefied natural gas in the installation part 3111 gradually discharges through the rectangular groove 3126, the round hole, and the first channel 3120. At the same time, the temperature around the gas charging part 3112 rises, and the gas in the gas charging part 3112 expands due to heat, thus squeezing the telescopic rod 312 to move close to the installation part 3111. At this time, the extrusion force on the first elastic member 313 increases, so that the ring 3123 squeezes the rubber block 3121 and the second elastic member 3122 to make the rubber block 3121 gradually enter the round hole, so that the rubber block 3121 seals the round hole again. Thus, the ring 3123 is converted from the second state to the first state again.;

[0040] In another embodiment provided by the present invention, a second channel 320 is provided in the middle of the seal 32. An annular groove 321 is provided on the surface of the seal 32 close to the replacement pipe 2. A third channel 322 is further provided inside the edge of the seal 32. The third channel 322 communicates with the annular groove 321. Specifically, the seal 32 is arranged inside the cavity structure of the fixed exhaust plate 41. The second channel 320 communicates with the first channel 3120 and their axes coincide. Two discharge holes 323 are arranged in parallel at one end of the seal 32 away from the telescopic rod 312. Both of the two discharge holes 323 communicate with the second channel 320. A discharge groove 324 is provided on the outside of the seal 32. There are multiple discharge grooves 324, and the multiple discharge grooves 324 are evenly arranged along the circumferential direction of the seal 32. The discharge groove 324 is connected to the annular groove 321 through the third channel 322. The position of the seal 32 in the annular groove 321 is made of rubber material to ensure that the annular groove 321 is deformed under pressure. In this embodiment, when storing liquefied natural gas, the cold shrinkage of the inflation part 3112 generates negative pressure to drive the telescopic rod 312 to move in the direction close to the inflation part 3112. At this time, the second elastic member 3122 squeezes the rubber block 3121 to slide it out of the round hole and expose the rectangular groove 3126, so that the telescopic rod 312 drives the end of the seal 32 close to the replacement pipe 2. When the seal 32 approaches the end of the replacement pipe 2, liquefied natural gas enters the second channel 320 through the discharge hole 323, so that the liquefied natural gas passes through the second channel 320, the round hole, and the rectangular groove 3126 and enters the installation part 3111, thereby providing power for the movement of the telescopic rod 312, so that the telescopic rod 312 drives the seal 32 to fit on the inner wall of the cavity structure at the end of the replacement pipe 2 and inside the fixed exhaust plate 41. When the seal 32 fits on the end of the replacement pipe 2, the discharge groove 324 first enters the replacement pipe 2. At this time, the liquefied natural gas in the replacement pipe 2 is squeezed to hinder the entry of the seal 32. To solve this problem, the liquefied natural gas in the replacement pipe 2 can enter the tank body 1 through the third channel 322 and the annular groove 321, and the pressure in the tank body 1 squeezes the seal 32, so that the annular groove 321 closely adheres to the inner wall of the cavity structure at the end of the replacement pipe 2 and inside the fixed exhaust plate 41, producing an effect similar to a suction cup to ensure that the seal 32 closely adheres to the end of the replacement pipe 2 to ensure sealing.

[0041] In another embodiment provided by the present invention, the sealing assembly 3 further includes two locking hooks 314. On the side of the locking hooks 314 facing away from each other, a second reset member 315 such as a spring is provided. The locking hooks 314 can limit the position of the seal 32 during sealing. Specifically, an inclined angle is provided at one end of the locking hook 314 close to the seal 32. The locking hook 314 is rotatably arranged on the inner wall of the cavity structure of the fixed exhaust plate 41. The second reset member 315 is arranged between the inner wall of the cavity structure of the fixed exhaust plate 41 and the locking hook 314. In this embodiment, when storing liquefied natural gas, the seal 32 fits on the inner wall of the cavity structure at the end of the replacement pipe 2 and inside the fixed exhaust plate 41. At this time, the second reset member 315 presses the locking hook 314, so that the locking hook 314 can lock and limit the seal 32, avoiding the seal 32 detaching from the inner wall of the cavity structure at the end of the replacement pipe 2 and inside the fixed exhaust plate 41 and affecting the sealing effect. When the stored liquefied natural gas is gradually discharged, the pressure inside the tank 1 also decreases accordingly. At this time, the gas in the inflation part 3112 thermally expands and presses the telescopic rod 312. At the same time, the liquefied natural gas in the installation part 3111 also slowly discharges, causing the telescopic rod 312 to drive the seal 32 to move towards the end away from the inflation part 3112. The seal 32 has a tendency to detach from the replacement pipe 2. To solve the above problems and maintain the sealing effect of the seal 32, the edge of the seal 32 is clamped and limited by the locking hook 314, avoiding the situation that the seal 32 is loose and difficult to seal when the pressure change in the tank 1 is small. At the same time, when nitrogen replacement is carried out again, nitrogen enters the annular groove 321 through the third channel 322, thereby restoring the annular groove 321 closely attached to the end of the replacement pipe 2 to its original state, and impacting the seal 32 with nitrogen. At this time, due to the relatively high pressure, the seal 32 is forced to deform to disengage from the locking hook 314, so that the telescopic rod 312 drives the seal 32 to reset to allow nitrogen to smoothly enter the tank 1 for replacement.

[0042] Only some exemplary embodiments of the present invention have been described by way of illustration above. Without doubt, for those of ordinary skill in the art, various different ways can be used to modify the described embodiments without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the protection scope of the claims of the present invention.

Claims

1. A nitrogen replacement device for an LNG storage tank, comprising a tank body. One side of the bottom of the tank body is provided with a replacement pipe, and a replacement mechanism is arranged at one end of the replacement pipe inside the tank body. It is characterized in that, The replacement mechanism includes a sealing assembly, which is passively contracted when the temperature is lower than -50 degrees Celsius to seal the orifice of the replacement pipe; The sealing assembly includes a telescopic structure and a seal. The telescopic structure is arranged inside the replacement pipe. A seal is arranged at the telescopic end of the telescopic structure. The telescopic structure can passively control the movement of the seal to seal the replacement pipe. The telescopic structure includes a support cylinder. A telescopic space is arranged inside the support cylinder. A telescopic rod is slidably arranged inside the telescopic space. A first elastic member is arranged on one side of the telescopic space. Gas is filled in the other side of the telescopic space. Two circular holes are arranged side by side on the telescopic rod. A first channel is opened in the middle of the telescopic rod. The first channel is communicated with the circular holes. A rubber block is slidably arranged in each circular hole. A second elastic member is arranged between the rubber block and the circular hole. One end of the first elastic member is provided with a ring; The telescopic space includes an installation part and an inflation part separated by a disc part arranged at the end of the telescopic rod. The first elastic member and the ring are both arranged in the installation part. Two circular holes are arranged side by side on the disc part. The two circular holes face the installation part. A first channel is opened on the central axis of the telescopic rod. The first channel is communicated with the two circular holes. A rubber block is slidably arranged in each circular hole. A second elastic member is arranged between the rubber block and the bottom wall of the circular hole. One end of the first elastic member is provided with a ring. The telescopic rod includes a disc part and a round rod part. A plurality of rectangular grooves are evenly opened along the circumferential direction at one end of the rubber block close to the disc part. A first channel is arranged inside the round rod part. The ring has two states during the sliding process of the telescopic rod: The first state is that the gas in the inflation part does not contract due to cold, and the telescopic rod does not move. At this time, the first elastic member presses the ring tightly against the surface of the disc part. The second state is that when storing liquefied natural gas, the ambient temperature around the inflation part drops, the gas in the inflation part contracts due to cold and generates negative pressure. In this way, the telescopic rod moves in the direction close to the inflation part. The first elastic member begins to recover, so that the pressing force of the first elastic member on the ring becomes smaller. At this time, the second elastic member also begins to reset, so that the second elastic member presses the rubber block to move in the circular hole in the direction away from the disc part, so that the rectangular grooves on the rubber block are exposed. In this way, the liquefied natural gas can sequentially pass through the first channel, the circular hole, and the rectangular groove and enter the installation part, so that the negative pressure generated by the inflation part, the extrusion of the first elastic member, and the extrusion of the liquefied natural gas entering the installation part jointly provide the power for the movement of the telescopic rod, facilitating the telescopic rod to drive the seal to move in the direction close to the end of the replacement pipe to seal the end of the replacement pipe.

2. The nitrogen replacement device for an LNG storage tank according to claim 1, characterized in that, The replacement mechanism further includes a replacement component, which includes a fixed exhaust plate and a movable exhaust plate. One movable exhaust plate is arranged on each side of the fixed exhaust plate through a gas guide pipe. A plurality of exhaust holes are evenly arranged on the side of the fixed exhaust pipe away from the tank body and the movable exhaust plate. The fixed exhaust pipe and the movable exhaust plate can evenly spray nitrogen into the interior of the tank body through a pushing mechanism.

3. The nitrogen replacement device for an LNG storage tank according to claim 2, characterized in that, In the vertical direction, the diameters of the plurality of exhaust holes gradually increase from bottom to top.

4. The nitrogen replacement device for an LNG storage tank according to claim 2, characterized in that, The pushing mechanism includes an extension pipe, and a plurality of first reset components are evenly arranged on the outer side of the extension pipe.

5. The nitrogen replacement device for an LNG storage tank according to claim 1, wherein A plurality of delivery pipes are arranged at the bottom of the tank body, and air injection holes are evenly arranged on the delivery pipes.

6. The nitrogen replacement device for an LNG storage tank according to claim 1, characterized in that, A second channel is arranged in the middle of the seal. An annular groove is arranged on the side of the seal close to the replacement pipe. A third channel is also arranged inside the edge of the seal, and the third channel is communicated with the annular groove.

7. The nitrogen replacement device for an LNG storage tank according to claim 1, wherein The sealing component further includes two locking hooks. Second reset components are arranged on the sides of the locking hooks facing away from each other. The locking hooks can limit the seal during sealing.

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