Heat insulation tank body for LNG fuel storage of oversized box ship and working method of heat insulation tank body

Abstract

The invention discloses a heat insulation tank for LNG fuel storage of a super-large box ship and a working method of the heat insulation tank, and relates to the technical field of LNG fuel storage tanks, the heat insulation tank comprises a tank body, the wall body of the tank body is composed of an inner tank layer, a heat insulation interlayer and an outer tank layer, and an emergency pressure relief mechanism is arranged on one side of the upper end face of the tank body; an air pressure sensor is arranged on one side of the upper end face of the emergency pressure relief mechanism, a graded pressure relief device communicated with an inner cavity of the tank body is arranged on the other side of the upper end face of the emergency pressure relief mechanism, three pressure relief cavities are formed in the graded pressure relief device, and an elastic sealing supporting assembly is arranged in each pressure relief cavity. The other side of the upper end face of the tank body is provided with a boil-off gas recycling mechanism, the upper end face of the boil-off gas recycling mechanism is fixedly provided with a pressurizing and cooling device, and the outlet end of the pressurizing and cooling device is provided with a recycled gas discharging pipe; the problems that an LNG fuel storage tank occupies a large effective load space of a ship, the heat insulation efficiency is low, and the evaporation rate is high are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of LNG fuel storage tanks, in particular to an adiabatic tank body for super large container ship LNG fuel storage and a working method thereof. BACKGROUND

[0002] The adiabatic tank body for container ship LNG fuel storage is a key equipment for storing liquefied natural gas (LNG) fuel in a container ship, and its design needs to meet the stringent requirements of LNG low-temperature storage. The tank body is usually of a double-layer structure, with the inner tank directly contacting LNG, generally made of special low-temperature-resistant steel such as Invar steel, which can maintain good performance at an extremely low temperature of about -162°C to prevent brittle fracture of the tank body due to low temperature; the outer tank serves as a protective and supporting role, and high-strength steel is usually used.

[0003] For example, the Chinese authorized patent with publication number CN113639184B, "Ship LNG-CO2 storage system based on LNG cold energy utilization", includes at least two LNG-CO2 storage tanks, a heat exchanger, an LNG combustion application device, a cold and heat management device, a carbon capture device, and a gas compressor. One of the at least two LNG-CO2 storage tanks is a reserved empty tank. The heat exchanger is provided with a liquid LNG inlet and a liquid carbon dioxide outlet on one side, and a liquid LNG outlet and a gaseous carbon dioxide inlet on the other side. All LNG-CO2 common tank bodies are connected to the liquid carbon dioxide outlet of the heat exchanger through a pipeline with a valve, and the pipeline has another valve branch connected to the liquid LNG inlet of the heat exchanger.

[0004] Although the above-mentioned prior art can achieve the storage of liquefied natural gas, the traditional LNG tank body has insufficient adiabatic performance, resulting in a high evaporation rate, increased fuel consumption and safety risks, and the double-layer metal tank body is heavy, occupies the effective payload space of the ship, and has high manufacturing cost. In addition, existing adiabatic materials, such as pearl sand and foam, are prone to aging under long-term ship vibration and low-temperature environment, resulting in adiabatic performance degradation, thus not meeting the existing demand. Therefore, we propose an adiabatic tank body for super large container ship LNG fuel storage and a working method thereof. SUMMARY

[0005] The present application aims to provide an adiabatic tank body for super large container ship LNG fuel storage and a working method thereof to solve the problems of large occupation of the effective payload space of the ship, low adiabatic efficiency, and high evaporation rate of the LNG fuel storage tank as mentioned in the background.

[0006] In order to achieve the above object, the present application provides the following technical scheme: a kind of super large box ship LNG fuel storage heat insulation tank body, including tank body, the wall of the tank body is composed of inner tank layer, heat insulation interlayer and outer tank layer, one side of the upper end surface of the tank body is provided with emergency pressure relief mechanism, one side of the upper end surface of the emergency pressure relief mechanism is provided with air pressure sensor, the other side of the upper end surface of the emergency pressure relief mechanism is provided with the graded pressure relief device being communicated with the inner cavity of tank body, two bursting discs are installed in the lower end inside the graded pressure relief device, three pressure relief cavities are provided in the inside of the graded pressure relief device, the inside of each pressure relief cavity is provided with elastic sealing support assembly, the other side of the upper end surface of the tank body is provided with evaporation gas recovery mechanism, the inside of the evaporation gas recovery mechanism is provided with compressor, cooler, expansion valve and evaporator, the upper end surface of the evaporation gas recovery mechanism is fixedly installed with booster cooling device, the outlet end of the booster cooling device is installed with recovery gas exhaust pipe.

[0007] Preferably, the inner tank layer is made of nickel-based cryogenic alloy material, the outer tank layer is high-strength glass fiber reinforced composite material, and the surface is coated with a bioadhesion-resistant coating, and the heat insulation interlayer is composed of aerogel heat insulation felt inner layer, vacuum heat insulation cavity and lightweight ceramic fiber cotton outer layer.

[0008] Preferably, the inner wall of the heat insulation interlayer is provided with a spiral distributed optical fiber distributed temperature sensor, the inner wall of the inner tank layer is provided with a spiral distributed cooling pipeline, and the lower part of the tank body is provided with a temperature compensation mechanism, the inside of the temperature compensation mechanism is installed with a liquid nitrogen storage tank, and the inlet end of the liquid nitrogen storage tank is connected with the outlet end of the cooling pipeline through a circulating inlet pipe, one side of the liquid nitrogen storage tank is installed with a circulating pump, and one end of the circulating pump is connected with the inlet end of the cooling pipeline through a circulating outlet pipe.

[0009] Preferably, the elastic sealing support assembly includes a sealing plate, and a conical sealing hole is provided at the center position of the sealing plate, a piston is installed at the upper end of the center sealing hole of the sealing plate, a support plate is provided above the piston and is welded and fixed with the graded pressure relief device, four annularly distributed through holes are provided on the outer ring of the support plate, a telescopic rod is installed between the support plate and the piston, a support spring is installed on the outside of the telescopic rod, and the two ends of the support spring are respectively in contact with the support plate and the piston.

[0010] Preferably, the graded pressure relief device is provided with annularly distributed pressure relief holes corresponding to the bursting discs and the upper ends of the lower two layers of pressure relief cavities, and the diameters of the pressure relief holes decrease from bottom to top, and the upper end of the graded pressure relief device corresponding to the upper layer of pressure relief cavities is provided with annularly distributed pressure relief windows.

[0011] Preferably, the inlet end of the compressor is connected to the inner cavity of the tank via a steam inlet pipe, the outlet end of the compressor is connected to the interface end of the cooler via a pipe, the outlet end of the cooler is connected to the interface end of the expansion valve via a pipe, the outlet end of the expansion valve is connected to the interface end of the evaporator via a pipe, and the outlet end of the evaporator is connected to the recovery gas exhaust pipe.

[0012] Preferably, one end of the recovered gas exhaust pipe is connected to a marine gas turbine pipeline and a reliquefaction pipeline via a three-way valve.

[0013] Preferably, support seats are welded and fixed on both sides of the bottom of the tank.

[0014] Preferably, the elastic coefficients of the three support springs decrease sequentially from bottom to top.

[0015] The working method for insulated tanks used for LNG fuel storage on ultra-large container ships includes the following steps: Step 1: Select nickel-based cryogenic alloy plates and form them using a rolling process. Assemble the inner tank using laser welding technology. Evenly lay aerogel insulation felt on the outer surface of the inner tank and fix it with hot melt adhesive to form a high-efficiency thermal barrier layer. Place the inner tank into the outer tank mold to construct the interlayer space and evacuate to 10°C. -3 A vacuum insulation cavity is formed below Pa. Lightweight ceramic fiber cotton is filled on the outside of the vacuum insulation cavity, and the interlayer is sealed after compaction. A high-strength glass fiber reinforced composite material is wound and molded into an outer can. After molding, an anti-bioadhesion coating is applied to the surface of the outer can. Step 2: After the tank is put into use, the fiber optic distributed temperature sensor collects the temperature data of the inner tank layer in real time and constructs a three-dimensional temperature field distribution model. When the temperature of the area exceeds the set threshold, the temperature compensation mechanism is automatically activated, and liquid nitrogen is circulated to cool and reduce the temperature around the inner tank to prevent LNG from evaporating too quickly. Step 3: The LNG vapor gas enters the vapor gas recovery mechanism through the steam inlet pipe, and is then successively pressurized by the compressor, cooled by the cooler, depressurized and cooled by the expansion valve, and further cooled by the evaporator before being delivered to the ship's gas turbine or reliquefaction unit. Step 4: When the pressure inside the tank exceeds 1.2 times the design pressure, the rupture disc of the staged pressure relief device ruptures, triggering staged pressure relief. The pressurized gas is released step by step through the pressure relief chamber, precisely controlling the pressure relief rate to ensure the safety of the tank and the ship.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention employs a three-layer composite structure for the tank body. The inner tank layer uses a nickel-based cryogenic alloy, which meets the requirements for low-temperature resistance and fatigue resistance up to -162℃ while reducing material costs by 30% in thickness. In the insulation interlayer, aerogel insulation felt, with its ultra-low thermal conductivity, covers the outer surface of the inner tank, forming a highly efficient thermal barrier. The vacuum insulation cavity is evacuated to 10...-3 Pa below the vacuum degree, the convection heat transfer of the blocking gas, the lightweight ceramic fiber cotton in the buffer ship vibration at the same time, even if the vacuum layer is damaged, it can maintain a certain heat insulation effect; The outer tank layer uses high-strength glass fiber reinforced composite material, which reduces the weight by 50% on the basis of its own resistance to seawater corrosion and anti-bioadhesion coating, and ensures the stability of the tank body external environment. Through the synergistic effect of each layer, efficient heat insulation, reduction of evaporation rate, reduction of tank weight, improvement of ship cargo carrying capacity, reduction of maintenance cost, and prolongation of tank service life are realized.

[0017] 2、The emergency pressure relief mechanism is provided with three pressure relief cavities in the stepped pressure relief device, when the pressure in the tank exceeds 1.2 times of the design pressure, the bursting disc at the bottom of the stepped pressure relief device is broken instantaneously, the impact force enters the lower pressure relief cavity, and the piston at the center of the sealing plate is impacted, so that the piston moves upward to overcome the elastic support force, and the pressure gas passes through the hole at the center of the sealing plate, then passes through the through hole of the support plate and contacts the piston at the center of the sealing plate of the upper pressure relief cavity, forming stepped pressure relief, and the outer wall of each pressure relief cavity is also provided with annularly distributed pressure relief holes, the diameters of the pressure relief holes of each pressure relief cavity gradually decrease from bottom to top, the emergency pressure relief mechanism can gradually and uniformly release the pressure, accurately control the pressure relief rate, prevent the tank structure from being damaged or secondary safety hazards caused by too fast pressure relief, greatly improve the safety and stability of the LNG tank under extreme pressure working conditions, ensure the safety of the ship and personnel, reduce the potential damage to the tank and surrounding equipment caused by abnormal pressure, and prolong the service life of the equipment.

[0018] 3、The evaporation gas recovery mechanism is provided with a booster cooling device, a compressor, a cooler, an expansion valve and an evaporator are installed inside, LNG evaporation gas enters the compressor from the steam inlet pipe at the top end of the tank cavity, the compressor compresses the evaporation gas to 3-5MPa, which significantly increases the temperature of the gas while increasing the gas pressure, then the high-temperature and high-pressure evaporation gas enters the cooler, and the temperature of the evaporation gas is lowered by heat exchange with the cooling medium, then the cooled evaporation gas enters the expansion valve for pressure and temperature reduction treatment, finally, the low-temperature and low-pressure evaporation gas is further cooled in the evaporator to-120 DEG C, and is finally transported to the ship gas turbine as fuel or enters the reliquefaction device for re-liquefaction storage. The booster cooling process of the mechanism effectively recycles LNG evaporation gas, reduces natural gas waste and emission, reduces ship operating costs, processes the evaporation gas to the working condition parameters suitable for the ship gas turbine or the reliquefaction device, improves energy utilization rate, avoids environmental pollution and safety hazards caused by direct emission of evaporation gas, and improves the green environmental protection performance and safety operation level of the ship.

[0019] 4、The application installs optical fiber distributed temperature sensor on the outer wall of the heat insulation interlayer, collects temperature data of each area of the heat insulation layer in real time, and constructs a three-dimensional temperature field distribution model, when the model shows that the temperature of a certain area exceeds the set threshold and abnormally rises, the system immediately starts the temperature compensation mechanism, the liquid nitrogen in the liquid nitrogen storage tank flows into the spiral cooling pipeline of the inner tank layer under the driving of the circulating pump, absorbs the heat around the inner tank through heat exchange, realizes rapid cooling, and the low-temperature backflow liquid nitrogen returns to the storage tank through the circulating outlet pipe, forming a circulating cooling loop. Realize high-precision and full-coverage monitoring of the temperature of the heat insulation layer, can timely find the local temperature anomaly caused by damage of the heat insulation material, vacuum degree drop and other reasons, and quickly inhibit the temperature rising trend through liquid nitrogen circulating cooling, avoid LNG from evaporating too fast due to too much heat transfer. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a perspective view of the application; Figure 2 is another perspective view of the application; Figure 3 is a perspective view of the tank body cross-sectional structure of the application; Figure 4 is a perspective view of the application Figure 3 is a local enlarged view of area A in the middle; Figure 5 is a perspective view of the hierarchical pressure relief device of the application; Figure 6 is a cross-sectional perspective view of the hierarchical pressure relief device of the application; Figure 7 is a schematic view of the internal structure of the pressurized cooling device of the application.

[0021] In the figure: 1, tank body; 2, emergency pressure relief mechanism; 3, air pressure sensor; 4, hierarchical pressure relief device; 5, evaporation gas recovery mechanism; 6, pressurized cooling device; 7, steam inlet pipe; 8, recovery gas discharge pipe; 9, three-way valve; 10, ship gas turbine pipeline; 11, reliquefier pipeline; 12, support seat; 13, temperature compensation mechanism; 14, liquid nitrogen storage tank; 15, circulating inlet pipe; 16, circulating outlet pipe; 17, inner tank layer; 18, heat insulation interlayer; 19, outer tank layer; 20, aerogel heat insulation felt inner layer; 21, vacuum heat insulation cavity; 22, lightweight ceramic fiber cotton outer layer; 23, optical fiber distributed temperature sensor; 24, cooling pipeline; 25, bursting disc; 26, pressure relief cavity; 27, sealing plate; 28, piston; 29, telescopic rod; 30, support plate; 31, support spring; 32, through hole; 33, compressor; 34, cooler; 35, expansion valve; 36, evaporator; 37, pressure relief hole; 38, pressure relief window. DETAILED DESCRIPTION

[0022] Clearly, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application.

[0023] Please refer to Figures 1-7 The present application provides an embodiment: an adiabatic tank body for LNG fuel storage of a super large box ship, comprising a tank body 1, support seats 12 are welded and fixed on both sides of the bottom of the tank body 1, the wall body of the tank body 1 is composed of an inner tank layer 17, an adiabatic interlayer 18 and an outer tank layer 19, an emergency pressure relief mechanism 2 is arranged on one side of the upper end face of the tank body 1, a gas pressure sensor 3 is arranged on one side of the upper end face of the emergency pressure relief mechanism 2, a graded pressure relief device 4 communicating with the inner cavity of the tank body 1 is arranged on the other side of the upper end face of the emergency pressure relief mechanism 2, two bursting discs 25 are installed at the lower end inside the graded pressure relief device 4, three pressure relief cavities 26 are arranged inside the graded pressure relief device 4, an elastic sealing support assembly is arranged inside each pressure relief cavity 26, a vapor recovery mechanism 5 is arranged on the other side of the upper end face of the tank body 1, a supercharging cooling device 6 is fixedly installed on the upper end face of the vapor recovery mechanism 5, a recovery gas exhaust pipe 8 is installed at the outlet end of the supercharging cooling device 6, and a ship gas turbine pipeline 10 and a reliquefier pipeline 11 are respectively connected to one end of the recovery gas exhaust pipe 8 through a three-way valve 9. The support seat 12 provides stable support for the tank body; the inner tank layer 17, the adiabatic interlayer 18 and the outer tank layer 19 constitute a three-layer protective structure, the inner tank layer directly contains LNG, the adiabatic interlayer blocks heat transfer, and the outer tank layer resists external environmental influences; the gas pressure sensor 3 monitors the pressure in the tank in real time and provides data for the emergency pressure relief mechanism 2; the graded pressure relief device 4 cooperates with the elastic sealing support assembly to realize graded pressure relief when the pressure is abnormal; the vapor recovery mechanism 5 processes the vapor in the tank through the supercharging cooling device 6, and then transports it to the ship gas turbine pipeline 10 or the reliquefier pipeline 11 through the recovery gas exhaust pipe 8, and the three-layer composite structure realizes efficient adiabatic, lightweight and corrosion resistance; gas pressure monitoring and graded pressure relief ensure the safety of the tank pressure; vapor recovery improves energy utilization and reduces emissions, and overall improves the safety, economy and environmental protection of the tank body.

[0024] Please refer to Figure 3, the inner tank layer 17 is made of nickel-based cryogenic alloy material, the outer tank layer 19 is made of high-strength glass fiber reinforced composite material, and the surface is coated with a bio-attachment resistant coating, and the heat insulation layer 18 is composed of an aerogel heat insulation felt inner layer 20, a vacuum heat insulation cavity 21 and a lightweight ceramic fiber cotton outer layer 22. The nickel-based cryogenic alloy of the inner tank layer maintains good mechanical properties at a low temperature of-162℃, and can withstand the low temperature impact of LNG; the high-strength glass fiber reinforced composite material of the outer tank layer provides structural strength with relatively light weight, and the bio-attachment resistant coating prevents marine organisms from attaching to the tank body and affecting the performance of the tank body; in the heat insulation layer, the aerogel heat insulation felt inner layer blocks heat by using ultra-low thermal conductivity, the vacuum heat insulation cavity eliminates gas convection below 10 -3 Pa by being vacuumized to 10

[0025] Please refer to Figure 3 and Figure 4 , the inner wall of the heat insulation layer 18 is provided with a spiral distributed optical fiber distributed temperature sensor 23, the inner wall of the inner tank layer 17 is provided with a spiral distributed cooling pipeline 24, and the lower part of the tank body 1 is provided with a temperature compensation mechanism 13. The temperature compensation mechanism 13 is internally provided with a liquid nitrogen storage tank 14, and the inlet end of the liquid nitrogen storage tank 14 is connected with the outlet end of the cooling pipeline 24 through a circulating inlet pipe 15. A circulating pump is installed on one side of the liquid nitrogen storage tank 14, and one end of the circulating pump is connected with the inlet end of the cooling pipeline 24 through a circulating outlet pipe 16. The optical fiber distributed temperature sensor 23 is based on the principle of Raman scattering, and can collect temperature data of each point of the tank body in real time, and construct a three-dimensional temperature field distribution model. When the model shows that the temperature of a certain area exceeds the set threshold value, the control system starts the circulating pump, the liquid nitrogen in the liquid nitrogen storage tank 14 enters the cooling pipeline 24 through the circulating outlet pipe 16, absorbs the heat around the inner tank through heat exchange, and the warmed liquid nitrogen returns to the storage tank through the circulating inlet pipe 15, forming a cooling cycle. The temperature of the heat insulation layer can be monitored with high precision and full coverage, and temperature abnormalities caused by damage to the heat insulation material, decrease in vacuum degree and the like can be found in time. The liquid nitrogen circulating cooling is started quickly to inhibit the temperature rise, and the evaporation of LNG due to heat transfer is avoided.

[0026] Please refer to Figure 6 , the elastic sealing support assembly includes a sealing plate 27, and a tapered sealing hole is arranged at the center position of the sealing plate 27. A piston 28 is installed at the upper end of the center sealing hole of the sealing plate 27. A support plate 30 is welded and fixed to the piston 28. Four annular through holes 32 are arranged on the outer ring of the support plate 30. A telescopic rod 29 is installed between the support plate 30 and the piston 28. Support springs 31 are installed on the outside of the telescopic rod 29, and the two ends of the support springs 31 are in contact with the support plate 30 and the piston 28, respectively. The elastic coefficients of the three support springs 31 decrease from bottom to top. When the pressure in the tank exceeds the design pressure by 1.2 times, the rupture disc 25 breaks, the pressure gas impacts the lower pressure relief chamber 26, the pressure pushes the piston 28 to overcome the elastic force of the supporting spring 31 to move upward, the gas enters the upper pressure relief chamber through the central hole of the sealing plate 27 and the through hole of the supporting plate 30; the piston in the upper pressure relief chamber continues to move upward under the action of pressure, overcoming the force of the supporting spring with smaller elastic coefficient, realizing staged pressure relief, and the gas is finally discharged through the pressure relief holes.

[0027] Please refer to Figure 1 、 Figure 5 and Figure 6 , the staged pressure relief device 4 is provided with annularly distributed pressure relief holes 37 corresponding to the rupture disc 25 and the upper end of the lower two pressure relief chambers 26, and the diameters of the pressure relief holes 37 decrease from bottom to top, and the upper staged pressure relief device 4 is provided with annularly distributed pressure relief windows 38 corresponding to the upper end position of the upper pressure relief chamber 26; After the rupture disc breaks, the pressure gas is initially released through the pressure relief holes 37 of the lower pressure relief chamber, and as the pressure pushes the piston to open the upper channel, the gas is further released through the upper pressure relief holes 37 with smaller diameters, gradually reducing the pressure; the uppermost pressure relief window 38 serves as the final pressure relief channel, ensuring complete pressure release, and the entire process controls the gas flow and pressure relief speed through the decreasing hole diameters.

[0028] Please refer to Figure 1 and Figure 7 , the inside of the evaporation gas recovery mechanism 5 is provided with a compressor 33, a cooler 34, an expansion valve 35 and an evaporator 36, the inlet end of the compressor 33 is connected with the inner cavity of the tank 1 through the vapor inlet pipe 7, the outlet end of the compressor 33 is connected with the interface end of the cooler 34 through a pipeline, the outlet end of the cooler 34 is connected with the interface end of the expansion valve 35 through a pipeline, the outlet end of the expansion valve 35 is connected with the interface end of the evaporator 36 through a pipeline, and the outlet end of the evaporator 36 is connected with the recovery gas discharge pipe 8; The LNG evaporation gas in the tank enters the compressor 33 through the vapor inlet pipe 7, is compressed to 3-5 MPa, and the temperature significantly rises at the same time of the pressure rising; the high-temperature and high-pressure gas enters the cooler 34, exchanges heat with the cooling medium to reduce the temperature; the cooled gas is depressurized and cooled by the expansion valve 35, and then further cooled to-120℃ by the evaporator 36, and finally discharged through the recovery gas discharge pipe 8, transported to the ship gas turbine or liquefaction device through the three-way valve 9. The complete pressurization and cooling process effectively recovers and utilizes the LNG evaporation gas, reduces the waste and emission of natural gas, and reduces the ship operation cost; the evaporation gas is treated to adapt to the working condition parameters of the equipment, improving the energy utilization rate.

[0029] The working method of the heat-insulated tank body for storing LNG fuel of a super-large box ship, comprising the following steps: Step one, select nickel-based low-temperature alloy plate, adopt coiling process forming, complete the inner tank splicing through laser welding technology, evenly lay aerogel insulation felt on the outer surface of the inner tank, use hot melt adhesive to fix, form high-efficiency thermal barrier layer, put the inner tank into the outer tank mold, build sandwich space, vacuumize to 10 -3 Pa below to form a vacuum insulation chamber 21, fill the outer side of the vacuum insulation chamber 21 with lightweight ceramic fiber cotton, seal the sandwich after compaction, and wrap the outer tank with high-strength glass fiber reinforced composite material to form the outer tank, and then coat the surface of the outer tank with a bioresistant coating; Step two, after the tank is put into use, the optical fiber distributed temperature sensor 23 collects the temperature data of the inner tank layer 17 in real time, and builds a three-dimensional temperature field distribution model. When the regional temperature exceeds the set threshold, the temperature compensation mechanism is automatically started, the liquid nitrogen circulating cooling reduces the temperature around the inner tank, and prevents the LNG from accelerating evaporation; Step three, LNG evaporation gas enters the evaporation gas recovery mechanism 5 through the vapor inlet pipe 7, is pressurized by the compressor 33, cooled by the cooler 34, depressurized and cooled by the expansion valve 35, and further cooled by the evaporator 36, and then is delivered to the ship gas turbine or liquefaction device; Step four, when the pressure in the tank exceeds 1.2 times the design pressure, the rupture disc 25 of the stepped pressure relief device 4 breaks, triggering the stepped pressure relief, and the pressure gas is released step by step through the pressure relief chamber 26, the pressure relief rate is accurately controlled, and the safety of the tank and the ship is ensured.

[0030] It will be obvious to a person skilled in the art that the application is not limited to the details of the above-described exemplary embodiments, but that the application can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the application being defined by the appended claims rather than by the above description, and it is therefore intended that all changes and modifications that fall within the meaning and range of equivalency of the elements of the claims are encompassed by the application. Any reference signs in the claims should not be considered as limiting the claims involved.

Claims

1. An insulated tank for storing LNG fuel in ultra-large container ships, comprising a tank body (1), characterized in that: The tank body (1) is composed of an inner tank layer (17), an insulation interlayer (18), and an outer tank layer (19). An emergency pressure relief mechanism (2) is provided on one side of the upper end face of the tank body (1). A pressure sensor (3) is provided on one side of the upper end face of the emergency pressure relief mechanism (2). A graded pressure relief device (4) communicating with the inner cavity of the tank body (1) is provided on the other side of the upper end face of the emergency pressure relief mechanism (2). Two rupture discs (25) are installed at the lower end of the inside of the graded pressure relief device (4). 4) has three pressure relief chambers (26) inside. Each pressure relief chamber (26) is equipped with an elastic sealing support assembly. An evaporation gas recovery mechanism (5) is provided on the other side of the upper end face of the tank body (1). The evaporation gas recovery mechanism (5) is equipped with a compressor (33), a cooler (34), an expansion valve (35) and an evaporator (36). A pressurization and cooling device (6) is fixedly installed on the upper end face of the evaporation gas recovery mechanism (5). A recovery gas pipe (8) is installed at the outlet end of the pressurization and cooling device (6).

2. The insulated tank for storing LNG fuel in ultra-large container ships according to claim 1, characterized in that: The inner tank layer (17) is made of nickel-based low-temperature alloy, the outer tank layer (19) is made of high-strength glass fiber reinforced composite material, and the surface is coated with an anti-bioadhesion coating. The heat insulation interlayer (18) is composed of an inner layer (20) of aerogel heat insulation felt, a vacuum heat insulation cavity (21) and an outer layer (22) of lightweight ceramic fiber cotton.

3. The insulated tank for storing LNG fuel in an ultra-large container ship according to claim 2, characterized in that: The inner wall of the insulation interlayer (18) is provided with a spirally distributed fiber optic temperature sensor (23), the inner wall of the inner tank layer (17) is provided with a spirally distributed cooling pipe (24), the bottom of the tank body (1) is provided with a temperature compensation mechanism (13), the inside of the temperature compensation mechanism (13) is equipped with a liquid nitrogen storage tank (14), and the inlet end of the liquid nitrogen storage tank (14) is connected to the outlet end of the cooling pipe (24) through a circulation inlet pipe (15). A circulation pump is installed on one side of the liquid nitrogen storage tank (14), and one end of the circulation pump is connected to the inlet end of the cooling pipe (24) through a circulation outlet pipe (16).

4. The insulated tank for storing LNG fuel in an ultra-large container ship according to claim 3, characterized in that: The elastic sealing support assembly includes a sealing plate (27), and a tapered sealing hole is provided at the center of the sealing plate (27). A piston (28) is installed at the upper end of the central sealing hole of the sealing plate (27). A support plate (30) is provided above the piston (28) and welded and fixed to the graded pressure relief device (4). The outer ring of the support plate (30) is provided with four annularly distributed through holes (32). A telescopic rod (29) is installed between the support plate (30) and the piston (28). A support spring (31) is installed on the outside of the telescopic rod (29), and the two ends of the support spring (31) are in contact with the support plate (30) and the piston (28) respectively.

5. The insulated tank for storing LNG fuel in an ultra-large container ship according to claim 4, characterized in that: The graded pressure relief device (4) is provided with annularly distributed pressure relief holes (37) at the upper end of the rupture disc (25) and the two lower pressure relief chambers (26), and the diameter of the pressure relief holes (37) decreases from bottom to top. The graded pressure relief device (4) is provided with annularly distributed pressure relief windows (38) at the upper end of the upper pressure relief chamber (26).

6. The insulated tank for storing LNG fuel in ultra-large container ships according to claim 5, characterized in that: The inlet end of the compressor (33) is connected to the inner cavity of the tank (1) through a steam inlet pipe (7). The outlet end of the compressor (33) is connected to the interface end of the cooler (34) through a pipe. The outlet end of the cooler (34) is connected to the interface end of the expansion valve (35) through a pipe. The outlet end of the expansion valve (35) is connected to the interface end of the evaporator (36) through a pipe. The outlet end of the evaporator (36) is connected to the recovery gas exhaust pipe (8).

7. The insulated tank for storing LNG fuel in ultra-large container ships according to claim 6, characterized in that: One end of the recovered gas pipe (8) is connected to the ship gas turbine pipeline (10) and the reliquefaction pipeline (11) respectively via a three-way valve (9).

8. The insulated tank for storing LNG fuel in ultra-large container ships according to claim 1, characterized in that: Support seats (12) are welded and fixed on both sides of the bottom of the tank (1).

9. An insulated tank for storing LNG fuel in an ultra-large container ship according to claim 4, characterized in that: The elastic coefficients of the three support springs (31) decrease sequentially from bottom to top.

10. The working method of the insulated tank for LNG fuel storage in ultra-large container ships according to claim 7, characterized in that: Includes the following steps: Step 1: Select nickel-based low-temperature alloy plates, roll them into shape, and complete the inner tank splicing through laser welding technology. Spread aerogel insulation felt evenly on the outer surface of the inner tank and fix it with hot melt adhesive to form a high-efficiency thermal barrier layer. Place the inner tank into the outer tank mold to build a sandwich space. Evacuate to below 10⁻³Pa to form a vacuum insulation cavity (21). Fill the outside of the vacuum insulation cavity (21) with lightweight ceramic fiber cotton, compact it and seal the sandwich layer. Use high-strength glass fiber reinforced composite material to wind and form the outer tank. After forming, coat the surface of the outer tank with an anti-bioadhesion coating. Step 2: After the tank is put into use, the fiber optic distributed temperature sensor (23) collects the temperature data of the inner tank layer (17) in real time and constructs a three-dimensional temperature field distribution model. When the temperature of the area exceeds the set threshold, the temperature compensation mechanism is automatically activated, and liquid nitrogen is circulated to cool and reduce the temperature around the inner tank to prevent LNG from evaporating faster. Step 3: The LNG vapor gas enters the vapor gas recovery mechanism (5) through the steam inlet pipe (7), and is successively pressurized by the compressor (33), cooled by the cooler (34), depressurized and cooled by the expansion valve (35), and further cooled by the evaporator (36) before being transported to the ship's gas turbine or reliquefaction unit. Step 4: When the pressure inside the tank exceeds 1.2 times the design pressure, the rupture disc (25) of the staged pressure relief device (4) ruptures, triggering staged pressure relief. The pressurized gas is released step by step through the pressure relief chamber (26), precisely controlling the pressure relief rate and ensuring the safety of the tank and the ship.

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