Warming-up method and system for liquefied gas storage tank

Abstract

A warming-up method for a liquefied gas storage tank according to the present invention comprises: a warming-up step of supplying a warming-up gas into an inner container of the liquefied gas storage tank to raise the temperature inside the inner container, the liquefied gas storage tank including the inner container in which a liquefied gas is stored, an outer container surrounding the outside of the inner container and spaced apart from the inner container, and a thermal insulation space between the inner container and the outer container; a purging step of replacing the gas inside the inner container with an inert gas; an aeration step of replacing the gas inside the inner container with air; and a personnel-entry step in which personnel can enter the inner container, wherein the end point of the warming-up step is determined on the basis of the temperature measured at the surface of the inner container.

Description

Warm-up method and system for liquefied gas storage tanks

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2025-0048664 filed on April 15, 2025, and all contents disclosed in the document of said Korean Patent Application are incorporated herein as part of this specification.

[0003] Technology field

[0004] The present invention relates to a method and system for warming up a liquefied gas storage tank, and more specifically, to a method and system for warming up a liquefied gas storage tank capable of shortening the warm-up time of the liquefied gas storage tank.

[0005] Liquefied gas storage tanks store gases in liquid form under cryogenic conditions and serve the role of safely storing, transporting, and supplying them. They are primarily used to store LNG (Liquefied Natural Gas), LPG (Liquefied Petroleum Gas), Liquid Oxygen (LOX), Liquid Nitrogen (LIN), and Liquid Hydrogen (LH2).

[0006] The inspection cycle for such liquefied gas storage tanks is determined by classification societies and international regulations to ensure the safe operation of the vessel and the safe handling of cargo. Regular inspections are to be performed every five years after construction, and if necessary, intermediate inspections may be performed annually or after approximately 2.5 years. In addition, if damage or abnormalities are found in the liquefied gas storage tank, additional inspections may be conducted separately from the regular inspection cycle.

[0007] Thus, there are times when it is necessary for personnel to enter liquefied gas storage tanks directly for inspection, maintenance, or reuse after transport. However, since liquefied gas storage tanks store gas in liquid form at cryogenic temperatures, a warming-up process is required to safely raise the internal temperature from the cryogenic state to ambient temperature and transition to an atmosphere suitable for entry.

[0008] Meanwhile, in highly insulated tanks that store cryogenic liquefied gases (e.g., liquefaction temperature at atmospheric pressure is -163 degrees for LNG and -235 degrees for hydrogen), if the insulation of the liquefied gas storage tank is insufficient and the thermal conductivity to the liquefied gas storage tank is high, the liquefied gas may vaporize and generate BOG (Boil-off Gas). Since the generation of BOG reduces the remaining amount of transported liquefied gas and high-pressure BOG affects the safety of the storage tank, an insulated space filled with insulation material capable of maintaining the internal temperature of the storage tank at a cryogenic state may be formed in the liquefied gas storage tank.

[0009] Generally, the temperature of the middle section of the insulation is measured to determine if it has reached a temperature suitable for human entry. However, because the thermal conductivity of the insulation is low (especially in the case of a vacuum) and the volume of the insulated space is large, it takes a long time to raise the temperature to a level suitable for human entry through a warm-up process. This results in a problem where the warm-up process takes a long time, which reduces the economic efficiency of ship operations.

[0010] The present invention aims to solve the problems of the prior art described above by providing a method and system for warming up a liquefied gas storage tank that can reduce the time required for the warming-up stage of raising the internal temperature of the liquefied gas storage tank.

[0011] A warming method for a liquefied gas storage tank according to one embodiment of the present invention comprises: a warming step of supplying a warming gas into the interior of a liquefied gas storage tank comprising a container in which liquefied gas is stored, an outer container surrounding the exterior of the container and spaced apart from the container, and an insulating space between the container and the outer container to raise the temperature inside the container; a purging step of replacing the gas inside the container with an inert gas; an aeration step of filling the gas inside the container with the atmosphere; and a person entry step that allows a person to enter the interior of the container, and determines the end time of the warming step based on the temperature measured on the surface of the container.

[0012] In one embodiment, the warming gas may be a liquefied gas in a gaseous state.

[0013] In one embodiment, if the measured temperature is higher than a preset temperature at which a person can enter, the warm-up step may be terminated.

[0014] In one embodiment, after the person entry step, an additional warm air supply step of supplying warm air into the interior of the container may be further included.

[0015] In one embodiment, the temperature and flow rate of the warm air supplied in the additional warm air supply step can be controlled by the cold heat from the insulation material of the insulation space.

[0016] In one embodiment, if the cold energy from the insulation material of the insulation space is below a predetermined reference value, the additional warm air supply step can be terminated.

[0017] In one embodiment, the worm air supplied in the additional worm air supply step may be injected through a liquefied gas loading line.

[0018] A warming-up system for a liquefied gas storage tank according to one embodiment of the present invention comprises: a liquefied gas storage tank including a container in which liquefied gas is stored, an outer container arranged to surround the outside of the container and spaced apart from the container, and an insulating space between the container and the outer container; a temperature sensor for measuring the surface temperature of the container, and a time for determining the end of injecting warming gas into the container based on the temperature measured by the temperature sensor.

[0019] In one embodiment, if the measured temperature is higher than a preset temperature at which a person can enter, the injection of the warming gas into the container can be terminated.

[0020] In one embodiment, warm air can be additionally supplied into the container through a liquefied gas loading line.

[0021] The warming method and system for a liquefied gas storage tank according to the present invention can improve the economic efficiency of ship operation by reducing the time required for the warming stage of raising the internal temperature of the liquefied gas storage tank.

[0022] FIG. 1 is a drawing of a liquefied gas storage tank according to the present invention.

[0023] FIG. 2 is a flowchart of a warm-up method for a liquefied gas storage tank according to the present invention.

[0024] Figure 3 is a graph showing the change in internal temperature of the insulation space of a liquefied gas storage tank according to the present invention.

[0025] Figure 4 is a graph showing the change in internal temperature of the insulation space of a liquefied gas storage tank according to the present invention.

[0026] Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that in assigning reference numerals to the components of each drawing, the same components are given the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the embodiments of the present invention, if it is determined that a detailed description of related known components or functions would hinder understanding of the embodiments of the present invention, such detailed description is omitted.

[0027] In addition, terms such as first, second, A, B, (a), (b), etc., may be used when describing the components of the embodiments of the present invention. These terms are intended merely to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by these terms. Where it is stated that a component is "connected," "combined," or "joined" to another component, it should be understood that the component may be directly connected or joined to the other component, but that another component may also be "connected," "combined," or "joined" between each component.

[0028] In this specification, the front-back, left-right, and up-down directions are referred to for convenience of explanation and may be directions orthogonal to one another. However, these directions are determined relatively, and the term "up-down direction" does not necessarily mean a vertical direction.

[0029]

[0030] <Warm-up Method for Liquefied Gas Storage Tanks>

[0031] With reference to FIGS. 1 to 4, a warming-up method (S100) for a liquefied gas storage tank according to the present invention is described. The warming-up method (S100) for a liquefied gas storage tank comprises: a warming-up step (S10) for raising the temperature inside the container (12) of a liquefied gas storage tank (10) comprising a container (12) in which liquefied gas is stored, an outer container (14) that surrounds the outside of the container (12) and is spaced apart from the container (12), and an insulating space (16) between the container (12) and the outer container (14); a purging step (S20) for replacing the gas inside the container (12) with an inert gas; and an aeration step (S30) for filling the gas inside the container (12) with the atmosphere. and includes a person entry step (S40) in which a person can enter the interior of the container (12), and determines the end time of the warm-up step (S10) based on the temperature measured on the surface of the container (12).

[0032] In the present invention, the entire method or system comprising a warm-up step (S10), a purging step (S20), and an aeration step (S30) is referred to as a warm-up method (S100) and a warm-up system. That is, the warm-up method (S100) according to the present invention should not be interpreted as being limited to including only the warm-up step (S10). For example, the warm-up method (system) of a liquefied gas storage tank may be used in terms such as a preparation method (system), post-treatment method (system), non-operation method (system), maintenance method (system), etc. of a liquefied gas storage tank.

[0033] A liquefied gas storage tank (10) may include a container (12) in which liquefied gas is stored, an outer container (14) that surrounds the outside of the container (12) and is spaced apart from the container (12), and an insulating space (16) between the container (12) and the outer container (14). For example, the liquefied gas may be LNG or liquefied hydrogen.

[0034] The insulating material filled in the insulating space (16) may be in the form of powder or beads. For example, the insulating material may include perlite, polyurethane foam, glass wool, and HGMs (hollow glass microspheres). Additionally, the insulating space (16) may be maintained in a vacuum state for excellent thermal insulation performance.

[0035] The warm-up stage (S10) is a process of gradually raising the temperature inside the container (12) of the liquefied gas storage tank (10) by supplying warm-up gas into the container (12). If the temperature changes rapidly from an ultra-low temperature state to the ambient temperature, thermal shock may occur, potentially damaging the liquefied gas storage tank (10). Therefore, the tank must be heated slowly while minimizing thermal stress on the material of the liquefied gas storage tank (10).

[0036] To this end, the warming gas may be a liquefied gas in a gaseous state. For example, if the liquefied gas is liquid hydrogen, gaseous hydrogen may be injected. Or, if the liquefied gas is LNG, NG or methane may be injected. In addition, the warming gas may be gaseous nitrogen or steam. Since the internal pressure may rise as the liquefied gas vaporizes, a pressure regulating valve (not shown) and a ventilation system (not shown) may be used to prevent overpressure.

[0037] However, as explained in the background technology, it may take a considerable amount of time for the internal temperature of the liquefied gas storage tank (10) to gradually rise and reach a level similar to the ambient temperature based on the temperature of the middle part of the insulation material.

[0038] For example, referring to FIG. 3, when the liquefied gas is LNG, the side of the insulation material that is in contact with the LNG (inner container (12)) is -163 degrees, and the outside (outer container (14)) is at room temperature of 40 degrees. When NG is heated and injected into the inner container (12) of the liquefied gas storage tank (10), the temperature inside the inner container (12) of the liquefied gas storage tank (10) rises, and then the temperature on the inner container (12) side propagates to the insulation material, causing the temperature to rise non-linearly. FIG. 3 illustrates the rise in the temperature of the insulation material over time from the lower straight line, and ultimately, the temperature reaches room temperature of 40 degrees as shown by the upper straight line. Conventionally, the warm-up stage (S10) ends at this point.

[0039] However, when the liquefied gas storage tank (10) is a vacuum-insulated tank, the temperature of the container (12) of the liquefied gas storage tank (10) increases rapidly with heating, but because the vacuum-insulated part of the insulation space (16) has low heat conductivity, the temperature of the insulation material rises slowly, so it takes a considerably long time to bring the entire liquefied gas storage tank (10) to room temperature, which causes a problem that reduces the economic efficiency of ship operation.

[0040] To solve this, the present invention does not install a temperature sensor (20) in the middle of the insulation material, but rather installs a temperature sensor (20) on the surface of the container (12) to determine the end point of the warm-up step (S10) based on the temperature measured on the surface of the container (12). In one example, if the temperature measured on the surface of the container (12) is above a preset temperature at which a person can enter, the warm-up step (S10) can be terminated. Therefore, when the surface of the container (12) reaches a temperature at which a person can enter, the warm-up step (S10) can be terminated even if the insulation material has not reached room temperature, thereby shortening the time required for the warm-up step (S10).

[0041] Referring to FIG. 4, the x-axis represents the position in the thickness direction of the insulation material, where 0 on the left is the position of the inner container (12) and 1 on the right is the position of the outer container (14), but these do not represent absolute values. FIG. 4 is an example where the liquefied gas is LNG. At the initial 0 hours, the inside of the inner container (12) is at the temperature of the liquefied gas, and the outside of the outer container (14) is at the temperature of the atmosphere, resulting in a state of thermal equilibrium. When gas above room temperature (80 degrees in FIG. 4) is injected during the warm-up phase (S10), the temperature inside the inner container (12) rises. The temperature of the inner container (12), which has high heat transfer characteristics, rises rapidly, but the temperature of the insulation material rises slowly because the temperature rise of the insulation material is slow. For example, after 5 hours, the temperature of the gas inside the inner container (12) becomes about -70 degrees, the inner container (12) becomes about -100 degrees, and the temperature of the insulation material rises by about 0.1m. After 60 hours, the internal gas of the container (12) and the temperature of the container (12) become 80 degrees, which is the same as the temperature of the supply gas, but the insulation material is calculated to have only partially risen by about 0.3m. Therefore, in the present invention, the warm-up stage (S10) can be terminated when the surface of the container (12) reaches a temperature at which a person can enter, without waiting for the temperature to rise to 0.5m, which is the middle position of the insulation material, thereby shortening the time required in the warm-up stage (S10).

[0042] The preset temperature at which a person can enter may be, for example, 30 to 50 degrees, or, a temperature at which condensation or freezing of the purging gas does not occur during the subsequent purging step (S20).

[0043] The purging step (S20) is a process of inactivating the gas inside the liquefied gas storage tank (10) to create a safe environment. After the warm-up step (S10), since there is a risk of explosion if the combustible gas (e.g., methane, ethylene, hydrogen, etc.) remaining in the container (12) of the liquefied gas storage tank (10) mixes with air, an inert gas (e.g., nitrogen) is injected to dilute and remove the combustible gas. For example, pure nitrogen gas can be injected into the container (12) of the liquefied gas storage tank (10) to discharge the residual gas. Thus, the inside of the liquefied gas storage tank (10) can be in an inert state.

[0044] The aeration step (S30) is a process of filling the inside of the liquefied gas storage tank (10) with air after the purging step (S20). Since there is almost no oxygen inside the liquefied gas storage tank (10) due to the nitrogen injected in the purging step (S20), the inside of the liquefied gas storage tank (10) is converted to an atmospheric state containing oxygen.

[0045] Additionally, the purging gas in the purging step (S20) and the air in the aeration step (S30) can be supplied at a temperature such that the temperature of the container (12) of the liquefied gas storage tank (10) does not drop below the temperature at which a person can enter. That is, the temperature of the container (12) of the liquefied gas storage tank (10) in the purging step (S20) and the aeration step (S30) can be maintained at the temperature at which a person can enter. Therefore, for example, if the warm-up step (S10) is 20 hours, the purging step (S20) is 20 hours, and the aeration step (S30) is 20 hours, a total warm-up effect of 60 hours can be obtained, and the time of the warm-up step (S10) can be drastically reduced.

[0046] After the aeration step (S30), in the person entry step (S30), a person can enter the interior of the container (12) of the liquefied gas storage tank (10) and perform necessary tasks such as inspection and maintenance of the liquefied gas storage tank (10).

[0047] Even after the warm-up phase (S10) is finished, the insulation material of the insulation space (16) is not sufficiently heated, so heat transfer occurs from the container (12) of the liquefied gas storage tank (10) to the insulation material of the insulation space (16) of the liquefied gas storage tank (10), causing the temperature of the container (12) of the liquefied gas storage tank (10) to drop, making it difficult for a person to work.

[0048] To prevent this, in one embodiment, after the person entry step (S30), an additional warm air supply step (S40) may be further included to supply warm air into the container (12) of the liquefied gas storage tank (10). In the additional warm air supply step (S40), warm air may be supplied into the container (12) of the liquefied gas storage tank (10) to such an extent that the temperature of the container (12) of the liquefied gas storage tank (10) does not drop.

[0049] Therefore, in order to shorten the time taken in the warm-up phase (S10) and maintain the temperature inside the container (12) of the storage tank (10), additional warm air is supplied into the container (12) of the liquefied gas storage tank (10) while a person is entering and exiting, thereby maintaining the inside of the container (12) of the liquefied gas storage tank (10) at a temperature where a person can enter.

[0050] In one example, the temperature and flow rate of the warm air supplied in the additional warm air supply step (S40) can be controlled by the cold heat from the insulation material of the insulation space (16). For example, if the amount of heat sent to the insulation material (cold heat from the insulation material) is calculated to be 29,000 W through fluid flow analysis, then if air with a temperature difference of 11 degrees (density 1.2 kg / m³, specific heat 1,000 J / kgK) is injected at a rate of about 8,000 kg / hr, the amount of heat of the supplied warm air is about 29,333 W. Therefore, the temperature of the warm air supplied in the additional warm air supply step (S40) is 11 degrees higher than the internal temperature of the container (12) of the liquefied gas storage tank (10) (for example, if the internal temperature is 30 degrees, it is supplied at 41 degrees), and the flow rate of the warm air can be about 8,000 kg / hr. At this time, 8000 m³ / hr is approximately 2.2 m³ / s, and when injected through a 300A pipe, the outlet flow velocity is about 31 m / s, which is the outlet side and diffuses into the liquefied gas storage tank (10), so the average velocity becomes negligible. Therefore, it is a wind strength that does not cause problems for people to work. In other words, the temperature and flow rate of the warm air can be adjusted so that the amount of heat transferred by the warm air is greater than the cold heat from the cooling of the insulation material. However, this is an exemplary value and may be changed depending on the conditions of the insulation material.

[0051] In one example, if the cooling heat from the insulation material of the insulation space (16) is less than or equal to a predetermined reference value, the additional warm air supply step (S40) can be terminated. If the amount of heat sent to the insulation material is less than the predetermined reference value, it is determined that the temperature drop inside the container (12) of the liquefied gas storage tank (10) is no longer severe due to the cooling heat from the insulation material, and thus the additional warm air supply step (S40) can be terminated. The reference value can be determined in advance through fluid flow analysis.

[0052] The additional warm air supply step (S40) takes place after the person entry step (S30), but can occur simultaneously in terms of time.

[0053] In one example, the warm air supplied in the additional warm air supply step (S40) can be injected into the interior of the container (12) of the liquefied gas storage tank (10) through the liquefied gas loading line (30). Thus, warm air can be supplied by utilizing the existing liquefied gas loading line (30) without a separate additional supply line, and also, warm air can be injected into the bottom of the liquefied gas storage tank (10) to warm up the coldest bottom first.

[0054]

[0055] <Warm-up System for Liquefied Gas Storage Tanks>

[0056] A warming-up system for a liquefied gas storage tank according to the present invention comprises: a liquefied gas storage tank (10) including a container (12) in which liquefied gas is stored, an outer container (14) that surrounds the outside of the container (12) and is spaced apart from the container (12), and an insulating space (16) between the container (12) and the outer container (14); and a temperature sensor (20) that measures the surface temperature of the container (12), and determines the end time of injecting warming gas into the container (12) based on the temperature measured by the temperature sensor (20).

[0057] In one example, in a warming system for a liquefied gas storage tank, if the measured temperature is above a preset temperature at which a person can enter, the injection of warming gas into the container (12) can be stopped. Thus, the time required for warming up can be shortened.

[0058] In one example, additional warm air is supplied into the container (12) through the liquefied gas loading line to prevent the temperature from dropping in the container (12) of the liquefied gas storage tank (10) after warming up.

[0059] The warm-up system for liquefied gas storage tanks is substantially identical in configuration to the warm-up method for liquefied gas storage tanks described earlier.

[0060]

[0061] The foregoing description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains will be able to make various modifications and variations within the scope of the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are intended to explain, not limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by these embodiments. The scope of protection of the present invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present invention.

[0062]

[0063] [Explanation of the symbol]

[0064] 10 liquefied gas storage tanks

[0065] 12 contents

[0066] 14 External container

[0067] 16 Insulated Space

[0068] 20 temperature sensors

[0069] 30 loading line

Claims

1. A warming-up step of supplying a warming gas into the interior of a liquefied gas storage tank comprising a container in which liquefied gas is stored, an outer container arranged to surround the exterior of the container and spaced apart from the container, and an insulating space between the container and the outer container, thereby raising the temperature inside the container; A purging step for replacing the gas inside the above-mentioned container with an inert gas; an aeration step of filling the gas inside the above-mentioned container with the atmosphere; and It includes a person entry step that allows a person to enter the interior of the above-mentioned container, and A method for warming up a liquefied gas storage tank, which determines the end point of the warming-up step based on the temperature measured on the surface of the container.

2. In Claim 1, A method for warming up a liquefied gas storage tank, wherein the above-mentioned warming gas is a liquefied gas in a gaseous state.

3. In Claim 1, A method for warming up a liquefied gas storage tank, wherein the warming-up step is terminated if the above-mentioned measured temperature is greater than or equal to a preset temperature at which a person can enter.

4. In Claim 1, A method for warming up a liquefied gas storage tank, further comprising an additional warm air supply step of supplying warm air into the interior of the container after the above-mentioned person entry step.

5. In Claim 4, A method for warming up a liquefied gas storage tank, wherein the temperature and flow rate of the warm air supplied in the additional warm air supply step are controlled by the cold heat generated by the insulation material of the insulation space.

6. In Claim 4, A method for warming up a liquefied gas storage tank, wherein the additional warm air supply step is terminated when the cold energy from the insulation material of the above-mentioned insulation space is below a predetermined standard value.

7. In Claim 4, A method for warming up a liquefied gas storage tank, wherein the warm air supplied in the above additional warm air supply step is injected through the liquefied gas loading line.

8. A liquefied gas storage tank comprising a container for storing liquefied gas, an outer container arranged to surround the exterior of the container and spaced apart from the container, and an insulating space between the container and the outer container; and It includes a temperature sensor that measures the surface temperature of the above-mentioned container, A warming-up system for a liquefied gas storage tank that determines the end point of injecting warming gas into the interior of the container based on the temperature measured by the temperature sensor.

9. In Claim 8, A warming system for a liquefied gas storage tank that terminates the injection of the warming gas into the interior of the container when the above-mentioned measured temperature is higher than or equal to a preset temperature at which a person can enter.

10. In Claim 8, A warming-up system for a liquefied gas storage tank that additionally supplies warm air into the interior of the container through a liquefied gas loading line.

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