Operation method of Membrane type Liquid Hydrogen Storage Tank

Abstract

The present invention provides a method for operating a membrane-type liquid hydrogen storage tank, wherein the internal space is divided into a storage space in which liquid hydrogen is stored, a primary insulation space formed between the primary and secondary walls, and a secondary insulation space formed between the secondary walls and the hull, wherein a secondary barrier and a primary barrier made of metal material are sequentially stacked and arranged on the inner wall surface of the hull; a primary insulation space formed between the primary barrier and the secondary barrier; and a secondary insulation space formed between the secondary barrier and the hull. The method comprises: a vacuum forming step of forming a vacuum in the storage space, the primary insulation space, and the secondary insulation space; a liquid hydrogen loading step of loading liquid hydrogen into the storage space; and a helium gas injection step of injecting helium gas as an inert gas into the primary insulation space and the secondary insulation space.

Description

Technology Field

[0001] The present invention relates to a method of operating a membrane-type liquid hydrogen storage tank, and more specifically, to an invention regarding gas exchange and the operation of an inert gas in the internal space of a membrane-type liquid hydrogen storage tank for storing and transporting liquid hydrogen in an ultra-low temperature environment of -253℃. Background Technology

[0002] Generally, the transportation of hydrogen can be broadly classified into inland and maritime transport. Inland hydrogen transportation can be carried out using pipelines, dedicated transport vehicles, or railways, while maritime hydrogen transportation can be achieved via vessels equipped with specialized storage facilities.

[0003] For efficient transport at sea, it may be desirable to store and transport gaseous hydrogen in a liquid state by cooling it to cryogenic temperatures and / or pressurizing it. Additionally, membrane-type storage tanks can be considered as a liquid hydrogen storage technology applicable to enable long-term transport over the sea.

[0004] Typically, membrane-type storage tanks are tanks manufactured as a single unit with the hull structure, and have a double insulation structure in which a primary barrier and a secondary barrier are installed in two layers on the inner wall of the hull, and an insulation space is formed between the primary barrier and the secondary barrier and between the secondary barrier and the hull.

[0005] A membrane-type storage tank composed of double thin barriers (membranes) can be divided into a storage space where liquefied gas is stored, a primary insulation space formed between the primary barrier and the secondary barrier, and a secondary insulation space formed between the secondary barrier and the hull. Here, the storage space can be referred to as SS (Storage Space), the primary insulation space as IBS (Inter Barrier Space), and the secondary insulation space as IS (Insulation Space).

[0006] The gas exchange process for the internal space of a membrane-type storage tank, which is divided into a storage space (SS), a primary insulation space (IBS), and a secondary insulation space (IS), is an essential element in terms of the operation of storage containers for the storage and transportation of liquefied gas.

[0007] For example, when loading liquefied gas into a membrane-type storage tank, gas replacement work must be performed inside the storage tank, taking into account that the liquefied gas is a flammable substance at extremely low temperatures.

[0008] Generally, the method for replacing the gas inside a liquefied gas storage tank includes drying, which involves blowing dry air into the tank to remove moisture; inerting, which involves supplying inert gas into the tank to remove oxygen and eliminate the risk of explosion; gasssing-up, which involves supplying relatively warm gaseous liquefied gas (hydrocarbon gas) into the tank to remove carbon dioxide components contained in the inert gas; and cool-down, which involves cooling the inside of the tank using a small amount of liquefied gas. Only after these replacement operations are performed can liquefied gas be supplied into the storage tank to carry out loading operations.

[0009] In addition, when unloading liquefied gas inside a liquefied gas storage tank, a process of warming up by injecting warm liquefied gas into the storage tank to vaporize all remaining liquefied gas inside the tank, an inerting process of injecting inert gas into the storage tank, and an aerating process of injecting air containing oxygen when human entry is required (e.g., maintenance) may be performed.

[0010] In addition, inert gas may be injected at a predetermined pressure into the primary insulation space (IBS) and secondary insulation space (IS) of the membrane-type storage tank for the purpose of preventing the risk of explosion and removing moisture, etc. within the space.

[0011] Nitrogen gas is the most commonly used inert gas in the gas exchange process for the internal space of membrane-type storage tanks.

[0012] Meanwhile, membrane storage tanks, which are atmospheric tanks, generally limit the increase in internal pressure to within 0.7 barg, except in cases where the maximum design vapor pressure is particularly high, and hydrogen is stored in a liquefied state at -253°C under that pressure environment.

[0013] As such, since liquid hydrogen has a very low boiling point among various liquefied gases, if nitrogen gas is used as an inert gas for gas exchange in membrane-type storage tanks, the problem of nitrogen gas condensing and solidifying occurs due to the low storage temperature environment of liquid hydrogen.

[0014] In addition, if gas exchange in each space inside the membrane-type storage tank does not proceed smoothly, not only nitrogen gas but also components such as oxygen and moisture may condense and solidify, raising serious concerns that it may cause problems in the operation of the storage facility. The problem to be solved

[0015] The present invention aims to solve the problems of the aforementioned prior art and provides a method for operating a membrane-type liquid hydrogen storage tank in which gas replacement in the internal space of the tank can be easily performed without the phenomenon of inert gas, oxygen, or moisture condensing and solidifying, even in an extremely low storage temperature environment of liquid hydrogen that is liquefied at -253℃. means of solving the problem

[0016] According to one aspect of the present invention for achieving the above objective, a method of operating a membrane-type liquid hydrogen storage tank may be provided, wherein a secondary barrier and a primary barrier made of metal material are sequentially stacked and arranged on the inner wall surface of the hull, and a storage space in which liquid hydrogen is stored; a primary insulation space formed between the primary barrier and the secondary barrier; and a secondary insulation space formed between the secondary barrier and the hull, wherein the internal space is divided into: a vacuum forming step of forming a vacuum in the storage space, the primary insulation space, and the secondary insulation space; a liquid hydrogen loading step of loading liquid hydrogen into the storage space; and a helium gas injection step of injecting helium gas as an inert gas into the primary insulation space and the secondary insulation space.

[0017] In the above vacuum formation step, the vacuum formation operation can be performed sequentially from the outermost secondary insulation space to the primary insulation space and the storage space.

[0018] In the above vacuum formation step, a vacuum is formed until the internal pressure of the secondary insulation space becomes a first vacuum pressure, a vacuum is formed until the internal pressure of the primary insulation space becomes a second vacuum pressure, and a vacuum is formed until the internal pressure of the storage space becomes a third vacuum pressure, provided that the magnitude of the vacuum pressure may be formed in the order of first vacuum pressure < second vacuum pressure < third vacuum pressure.

[0019] In the above liquid hydrogen loading step, a cool-down operation may be performed by spraying a small amount of liquid hydrogen into the storage space to cool it before the liquid hydrogen is loaded into the storage space.

[0020] As the above storage space is formed as a vacuum, the process of removing moisture by supplying dry air into the storage space, removing oxygen by supplying an inert gas into the storage space, and removing the inert gas by supplying a hydrocarbon gas into the storage space may be omitted as a preliminary operation prior to loading liquid hydrogen into the storage space.

[0021] In the helium gas injection step above, the operation of injecting helium gas into the first insulation space may be performed first, and then the operation of injecting helium gas into the second insulation space may be performed.

[0022] In the helium gas injection step, helium gas is injected until the internal pressure of the first insulation space reaches the first internal pressure, and helium gas is injected until the internal pressure of the second insulation space reaches the second internal pressure, wherein the pressure magnitude can be formed in the order of second internal pressure < first internal pressure < storage pressure of liquid hydrogen filled in the storage space.

[0023] A device for monitoring and controlling the pressure state of the storage space, the primary insulation space, and the secondary insulation space may be provided during the vacuum forming step and the helium gas injection step. Effects of the invention

[0024] The method of operating a membrane-type liquid hydrogen storage tank according to the present invention has the effect of enabling the performance of gas replacement work, which is essential for tank operation, without fear of conventional condensation and solidification problems by using helium gas, which has a boiling point lower than that of liquid hydrogen, as an inert gas.

[0025] In addition, while the use of large quantities of helium as an inert gas is unavoidable, the present invention enables limited use of helium gas by combining it with a vacuum method, thereby having the effect of reducing the cost associated with helium gas usage.

[0026] The effects of the present invention are not limited to those described above, and other unmentioned effects of the present invention will be clearly understood from the description below. Brief explanation of the drawing

[0027] FIG. 1 is a schematic diagram showing the insulation structure of a membrane-type liquid hydrogen storage tank according to the present invention. FIG. 2 is a flowchart illustrating the operation method of a membrane-type liquid hydrogen storage tank according to the present invention. FIG. 3 is a schematic diagram showing the arrangement structure of a ship including a membrane-type liquid hydrogen storage tank according to the present invention. Specific details for implementing the invention

[0028] In order to fully understand the present invention, the operational advantages of the present invention, and the objectives and effects achieved by the implementation of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

[0029] The details depicted in the drawings attached to this specification are schematic drawings intended to facilitate the explanation of embodiments of the invention and may differ somewhat from the actual forms implemented; furthermore, the size of each component shown in the drawings may be exaggerated or reduced for illustrative purposes and does not imply the actual applicable size.

[0030] Furthermore, the terms used in this specification are used merely to describe specific embodiments and are not intended to limit the invention. For example, in this specification, the term "comprising" a component means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0031] Furthermore, the statement that one component is 'connected' to another component includes not only direct but also indirect connections, and should be understood as implying that other components may exist between the two components. A singular expression may be interpreted to include a plural expression unless the context clearly indicates otherwise.

[0032] The present invention will be described in detail below by explaining preferred embodiments with reference to the attached drawings. The embodiments described below are provided to enable those skilled in the art to easily understand the technical concept of the present invention and are not intended to limit the present invention.

[0034] FIG. 1 is a schematic diagram showing the insulation structure of a membrane-type liquid hydrogen storage tank according to the present invention, and FIG. 2 is a flowchart showing the method of operation of a membrane-type liquid hydrogen storage tank according to the present invention. FIG. 3 is a schematic diagram showing the arrangement structure of a ship including a membrane-type liquid hydrogen storage tank according to the present invention.

[0035] Referring to FIG. 1, the membrane-type liquid hydrogen storage tank according to the present invention has a double insulation structure in which a secondary barrier (20) and a primary barrier (10) made of metal are sequentially arranged in two layers on the inner wall surface of the hull (H), and an insulation space is formed between the primary barrier (10) and the secondary barrier (20) and between the secondary barrier (20) and the hull (H).

[0036] The primary insulation space formed between the primary barrier (10) and the secondary barrier (20) can be referred to as the Inter Barrier Space (IBS), and the secondary insulation space formed between the secondary barrier (20) and the hull (H) can be referred to as the Insulation Space (IS). In each insulation space (IBS, IS), an insulating material to achieve insulation performance may be filled in the form of foam or powder, or manufactured and arranged in the form of an insulation panel or an insulation box.

[0037] That is, similar to the structure of a conventional membrane-type storage tank, the membrane-type liquid hydrogen storage tank according to the present invention can be divided into a storage space (SS) in which liquid hydrogen is stored, and a primary insulation space (IBS) and a secondary insulation space (IS) arranged outwardly from the storage space (SS), and the gas exchange process for each space is an essential element in terms of the operation of the liquid hydrogen storage tank.

[0038] Meanwhile, the liquid hydrogen intended for transport in this invention has a boiling point of -253°C, and even when compared to the boiling point of -167°C of the currently most widely used liquefied natural gas (LNG), a storage environment must be established at a very low temperature.

[0039] However, as explained in the background technology, using nitrogen gas as an inert gas in extremely low temperature environments such as -253℃ can cause many problems in the operation of membrane-type storage tanks. Accordingly, the present invention proposes a technology that can easily perform gas replacement work in the internal space of a membrane-type storage tank while solving the problem of inert gas, oxygen, and moisture condensing and solidifying in an extremely low storage temperature environment of liquid hydrogen.

[0040] To solve the above technical problem, the present invention proposes a method of using helium gas (boiling point: -269℃), which has a boiling point lower than that of hydrogen, as an inert gas.

[0041] Furthermore, based on the recognition of the problem that economical operation of a storage tank cannot be achieved solely by using helium as an inert gas because helium (He) exists in only minute quantities in the air, the present invention proposes a method of using 'vacuum' and 'helium gas' in parallel in relation to gas exchange and inert gas operation of a membrane-type liquid hydrogen storage tank.

[0043] Hereinafter, with reference to FIG. 2, a method of operating a membrane-type liquid hydrogen storage tank according to the present invention, more specifically a method of performing gas exchange in the internal space of a membrane-type liquid hydrogen storage tank by using vacuum and helium gas in parallel, will be described in more detail.

[0044] The method of operating a membrane-type liquid hydrogen storage tank according to the present invention can be broadly divided into three steps: a vacuum forming step (S100) for forming a vacuum in each space (SS, IBS, IS) formed inside the membrane-type liquid hydrogen storage tank; a liquid hydrogen loading step (S200) for loading liquid hydrogen into the storage space (SS); and a helium gas injection step (S300) for injecting helium gas as an inert gas into the insulation space (IBS, IS).

[0045] The vacuum formation step (S100) is a step of forming a vacuum in each space (SS, IBS, IS) partitioned inside a membrane-type liquid hydrogen storage tank, and the vacuum formation operation is performed individually for each space (SS, IBS, IS), but the vacuum formation operation can be performed sequentially in the order of the second insulation space (IS) located at the outermost end, the first insulation space (IBS), and the storage space (SS).

[0046] In this case, in the case of vacuum pressure, the secondary adiabatic space (IS) can be formed to be the lowest and the storage space (SS) to be the highest. That is, the pressure magnitude of each space can be formed in the order of IS < IBS < SS.

[0047] And the vacuum formation process for each space (SS, IBS, IS) can be carried out until the components (oxygen, moisture, etc.) required to be removed from the gas present inside the space come within an acceptable range.

[0048] If we look specifically at the sequential execution process of the vacuum formation step (S100),

[0049] (1) First, a vacuum is created in the secondary adiabatic space (IS) using a vacuum pump (P, see FIG. 3). At this time, the internal pressure of the secondary adiabatic space (IS) is the first vacuum pressure (P V,IS A vacuum is formed until it becomes ), and the first vacuum pressure can be determined within a range that satisfies the oxygen concentration in the secondary adiabatic space (IS) below a certain level (allowable value) and the dew point below a certain level (allowable value).

[0050] (2) Next, using a vacuum pump (P, see FIG. 3), the internal pressure of the primary adiabatic space (IBS) is reduced to a second vacuum pressure (P V,IBS A vacuum is formed until ). The second vacuum pressure can be determined within a range that satisfies a level below the allowable limit for the oxygen concentration or dew point within the primary adiabatic space (IBS), and the second vacuum pressure is formed to be greater than the aforementioned first vacuum pressure (P V,IS <P V,IBS It is characterized by becoming ).

[0051] (3) Finally, using a vacuum pump (P, see FIG. 3), the internal pressure of the storage space (SS) is reduced to a third vacuum pressure (P V,SS A vacuum is formed until ). The third vacuum pressure can be determined within a range that satisfies a level below the allowable limit for the oxygen concentration or dew point within the storage space (SS), and the third vacuum pressure is formed to be greater than the aforementioned second vacuum pressure (P V,IBS <P V,SS )becomes.

[0052] Accordingly, after the above processes (1) to (3) are completed, the vacuum pressure magnitude of each space (SS, IBS, IS) is "P V,IS <P V,IBS <P V,SS It can be formed in this order.

[0053] In the case of membrane-type storage tanks, the primary and secondary barriers serve only as sealing mechanisms, while structural support is provided by an insulation system (in the form of insulation materials, insulation boxes, insulation panels, etc.) placed in the insulation space. In other words, membrane-type storage tanks have a form in which a thin metal barrier called a membrane is placed on a relatively rigid surface. If the membrane is lifted away from the surface, it can not only cause structural problems in the storage tank but also lead to significant issues with the airtightness of the liquefied gas stored inside.

[0054] In order to prevent the above-mentioned problems, the present invention prevents the first and second barriers (10, 20) from being lifted from the surface of the insulation system in which they are respectively placed by sequentially forming pressure in each space (IS, IBS, SS). In addition, the order of forming pressure for each space (IS, IBS, SS) is also for the same reason.

[0055] Meanwhile, since the expression "vacuum pressure" mentioned above refers to negative pressure, a higher vacuum pressure does not mean a larger vacuum. For example, P V,IS The pressure is -500 mbarg, P V,IBS The pressure is -400 mbarg, and P V,SS The pressure can be formed sequentially with a magnitude of -300 mbarg.

[0056] In addition, in order to prevent the pressure (vacuum pressure) of each space (SS, IBS, IS) from being reversed while the above series of processes is performed, a device for monitoring the pressure of each space (SS, IBS, IS) and a control device having a pressure control function may be further provided.

[0057] When the vacuum formation of each space (SS, IBS, IS) is completed by performing the vacuum formation step (S100), a liquid hydrogen loading step (S200) can be performed in which liquid hydrogen is loaded into the storage space (SS) after cooling by injecting a small amount of liquid hydrogen into the storage space (SS).

[0058] Typically, before loading liquefied gas into a membrane-type storage tank, a drying process must be performed by supplying dry air into the tank to remove moisture (drying), supplying inert gas to remove oxygen (inerting), supplying hydrocarbon gas produced by vaporizing the liquefied gas to remove inert gas (gassing-up), and then cooling down the tank by injecting a small amount of liquefied gas into the storage tank.

[0059] However, according to the present invention, in the process of forming a vacuum in a storage space (SS) where liquid hydrogen is stored, major gases constituting air, such as oxygen and nitrogen, are first removed, and subsequently, moisture and other gases are also discharged, so there is almost no oxygen and moisture present in the storage space (SS) where the vacuum formation is completed. Furthermore, as described above, the present invention forms a vacuum in each space (SS, IBS, IS) including the storage space (SS) within a range where the oxygen concentration present inside satisfies the condition of being below the allowable limit and the dew point satisfies the condition of being below the allowable limit; thus, the storage space (SS) where the vacuum formation is completed can be considered to already satisfy the conditions for oxygen and moisture for the shipment of liquid hydrogen.

[0060] Accordingly, according to the present invention, among the preliminary operations previously performed for the shipment of liquefied gas, it is possible to omit the process of removing moisture by supplying dry air, the process of removing oxygen by supplying inert gas, and the process of removing inert gas by supplying hydrocarbon gas.

[0061] That is, according to the method of operating a membrane-type liquid hydrogen storage tank according to the present invention, after the vacuum formation step (S100), the cool-down process of cooling the tank and the process of loading liquid hydrogen can be performed immediately without the need to inject a separate inert gas into the storage space (SS).

[0062] When the liquid hydrogen loading stage (S200) is completed, an inert gas is injected into each space to replace it, in sequence from the first insulation space (IBS) to the second insulation space (IS). That is, a procedure to inject helium gas to replace the first and second insulation spaces (IBS, IS) according to the target pressurization level may be carried out, and here, as the inert gas, helium gas may be used considering the cryogenic (-253℃) liquid hydrogen storage environment as described above.

[0063] More specifically, in the helium gas injection step (S300), the operation of injecting helium gas into the primary adiabatic space (IBS) is performed first, contrary to the order of forming the vacuum, and then the operation of injecting helium gas into the secondary adiabatic space (IS) can be performed. The reason for performing the helium gas injection sequentially from the primary adiabatic space (IBS) to the secondary adiabatic space (IS) is to prevent a situation in which the pressure of each adiabatic space (IBS, IS) is reversed, as the pressure in the space increases as helium gas is injected.

[0064] The helium gas injected into the primary insulation space (IBS) and the secondary insulation space (IS) maintains the pressure in each space at a set level to ensure the stability of the storage tank and also serves to prevent the inflow of oxygen that forms explosive conditions.

[0065] In the above liquid hydrogen loading step (S200), the storage pressure of the liquid hydrogen filled in the storage space (SS) is P V When given that, the first internal pressure (P), which is the internal pressure of the primary adiabatic space (IBS) filled with helium gas, IG,IBS ) is the storage pressure of liquid hydrogen (PV It can be formed to be smaller than ). In addition, the second internal pressure (P), which is the internal pressure of the secondary adiabatic space (IS) filled with helium gas, IG,IS ) is the first internal pressure (P IG,IBS It can be formed smaller than ).

[0066] In other words, the injection pressure of helium gas can be higher in the primary adiabatic space (IBS) than in the secondary adiabatic space (IS). Consequently, the magnitude of the pressure in each space (IS, IBS, SS) is P IG,IS <P IG,IBS <P V It can be formed in this order, which is to prevent the first and second barriers (10, 20), which are composed of thin membranes as described above, from being lifted from the insulation system.

[0068] FIG. 3 schematically illustrates the arrangement structure of a ship including a membrane-type liquid hydrogen storage tank according to the present invention.

[0069] Referring to FIG. 3, at least one membrane-type liquid hydrogen storage tank (T) according to the present invention may be disposed inside the hull of a ship, and a vacuum pump (P) for removing air inside the tank to form a vacuum may be provided at the rear of the membrane-type liquid hydrogen storage tank (T), and a helium storage tank (HT) for storing helium supplied to an insulating space (IBS, IS) inside the membrane-type liquid hydrogen storage tank (T).

[0070] In cases where two or more membrane-type liquid hydrogen storage tanks (T) are provided, as shown in the drawing, a vacuum pump (P) and a helium storage tank (HT) may each be provided so that the multiple tanks are operated in common through one device, but it is also possible to provide a vacuum pump (P) and a helium storage tank (HT) to correspond to each of the multiple tanks so that each tank is operated individually.

[0072] As explained above, the method of operating a membrane-type liquid hydrogen storage tank according to the present invention is such that gas replacement in large spaces is performed using a vacuum due to the high consumption of inert gas, while gas replacement in limited spaces can be handled with a small amount of helium. Here, large spaces refer to storage spaces (SS) that must be filled with liquid hydrogen, and limited spaces refer to insulation spaces (IBS, IS) filled with insulating materials that have little to no empty space inside.

[0073] In the present invention, when using helium as an inert gas to prevent condensation and solidification caused by the extremely low boiling point of liquid hydrogen intended for transport, the use of a large amount is unavoidable; however, the present invention can achieve the effect of reducing costs by configuring a system that enables the limited use of helium gas by combining a vacuum method.

[0074] In addition, for the operation of the membrane-type liquid hydrogen storage tank as described above, the membrane-type liquid hydrogen storage tank according to the present invention is characterized in that the double barriers (10, 20) are all made of metal, and may further include a control device and a monitoring device having a pressure control function so that the pressure change in each space (SS, IBS, IS) does not exceed the operating standard or the pressure in each space (SS, IBS, IS) does not reverse during the gas exchange process.

[0075] The present invention is proposed to be preferably applied to membrane-type storage tanks for storing liquid hydrogen with an extremely low boiling point, but the basic concept of the present invention can, of course, be applied to membrane-type storage tanks for storing various liquid gases that can be liquefied at low temperatures and stored and transported, such as LPG (Liquefied Petroleum Gas), LEG (Liquefied Ethane Gas), Liquefied Ethylene Gas, and Liquefied Propylene Gas, in addition to liquid hydrogen.

[0076] In addition, the term 'ship' in the present invention can include not only ships with their own propulsion but also the concept of offshore structures floating on the sea, provided that the structure is capable of being equipped with a membrane-type storage tank for storing liquefied gas inside the hull.

[0077] It is obvious to those skilled in the art that the present invention is not limited to the described embodiments and can be modified and varied in various ways without departing from the spirit and scope of the invention. Accordingly, such modifications or variations should be deemed to fall within the scope of the claims of the present invention. Explanation of the symbols

[0078] 10: 1st Barrier 20: Second Barrier SS: Storage space IBS: Primary insulation space IS: Secondary insulation space S100: Vacuum formation step S200: Liquid hydrogen shipment stage S300: Helium gas injection step

Claims

Claim 1 A method of operating a membrane-type liquid hydrogen storage tank, wherein the internal space is divided into: a storage space in which liquid hydrogen is stored, wherein a secondary barrier and a primary barrier made of metal are sequentially stacked and arranged on the inner wall surface of the hull; a primary insulation space formed between the primary barrier and the secondary barrier; and a secondary insulation space formed between the secondary barrier and the hull. The method comprises: a vacuum forming step of forming a vacuum in the storage space, the primary insulation space, and the secondary insulation space; a liquid hydrogen loading step of loading liquid hydrogen into the storage space; and a helium gas injection step of injecting helium gas as an inert gas into the primary insulation space and the secondary insulation space. Claim 2 A method of operating a membrane-type liquid hydrogen storage tank according to claim 1, characterized in that, in the vacuum forming step, the vacuum forming operation is performed sequentially from the outermost secondary insulation space to the primary insulation space and the storage space. Claim 3 A method of operating a membrane-type liquid hydrogen storage tank according to claim 2, wherein in the vacuum forming step, a vacuum is formed until the internal pressure of the secondary insulation space becomes a first vacuum pressure, a vacuum is formed until the internal pressure of the primary insulation space becomes a second vacuum pressure, and a vacuum is formed until the internal pressure of the storage space becomes a third vacuum pressure, wherein the magnitude of the vacuum pressure is formed in the order of first vacuum pressure < second vacuum pressure < third vacuum pressure. Claim 4 A method of operating a membrane-type liquid hydrogen storage tank according to claim 3, characterized in that, in the liquid hydrogen loading step, a cool-down operation is performed by spraying a small amount of liquid hydrogen into the storage space to cool it before the liquid hydrogen is loaded into the storage space. Claim 5 A method of operating a membrane-type liquid hydrogen storage tank according to claim 4, characterized in that, as the storage space is formed into a vacuum, the process of removing moisture by supplying dry air into the storage space as a preliminary operation prior to loading liquid hydrogen into the storage space, the process of removing oxygen by supplying an inert gas into the storage space, and the process of removing the inert gas by supplying a hydrocarbon gas into the storage space can be omitted. Claim 6 A method of operating a membrane-type liquid hydrogen storage tank according to claim 4, characterized in that, in the helium gas injection step, the operation of injecting helium gas into the primary insulation space is performed first, and then the operation of injecting helium gas into the secondary insulation space is performed. Claim 7 A method of operating a membrane-type liquid hydrogen storage tank according to claim 6, wherein in the helium gas injection step, helium gas is injected until the internal pressure of the primary insulation space becomes a first internal pressure, and helium gas is injected until the internal pressure of the secondary insulation space becomes a second internal pressure, wherein the pressure magnitude is formed in the order of second internal pressure < first internal pressure < storage pressure of liquid hydrogen filled in the storage space. Claim 8 A method of operating a membrane-type liquid hydrogen storage tank according to claim 7, characterized in that a device for monitoring and controlling the pressure state of the storage space, the primary insulation space, and the secondary insulation space is provided during the vacuum forming step and the helium gas injection step.

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