Liquefied hydrogen evaporative gas control system and method

Abstract

The present invention relates to a system and method for controlling the amount of evaporated gas generated from liquefied hydrogen and for maintaining a low pressure in a liquefied hydrogen storage tank that can be applied to a storage facility that stores a large amount of hydrogen in a liquefied state or a transportation means that stores and transports liquefied hydrogen. The liquefied hydrogen evaporated gas control method according to the present invention includes a storage tank that stores liquefied hydrogen, is provided with at least two storage tanks, and is operated in a high-temperature mode or a low-temperature mode, the low-temperature mode includes a step of maintaining at least a portion of the liquefied hydrogen stored in the storage tank at a first temperature that is a densification temperature, and the high-temperature mode includes a step of recovering cold energy from the liquefied hydrogen stored in the storage tank and maintaining at least a portion of the liquefied hydrogen at a second temperature that is a temperature above the triple point of the liquefied hydrogen.

Description

[Technical Field]

[0001] The present invention relates to a liquefied hydrogen storage tank that can be applied to storage facilities that store large amounts of hydrogen in a liquefied state or to transportation means that store and transport liquefied hydrogen. More particularly, the present invention relates to a liquefied hydrogen evaporative gas control system and method that can control the amount of evaporative gas generated from liquefied hydrogen and maintain low pressure in a liquefied hydrogen storage tank. [Background technology]

[0002] Hydrogen transportation can be broadly divided into inland transportation and sea transportation. Inland transportation can be carried out using specialized vehicles and railways equipped with pipelines or storage facilities, while sea transportation can be carried out using floating vessels such as ships equipped with storage facilities.

[0003] Until recently, hydrogen has been compressed to over 200 bar, stored in special containers, and transported for small-scale supply and utilization, but with the increasing emphasis on environmentally friendly energy sources such as carbon taxes, technology for large-volume, long-distance transportation is needed. In particular, for efficient transportation, it is necessary to consider storing and transporting liquid hydrogen obtained by liquefying gaseous hydrogen through cooling and pressurization.

[0004] Liquid hydrogen can be obtained by cooling gaseous hydrogen to cryogenic temperatures (approximately -253°C at atmospheric pressure), and can be transported in liquid form by storing it in special insulated storage tanks for cryogenic temperatures.

[0005] Liquefied hydrogen has a volume that is approximately 1 / 865 of that of gaseous hydrogen, meaning that it has a volumetric energy density 865 times higher than gaseous hydrogen at the same pressure. Storing hydrogen in a liquid state allows for higher density storage than storing gaseous hydrogen at high pressure, and is advantageous in terms of storage tank safety, as well as reducing storage costs and the risk of explosion.

[0006] Existing liquefied gas storage technologies are designed for LNG (Liquefied Natural Gas) and LPG (Liquefied Petroleum Gas). Among the commercially available liquefied gas storage technologies, the liquefaction temperature of LNG is approximately -163°C at atmospheric pressure. Applying existing storage technologies to hydrogen requires higher storage pressures due to the much lower liquefaction temperature (or boiling point) of hydrogen. Therefore, in order to apply existing storage technologies to hydrogen, the insulation thickness must be increased by several to several tens of times.

[0007] In addition, if liquefied hydrogen is stored using insulation technology similar to that used for commercially available LNG, the design pressure of the storage tank will be high, exceeding 3 bar based on the triple point temperature. In other words, as the storage pressure of liquefied hydrogen increases, the thickness of the storage tank's inner wall will inevitably increase, which will exceed construction and inspection standards, making it impossible to implement.

[0008] Therefore, in storing and transporting large amounts of liquefied hydrogen, technologies that reduce storage pressure and improve insulation and energy efficiency over existing liquefied gas storage technologies are very important.

[0009] Meanwhile, in storing and transporting liquefied gas, it is essential to treat the evaporated gas, and various methods for treating the evaporated gas of LNG have been proposed and are being applied in practice.

[0010] However, while LNG remains stable at approximately 0.36 bar and approximately -163°C, liquefied hydrogen is stored at -253°C, which is approximately 90°C lower than LNG, and is stored in the 2 bar to 6 bar range, which is several times the storage pressure of LNG, 0.36 bar. In addition, liquefied hydrogen has the characteristic of irregularly generating evaporated gas due to the ortho-para conversion reaction, which means that there are practical limitations to applying LNG evaporated gas processing technology to liquefied hydrogen evaporated gas. Summary of the Invention [Problem to be solved by the invention]

[0011] Therefore, the present invention is intended to solve the above-mentioned problems, and provides an evaporation control system and method that can control the amount of evaporation generated from liquefied hydrogen when storing and transporting liquefied hydrogen.

[0012] Another object of the present invention is to provide a liquefied hydrogen evaporative gas control system and method that can control the amount of evaporative gas that is irregularly generated due to the ortho-para conversion reaction of hydrogen, maintain low pressure in the liquefied hydrogen storage tank, and enable the storage tank to be made larger.

[0013] Here, the technical problems and objectives that the present invention aims to solve are not limited to those described above, and other technical problems and objectives will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0014] According to one aspect of the present invention to achieve the above-mentioned object, there is provided a liquefied hydrogen evaporative gas control method including: at least two storage tanks for storing liquefied hydrogen, the storage tanks being provided with at least two tanks and being operated in a high-temperature mode or a low-temperature mode, the low-temperature mode including a step of maintaining at least a portion of the liquefied hydrogen stored in the storage tanks at a first temperature that is a densification temperature; and the high-temperature mode including a step of recovering cold energy from the liquefied hydrogen stored in the storage tanks and maintaining at least a portion of the liquefied hydrogen at a second temperature that is a temperature above the triple point of the liquefied hydrogen.

[0015] Preferably, in the step of maintaining the second temperature, evaporated gas of the liquefied hydrogen is generated, and the high temperature mode may further include the steps of: reducing the internal pressure of the storage tank to a vacuum state to interrupt a chain reaction of vaporization; and venting the generated evaporated gas to generate electricity.

[0016] Preferably, the cold energy of the liquefied hydrogen recovered in the high temperature mode can be supplied in the step of maintaining the first temperature.

[0017] Preferably, the step of maintaining the first temperature includes the step of solidifying at least a portion of the liquefied hydrogen stored in the storage tank operating in the low-temperature mode; and the storage tank operating in the low-temperature mode is capable of storing hydrogen in both a liquid state and a solid state.

[0018] According to another aspect of the present invention to achieve the above-mentioned object, there is provided a liquefied hydrogen evaporative gas control system, comprising: at least two storage tanks for storing liquefied hydrogen, wherein the storage tanks are provided with a densification unit for maintaining the temperature of the liquefied hydrogen stored in the storage tanks at a first temperature; and a temperature maintenance unit for maintaining the temperature at a second temperature; wherein the storage tanks include a low-temperature tank in which at least a portion of the liquefied hydrogen stored in the storage tanks is maintained at the first temperature, which is the densification temperature, by the densification unit; and a high-temperature tank in which at least a portion of the liquefied hydrogen stored in the storage tanks is maintained at a second temperature, which is a temperature above the triple point of the liquefied hydrogen, by the temperature maintenance unit.

[0019] Preferably, the fuel cell system may further include a compressor that can exhaust evaporative gas from the storage tank and reduce the internal pressure of the storage tank to a vacuum state; a buffer tank that stores the evaporative gas compressed by the compressor; and an energy conversion unit that produces electricity using the evaporative gas stored in the buffer tank.

[0020] Preferably, the system may further include a heat medium circulating unit that receives a low-temperature heat medium obtained by recovering cold energy from the liquefied hydrogen in the temperature maintaining unit of the high-temperature tank and supplies the low-temperature heat medium to the temperature maintaining unit of the low-temperature tank, and the heat medium circulating unit may be driven by electric power generated in the energy converting unit.

[0021] Preferably, the storage tank further includes a heat medium circulating unit that supplies a low-temperature heat medium to the temperature maintaining unit of the storage tank, and the densifying unit primarily recovers the cold energy of the low-temperature heat medium supplied to the temperature maintaining unit and solidifies at least a portion of the liquefied hydrogen stored in the storage tank. [Effects of the Invention]

[0022] The system and method according to the present invention can maintain the storage pressure of liquefied hydrogen at atmospheric pressure by cooling the inside of the storage tank, solidifying a portion of the liquefied hydrogen, and storing the liquefied hydrogen in a stable state.

[0023] Furthermore, by solidifying a portion of the liquefied hydrogen, it is possible to obtain cryogenic cold and latent heat of vaporization from the liquid hydrogen.

[0024] Furthermore, since the operating pressure of the liquefied hydrogen is lowered, the thickness of the inner wall of the storage tank can be reduced, allowing the liquefied hydrogen storage tank to be made larger.

[0025] When connecting a liquefied hydrogen storage tank with a fuel cell and using liquefied hydrogen evaporative gas as fuel for the fuel cell, there has been a problem in that the amount of evaporative gas generated varies depending on the external temperature and the elapsed time. However, according to the present invention, by controlling the internal temperature of the liquefied hydrogen storage tank, the amount of hydrogen evaporative gas generated, which was irregular, can be adjusted to a constant level, allowing for a stable supply of hydrogen fuel to the fuel cell, and as a result, electric power can be produced and supplied stably.

[0026] Furthermore, when transporting cryogenic liquefied gas by sea, sloshing can occur due to high waves, which can damage storage tanks. However, according to the present invention, by converting a portion of the liquefied hydrogen into a highly viscous solid, it is possible to effectively deal with sloshing and ensure the safety of transportation.

[0027] According to the present invention, the efficiency of the overall control process is improved, such as stably producing electricity by controlling the amount of evaporated gas generated while making maximum use of the cold energy of liquefied hydrogen between a low-temperature tank and a high-temperature tank, and using the produced electricity to cool the liquefied hydrogen, thereby enabling liquefied hydrogen to be maintained and stored in an ultra-low temperature liquid state for a long period of time.

[0028] In addition, the energy-efficient evaporative gas control technology can be applied not only during the storage and transportation of liquefied hydrogen, but also at terminals such as liquefied hydrogen supply bases and receiving bases where liquefied hydrogen is loaded and unloaded. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a simplified system diagram illustrating a liquefied hydrogen evaporative gas control system according to a first embodiment of the present invention.

[0030] [Figure 2] FIG. 4 is a simplified system diagram illustrating a liquefied hydrogen evaporative gas control system according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] For a fuller understanding of the operating advantages and objects attained by the practice of the present invention, reference should be made to the accompanying drawings which illustrate preferred embodiments of the invention and the content based on the accompanying drawings.

[0032] The configuration and operation of a preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, when referring to components in each drawing, the same components are denoted by the same reference numerals whenever possible, even if they appear in different drawings. Furthermore, the following embodiments can be modified into many other forms, and the scope of the present invention is not limited to the following embodiments.

[0033] The liquefied hydrogen evaporative gas control system and method according to an embodiment of the present invention, which will be described later, can be applied to both onshore and offshore storage facilities and transportation means.

[0034] Hereinafter, an embodiment of the present invention will be described based on its application to marine use, taking as an example a ship as a means of transportation on which a liquefied hydrogen storage tank is installed.

[0035] In describing an embodiment of the present invention, the ship is a ship equipped with storage facilities for storing liquefied hydrogen, and may include ships having self-propulsion capabilities, such as liquefied hydrogen carriers, as well as offshore structures that do not have propulsion capabilities but float on the sea, such as FPSOs (Floating Production Storage Offloading) and FSRUs (Floating Storage Regasification Units). However, in each embodiment described below, the ship will be described as a liquefied hydrogen carrier.

[0036] Hereinafter, a system and method for controlling liquefied hydrogen evaporative gas according to an embodiment of the present invention will be described with reference to FIGS.

[0037] First, referring to FIG. 1, a system and method for controlling evaporative gas from liquefied hydrogen in a liquefied hydrogen storage tank according to one embodiment of the present invention will be described.

[0038] The liquefied hydrogen evaporated gas control system of this embodiment includes storage tanks 101, 102 for storing liquefied hydrogen, a compressor 41 for discharging evaporated gas from the storage tanks 101, 102, a buffer tank 42 for storing the evaporated gas discharged from the storage tanks 101, 102, an energy conversion unit 47 for producing electricity using the evaporated gas discharged from the storage tanks 101, 102, and a heat medium circulation unit 40 for recovering thermal energy of the liquefied hydrogen.

[0039] The storage tanks 101 and 102 in this embodiment are 100 m 3At least two of the above large-capacity storage tanks are provided.

[0040] In addition, the operating pressure of the storage tanks 101 and 102 in this embodiment may be 0.1 bar to 6 bar, and is preferably maintained at 3 bar or less, more preferably 1 bar or less, or at normal pressure.

[0041] In this embodiment, the storage tanks 101 and 102 may be operated in either a low-temperature mode in which they are maintained at a first temperature or a high-temperature mode in which they are maintained at a second temperature higher than the first temperature. Hereinafter, in the description of this embodiment, the storage tank operated in the low-temperature mode will be referred to as the low-temperature tank 101, and the storage tank operated in the high-temperature mode will be referred to as the high-temperature tank 102.

[0042] In this embodiment, the first temperature is a densification temperature that increases the density of the stored liquefied hydrogen. The densification temperature in this embodiment is a temperature range in which the liquefied hydrogen exists in a mixed state of solid and liquid, and may be approximately 14K to 21K.

[0043] In this embodiment, when the storage tanks 101, 102 are operated in the low-temperature mode, the liquefied hydrogen stored in the storage tanks 101, 102 is maintained at the densification temperature, and the liquefied hydrogen in the densification temperature range exists in a solid state that is denser than when at least a portion of the liquefied hydrogen is in a liquid state, and exists in a mixed state of liquid and solid, preferably in a slurry state.

[0044] The density of liquefied hydrogen is approximately 1 kg / m per 1 K. 3 The density of liquefied hydrogen changes gradually, but when the temperature is 14K, it is about 77kg / m 3 When the temperature of liquefied hydrogen is 21K, the density is 77kg / m 3 is.

[0045] In this embodiment, the second temperature may be the triple point temperature of the liquefied hydrogen, for example, a temperature above 21 K. When the storage tank is maintained at the second temperature, the temperature of the hydrogen in the storage tank may be maintained at a temperature slightly higher than 21 K, i.e., approximately 21 K.

[0046] In this embodiment, when two storage tanks 101 and 102 are provided, one tank is operated as a low-temperature tank 101 and the other tank is operated as a high-temperature tank 102. In addition, the low-temperature tank 101, which has been operating in a low-temperature mode, and the high-temperature tank 102, which has been operating in a high-temperature mode, may be operated while switching between their operating modes.

[0047] That is, the low-temperature tank 101 operated in low-temperature mode can be operated as the high-temperature tank 102 operated in high-temperature mode when the low-temperature mode is completed, and the high-temperature tank 102 operated in high-temperature mode can be operated as the low-temperature tank 101 operated in low-temperature mode when the high-temperature mode is completed.

[0048] Depending on the operating conditions of the ship, the number of storage tanks operating in low temperature mode and the number of storage tanks operating in high temperature mode among the two or more storage tanks 101, 102 can be adjusted.

[0049] As an example, when a ship is sailing at sea carrying liquefied hydrogen, two or more storage tanks 101, 102 are all operated in cryogenic mode.

[0050] In addition, when this system is applied to a liquefied hydrogen storage base, it can be operated in a crossover mode, with at least one storage tank operating in low-temperature mode and at least one storage tank operating in high-temperature mode. Since the storage base needs to use hydrogen evaporative gas (or vaporized gas) as fuel to produce electricity for use in the system, at least one storage tank operates in high-temperature mode to continuously generate a certain amount of hydrogen evaporative gas, enabling stable production and supply of electricity.

[0051] A liquefied hydrogen storage base is a base equipped with numerous liquefied hydrogen storage tanks on land or at sea, where large volumes of liquefied hydrogen are stored and supplied (loaded and unloaded) to transportation means or destinations.

[0052] Meanwhile, when the stored liquefied hydrogen is loaded onto a transportation means or a consumer, the liquefied hydrogen is supplied sequentially or in a chain-like manner from multiple liquefied hydrogen storage tanks. In this case, the multiple liquefied hydrogen storage tanks are operated in a crossover mode, i.e., a mode including at least one liquefied hydrogen storage tank operating in a high-temperature mode and at least one liquefied hydrogen storage tank operating in a low-temperature mode. If there is one storage tank remaining for loading and unloading liquefied hydrogen, that one liquefied hydrogen storage tank can be operated in the high-temperature mode.

[0053] According to this embodiment, the pressure of the storage tanks 101 and 102 can be maintained at 3 bar or less, 1 bar or less, or at normal pressure, regardless of whether the storage tanks 101 and 102 are operated in the low temperature mode or the high temperature mode.

[0054] 1 shows that the compressor 41, buffer tank 42, and energy conversion unit 47 are connected only to the high-temperature tank 102, but the compressor 41, buffer tank 42, and energy conversion unit 47 may also be connected to the low-temperature tank 101. Alternatively, a separate compressor, buffer tank, and energy conversion unit connected to the low-temperature tank 101 may be provided.

[0055] In this embodiment, an example will be described in which the low-temperature tank 101 and the high-temperature tank 102 share the compressor 41, the buffer tank 42, and the energy conversion unit 47. The low-temperature tank 101 and the compressor 41 are connected by a first evaporated gas supply line BL1, and the high-temperature tank 102 and the compressor 41 are connected by a second evaporated gas supply line BL2.

[0056] In this embodiment, the storage tanks 101, 102 are provided inside with temperature maintaining units 44, 46, which are flow paths through which the low-temperature or high-temperature heat medium transferred from the heat medium circulating unit 40 flows in order to maintain the internal temperatures of the storage tanks 101, 102 within the respective operating ranges, and densification units 43, 45, which are located above the temperature maintaining units 44, 46 and through which the low-temperature heat medium transferred from the heat medium circulating unit 40 flows, thereby increasing the density of the liquefied hydrogen in the storage tanks 101, 102.

[0057] In this embodiment, as shown in the drawings, the densification sections 43, 45 are arranged at the upper ends of the temperature maintenance sections 44, 46, but the densification sections 43, 45 and the temperature maintenance sections 44, 46 may be arranged parallel to each other, and their positions are not limited.

[0058] In the following description of this embodiment, the densification section of the low-temperature tank 101 will be named the first densification section 43, the temperature maintenance section of the low-temperature tank 101 will be named the first temperature maintenance section 44, the densification section of the high-temperature tank 102 will be named the second densification section 45, and the temperature maintenance section of the high-temperature tank 102 will be named the second temperature maintenance section 46.

[0059] The first densification section 43, the first temperature maintenance section 44 and the heat medium circulation section 40 are connected by a first heat medium line ML1, and the second densification section 45, the second temperature maintenance section 46 and the heat medium circulation section 40 are connected by a second heat medium line ML2.

[0060] The cryogenic tank 101 operating in the low temperature mode receives a low temperature heat transfer medium via the first heat transfer medium line ML1 and can be maintained at a first temperature of 13K to 21K, 20K or less, or 13K to 14K, which is the densification temperature.

[0061] The hydrogen inside the cryogenic tank 101 operating in the cryogenic mode can exist in a liquid state, a two-phase mixture of liquid and solid, or a three-phase mixture of liquid, solid, and gas.

[0062] The high temperature tank 102 operated in high temperature mode receives a high temperature heat transfer medium via the second heat transfer medium line ML2 and may be maintained at an operating temperature slightly above the triple point temperature, for example, about 21K.

[0063] The hydrogen within the high temperature tank 102 operated in high temperature mode can exist in a liquid state, a gaseous state, or a two-phase mixture of liquid and gas.

[0064] The heat medium circulating unit 40 of this embodiment supplies a high-temperature heat medium to the high-temperature tank 102 and receives a low-temperature heat medium from the high-temperature tank 102 by recovering the cold energy of the liquefied hydrogen.

[0065] The heat medium circulating unit 40 also supplies a low-temperature heat medium to the low-temperature tank 101 and receives a high-temperature heat medium by transferring cold to the hydrogen stored in the low-temperature tank 101 .

[0066] The heat medium circulating section 40 of this embodiment may be a refrigeration cycle that uses helium as a refrigerant.

[0067] The fluid transferred through the heat transfer medium lines ML1 and ML2 may be helium or an intermediate heat transfer medium that indirectly transfers thermal energy between helium and the hydrogen stored in the storage tanks 101 and 102.

[0068] In this embodiment, the low-temperature mode is implemented to suppress the reactivity of the liquefied hydrogen stored in the storage tank, so that the hydrogen can be stored stably while maintaining its liquid state.

[0069] In this embodiment, the high-temperature mode is implemented to vaporize a portion of the liquefied hydrogen stored in the storage tank and induce the generation of a certain amount of evaporated gas, thereby supplying fuel for producing electricity in the energy conversion unit 47. It is also possible to recover cold energy from the liquefied hydrogen in the high-temperature tank 102 operated in the high-temperature mode to be supplied to the liquefied hydrogen in the low-temperature tank 101 operated in the low-temperature mode.

[0070] In this embodiment, the densifying sections 43, 45 operate in a low temperature mode, and the temperature maintaining sections 44, 46 operate in a high temperature mode, and may also operate in a low temperature mode if desired.

[0071] That is, when the densification sections 43, 45 are activated, the temperature of the liquefied hydrogen around the densification sections 43, 45 is maintained at a first temperature, and when the temperature maintenance sections 44, 46 are activated, the temperature of the liquefied hydrogen around the temperature maintenance sections 44, 46 is maintained at a second temperature.

[0072] In the low-temperature mode of this embodiment, a low-temperature heat medium is supplied from the heat medium circulating unit 40 to the first densification unit 43 of the low-temperature tank 101 via the first heat medium line ML1, and the medium-temperature heat medium from which cold has been primarily recovered in the first densification unit 43 can be transferred to the first temperature maintaining unit 44.

[0073] The first densification unit 43 solidifies a portion of the stored liquefied hydrogen through cooling, thereby suppressing the reactivity of the liquefied hydrogen. When a portion of the liquefied hydrogen begins to solidify, the ortho-para conversion reaction of the liquefied hydrogen is suppressed, thereby preventing the liquefied hydrogen from changing into a gas phase and stabilizing the liquefied hydrogen by preventing the diffusion of vaporization. A portion of the liquefied hydrogen stored in the cryogenic tank 101 by the first densification unit 43, for example, the surface layer of the liquefied hydrogen, may exist in a slurry state.

[0074] The first densification unit 43 solidifies a portion of the liquefied hydrogen stored in the cryogenic tank 101, specifically, the liquefied hydrogen around the location of the first densification unit 43. The first densification unit 43 of this embodiment may be selectively operated when the reactivity of the liquefied hydrogen stored in the cryogenic tank 101 increases above a reference value or at a temperature below a specific temperature.

[0075] According to this embodiment, densification units 43, 45, which are solidification devices that change the phase of liquefied hydrogen into a solid state, are installed inside the storage tanks 101, 102 of this embodiment, which are large tanks, to solidify the liquefied hydrogen.The stored liquefied hydrogen is solidified not entirely but partially, and the hydrogen is stored in a solid state that partially retains more cold heat, thereby maximizing the retained latent heat and allowing hydrogen to be stored stably.

[0076] Furthermore, the first temperature maintaining unit 44 can maintain the temperature of a portion of the liquefied hydrogen stored in the cryogenic tank 101, for example, the liquefied hydrogen in the vicinity where the first temperature maintaining unit 44 is located, at 20K or less.

[0077] The high-temperature heat medium whose temperature has increased while cooling the liquefied hydrogen in the first temperature maintaining unit 44 is recovered to the heat medium circulating unit 40 via the first heat medium line ML1.

[0078] In this embodiment, the internal temperature of the cryogenic tank 101 operating in low-temperature mode is maintained below 20K, and at least a portion of the liquefied hydrogen exists in a solid state, thereby acting as a shield and suppressing the evaporation of the liquefied hydrogen. Through this operation, the internal pressure of the cryogenic tank 101 is maintained below 1 bar.

[0079] On the other hand, in the high temperature mode of this embodiment, the high temperature heat medium is supplied from the heat medium circulating unit 40 to the second temperature maintaining unit 46 of the high temperature tank 102 via the second heat medium line ML2.

[0080] The second temperature maintaining unit 46 maintains the internal temperature of the high-temperature tank 102 at a temperature above the triple point, ie, at 21 K or higher, and when a high-temperature heat medium is supplied to the high-temperature tank 102, a vaporization reaction begins to occur.

[0081] The low-temperature heat medium, whose temperature has been reduced while recovering the cold energy from the liquefied hydrogen in the second temperature maintaining unit 46, is recovered to the heat medium circulating unit 40 via the second heat medium line ML2.

[0082] Hydrogen molecules are classified as ortho-hydrogen and para-hydrogen depending on the spin direction of the atomic nucleus. The ratio of ortho-hydrogen to para-hydrogen is temperature-dependent. At room temperature and pressure, hydrogen exists in a gaseous state, with the ratio of ortho-hydrogen to para-hydrogen being 3:1. However, when the temperature drops to 20K, hydrogen exists in a liquid state, with para-hydrogen overwhelmingly predominating at 99.8%.

[0083] However, hydrogen molecules spin in one direction, but when the temperature drops, one molecule spins in the opposite direction, generating heat as it spins on both sides and vaporizing itself. In other words, if hydrogen is stored for a long time, it will naturally convert to para-hydrogen, and the conversion reaction from ortho-hydrogen to para-hydrogen generates heat.

[0084] Since the heat of conversion generated during the ortho-para hydrogen conversion reaction is greater than the latent heat of vaporization of the liquefied hydrogen, the stored liquefied hydrogen begins to evaporate.

[0085] Due to the characteristics of hydrogen, hydrogen evaporative gas is generated irregularly as it instantaneously generates a chain reaction, then stops vaporizing, and the amount of gas generated suddenly decreases. However, according to this embodiment, the storage tank can be operated in high temperature mode and low temperature mode to regulate the amount of gas generated to a constant level.

[0086] On the other hand, in this embodiment, when it is time to discharge the evaporated gas from the storage tanks 101 and 102, the compressor 41 is operated to discharge the evaporated gas.

[0087] The compressor 41 of this embodiment compresses and discharges the evaporated gas in the storage tanks 101 and 102, but when the evaporated gas in the storage tanks 101 and 102 is explosively generated, it can operate to supply and exhaust the evaporated gas so that the inside of the storage tanks 101 and 102 is in a medium vacuum state.

[0088] In particular, the compressor 41 is used as a means for discharging evaporative gases when the storage tanks 101, 102 are operated in low temperature mode, and as a means for creating a medium vacuum in the storage tanks 101, 102 when the storage tanks are operated in high temperature mode.

[0089] When the compressor 41 is operated and the storage tanks 101 and 102 are placed under a medium vacuum, an ortho-para conversion reaction begins to occur in the storage tanks 101 and 102. When the proportion of para hydrogen increases, the compressor 41 is stopped and the vacuum in the storage tanks 101 and 102 is released, thereby stabilizing the storage tanks 101 and 102.

[0090] Compressor 41 is 100m 3 The compressor is capable of creating a vacuum for a large liquefied hydrogen storage tank, and may be a multi-stage compressor in which one or more compressors are connected in series depending on the operating range, or multiple compressors may be installed in parallel.

[0091] When the compressor 41 is operated, the evaporated gas discharged from the storage tanks 101 and 102 through the second evaporated gas supply line BL2 can be transferred to the buffer tank 42 through the first evaporated gas distribution line CL1 and stored in the buffer tank 42.

[0092] In addition, the evaporated gas discharged from the storage tanks 101 and 102 may be transferred to the energy converter 47 via a second evaporated gas distribution line CL2.

[0093] In this embodiment, the energy conversion unit 47 may include at least one of a fuel cell that uses hydrogen as fuel to produce electricity through an electrochemical reaction, and a turbine generator that uses hydrogen gas as a working fluid to drive a turbine and converts the turbine's driving energy into electricity to produce electricity.

[0094] The electricity generated in the energy conversion unit 47 in this embodiment may be used in the heat medium circulation unit 40, or may be distributed and supplied to electricity demand destinations on the ship by an electricity distribution means (not shown) such as a switchboard (not shown).

[0095] When gaseous nitrogen or methane is compressed and then Joule-Thomson expanded, the temperature decreases and it liquefies, but gaseous hydrogen and helium have a lower inversion temperature than room temperature, so when they are expanded at room temperature, the temperature actually rises. Therefore, when hydrogen is expanded below the inversion temperature, the temperature drops.

[0096] In this embodiment, the internal temperature of the high-temperature tank 102 operated in high-temperature mode is maintained above 20 K but below the inversion temperature, creating a vacuum inside the high-temperature tank 102 to promote conversion to parahydrogen, while simultaneously supplying and venting evaporated gases, thereby controlling the pressure in the high-temperature tank 102 and the amount of evaporated gas generated. Through this operation, the internal pressure of the high-temperature tank 102 is maintained at 3 bar or less.

[0097] Next, with reference to FIG. 2, a liquefied hydrogen evaporative gas control system and method according to a second embodiment of the present invention will be described.

[0098] This embodiment is a modified example of the first embodiment described above, and relates to a system and method for controlling the evaporated gas of liquefied hydrogen while supplying liquefied hydrogen to a consumer in a loading / unloading mode in which liquefied hydrogen is loaded between a liquefied gas storage tank to which the liquefied hydrogen evaporated hydrogen control system and method according to the first embodiment is applied and a transportation means (liquefied hydrogen consumer 51, 52).

[0099] Therefore, this embodiment relates to a liquefied hydrogen supply system and method in which the liquefied hydrogen storage tank and liquefied hydrogen evaporated gas control system and method according to the first embodiment described above are applied in the same manner, but the storage facility or transportation means to which the first embodiment described above is applied is operated in a loading mode to load and unload liquefied hydrogen from the liquefied hydrogen storage tank to a liquefied hydrogen demand destination, thereby supplying liquefied hydrogen.

[0100] According to this embodiment, the multiple liquefied hydrogen storage tanks 101, 102 are operated in an alternating mode. Also, according to this embodiment, the multiple liquefied hydrogen storage tanks 101, 102 are operated to include at least one low temperature tank 101 and at least one high temperature tank 102. However, the last liquefied hydrogen storage tank to be loaded can be operated as the high temperature tank 102.

[0101] According to this embodiment, in the first embodiment described above, the system further includes two or more pressure tanks 100 which are smaller in capacity than the storage tanks 101, 102 but are operated at a higher pressure than the storage tanks 101, 102 and store liquefied hydrogen to be supplied to liquefied hydrogen demand destinations 51, 52, liquefied hydrogen supply lines SL1, SL2 which connect the pressure tanks 100 to the liquefied hydrogen demand destinations 51, 52 and transport the liquefied hydrogen from the pressure tanks 100 to the liquefied hydrogen demand destinations 51, 52, and recovery lines RL1, RL2, RL3, RL4, RL5 which recover evaporated gas from the pressure tanks 100 and the liquefied hydrogen demand destinations 51, 52.

[0102] The operating pressure of the pressure tank 100 of this embodiment can be maintained at a higher pressure than the operating pressure of the storage tanks 101 and 102, which are operated at 3 bar or less. The pressure tank 100 of this embodiment may also be operated at 6 bar or more, or 10 bar or more.

[0103] Meanwhile, since the operating pressure of the pressure tank 100 is higher than the operating pressure of the storage tanks 101, 102, a supply pump 50 may be installed in the liquefied hydrogen discharge line LL connecting the storage tanks 101, 102 and the pressure tank 100 to pressurize and supply liquefied hydrogen from the storage tanks 101, 102 to the pressure tank 100. In this case, the liquefied hydrogen is transferred to the pressure tank 100 while being pressurized by the supply pump 50.

[0104] The supply pump 50 of this embodiment can be omitted as an optional configuration, and the height of the pressure tank 100 may be lower than the height of the storage tanks 101, 102, even if additional power such as the supply pump 50 is not provided. Liquefied hydrogen can then be transferred from the storage tanks 101, 102 to the pressure tank 100 due to the height difference.

[0105] According to this embodiment, before transferring liquefied hydrogen from the storage tank 102 to the pressure tank 100, it can be pre-cooled using liquefied hydrogen discharged from the storage tank 102 via a liquefied hydrogen discharge line LL connecting the storage tank 102 and the pressure tank 100.

[0106] When the supply pump 50 is installed, the cavitation phenomenon of the supply pump 50 can be prevented by pre-cooling both the liquefied hydrogen discharge line LL and the supply pump 50.

[0107] As a means for pre-cooling the liquefied hydrogen discharge line LL, a liquefied hydrogen recovery line LL1 may be further included, which branches off from the pressure tank 100 or the portion where the pressure tank 100 and the liquefied hydrogen discharge line LL meet, i.e., upstream of the header, and joins the portion where the liquefied hydrogen discharge line LL meets the upstream of the supply pump 50 or the storage tanks 101, 102, i.e., downstream of the header, and pre-cools the liquefied hydrogen discharge line LL while recirculating the liquefied hydrogen whose temperature has increased to the upstream of the liquefied hydrogen discharge line LL.

[0108] In this embodiment, the internal pressure of the pressure tank 100 is maintained at 10 bar or more, and the operating pressures of the liquefied hydrogen demand destinations 51 and 52 are maintained at 10 bar or less.

[0109] The internal pressure of the pressure tank 100 can be maintained by supplying the evaporated gas discharged from the storage tanks 101 and 102 to the pressure tank 100 while compressing it.

[0110] According to this embodiment, in order to maintain the internal pressure of the pressure tank 100 at the operating pressure, at least one of the multiple storage tanks 101, 102 is operated in high temperature mode, and evaporated gas discharged from the high temperature tank 102 can be supplied to the pressure tank 100 using the compressor 41.

[0111] Therefore, FIG. 2 only shows the connection relationship between the high-temperature tank 102 and the pressure tank 100, and the explanation will be given using the example of supplying liquefied hydrogen from the high-temperature tank 102 to the pressure tank 100, but it goes without saying that the same can be applied to the low-temperature tank 101.

[0112] Of the high-pressure evaporated gas discharged from the high-temperature tank 102 and compressed by the compressor 41, the amount of evaporated gas that exceeds the amount of evaporated gas required by the pressure tank 100 may be stored in the buffer tank 42 or supplied to the energy conversion unit 47 and used to generate electricity, or may be stored in the buffer tank 42 and then supplied to the energy conversion unit 47.

[0113] In addition, in order to prevent the pressure in the pressure tank 100 from becoming lower than the operating pressure, the high-pressure evaporated gas stored in the buffer tank 42 can be supplied to the pressure tank 100 with priority.

[0114] In this embodiment, the compressor 41 is a multi-stage compressor and may include a first compressor that exhausts the evaporative gas from the high-temperature tank 102 and depressurizes the inside of the high-temperature tank 102 to a vacuum state, and a second compressor that compresses the evaporative gas to a required pressure in the pressure tank 100. The first compressor and the second compressor may be connected in series or in parallel.

[0115] The loading and unloading of liquefied hydrogen from the pressure tank 100 to the liquefied hydrogen demand destinations 51, 52 can be carried out by discharging liquefied hydrogen from the pressure tank 100 to the first liquefied hydrogen supply line SL1 and the second liquefied hydrogen supply line SL2 due to the pressure of the liquefied hydrogen transferred from the storage tanks 101, 102 to the pressure tank 100 along the liquefied hydrogen discharge line LL due to a pressure difference or height difference, and the self-pressure of the high-pressure evaporated gas transferred from the buffer tank 42 via the third evaporated gas distribution line CL3.

[0116] The third evaporative gas distribution line CL3 is a high-pressure evaporative gas flow path that connects the buffer tank 42 and the pressure tank 100, and is a means for maintaining the internal pressure of the pressure tank 100. The high-pressure evaporative gas compressed by the compressor 41, or the high-pressure evaporative gas stored in the buffer tank 42 after being compressed by the compressor 41, is transferred to the pressure tank 100 via the third evaporative gas distribution line CL3.

[0117] In this embodiment, when the high-pressure evaporated gas transported through the third evaporated gas distribution line CL3 is insufficient to maintain the internal pressure of the pressure tank 100, the internal pressure of the pressure tank 100 can be maintained by vaporizing and supplying the liquefied hydrogen stored in the pressure tank 100.

[0118] As means for maintaining the internal pressure of the pressure tank 100, the pressure tank 100 may further include a third heat medium line ML3 connecting the pressure tank 100 and the heat medium circulation section 40, and a fifth recovery line RL5 connecting the pressure tank 100 and the upstream of the compressor 41.

[0119] The high-temperature heat medium is transferred from the heat medium circulation unit 40 to the pressure tank 100 via the third heat medium line ML3, and the low-temperature heat medium that has recovered cold energy while vaporizing the liquefied hydrogen stored in the pressure tank 100 is recovered again to the heat medium circulation unit 40 via the third heat medium line ML3.

[0120] When the heat medium is circulated through the third heat medium line ML3 and evaporative gas is generated in the pressure tank 100, the internal pressure of the pressure tank 100 increases, thereby maintaining the operating pressure of the pressure tank 100. In addition, the operating pressure of the pressure tank 100 can be maintained by discharging the evaporative gas through the fifth recovery line RL and then supplying it upstream of the compressor 41, compressing the evaporative gas in the compressor 41, and supplying it to the pressure tank 100 in the form of high-pressure evaporative gas.

[0121] The third heat medium line ML3 connecting the pressure tank 100 and the heat medium circulating unit 40, and various devices such as a heat exchanger and valves that may be installed in the header and the third heat medium line ML3, which connect the pressure tank 100 and the heat medium circulating unit 40, are installed in a cold box, thereby achieving primary vacuum insulation. A hydrogen sensor for detecting hydrogen leakage may be installed in the cold box.

[0122] Additionally, insulation can be provided on the outside of the cold box to provide additional secondary insulation.

[0123] The liquefied hydrogen demand destinations 51, 52 in this embodiment may include at least one of a liquefied hydrogen storage base 51 such as a liquefied hydrogen terminal as a first demand destination, and a vaporizer 52 that vaporizes liquefied hydrogen and supplies it to a gaseous hydrogen demand destination as a second demand destination.

[0124] In this embodiment, the liquefied hydrogen storage base 51 is a concept that includes not only a land terminal but also a ship or land trailer that receives liquefied hydrogen at the terminal.

[0125] The first demand destination 51 receives liquefied hydrogen via a first liquefied hydrogen supply line SL1 connecting the pressure tank 100 and the first demand destination 51, and the second demand destination 52 receives liquefied hydrogen via a second liquefied hydrogen supply line SL2 connecting the pressure tank 100 and the second demand destination 52.

[0126] On the other hand, before transferring liquefied hydrogen to liquefied hydrogen demand destinations 51 and 52, liquefied hydrogen supply lines SL1 and SL2 can be pre-cooled using liquefied hydrogen stored in pressure tank 100 or storage tank 102.

[0127] The evaporated gas vaporized while pre-cooling the liquefied hydrogen supply lines SL1 and SL2 can be recovered to the pressure tank 100 via a third recovery line RL3 connected to the pressure tank 100, or can be recovered to the compressor 41 via a fourth recovery line RL4 connected to the compressor 41.

[0128] The evaporated gas vaporized while pre-cooling the first liquefied hydrogen supply line SL1 is recovered in the third recovery line RL3 and the fourth recovery line RL4 via the first recovery line RL1, and the evaporated gas vaporized while pre-cooling the second liquefied hydrogen supply line SL2 is recovered in the third recovery line RL3 and the fourth recovery line RL4 via the second recovery line RL2.

[0129] On the other hand, evaporated gas generated at the liquefied hydrogen demand destinations 51, 52 while liquefied hydrogen is being supplied to the liquefied gas demand destinations 51, 52 and exceeding the allowable pressure of the liquefied hydrogen demand destinations 51, 52 can also be recovered in the compressor 41 via the first to fourth recovery lines RL1 to RL4.

[0130] The evaporated gas recovered upstream of the compressor 41 via the fourth recovery line RL4 and the fifth recovery line RL5 may be compressed by the compressor 41 and then stored in the buffer tank 42, or may be recovered in the pressure tank 100 and used to maintain the internal pressure of the pressure tank 100.

[0131] In addition, the evaporated gas recovered from liquefied hydrogen demand destinations 51, 52 via the fourth recovery line RL4 and the fifth recovery line RL5 may be supplied to the energy conversion unit 47 via the second evaporated gas distribution line CL2 connected to the energy conversion unit 47 and used for electricity production.

[0132] Meanwhile, in this embodiment, the second demand destination 52 may be a vaporizer, and the heat of vaporization generated when the liquefied hydrogen is vaporized in the vaporizer may be recovered via a fourth heat medium line ML4 connecting the heat medium circulating unit 40 and the second demand destination 52.

[0133] The high-temperature heat medium is supplied from the heat medium circulation unit 40 to the vaporizer 52 via the fourth heat medium line ML4, and the low-temperature heat medium that has recovered cold energy while vaporizing the liquefied hydrogen in the vaporizer 52 is recovered in the heat medium circulation unit 40 via the fourth heat medium line ML4.

[0134] In addition, the vaporizer 52 can receive waste heat generated while producing electricity in the energy conversion unit 47 via a waste heat supply line EL connecting the energy conversion unit 47 and the vaporizer 52, and can use this waste heat as thermal energy to vaporize the liquefied hydrogen.

[0135] The temperature of the thermal energy transferred through the waste heat supply line EL may be about 500 to 600°C.

[0136] The system and method according to this embodiment can use the evaporated gas generated during the loading and unloading of liquefied hydrogen to maintain the pressure in the pressure tank 100 and generate pressure for sending the liquefied hydrogen to a demand destination. In addition, the pressure in the pressure tank 100 can be maintained while effectively maximizing the use of the cold heat and waste heat of the liquefied hydrogen during the loading and unloading of liquefied hydrogen.

[0137] In the second embodiment, liquefied hydrogen is supplied from storage tanks 101 and 102 to pressure tank 100, and then loaded from pressure tank 100 to liquefied hydrogen consumers 51 and 52. However, this embodiment can also be applied to a case where liquefied hydrogen is directly loaded from a liquefied hydrogen receiving terminal to pressure tank 100, and simultaneously liquefied hydrogen is loaded from pressure tank 100 to liquefied hydrogen consumers 51 and 52. In this case, the storage facility installed at the onshore liquefied hydrogen receiving terminal may include storage tanks 101 and 102 of this embodiment.

[0138] It will be obvious to those skilled in the art to which the present invention pertains that the present invention is not limited to the above embodiments and can be modified or altered in various ways without departing from the technical scope of the present invention. [Explanation of symbols]

[0139] 100 Pressure Tank

[0140] 101 Cryogenic Tank

[0141] 102 High-Temperature Tank

[0142] 40 Heat medium circulation section

[0143] 41 Compressor

[0144] 42 Buffer tank

[0145] 47 Energy Conversion Department

[0146] 43, 45 High density section

[0147] 44, 46 Temperature maintenance section

[0148] 51, 52 Demand for liquefied hydrogen

[0149] BL1, BL2 evaporative gas supply line

[0150] CL1, CL2, CL3 Evaporative gas distribution lines

[0151] ML1, ML2, ML3, ML4, ML5 Heat transfer medium lines

[0152] RL1, RL2, RL3, RL4, RL5 recovery lines

[0153] SL1, SL2 liquefied hydrogen supply lines

[0154] LL Liquid hydrogen discharge line

[0155] LL1 Liquefied hydrogen recovery line

[0156] EL waste heat supply line

Claims

1. storing liquefied hydrogen and suppressing or inducing a vaporization reaction of the stored liquefied hydrogen using temperature maintaining means provided in each of at least two storage tanks for maintaining the internal temperature of the storage tank at a required temperature in a high temperature mode or a low temperature mode; In the step of suppressing or inducing a vaporization reaction of the stored liquefied hydrogen, The low temperature mode is maintaining at least a portion of the liquefied hydrogen stored in the storage tank at a first temperature, which is a densification temperature, thereby suppressing an ortho-para conversion reaction of hydrogen; The high temperature mode is maintaining at least a portion of the liquefied hydrogen stored in the storage tank at a second temperature that is a temperature above the triple point of the liquefied hydrogen; While maintaining the temperature of the storage tank at a second temperature, reducing the internal pressure of the storage tank to a medium vacuum state to induce an ortho-para conversion reaction and increase the proportion of para-hydrogen; and and releasing the vacuum in the storage tank after the ratio of para-hydrogen reaches a predetermined value, thereby stopping the chain reaction of vaporization.

2. 2. The method for controlling liquefied hydrogen evaporative emissions according to claim 1, further comprising the step of: supplying the exhausted evaporative emissions as fuel to generate electricity.

3. 2. The liquefied hydrogen evaporated gas control method according to claim 1, wherein the cold energy of the liquefied hydrogen recovered from the storage tank operated in the high-temperature mode is supplied to the storage tank operated in the low-temperature mode.

4. The step of maintaining the first temperature comprises: solidifying at least a portion of the liquefied hydrogen stored in the storage tank operating in the low-temperature mode; 2. The method for controlling liquefied hydrogen evaporated gas according to claim 1, wherein hydrogen is stored in the storage tank operated in the low-temperature mode in both a liquid state and a solid state.

5. Storage tanks for storing liquefied hydrogen, of which at least two are provided; a temperature maintaining means for maintaining the internal temperature of the storage tank at a required temperature in a high temperature mode or a low temperature mode, each of the two or more storage tanks being provided therein; The temperature maintaining means is a densification unit that operates when the storage tank operates in a low-temperature mode and maintains the temperature of at least a portion of the liquefied hydrogen stored in the storage tank at a first temperature that is a densification temperature, thereby suppressing the ortho-para conversion reaction of hydrogen; and a temperature maintaining unit that operates when the storage tank operates in a high-temperature mode to maintain at least a portion of the liquefied hydrogen stored in the storage tank at a second temperature that is a temperature above the triple point of the liquefied hydrogen; a compressor that exhausts evaporated gas from the storage tank, and reduces the internal pressure of the storage tank to a medium vacuum state while maintaining the temperature of the storage tank at a second temperature, thereby inducing an ortho-para conversion reaction to increase the proportion of para-hydrogen, or that releases the vacuum in the storage tank after the proportion of para-hydrogen reaches a predetermined value, thereby stopping the chain reaction of vaporization; a heat medium circulating unit that receives a low-temperature heat medium obtained by recovering cold energy from the liquefied hydrogen in the temperature maintaining unit of the storage tank operated in the high-temperature mode, and supplies the low-temperature heat medium to the temperature maintaining unit of the storage tank operated in the low-temperature mode; Liquefied hydrogen evaporative gas control system.

6. A buffer tank for storing the evaporated gas compressed by the compressor; and an energy conversion unit that generates electricity using the evaporated gas stored in the buffer tank; The liquefied hydrogen evaporative emission control system of claim 5, comprising:

7. A liquefied hydrogen evaporative gas control system as described in claim 5, wherein the densification section primarily recovers the cold energy of the low-temperature heat medium supplied to the temperature maintenance section and solidifies at least a portion of the liquefied hydrogen stored in the storage tank.

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