High-efficiency hydrogen liquefaction system and hydrogen liquefaction process

Abstract

A high-efficiency hydrogen liquefaction system according to the present invention may comprise: a cooling cycle unit including a first pre-cooling cycle provided to circulate a first pre-cooling refrigerant and a liquefaction cycle provided to circulate a liquefaction refrigerant; a cooling line unit through which a cooling target provided to be cooled by the cooling cycle unit passes; and a heat exchange unit including a plurality of heat exchangers that allow heat exchange between the cooling cycle unit and the cooling line unit, wherein, among the plurality of heat exchangers, a heat exchanger allowing heat exchange with the first pre-cooling cycle is referred to as a high-temperature part heat exchanger, the liquefaction cycle includes a liquefaction line through which a liquefaction refrigerant passes, and the liquefaction cycle may include a bypass line branched from one point of the liquefaction line and joined to the other point of the liquefaction line such that, among the plurality of heat exchangers, heat exchange is not performed only in at least one of the high-temperature part heat exchangers.

Description

High-efficiency hydrogen liquefaction system and hydrogen liquefaction process

[0001] The present invention relates to a high-efficiency hydrogen liquefaction system and a hydrogen liquefaction process.

[0002] With the recent expansion of hydrogen fuel utilization across various fields, the need for large-scale hydrogen liquefaction processes is emerging. Unlike unstable gaseous hydrogen, liquid hydrogen can be stored at atmospheric pressure and has a relatively small volume, offering high safety and economic efficiency in terms of area.

[0003] Figure 1 is a conceptual diagram showing the flow of an exemplary hydrogen liquefaction process. Figure 2 is a conceptual diagram showing the temperature range of an exemplary hydrogen liquefaction process. Figure 3 is a pressure-temperature graph showing the Joule-Thomson coefficients of each material.

[0004] As illustrated, the hydrogen liquefaction process can be carried out through pre-cooling and liquefaction. The pretreatment steps can be performed in sequence, and the process of pre-cooling the pretreated hydrogen can be performed.

[0005] Gaseous hydrogen is cooled to an appropriate temperature through a pre-cooling process. Here, the appropriate temperature refers to a state suitable for carrying out the subsequent liquefaction process and can be selected by referring to the pressure-temperature graph based on the Joule-Thomson coefficient in Fig. 3. In Fig. 3, the horizontal axis represents pressure in atmospheric pressure (atm), and the vertical axis represents temperature in absolute temperature, Kelvin (K).

[0006] Referring to the graph in Figure 3, there are regions where the Joule-Thomson coefficient is positive and regions where it is negative. The Joule-Thomson coefficient represents the value of the change in temperature according to the change in pressure at the same enthalpy. In other words, if the Joule-Thomson coefficient is positive, the temperature decreases with the decrease in pressure when the gas expands. Therefore, in order to liquefy hydrogen by reducing its temperature through Joule-Thomson expansion, gaseous hydrogen must be placed in the region where the Joule-Thomson coefficient is positive as shown in the graph, and this pre-liquefaction state is achieved through pressurization and pre-cooling. For example, pre-cooling can be performed to 80K (-193℃), a temperature that falls within the region where the Joule-Thomson coefficient of hydrogen is positive, by utilizing the heat of vaporization of liquid nitrogen.

[0007] In the main cooling process, pre-cooled hydrogen can be cooled to 20K (-253℃) using hydrogen and helium to perform liquefaction. Joule-Thomson expansion using a Joule-Thomson valve can be performed in the main cooling process. In other words, cooling to 20K (-253℃) is required for liquefaction at atmospheric pressure.

[0008] Therefore, to achieve high efficiency in the entire hydrogen liquefaction process, it is necessary to optimize the pre-cooling and main-cooling processes through an efficient configuration.

[0009] The objective of the present invention is to provide a high-efficiency hydrogen liquefaction system and a hydrogen liquefaction process by efficiently configuring the pre-cooling process and the main cooling process.

[0010] In one example, a high-efficiency hydrogen liquefaction system comprises: a cooling cycle section (10) including a first pre-cooling cycle (100) arranged to circulate a first pre-cooling refrigerant and a main cooling cycle (300) arranged to circulate a main cooling refrigerant; a cooling line section (20) through which a cooling target to be cooled by the cooling cycle section (10) passes; and a heat exchange section (30) including a plurality of heat exchangers that exchange heat between the cooling cycle section (10) and the cooling line section (20), wherein, among the plurality of heat exchangers, the heat exchanger that exchanges heat with the first pre-cooling cycle (100) is referred to as a high-temperature heat exchanger, and wherein the main cooling cycle (300) includes a main cooling line through which the main cooling refrigerant passes, and wherein the main cooling cycle may include a bypass line that branches off from one point of the main cooling line and bypasses the main cooling line so as not to exchange heat with only at least one of the high-temperature heat exchangers among the plurality of heat exchangers, and joins to another point of the main cooling line.

[0011] In another example, a high-efficiency hydrogen liquefaction system comprises: a cooling cycle section (10) comprising a first pre-cooling cycle (100) configured to circulate a first pre-cooling refrigerant and a main cooling cycle (300) configured to circulate a main cooling refrigerant; a cooling line section (20) through which a cooling target to be cooled by the cooling cycle section (10) passes; and a heat exchange section (30) comprising a plurality of heat exchangers that exchange heat between the cooling cycle section and the cooling line section, wherein the main cooling cycle (300) comprises: a main main cooling line (310); and a first main cooling line (320) which branches off from a first main cooling branch point (311) of the main main cooling line (310) and joins to a first main cooling confluence point which is a point of the main main cooling line (310). The system includes a second main cooling line (330) that branches off from a second main cooling branch point (312) of the main main cooling line (310) and joins to a second main cooling confluence point which is a point of the main main cooling line (310) or the first main cooling line (320); and a main cooling bypass line (340) that branches off from a third main cooling branch point (316) of the second main cooling line (330) and joins to the second main cooling confluence point without exchanging heat with at least one of the heat exchangers through which the first pre-cooling cycle passes among the plurality of heat exchangers, wherein the second main cooling branch point (312) may be located downstream of the first main cooling branch point (311).

[0012] In another example, the main cooling cycle (300) may further include a main cooling expansion valve (314) positioned downstream of the second main cooling branch point (312) of the main main cooling line (310); and a main main cooling compressor (315) positioned downstream of the main cooling expansion valve (314).

[0013] In another example, the above-mentioned main cooling cycle (300) may further include a first main cooling expander (321) disposed in the first main cooling line (320); and a second main cooling expander (331) disposed in the second main cooling line (330).

[0014] In another example, the main cooling cycle (300) may further include a first main cooling compressor (322) positioned in the first main cooling line (320) and downstream of the first main cooling expander (321); and a second main cooling compressor (332) positioned in the second main cooling line (330) and downstream of the second main cooling expander.

[0015] In another example, the first pre-cooling cycle (100) comprises: a first gas-liquid separator (110) configured to separate the gas and liquid of the first pre-cooling refrigerant introduced; a first pre-cooling line (120) configured to allow the gaseous pre-cooling refrigerant discharged from the first gas-liquid separator (110) to pass through; a second pre-cooling line (130) configured to allow the liquid pre-cooling refrigerant discharged from the first gas-liquid separator (110) to pass through; a connecting pre-cooling line (140) connected to the first pre-cooling line (120) and the second pre-cooling line (130); a second gas-liquid separator (150) configured to separate the gas and liquid of the refrigerant introduced from the connecting pre-cooling line; and a third pre-cooling line (160) configured to allow the gaseous pre-cooling refrigerant discharged from the second gas-liquid separator (150) to pass through and connected to the first gas-liquid separator. It may include a fourth pre-cooling line (170) connected to the second pre-cooling line (130) through which the liquid pre-cooling refrigerant discharged from the second gas-liquid separator (150) passes; and a fifth pre-cooling line (180) connected to the second pre-cooling line (130) and the fourth pre-cooling line.

[0016] In another example, the first pre-cooling cycle (100) may further include: a first pre-cooling expansion valve (121) disposed in the first pre-cooling line (120); a first pre-cooling compressor (122) disposed in the first pre-cooling line (120) and downstream of the first pre-cooling expansion valve (121); a second pre-cooling expansion valve (131) disposed in the fifth pre-cooling line (180); and a second pre-cooling compressor (132) disposed in the fifth pre-cooling line (180) and downstream of the second pre-cooling expansion valve (131).

[0017] In another example, the first pre-cooling cycle (100) may further include a third pre-cooling compressor (161) disposed in the third pre-cooling line (160); and a pre-cooling pump (171) disposed in the fourth pre-cooling line (170) and configured to pump the pre-cooling refrigerant in the fourth pre-cooling line toward the second pre-cooling line (130).

[0018] In another example, the apparatus further comprises a second pre-cooling cycle (200) configured to circulate a second pre-cooling refrigerant that performs cooling at a lower temperature than the first pre-cooling refrigerant, wherein the second pre-cooling cycle (200) comprises: a second-1 gas-liquid separator (210) configured to separate the second pre-cooling refrigerant from the gas phase and liquid phase; a second-1 pre-cooling line (220) configured to allow the gaseous second pre-cooling refrigerant discharged from the second-1 gas-liquid separator (210) to pass through; a second-2 pre-cooling line (230) configured to allow the liquid second pre-cooling refrigerant discharged from the second-1 gas-liquid separator (210) to pass through; and a second-2 gas-liquid separator (240) connected to the second-1 pre-cooling line (220) configured to separate the second pre-cooling refrigerant from the second-1 pre-cooling line (220) from the gas phase and liquid phase. It may include a second-3 pre-cooling line (250) through which a second pre-cooling refrigerant in the gas phase discharged from the second-2 gas-liquid separator (240) passes; a second-4 pre-cooling line (260) through which a second pre-cooling refrigerant in the liquid phase discharged from the second-2 gas-liquid separator (240) passes; a second-6 pre-cooling line (280) connected to the second-3 pre-cooling line (250) and the second-4 pre-cooling line (260); and a second-7 pre-cooling line (290) connected to at least one of the second-2 pre-cooling line (230) or the second-6 pre-cooling line (280), and connected to the second-1 gas-liquid separator to allow the second pre-cooling refrigerant to flow into the second-1 gas-liquid separator.

[0019] In another example, the second pre-cooling cycle (200) may further include a second-1 pre-cooling expander (221) placed in the second-1 pre-cooling line (220); and a second-2 pre-cooling expander (251) placed in the second-3 pre-cooling line (250).

[0020] In another example, the second pre-cooling cycle (200) may further include a second-1 pre-cooling expansion valve (231) disposed in the second-2 pre-cooling line (230); and a second-1 pre-cooling compressor (232) disposed in the second-2 pre-cooling line (230) and disposed downstream of the second-1 pre-cooling expansion valve (231).

[0021] In another example, the second pre-cooling cycle (200) may further include a second-2 pre-cooling expansion valve (261) disposed in the second-4 pre-cooling line; and a second-3 pre-cooling compressor (282) disposed in the second-6 pre-cooling line (280).

[0022] In another example, the heat exchanger (30) comprises a first heat exchanger (31) configured to exchange heat between the first pre-cooling cycle (100) and the main cooling cycle (300) and the cooling line section (20); The first pre-cooling cycle (100) and the main cooling cycle (300) are arranged to exchange heat with the cooling line section (20), and include a second heat exchanger (32) that passes downstream of the point where the first heat exchanger (31) passes in the cooling line section (20), and the first heat exchanger (31) is arranged so that the first pre-cooling line (120), the fifth pre-cooling line (180), the main main cooling line (310), the first main cooling line (320), and the second main cooling line (330) pass through, and the second heat exchanger (32) can be arranged so that the first pre-cooling line (120), the main main cooling line (310), the first main cooling line (320), and the second main cooling line (330) pass through.

[0023] In another example, the first pre-cooling cycle (100) comprises: a first gas-liquid separator (110) configured to separate the gas and liquid of the first pre-cooling refrigerant introduced; a first pre-cooling line (120) configured to allow the gaseous pre-cooling refrigerant discharged from the first gas-liquid separator (110) to pass through; a second pre-cooling line (130) configured to allow the liquid pre-cooling refrigerant discharged from the first gas-liquid separator (110) to pass through; a connecting pre-cooling line (140) connected to the first pre-cooling line (120) and the second pre-cooling line (130); a second gas-liquid separator (150) configured to separate the gas and liquid of the refrigerant introduced from the connecting pre-cooling line; and a third pre-cooling line (160) configured to allow the gaseous pre-cooling refrigerant discharged from the second gas-liquid separator (150) to pass through and connected to the first gas-liquid separator. A fourth pre-cooling line (170) connected to the second pre-cooling line (130) through which the liquid pre-cooling refrigerant discharged from the second gas-liquid separator (150) passes; and a fifth pre-cooling line (180) connected to the second pre-cooling line (130) and the fourth pre-cooling line, wherein the heat exchanger (30) comprises a first heat exchanger (31) configured to exchange heat between the first pre-cooling cycle (100), the second pre-cooling cycle (100), and the main cooling cycle (300) with the cooling line section (20);and is configured to exchange heat between the first pre-cooling cycle (100), the second pre-cooling cycle (100), and the main cooling cycle (300) with the cooling line section (20), and includes a second heat exchanger (32) that passes downstream of the point where the first heat exchanger (31) passes in the cooling line section (20), and the first heat exchanger (31) is arranged so that the first pre-cooling line (120), the fifth pre-cooling line (180), the second-seventh pre-cooling line (290), the second-second pre-cooling line (230), the second-sixth pre-cooling line (280), the main main cooling line (310), the first main cooling line (320), and the second main cooling line (330) pass through, and the second heat exchanger (32) is arranged so that the first pre-cooling line (120), the second-seventh pre-cooling line (290), and the second-second pre-cooling line (230) The 2-6 pre-cooling line (280), main main cooling line (310), 1 main cooling line (320), and 2 main cooling line (330) may be arranged to pass through.

[0024] In another example, the heat exchanger (30) comprises: a third heat exchanger (33) configured to exchange heat between the second pre-cooling cycle (200) and the main cooling cycle (300) and the cooling line section (20); a fourth heat exchanger (34) configured to exchange heat between the second pre-cooling cycle (200) and the main cooling cycle (300) and the cooling line section (20), with the downstream portion of the cooling line section (20) passing through the point where the third heat exchanger (33) passes; and a fifth heat exchanger (35) configured to exchange heat between the second pre-cooling cycle (200) and the main cooling cycle (300) and the cooling line section (20), with the downstream portion of the cooling line section (20) passing through the point where the fourth heat exchanger (34) passes. And the second pre-cooling cycle (200) and the main cooling cycle (300) are arranged to exchange heat with the cooling line section (20), and may include a sixth heat exchanger (36) that passes downstream of the point where the fifth heat exchanger (35) passes in the cooling line section (20).

[0025] In another example, the third heat exchanger (33), the fourth heat exchanger (34), and the fifth heat exchanger (35) may be positioned so that the second-6 pre-cooling line (280) passes through them, the sixth heat exchanger (36) may be positioned so that the second-3 pre-cooling line (250) passes through it, the third heat exchanger (33) may be positioned so that the second-2 pre-cooling line (230) and the second-7 pre-cooling line (290) pass through it, and the fifth heat exchanger (35) may be positioned so that the second-1 pre-cooling line (220) passes through it.

[0026] In another example, the heat exchanger (30) comprises: a seventh heat exchanger (37) arranged to exchange heat between the main cooling cycle (300) and the cooling line section (20); an eighth heat exchanger (38) arranged to exchange heat between the main cooling cycle (300) and the cooling line section (20), with the downstream portion of the cooling line section (20) passing through the point where the seventh heat exchanger (37) passes; and a ninth heat exchanger (39) arranged to exchange heat between the main cooling cycle (300) and the cooling line section (20), with the downstream portion of the cooling line section (20) passing through the point where the eighth heat exchanger (38) passes. And the above main cooling cycle (300) and the above cooling line section (20) are arranged to exchange heat, and may include a 10th heat exchanger (40) that passes downstream of the point where the 9th heat exchanger (39) passes in the above cooling line section (20).

[0027] In another example, the seventh heat exchanger and the eighth heat exchanger are positioned so that a portion of the main main cooling line passes between the first main cooling branch point (311) and the second main cooling branch point (312), and the seventh heat exchanger is positioned so that the main main cooling line (310), the first main cooling line (320), and the second main cooling line (330) pass through, and the eighth heat exchanger is positioned so that the main main cooling line (310) and the second main cooling line (330) pass through.

[0028] In another example, the ninth heat exchanger (39) and the tenth heat exchanger (40) are positioned so that the portion of the main main cooling line (310) located between the second main cooling branch point (312) and the main cooling expansion valve (314) passes through, the ninth heat exchanger (39) is positioned so that the main main cooling line (310) and the second main cooling line (330) pass through, and the tenth heat exchanger (40) can be positioned so that the main main cooling line (310) passes through.

[0029] In another example, the third main cooling branch point (316) is located between the first heat exchanger (31) and the second heat exchanger (32), and the main cooling bypass line (340) may not pass through the first heat exchanger (31).

[0030] For example, a hydrogen liquefaction system comprises: a cooling cycle section (10) including a first pre-cooling cycle (100) arranged to circulate a first pre-cooling refrigerant and a main cooling cycle (300) arranged to circulate a main cooling refrigerant; a cooling line section (20) through which a cooling target to be cooled by the cooling cycle section (10) passes; and a heat exchange section (30) including a plurality of heat exchangers that exchange heat between the cooling cycle section (10) and the cooling line section, wherein the main cooling cycle (300) comprises: a main main cooling line (310); a third main cooling line (350) branched from a fourth main cooling branch point (317) of the main main cooling line (310) and joined to a third main cooling junction point, which is a point of the main main cooling line (310); and a third main cooling expander (351) and a fourth main cooling expander (352) arranged in series on the third main cooling line (350). The system includes a second main cooling bypass line (360) that branches off from the fifth main cooling branch point (318) of the third main cooling line (350) and joins the third main cooling confluence point without exchanging heat with at least one of the plurality of heat exchangers, and the fifth main cooling branch point (318) may be located downstream of the fourth main cooling branch point (317).

[0031] In another example, the heat exchange section (30) comprises: a first heat exchanger (31) configured to exchange heat between the first pre-cooling cycle (100) and the main cooling cycle (300) and the cooling line section (20); and a second heat exchanger (32) configured to exchange heat between the first pre-cooling cycle (100) and the main cooling cycle (300) and the cooling line section (20), wherein the downstream of the point where the first heat exchanger (31) passes in the cooling line section (20) passes, and the fifth main cooling branch point (318) is located between the first heat exchanger (31) and the second heat exchanger (32), and the second main cooling bypass line (360) may not pass through the first heat exchanger (31).

[0032] In another example, the apparatus further includes a second pre-cooling cycle (200) configured to circulate a second pre-cooling refrigerant that performs cooling at a lower temperature compared to the first pre-cooling refrigerant, wherein the first heat exchanger (31) and the second heat exchanger (32) are each configured to further heat exchange the second pre-cooling cycle (200) with the cooling line section (20), and the second pre-cooling cycle (200) comprises: a second-1 gas-liquid separator (210) configured to separate the incoming second pre-cooling refrigerant from the gas; a second-1 pre-cooling line (220) configured to allow the gaseous second pre-cooling refrigerant discharged from the second-1 gas-liquid separator (210) to pass through; and a second-2 pre-cooling line (230) configured to allow the liquid second pre-cooling refrigerant discharged from the second-1 gas-liquid separator (210) to pass through. A second-2 gas-liquid separator (240) connected to the second-1 pre-cooling line (220) and configured to separate the second pre-cooling refrigerant flowing in from the second-1 pre-cooling line (220); a second-3 pre-cooling line (250) configured to allow the gaseous second pre-cooling refrigerant discharged from the second-2 gas-liquid separator (240) to pass through; a second-4 pre-cooling line (260) configured to allow the liquid second pre-cooling refrigerant discharged from the second-2 gas-liquid separator (240) to pass through; and a second-6 pre-cooling line (280) connected to the second-3 pre-cooling line (250) and the second-4 pre-cooling line (260). and may include a 2-7 pre-cooling line (290) connected to at least one of the 2-2 pre-cooling line (230) or the 2-6 pre-cooling line (280), and connected to the 2-1 gas-liquid separator to allow the 2-1 pre-cooling refrigerant to flow into the 2-1 gas-liquid separator.

[0033] For example, a high-efficiency hydrogen liquefaction process using a hydrogen liquefaction system can be provided.

[0034] According to the present invention, a highly efficient hydrogen liquefaction system and hydrogen liquefaction process can be obtained by efficiently configuring the pre-cooling process and the main cooling process.

[0035] Figure 1 is a conceptual diagram showing the flow of an exemplary hydrogen liquefaction process.

[0036] Figure 2 is a conceptual diagram showing the temperature range of an exemplary hydrogen liquefaction process.

[0037] Figure 3 is a pressure-temperature graph showing the Joule-Thomson coefficients of each material.

[0038] FIG. 4 is a conceptual diagram showing a high-efficiency hydrogen liquefaction system according to an embodiment of the present invention.

[0039] am.

[0040] Figure 5 is a graph comparing energy consumption according to the main cooling bypass structure.

[0041] FIG. 6 is a conceptual diagram showing a high-efficiency hydrogen liquefaction system according to another embodiment of the present invention.

[0042] FIG. 7 is a conceptual diagram showing a high-efficiency hydrogen liquefaction system according to another embodiment of the present invention.

[0043] FIG. 8 is a conceptual diagram showing a high-efficiency hydrogen liquefaction system according to another embodiment of the present invention.

[0044] Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. In assigning reference numerals to the components of each drawing, the same components are given the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the embodiments of the present invention, if it is determined that a detailed description of related known components or functions would hinder understanding of the embodiments of the present invention, such detailed description is omitted.

[0045] In addition, terms such as first, second, A, B, (a), (b), etc., may be used when describing the components of the embodiments of the present invention. These terms are intended only to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by the terms. Where it is stated that a component is "connected," "combined," or "connected" to another component, it should be understood that the component may be directly connected or connected to the other component, but that another component may also be "connected," "combined," or "connected" between each component.

[0046] Meanwhile, in this specification, the expressions upstream and downstream may be based on the direction of fluid flow. For example, if the fluid flows from left to right, the left side may correspond to upstream and the right side to downstream.

[0047] Basic structure of high-efficiency hydrogen liquefaction system and hydrogen liquefaction process

[0048] According to the present invention, a high-efficiency hydrogen liquefaction system and a hydrogen liquefaction process may be provided, comprising: a cooling cycle section including a first pre-cooling cycle arranged to circulate a first pre-cooling refrigerant and a main cooling cycle arranged to circulate a main cooling refrigerant; a cooling line section through which a cooling target to be cooled by the cooling cycle section passes; and a heat exchange section including a plurality of heat exchangers that exchange heat with the cooling cycle section and the cooling line section, wherein, among the plurality of heat exchangers, the heat exchanger that exchanges heat with the first pre-cooling cycle is referred to as a high-temperature heat exchanger, wherein the main cooling cycle includes a main cooling line through which the main cooling refrigerant passes, and wherein the main cooling cycle includes a bypass line that branches off from one point of the main cooling line and bypasses the main cooling line so as not to exchange heat with only at least one of the high-temperature heat exchangers among the plurality of heat exchangers, and joins to another point of the main cooling line.

[0049] First embodiment

[0050] FIG. 4 is a conceptual diagram showing a high-efficiency hydrogen liquefaction system according to a first embodiment of the present invention. The high-efficiency hydrogen liquefaction system according to the first embodiment of the present invention may include a cooling cycle section (10), a cooling line section (20), and a heat exchange section (30). The cooling cycle section (10) may include a first pre-cooling cycle (100) and a main cooling cycle (300). In the specification of the present invention, the term "cycle" may refer to a closed circuit that undergoes compression, condensation, expansion, and evaporation processes. The evaporation and condensation processes may occur through the heat exchange section (30) described later.

[0051] The first pre-cooling cycle (100) may be configured to circulate a first pre-cooling refrigerant. For example, the first pre-cooling refrigerant may be a mixed refrigerant comprising at least one of nitrogen, C1 (methane), C2 (ethane), C3 (propane) or C4 (butane) or a combination thereof.

[0052] In one embodiment, the first pre-cooling refrigerant may comprise 83 mol% or more and 97 mol% or less of one or more hydrocarbon compounds selected from the group consisting of 3 mol% or more and 17 mol% or less of a nitrogen compound and C1 to C4 hydrocarbon compounds.

[0053] Nitrogen is a low-boiling point substance, which is advantageous for hydrogen refrigerants; however, since nitrogen requires relatively more energy for compression, the Specific Energy Consumption (SEC), which is the energy consumed to liquefy 1 kg of hydrogen, increases as the content of the nitrogen compound increases, thus requiring an optimal nitrogen content. Accordingly, if the nitrogen compound of the first pre-cooling refrigerant satisfies the above content range within the mixed refrigerant, the hydrogen cooling efficiency can be increased and the energy consumption used to operate the hydrogen liquefaction system can be reduced.

[0054] The main cooling cycle (300) may be configured to circulate the main cooling refrigerant. For example, the main cooling refrigerant may be hydrogen. The main cooling refrigerant may further contain helium. While the main cooling discharge temperature is limited by the minimum temperature difference condition of the heat exchanger when only hydrogen is used as the main cooling refrigerant, adding helium to the main cooling refrigerant allows a lower temperature to be reached during expansion, which has the advantage of lowering the final cooling temperature.

[0055] The cooling line section (20) may be a section through which a cooling target passes, which is arranged to be cooled by the cooling cycle section (10). The cooling target may be hydrogen. Although the present specification describes gaseous hydrogen flowing into the cooling line section (20), being liquefied, and then discharged, any gaseous substance other than hydrogen may be applied and liquefied, and the cooling target is not limited to hydrogen.

[0056] The cooling line section (20) may include a cooling line (21). The cooling line (21) may be a line through which gaseous hydrogen can flow. In the specification of the present invention, the term "line" may refer to a structure arranged to allow fluid to flow through its interior. For example, the line may have a pipe shape, but even if it is not a pipe, it may be used as a line if fluid can flow through its interior.

[0057] The cooling line section (20) may include a cooling expansion valve (22). For example, the cooling expansion valve (22) may be a Joule-Thomson expansion valve for finally liquefying hydrogen cooled by the heat exchanger (30) by Joule-Thomson expansion. To increase expansion efficiency, the cooling expansion valve (22) may further include an expander that isentropically expands the hydrogen in the cooling line, and may be composed of a combination of the expansion valve and the expander. The expander can lower the temperature of the hydrogen and, incidentally, produce power from the expansion of the hydrogen.

[0058] The cooling line section (20) may include a cooling gas-liquid separator (23). The cooling gas-liquid separator (23) may be configured to separate the gas and liquid of hydrogen passing through the expansion valve (22) to finally obtain liquid hydrogen.

[0059] The heat exchanger (30) can exchange heat between the cooling cycle section (10) and the cooling line section (20). The heat exchanger (30) can perform a heat exchange process in the cycle. For example, the heat exchanger (30) can perform an evaporation process during the cycle. Additionally, the heat exchanger (30) can perform a condensation process during the cycle. The heat exchanger (30) can liquefy hydrogen passing through the cooling line section (20). The liquefied hydrogen can be discharged through the cooling line (21).

[0060] The heat exchanger (30) may include a plurality of heat exchangers and a plurality of conversion modules (30'). The conversion modules (30') may be placed in some of the plurality of heat exchangers. In the conversion modules (30'), ortho-para conversion, which converts ortho-hydrogen to para-hydrogen by cooling and a catalyst, may be performed. In the conversion modules (30'), cooling or condensation of hydrogen passing through a cooling line may occur.

[0061] 1st pre-cooling cycle (100)

[0062] The first pre-cooling cycle (100) may include a first gas-liquid separator (110), a first pre-cooling line (120), a second pre-cooling line (130), and a connecting pre-cooling line (140). The first gas-liquid separator (110) may be configured to separate the gas and liquid of the incoming first pre-cooling refrigerant. The first pre-cooling line (120) may be configured to allow the gaseous pre-cooling refrigerant discharged from the first gas-liquid separator (110) to pass through. The second pre-cooling line (130) may be configured to allow the liquid pre-cooling refrigerant discharged from the first gas-liquid separator (110) to pass through. The connecting pre-cooling line (140) may be connected to a fifth pre-cooling line (180) which is an extension of the first pre-cooling line (120) and the second pre-cooling line (130).

[0063] For example, a pre-cooling mixer (141) may be placed in the connecting pre-cooling line (140). The pre-cooling mixer (141) can mix the pre-cooling refrigerant flowing in from the fifth pre-cooling line (180), which is an extension of the first pre-cooling line (120) and the second pre-cooling line (130). This pre-cooling mixer (141) may be a conventional mixer. As another example, the pre-cooling mixer (141) may not be a separate mixer, but rather a connecting structure between the first pre-cooling line (120) and the second pre-cooling line (130) and the fifth pre-cooling line (180), that is, a structure that is interconnected to induce mixing of the pre-cooling refrigerants of each line.

[0064] The first pre-cooling cycle (100) may further include a second gas-liquid separator (150), a third pre-cooling line (160), and a fourth pre-cooling line (170). The second gas-liquid separator (150) may be configured to separate the gas and liquid of the refrigerant introduced from the connected pre-cooling line (140). The third pre-cooling line (160) may be configured to allow the gaseous pre-cooling refrigerant discharged from the second gas-liquid separator (150) to pass through and may be connected to the first gas-liquid separator (110). The fourth pre-cooling line (170) may be configured to allow the liquid pre-cooling refrigerant discharged from the second gas-liquid separator (150) to pass through and may be connected to the fifth pre-cooling line (180).

[0065] For example, a pre-cooling mixer (142) may be placed in the fifth pre-cooling line (180). The pre-cooling mixer (142) can mix the pre-cooling refrigerant flowing in from the second pre-cooling line (130) and the fourth pre-cooling line (170). This pre-cooling mixer (142) may be a conventional mixer. As another example, the pre-cooling mixer (142) may not be a separate mixer, but rather a connecting structure between the second pre-cooling line (130) and the fourth pre-cooling line (130), that is, a structure that is interconnected to induce mixing of the pre-cooling refrigerants of each line.

[0066] The first pre-cooling cycle (100) may include a first pre-cooling expansion valve (121), a first pre-cooling compressor (122), a second pre-cooling expansion valve (131), and a second pre-cooling compressor (132).

[0067] A first pre-cooling expansion valve (121) may be arranged in a first pre-cooling line (120) to expand the gaseous pre-cooling refrigerant discharged from a first gas-liquid separator (110). A first pre-cooling compressor (122) may be arranged to compress the pre-cooling refrigerant of the first pre-cooling line (120) that has been cooled through a heat exchanger (30).

[0068] A second pre-cooling expansion valve (131) may be arranged in a fifth pre-cooling line (180) connected to a second pre-cooling line (130) to expand the liquid pre-cooling refrigerant discharged from the first gas-liquid separator (110). A second pre-cooling compressor (132) may be arranged to compress the pre-cooling refrigerant of the fifth pre-cooling line (180) that has been cooled through the heat exchanger (30).

[0069] The first pre-cooling cycle (100) may further include a third pre-cooling compressor (161) and a pre-cooling pump (171). The third pre-cooling compressor (161) may be placed in the third pre-cooling line (160).

[0070] A third pre-cooling compressor (161) may be configured to compress the gaseous pre-cooling refrigerant discharged from the second gas-liquid separator (150). An aftercooler (not shown) may be disposed downstream of the third pre-cooling compressor (161). Likewise, an aftercooler (not shown) may be disposed downstream of all other compressors described above and below.

[0071] A pre-cooling pump (171) may be positioned in the fourth pre-cooling line (170) to pump liquid pre-cooling refrigerant within the fourth pre-cooling line (170) toward the fifth pre-cooling line (180).

[0072] Main cooling cycle (300)

[0073] The main cooling cycle (300) may include a main main cooling line (310), a first main cooling line (320), and a second main cooling line (330).

[0074] The first main cooling line (320) can be branched from the first main cooling branch point (311) of the main main cooling line (310) and joined to the first main cooling confluence point of the main main cooling line (310).

[0075] The second main cooling line (330) may branch off from the second main cooling branch point (312) of the main main cooling line (310) and join to the second main cooling confluence point of the main main cooling line (310). The second main cooling branch point (312) may be located downstream of the first main cooling branch point (311). For example, the first main cooling confluence point and the second main cooling confluence point may be the same point.

[0076] At this time, a cold mixing machine (313) may be placed at the first and second cold merging points.

[0077] The main cooling mixer (313) can mix the main cooling refrigerant flowing in from at least one of the main main cooling line (310), the first main cooling line (320), and the second main cooling line (330). This main cooling mixer (313) may be a conventional mixer. As another example, the main cooling mixer (313) may not be a separate mixer, but may be a connecting structure between the main main cooling line (310), the first main cooling line (320), and the second main cooling line (330), that is, a structure that is interconnected to induce mixing of the main cooling refrigerants of each line.

[0078] However, the first main cold confluence point and the second main cold confluence point do not necessarily have to coincide.

[0079] In the original cooling cycle (300), the conventionally used Claude cycle has a serial structure, so the expansion outlet flow discharged from the first expansion unit all flows into the second expansion unit, which can cause a problem of putting a load on the second compressor.

[0080] In the case of a high-efficiency hydrogen liquefaction system according to one embodiment of the present invention, by having a parallel structure and a separate compression structure, the expansion / compression sections and flow rates for each cooling target temperature can be configured independently to reduce the load on the compressor, and the refrigerant flow rate and expansion valve recovery pressure can be adjusted according to the cooling target temperature section, thereby increasing the freedom of process design. In other words, high hydrogen liquefaction efficiency can be obtained by efficiently configuring the main cooling process.

[0081] The main cooling cycle (300) may further include a main cooling expansion valve (314) and a main main cooling compressor (315). The main cooling expansion valve (314) may be positioned downstream of a second main cooling branch point (312) in the main main cooling line (310). The main cooling refrigerant separated at the second main cooling branch point (312) may flow into the main cooling expansion valve (314) and be expanded to a low pressure (LP). To increase expansion efficiency, the main cooling expansion valve (314) may further include an expander (not shown) that isentropically expands hydrogen in the cooling line, and may be composed of a combination of the expansion valve and the expander. The expander can lower the temperature of the hydrogen and, incidentally, produce power from the expansion of the hydrogen.

[0082] The main main cooling compressor (315) may be positioned downstream of the main cooling expansion valve (314) in the main main cooling line (310). The main main cooling compressor (315) may be configured to compress the main cooling refrigerant of the main main cooling line (310) that has been cooled through the heat exchanger (30).

[0083] The main cooling cycle (300) may further include a first main cooling expander (321) and a first main cooling compressor (322). The first main cooling expander (321) may be placed in the first main cooling line (220). The first main cooling expander (321) may be configured to expand the high-pressure (HP) main cooling refrigerant separated at the first main cooling branch point (311) into a refrigerant having a primary intermediate pressure (MP1). As an example, the first main cooling compressor (322) may be placed in the first main cooling line (320) and may be placed downstream of the first main cooling expander (321). The first main cooling compressor (322) may be configured to compress the main cooling refrigerant of the first main cooling line (320) that has been cooled through the heat exchanger (30). However, as another example, the first main cooling compressor (322', not shown) may be placed in the main main cooling line (310).

[0084] The main cooling cycle (300) may further include a second main cooling expander (331) and a second main cooling compressor (332). The second main cooling expander (331) may be placed in the second main cooling line (330). The second main cooling expander (331) may be configured to expand the high-pressure (HP) main cooling refrigerant separated at the second main cooling branch point (312) into a refrigerant having a secondary intermediate pressure (MP2). The second main cooling compressor (332) may be placed in the second main cooling line (330) but may be placed downstream of the second main cooling expander (331). The second main cooling compressor (332) may be configured to compress the main cooling refrigerant of the second main cooling line (330) that has been cooled through the heat exchanger (30). However, as another example, the second main cooling compressor (232', not shown) may be placed in the main main cooling line (310).

[0085] The compression ratio of the main main cooling compressor (315) may be greater than or equal to the compression ratio of the first main cooling compressor (322) and the second main cooling compressor (332). The compression ratio of the second main cooling compressor (332) may be greater than or equal to the compression ratio of the first main cooling compressor (322).

[0086] heat exchanger (30)

[0087] The heat exchange section (30) may include a first heat exchanger (31) and a second heat exchanger (32). The first heat exchanger (31) and the second heat exchanger (32) may be arranged to exchange heat between the first pre-cooling cycle (100) and the main cooling cycle (300) and the cooling line section (20). The second heat exchanger (32) may be positioned so that it passes downstream of the point where the first heat exchanger (31) passes through the cooling line section (20). The hydrogen in the cooling line section (20) that has passed through the second heat exchanger (32) may be at a lower temperature compared to the hydrogen in the cooling line section (20) that has passed through the first heat exchanger (31).

[0088] The first heat exchanger (31) may be positioned so that the first pre-cooling line (120) and the second pre-cooling line (130) extend to the fifth pre-cooling line (180). Additionally, the first heat exchanger (31) may be positioned so that the main main cooling line (310), the first main cooling line (320), and the second main cooling line (330) pass through it.

[0089] The second heat exchanger (32) may be positioned so that the first pre-cooling line (120) passes through it. This may mean that the second heat exchanger (32), unlike the first heat exchanger (31), does not pass through the second pre-cooling line (130) and the fifth pre-cooling line (180).

[0090] Additionally, the second heat exchanger (32) can be positioned so that the main main cooling line (310), the first main cooling line (320), and the second main cooling line (330) pass through it.

[0091] For example, a cryogenic adsorber (30”) may be placed through the second heat exchanger (32).

[0092] The heat exchanger (30) may further include a seventh heat exchanger (37), an eighth heat exchanger (38), a ninth heat exchanger (39), and a tenth heat exchanger (40). The seventh heat exchanger (37), the eighth heat exchanger (38), the ninth heat exchanger (39), and the tenth heat exchanger (40) may be arranged to exchange heat between the main cooling cycle (300) and the cooling line section (20).

[0093] The 8th heat exchanger (38) may be positioned so that it passes downstream of the point where the 7th heat exchanger (33) passes in the cooling line section (20). The 9th heat exchanger (39) may be positioned so that it passes downstream of the point where the 8th heat exchanger (34) passes in the cooling line section (20). The 10th heat exchanger (40) may be positioned so that it passes downstream of the point where the 9th heat exchanger (39) passes in the cooling line section (20).

[0094] The hydrogen in the cooling line section (20) that has passed through the 7th heat exchanger (37) may be at a lower temperature than the hydrogen in the cooling line section (20) that has passed through the 2nd heat exchanger (32). The hydrogen in the cooling line section (20) that has passed through the 8th heat exchanger (38) may be at a lower temperature than the hydrogen in the cooling line section (20) that has passed through the 7th heat exchanger (33). The hydrogen in the cooling line section (20) that has passed through the 9th heat exchanger (39) may be at a lower temperature than the hydrogen in the cooling line section (20) that has passed through the 8th heat exchanger (38). The hydrogen in the cooling line section (20) that has passed through the 10th heat exchanger (40) may be at a lower temperature than the hydrogen in the cooling line section (20) that has passed through the 9th heat exchanger (39).

[0095] The 7th heat exchanger (37) and the 8th heat exchanger (38) may be positioned so that the portion between the 1st main cooling branch point (311) and the 2nd main cooling branch point (312) of the main main cooling line (310) passes through. The 7th heat exchanger (37) may be positioned so that the main main cooling line (310), the 1st main cooling line (320), and the 2nd main cooling line (330) pass through. The 8th heat exchanger (38) may be positioned so that the main main cooling line (310) and the 2nd main cooling line (330) pass through. This may mean that, unlike the 7th heat exchanger (33), the 8th heat exchanger (38) does not pass through the 1st main cooling line (320).

[0096] The ninth heat exchanger (39) and the tenth heat exchanger (36) may be positioned so that the portion between the second main cooling branch point (312) and the main cooling expansion valve (314) of the main main cooling line (310) passes through it. The ninth heat exchanger (39) may be positioned so that the main main cooling line (310) and the second main cooling line (330) pass through it. The tenth heat exchanger (40) may be positioned so that the main main cooling line (310) passes through it. This may mean that, unlike the ninth heat exchanger (39), the second main cooling line (330) does not pass through the tenth heat exchanger (40).

[0097] Specifically, the main cooling refrigerant circulating through the main cooling line (310) passes sequentially from the 10th heat exchanger (40) through the 9th heat exchanger (39), the 8th heat exchanger (38), the 7th heat exchanger (37), the 2nd heat exchanger (32), and the 1st heat exchanger (31), thereby cooling the hydrogen in the cooling line section (20). In this process, the temperature of the hydrogen in the cooling line section (20) passing through each heat exchanger can be lowered as it goes from the 1st heat exchanger (31) to the 10th heat exchanger (40).

[0098] A switching module (30') may be placed in the second heat exchanger (32), the seventh heat exchanger (37), the eighth heat exchanger (38), the ninth heat exchanger (39), and the tenth heat exchanger (40).

[0099] For example, the main cooling refrigerant flowing into the 10th heat exchanger (10) can have a temperature of 20K.

[0100] Bypass line

[0101] The main cooling cycle (300) may include a main cooling bypass line (340) that branches off from the third main cooling branch point (316) of the second main cooling line (330) and joins the second main cooling joining point without exchanging heat with at least one of the heat exchangers through which the first pre-cooling cycle passes among the plurality of heat exchangers. Accordingly, some or all of the main cooling refrigerant in the second main cooling line (330) may not exchange heat with at least one of the heat exchangers through which the first pre-cooling cycle passes among the plurality of heat exchangers via the main cooling bypass line (340).

[0102] In the present specification, a heat exchanger through which the first pre-cooling cycle (100) passes may be referred to as a high-temperature heat exchanger. For example, in FIG. 4, the first heat exchanger (31) and the second heat exchanger (32) correspond to high-temperature heat exchangers because the first pre-cooling cycle (100) passes through them, and the 7th to 10th heat exchangers (37-40) do not correspond to high-temperature heat exchangers because the first pre-cooling cycle (100) does not pass through them. For example, in FIG. 6, the first and second heat exchangers (31, 32) correspond to high-temperature heat exchangers because the first pre-cooling cycle (100) passes through them, and the 3rd to 10th heat exchangers (33-40) do not correspond to high-temperature heat exchangers because the first pre-cooling cycle (100) does not pass through them. In this specification, a heat exchanger (33-36) through which the second pre-cooling cycle (200) and the main cooling cycle (300) pass without the first pre-cooling cycle (100) may be referred to as a medium-temperature heat exchanger. In this specification, a heat exchanger (37-40) through which the main cooling cycle (300) passes without the first pre-cooling cycle (100) and the second pre-cooling cycle (200) may be referred to as a low-temperature heat exchanger.

[0103] In one embodiment, the second main cooling junction point may be located downstream of the first heat exchanger (31) and upstream of the second main cooling compressor (332). At this time, a second main cooling mixer (333) may be placed at the second main cooling junction point.

[0104] The second main cooling mixer (333) can mix the main cooling refrigerant flowing in from at least one of the second main cooling line (330) and the main cooling bypass line (340). This second main cooling mixer (333) may be a conventional mixer. As another example, the second main cooling mixer (333) may not be a separate mixer, but may be a connecting structure between the second main cooling line (330) and the main cooling bypass line (340), that is, a structure that is interconnected to induce mixing of the main cooling refrigerants of each line.

[0105] Accordingly, according to the present invention, the main cooling refrigerant can partially bypass the pre-cooling section when recovered after expansion. By bypassing a portion of the pre-cooling section, the main cooling refrigerant is introduced into the compressor in a low-temperature state, thereby reducing compression energy and thus increasing energy efficiency.

[0106] However, the above bypass can transfer the main cooling load to pre-cooling. Specifically, due to the bypass of the main cooling refrigerant, the flow rate of the pre-cooling refrigerant required to cool the hydrogen increases, which may increase the pre-cooling energy consumption.

[0107] Therefore, an optimal bypass path can be determined by considering the relationship between the reduction in main cooling energy consumption and the increase in pre-cooling energy consumption. Specifically, the bypass path can be determined such that the main cooling refrigerant does not exchange heat exclusively with at least one of the high-temperature heat exchangers.

[0108] In the case of bypass path 1, the third main cooling branch point (316) in FIG. 4 may be located between the first heat exchanger (31) and the second heat exchanger (32). The main cooling refrigerant of the second main cooling line (330) passes through the second heat exchanger (32), but may not pass through the first heat exchanger (31) through the main cooling bypass line (340).

[0109] In the case of bypass path 2, the third main cooling branch point (316) in FIG. 4 may be located between the second heat exchanger (32) and the seventh heat exchanger (32). The main cooling refrigerant of the second main cooling line (330) does not pass through the second heat exchanger (32) via the main cooling bypass line (340), but may pass through the first heat exchanger (31).

[0110] In the case of bypass path 3, the third main cooling branch point (316) in FIG. 4 may be located between the second heat exchanger (32) and the seventh heat exchanger (32). The main cooling refrigerant of the second main cooling line (330) may not pass through both the first heat exchanger (31) and the second heat exchanger (32) through the main cooling bypass line (340).

[0111] Figure 5 is a graph comparing energy consumption according to the bypass structure. Specifically, for the above-mentioned bypass paths 1 to 3 and the case without a bypass, the specific energy consumption (SEC), which is the energy consumed to liquefy 1 kg of hydrogen, was calculated using the Aspen HYSYS simulator.

[0112] In Figure 5, when comparing the total energy consumption, the total energy consumption is reduced when there is a bypass path compared to when there is no bypass path, and the energy efficiency is improved.

[0113] In Figure 5, when comparing the pre-cooling energy consumption, for bypass paths 1 to 3, the main cooling refrigerant load is distributed to the pre-cooling due to the bypass, and thus the pre-cooling flow rate increases, resulting in an increase in pre-cooling energy consumption. Meanwhile, among bypass paths 1 to 3, the pre-cooling energy consumption of bypass path 1 was the lowest at 1.914 kWh / kg LH2. Therefore, considering the temperature range where the cooling load is distributed, bypassing the high-temperature range of the main cooling cycle can be effective in reducing the main cooling energy consumption.

[0114] In FIG. 5, when comparing the energy consumption of the main cooling, in the case of bypass paths 1 to 3, the main cooling load is distributed due to the bypass, and the compressor energy consumption is reduced, so the energy consumption of the main cooling is reduced compared to the case without the bypass. Bypass paths 1 and 3 can reduce the energy consumption of the refrigerant compression by partially bypassing the heat exchanger to lower the temperature of the refrigerant flowing into the compressor.

[0115] In this case, the results calculated using the Aspen HYSYS simulator showed that the first pre-cooling energy consumption was 1.914 kWh / kg LH2 and the main cooling energy consumption was 5.738 kWh / kg LH2. Therefore, the total energy consumption was 7.653 kWh / kg LH2.

[0116] 2nd embodiment

[0117] FIG. 6 is a conceptual diagram showing a hydrogen liquefaction system according to a second embodiment of the present invention. The hydrogen liquefaction system according to the second embodiment may further include a second pre-cooling cycle (200) in addition to the hydrogen liquefaction system according to the first embodiment. Specifically, the hydrogen liquefaction system according to the second embodiment may include a cooling cycle section (10), a cooling line section (20), and a heat exchange section (30), and the cooling cycle section (10) may include a first pre-cooling cycle (100), a second pre-cooling cycle (200), and a main cooling cycle (300).

[0118] In the second embodiment, unless specifically stated otherwise, other components excluding the second pre-cooling cycle (200) may be the same as those of the first embodiment.

[0119] The second pre-cooling cycle (200) may be configured to circulate a second pre-cooling refrigerant. For example, the second pre-cooling refrigerant may be a mixed refrigerant comprising at least one of nitrogen, hydrogen, helium, or a combination thereof.

[0120] The hydrogen liquefaction system according to the second embodiment includes a first pre-cooling cycle (100) and a second pre-cooling cycle (200), so that the second pre-cooling cycle (200) can distribute the cooling load of the main cooling cycle (300), thereby enabling the configuration of an efficient cooling cycle.

[0121] 1st pre-cooling cycle (100)

[0122] The hydrogen liquefaction system according to the second embodiment may include a first pre-cooling cycle (100) identical to that of the hydrogen liquefaction system according to the first embodiment. Therefore, unless otherwise stated, the description of the pre-cooling cycle of the first embodiment described above may be applied to the first pre-cooling cycle of the second embodiment.

[0123] 2nd pre-cooling cycle (200)

[0124] The second pre-cooling cycle (200) may include a second-1 gas-liquid separator (210), a second-1 pre-cooling line (220), and a second-2 pre-cooling line (230). The second-1 gas-liquid separator (210) may be configured to separate the gas and liquid of the second pre-cooling refrigerant being introduced.

[0125] The second-1 pre-cooling line (220) may be provided to allow the gaseous second pre-cooling refrigerant discharged from the second-1 gas-liquid separator (210) to pass through. The second-2 pre-cooling line (230) may be provided to allow the liquid second pre-cooling refrigerant discharged from the second-1 gas-liquid separator (210) to pass through.

[0126] The second pre-cooling cycle (200) may further include a second-2 gas-liquid separator (240), a second-3 pre-cooling line (250), a second-4 pre-cooling line (260), a second-6 pre-cooling line (280), and a second-7 pre-cooling line (290).

[0127] The second-2 gas-liquid separator (240) may be connected to the second-1 pre-cooling line (220) and configured to separate the second pre-cooling refrigerant flowing in from the second-1 pre-cooling line (220) into gas and liquid. The second-3 pre-cooling line (250) may be configured to allow the gaseous second pre-cooling refrigerant discharged from the second-2 gas-liquid separator (240) to pass through. The second-4 pre-cooling line (260) may be configured to allow the liquid second pre-cooling refrigerant discharged from the second-2 gas-liquid separator (240) to pass through.

[0128] The 2-6 pre-cooling line (280) can be connected to the 2-3 pre-cooling line (250) and the 2-4 pre-cooling line (260).

[0129] The 2-7 pre-cooling line (290) may be connected to at least one of the 2-2 pre-cooling line (230) and the 2-6 pre-cooling line (280). The 2-7 pre-cooling line (290) may be connected to the 2-1 gas-liquid separator (210) and arranged to introduce the 2-1 pre-cooling refrigerant into the 2-1 gas-liquid separator (210).

[0130] For example, a second-2 pre-cooling mixer (291) may be placed in the second-7 pre-cooling line (290). The second-2 pre-cooling mixer (291) can mix the second pre-cooling refrigerant flowing in from the second-2 pre-cooling line (230) and the second-6 pre-cooling line (280). This second-2 pre-cooling mixer (291) may be a conventional mixer. As another example, the second-2 pre-cooling mixer (291) may not be a separate mixer, but may refer to a connecting structure between the second-2 pre-cooling line (230) and the second-6 pre-cooling line (280), that is, a structure that is interconnected to induce mixing of the second pre-cooling refrigerants of each line.

[0131] The second pre-cooling cycle (200) may further include a second-1 pre-cooling expander (221). The second-1 pre-cooling expander (221) may be placed in the second-1 pre-cooling line (220). The second-1 pre-cooling expander (221) may be arranged to expand the gaseous second pre-cooling refrigerant discharged from the second-1 gas-liquid separator (210). The gaseous second pre-cooling refrigerant separated from the second-1 gas-liquid separator (210) may be introduced into the second-1 pre-cooling expander (221) and expanded to have a secondary intermediate pressure (MP2).

[0132] The second pre-cooling cycle (200) may further include a second-2 pre-cooling expander (251). The second-2 pre-cooling expander (251) may be placed in the second-3 pre-cooling line (250). The second-2 pre-cooling expander (251) may be arranged to expand the gaseous second pre-cooling refrigerant discharged from the second-2 gas-liquid separator (240).

[0133] The second pre-cooling cycle (200) may further include a second-1 pre-cooling expansion valve (231). The second-1 pre-cooling expansion valve (231) may be placed in the second-2 pre-cooling line (230). The second-1 pre-cooling expansion valve (231) may be arranged to expand the second pre-cooling refrigerant in liquid form discharged from the second-1 gas-liquid separator (210). The second pre-cooling refrigerant in liquid form separated from the second-1 gas-liquid separator (210) may be introduced into the second-1 pre-cooling expansion valve (231) and expanded to have a primary intermediate pressure (MP1).

[0134] The second pre-cooling cycle (200) may further include a second-2 pre-cooling expansion valve (261). The second-2 pre-cooling expansion valve (261) may be placed in the second-4 pre-cooling line (260). The second-2 pre-cooling expansion valve (261) may be configured to expand the second pre-cooling refrigerant in liquid form discharged from the second-2 gas-liquid separator (240).

[0135] The second pre-cooling cycle (200) may further include a second-1 pre-cooling compressor (232). The second-1 pre-cooling compressor (232) may be placed in the second-2 pre-cooling line (230) and may be placed downstream of the second-1 pre-cooling expansion valve (231). The second-1 pre-cooling compressor (232) may compress the second pre-cooling refrigerant that has passed through the third heat exchanger (33), the second heat exchanger (32), and the first heat exchanger (31), which will be described later. The second-1 pre-cooling compressor (232) may be configured to compress a refrigerant with a relatively heavy component (Heavy MR), such as nitrogen, among the second pre-cooling refrigerants. This structure has the effect of utilizing nitrogen, which is relatively low-cost among low-boiling point mixtures that can be used as refrigerants in the corresponding cooling section, as the main component.

[0136] The second pre-cooling cycle (200) may further include a second-third pre-cooling compressor (282). The second-third pre-cooling compressor (282) may be placed in the second-sixth pre-cooling line (280). The second-third pre-cooling compressor (282) may compress the second pre-cooling refrigerant that has passed through the sixth heat exchanger (36), the fifth heat exchanger (35), the fourth heat exchanger (34), the third heat exchanger (33), the second heat exchanger (32), and the first heat exchanger (31), which will be described later. The second-third pre-cooling compressor (282) may be configured to compress a relatively light component of the second pre-cooling refrigerant (Light MR) or a low-pressure refrigerant.

[0137] The compression ratio of the 2-3 pre-cooling compressor (282) may be greater than or equal to the compression ratio of the 2-1 pre-cooling compressor (232).

[0138] As another example, the second pre-cooling cycle (200) may also have a parallel structure and a separate compression structure, similar to the main cooling cycle (300). In this case, the degree of design freedom is increased, allowing the pre-cooling process to be configured efficiently.

[0139] Main cooling cycle (300)

[0140] The hydrogen liquefaction system according to the second embodiment may include the same main cooling cycle (300) as that of the hydrogen liquefaction system according to the first embodiment. Therefore, unless otherwise stated, the description of the main cooling cycle of the first embodiment described above may be applied to the main cooling cycle of the second embodiment.

[0141] heat exchanger (30)

[0142] The heat exchange section (30) may include a first heat exchanger (31) and a second heat exchanger (32). The first heat exchanger (31) and the second heat exchanger (32) may be arranged to exchange heat between the first pre-cooling cycle (100), the second pre-cooling cycle (200), the main cooling cycle (300), and the cooling line section (20). The second heat exchanger (32) may be positioned so that it passes downstream of the point where the first heat exchanger (31) passes through the cooling line section (20). As an example, a cryogenic adsorber (30”) may be positioned to pass through the second heat exchanger (32). The hydrogen in the cooling line section (20) that has passed through the second heat exchanger (32) may be at a lower temperature than the hydrogen in the cooling line section (20) that has passed through the first heat exchanger (31).

[0143] The first heat exchanger (31) may be positioned so that the first pre-cooling line (120) and the second pre-cooling line (130) pass through the fifth pre-cooling line (180). Additionally, the first heat exchanger (31) may be positioned so that the second-2 pre-cooling line (230), the second-6 pre-cooling line (280), and the second-7 pre-cooling line (290) pass through. Additionally, the first heat exchanger (31) may be positioned so that the main main cooling line (310), the first main cooling line (320), and the second main cooling line (330) pass through.

[0144] The second heat exchanger (32) may be positioned so that the first pre-cooling line (120) passes through it. This may mean that the second heat exchanger (32), unlike the first heat exchanger (31), does not pass through the second pre-cooling line (130) and the fifth pre-cooling line (180).

[0145] Additionally, the second heat exchanger (32) may be positioned so that the second-2 pre-cooling line (230), the second-6 pre-cooling line (280), and the second-7 pre-cooling line (290) pass through it. Additionally, the second heat exchanger (32) may be positioned so that the main main cooling line (310), the first main cooling line (320), and the second main cooling line (330) pass through it.

[0146] The heat exchanger (30) may further include a third heat exchanger (33), a fourth heat exchanger (34), a fifth heat exchanger (35), and a sixth heat exchanger (36). The third heat exchanger (33), the fourth heat exchanger (34), the fifth heat exchanger (35), and the sixth heat exchanger (36) may be arranged to exchange heat between the second pre-cooling cycle (200) and the main cooling cycle (300) and the cooling line section (20).

[0147] The fourth heat exchanger (34) may be positioned so that it passes downstream of the point where the third heat exchanger (33) passes in the cooling line section (20). The fifth heat exchanger (35) may be positioned so that it passes downstream of the point where the fourth heat exchanger (34) passes in the cooling line section (20). The sixth heat exchanger (36) may be positioned so that it passes downstream of the point where the fifth heat exchanger (35) passes in the cooling line section (20).

[0148] The hydrogen in the cooling line section (20) that has passed through the third heat exchanger (33) may be at a lower temperature than the hydrogen in the cooling line section (20) that has passed through the second heat exchanger (32). The hydrogen in the cooling line section (20) that has passed through the fourth heat exchanger (34) may be at a lower temperature than the hydrogen in the cooling line section (20) that has passed through the third heat exchanger (33). The hydrogen in the cooling line section (20) that has passed through the fifth heat exchanger (35) may be at a lower temperature than the hydrogen in the cooling line section (20) that has passed through the fourth heat exchanger (34). The hydrogen in the cooling line section (20) that has passed through the sixth heat exchanger (36) may be at a lower temperature than the hydrogen in the cooling line section (20) that has passed through the fifth heat exchanger (35).

[0149] The third heat exchanger (33) may be positioned so that the second-2 pre-cooling line (230), the second-6 pre-cooling line (280), and the second-7 pre-cooling line (290) pass through it. Additionally, the third heat exchanger (33) may be positioned so that the main main cooling line (310), the first main cooling line (320), and the second main cooling line (330) pass through it.

[0150] The fourth heat exchanger (34) may be positioned so that the second-6 pre-cooling line (280) passes through it. This may mean that, unlike the third heat exchanger (33), the fourth heat exchanger (34) does not pass through the second-2 pre-cooling line (230) and the second-7 pre-cooling line (290). Additionally, the fourth heat exchanger (34) may be positioned so that the main main cooling line (310), the first main cooling line (320), and the second main cooling line (330) pass through it.

[0151] The fifth heat exchanger (35) may be positioned so that the second-1 pre-cooling line (220) passes through it. Additionally, the fifth heat exchanger (35) may be positioned so that the second-6 pre-cooling line (280) passes through it. Additionally, the fifth heat exchanger (35) may be positioned so that the main main cooling line (310), the first main cooling line (320), and the second main cooling line (330) pass through it.

[0152] The sixth heat exchanger (36) may be positioned so that the second-third pre-cooling line (250) passes through it. This may mean that the sixth heat exchanger (36) does not pass through the second-first pre-cooling line (220), unlike the fifth heat exchanger (35). Additionally, the sixth heat exchanger (36) may be positioned so that the main main cooling line (310), the first main cooling line (320), and the second main cooling line (330) pass through it.

[0153] The heat exchange section (30) may further include a seventh heat exchanger (37), an eighth heat exchanger (38), a ninth heat exchanger (39), and a tenth heat exchanger (40) sequentially downstream of the point where the sixth heat exchanger (36) passes in the cooling line section (20). The seventh heat exchanger (37), the eighth heat exchanger (38), the ninth heat exchanger (39), and the tenth heat exchanger (40) may be arranged to exchange heat between the main cooling cycle (300) and the cooling line section (20).

[0154] The hydrogen liquefaction system according to the second embodiment may include the same seventh heat exchanger (37), eighth heat exchanger (38), ninth heat exchanger (39), and tenth heat exchanger (40) as those of the hydrogen liquefaction system according to the first embodiment. Therefore, unless otherwise stated, the description of the seventh heat exchanger (37), eighth heat exchanger (38), ninth heat exchanger (39), and tenth heat exchanger (40) of the first embodiment described above may be applied to the seventh heat exchanger (37), eighth heat exchanger (38), ninth heat exchanger (39), and tenth heat exchanger (40) of the second embodiment.

[0155] Bypass line

[0156] The hydrogen liquefaction system according to the second embodiment may include the same bypass line (340) as that of the hydrogen liquefaction system according to the first embodiment. Therefore, unless otherwise stated, the description of the bypass line (340) of the first embodiment described above may be applied to the bypass line (340) of the second embodiment.

[0157] In FIG. 6, the third main cooling branch point (316) may be located between the first heat exchanger (31) and the second heat exchanger (32). The main cooling refrigerant of the second main cooling line (330) passes through the second heat exchanger (32) but may not pass through the first heat exchanger (31) via the main cooling bypass line (340). In this case, as a result calculated using the Aspen HYSYS simulator, the first pre-cooling energy consumption was 1.379 kWh / kg LH2, the second pre-cooling energy consumption was 1.348 kWh / kg LH2, and the main cooling energy consumption was 4.826 kWh / kg LH2. Therefore, the total energy consumption was 7.553 kWh / kg LH2.

[0158] Third embodiment

[0159] FIG. 7 is a conceptual diagram showing a high-efficiency hydrogen liquefaction system according to a third embodiment of the present invention. The hydrogen liquefaction system according to the third embodiment may include a cooling cycle section (10), a cooling line section (20), and a heat exchange section (30), and the cooling cycle section (10) may include a first pre-cooling cycle (100) and a main cooling cycle (300).

[0160] However, the hydrogen liquefaction system according to the third embodiment is a modified version of the hydrogen liquefaction system according to the first embodiment, in which the main cooling cycle (300) is changed. Specifically, the third main cooling expander (351) and the fourth main cooling expander (352) are arranged in parallel in the first embodiment, and in series in the third embodiment.

[0161] Accordingly, in the third embodiment, unless specifically stated otherwise, other components excluding the main cooling cycle (300) may be the same as those of the first embodiment.

[0162] 1st pre-cooling cycle (100)

[0163] The hydrogen liquefaction system according to the third embodiment may include a first pre-cooling cycle (100) identical to that of the hydrogen liquefaction system according to the first embodiment. Therefore, unless otherwise stated, the description of the pre-cooling cycle (100) of the first embodiment described above may be applied to the first pre-cooling cycle (100) of the third embodiment.

[0164] Main cooling cycle (300)

[0165] The main cooling cycle (300) may include a main main cooling line (310) and a third main cooling line (350). The third main cooling line (350) may branch off from the fourth main cooling branch point (317) of the main main cooling line (310) and join to the third main cooling confluence point, which is a point of the main main cooling line (310). A third main cooling expander (351) and a fourth main cooling expander (352) may be arranged in series in the third main cooling line (350).

[0166] The main cooling cycle (300) may include a liquefaction separation means (319) located downstream of the fourth main cooling branch point (317) from the main main cooling line (310). The liquefaction separation means (319) may separate the phases of the main cooling refrigerant for liquefaction. The main cooling cycle (300) may include a main cooling low-pressure liquid phase line (371) and a main cooling low-pressure gas phase line (372) connected to the liquefaction separation means (319). The main cooling low-pressure liquid phase line (371) is a line through which the liquid portion of the main cooling refrigerant for liquefaction separated from the liquefaction separation means (319) flows. The liquid portion of the main cooling refrigerant for liquefaction transferred from the liquefaction separation means (319) to the main cooling low-pressure liquid phase line (371) may have a temperature of 20K. The main cooling low-pressure gas line (372) is a line through which the gaseous portion of the main cooling refrigerant for liquefaction separated from the liquefaction separation means (319) flows. The main cooling low-pressure liquid line (371) can cool the hydrogen flowing in the cooling line (21) before it passes through the eighth heat exchanger (38-2) and is transferred to the main expansion valve (22). The main cooling low-pressure gas line (372) is connected to the main cooling low-pressure liquid line (371) that has passed through the eighth heat exchanger (38-2), so that the gaseous portion of the main cooling refrigerant for liquefaction flowing in the main cooling low-pressure gas line (372) can be combined with the liquid portion of the main cooling refrigerant for liquefaction flowing in the main cooling low-pressure liquid line (371).

[0167] The main cooling cycle (300) may include a main cooling low-pressure recovery line (373). The main cooling low-pressure recovery line (373) may extend from the point where the main cooling low-pressure liquid phase line (371) and the main cooling low-pressure gas phase line (372) merge. The main cooling low-pressure recovery line (373) may pass through the seventh heat exchanger (37-2), the sixth heat exchanger (36-2), the fifth heat exchanger (35-2), the fourth heat exchanger (34-2), the third heat exchanger (33-2), the second heat exchanger (32), and the first heat exchanger (31) in order to cool other refrigerants or hydrogen passing through the first to seventh heat exchangers described above.

[0168] The main cooling cycle (300) may include a plurality of compressors. The plurality of compressors may compress the main cooling refrigerant for liquefaction passing through the liquefaction line. The compressors may include turbines operated by power, etc. The plurality of compressors may include a first compressor (374) placed in the third main cooling low-pressure recovery line (373). The first compressor (374) may be placed downstream of the first heat exchanger (31) based on the direction in which the main cooling refrigerant for liquefaction flows in the main cooling low-pressure recovery line (373). The first compressor (374) may compress the main cooling refrigerant for liquefaction flowing in the main cooling low-pressure recovery line (373). The main cooling refrigerant discharged from the first compressor (374) may be joined to a first main cooling junction point, which is a point on the main main cooling line (310).

[0169] A third main cooling mixer (376) may be placed at the third main cooling confluence point. The third main cooling mixer (376) can mix the main cooling refrigerant flowing in from the third main cooling line (350), the main cooling low-pressure recovery line (373), and the bypass line (360) described later. This third main cooling mixer (376) may be a conventional mixer. As another example, the third main cooling mixer (376) may not be a separate mixer, but rather a connecting structure between the third main cooling line (350), the main cooling low-pressure recovery line (373), and the bypass line (360), that is, a structure that is interconnected to induce mixing of the main cooling refrigerants of each line. The main cooling refrigerant discharged from the third main cooling mixer (376) may be introduced into and compressed by the second compressor (375) placed in the main main cooling line (310).

[0170] The main cooling cycle (300) may include a main cooling expansion valve (314). The main cooling expansion valve (314) may be a Joule-Thomson expansion valve for Joule-Thomson expansion of hydrogen. The main cooling expansion valve (314) may be located downstream of the eighth heat exchanger (38-2) with respect to the direction in which the main cooling refrigerant flows in the main main cooling line (310). Thus, the main cooling expansion valve (314) can cause expansion of the main cooling refrigerant that has flowed through the main main cooling line (310) and been cooled, thereby transferring the liquefied main cooling refrigerant to the liquefaction separation means (319).

[0171] The main cooling cycle (300) may include a plurality of main cooling expanders (351, 352). The main cooling expanders expand the main cooling refrigerant. The main cooling expanders may be expanders such as turbines operated by power. The plurality of main cooling expanders may include a third main cooling expander (351) disposed in the third main cooling line (350). The third main cooling expander (351) may be located upstream of the fifth heat exchanger (35-2) with respect to the direction in which the main cooling refrigerant flows in the third main cooling line (350). The third main cooling line (350) may pass through the fifth heat exchanger (35-2). Thus, the main cooling refrigerant expanded by the third main cooling expander (351) can be cooled in the fifth heat exchanger (35-2).

[0172] heat exchanger (30)

[0173] The heat exchange section (30) may include a first heat exchanger (31) and a second heat exchanger (32). The first heat exchanger (31) and the second heat exchanger (32) may be arranged to exchange heat between the first pre-cooling cycle (100) and the main cooling cycle (300) and the cooling line section (20). The second heat exchanger (32) may be positioned so that it passes downstream of the point where the first heat exchanger (31) passes through the cooling line section (20). The hydrogen in the cooling line section (20) that has passed through the second heat exchanger (32) may be at a lower temperature compared to the hydrogen in the cooling line section (20) that has passed through the first heat exchanger (31).

[0174] The first heat exchanger (31) may be positioned so that the first pre-cooling line (120) and the second pre-cooling line (130) extend to the fifth pre-cooling line (180). Additionally, the first heat exchanger (31) may be positioned so that the main main cooling line (310), the third main cooling line (350), and the main cooling low-pressure recovery line (373) pass through it.

[0175] The second heat exchanger (32) may be positioned so that the first pre-cooling line (120) passes through it. This may mean that the second heat exchanger (32), unlike the first heat exchanger (31), does not pass through the second pre-cooling line (130) and the fifth pre-cooling line (180).

[0176] Additionally, the second heat exchanger (32) can be positioned so that the main main cooling line (310), the third main cooling line (350), and the main cooling low-pressure recovery line (373) pass through it.

[0177] For example, a cryogenic adsorber (30”) may be placed through the second heat exchanger (32).

[0178] The heat exchanger (30) may further include a third heat exchanger (33-2), a fourth heat exchanger (34-2), a fifth heat exchanger (35-2), a sixth heat exchanger (36-2), a seventh heat exchanger (37-2), and an eighth heat exchanger (38-2). The third heat exchanger (33-2), the fourth heat exchanger (34-2), the fifth heat exchanger (35-2), the sixth heat exchanger (36-2), the seventh heat exchanger (37-2), and the eighth heat exchanger (38-2) may be arranged to exchange heat between the main cooling cycle (300) and the cooling line section (20).

[0179] The third heat exchanger (33-2), the fourth heat exchanger (34-2), the fifth heat exchanger (35-2), the sixth heat exchanger (36-2), the seventh heat exchanger (37-2), and the eighth heat exchanger (38-2) can be sequentially arranged downstream of the second heat exchanger (32) in the cooling line section (20).

[0180] The temperature of the hydrogen in the cooling line section (20) passing through each of the third heat exchanger (33-2), fourth heat exchanger (34-2), fifth heat exchanger (35-2), sixth heat exchanger (36-2), seventh heat exchanger (37-2), and eighth heat exchanger (38-2) may be lower than the temperature of the hydrogen in the cooling line section (20) passing through the heat exchanger located upstream of each heat exchanger.

[0181] The third heat exchanger (33-2) and the fourth heat exchanger (34-2) may be arranged so that the main main cooling line (310), the third main cooling line (350), and the main cooling low-pressure recovery line (373) pass through them. A fourth main cooling branch point (317) may be located in the main main cooling line (310) between the third heat exchanger (33-2) and the fourth heat exchanger (34-2).

[0182] The fifth heat exchanger (35-2) can be positioned so that the main main cooling line (310), the third main cooling line (350), and the main cooling low-pressure recovery line (373) pass through it. Additionally, the fifth heat exchanger (35-2) can be positioned so that the main cooling refrigerant passing through the third main cooling expansion valve (351) from the third main cooling line (350) passes through it.

[0183] The sixth heat exchanger (36-2) can be positioned so that the main main cooling line (310), the third main cooling line (350), and the main cooling low-pressure recovery line (373) pass through it.

[0184] The seventh heat exchanger (37-2) may be positioned so that the main main cooling line (310) and the main cooling low-pressure recovery line (373) pass through it. This may mean that the seventh heat exchanger (37-2) does not have the third main cooling line (350) pass through it, unlike the sixth heat exchanger (36-2).

[0185] The eighth heat exchanger (38-2) can be positioned so that the main main cooling line (310) and the main cooling low-pressure liquid line (371) pass through it.

[0186] Bypass line

[0187] The main cooling cycle (300) may include a second main cooling bypass line (360) that branches off from the fifth main cooling branch point (318) of the third main cooling line (350) and joins the third main cooling confluence point without exchanging heat with at least one of the plurality of heat exchangers. The fifth main cooling branch point (318) may be located downstream of the fourth main cooling branch point (317). Accordingly, some or all of the main cooling refrigerant in the third main cooling line (350) may not exchange heat with at least one of the plurality of heat exchangers through the second main cooling bypass line (360).

[0188] The above third main cooling junction point may be located downstream of the first heat exchanger (31) and upstream of the second compressor (375). At this time, a third main cooling mixer (376) may be placed at the third main cooling junction point.

[0189] The third main cooling mixer (376) can mix the main cooling refrigerant flowing in from at least one of the third main cooling line (330), the main cooling low-pressure recovery line (373), and the second main cooling bypass line (360). This third main cooling mixer (376) may be a conventional mixer. As another example, the third main cooling mixer (376) may not be a separate mixer, but may be a connecting structure between the third main cooling line (330), the main cooling low-pressure recovery line (373), and the second main cooling bypass line (360), that is, a structure that is interconnected to induce mixing of the main cooling refrigerants of each line.

[0190] Accordingly, according to the present invention, the main cooling refrigerant can partially bypass the pre-cooling section when recovered after expansion. By bypassing a portion of the pre-cooling section, the main cooling refrigerant is introduced into the compressor in a low-temperature state, thereby reducing compression energy and thus increasing energy efficiency.

[0191] In FIG. 7, the fifth main cooling branch point (318) may be located between the first heat exchanger (31) and the second heat exchanger (32). The main cooling refrigerant of the third main cooling line (350) passes through the second heat exchanger (32), but may not pass through the first heat exchanger (31) via the second main cooling bypass line (360). In this case, as a result calculated using the Aspen HYSYS simulator, the first pre-cooling energy consumption was 2.077 kWh / kg LH2 and the main cooling energy consumption was 6.361 kWh / kg LH2. Therefore, the total energy consumption was 8.438 kWh / kg LH2.

[0192] 4th embodiment

[0193] FIG. 8 is a conceptual diagram showing a high-efficiency hydrogen liquefaction system according to a fourth embodiment of the present invention. The hydrogen liquefaction system according to the fourth embodiment may include a cooling cycle section (10), a cooling line section (20), and a heat exchange section (30), and the cooling cycle section (10) may include a first pre-cooling cycle (100), a second pre-cooling cycle (200), and a main cooling cycle (300).

[0194] However, the hydrogen liquefaction system according to the fourth embodiment is the hydrogen liquefaction system according to the third embodiment with the addition of a second pre-cooling cycle (200) and a modification of the heat exchanger (30). Unless otherwise specifically stated, the descriptions in the first to third embodiments may be applied to the fourth embodiment.

[0195] 1st pre-cooling cycle (100)

[0196] The hydrogen liquefaction system according to the fourth embodiment may include a first pre-cooling cycle (100) identical to that of the hydrogen liquefaction system according to the first embodiment. Therefore, unless otherwise stated, the description of the pre-cooling cycle (100) of the first embodiment described above may be applied to the first pre-cooling cycle (100) of the fourth embodiment.

[0197] 2nd pre-cooling cycle (200)

[0198] The hydrogen liquefaction system according to the fourth embodiment may include a second pre-cooling cycle (200) identical to that of the hydrogen liquefaction system according to the first embodiment. Therefore, unless otherwise stated, the description of the pre-cooling cycle (200) of the second embodiment described above may be applied to the second pre-cooling cycle (200) of the fourth embodiment.

[0199] Main cooling cycle (300)

[0200] The hydrogen liquefaction system according to the fourth embodiment may include the same main cooling cycle (300) as that of the hydrogen liquefaction system according to the third embodiment. Therefore, unless otherwise stated, the description of the main cooling cycle (300) of the third embodiment described above may be applied to the main cooling cycle (300) of the fourth embodiment.

[0201] heat exchanger (30)

[0202] The heat exchange section (30) may include a first heat exchanger (31) and a second heat exchanger (32). The first heat exchanger (31) and the second heat exchanger (32) may be arranged to exchange heat between the first pre-cooling cycle (100), the second pre-cooling cycle (200), the main cooling cycle (300), and the cooling line section (20). Unless otherwise noted, the description of the first heat exchanger (31) and the second heat exchanger (32) of the second embodiment described above may be applied to the first heat exchanger (31) and the second heat exchanger (32) of the fourth embodiment.

[0203] The first heat exchanger (31) may be positioned so that the first pre-cooling line (120) and the second pre-cooling line (130) pass through the fifth pre-cooling line (180). Additionally, the first heat exchanger (31) may be positioned so that the second-2 pre-cooling line (230), the second-6 pre-cooling line (280), and the second-7 pre-cooling line (290) pass through. Additionally, the first heat exchanger (31) may be positioned so that the main main cooling line (310), the third main cooling line (350), and the main cooling low-pressure recovery line (373) pass through.

[0204] The second heat exchanger (32) may be positioned so that the first pre-cooling line (120) passes through it. This may mean that the second heat exchanger (32), unlike the first heat exchanger (31), does not pass through the second pre-cooling line (130) and the fifth pre-cooling line (180).

[0205] Additionally, the second heat exchanger (32) may be positioned so that the second-2 pre-cooling line (230), the second-6 pre-cooling line (280), and the second-7 pre-cooling line (290) pass through it. Additionally, the second heat exchanger (32) may be positioned so that the main main cooling line (310), the third main cooling line (350), and the main cooling low-pressure recovery line (373) pass through it.

[0206] The heat exchanger (30) may further include a third heat exchanger (43), a fourth heat exchanger (44), a fifth heat exchanger (45), and a sixth heat exchanger (46). The third heat exchanger (43), the fourth heat exchanger (44), the fifth heat exchanger (45), and the sixth heat exchanger (46) may be arranged to exchange heat between the second pre-cooling cycle (200) and the main cooling cycle (300) and the cooling line section (20).

[0207] The fourth heat exchanger (34) may be positioned so that it passes downstream of the point where the third heat exchanger (43) passes in the cooling line section (20). The fifth heat exchanger (45) may be positioned so that it passes downstream of the point where the fourth heat exchanger (44) passes in the cooling line section (20). The sixth heat exchanger (46) may be positioned so that it passes downstream of the point where the fifth heat exchanger (45) passes in the cooling line section (20).

[0208] The hydrogen in the cooling line section (20) that has passed through the third heat exchanger (43) may be at a lower temperature than the hydrogen in the cooling line section (20) that has passed through the second heat exchanger (32). The hydrogen in the cooling line section (20) that has passed through the fourth heat exchanger (44) may be at a lower temperature than the hydrogen in the cooling line section (20) that has passed through the third heat exchanger (43). The hydrogen in the cooling line section (20) that has passed through the fifth heat exchanger (45) may be at a lower temperature than the hydrogen in the cooling line section (20) that has passed through the fourth heat exchanger (44). The hydrogen in the cooling line section (20) that has passed through the sixth heat exchanger (46) may be at a lower temperature than the hydrogen in the cooling line section (20) that has passed through the fifth heat exchanger (45).

[0209] The third heat exchanger (43) may be positioned so that the second-2 pre-cooling line (230), the second-6 pre-cooling line (280), and the second-7 pre-cooling line (290) pass through it. Additionally, the third heat exchanger (43) may be positioned so that the main main cooling line (310), the third main cooling line (350), and the main cooling low-pressure recovery line (373) pass through it.

[0210] The fourth heat exchanger (44) may be positioned so that the second-6 pre-cooling line (280) passes through it. This may mean that, unlike the third heat exchanger (43), the fourth heat exchanger (44) does not pass through the second-2 pre-cooling line (230) and the second-7 pre-cooling line (290). Additionally, the fourth heat exchanger (44) may be positioned so that the main main cooling line (310), the third main cooling line (350), and the main cooling low-pressure recovery line (373) pass through it.

[0211] The fifth heat exchanger (45) may be positioned so that the second-1 pre-cooling line (220) and the second-6 pre-cooling line (280) pass through it. Additionally, the fifth heat exchanger (45) may be positioned so that the second-6 pre-cooling line (280) passes through it. Additionally, the fifth heat exchanger (45) may be positioned so that the main main cooling line (310), the third main cooling line (350), and the main cooling low-pressure recovery line (373) pass through it.

[0212] The sixth heat exchanger (46) may be positioned so that the second-third pre-cooling line (250) passes through it. This may mean that the sixth heat exchanger (46) does not pass through the second-first pre-cooling line (220), unlike the fifth heat exchanger (45). Additionally, the sixth heat exchanger (46) may be positioned so that the main main cooling line (310), the third main cooling line (350), and the main cooling low-pressure recovery line (373) pass through it.

[0213] The heat exchanger (30) may further include a seventh heat exchanger (47), an eighth heat exchanger (48), a ninth heat exchanger (49), a tenth heat exchanger (50), and an eleventh heat exchanger (51) sequentially downstream of the point where the sixth heat exchanger (36) passes in the cooling line section (20). The seventh heat exchanger (47), the eighth heat exchanger (48), the ninth heat exchanger (49), the tenth heat exchanger (50), and the eleventh heat exchanger (51) may be arranged to exchange heat between the main cooling cycle (300) and the cooling line section (20).

[0214] The temperature of the hydrogen in the cooling line section (20) passing through each of the 7th heat exchanger (47), 8th heat exchanger (48), 9th heat exchanger (49), 10th heat exchanger (50), and 11th heat exchanger (51) may be lower than the temperature of the hydrogen in the cooling line section (20) passing through the heat exchanger located upstream of each heat exchanger.

[0215] The seventh heat exchanger (47) may be positioned so that the main main cooling line (310), the third main cooling line (350), and the main cooling low-pressure recovery line (373) pass through it. A fourth main cooling branch point (317) may be located in the main main cooling line (310) between the sixth heat exchanger (46) and the seventh heat exchanger (47).

[0216] The eighth heat exchanger (48) may be positioned so that the main main cooling line (310), the third main cooling line (350), and the main cooling low-pressure recovery line (373) pass through it. Additionally, the eighth heat exchanger (48) may be positioned so that the main cooling refrigerant passing through the third main cooling expansion valve (351) in the third main cooling line (350) passes through it.

[0217] The ninth heat exchanger (49) can be positioned so that the main main cooling line (310), the third main cooling line (350), and the main cooling low-pressure recovery line (373) pass through it.

[0218] The 10th heat exchanger (50) may be positioned so that the main main cooling line (310) and the main cooling low-pressure recovery line (373) pass through it. This may mean that the 10th heat exchanger (50), unlike the 9th heat exchanger (49), does not have the 3rd main cooling line (350) pass through it.

[0219] The 11th heat exchanger (51) can be positioned so that the main main cooling line (310) and the main cooling low-pressure liquid line (371) pass through it.

[0220] Bypass line

[0221] The main cooling cycle (300) may include a second main cooling bypass line (360) that branches off from the fifth main cooling branch point (318) of the third main cooling line (350) and joins to the third main cooling joining point without exchanging heat with at least one of the plurality of heat exchangers.

[0222] The hydrogen liquefaction system according to the fourth embodiment may include a second main cooling bypass line (360) identical to that of the hydrogen liquefaction system according to the third embodiment. Therefore, unless otherwise stated, the description of the second main cooling bypass line (360) of the third embodiment described above may be applied to the second main cooling bypass line (360) of the fourth embodiment.

[0223] In FIG. 8, the fifth main cooling branch point (318) may be located between the first heat exchanger (31) and the second heat exchanger (32). The main cooling refrigerant of the third main cooling line (350) passes through the second heat exchanger (32), but may not pass through the first heat exchanger (31) via the second main cooling bypass line (360). In this case, as a result calculated using the Aspen HYSYS simulator, the first pre-cooling energy consumption was 1.349 kWh / kg LH2, the second pre-cooling energy consumption was 1.532 kWh / kg LH2, and the main cooling energy consumption was 4.930 kWh / kg LH2. Therefore, the total energy consumption was 7.811 kWh / kg LH2.

[0224] The foregoing description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains will be able to make various modifications and variations within the scope of the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are intended to explain, not limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by these embodiments. The scope of protection of the present invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present invention.

Claims

1. A cooling cycle section comprising a first pre-cooling cycle arranged to circulate a first pre-cooling refrigerant and a main cooling cycle arranged to circulate a main cooling refrigerant; A cooling line section through which a cooling target, arranged to be cooled by the above cooling cycle section, passes; and It includes a heat exchanger comprising a plurality of heat exchangers that exchange heat between the cooling cycle section and the cooling line section, and Here, among the plurality of heat exchangers, the heat exchanger that exchanges heat with the first pre-cooling cycle is called the high-temperature heat exchanger, and Here, the above-mentioned main cooling cycle includes a main cooling line through which the main cooling refrigerant passes, and Herein, the above-mentioned main cooling cycle includes a bypass line that branches off from one point of the main cooling line and bypasses the plurality of heat exchangers so as not to exchange heat with only at least one of the high-temperature heat exchangers, and joins to another point of the main cooling line, in a high-efficiency hydrogen liquefaction system.

2. A cooling cycle section comprising a first pre-cooling cycle arranged to circulate a first pre-cooling refrigerant and a main cooling cycle arranged to circulate a main cooling refrigerant; A cooling line section through which a cooling target, arranged to be cooled by the above cooling cycle section, passes; and It includes a heat exchanger comprising a plurality of heat exchangers that exchange heat between the cooling cycle section and the cooling line section, and The above main cooling cycle is, Main main cooling line; A first main cooling line branched off from a first main cooling branch point of the above main cooling line and joined to a first main cooling confluence point, which is a point of the above main cooling line; A second main cooling line branched from a second main cooling branch point of the main main cooling line and joined to a second main cooling confluence point, which is a point of the main main cooling line or the first main cooling line; and It includes a main cooling bypass line that branches off from the third main cooling branch point of the second main cooling line and joins to the second main cooling confluence point without exchanging heat with at least one of the heat exchangers through which the first pre-cooling cycle passes among the plurality of heat exchangers, and The above-mentioned second main cooling branch point is a high-efficiency hydrogen liquefaction system located downstream of the above-mentioned first main cooling branch point.

3. In Claim 2, The above main cooling cycle is, A high-efficiency hydrogen liquefaction system further comprising: a main cooling expansion valve positioned downstream of the second main cooling branch point in the main main cooling line; and a main main cooling compressor positioned downstream of the main cooling expansion valve.

4. In Claim 3, The above main cooling cycle is, A first main cooling expansion unit disposed in the first main cooling line above; and A high-efficiency hydrogen liquefaction system further comprising a second main cooling expansion unit disposed in the second main cooling line.

5. In Claim 4, The above main cooling cycle is, A first main cooling compressor disposed in the first main cooling line and positioned downstream of the first main cooling expansion unit; and A high-efficiency hydrogen liquefaction system comprising a second main cooling compressor disposed in the second main cooling line and disposed downstream of the second main cooling expander.

6. In Claim 2, The above first pre-cooling cycle is, A first gas-liquid separator configured to separate the incoming first pre-cooling refrigerant from the gas-liquid; A first pre-cooling line through which the gaseous pre-cooling refrigerant discharged from the first gas-liquid separator passes; A second pre-cooling line through which the liquid pre-cooling refrigerant discharged from the first gas-liquid separator passes; A first pre-cooling line and a connecting pre-cooling line connected to the second pre-cooling line; A second device configured to separate the refrigerant flowing in from the above-mentioned connected pre-cooling line into gas and liquid. Liquid separator; A third pre-cooling line connected to the first gas-liquid separator, through which the gaseous pre-cooling refrigerant discharged from the second gas-liquid separator passes; A fourth pre-cooling line connected to the second pre-cooling line, through which the liquid pre-cooling refrigerant discharged from the second gas-liquid separator passes; and A high-efficiency hydrogen liquefaction system comprising a fifth pre-cooling line connected to the second pre-cooling line and the fourth pre-cooling line.

7. In Claim 6, The above first pre-cooling cycle is, A first pre-cooling expansion valve disposed in the first pre-cooling line; A first pre-cooling compressor disposed in the first pre-cooling line and positioned downstream of the first pre-cooling expansion valve; A second pre-cooling expansion valve disposed in the above-mentioned fifth pre-cooling line; and A high-efficiency hydrogen liquefaction system further comprising a second pre-cooling compressor disposed in the fifth pre-cooling line and downstream of the second pre-cooling expansion valve.

8. In Claim 6, The above first pre-cooling cycle is, A third pre-cooling compressor disposed in the above third pre-cooling line; and A high-efficiency hydrogen liquefaction system further comprising a pre-cooling pump disposed in the fourth pre-cooling line and configured to pump the pre-cooling refrigerant within the fourth pre-cooling line toward the second pre-cooling line.

9. In Claim 2 It further includes a second pre-cooling cycle configured to circulate a second pre-cooling refrigerant that performs cooling at a lower temperature compared to the first pre-cooling refrigerant, and The above second pre-cooling cycle is, 2-1 gas-liquid separator configured to separate the incoming 2nd pre-cooling refrigerant from the gas-liquid; A second-1 pre-cooling line through which the second pre-cooling refrigerant in the gas phase discharged from the second-1 gas-liquid separator above passes; A 2-2 pre-cooling line through which the liquid 2nd pre-cooling refrigerant discharged from the 2-1 gas-liquid separator above passes; A 2-2 gas-liquid separator connected to the 2-1 pre-cooling line and configured to separate the gas and liquid of the 2-2 pre-cooling refrigerant flowing in from the 2-1 pre-cooling line; A 2-3 pre-cooling line through which the gaseous 2nd pre-cooling refrigerant discharged from the above 2-2 gas-liquid separator passes; A 2-4 pre-cooling line through which the liquid 2nd pre-cooling refrigerant discharged from the above 2-2 gas-liquid separator passes; A 2-6 pre-cooling line connected to the above 2-3 pre-cooling line and the above 2-4 pre-cooling line; and A hydrogen liquefaction system comprising a 2-7 pre-cooling line connected to at least one of the 2-2 pre-cooling line or the 2-6 pre-cooling line, and connected to the 2-1 gas-liquid separator to allow the 2 pre-cooling refrigerant to flow into the 2-1 gas-liquid separator.

10. In Claim 9, The above second pre-cooling cycle is, A 2-1 pre-cooling expander disposed in the above 2-1 pre-cooling line; and A hydrogen liquefaction system further comprising a 2-2 pre-cooling expander disposed in the above 2-3 pre-cooling line.

11. In Claim 9, The above second pre-cooling cycle is, 2-1 pre-cooling expansion valve disposed in the above 2-2 pre-cooling line; and A hydrogen liquefaction system further comprising a 2-1 pre-cooling compressor disposed in the 2-2 pre-cooling line and disposed downstream of the 2-1 pre-cooling expansion valve.

12. In Claim 9, The above second pre-cooling cycle is, 2-2 pre-cooling expansion valve disposed in the above 2-4 pre-cooling line; and A hydrogen liquefaction system further comprising a 2-3 pre-cooling compressor disposed in the above 2-6 pre-cooling line.

13. In Claim 6, The above heat exchanger is, A first heat exchanger configured to exchange heat between the first pre-cooling cycle and the main cooling cycle with the cooling line section; and The above first pre-cooling cycle and the above main cooling cycle are arranged to exchange heat with the cooling line section, and include a second heat exchanger through which the downstream of the point where the first heat exchanger passes in the cooling line section passes. The first heat exchanger is arranged so that the first pre-cooling line, the fifth pre-cooling line, the main main cooling line, the first main cooling line, and the second main cooling line pass through it, and The above second heat exchanger is a hydrogen liquefaction system in which the above first pre-cooling line, main main cooling line, first main cooling line, and second main cooling line pass through.

14. In Claim 9, The above first pre-cooling cycle is, A first gas-liquid separator configured to separate the incoming first pre-cooling refrigerant from the gas-liquid; A first pre-cooling line through which the gaseous pre-cooling refrigerant discharged from the first gas-liquid separator passes; A second pre-cooling line through which the liquid pre-cooling refrigerant discharged from the first gas-liquid separator passes; A first pre-cooling line and a connecting pre-cooling line connected to the second pre-cooling line; A second device configured to separate the refrigerant flowing in from the above-mentioned connected pre-cooling line into gas and liquid. Liquid separator; A third pre-cooling line connected to the first gas-liquid separator, through which the gaseous pre-cooling refrigerant discharged from the second gas-liquid separator passes; A fourth pre-cooling line connected to the second pre-cooling line, through which the liquid pre-cooling refrigerant discharged from the second gas-liquid separator passes; and It includes a fifth pre-cooling line to which the second pre-cooling line and the fourth pre-cooling line are connected, and The above heat exchanger is, A first heat exchanger configured to exchange heat between the first pre-cooling cycle, the second pre-cooling cycle, and the main cooling cycle with the cooling line section; and The above first pre-cooling cycle, the above second pre-cooling cycle, and the above main cooling cycle are arranged to exchange heat with the cooling line section, and include a second heat exchanger through which the downstream of the point where the first heat exchanger passes in the cooling line section passes. The above-mentioned first heat exchanger is arranged so that the above-mentioned first pre-cooling line, fifth pre-cooling line, second-seven pre-cooling line, second-seven pre-cooling line, second-six pre-cooling line, main main cooling line, first main cooling line, and second main cooling line pass through it, and The above second heat exchanger is a hydrogen liquefaction system in which the above first pre-cooling line, second-7 pre-cooling line, second-2 pre-cooling line, second-6 pre-cooling line, main main cooling line, first main cooling line, and second main cooling line pass through.

15. In Claim 9, The above heat exchanger is, A third heat exchanger configured to exchange heat between the second pre-cooling cycle and the main cooling cycle and the cooling line section; A fourth heat exchanger configured to exchange heat with the second pre-cooling cycle and the main cooling cycle and the cooling line section, wherein the downstream of the point where the third heat exchanger passes in the cooling line section passes; A fifth heat exchanger configured to exchange heat between the second pre-cooling cycle and the main cooling cycle and the cooling line section, wherein the downstream of the point where the fourth heat exchanger passes in the cooling line section passes; and A hydrogen liquefaction system configured to heat exchange the above-mentioned second pre-cooling cycle and the above-mentioned main cooling cycle with the above-mentioned cooling line section, and including a sixth heat exchanger through which the downstream of the point where the above-mentioned fifth heat exchanger passes in the above-mentioned cooling line section.

16. In Claim 15, The third heat exchanger, the fourth heat exchanger, and the fifth heat exchanger are arranged so that the second-6 pre-cooling line passes through them, and the sixth heat exchanger is arranged so that the second-3 pre-cooling line passes through it. The above third heat exchanger is arranged so that the above 2-2 pre-cooling line and the above 2-7 pre-cooling line pass through it, and The above-mentioned fifth heat exchanger is a hydrogen liquefaction system in which the above-mentioned second-1 pre-cooling line passes.

17. In claim 2 or 9, The above heat exchanger is, A seventh heat exchanger configured to exchange heat between the above main cooling cycle and the above cooling line section; An 8th heat exchanger is provided to exchange heat between the above main cooling cycle and the above cooling line section, wherein the downstream of the point where the 7th heat exchanger passes in the above cooling line section passes; A ninth heat exchanger arranged to exchange heat between the above main cooling cycle and the above cooling line section, wherein the downstream of the point where the eighth heat exchanger passes in the above cooling line section passes; and A high-efficiency hydrogen liquefaction system configured to heat exchange the above-mentioned main cooling cycle and the above-mentioned cooling line section, comprising a 10th heat exchanger passing downstream of the point where the 9th heat exchanger passes in the above-mentioned cooling line section.

18. In Claim 17, The above-mentioned seventh heat exchanger and the above-mentioned eighth heat exchanger are arranged so that a portion of the above-mentioned main cooling line passes between the above-mentioned first main cooling branch point and the above-mentioned second main cooling branch point, and The above seventh heat exchanger is arranged so that the main main cooling line, the first main cooling line, and the second main cooling line pass through it, The above-mentioned eighth heat exchanger is a high-efficiency hydrogen liquefaction system arranged so that the above-mentioned main cooling line and the above-mentioned second cooling line pass through it.

19. In Claim 17, The ninth heat exchanger and the tenth heat exchanger are arranged so that a portion of the main cooling line passes between the second cooling branch point and the cooling expansion valve. The above ninth heat exchanger is arranged so that the above main cooling line and the above second cooling line pass through it, and The above 10th heat exchanger is a high-efficiency hydrogen liquefaction system arranged so that the above main cooling line passes through it.

20. In claim 13 or 14, A high-efficiency hydrogen liquefaction system in which the above-mentioned third main cooling branch point is located between the first heat exchanger and the second heat exchanger, and the above-mentioned main cooling bypass line does not pass through the first heat exchanger.

21. A cooling cycle section comprising a first pre-cooling cycle arranged to circulate a first pre-cooling refrigerant and a main cooling cycle arranged to circulate a main cooling refrigerant; A cooling line section through which a cooling target, arranged to be cooled by the above cooling cycle section, passes; and It includes a heat exchanger comprising a plurality of heat exchangers that exchange heat between the cooling cycle section and the cooling line section, and The above main cooling cycle is, Main main cooling line; A third main cooling line that branches off from the fourth main cooling branch point of the above main main cooling line and joins to the third main cooling confluence point, which is a point of the above main main cooling line; A third main cooling expander and a fourth main cooling expander arranged in series on the above third main cooling line; It includes a second main cooling bypass line that branches off from the fifth main cooling branch point of the third main cooling line and joins to the third main cooling joining point without exchanging heat with at least one of the plurality of heat exchangers, The above-mentioned fifth main cooling branch point is a high-efficiency hydrogen liquefaction system located downstream of the above-mentioned fourth main cooling branch point.

22. In Claim 21, The above heat exchanger is, A first heat exchanger configured to exchange heat between the first pre-cooling cycle and the main cooling cycle and the cooling line section; and The cooling line section is arranged to exchange heat with the first pre-cooling cycle and the main cooling cycle, and includes a second heat exchanger passing downstream of the point where the first heat exchanger passes in the cooling line section. A high-efficiency hydrogen liquefaction system in which the above-mentioned fifth main cooling branch point is located between the first heat exchanger and the second heat exchanger, and the above-mentioned second main cooling bypass line does not pass through the first heat exchanger.

23. In Claim 21, It further includes a second pre-cooling cycle configured to circulate a second pre-cooling refrigerant that performs cooling at a lower temperature compared to the first pre-cooling refrigerant, and The first heat exchanger and the second heat exchanger are each arranged to further heat exchange the second pre-cooling cycle with the cooling line section, and The above second pre-cooling cycle is, 2-1 gas-liquid separator configured to separate the incoming 2nd pre-cooling refrigerant from the gas-liquid; A second-1 pre-cooling line through which the second pre-cooling refrigerant in the gas phase discharged from the second-1 gas-liquid separator above passes; A 2-2 pre-cooling line through which the liquid 2nd pre-cooling refrigerant discharged from the 2-1 gas-liquid separator above passes; A 2-2 gas-liquid separator connected to the 2-1 pre-cooling line and configured to separate the gas and liquid of the 2-2 pre-cooling refrigerant flowing in from the 2-1 pre-cooling line; A 2-3 pre-cooling line through which the gaseous 2nd pre-cooling refrigerant discharged from the above 2-2 gas-liquid separator passes; A 2-4 pre-cooling line through which the liquid 2nd pre-cooling refrigerant discharged from the above 2-2 gas-liquid separator passes; A 2-6 pre-cooling line connected to the above 2-3 pre-cooling line and the above 2-4 pre-cooling line; and A hydrogen liquefaction system comprising a 2-7 pre-cooling line connected to at least one of the 2-2 pre-cooling line or the 2-6 pre-cooling line, and connected to the 2-1 gas-liquid separator to allow the 2 pre-cooling refrigerant to flow into the 2-1 gas-liquid separator.

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