System and method for carrying out hydrogen liquefaction by utilizing LNG (Liquefied Natural Gas) cold energy

Abstract

The invention relates to the technical field of hydrogen liquefaction, in particular to a system and method for hydrogen liquefaction through LNG cold energy. The system for carrying out hydrogen liquefaction by utilizing the LNG cold energy comprises a nitrogen refrigeration cycle, a cryogenic refrigerant refrigeration cycle, a first heat exchanger, a hydrogen compressor, a second heat exchanger, a third heat exchanger, an ortho-parahydrogen conversion reactor, a fourth heat exchanger and a hydrogen throttle valve, hydrogen sequentially passes through the first heat exchanger, the hydrogen compressor, the second heat exchanger, the third heat exchanger, the ortho-parahydrogen conversion reactor, the fourth heat exchanger and the hydrogen throttling valve and is liquefied into liquid hydrogen from a gaseous state, and the nitrogen refrigeration cycle is used for exchanging heat for the cryogenic refrigerant refrigeration cycle, the second heat exchanger, the third heat exchanger and the ortho-parahydrogen conversion reactor. And the cryogenic refrigerant refrigeration cycle is used for cryogenic liquefaction of hydrogen. According to the system for hydrogen liquefaction through the LNG cold energy, hydrogen liquefaction is achieved by using the LNG cold energy as a cold source, comprehensive utilization of energy is achieved, power consumption is reduced, and energy conservation and environmental protection are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen liquefaction, and in particular to a system and method for hydrogen liquefaction using LNG cold energy. Background Art

[0002] In the process of utilizing hydrogen energy, storage and transportation are key technologies. Compared with gaseous hydrogen storage and transportation, liquid hydrogen storage and transportation has the advantages of low cost, high hydrogen density, high purity, suitability for long-distance transportation and bulk international trade, and convenience for refueling in later applications. It is recognized by the industry as an important link in the large-scale use of hydrogen energy. In order to obtain liquid hydrogen, hydrogen liquefaction is the basic technology that supports the large-scale collection, storage, transportation, and application of hydrogen.

[0003] The production of liquid hydrogen requires a lot of cold energy, and the energy consumption of the hydrogen liquefaction process of the pure electric refrigeration cycle is very high, which has caused certain restrictions on its promotion. At the same time, there are many existing LNG receiving stations in China, but there is a problem that a large amount of LNG cold energy is wasted. Therefore, it is considered to combine the two to achieve comprehensive and optimal utilization of energy. Unlike electric refrigeration liquefied hydrogen, the LNG gasification of the LNG receiving station itself can provide a large amount of cold energy. Therefore, for the hydrogen liquefaction process, LNG cold energy can be used as much as possible to reduce power consumption, thereby achieving the energy-saving purpose of reducing liquefaction energy consumption. Since many LNG receiving stations and wind, solar, tidal and other renewable energy power generation / electrolysis hydrogen production are arranged at the seaside, there is a large possibility of synchronization between the two, and the planning can be comprehensively considered. Based on this, the present invention application is proposed. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a system and method for hydrogen liquefaction using LNG cold energy. The system for hydrogen liquefaction using LNG cold energy uses LNG cold energy as a cold source to achieve hydrogen liquefaction, thereby realizing comprehensive utilization of energy, reducing power consumption, and saving energy and protecting the environment.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A system for liquefying hydrogen using LNG cold energy comprises a nitrogen refrigeration cycle, a cryogenic refrigerant refrigeration cycle, a first heat exchanger, a hydrogen compressor, a second heat exchanger, a third heat exchanger, a normal-parahydrogen conversion reactor, a fourth heat exchanger and a hydrogen throttle valve. Hydrogen is sequentially liquefied from a gaseous state to liquid hydrogen through the first heat exchanger, the hydrogen compressor, the second heat exchanger, the third heat exchanger, the normal-parahydrogen conversion reactor, the fourth heat exchanger and the hydrogen throttle valve. The nitrogen refrigeration cycle is used for heat exchange for the cryogenic refrigerant refrigeration cycle, the second heat exchanger, the third heat exchanger and the normal-parahydrogen conversion reactor. The cryogenic refrigerant refrigeration cycle is used for deep-cold liquefaction of hydrogen.

[0007] Further, the nitrogen refrigeration cycle includes a nitrogen compressor, a fifth heat exchanger, a nitrogen expander and a nitrogen throttle valve. The nitrogen is compressed by the nitrogen compressor, and the compressed nitrogen is cooled by the fifth heat exchanger. The cooled nitrogen is expanded and throttled by the nitrogen expander and the nitrogen throttle valve and then cooled again. The nitrogen after cooling again is used as a cold source to heat and reheat the normal-parahydrogen conversion reactor and the third heat exchanger respectively. The nitrogen after heat exchange and reheating is used as a cold source again to heat and reheat the second heat exchanger to meet the minimum inlet temperature requirement of the nitrogen compressor. The nitrogen after heat exchange and reheating is compressed in the nitrogen compressor again, and the cycle is repeated in sequence.

[0008] Furthermore, the cryogenic refrigerant refrigeration cycle includes a cryogenic refrigerant compressor, a sixth heat exchanger, and a cryogenic refrigerant expander. The cryogenic refrigerant is compressed and pressurized by the cryogenic refrigerant compressor, and the compressed cryogenic refrigerant enters the sixth heat exchanger for heat exchange and cooling. The cryogenic refrigerant after heat exchange passes through the third heat exchanger for heat exchange and cooling again, and then enters the fourth heat exchanger for the first time for further heat exchange and cooling, and then enters the cryogenic refrigerant expander for expansion and cooling, and then enters the fourth heat exchanger again as a cold source for heat exchange, and the reheated cryogenic refrigerant passes through the second heat exchanger for reheating again to meet the minimum inlet temperature requirement of the cryogenic refrigerant compressor, and then the cryogenic refrigerant enters the cryogenic refrigerant compressor for compression, and the cycle is repeated in sequence.

[0009] Furthermore, the cold source of the first heat exchanger is LNG cold energy, and the first heat exchanger is used for heat exchange and cooling of hydrogen.

[0010] Furthermore, the cold source of the second heat exchanger is LNG cold energy, cold energy of nitrogen reheating before entering the nitrogen compressor in the nitrogen refrigeration cycle, and cold energy of cryogenic refrigerant reheating before entering the cryogenic refrigerant compressor in the cryogenic refrigerant refrigeration cycle. The second heat exchanger is used for heat exchange and cooling of hydrogen, the second heat exchanger is used for nitrogen reheating so that it reaches the minimum inlet temperature requirement of the nitrogen compressor, and the second heat exchanger is also used for cryogenic refrigerant reheating so that it reaches the minimum inlet temperature requirement of the cryogenic refrigerant compressor.

[0011] Furthermore, the cold source of the third heat exchanger is the cold energy generated by nitrogen expansion / throttling refrigeration in the nitrogen refrigeration cycle. The third heat exchanger is used for heat exchange and cooling of hydrogen. The third heat exchanger is also used for heat exchange and cooling of the cryogenic refrigerant before it enters the fourth heat exchanger for the first time.

[0012] Furthermore, the cold source of the fourth heat exchanger is the cold energy generated by the expansion and refrigeration of the cryogenic refrigerant in the cryogenic refrigerant refrigeration cycle, and the fourth heat exchanger is used to cryogenically cool the hydrogen to liquefy it.

[0013] Furthermore, the cold sources of the fifth heat exchanger and the sixth heat exchanger are both LNG cold energy.

[0014] Furthermore, the deep cryogen includes helium cryogen or hydrogen cryogen or helium-hydrogen mixed cryogen.

[0015] On the other hand, the present invention also provides a method for liquefying hydrogen using LNG cold energy, which comprises the following steps:

[0016] S1: preparing hydrogen by electrolysis of water as the input source of raw hydrogen;

[0017] S2: LNG cold energy, nitrogen refrigeration cycle, and cryogenic refrigerant refrigeration cycle are set to provide cooling and liquefaction support for hydrogen. LNG cold energy, nitrogen refrigeration cycle, and cryogenic refrigerant refrigeration cycle are used crosswise to achieve the purpose of fully utilizing energy and using LNG cold energy as much as possible for cooling;

[0018] S3: The cryogenic hydrogen continues to be throttled and cooled to a temperature below the liquefaction temperature corresponding to the storage pressure of the liquid hydrogen storage tank;

[0019] S4: Set up a liquid hydrogen storage tank, and the hydrogen enters the tank for storage after liquefaction.

[0020] Beneficial effects of the invention: The invention discloses a system for liquefying hydrogen using cold energy of LNG, comprising a nitrogen refrigeration cycle, a cryogenic refrigerant refrigeration cycle, a first heat exchanger, a hydrogen compressor, a second heat exchanger, a third heat exchanger, a normal-parahydrogen conversion reactor, a fourth heat exchanger and a hydrogen throttle valve, wherein hydrogen is sequentially liquefied from a gaseous state to liquid hydrogen through the first heat exchanger, the hydrogen compressor, the second heat exchanger, the third heat exchanger, the normal-parahydrogen conversion reactor, the fourth heat exchanger and the hydrogen throttle valve, wherein the nitrogen refrigeration cycle is used for heat exchange for the cryogenic refrigerant refrigeration cycle, the second heat exchanger, the third heat exchanger and the normal-parahydrogen conversion reactor, and the cryogenic refrigerant refrigeration cycle is used for deep-cold liquefaction of hydrogen. Hydrogen is obtained by electrolysis of water. The temperature of the raw hydrogen is relatively high. The raw hydrogen is cooled by the first heat exchanger. The hydrogen compressor can be a conventional compressor or a low-temperature compressor. When the hydrogen compressor is a conventional compressor, a multi-stage intercooler and an aftercooler need to be installed. The multi-stage intercooler and the aftercooler can use the cold wastewater from LNG gasification as the cooling medium. However, since conventional compressors and their ancillary equipment are relatively complicated and energy-intensive, it is more appropriate to use a low-temperature compressor. The temperature of the hydrogen is first cooled to -150℃~-160℃ by the first heat exchanger, and then pressurized by the hydrogen compressor. The pressurized hydrogen will heat up, and then the hydrogen is heated by the second heat exchanger. Cooling and precooling the temperature of hydrogen to -145℃~-158℃, and then cooling the hydrogen again through the third heat exchanger to cool the temperature of hydrogen to -183℃~192℃, and setting a normal-parahydrogen conversion reactor within this temperature range, installing a conversion catalyst in the normal-parahydrogen conversion reactor, when hydrogen passes through the normal-parahydrogen conversion reactor, not only heat exchange is carried out, but also normal-parahydrogen conversion occurs at the same time, keeping the temperature at -183℃~192℃, then the hydrogen is cooled again through the fourth heat exchanger, and the temperature after cooling is -245℃~-252℃, and the deep-cold hydrogen is finally throttled and cooled through the hydrogen throttle valve, and is liquefied below the liquefaction temperature and then enters the storage tank for storage. A system for hydrogen liquefaction using LNG cold energy of the present application uses LNG cold energy as a cold source to realize hydrogen liquefaction, realize comprehensive utilization of energy, reduce power consumption, and save energy and protect the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the present invention;

[0022] Figure 2 It is a structural schematic diagram of the nitrogen refrigeration cycle of the present invention;

[0023] Figure 3 It is a schematic diagram of the structure of the cryogenic refrigerant refrigeration cycle of the present invention.

[0024] Explanation of the reference numerals: 1-first heat exchanger, 2-hydrogen compressor, 3-second heat exchanger, 4-third heat exchanger, 5-normal-para-hydrogen conversion reactor, 6-fourth heat exchanger, 7-hydrogen throttle valve, 8-nitrogen compressor, 9-fifth heat exchanger, 10-nitrogen expander, 11-nitrogen throttle valve, 12-cryogenic refrigerant compressor, 13-sixth heat exchanger, 14-cryogenic refrigerant expander. DETAILED DESCRIPTION

[0025] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0026] It should be understood that the terms used herein are only for the purpose of describing specific example embodiments and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "include", "comprise", "contain", and "have" are inclusive and therefore specify the existence of stated features, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, steps, operations, elements, parts and / or combinations thereof. The method steps, processes, and operations described herein are not interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0027] Although the terms first, second, third, etc. can be used in the text to describe multiple elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in the text. Therefore, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section without departing from the teaching of the example embodiments.

[0028] For ease of description, spatial relative terms may be used in the text to describe the relationship of one element or feature relative to another element or feature as shown in the figure, such as "inside", "outside", "inner side", "outer side", "below", "below", "above", "above", etc. Such spatial relative terms include different orientations of the device in use or operation in addition to the orientation depicted in the figure. For example, if the device in the figure is turned over, the element described as "below other elements or features" or "below other elements or features" will then be oriented as "above other elements or features" or "above other elements or features". Therefore, the example term "below..." can include both upper and lower orientations. The device can be oriented otherwise (rotated 90 degrees or in other directions) and the spatial relative descriptors used in the text are interpreted accordingly.

[0029] Embodiment 1:

[0030] like Figure 1-3As shown, the present embodiment provides a system for liquefying hydrogen using LNG cold energy, which includes a nitrogen refrigeration cycle, a cryogenic refrigerant refrigeration cycle, a first heat exchanger 1, a hydrogen compressor 2, a second heat exchanger 3, a third heat exchanger 4, a normal-parahydrogen conversion reactor 5, a fourth heat exchanger 6 and a hydrogen throttle valve 7. Hydrogen is liquefied from a gaseous state to liquid hydrogen through the first heat exchanger 1, the hydrogen compressor 2, the second heat exchanger 3, the third heat exchanger 4, the normal-parahydrogen conversion reactor 5, the fourth heat exchanger 6 and the hydrogen throttle valve 7 in sequence. The nitrogen refrigeration cycle is used for heat exchange for the cryogenic refrigerant refrigeration cycle, the second heat exchanger 3, the third heat exchanger 4 and the normal-parahydrogen conversion reactor 5, and the cryogenic refrigerant refrigeration cycle is used for deep-cold liquefaction of hydrogen. In actual use, hydrogen is obtained by electrolyzing water. The temperature of the raw hydrogen is relatively high. The raw hydrogen is cooled by the first heat exchanger 1. The hydrogen compressor 2 can use a conventional compressor or a low-temperature compressor. When the hydrogen compressor 2 is a conventional compressor, a multi-stage intercooler and an aftercooler need to be installed. The multi-stage intercooler and the aftercooler can use the cold wastewater from LNG gasification as the cooling medium. However, since the conventional compressor and its ancillary equipment are relatively complicated and have high energy consumption, it is more appropriate to use a low-temperature compressor. The temperature of the hydrogen is first cooled to -150℃~-160℃ by the first heat exchanger, and then pressurized by the hydrogen compressor 2. The pressurized hydrogen will heat up, and then the hydrogen will be heated by the second heat exchanger 3. The hydrogen is cooled down to -145°C to -158°C, and then cooled down again by the third heat exchanger 4 to -183°C to 192°C. A normal-parahydrogen conversion reactor 5 is arranged within the temperature range, and a conversion catalyst is installed in the normal-parahydrogen conversion reactor 5. When the hydrogen passes through the normal-parahydrogen conversion reactor 5, heat exchange is performed and normal-parahydrogen conversion occurs at the same time, maintaining the temperature at -183°C to 192°C. After that, the hydrogen is cooled down again by the fourth heat exchanger 6, and the temperature after cooling is -245°C to -252°C. The cryogenic hydrogen is finally throttled down by the hydrogen throttle valve 7 to be liquefied below the liquefaction temperature and then stored in the storage tank.

[0031] In this embodiment, the nitrogen refrigeration cycle includes a nitrogen compressor 8, a fifth heat exchanger 9, a nitrogen expander 10 and a nitrogen throttle valve 11. The nitrogen is compressed by the nitrogen compressor 8, and the compressed nitrogen is cooled by the fifth heat exchanger 9. The cooled nitrogen is expanded and throttled by the nitrogen expander 10 and the nitrogen throttle valve 11 and then cooled again. The nitrogen after cooling again is used as a cold source to heat and reheat the normal-parahydrogen conversion reactor 5 and the third heat exchanger 4 respectively. The nitrogen after heat exchange and reheating is used as a cold source again to heat and reheat the second heat exchanger 3 to meet the minimum inlet temperature requirement of the nitrogen compressor 8. The nitrogen after heat exchange and reheating is compressed in the nitrogen compressor 8 again, and the cycle is repeated in sequence. In actual use, the nitrogen refrigeration cycle is a closed cycle. The nitrogen reheated to -150℃~-160℃ by the second heat exchanger 3 is compressed to 4~7MPa by the nitrogen compressor 8. The nitrogen compressor 8 adopts a low-temperature nitrogen compressor 8. The compressed nitrogen will heat up and exchange heat with LNG through the fifth heat exchanger 9. After being cooled to -150℃~-160℃ by LNG, the nitrogen is expanded and throttled by the nitrogen expander 10 and the nitrogen throttle valve 11 respectively, and the temperature is reduced to -180℃~-20 0℃, and then as a cold source to provide cold energy support to the third heat exchanger 4 and the normal-parahydrogen conversion reactor 5 respectively, so that the temperature of the hydrogen is maintained at -180℃~-200℃, and then the nitrogen is used as a cold source again to heat and reheat the second heat exchanger 3. The temperature of the nitrogen after reheating is -150℃~-160℃, so that it can enter the nitrogen compressor 8 of the nitrogen refrigeration cycle. The nitrogen expander 10 and the nitrogen throttle valve 11 can be used at will or both of them can realize the function of cooling and refrigerating the nitrogen.

[0032] In this embodiment, the cryogenic refrigerant refrigeration cycle includes a cryogenic refrigerant compressor 12, a sixth heat exchanger 13, and a cryogenic refrigerant expander 14. The cryogenic refrigerant is compressed and pressurized by the cryogenic refrigerant compressor 12, and the compressed cryogenic refrigerant enters the sixth heat exchanger 13 for heat exchange and cooling. The cryogenic refrigerant after heat exchange passes through the third heat exchanger 4 for heat exchange and cooling again, and then enters the fourth heat exchanger 6 for further heat exchange and cooling for the first time, and then enters the cryogenic refrigerant expander 14 for expansion and cooling, and then enters the fourth heat exchanger 6 again as a cold source for heat exchange, and the reheated cryogenic refrigerant passes through the second heat exchanger 3 for reheating again to meet the minimum inlet temperature requirement of the cryogenic refrigerant compressor 12, and then the cryogenic refrigerant enters the cryogenic refrigerant compressor 12 for compression, and circulates in sequence. In actual use, the cryogenic refrigerant refrigeration cycle is a closed cycle. The cryogenic refrigerant is reheated to -150°C to -160°C through the second heat exchanger 3. The cryogenic refrigerant compressor 12 also uses a low-temperature compressor. After the cryogenic refrigerant is compressed to 3 to 5 MPa by the cryogenic refrigerant compressor 12, the cryogenic refrigerant is heated. The heated cryogenic refrigerant exchanges heat with LNG through the sixth heat exchanger 13 and is cooled to -150°C to -160°C by LNG. Then, the cryogenic refrigerant is reheated to -150°C to -160°C through the third heat exchanger 4. After being cooled to -180℃~-200℃ for the first time, it enters the fourth heat exchanger 6 to be further cooled to -220℃~-240℃, and then enters the cryogenic refrigerant expander 14 to expand, and the temperature is reduced to -254℃~-256℃, and then enters the fourth heat exchanger 6 again as a cold source to cool the hydrogen, so that the hydrogen temperature is reduced to the target temperature, and then the cryogenic refrigerant is reheated to -150℃~-160℃ through the second heat exchanger 3 so that it can enter the cryogenic refrigerant compressor 12.

[0033] In this embodiment, the cold source of the first heat exchanger 1 is LNG cold energy, and the first heat exchanger 1 is used to heat and cool the hydrogen. In actual use, the raw hydrogen produced by electrolysis has a temperature of 70°C to 130°C under normal pressure, and is heat exchanged and cooled by the first heat exchanger 1 to enter the subsequent process.

[0034] In this embodiment, the cold source of the second heat exchanger 3 is LNG cold energy, cold energy before nitrogen reheating in the nitrogen refrigeration cycle enters the nitrogen compressor 8, and cold energy before deep cryogenic refrigerant reheating in the deep cryogenic refrigerant refrigeration cycle enters the deep cryogenic refrigerant compressor 12. The second heat exchanger 3 is used to heat and cool the hydrogen. The second heat exchanger 3 is used to reheat the nitrogen to make it reach the minimum inlet temperature requirement of the nitrogen compressor 8. The second heat exchanger 3 is also used to reheat the deep cryogenic refrigerant to make it reach the minimum inlet temperature requirement of the deep cryogenic refrigerant compressor 12. In actual use, the second heat exchanger 3 uses LNG cold energy, cold energy before nitrogen reheating in the nitrogen refrigeration cycle enters the nitrogen compressor 8, and cold energy before deep cryogenic refrigerant reheating in the deep cryogenic refrigerant refrigeration cycle enters the deep cryogenic refrigerant compressor 12 to precool the hydrogen to -145°C to -158°C, and at the same time reheat the nitrogen and deep cryogenic refrigerant to -150°C to -160°C, so that they can both enter the corresponding low-temperature compressor for compression and pressurization.

[0035] In this embodiment, the cold source of the third heat exchanger 4 is the cold energy generated by nitrogen expansion / throttling refrigeration in the nitrogen refrigeration cycle. The third heat exchanger 4 is used to heat and cool the hydrogen. The third heat exchanger 4 is also used to heat and cool the cryogenic refrigerant before it enters the fourth heat exchanger 6 for the first time. In actual use, the third heat exchanger 4 uses the cold energy of nitrogen before it reheats and enters the second heat exchanger 3 to cool the hydrogen to -183°C to 192°C, and a normal-parahydrogen catalytic converter is set within this temperature range. The nitrogen refrigeration cycle is still used for heat removal, and the refrigeration cycle also precools the cryogenic refrigerant.

[0036] In this embodiment, the cold source of the fourth heat exchanger 6 is the cold energy generated by the cryogenic expansion refrigeration in the cryogenic refrigerant refrigeration cycle, and the fourth heat exchanger 6 is used to cryogenically cool the hydrogen to liquefy it. In actual use, the fourth heat exchanger 6 uses the cold energy of the cryogenic refrigerant before it reheats and enters the second heat exchanger 3 to cool the hydrogen to -245°C to -252°C.

[0037] In this embodiment, the cold sources of the fifth heat exchanger 9 and the sixth heat exchanger 13 are both LNG cold energy. In actual use, the cold source of the fifth heat exchanger 9 is LNG cold energy, and the fifth heat exchanger 9 is used to heat exchange and cool the nitrogen after being pressurized and heated by the nitrogen compressor 8, and is cooled to -150℃~-160℃ by LNG. The cold source of the sixth heat exchanger 13 is also LNG cold energy, and the sixth heat exchanger 13 is used to heat exchange and cool the cryogenic refrigerant after being pressurized and heated by the cryogenic refrigerant compressor 12, and is cooled to -150℃~-160℃ by LNG.

[0038] In this embodiment, the cryogenic cryogen includes helium cryogen or hydrogen cryogen or helium-hydrogen mixed cryogen. In actual use, the cryogenic cryogen includes helium cryogen or hydrogen cryogen or helium-hydrogen mixed cryogen, and can also be any combination of two or more of hydrogen, helium, neon and nitrogen.

[0039] In this embodiment, the hydrogen compressor 2, the nitrogen compressor 8 and the cryogenic refrigerant compressor 12 all use low-temperature compressors. In actual use, the temperature of the hydrogen compressor 2, the nitrogen compressor 8 and the cryogenic refrigerant compressor 12 before entering the compressor inlet is relatively low. The use of low-temperature compressors can directly compress the low-temperature hydrogen, nitrogen and cryogenic refrigerants. If a conventional compressor is used, a set of rewarming devices is also required to restore the temperature of the hydrogen, nitrogen and cryogenic refrigerants to room temperature before use. The compressed gas is a high-temperature gas, and external cooling is required to cool it down, so more energy is consumed; on the other hand, because the medium has low kinetic energy at low temperature, small diffusion, small volume, and is easy to absorb energy, that is, easy to be compressed, so the energy consumption of the normal temperature compressor will be significantly higher than that of the low temperature compressor due to the above two reasons.

[0040] Embodiment 2:

[0041] like Figure 1-3 As shown, based on the first embodiment, the present invention provides a method for liquefying hydrogen using LNG cold energy, comprising the following steps:

[0042] S1: preparing hydrogen by electrolysis of water as the input source of raw hydrogen;

[0043] S2: LNG cold energy, nitrogen refrigeration cycle, and cryogenic refrigerant refrigeration cycle are set to provide cooling and liquefaction support for hydrogen. LNG cold energy, nitrogen refrigeration cycle, and cryogenic refrigerant refrigeration cycle are used crosswise to achieve the purpose of fully utilizing energy and using LNG cold energy as much as possible for cooling;

[0044] S3: The cryogenic hydrogen continues to be throttled and cooled to a temperature below the liquefaction temperature corresponding to the storage pressure of the liquid hydrogen storage tank;

[0045] S4: Set up a liquid hydrogen storage tank, and the hydrogen enters the tank for storage after liquefaction.

[0046] In actual use, water is electrolyzed as hydrogen raw material input, and then LNG cold energy, nitrogen refrigeration cycle, and cryogenic refrigerant refrigeration cycle are used to provide cooling and liquefaction support for the hydrogen. LNG cold energy, nitrogen refrigeration cycle, and cryogenic refrigerant refrigeration cycle are used interchangeably to achieve the purpose of fully utilizing energy and using LNG cold energy as much as possible for cooling, so as to liquefy the hydrogen, and finally throttle the temperature to below the liquefaction temperature corresponding to the hydraulic tank pressure, and finally the liquefied hydrogen is loaded into the tank for storage.

[0047] All technical features in this embodiment can be freely combined according to actual needs. The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be covered by the scope of the claims of the present invention. The technology, shape, and structural parts not described in detail in the present invention are all well-known technologies.

[0048] The above embodiments are preferred implementation schemes of the present invention. In addition, other implementation schemes are also included. Any obvious replacement without departing from the concept of the present technical scheme is within the protection scope of the present invention.

Claims

1. A system for liquefying hydrogen using cold energy from LNG, characterized in that: The invention comprises a nitrogen refrigeration cycle, a cryogenic refrigerant refrigeration cycle, a first heat exchanger (1), a hydrogen compressor (2), a second heat exchanger (3), a third heat exchanger (4), a normal-parahydrogen conversion reactor (5), a fourth heat exchanger (6) and a hydrogen throttle valve (7). Hydrogen is sequentially liquefied from gaseous state to liquid hydrogen through the first heat exchanger (1), the hydrogen compressor (2), the second heat exchanger (3), the third heat exchanger (4), the normal-parahydrogen conversion reactor (5), the fourth heat exchanger (6) and the hydrogen throttle valve (7). The nitrogen refrigeration cycle is used for heat exchange for the cryogenic refrigerant refrigeration cycle, the second heat exchanger (3), the third heat exchanger (4) and the normal-parahydrogen conversion reactor (5). The cryogenic refrigerant refrigeration cycle is used for deep-cold liquefaction of hydrogen.

2. A system for liquefying hydrogen using cold energy of LNG according to claim 1, characterized in that: The nitrogen refrigeration cycle comprises a nitrogen compressor (8), a fifth heat exchanger (9), a nitrogen expander (10) and a nitrogen throttle valve (11). Nitrogen is compressed by the nitrogen compressor (8), and the compressed nitrogen is cooled by the fifth heat exchanger (9). The cooled nitrogen is expanded and throttled by the nitrogen expander (10) and the nitrogen throttle valve (11) and then cooled again. The nitrogen cooled again is used as a cold source to heat and reheat the normal-para-hydrogen conversion reactor (5) and the third heat exchanger (4). The nitrogen after heat exchange and reheating is used as a cold source to heat and reheat the second heat exchanger (3) again to meet the minimum inlet temperature requirement of the nitrogen compressor (8). The nitrogen after heat exchange and reheating is compressed in the nitrogen compressor (8) again, and the cycle is repeated.

3. A system for liquefying hydrogen using cold energy of LNG according to claim 2, characterized in that: The cryogenic refrigerant refrigeration cycle includes a cryogenic refrigerant compressor (12), a sixth heat exchanger (13), and a cryogenic refrigerant expander (14). The cryogenic refrigerant is compressed and pressurized by the cryogenic refrigerant compressor (12). The compressed cryogenic refrigerant enters the sixth heat exchanger (13) for heat exchange and cooling. The cryogenic refrigerant after heat exchange passes through the third heat exchanger (4) for heat exchange and cooling again, and then enters the fourth heat exchanger (6) for further heat exchange and cooling for the first time, then enters the cryogenic refrigerant expander (14) for expansion and cooling, and then enters the fourth heat exchanger (6) again as a cold source for heat exchange. The reheated cryogenic refrigerant passes through the second heat exchanger (3) for reheating again to reach the minimum inlet temperature requirement of the cryogenic refrigerant compressor (12), and then the cryogenic refrigerant enters the cryogenic refrigerant compressor (12) for compression, and the cycle continues.

4. A system for liquefying hydrogen using cold energy of LNG according to claim 1, characterized in that: The cold source of the first heat exchanger (1) is LNG cold energy, and the first heat exchanger (1) is used for heat exchange and temperature reduction of hydrogen.

5. The system for liquefying hydrogen using cold energy of LNG according to claim 3, characterized in that: The cold source of the second heat exchanger (3) is LNG cold energy, cold energy of nitrogen reheating before entering the nitrogen compressor (8) in the nitrogen refrigeration cycle, and cold energy of cryogenic refrigerant reheating before entering the cryogenic refrigerant compressor (12) in the cryogenic refrigerant refrigeration cycle. The second heat exchanger (3) is used for heat exchange and cooling of hydrogen. The second heat exchanger (3) is used for nitrogen reheating so that it reaches the minimum inlet temperature requirement of the nitrogen compressor (8). The second heat exchanger (3) is also used for cryogenic refrigerant reheating so that it reaches the minimum inlet temperature requirement of the cryogenic refrigerant compressor (12).

6. A system for liquefying hydrogen using cold energy of LNG according to claim 3, characterized in that: The cold source of the third heat exchanger (4) is the cold energy generated by nitrogen expansion / throttling refrigeration in the nitrogen refrigeration cycle. The third heat exchanger (4) is used for heat exchange and cooling of hydrogen. The third heat exchanger (4) is also used for heat exchange and cooling of the cryogenic refrigerant before it enters the fourth heat exchanger (6) for the first time.

7. The system for liquefying hydrogen using cold energy of LNG according to claim 3, characterized in that: The cold source of the fourth heat exchanger (6) is the cold energy generated by the expansion refrigeration of the cryogenic refrigerant in the cryogenic refrigerant refrigeration cycle. The fourth heat exchanger (6) is used to cryogenically cool the hydrogen to liquefy it.

8. The system for liquefying hydrogen using cold energy of LNG according to claim 3, characterized in that: The cold sources of the fifth heat exchanger (9) and the sixth heat exchanger (13) are both LNG cold energy.

9. The system for liquefying hydrogen using cold energy of LNG according to claim 3, characterized in that: The cryogenic cryogen includes helium cryogen, hydrogen cryogen or helium-hydrogen mixed cryogen.

10. A method for liquefying hydrogen using LNG cold energy, characterized in that: The following steps are involved: S1: Producing hydrogen by electrolysis of water as the input source of raw hydrogen; S2: LNG cold energy, nitrogen refrigeration cycle, and cryogenic refrigerant refrigeration cycle are set to provide cooling and liquefaction support for hydrogen. LNG cold energy, nitrogen refrigeration cycle, and cryogenic refrigerant refrigeration cycle are used crosswise to achieve the purpose of fully utilizing energy and using LNG cold energy as much as possible for cooling; S3: The cryogenic hydrogen continues to be throttled and cooled to a temperature below the liquefaction temperature corresponding to the storage pressure of the liquid hydrogen storage tank; S4: Set up a liquid hydrogen storage tank, and the hydrogen enters the tank for storage after liquefaction.

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