Hydrogen liquefaction method and system

Abstract

The invention relates to a hydrogen liquefaction method and system, and the method comprises the steps: enabling a hydrogen raw material to enter a heat exchanger group for cooling after the hydrogen raw material is boosted to a higher pressure; and the obtained cryogenic hydrogen is subjected to two times of expansion refrigeration through a throttling valve and an expansion machine, and then the obtained extremely cold hydrogen is subjected to heat exchange with the pressurized hydrogen through the heat exchanger set and then returns to the hydrogen compressor. By adopting the method disclosed by the invention, on one hand, the yield of circulating hydrogen can be increased under the condition of ensuring that the gas-liquid mixed hydrogen has a relatively high liquefaction component, so that the yield of extremely cold hydrogen serving as a cooling medium can be increased; and on the other hand, the extremely cold hydrogen is adopted for heat exchange, the heat exchange effect of the heat exchanger set can be improved, and then heat balance of the system can be achieved. And on the other hand, the hydrogen raw material is pressurized to a high pressure, then depressurized to a low level and then subjected to secondary expansion refrigeration, the power consumption of the hydrogen compressor and the expansion machine can be reduced, and then the total power consumption and energy consumption of the system can be reduced.

Description

Technical Field

[0001] The present disclosure relates to the field of hydrogen storage and transportation, and particularly to a method and a system for hydrogen liquefaction. Background Art

[0002] Hydrogen is the cleanest energy source. With the development of technology, it is gradually widely used in fields such as fine chemical industry and powder metallurgy. During the transportation process, hydrogen is generally liquefied into liquid hydrogen for long-distance transportation.

[0003] The Claude liquefaction process and the Linde-Hampson liquefaction process are the two current mainstream processes. In the hydrogen system of the Claude liquefaction process, the pressure is relatively low, and the exhaust pressure of the hydrogen compressor is small. In this process, the hydrogen in the high-temperature area is shunted and then enters the expander for refrigeration; in the Linde-Hampson process, the exhaust pressure of the hydrogen compressor is relatively high, and a throttle valve is used for expansion refrigeration. Due to the large energy loss during the throttling process, the energy efficiency of the system is low. The energy consumption of these two processes is relatively high. Therefore, the existing hydrogen liquefaction processes are complex and have high energy consumption, which is the main problem for the large-scale development of the industry. Summary of the Invention

[0004] The purpose of the present disclosure is to provide a method and a system for hydrogen liquefaction to solve the problems of complex process and high energy consumption existing in the prior art.

[0005] To achieve the above purpose, the first aspect of the present disclosure provides a method for hydrogen liquefaction, which includes: boosting the pressure of a hydrogen raw material by a hydrogen compressor to obtain boosted hydrogen with a pressure of 10.2 - 15.9 MPa; cooling the boosted hydrogen through a heat exchanger group to obtain cryogenic hydrogen; performing primary expansion refrigeration on the cryogenic hydrogen through a throttle valve to obtain gas-liquid mixed hydrogen; the valve downstream pressure of the primary expansion refrigeration is 1 - 1.5 MPa; separating the gas-liquid mixed hydrogen in a gas-liquid separation tank to obtain recycled hydrogen and liquid hydrogen products; performing secondary expansion refrigeration on the recycled hydrogen through an expander to obtain ultra-cryogenic hydrogen; allowing the ultra-cryogenic hydrogen to enter the heat exchanger group to exchange heat with the boosted hydrogen and then return to the inlet of the hydrogen compressor; using liquid nitrogen as a cold source to enter the heat exchanger group to exchange heat with the boosted hydrogen.

[0006] Optionally, the heat exchanger group includes a plurality of heat exchangers. Inside the heat exchanger group, the boosted hydrogen contacts the ultra-cryogenic hydrogen in a countercurrent manner, and the boosted hydrogen contacts the liquid nitrogen in a countercurrent manner.

[0007] Optionally, the heat exchanger group includes a first heat exchanger, a second heat exchanger, a third heat exchanger, and a fourth heat exchanger that are connected in sequence; the method further includes cooling the boosted hydrogen gas successively through the first heat exchanger, the second heat exchanger, the third heat exchanger, and the fourth heat exchanger to obtain the cryogenic hydrogen gas; heating the ultra-cryogenic hydrogen gas successively through the fourth heat exchanger, the third heat exchanger, the second heat exchanger, and the first heat exchanger and then returning it to the hydrogen compressor; and heating the liquid nitrogen in the liquid nitrogen storage tank successively through the third heat exchanger, the second heat exchanger, and the first heat exchanger and then returning it to the liquid nitrogen storage tank.

[0008] Optionally, the pressure of the boosted hydrogen gas is 10.48 - 15.74 MPa; the pressure of the gas-liquid mixed hydrogen is 1 - 1.5 MPa; the pressure of the ultra-cryogenic hydrogen gas is 0.01 - 0.08 MPa.

[0009] Optionally, the temperature of the cryogenic hydrogen gas is -238 to -225 °C, and the temperature of the ultra-cryogenic hydrogen gas is -252 to -245 °C.

[0010] Optionally, the method further includes mixing the ultra-cryogenic hydrogen gas with the hydrogen raw material to 20 - 25 °C before the ultra-cryogenic hydrogen gas returns to the hydrogen compressor.

[0011] Optionally, the concentration of hydrogen in the hydrogen raw material is 99.9999 vol% or more.

[0012] In a second aspect of the present disclosure, a system for liquefying hydrogen using the method described in the first aspect is provided. The system includes a hydrogen compressor, a heat exchanger group, a throttle valve, a gas-liquid separation tank, and an expander; the hydrogen compressor includes a hydrogen raw material inlet, a heat exchange medium inlet, and a boosted hydrogen gas outlet; the heat exchanger group includes a boosted hydrogen gas inlet, an ultra-cryogenic hydrogen gas inlet, a liquid nitrogen cold source inlet, a cryogenic hydrogen gas outlet, a heat exchange medium outlet, and a liquid nitrogen cold source outlet; the throttle valve includes a cryogenic hydrogen gas inlet and a gas-liquid mixed hydrogen outlet; the gas-liquid separation tank includes a gas-liquid mixed hydrogen inlet and a recycled hydrogen gas outlet; the expander includes a recycled hydrogen gas inlet and an ultra-cryogenic hydrogen gas outlet; the boosted hydrogen gas outlet of the hydrogen compressor is connected to the boosted hydrogen gas inlet of the heat exchanger group; the cryogenic hydrogen gas outlet of the heat exchanger group is connected to the cryogenic hydrogen gas inlet of the throttle valve; the gas-liquid mixed hydrogen outlet of the throttle valve is connected to the gas-liquid mixed hydrogen inlet of the gas-liquid separation tank; the recycled hydrogen gas outlet of the gas-liquid separation tank is connected to the recycled hydrogen gas inlet of the expander; the ultra-cryogenic hydrogen gas outlet of the expander is connected to the ultra-cryogenic hydrogen gas inlet of the heat exchanger group; the heat exchange medium outlet of the heat exchanger group is connected to the heat exchange medium inlet of the hydrogen compressor; and the liquid nitrogen cold source inlet of the heat exchanger group is connected to a liquid nitrogen source.

[0013] Optionally, the heat exchanger group includes a first heat exchanger, a second heat exchanger, a third heat exchanger, and a fourth heat exchanger; an inlet of the first heat exchanger is communicated with a boosted hydrogen outlet of the hydrogen compressor; an outlet of the first heat exchanger is communicated with an inlet of the second heat exchanger, and an outlet of the second heat exchanger is communicated with an inlet of the third heat exchanger; an outlet of the third heat exchanger is communicated with an inlet of the fourth heat exchanger; an outlet of the fourth heat exchanger is communicated with a cryogenic hydrogen inlet of the throttle valve; a cooling medium inlet of the fourth heat exchanger is communicated with an extremely cold medium outlet of the expander; a heat exchange medium outlet of the fourth heat exchanger is communicated with a heat exchange medium inlet of the third heat exchanger; a heat exchange medium outlet of the third heat exchanger is communicated with a heat exchange medium inlet of the second heat exchanger; a heat exchange medium outlet of the second heat exchanger is communicated with a heat exchange medium inlet of the first heat exchanger; and a heat exchange medium outlet of the first heat exchanger is communicated with a heat exchange medium inlet of the hydrogen compressor.

[0014] Optionally, the system further includes a liquid nitrogen storage tank, which includes a liquid nitrogen inlet and a liquid nitrogen outlet; the liquid nitrogen outlet of the liquid nitrogen storage tank is communicated with a liquid nitrogen cold source inlet of the third heat exchanger; a liquid nitrogen cold source outlet of the third heat exchanger is communicated with a liquid nitrogen cold source inlet of the second heat exchanger; a liquid nitrogen cold source outlet of the second heat exchanger is communicated with a liquid nitrogen cold source inlet of the first heat exchanger; and a liquid nitrogen cold source outlet of the first heat exchanger is communicated with the liquid nitrogen inlet of the liquid nitrogen storage tank.

[0015] Through the above technical solution, the present disclosure boosts the hydrogen raw material to a relatively high pressure and then enters the heat exchanger group for temperature reduction, and enables the obtained cryogenic hydrogen to undergo a primary expansion refrigeration through the throttle valve and then enables the circulating hydrogen to undergo a secondary expansion refrigeration through the expander, and enables the obtained extremely cold hydrogen to return to the hydrogen compressor after heat exchange with the boosted hydrogen through the heat exchanger group. By adopting the method of the present disclosure, on the one hand, it is possible to increase the output of the circulating hydrogen while ensuring that the gas-liquid mixed hydrogen has a relatively high liquefaction component, and thus it is possible to increase the output of the extremely cold hydrogen serving as the cooling medium; on the other hand, by using the above-mentioned extremely cold hydrogen for heat exchange, it is possible to improve the heat exchange effect of the heat exchanger group, and thus it is possible to achieve the thermal balance of the system. On the further hand, boosting the hydrogen raw material to a relatively high pressure and then reducing the pressure to a relatively low level before performing the secondary expansion refrigeration can reduce the power consumption of the hydrogen compressor and the expander, and thus can reduce the total power consumption and energy consumption of the system.

[0016] Other features and advantages of the present disclosure will be described in detail in the subsequent specific implementation section. Description of the Drawings

[0017] The drawings are used to provide a further understanding of the present disclosure, and constitute a part of the specification. Together with the following specific implementation, they are used to explain the present disclosure, but do not constitute a limitation to the present disclosure. In the drawings:

[0018] Figure 1 It is a schematic diagram of a hydrogen liquefaction system of the present disclosure.

[0019] Description of the reference numerals in the drawings

[0020] 1 Hydrogen compressor; 2 First heat exchanger; 3 Second heat exchanger; 4 Third heat exchanger; 5 Fourth heat exchanger; 6 Throttle valve; 7 Gas-liquid separation tank; 8 Expander; 9 Liquid nitrogen storage tank; A Hydrogen raw material; B Liquid hydrogen product; C Supplementary liquid nitrogen. Specific embodiments

[0021] The following will describe in detail the specific embodiments of the present disclosure with reference to the drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present disclosure, and are not used to limit the present disclosure.

[0022] As Figure 1 shown, the first aspect of the present disclosure provides a method for hydrogen liquefaction, the method comprising: boosting the pressure of the hydrogen raw material A to by a hydrogen compressor 1 to obtain boosted hydrogen with a pressure of 10.2 - 15.9 MPa; cooling the boosted hydrogen through a heat exchanger group to obtain cryogenic hydrogen; subjecting the cryogenic hydrogen to a first expansion refrigeration through a throttle valve 6 to obtain gas-liquid mixed hydrogen; the valve outlet pressure of the first expansion refrigeration being 1 - 1.5 MPa; separating the gas-liquid mixed hydrogen in a gas-liquid separation tank 7 to obtain recycled hydrogen and a liquid hydrogen product B; subjecting the recycled hydrogen to a second expansion refrigeration through an expander 8 to obtain ultra-cryogenic hydrogen; introducing the ultra-cryogenic hydrogen into the heat exchanger group to exchange heat with the boosted hydrogen and then returning it to the inlet of the hydrogen compressor 1; introducing liquid nitrogen as a cold source into the heat exchanger group to exchange heat with the boosted hydrogen.

[0023] Through the above technical solution, the present disclosure boosts the pressure of the hydrogen raw material to a relatively high pressure and then enters the heat exchanger group for cooling, and subjects the obtained cryogenic hydrogen to a first expansion refrigeration through a throttle valve and then subjects the recycled hydrogen to a second expansion refrigeration through an expander, and returns the obtained ultra-cryogenic hydrogen to the hydrogen compressor after exchanging heat with the boosted hydrogen through the heat exchanger group. By adopting the method of the present disclosure, on the one hand, it is possible to increase the output of recycled hydrogen while ensuring that the gas-liquid mixed hydrogen has a relatively high liquefaction component, and thus it is possible to increase the output of ultra-cryogenic hydrogen as a cooling medium; on the other hand, using the above ultra-cryogenic hydrogen for heat exchange can improve the heat exchange effect of the heat exchanger group, and thus it is possible to achieve the heat balance of the system. On the other hand, boosting the pressure of the hydrogen raw material to a relatively high pressure and then reducing the pressure to a relatively low level before performing the second expansion refrigeration can reduce the power consumption of the hydrogen compressor and the expander, and thus it is possible to reduce the total power consumption and energy consumption of the system.

[0024] The source of hydrogen raw material A used in the present disclosure is a conventional choice in the art. Preferably, hydrogen raw material A is high-purity green hydrogen after purification treatment. Among them, the concentration of hydrogen in hydrogen raw material A is above 99.9999% by volume.

[0025] In one embodiment, the method further includes mixing the extremely cold hydrogen with the hydrogen raw material A to 20 - 25°C, preferably 20°C, before the extremely cold hydrogen returns to the hydrogen compressor 1. In this embodiment, since the temperature of the extremely cold hydrogen is very low compared to the temperature of the boosted hydrogen, the temperature of the extremely cold hydrogen increases after heat exchange through the heat exchanger group, but it is still relatively low compared to the temperature of the hydrogen raw material A. When the hydrogen raw material A and the heat-exchanged extremely cold hydrogen are mixed, it can preliminarily cool the hydrogen raw material A, not only reducing the power consumption of the hydrogen compressor 1 but also improving the cooling effect of the subsequent heat exchanger group.

[0026] The hydrogen compressor 1 used in the present disclosure is a conventional choice in the art, and no special requirements are made in this application. In this embodiment, the greater the pressure of the boosted hydrogen obtained after the hydrogen raw material A is boosted by the hydrogen compressor 1, especially when the pressure of the boosted hydrogen is greater than 15.9 MPa, the processing capacity of the heat exchanger group will increase, but the temperature of the hydrogen will rise and the energy consumption of the heat exchanger group will also increase; the smaller the pressure of the boosted hydrogen, especially when the pressure of the boosted hydrogen is less than 10.2 MPa, due to the excessive liquefied component after throttling, the circulating hydrogen flow rate is too small, resulting in insufficient cooling capacity of the heat exchanger group and unbalanced system heat. Therefore, in order to ensure the balance of system heat while reducing the energy consumption of the system, the pressure of the boosted hydrogen can be maintained at a certain level. The pressure of the boosted hydrogen is 10.2 - 15.9 MPa, preferably 10.48 - 15.74 MPa, and further preferably 10.48 MPa. Among them, the temperature of the boosted hydrogen after being compressed by the hydrogen compressor 1 is 109 - 179°C, preferably 160 - 179°C.

[0027] In one embodiment, the heat exchanger group includes a plurality of heat exchangers. Inside the heat exchanger group, the boosted hydrogen contacts the extremely cold hydrogen in a countercurrent manner, and the boosted hydrogen contacts the liquid nitrogen in a countercurrent manner.

[0028] The heat exchanger group of the present disclosure includes a first heat exchanger 2, a second heat exchanger 3, a third heat exchanger 4, and a fourth heat exchanger 5 that are connected in sequence; among them, the heat exchangers in the heat exchanger group are conventional choices in the art, and no special requirements are made in this application.

[0029] In one embodiment, the method further includes cooling the boosted hydrogen gas sequentially through a first heat exchanger 2, a second heat exchanger 3, a third heat exchanger 4, and a fourth heat exchanger 5 to obtain the cryogenic hydrogen gas; and heating the ultra-cryogenic hydrogen gas sequentially through the fourth heat exchanger 5, the third heat exchanger 4, the second heat exchanger 3, and the first heat exchanger 2 and then returning it to the hydrogen compressor 1.

[0030] In one embodiment, the method further includes heating the liquid nitrogen in the liquid nitrogen storage tank 9 sequentially through the third heat exchanger 4, the second heat exchanger 3, and the first heat exchanger 2 and then returning it to the liquid nitrogen storage tank 9. In this embodiment, the purity of the liquid nitrogen in the liquid nitrogen storage tank 9 is 99.99%, and the temperature is -196°C.

[0031] In the above embodiment, when the liquid nitrogen and the ultra-cryogenic hydrogen gas are used as the cooling medium, cooling the boosted hydrogen gas sequentially through the first heat exchanger 2, the second heat exchanger 3, and the third heat exchanger 4 can gradually reduce the temperature of the boosted hydrogen gas to -200 to -190°C. By enabling the boosted hydrogen gas to exchange heat with the liquid nitrogen and the ultra-cryogenic hydrogen gas during the countercurrent contact process, the utilization rate of the cold source of the system can be improved, and furthermore, the refrigeration effect of the system can be further enhanced. Then, the outlet material of the third heat exchanger 4 enters the fourth heat exchanger 5 to exchange heat with the ultra-cryogenic hydrogen gas, obtaining cryogenic hydrogen gas with a temperature of -238 to -225°C, preferably -235 to -228°C. Since the temperature of the ultra-cryogenic hydrogen gas is extremely low, after the boosted hydrogen gas enters the fourth heat exchanger to exchange heat with the ultra-cryogenic hydrogen gas, the temperature of the cryogenic hydrogen gas can be further reduced, and thus the refrigeration effect of the system can be further enhanced.

[0032] The throttle valve 6 used in the present disclosure is a conventional selection in the art, and no special requirements are made in this application. The gas-liquid separation tank 7 used in the present disclosure is a conventional selection in the art, and no special requirements are made in this application, as long as it can fully separate the gas and liquid.

[0033] In this embodiment, after the cryogenic hydrogen gas undergoes a primary expansion refrigeration through the throttle valve 6, the hydrogen gas pressure and temperature will further decrease. Since the pressure difference between the cryogenic hydrogen gas and the gas-liquid mixed hydrogen gas obtained after the primary expansion refrigeration is relatively large, therefore, liquid hydrogen product B is generated during the temperature reduction process. Separating the above gas-liquid mixed hydrogen gas can obtain liquid hydrogen product B and gas phase. Using the separated gas phase as the recycled hydrogen gas to undergo a secondary expansion refrigeration through the expander 8 can further reduce the pressure and temperature of the recycled hydrogen gas. Among them, the temperature of the recycled hydrogen gas is -252 to -240°C, preferably -250 to -241°C.

[0034] In one embodiment, in order to increase the content of liquid hydrogen product B while reducing the energy consumption of system refrigeration, the liquefaction fraction of the gas-liquid mixed hydrogen can be maintained at a certain level. Specifically, the liquefaction fraction of the gas-liquid mixed hydrogen is 10-30%, preferably 13-28%. In this embodiment, when the liquefaction fraction of the gas-liquid mixed hydrogen is higher, the vaporization fraction is lower. At this time, although the yield of liquid hydrogen product B can be increased, the content of the recycled hydrogen decreases, resulting in a worse heat exchange effect of the heat exchanger group, and further increasing the refrigeration energy consumption of the system; when the liquefaction fraction of the gas-liquid mixed hydrogen is lower, the vaporization fraction is higher. At this time, although the content of the recycled hydrogen can be increased, making the heat exchange effect of the heat exchanger group better, and further reducing the refrigeration energy consumption of the system, the yield of liquid hydrogen product B will be reduced. In addition, the liquefaction fraction of the gas-liquid mixed hydrogen is controlled by the combined action of the temperature and pressure of the cryogenic hydrogen and the pressure drop of the primary expansion refrigeration. Among them, the pressure of the cryogenic hydrogen is not much different from the pressure of the boosted hydrogen, and the pressure of the gas-liquid mixed hydrogen is preferably 1-1.5 MPa.

[0035] In one embodiment, the pressure of the ultra-cold hydrogen is preferably 0.01-0.08 MPa, and the temperature is -252 to -245 °C, preferably -252 to -249 °C. In this embodiment, the recycled hydrogen is subjected to secondary expansion refrigeration by an expander, which can further reduce the pressure of the recycled hydrogen, or both the pressure and temperature are further reduced, which can further improve the heat exchange effect of the heat exchanger group, and thus reduce the system energy consumption. Among them, the expander 8 used in the present disclosure is a conventional selection in the art, and no special requirements are made in this application.

[0036] In one embodiment, as Figure 1 shown, the method for hydrogen liquefaction includes:

[0037] The hydrogen raw material A is boosted by a hydrogen compressor 1 to obtain boosted hydrogen; the boosted hydrogen is sequentially heat-exchanged through a first heat exchanger 2, a second heat exchanger 3, a third heat exchanger 4 and a fourth heat exchanger 5 to obtain cryogenic hydrogen; among them, the temperature of the boosted hydrogen is 160-179 °C and the pressure is 10.2-15.9 MPa; the temperature of the cryogenic hydrogen is -238 to -225 °C and the pressure is 1-1.5 MPa;

[0038] The cryogenic hydrogen is subjected to primary expansion refrigeration through a throttle valve 6 to obtain gas-liquid mixed hydrogen; the gas-liquid mixed hydrogen enters a gas-liquid separation tank 7 for separation to obtain recycled hydrogen and liquid hydrogen product B; the recycled hydrogen is subjected to secondary expansion refrigeration through an expander 8 to obtain ultra-cold hydrogen; among them, the vaporization fraction of the gas-liquid mixed hydrogen is 10-30%, the temperature of the recycled hydrogen is -252 to -240 °C and the pressure is 1-1.5 MPa; the temperature of the ultra-cold hydrogen is -252 to -245 °C and the pressure is 0.01-0.08 MPa;

[0039] After the extremely cold hydrogen gas passes through the fourth heat exchanger 5, the third heat exchanger 4, the second heat exchanger 3, and the first heat exchanger 2 in sequence to exchange heat with the boosted hydrogen gas, it is then mixed with hydrogen raw material A until the temperature reaches 20 - 25°C and the pressure reaches 0.01 - 0.08 MPa, and then enters the hydrogen compressor 1;

[0040] After the liquid nitrogen in the liquid nitrogen storage tank 9 passes through the third heat exchanger 4, the second heat exchanger 3, and the first heat exchanger 2 in sequence for heat exchange, it returns to the liquid nitrogen storage tank 9. Among them, the purity of the liquid nitrogen in the liquid nitrogen storage tank 9 is 99.99%, and the temperature is -196°C. In order to maintain the liquid nitrogen in the liquid nitrogen storage tank 9 at the above temperature, supplementary liquid nitrogen C can be added to the liquid nitrogen storage tank 9.

[0041] The system for hydrogen liquefaction using the method described in the first aspect of the present disclosure in the second aspect of the present disclosure includes a hydrogen compressor 1, a heat exchanger group, a throttle valve 6, a gas-liquid separation tank 7, and an expander 8; the hydrogen compressor 1 includes a hydrogen raw material inlet, a heat exchange medium inlet, and a boosted hydrogen gas outlet; the heat exchanger group includes a boosted hydrogen gas inlet, an extremely cold hydrogen gas inlet, a liquid nitrogen cold source inlet, a deeply cooled hydrogen gas outlet, a heat exchange medium outlet, and a liquid nitrogen cold source outlet; the throttle valve 6 includes a deeply cooled hydrogen gas inlet and a gas-liquid mixed hydrogen outlet; the gas-liquid separation tank 7 includes a gas-liquid mixed hydrogen inlet and a recycled hydrogen gas outlet; the expander 8 includes a recycled hydrogen gas inlet and an extremely cold hydrogen gas outlet; the boosted hydrogen gas outlet of the hydrogen compressor 1 is communicated with the boosted hydrogen gas inlet of the heat exchanger group; the deeply cooled hydrogen gas outlet of the heat exchanger group is communicated with the deeply cooled hydrogen gas inlet of the throttle valve 6; the gas-liquid mixed hydrogen outlet of the throttle valve 6 is communicated with the gas-liquid mixed hydrogen inlet of the gas-liquid separation tank 7; the recycled hydrogen gas outlet of the gas-liquid separation tank 7 is communicated with the recycled hydrogen gas inlet of the expander 8; the extremely cold hydrogen gas outlet of the expander 8 is communicated with the extremely cold hydrogen gas inlet of the heat exchanger group; the heat exchange medium outlet of the heat exchanger group is communicated with the heat exchange medium inlet of the hydrogen compressor 1; the liquid nitrogen cold source inlet of the heat exchanger group is communicated with a liquid nitrogen source.

[0042] In one embodiment, the heat exchanger group includes a first heat exchanger 2, a second heat exchanger 3, a third heat exchanger 4, and a fourth heat exchanger 5; the inlet of the first heat exchanger 2 is communicated with the boosted hydrogen outlet of the hydrogen compressor 1; the outlet of the first heat exchanger 2 is communicated with the inlet of the second heat exchanger 3, and the outlet of the second heat exchanger 3 is communicated with the inlet of the third heat exchanger 4; the outlet of the third heat exchanger 4 is communicated with the inlet of the fourth heat exchanger 5; the outlet of the fourth heat exchanger 5 is communicated with the cryogenic hydrogen inlet of the throttle valve 6; the cooling medium inlet of the fourth heat exchanger 5 is communicated with the extremely cold medium outlet of the expander 8; the heat exchange medium outlet of the fourth heat exchanger 5 is communicated with the heat exchange medium inlet of the third heat exchanger 4; the heat exchange medium outlet of the third heat exchanger 4 is communicated with the heat exchange medium inlet of the second heat exchanger 3; the heat exchange medium outlet of the second heat exchanger 3 is communicated with the heat exchange medium inlet of the first heat exchanger 2; the heat exchange medium outlet of the first heat exchanger 2 is communicated with the heat exchange medium inlet of the hydrogen compressor 1.

[0043] In one embodiment, the system further includes a liquid nitrogen storage tank 9, and the liquid nitrogen storage tank 9 includes a liquid nitrogen inlet and a liquid nitrogen outlet; the liquid nitrogen outlet of the liquid nitrogen storage tank 9 is communicated with the liquid nitrogen cold source inlet of the third heat exchanger 4; the liquid nitrogen cold source outlet of the third heat exchanger 4 is communicated with the liquid nitrogen cold source inlet of the second heat exchanger 3; the liquid nitrogen cold source outlet of the second heat exchanger 3 is communicated with the liquid nitrogen cold source inlet of the first heat exchanger 2; the liquid nitrogen cold source outlet of the first heat exchanger 2 is communicated with the liquid nitrogen inlet of the liquid nitrogen storage tank 9.

[0044] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto. The hydrogen used in the examples and comparative examples is high-purity green hydrogen obtained after purification treatment, and the purity is 99.9999% by volume.

[0045] Example 1

[0046] Adopt Figure 1 the hydrogen liquefaction system to process the hydrogen raw material A;

[0047] The hydrogen liquefaction method includes: after boosting the hydrogen raw material A by the hydrogen compressor 1, boosted hydrogen is obtained; after the boosted hydrogen is sequentially heat-exchanged through the first heat exchanger 2, the second heat exchanger 3, the third heat exchanger 4, and the fourth heat exchanger 5, cryogenic hydrogen is obtained; wherein, the temperature of the boosted hydrogen is 172 °C and the pressure is 10.48 MPa; the temperature of the cryogenic hydrogen is -232 °C and the pressure is 10.48 MPa;

[0048] Let the cryogenic hydrogen undergo primary expansion refrigeration through throttle valve 6 to obtain gas-liquid mixed hydrogen; let the gas-liquid mixed hydrogen enter gas-liquid separation tank 7 for separation to obtain recycled hydrogen and liquid hydrogen product B; let the recycled hydrogen undergo secondary expansion refrigeration through expander 8 to obtain extremely cold hydrogen; wherein, the temperature of the recycled hydrogen is -241°C and the pressure is 1.1 MPa; the temperature of the extremely cold hydrogen is -252°C and the pressure is 0.05 MPa;

[0049] Let the extremely cold hydrogen sequentially pass through the fourth heat exchanger 5, the third heat exchanger 4, the second heat exchanger 3, and the first heat exchanger 2 to exchange heat with the boosted hydrogen, and then mix with the boosted hydrogen until the temperature reaches 20°C and the pressure reaches 0.05 MPa, and then return to the hydrogen compressor 1;

[0050] Let the liquid nitrogen in the liquid nitrogen storage tank 9 be used as a cold source and sequentially pass through the third heat exchanger 4, the second heat exchanger 3, and the first heat exchanger 2 for heat exchange and then return to the liquid nitrogen storage tank 9, wherein the purity of the liquid nitrogen in the liquid nitrogen storage tank 9 is 99.9999% and the temperature is -196°C.

[0051] The results of the hydrogen liquefaction treatment are shown in Table 1.

[0052] Comparative Example 1

[0053] The Linde-hampson process is used for hydrogen liquefaction. The specific method includes:

[0054] Let hydrogen raw material A be boosted to 10 MPa by a compressor to obtain boosted hydrogen; let the boosted hydrogen sequentially pass through the first heat exchanger, the second heat exchanger, the third heat exchanger, the fourth heat exchanger, and the fifth heat exchanger for heat exchange to obtain cryogenic hydrogen at a temperature of -227°C; let the cryogenic hydrogen undergo expansion treatment through a throttle valve to obtain gas-liquid mixed hydrogen at a temperature of -251°C and a pressure of 0.05 MPa; and let the gas-liquid mixed hydrogen enter a gas-liquid separation device for separation to obtain liquid hydrogen product B and extremely cold hydrogen;

[0055] Let the extremely cold hydrogen sequentially pass through the fifth heat exchanger, the fourth heat exchanger, the third heat exchanger, the second heat exchanger, and the first heat exchanger for heat exchange and then return to the compressor.

[0056] The results of the hydrogen liquefaction treatment are shown in Table 1.

[0057] Comparative Example 2

[0058] The Claude process is used for hydrogen liquefaction. The specific method includes:

[0059] After the hydrogen gas is boosted to 3 MPa by a compressor, pressurized hydrogen gas is obtained; after the pressurized hydrogen gas is heat-exchanged in a first heat exchanger, a part of the heat-exchanged pressurized hydrogen gas is sequentially heat-exchanged in a second heat exchanger and a third heat exchanger to obtain cryogenic hydrogen gas; after the cryogenic hydrogen gas is depressurized to 0.2 MPa by a throttle valve and then undergoes gas-liquid separation, extremely cold hydrogen gas and liquid hydrogen product B are obtained; the extremely cold hydrogen gas is sequentially heat-exchanged in the third heat exchanger, the second heat exchanger and the first heat exchanger 2 and then returned to the compressor;

[0060] Another part of the heat-exchanged pressurized hydrogen gas is depressurized to 0.2 MPa by an expander and then mixed with the recycled hydrogen gas heat-exchanged in the third heat exchanger.

[0061] The results of the hydrogen liquefaction treatment are shown in Table 1.

[0062] Comparative Example 3

[0063] The method for hydrogen liquefaction is the same as that in Example 1, except that the pressure of the pressurized hydrogen gas is 9.5 MPa and no additional cold source or cooling device is added. The results of the hydrogen liquefaction treatment are shown in Table 1.

[0064] Comparative Example 4

[0065] The method for hydrogen liquefaction is the same as that in Example 1, except that the pressure of the recycled hydrogen gas is 12 MPa. The results of the hydrogen liquefaction treatment are shown in Table 1.

[0066] Table 1 Results of the hydrogen liquefaction treatment in the examples and comparative examples.

[0067]

[0068]

[0069] Among them, the total power consumption refers to the difference between the power of the hydrogen compressor and the power of the expander.

[0070] As shown in Table 1, by comparing the data in Example 1 and Comparative Examples 1 to 4, it can be seen that by using the method of the present disclosure, not only can the heat exchange effect of the heat exchanger group be improved, thereby achieving the thermal balance of the system, but also the total power consumption and energy consumption of the system can be reduced. By comparing the data in Example 1 and Comparative Example 3, it can be seen that when the pressure of the boosted hydrogen is 10.2 - 15.9 MPa, not only can the production of the recycled hydrogen be increased while ensuring a relatively high liquefaction component in the gas-liquid mixed hydrogen, but also the heat exchange effect of the heat exchanger group can be improved, thereby achieving the thermal balance of the system. When the pressure of the boosted hydrogen is less than 10.2 MPa, due to the excessive liquefaction component after throttling, the flow rate of the recycled hydrogen is too small, resulting in insufficient cold energy of the heat exchanger group. Without adding a cold source or refrigeration device, the heat balance of the system cannot be achieved. By comparing the data in Example 1 and Comparative Example 4, it can be seen that boosting the hydrogen raw material to a relatively high pressure and then reducing it to a lower level and then performing secondary expansion refrigeration can reduce the power consumption of the hydrogen compressor and expander, thereby reducing the total power consumption and energy consumption of the system.

[0071] The preferred embodiments of the present disclosure have been described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0072] In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without conflict. To avoid unnecessary repetition, the present disclosure will not separately describe various possible combination methods.

[0073] Furthermore, any combination can be made between various different embodiments of the present disclosure, as long as it does not violate the idea of the present disclosure, and it should also be regarded as the content disclosed by the present disclosure.

Claims

1. A method for liquefying hydrogen, characterized in that, The method includes: Boosting the pressure of the hydrogen raw material by a hydrogen compressor (1) to obtain boosted hydrogen with a pressure of 10.2 - 15.9 MPa; cooling the boosted hydrogen through a heat exchanger group to obtain cryogenic hydrogen; Performing primary expansion refrigeration on the cryogenic hydrogen through a throttle valve (6) to obtain gas - liquid mixed hydrogen; the pressure after the valve of the primary expansion refrigeration is 1 - 1.5 MPa; feeding the gas - liquid mixed hydrogen into a gas - liquid separation tank (7) for separation to obtain recycled hydrogen and liquid hydrogen product; Performing secondary expansion refrigeration on the recycled hydrogen through an expander (8) to obtain ultra - cold hydrogen; Feeding the ultra - cold hydrogen into the heat exchanger group to exchange heat with the boosted hydrogen and then returning to the inlet of the hydrogen compressor (1); feeding liquid nitrogen as a cold source into the heat exchanger group to exchange heat with the boosted hydrogen.

2. The method according to claim 1, characterized in that, The heat exchanger group includes multiple heat exchangers. Inside the heat exchanger group, the boosted hydrogen contacts the ultra - cold hydrogen in a counter - current manner, and the boosted hydrogen contacts the liquid nitrogen in a counter - current manner.

3. The method according to claim 2, wherein The heat exchanger group includes a first heat exchanger (2), a second heat exchanger (3), a third heat exchanger (4), and a fourth heat exchanger (5) connected in sequence; The method further includes cooling the boosted hydrogen sequentially through the first heat exchanger (2), the second heat exchanger (3), the third heat exchanger (4), and the fourth heat exchanger (5) to obtain the cryogenic hydrogen; Heating the ultra - cold hydrogen sequentially through the fourth heat exchanger (5), the third heat exchanger (4), the second heat exchanger (3), and the first heat exchanger (2) and then returning it to the hydrogen compressor (1); Heating the liquid nitrogen in a liquid nitrogen storage tank (9) sequentially through the third heat exchanger (4), the second heat exchanger (3), and the first heat exchanger (2) and then returning it to the liquid nitrogen storage tank (9).

4. The method according to claim 1, characterized in that The pressure of the boosted hydrogen is 10.48 - 15.74 MPa; the pressure of the gas - liquid mixed hydrogen is 1 - 1.5 MPa; the pressure of the ultra - cold hydrogen is 0.01 - 0.08 MPa.

5. The method according to claim 1, wherein The temperature of the cryogenic hydrogen is - 238 to - 225 °C, and the temperature of the ultra - cold hydrogen is - 252 to - 245 °C.

6. The method according to claim 1, wherein The method further includes mixing the ultra - cold hydrogen with the hydrogen raw material to 20 - 25 °C before the ultra - cold hydrogen returns to the hydrogen compressor (1).

7. The method according to claim 1, wherein The concentration of hydrogen in the hydrogen raw material is 99.9999 vol% or more.

8. A system for hydrogen liquefaction using the method according to any one of claims 1 to 7, characterized in that, The system includes a hydrogen compressor (1), a heat exchanger group, a throttle valve (6), a gas - liquid separation tank (7), and an expander (8); The hydrogen compressor (1) includes a hydrogen raw material inlet, a heat exchange medium inlet, and a boosted hydrogen outlet; The heat exchanger group includes a boosted hydrogen inlet, an ultra - cold hydrogen inlet, a liquid nitrogen cold source inlet, a cryogenic hydrogen outlet, a heat exchange medium outlet, and a liquid nitrogen cold source outlet; The throttle valve (6) includes a cryogenic hydrogen inlet and a gas - liquid mixed hydrogen outlet; The gas - liquid separation tank (7) includes a gas - liquid mixed hydrogen inlet and a recycled hydrogen outlet; The expander (8) includes a recycled hydrogen inlet and an ultra - cold hydrogen outlet; The boosted hydrogen outlet of the hydrogen compressor (1) is communicated with the boosted hydrogen inlet of the heat exchanger group; the cryogenic hydrogen outlet of the heat exchanger group is communicated with the cryogenic hydrogen inlet of the throttle valve (6); the gas-liquid mixed hydrogen outlet of the throttle valve (6) is communicated with the gas-liquid mixed hydrogen inlet of the gas-liquid separation tank (7); the recycled hydrogen outlet of the gas-liquid separation tank (7) is communicated with the recycled hydrogen inlet of the expander (8); the extremely cold hydrogen outlet of the expander (8) is communicated with the extremely cold hydrogen inlet of the heat exchanger group; the heat transfer medium outlet of the heat exchanger group is communicated with the heat transfer medium inlet of the hydrogen compressor (1); the liquid nitrogen cold source inlet of the heat exchanger group is communicated with the liquid nitrogen source.

9. The system according to claim 8, wherein The heat exchanger group includes a first heat exchanger (2), a second heat exchanger (3), a third heat exchanger (4) and a fourth heat exchanger (5); The inlet of the first heat exchanger (2) is communicated with the boosted hydrogen outlet of the hydrogen compressor (1); the outlet of the first heat exchanger (2) is communicated with the inlet of the second heat exchanger (3), and the outlet of the second heat exchanger (3) is communicated with the inlet of the third heat exchanger (4); the outlet of the third heat exchanger (4) is communicated with the inlet of the fourth heat exchanger (5); the outlet of the fourth heat exchanger (5) is communicated with the cryogenic hydrogen inlet of the throttle valve (6); The cooling medium inlet of the fourth heat exchanger (5) is communicated with the extremely cold medium outlet of the expander (8); the heat transfer medium outlet of the fourth heat exchanger (5) is communicated with the heat transfer medium inlet of the third heat exchanger (4); the heat transfer medium outlet of the third heat exchanger (4) is communicated with the heat transfer medium inlet of the second heat exchanger (3); the heat transfer medium outlet of the second heat exchanger (3) is communicated with the heat transfer medium inlet of the first heat exchanger (2); the heat transfer medium outlet of the first heat exchanger (2) is communicated with the heat transfer medium inlet of the hydrogen compressor (1).

10. The system according to claim 9, wherein, The system further includes a liquid nitrogen storage tank (9), and the liquid nitrogen storage tank (9) includes a liquid nitrogen inlet and a liquid nitrogen outlet; The liquid nitrogen outlet of the liquid nitrogen storage tank (9) is communicated with the liquid nitrogen cold source inlet of the third heat exchanger (4); the liquid nitrogen cold source outlet of the third heat exchanger (4) is communicated with the liquid nitrogen cold source inlet of the second heat exchanger (3); the liquid nitrogen cold source outlet of the second heat exchanger (3) is communicated with the liquid nitrogen cold source inlet of the first heat exchanger (2); the liquid nitrogen cold source outlet of the first heat exchanger (2) is communicated with the liquid nitrogen inlet of the liquid nitrogen storage tank (9).

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