A hydrogen liquefaction system and its mixed precooling unit

Abstract

This invention provides a hydrogen liquefaction system and its mixed precooling unit. The mixed precooling unit includes a precooling heat exchanger unit and a mixed precooling compressor unit. After the raw hydrogen enters the precooling heat exchanger unit, it is cooled to a preset temperature by the mixed precooling agent provided by the mixed precooling compressor unit. The precooling heat exchanger unit includes a first precooling heat exchanger, a second precooling heat exchanger, and a third precooling heat exchanger. The mixed precooling compressor unit includes a mixed precooling compressor, a mixed precooling balance tank, a mixed precooling primary refrigeration throttling valve, a mixed precooling primary refrigeration flash tank, a mixed precooling low-temperature separation tank, a mixed precooling secondary refrigeration throttling valve, a mixed precooling secondary refrigeration flash tank, a mixed precooling tertiary refrigeration throttling valve, and a mixed precooling tertiary refrigeration flash tank. This invention refluxes heavier components in the liquid phase at higher temperatures, reducing the content of heavier components in the precooling agent at lower temperatures and preventing low-temperature freezing blockage.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen liquefaction technology, specifically, it relates to a hydrogen liquefaction system and a precooling unit with a mixed precooling agent. Background Technology

[0002] With the increasing global demand for clean energy, hydrogen energy, as a highly efficient and clean secondary energy source, has received widespread attention. Liquid hydrogen, due to its high energy density and ease of storage and transportation, has become a key component in large-scale hydrogen energy applications. However, the current hydrogen liquefaction process faces challenges such as high energy consumption and high costs, severely hindering the commercialization and application of liquid hydrogen technology.

[0003] Traditional hydrogen liquefaction methods typically employ multi-stage compression and expansion cycles, with liquid nitrogen precooling combined with helium or hydrogen expansion cooling being a common approach. In this method, the hydrogen is first precooled using the low temperature of liquid nitrogen, and then further cooled using helium or hydrogen expansion cooling until liquefaction occurs. While this method can achieve hydrogen liquefaction to some extent, it has several drawbacks.

[0004] On the one hand, the liquid nitrogen precooling process is an open system that requires a continuous consumption of liquid nitrogen. The preparation of liquid nitrogen itself consumes a large amount of energy, which undoubtedly increases the energy consumption of the entire hydrogen liquefaction process. Moreover, the stability of the liquid nitrogen supply depends on external liquid nitrogen manufacturers, increasing the complexity and uncertainty of the supply chain. For example, in some remote areas or regions with unstable liquid nitrogen supply, the normal operation of the hydrogen liquefaction plant may be affected by the interruption of the liquid nitrogen supply.

[0005] On the other hand, traditional methods are inefficient in the heat exchange process. Because they use a single cryogenic medium for precooling, they cannot precisely match the cooling requirements of hydrogen at different temperature stages, resulting in a large temperature gradient during heat exchange and thus significant thermodynamic irreversible losses. This loss not only wastes energy but also keeps the energy consumption of the entire hydrogen liquefaction system high. Statistics show that traditional hydrogen liquefaction systems using liquid nitrogen precooling combined with helium or hydrogen expansion refrigeration typically consume 13–15 kWh / kgLH2, making liquid hydrogen production costly and uncompetitive in the market.

[0006] Furthermore, traditional technologies struggle to meet the demands of high-efficiency and stable production when facing large-scale hydrogen liquefaction needs. With the development of the hydrogen energy industry, the demand for large-scale hydrogen liquefaction plants with a daily output of 30 tons or more is increasing. The shortcomings of traditional technologies in terms of energy consumption, cost, and system stability are becoming increasingly apparent, severely hindering the large-scale commercialization of the hydrogen energy industry. Therefore, developing a low-energy-consumption, high-efficiency hydrogen liquefaction technology is urgently needed to address the aforementioned problems in existing technologies and promote the widespread application of hydrogen energy and liquid hydrogen technology.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] The technical problem to be solved by this invention is to overcome at least some of the shortcomings of the prior art and provide a mixed precooling unit for a hydrogen liquefaction system. This unit utilizes the different boiling points of the multiple components in the mixed precooling agent to absorb heat at different temperature stages, thereby matching the cooling requirements of the multiple stages in the hydrogen liquefaction process and reducing energy consumption. Furthermore, by employing a three-stage precooling heat exchanger combined with a multi-stage flash tank, on the one hand, the temperature of the hot and cold media can be more closely matched by rationally designing the refrigeration temperature and specific component ratios between the three precooling heat exchangers, reducing precooling energy consumption. On the other hand, heavier components can be refluxed in the liquid phase at higher temperatures, gradually reducing the content of heavier components in the refrigerant at lower temperatures, thus avoiding low-temperature freezing blockage of the precooling heat exchanger due to excessive heavy components during subsequent cooling processes.

[0009] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is: a mixed precooling unit for a hydrogen liquefaction system, including a precooling heat exchanger unit and a mixed precooling compressor unit, wherein the raw material hydrogen enters the precooling heat exchanger unit and is cooled to a preset temperature by the mixed precooling agent provided by the mixed precooling compressor unit;

[0010] The precooling heat exchanger unit includes a first precooling heat exchanger, a second precooling heat exchanger, and a third precooling heat exchanger. The mixed precooling compressor unit includes a mixed precooling compressor, a mixed precooling balance tank, a mixed precooling primary refrigeration throttling valve, a mixed precooling primary refrigeration flash tank, a mixed precooling low-temperature separation tank, a mixed precooling secondary refrigeration throttling valve, a mixed precooling secondary refrigeration flash tank, a mixed precooling tertiary refrigeration throttling valve, and a mixed precooling tertiary refrigeration flash tank.

[0011] The raw material hydrogen gas sequentially passes through the first precooling heat exchanger, the second precooling heat exchanger, and the third precooling heat exchanger. The mixed precooling agent, after being compressed by the mixed precooling agent compressor, enters the mixed precooling agent balance tank, forming high-pressure gaseous refrigerant and high-pressure liquid refrigerant. The high-pressure liquid refrigerant enters the first precooling heat exchanger, where it is throttled and cooled by the first-stage refrigeration throttling valve of the mixed precooling agent. It then enters the flash tank after the first-stage refrigeration of the mixed precooling agent, mixes with the refrigerant returned from the flash tank after the second-stage refrigeration of the mixed precooling agent, and returns to the first precooling heat exchanger for reheating before entering the inlet of the mixed precooling agent compressor, completing the cycle. The high-pressure gaseous refrigerant enters the first precooling heat exchanger and the second... After the precooling heat exchanger, the mixture enters the low-temperature separation tank of the mixed precooling agent to form a liquid phase and a gas phase. The liquid phase is throttled and cooled by the secondary refrigeration throttling valve of the mixed precooling agent, and then enters the flash tank after the secondary refrigeration of the mixed precooling agent. It mixes with the refrigerant returned from the flash tank after the tertiary refrigeration of the mixed precooling agent and returns to the flash tank after the primary refrigeration of the mixed precooling agent. After being reheated by the third and second precooling heat exchangers, it enters the flash tank after the primary refrigeration of the mixed precooling agent. The gas phase is cooled by the third precooling heat exchanger and then throttled and cooled by the tertiary refrigeration throttling valve of the mixed precooling agent. It then enters the flash tank after the tertiary refrigeration of the mixed precooling agent, and after being reheated by the third precooling heat exchanger, it enters the flash tank after the secondary refrigeration of the mixed precooling agent.

[0012] In some embodiments, the mixed precooling agent includes nitrogen, methane, ethane, propane, and isopentane, with molar fractions of each component being 0%–30%, 0%–50%, 0%–30%, 0%–30%, and 0%–30%, respectively.

[0013] In some implementations, the preset temperature range is from 80K to 120K;

[0014] Preferably, the K value is between 85K and 95K.

[0015] 90K is preferred.

[0016] In some embodiments, the mixed precooling agent precooling unit of the hydrogen liquefaction system further includes a precooling box;

[0017] The first, second, and third precooling heat exchangers are disposed in the precooling box. The first-stage refrigeration throttling valve, the first-stage flash evaporator, the low-temperature separator, the second-stage refrigeration throttling valve, the third-stage refrigeration throttling valve, and the third-stage flash evaporator are disposed in the precooling box. The precooling compressor and the precooling balance tank are disposed outside the precooling box.

[0018] The present invention also provides a hydrogen liquefaction system, including the precooling unit of the mixed precooling agent described above.

[0019] In some embodiments, the hydrogen liquefaction system further includes a cryogenic heat exchanger unit, a cryogenic refrigerant compressor unit, and a final-stage throttling valve for the raw material hydrogen path. After cooling, the raw material hydrogen enters the cryogenic heat exchanger unit and is cooled by the cryogenic refrigerant in the cryogenic refrigerant compressor unit. After passing through the final-stage throttling valve for the raw material hydrogen path, it is converted into liquid hydrogen.

[0020] The cryogenic heat exchange unit includes a low-temperature adsorber, a first cryogenic heat exchanger, a second cryogenic heat exchanger, a third cryogenic heat exchanger, a fourth cryogenic heat exchanger, and a fifth cryogenic heat exchanger.

[0021] The cryogenic refrigerant compressor unit includes a cryogenic refrigerant low-pressure compressor, a cryogenic refrigerant medium-pressure compressor, a cryogenic refrigerant circulation primary turbine expander unit, a cryogenic refrigerant circulation secondary turbine expander unit, a cryogenic refrigerant circulation cooler, and a flash tank after the cryogenic refrigerant circulation cooler.

[0022] The cooled raw material hydrogen gas sequentially passes through the first cryogenic heat exchanger, the low-temperature adsorber, the second cryogenic heat exchanger, the third cryogenic heat exchanger, the fourth cryogenic heat exchanger, and the fifth cryogenic heat exchanger. The cryogenic refrigerant, after being compressed by the cryogenic refrigerant medium-pressure compressor, sequentially passes through the first pre-cooling heat exchanger, the second pre-cooling heat exchanger, and the third pre-cooling heat exchanger, where it is cooled by the returned cold low-pressure cryogenic refrigerant, medium-pressure cryogenic refrigerant, and mixed pre-cooling agent. The cooled cryogenic refrigerant then splits into two paths after passing through the first cryogenic heat exchanger. One path enters the cryogenic refrigerant circulation stage one turbine expander unit and returns to the medium-pressure cryogenic refrigerant channel in the second cryogenic heat exchanger. The other path, after passing through the second cryogenic heat exchanger, splits again into two paths. One path enters the cryogenic refrigerant circulation stage two turbine expander unit and returns to the medium-pressure cryogenic refrigerant channel in the third cryogenic heat exchanger. The other path, after passing through the third cryogenic heat exchanger, is cooled by the cryogenic refrigerant circulation cooler.

[0023] The medium-pressure cryogenic refrigerant in the third cryogenic heat exchanger and the second cryogenic heat exchanger passes through the first cryogenic heat exchanger, the third precooling heat exchanger, the second precooling heat exchanger, and the first precooling heat exchanger for reheating before entering the inlet of the medium-pressure cryogenic refrigerant compressor to complete the cycle.

[0024] The hydrogen, after being refrigerated and throttled by the cryogenic refrigerant circulating cooler, becomes a low-pressure cryogenic refrigerant. This low-pressure cryogenic refrigerant enters the flash tank after the cryogenic refrigerant circulating cooler. The gaseous phase therein sequentially passes through the fourth cryogenic heat exchanger, the third cryogenic heat exchanger, the second cryogenic heat exchanger, the first cryogenic heat exchanger, the third precooling heat exchanger, the second precooling heat exchanger, and the first precooling heat exchanger before being reheated and entering the inlet of the low-pressure cryogenic refrigerant compressor. The hydrogen gas at the outlet of the low-pressure cryogenic refrigerant compressor, which is a medium-pressure cryogenic refrigerant, merges with the returning medium-pressure cryogenic refrigerant and enters the inlet of the medium-pressure cryogenic refrigerant compressor. The liquid phase therein returns to the fifth and fourth cryogenic heat exchangers and then merges with the gaseous phase therein.

[0025] In some implementations, the hydrogen liquefaction system also includes a cryogenic cold box;

[0026] The cryogenic adsorber, the first cryogenic heat exchanger, the second cryogenic heat exchanger, the third cryogenic heat exchanger, the fourth cryogenic heat exchanger, and the fifth cryogenic heat exchanger are disposed in the cryogenic cold box.

[0027] The cryogenic refrigerant circulation primary turbine expander, the cryogenic refrigerant circulation secondary turbine expander, the cryogenic refrigerant circulation cooler, and the flash tank after the cryogenic refrigerant circulation cooler are installed in the cryogenic cold box, while the cryogenic refrigerant low-pressure compressor and the cryogenic refrigerant medium-pressure compressor are installed outside the cryogenic cold box.

[0028] In some embodiments, the cryogenic refrigerant cycle primary turbine expander and the cryogenic refrigerant cycle secondary turbine expander are configured in a multi-stage series, multi-stage parallel, or multi-stage series-parallel configuration.

[0029] In some embodiments, the cryogenic refrigerant circulating cooler employs a cryogenic refrigerant circulating throttle valve or a cryogenic refrigerant turbine expander.

[0030] In some embodiments, the cryogenic refrigerant includes hydrogen or a mixture of two or three of hydrogen, helium, and neon.

[0031] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art.

[0032] 1. The mixed precooling unit of the hydrogen liquefaction system provided by this invention utilizes the different boiling points of the components in the mixed precooling agent to absorb heat at different temperature stages, thereby matching the cooling requirements of multiple stages in the hydrogen liquefaction process and reducing energy consumption. Moreover, by adopting a three-stage precooling heat exchanger combined with a three-stage flash tank, on the one hand, the temperature of the hot and cold media can be more closely matched by reasonably designing the refrigeration temperature and specific component ratio between the three precooling heat exchangers, thus reducing precooling energy consumption. On the other hand, the heavier components can be refluxed in the liquid phase at higher temperatures, gradually reducing the content of heavy components in the refrigerant at lower temperatures, thereby avoiding low-temperature freezing blockage of the precooling heat exchanger due to excessive heavy components during subsequent cooling.

[0033] 2. The hydrogen liquefaction system provided by this invention utilizes a mixed precooling agent precooling unit to precool the raw hydrogen to a temperature range of 80K to 100K, creating favorable conditions for the subsequent cryogenic liquefaction process. Then, it combines a helium reverse Brayton cycle or a hydrogen Claude cycle to achieve the final liquefaction of hydrogen, reducing the temperature to around 20K. This integrated approach fully leverages the advantages of different refrigeration technologies, and compared to a single refrigeration technology, the overall system efficiency can be increased by 30% to 40%, further reducing the energy consumption and cost of hydrogen liquefaction.

[0034] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0035] The accompanying drawings, as part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings:

[0036] Figure 1 This is a schematic diagram of a liquid hydrogen energy storage system with multi-energy coupling and cascaded energy release according to an exemplary embodiment of the present invention.

[0037] In the diagram: 100, hydrogen liquefaction system;

[0038] 1. Raw material hydrogen; 2. First precooling heat exchanger; 3. Second precooling heat exchanger; 4. Third precooling heat exchanger; 5. First cryogenic heat exchanger; 6. Low-temperature adsorber; 7. Second cryogenic heat exchanger; 8. Third cryogenic heat exchanger; 9. Fourth cryogenic heat exchanger; 10. Fifth cryogenic heat exchanger; 11. Final stage throttling valve for raw material hydrogen; 12. Low-pressure cryogenic refrigerant compressor; 13. Medium-pressure cryogenic refrigerant compressor; 14. Mixed precoolant compressor; 15. Mixed precoolant balance tank; 16. First-stage refrigeration throttling valve for mixed precoolant; 17. Flash evaporator after first-stage refrigeration of mixed precoolant; 18. Mixed precooler cryogenic separator; 19. Mixed precooler secondary refrigeration throttling valve; 20. Mixed precooler flash tank after secondary refrigeration; 21. Mixed precooler tertiary refrigeration throttling valve; 22. Mixed precooler flash tank after tertiary refrigeration; 23. Cryogenic refrigerant circulation primary turbine expander unit; 24. Cryogenic refrigerant circulation secondary turbine expander unit; 25. Cryogenic refrigerant circulation cooler; 26. Cryogenic refrigerant circulation cooler flash tank after flash tank; 27. Precooling cold box; 28. Cryogenic cold box; 29. ​​Cryogenic refrigerant; 30. Mixed precooler; 31. Continuous positive and negative hydrogen conversion.

[0039] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0041] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0042] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0043] Figure 1 This is a schematic diagram of a hydrogen liquefaction system 100 provided according to an exemplary embodiment of the present invention.

[0044] like Figure 1 As shown, the hydrogen liquefaction system 100 includes a mixed precooling agent precooling unit and a cryogenic refrigerant liquefaction unit. The mixed precooling agent precooling unit uses a mixed precooling agent 30 to cool the raw material hydrogen 1 to a preset temperature, such as 80K-100K, creating favorable conditions for the subsequent cryogenic liquefaction process. Then, combined with a helium reverse Brayton cycle or a hydrogen Claude cycle, the hydrogen is finally liquefied, with the temperature dropping to around 20K. This integrated approach fully leverages the advantages of different refrigeration technologies, increasing the overall system efficiency by 30%-40% compared to a single refrigeration technology, further reducing the energy consumption and cost of hydrogen liquefaction.

[0045] The following is in conjunction with the appendix Figure 1 The precooling unit with mixed precooling agent and the liquefaction unit with cryogenic refrigerant are described in detail.

[0046] like Figure 1 As shown, the mixed precooling unit includes a precooling box 27, a precooling heat exchanger unit, and a mixed precooling compressor unit. The main function of the mixed precooling agent 30 in the process cycle is to generate the cooling capacity required for the hydrogen liquefaction precooling stage. After the raw material hydrogen 1 enters the precooling heat exchanger unit, it is cooled to a preset temperature by the mixed precooling agent 30 provided by the mixed precooling compressor unit. The preset temperature range is 80K to 120K; preferably 85K to 95K; more preferably 90K.

[0047] In some embodiments, the mixed precooling agent 30 includes a first component, a second component, a third component, a fourth component, and a fifth component. The first component is, for example, nitrogen or a mixture of nitrogen and neon / argon; the second component is methane; the third component is ethane; the fourth component is propane; and the fifth component is n-butane, isobutane, n-pentane, or isopentane, preferably isopentane. The molar fraction of the first component is 0% to 30%; the molar fraction of the second component is 0% to 50%; the molar fraction of the third component is 0% to 30%; the molar fraction of the fourth component is 0% to 30%; and the molar fraction of the fifth component is 0% to 30%.

[0048] In the above scheme, the mixed precooling agent 30 is composed of various components with different boiling points, ranging from high-boiling-point propane and isopentane to low-boiling-point nitrogen and methane, covering a wide temperature range from room temperature to below -180°C during evaporation. Throughout the hydrogen liquefaction process, each component functions sequentially according to temperature requirements, absorbing heat from the hydrogen in stages, effectively reducing the temperature difference during heat exchange and minimizing irreversible thermodynamic losses. For example, in the initial stage, the high-boiling-point components evaporate and absorb heat first; as the temperature decreases, the low-boiling-point components take over sequentially, achieving gradual cooling of the hydrogen. Compared to traditional technologies, energy consumption can be significantly reduced for the same hydrogen liquefaction scale.

[0049] Furthermore, by precisely optimizing the proportions of each component in the mixed refrigerant, its phase change curve closely matches the hydrogen cooling curve. During heat exchange, the mixed refrigerant maintains a temperature close to that of hydrogen, avoiding waste of cooling capacity due to temperature mismatch. For example, at different stages of hydrogen cooling, the corresponding components of the mixed refrigerant evaporate and absorb heat in a timely manner, ensuring efficient energy utilization. This allows the energy consumption of the entire hydrogen liquefaction system to be reduced to below 10 kWh / kg LH2, significantly reducing energy consumption and improving energy efficiency.

[0050] Furthermore, the present invention limits the mixed precooling agent 30 to exclude ethylene and propylene, which can avoid the occurrence of low-temperature freezing blockage.

[0051] Furthermore, the precooling heat exchanger unit includes a first precooling heat exchanger 2, a second precooling heat exchanger 3, and a third precooling heat exchanger 4, and the mixed precooling compressor unit includes a mixed precooling compressor 14, a mixed precooling balance tank 15, a mixed precooling primary refrigeration throttling valve 16, a mixed precooling primary refrigeration flash tank 17, a mixed precooling low-temperature separation tank 18, a mixed precooling secondary refrigeration throttling valve 19, a mixed precooling secondary refrigeration flash tank 20, a mixed precooling tertiary refrigeration throttling valve 21, and a mixed precooling tertiary refrigeration flash tank 22. The first precooling heat exchanger 2, the second precooling heat exchanger 3, and the third precooling heat exchanger 4 are disposed in the precooling cold box 27. The mixed precooling agent primary refrigeration throttling valve 16, the mixed precooling agent primary refrigeration flash evaporator 17, the mixed precooling agent low-temperature separation tank 18, the mixed precooling agent secondary refrigeration throttling valve 19, the mixed precooling agent secondary refrigeration flash evaporator 20, the mixed precooling agent tertiary refrigeration throttling valve 21, and the mixed precooling agent tertiary refrigeration flash evaporator 22 are disposed in the precooling cold box 27. The mixed precooling agent compressor 14 and the mixed precooling agent balance tank 15 are disposed outside the precooling cold box 27.

[0052] At room temperature and pressure, raw material hydrogen 1 passes sequentially through the first precooling heat exchanger 2, the second precooling heat exchanger 3, and the third precooling heat exchanger 4. Mixed precooling agent 30, after being compressed by the mixed precooling agent compressor 14, enters the mixed precooling agent balance tank 15, forming high-pressure gaseous refrigerant and high-pressure liquid refrigerant. The high-pressure liquid refrigerant enters the first precooling heat exchanger 2, is throttled and cooled by the mixed precooling agent primary refrigeration throttling valve 16, and then enters the mixed precooling agent primary refrigeration flash tank 17, where it mixes with the refrigerant returning from the mixed precooling agent secondary refrigeration flash tank 20. After being reheated, it returns to the first precooling heat exchanger 2 and enters the inlet of the mixed precooling agent compressor 14, completing the cycle. The high-pressure gaseous refrigerant enters the first precooling heat exchanger 2... After passing through the second precooling heat exchanger 3, the mixture enters the low-temperature separation tank 18 of the mixed precooling agent to form a liquid phase and a gas phase. The liquid phase is throttled and cooled by the second-stage refrigeration throttling valve 19 of the mixed precooling agent, and then enters the flash evaporator 20 of the second-stage refrigeration of the mixed precooling agent. It mixes with the refrigerant returned from the third-stage refrigeration flash evaporator 22 of the mixed precooling agent and returns to the third precooling heat exchanger 4 and the second precooling heat exchanger 3 to be reheated before entering the flash evaporator 17 of the first-stage refrigeration of the mixed precooling agent. The gas phase is cooled by the third precooling heat exchanger 4, throttled and cooled by the third-stage refrigeration throttling valve 21 of the mixed precooling agent, and then enters the flash evaporator 22 of the third-stage refrigeration of the mixed precooling agent. After being reheated by the third precooling heat exchanger, it enters the flash evaporator 20 of the second-stage refrigeration of the mixed precooling agent.

[0053] The cryogenic refrigerant liquefaction unit includes a cryogenic cold box 28, a cryogenic heat exchanger unit, a cryogenic refrigerant compressor unit, and a final-stage throttling valve 11 for the raw material hydrogen path. The main function of the process cycle of the cryogenic refrigerant 29 is to generate the cooling capacity required for hydrogen liquefaction, achieving the final liquefaction of hydrogen at a temperature of around 20K. It is a closed loop, independent of the raw material hydrogen path to be liquefied.

[0054] In some embodiments, the cryogenic refrigerant 29 comprises hydrogen or a mixture of two or three of hydrogen, helium, and neon.

[0055] Traditional liquid nitrogen precooling technology heavily relies on an external liquid nitrogen supply, resulting in high energy consumption in liquid nitrogen production and supply stability that is greatly affected by external factors. The mixed refrigerant system in the above-described solution of this invention employs a closed-loop, self-sufficient system, eliminating reliance on an external liquid nitrogen supply. This reduces supply chain complexity and uncertainty, and improves the independence and stability of the hydrogen liquefaction system 100. Even in regions where liquid nitrogen supply is difficult, the normal operation of the hydrogen liquefaction unit can be ensured.

[0056] Furthermore, the cryogenic heat exchange unit includes a low-temperature adsorber 6, a first cryogenic heat exchanger 5, a second cryogenic heat exchanger 7, a third cryogenic heat exchanger 8, a fourth cryogenic heat exchanger 9, and a fifth cryogenic heat exchanger 10; the cryogenic refrigerant compressor unit includes a cryogenic refrigerant low-pressure compressor 12, a cryogenic refrigerant medium-pressure compressor 13, a cryogenic refrigerant circulation first-stage turbine expander unit 23, a cryogenic refrigerant circulation second-stage turbine expander unit 24, a cryogenic refrigerant circulation cooler 25, and a flash tank 26 after the cryogenic refrigerant circulation cooler.

[0057] The cryogenic adsorber 6, the first cryogenic heat exchanger 5, the second cryogenic heat exchanger 7, the third cryogenic heat exchanger 8, the fourth cryogenic heat exchanger 9, and the fifth cryogenic heat exchanger 10 are disposed in the cryogenic cold box 28; the cryogenic refrigerant circulation first-stage turboexpander unit 23, the cryogenic refrigerant circulation second-stage turboexpander unit 24, the cryogenic refrigerant circulation cooler, and the flash tank after the cryogenic refrigerant circulation cooler are disposed in the cryogenic cold box 28; and the cryogenic refrigerant low-pressure compressor 12 and the cryogenic refrigerant medium-pressure compressor 13 are disposed outside the cryogenic cold box 28.

[0058] The raw material hydrogen 1, cooled in the pre-cooling cold box 27, enters the cryogenic cold box 28 and passes sequentially through the first cryogenic heat exchanger 5, the low-temperature adsorber 6, the second cryogenic heat exchanger 7, the third cryogenic heat exchanger 8, the fourth cryogenic heat exchanger 9, the fifth cryogenic heat exchanger 10, and the final stage throttle valve 11 of the raw material hydrogen path.

[0059] After being compressed by the cryogenic refrigerant medium-pressure compressor 13, the cryogenic refrigerant 29 passes sequentially through the first precooling heat exchanger 2, the second precooling heat exchanger 3, and the third precooling heat exchanger 4 in the precooling cold box 27. It is cooled by the returned cold low-pressure cryogenic refrigerant, medium-pressure cryogenic refrigerant, and mixed precooling agent 30. The cooled cryogenic refrigerant is split into two paths through the first cryogenic heat exchanger 5. One path enters the cryogenic refrigerant circulation first-stage turbine expander 23 for expansion and then returns to the medium-pressure cryogenic refrigerant channel in the second cryogenic heat exchanger 7. The other path is split into two paths again through the second cryogenic heat exchanger 7. One path enters the cryogenic refrigerant circulation second-stage turbine expander 24 for expansion and then returns to the medium-pressure cryogenic refrigerant channel in the third cryogenic heat exchanger 8. The other path passes through the third cryogenic heat exchanger 8 and is cooled by the cryogenic refrigerant circulation cooler 25.

[0060] The medium-pressure cryogenic refrigerant from the third cryogenic heat exchanger 8 and the second cryogenic heat exchanger 7 enters the pre-cooling cold box 27 after passing through the first cryogenic heat exchanger 5, and then flows out of the pre-cooling cold box 27 after being reheated by passing through the third pre-cooling heat exchanger 4, the second pre-cooling heat exchanger 3, and the first pre-cooling heat exchanger 2 in sequence, and enters the inlet of the cryogenic refrigerant medium-pressure compressor 13 to complete the cycle.

[0061] The hydrogen, after being refrigerated and throttled by the cryogenic refrigerant circulating cooler 25, becomes a low-pressure cryogenic refrigerant. This low-pressure cryogenic refrigerant enters the flash tank 26 after the cryogenic refrigerant circulating cooler. The gaseous phase of this gaseous phase passes sequentially through the fourth cryogenic heat exchanger 9, the third cryogenic heat exchanger 8, the second cryogenic heat exchanger 7, and the first cryogenic heat exchanger 5 before entering the pre-cooling cold box 27. It then passes sequentially through the third pre-cooling heat exchanger 4, the second pre-cooling heat exchanger 3, and the first pre-cooling heat exchanger 2 for rewarming before exiting the pre-cooling cold box 27 and entering the inlet of the cryogenic refrigerant low-pressure compressor 12. The hydrogen gas exiting the cryogenic refrigerant low-pressure compressor 12 is a medium-pressure cryogenic refrigerant. It merges with the returning medium-pressure cryogenic refrigerant and enters the inlet of the cryogenic refrigerant medium-pressure compressor 13. The liquid phase of this gaseous phase returns to the fifth cryogenic heat exchanger 10 and the fourth cryogenic heat exchanger 9, where it merges with the gaseous phase.

[0062] In some embodiments, the cryogenic refrigerant cycle primary turbine expander unit 23 and the cryogenic refrigerant cycle secondary turbine expander unit 24 are arranged in a multi-stage series, multi-stage parallel, or multi-stage series-parallel configuration.

[0063] The cryogenic refrigerant circulating cooler 25 employs a cryogenic refrigerant circulating throttle valve or a cryogenic refrigerant turbine expander.

[0064] The following reference Figure 1 Describe the hydrogen liquefaction process principle of the hydrogen liquefaction system 100.

[0065] like Figure 1As shown, ambient temperature and pressurized raw material hydrogen 1 enters the inlet of the precooling box 27 of the mixed precooling unit. At this time, the hydrogen temperature is approximately the ambient temperature, generally 20-30℃. It passes through the first precooling heat exchanger 2, the second precooling heat exchanger 3, and the third precooling heat exchanger 4 in stages. The high-boiling-point component, medium-boiling-point component, and low-boiling-point component of the mixed precooling agent 30 pass through the first-stage refrigeration throttling valve 16, the second-stage refrigeration throttling valve 19, and the third-stage refrigeration throttling valve 21 of the mixed precooling agent in stages. After being refrigerated, they exchange heat in these heat exchangers, absorbing the heat of the hydrogen and reducing the hydrogen temperature to a certain level, such as 80-120K. After heat exchange, the cryogenic feedstock hydrogen 1 enters the cryogenic chamber 28, passing through the first cryogenic heat exchanger 5, the cryogenic adsorber 6, the second cryogenic heat exchanger 7, the third cryogenic heat exchanger 8, the fourth cryogenic heat exchanger 9, the fifth cryogenic heat exchanger 10, and the final stage throttling valve 11 of the feedstock hydrogen path. It then undergoes continuous secondary hydrogen conversion 31, reducing its temperature to approximately 20K (the critical temperature of hydrogen, especially below 24K, more preferably below 21.5K), achieving a secondary hydrogen content of ≥95%, and finally becoming qualified liquid hydrogen that flows out of the cryogenic chamber 28. During this process, the cryogenic refrigerant 29, at low temperature, provides cooling for the hydrogen by passing through the cryogenic refrigerant circulation primary turbine expander 23, the cryogenic refrigerant circulation secondary turbine expander 24, and the cryogenic refrigerant circulation throttling valve 25.

[0066] It should be noted that the aforementioned continuous ortho- and para-hydrogen conversion 31 is achieved by loading ortho- and para-hydrogen catalysts into the second cryogenic heat exchanger 7, the third cryogenic heat exchanger 8, the fourth cryogenic heat exchanger 9, and the fifth cryogenic heat exchanger 10. The continuous ortho- and para-hydrogen conversion 31 can also take the form of adiabatic or isothermal ortho- and para-hydrogen conversion. The ortho- and para-hydrogen catalyst is used to catalyze the conversion of ortho-hydrogen to para-hydrogen, and is preferably hydrated iron oxide.

[0067] Furthermore, the devices described above in this invention can be constructed using structures commonly used in the field that can achieve the above functions, and will not be elaborated upon here.

[0068] The hydrogen liquefaction system 100 of the present invention has many significant beneficial effects:

[0069] (I) Significantly reduce energy consumption

[0070] 1. Advantages of Synergistic Cooling with Multiple Components: Traditional liquid nitrogen precooling technology uses a single cryogenic medium, which is difficult to precisely match the wide temperature range cooling requirements of hydrogen, resulting in large temperature gradients and irreversible losses. In contrast, the mixed refrigerant of this invention consists of multiple components with different boiling points, ranging from high-boiling-point propane and isopentane to low-boiling-point nitrogen and methane, covering a wide temperature range from room temperature to below -180°C during evaporation. Throughout the hydrogen liquefaction process, each component functions sequentially according to temperature requirements, absorbing heat from the hydrogen in stages, effectively reducing the temperature difference during heat exchange and minimizing thermodynamic irreversible losses. Compared to traditional technologies, energy consumption can be significantly reduced for the same hydrogen liquefaction scale.

[0071] 2. Highly Efficient Matching of Hydrogen Cooling Curve: By precisely optimizing the proportions of each component in the mixed refrigerant, its phase change curve closely matches the hydrogen cooling curve. During heat exchange, the mixed refrigerant maintains a similar temperature to the hydrogen, avoiding wasted cooling capacity due to temperature mismatch. For example, at different stages of hydrogen cooling, the corresponding components of the mixed refrigerant evaporate and absorb heat in a timely manner, ensuring efficient energy utilization. This allows the energy consumption of the entire hydrogen liquefaction system to be reduced to below 10 kWh / kg LH2, significantly reducing energy consumption and improving energy efficiency.

[0072] (II) Improving liquefaction efficiency

[0073] 1. Wide Temperature Range Coverage: The staged evaporation characteristics of different boiling point components in the mixed refrigerant can simultaneously provide cooling capacity across multiple temperature ranges. During hydrogen liquefaction, hydrogen gas can be rapidly cooled in each stage of the heat exchanger, accelerating the phase change process from gaseous to liquid. For example, in the first-stage heat exchanger, the high-boiling-point component rapidly absorbs the initial heat from the hydrogen gas, causing its temperature to drop rapidly. Subsequently, the medium and low-boiling-point components take turns cooling, effectively shortening the time required for hydrogen liquefaction. Compared to traditional technologies, this significantly increases the hydrogen liquefaction yield per unit time.

[0074] 2. Phase Change Heat Transfer Optimization: The temperature glide characteristics of the mixed refrigerant during evaporation allow for better matching with the temperature changes of hydrogen. Traditional refrigerant isothermal phase change processes differ significantly from the hydrogen cooling curve, resulting in large heat exchange temperature differences and low thermal efficiency. This invention utilizes the temperature glide of the mixed refrigerant to make the heat exchange process closer to an ideal reversible process, reducing heat transfer losses due to temperature differences and further improving thermal efficiency, thereby enhancing hydrogen liquefaction efficiency.

[0075] (III) Reducing the cost of hydrogen liquefaction

[0076] 1. Reduced operating costs: The significant reduction in energy consumption directly decreases the energy costs, such as electricity, in the hydrogen liquefaction process. Furthermore, because this technology employs a closed-loop refrigeration cycle, it eliminates the need for continuous liquid nitrogen consumption as in traditional liquid nitrogen precooling, thus avoiding costs associated with liquid nitrogen procurement and transportation. In addition, improved system stability reduces the probability of equipment failure and lowers maintenance costs. All these factors combined significantly reduce the operating costs of hydrogen liquefaction.

[0077] 2. Significant Economic Advantages at Scale: In large-scale liquefaction plants with a daily output of 30 tons or more, the cost advantage of this mixed refrigerant technology becomes more pronounced as production scales up. The unit liquefaction cost can be reduced to 60%–70% of that of traditional methods, making liquid hydrogen more price-competitive in the market, bringing greater profit margins to the liquid hydrogen technology industry chain, and strongly promoting the commercial application of liquid hydrogen.

[0078] (iv) Advantages of technology integration

[0079] 1. Highly efficient synergy with helium or hydrogen refrigeration systems: This hybrid refrigerant precooling system acts as the front end, precooling hydrogen to 80–100K, creating favorable conditions for subsequent deep cryogenic liquefaction of helium or hydrogen to 20K. This integrated approach fully leverages the advantages of different refrigeration technologies, improving overall system efficiency by 30%–40% compared to a single refrigeration technology. It not only enhances hydrogen liquefaction efficiency but also reduces dependence on a single refrigeration technology, strengthening the system's reliability and adaptability.

[0080] 2. Adaptability to Future Technological Upgrades: This invention has good compatibility and can be combined with new materials (such as high-temperature superconducting magnets) or advanced expander technology. With the continuous development and progress of related technologies, it can further explore the potential for improving system performance, continuously optimize the hydrogen liquefaction process, maintain technological advancement, and meet the future demands of the hydrogen energy industry for higher efficiency and lower costs.

[0081] (V) Overcoming the bottlenecks of traditional technologies

[0082] Avoiding dependence on liquid nitrogen: Traditional liquid nitrogen precooling technology heavily relies on external liquid nitrogen supply, which is energy-intensive and its supply stability is greatly affected by external factors. This hybrid refrigerant system adopts a closed-loop, self-sufficient system, eliminating reliance on external liquid nitrogen supply. This reduces supply chain complexity and uncertainty, and improves the independence and stability of the hydrogen liquefaction unit. Even in regions where liquid nitrogen supply is difficult, the normal operation of the hydrogen liquefaction unit can be ensured.

[0083] In summary, the hydrogen liquefaction system 100 of the present invention brings comprehensive improvements in energy consumption, cost, efficiency and technical adaptability, and is of great significance to promoting the healthy development of my country's hydrogen energy industry.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A mixed precooling agent precooling unit for a hydrogen liquefaction system, characterized in that, It includes a precooling heat exchanger unit and a mixed precooling agent compressor unit. After the raw material hydrogen enters the precooling heat exchanger unit, it is cooled to a preset temperature by the mixed precooling agent provided by the mixed precooling agent compressor unit. The precooling heat exchanger unit includes a first precooling heat exchanger, a second precooling heat exchanger, and a third precooling heat exchanger. The mixed precooling compressor unit includes a mixed precooling compressor, a mixed precooling balance tank, a mixed precooling primary refrigeration throttling valve, a mixed precooling primary refrigeration flash tank, a mixed precooling low-temperature separation tank, a mixed precooling secondary refrigeration throttling valve, a mixed precooling secondary refrigeration flash tank, a mixed precooling tertiary refrigeration throttling valve, and a mixed precooling tertiary refrigeration flash tank. The raw material hydrogen gas sequentially passes through the first precooling heat exchanger, the second precooling heat exchanger, and the third precooling heat exchanger. The mixed precooling agent, after being compressed by the mixed precooling agent compressor, enters the mixed precooling agent balance tank, forming high-pressure gaseous refrigerant and high-pressure liquid refrigerant. The high-pressure liquid refrigerant enters the first precooling heat exchanger, where it is throttled and cooled by the first-stage refrigeration throttling valve of the mixed precooling agent. It then enters the flash tank after the first-stage refrigeration of the mixed precooling agent, mixes with the refrigerant returned from the flash tank after the second-stage refrigeration of the mixed precooling agent, and returns to the first precooling heat exchanger for reheating before entering the inlet of the mixed precooling agent compressor, completing the cycle. The high-pressure gaseous refrigerant enters the first precooling heat exchanger and the second... After the precooling heat exchanger, the mixture enters the low-temperature separation tank of the mixed precooling agent to form a liquid phase and a gas phase. The liquid phase is throttled and cooled by the secondary refrigeration throttling valve of the mixed precooling agent, and then enters the flash tank after the secondary refrigeration of the mixed precooling agent. It mixes with the refrigerant returned from the flash tank after the tertiary refrigeration of the mixed precooling agent and returns to the flash tank after the primary refrigeration of the mixed precooling agent. After being reheated by the third and second precooling heat exchangers, it enters the flash tank after the primary refrigeration of the mixed precooling agent. The gas phase is cooled by the third precooling heat exchanger and then throttled and cooled by the tertiary refrigeration throttling valve of the mixed precooling agent. It then enters the flash tank after the tertiary refrigeration of the mixed precooling agent, and after being reheated by the third precooling heat exchanger, it enters the flash tank after the secondary refrigeration of the mixed precooling agent.

2. The mixed precooling agent precooling unit of the hydrogen liquefaction system according to claim 1, characterized in that, in, The mixed precooling agent includes nitrogen, methane, ethane, propane, and isopentane, with molar fractions of 0%–30%, 0%–50%, 0%–30%, 0%–30%, and 0%–30%, respectively.

3. The mixed precooling agent precooling unit of the hydrogen liquefaction system according to claim 1, characterized in that, The preset temperature range is from 80K to 120K; Preferably, the K value is between 85K and 95K. 90K is preferred.

4. The mixed precooling agent precooling unit of the hydrogen liquefaction system according to any one of claims 1 to 3, characterized in that, It also includes pre-cooled cold boxes; The first, second, and third precooling heat exchangers are disposed in the precooling box. The first-stage refrigeration throttling valve, the first-stage flash evaporator, the low-temperature separator, the second-stage refrigeration throttling valve, the third-stage refrigeration throttling valve, and the third-stage flash evaporator are disposed in the precooling box. The precooling compressor and the precooling balance tank are disposed outside the precooling box.

5. A hydrogen liquefaction system, characterized in that, Includes a precooling unit with a mixed precooling agent according to any one of claims 1 to 4.

6. The hydrogen liquefaction system according to claim 5, characterized in that, It also includes a cryogenic heat exchanger unit, a cryogenic refrigerant compressor unit, and a final-stage throttling valve for the raw material hydrogen path. After being cooled, the raw material hydrogen enters the cryogenic heat exchanger unit and is cooled by the cryogenic refrigerant in the cryogenic refrigerant compressor unit. After passing through the final-stage throttling valve for the raw material hydrogen path, it is converted into liquid hydrogen. The cryogenic heat exchange unit includes a low-temperature adsorber, a first cryogenic heat exchanger, a second cryogenic heat exchanger, a third cryogenic heat exchanger, a fourth cryogenic heat exchanger, and a fifth cryogenic heat exchanger. The cryogenic refrigerant compressor unit includes a cryogenic refrigerant low-pressure compressor, a cryogenic refrigerant medium-pressure compressor, a cryogenic refrigerant circulation primary turbine expander unit, a cryogenic refrigerant circulation secondary turbine expander unit, a cryogenic refrigerant circulation cooler, and a flash tank after the cryogenic refrigerant circulation cooler. The cooled raw material hydrogen gas sequentially passes through the first cryogenic heat exchanger, the low-temperature adsorber, the second cryogenic heat exchanger, the third cryogenic heat exchanger, the fourth cryogenic heat exchanger, and the fifth cryogenic heat exchanger. The cryogenic refrigerant, after being compressed by the cryogenic refrigerant medium-pressure compressor, sequentially passes through the first pre-cooling heat exchanger, the second pre-cooling heat exchanger, and the third pre-cooling heat exchanger, where it is cooled by the returned cold low-pressure cryogenic refrigerant, medium-pressure cryogenic refrigerant, and mixed pre-cooling agent. The cooled cryogenic refrigerant then splits into two paths after passing through the first cryogenic heat exchanger. One path enters the cryogenic refrigerant circulation stage one turbine expander unit and returns to the medium-pressure cryogenic refrigerant channel in the second cryogenic heat exchanger. The other path, after passing through the second cryogenic heat exchanger, splits again into two paths. One path enters the cryogenic refrigerant circulation stage two turbine expander unit and returns to the medium-pressure cryogenic refrigerant channel in the third cryogenic heat exchanger. The other path, after passing through the third cryogenic heat exchanger, is cooled by the cryogenic refrigerant circulation cooler. The medium-pressure cryogenic refrigerant in the third cryogenic heat exchanger and the second cryogenic heat exchanger passes through the first cryogenic heat exchanger, the third precooling heat exchanger, the second precooling heat exchanger, and the first precooling heat exchanger for reheating before entering the inlet of the medium-pressure cryogenic refrigerant compressor to complete the cycle. The hydrogen, after being refrigerated and throttled by the cryogenic refrigerant circulating cooler, becomes a low-pressure cryogenic refrigerant. This low-pressure cryogenic refrigerant enters the flash tank after the cryogenic refrigerant circulating cooler. The gaseous phase therein sequentially passes through the fourth cryogenic heat exchanger, the third cryogenic heat exchanger, the second cryogenic heat exchanger, the first cryogenic heat exchanger, the third precooling heat exchanger, the second precooling heat exchanger, and the first precooling heat exchanger before being reheated and entering the inlet of the low-pressure cryogenic refrigerant compressor. The hydrogen gas at the outlet of the low-pressure cryogenic refrigerant compressor, which is a medium-pressure cryogenic refrigerant, merges with the returning medium-pressure cryogenic refrigerant and enters the inlet of the medium-pressure cryogenic refrigerant compressor. The liquid phase therein returns to the fifth and fourth cryogenic heat exchangers and then merges with the gaseous phase therein.

7. The hydrogen liquefaction system according to claim 6, characterized in that, This also includes cryogenic cold boxes; The cryogenic adsorber, the first cryogenic heat exchanger, the second cryogenic heat exchanger, the third cryogenic heat exchanger, the fourth cryogenic heat exchanger, and the fifth cryogenic heat exchanger are disposed in the cryogenic cold box. The cryogenic refrigerant circulation primary turbine expander, the cryogenic refrigerant circulation secondary turbine expander, the cryogenic refrigerant circulation cooler, and the flash tank after the cryogenic refrigerant circulation cooler are installed in the cryogenic cold box, while the cryogenic refrigerant low-pressure compressor and the cryogenic refrigerant medium-pressure compressor are installed outside the cryogenic cold box.

8. The hydrogen liquefaction system according to claim 6, characterized in that, The cryogenic refrigerant cycle primary turbine expander and the cryogenic refrigerant cycle secondary turbine expander are connected in a multi-stage series, multi-stage parallel, or multi-stage series-parallel configuration.

9. The hydrogen liquefaction system according to claim 6, characterized in that, The cryogenic refrigerant circulating cooler employs a cryogenic refrigerant circulating throttle valve or a cryogenic refrigerant turbine expander.

10. The hydrogen liquefaction system according to any one of claims 6 to 9, characterized in that, The cryogenic refrigerant includes hydrogen or a mixture of two or three of hydrogen, helium, and neon.

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