Hydrogen low-temperature precooling device and method

Abstract

The invention provides a hydrogen low-temperature precooling device and method which are suitable for deep precooling treatment before hydrogen liquefaction in a liquid hydrogen preparation process. The device comprises a raw material hydrogen cooling and converting system, a mixed refrigerant refrigerating system and a nitrogen circulating refrigerating system, multi-stage heat exchange is achieved through a main heat exchanger and a subcooler, and efficient cooling capacity distribution is provided by adopting a multi-stage refrigerant separation and throttling path. After being cooled, the hydrogen sequentially passes through the low-temperature adsorber and the ortho-parahydrogen converter, so that precooled hydrogen of which the temperature and the molecular structure both meet the liquefaction requirements is obtained. The device supports structure optimization and module simplification, can adopt externally supplied liquid nitrogen as a cold source, and adapts to different pre-cooling scenes. According to the method, through a refrigerant multi-section throttling and reheating recovery mechanism and a nitrogen double-channel cooling mechanism, cooling capacity output and energy efficiency utilization are both considered, and the method has the advantages of being safe in operation, compact in structure, accurate in temperature control and the like.

Description

Technical Field

[0001] The present invention relates to the fields of low-temperature refrigeration and hydrogen liquefaction, and in particular to a device and method for low-temperature pre-cooling of hydrogen. Background Art

[0002] Hydrogen is an important carrier to replace traditional fossil energy. However, its low density makes it difficult to transport. The density of liquid hydrogen at atmospheric pressure is 70kg / m³, several times that of high-pressure gaseous hydrogen. Therefore, liquid hydrogen has great advantages as a transport carrier, and its development is a future trend.

[0003] At present, hydrogen liquefaction is achieved by combining pre-cooling and deep low-temperature refrigeration. Most pre-cooling methods directly use liquid nitrogen pre-cooling or mixed refrigerant refrigeration cycle. Liquid nitrogen pre-cooling has problems such as poor matching of cold and hot streams, high energy consumption, and large liquid nitrogen consumption. Mixed refrigerant refrigeration cycle has problems such as complex mixed refrigerant components, difficulty in adjusting the ratio, freezing and blockage, and high energy consumption.

[0004] Chinese patent publication number CN115682628A discloses a hydrogen liquefaction system and process based on mixed refrigerant pre-cooling. It uses a mixed refrigerant composed of six components, including methane, ethane, propane, isobutane, nitrogen, and hydrogen, to provide cooling capacity above 80K (-193.15°C). The mixed refrigerant undergoes only one stage of condensation separation and the separation temperature reaches 25°C. At the same time, in order to improve efficiency, a two-phase expander is used instead of a throttle valve. The patent has the problems of complex mixed refrigerant ratio, difficult operation, no low-temperature condensation separation, resulting in low-temperature freezing of isobutane at -193.15℃, and the two-phase expander is difficult to manufacture and has low safety. The Chinese patent with publication number CN114543441A discloses a hydrogen liquefaction system and method with helium expansion combined with mixed refrigerant refrigeration, which uses a mixed refrigerant composed of five components similar to nitrogen, methane, ethylene, propane, and isopentane in the natural gas liquefaction process. The patent does not optimize the refrigerant ratio for the hydrogen liquefaction device, and does not specify the pre-cooling temperature of the mixed refrigerant, but the mixed The optimal temperature for the refrigeration process is between -150°C and -163°C, which doesn't match the pre-cooling temperature required for hydrogen liquefaction (-183°C to -193°C). Chinese patent publication number CN113446815B discloses a hydrogen liquefaction device and method using mixed refrigeration. This device utilizes a mixed refrigerant process and a nitrogen cycle refrigeration process for pre-cooling. The mixed refrigerant is a similar mixture of nitrogen, methane, ethylene, propane, and isopentane used in natural gas liquefaction. The pre-cooling temperature is 113K (-160°C), and the nitrogen refrigeration cycle provides 80K (-193.15°C) of cooling capacity. This patent fails to optimize the refrigerant composition for the hydrogen liquefaction unit, making the mixing process more complex. Furthermore, the pre-cooling temperature and process for the mixed refrigerant are not optimized. While this solves the problem of heavy component freezing and blockage, the higher pre-cooling temperature results in excessively high nitrogen cycle pressure, leading to higher energy consumption. Summary of the Invention

[0005] The object of the present invention is to provide a device and method for low-temperature precooling of hydrogen to solve the problems existing in the prior art.

[0006] The present invention is implemented by adopting the following technical solutions: a device for low-temperature precooling of hydrogen, characterized in that it includes a main heat exchanger, which is provided with multiple heat exchange channels, the first channel inlet of which is connected to the hydrogen raw material pipeline, and the outlet is connected to the first channel inlet of the subcooler, forming a preliminary heat exchange path for hydrogen; the first channel outlet of the subcooler is connected to a low-temperature adsorber and a normal-para hydrogen converter in sequence, and the outlet of the normal-para hydrogen converter is connected to the second channel inlet of the subcooler, forming a closed-loop path for hydrogen precooling and molecular conversion; a mixed refrigerant refrigeration system, comprising a mixed refrigerant compressor, a mixed refrigerant cooler, a mixed refrigerant final-stage separation tank, a mixed refrigerant medium-pressure separation tank and a mixed refrigerant low-pressure separation tank, wherein: the outlet of the mixed refrigerant compressor is connected to the cooler inlet, and one end of the cooler outlet is connected to the inlet of the mixed refrigerant final-stage separation tank; the liquid phase outlet of the mixed refrigerant final-stage separation tank is connected to the second channel of the main heat exchanger, and the second channel is connected to the seventh channel through valve 1; the mixed refrigerant final-stage separation tank is connected to the liquid phase outlet of the mixed refrigerant final-stage separation tank. The gas phase outlet of the separation tank is connected to the third channel of the main heat exchanger, and the third channel is connected to the inlet of the mixed refrigerant medium-pressure separation tank; the liquid phase outlet of the mixed refrigerant medium-pressure separation tank is connected in sequence to the sixth channel of the main heat exchanger, valve two, and the mixed refrigerant low-pressure separation tank; the gas phase outlet of the mixed refrigerant medium-pressure separation tank is connected to the fifth channel of the main heat exchanger and connected to the seventh channel through valve three; the liquid phase and gas phase outlets of the mixed refrigerant low-pressure separation tank merge and are connected to the eighth channel of the main heat exchanger, and the outlet of the eighth channel is connected to the inlet of the compressor, forming a closed-loop circulation path for the mixed refrigerant; the nitrogen circulation system includes a nitrogen compressor, a nitrogen cooler and a liquid nitrogen separation tank, the compressor outlet is connected to the nitrogen cooler and the fourth channel of the main heat exchanger in sequence; the third channel outlet of the subcooler is connected to the inlet of the liquid nitrogen separation tank through valve four, the liquid phase outlet of the liquid nitrogen separation tank is connected to the fourth channel of the subcooler, and the gas phase outlet is connected to the ninth channel of the main heat exchanger, forming a nitrogen refrigeration and reheating path. It realizes multi-stage deep cooling of hydrogen, deep removal of impurities and molecular structure transformation. At the same time, through multi-stage separation and throttling of mixed refrigerants, nitrogen liquefaction and reheating, it provides efficient and precise matching of cold supply in different temperature zones, and realizes effective recovery of cold, providing pre-cooled hydrogen with qualified temperature and molecular structure for subsequent hydrogen liquefaction.

[0007] Furthermore, each separation tank in the mixed refrigerant system is provided with an independent heat exchange branch, which is respectively connected to different temperature zone channels of the main heat exchanger. The liquid-phase refrigerant in the final separation tank of the mixed refrigerant is cooled through the second channel, and after throttling by valve one, it supplies low-temperature cooling capacity at the upper part of the eighth channel. The low-pressure separation tank of the mixed refrigerant supplies the middle cooling capacity through the lower part of the eighth channel. The gas-phase refrigerant in the medium-pressure separation tank of the mixed refrigerant is cooled through the fifth channel, and after throttling by valve three, it provides terminal cooling capacity through the seventh channel.

[0008] Furthermore, the cryogenic adsorber and the para-hydrogen converter are sequentially connected after the subcooler. After heating through the corresponding steps, they are then cooled to the corresponding temperature through the subcooler, forming a functional module for impurity removal and molecular conversion. This layout optimizes the process sequence, ensuring that the hydrogen gas undergoes deep impurity removal after reaching a relatively low temperature, followed by the para-hydrogen conversion at low temperatures. The converted hydrogen gas returns to the subcooler for final cooling, ensuring that the output pre-cooled hydrogen meets both the extremely low temperature requirements and the molecular structure requirements of para-hydrogen, laying the foundation for subsequent efficient and stable liquefaction.

[0009] Furthermore, in the main heat exchanger, the heat exchange channels for hydrogen, mixed refrigerant, and nitrogen are distributed along the hydrogen flow path from high-temperature zones to low-temperature zones, with the flows arranged in opposite directions to form a countercurrent heat exchange structure. This countercurrent heat exchange structure maximizes the average heat transfer temperature difference between the hot and cold streams, significantly improving heat exchange efficiency and reducing heat transfer area requirements and irreversible losses. The temperatures of the hot and cold fluids gradually approach each other as the flow progresses, achieving a smaller heat transfer temperature difference in the most critical low-temperature zone, significantly reducing the system's total power consumption and improving energy efficiency.

[0010] Furthermore, the mixed refrigerant refrigeration system eliminates the final mixed refrigerant separation tank and its corresponding second channel of the main heat exchanger. Instead, the mixed refrigerant compressor connects directly to the mixed refrigerant intermediate-pressure separation tank after passing through the mixed refrigerant cooler. This simplified solution eliminates the primary low-temperature separation stage, reducing device complexity and manufacturing costs, reducing valves and control points, and improving system reliability and ease of operation. While it may compromise on the most efficient cooling capacity, it can still provide satisfactory pre-cooling results in applications with higher cost and compactness requirements, demonstrating excellent adaptability and cost-effectiveness.

[0011] Furthermore, the nitrogen circulation refrigeration system eliminates the cooling path of nitrogen through the fourth channel of the main heat exchanger and the third channel of the subcooler, and instead uses externally supplied liquid nitrogen. After throttling, the externally supplied liquid nitrogen enters the liquid nitrogen separation tank for gas-liquid separation. The liquid nitrogen is then connected to the fourth channel of the subcooler for cooling. This solution completely avoids the compression work required to liquefy nitrogen in the system and the complex liquefaction heat exchange process, directly utilizing an external liquid nitrogen cooling source, significantly reducing system energy consumption. It simplifies the nitrogen circuit equipment and process, making the device more compact and suitable for applications with a stable and inexpensive external liquid nitrogen supply, with strong flexibility and fast startup.

[0012] Furthermore, the nitrogen output from the nitrogen compressor, after being cooled by the nitrogen cooler, is no longer returned to the nitrogen circulation system, but is instead consumed as a utility byproduct of the device. This solution outputs a portion of the compressed and pre-cooled nitrogen as a valuable byproduct for use in other processes. This effectively utilizes the system's compression work, improving overall resource utilization and economic efficiency, while still ensuring the nitrogen cooling capacity required for the main hydrogen pre-cooling process.

[0013] Furthermore, the nitrogen compressor and the mixed refrigerant compressor may be reciprocating, screw or centrifugal compressors.

[0014] Furthermore, the nitrogen cooler and mixed refrigerant cooler can be air cooling, water cooling, ammonia cooling, lithium bromide cooling, propane cooling, or a combination of two thereof; the main heat exchanger and subcooler can be coil heat exchangers, plate-fin heat exchangers, or printed circuit board heat exchangers.

[0015] A method for low-temperature precooling of hydrogen comprises the following steps: Hydrogen pre-cooling and conversion step: The raw hydrogen passes through the main heat exchanger, subcooler, low-temperature adsorber and normal-parahydrogen converter in sequence for heat exchange cooling, impurity removal and molecular structure conversion. The converted hydrogen returns to the subcooler for further cooling and is output as pre-cooled hydrogen that meets the temperature and structure requirements. Mixed refrigerant circulation cooling steps: After being compressed and cooled, the mixed refrigerant enters the mixed refrigerant final separation tank, the mixed refrigerant medium-pressure separation tank, and the mixed refrigerant low-pressure separation tank in sequence for multi-stage gas-liquid separation. Each separation product flows into different channels of the main heat exchanger, releases cold energy through throttling, is reheated in the main heat exchanger, and finally flows back to the compressor to form a closed-loop cooling supply; Nitrogen circulation cooling steps: After compression and cooling, nitrogen passes through the main heat exchanger and subcooler in sequence for liquefaction, throttling, and separation. The liquid nitrogen is supplied to the subcooler to provide cooling capacity, and the gaseous nitrogen is reheated through the main heat exchanger and returned to the compressor, forming a closed cycle path; Cold distribution and heat recovery steps: Different channels in the main heat exchanger are responsible for releasing cold in high, medium and low temperature zones respectively, forming a countercurrent heat exchange between hydrogen and the refrigerant, and completing heat recovery in the low temperature channel to achieve an efficient and energy-saving deep cold heat exchange process.

[0016] Furthermore, the raw hydrogen pressure is between 1 and 8 MPa or 20 and 30 MPa, and the purity is between 99.9% and 99.999%.

[0017] Furthermore, the operating temperature of the raw hydrogen after passing through the main heat exchanger is between -162 and -183°C, and the operating temperature of the raw hydrogen after passing through the subcooler is between -173 and -196°C.

[0018] Furthermore, the inlet and outlet operating pressures of the nitrogen compressor are between 0.1~0.76MPa and 1.6~6MPa respectively.

[0019] Furthermore, the inlet and outlet operating pressures of the mixed refrigerant compressor are between 0.15~0.6MPa and 1.5~5MPa respectively.

[0020] Furthermore, the operating temperature of the mixed refrigerant medium-pressure separation tank is between -10 and -100°C.

[0021] Furthermore, the mixed refrigerant is composed of at least four gases: methane, ethylene, nitrogen, and butane, with the volume fractions ranging from 25-35% methane, 20-40% ethylene, 10-20% nitrogen, and 25-40% butane. This specific ratio of the quaternary mixed refrigerant is relatively simple and flexible to adjust. Its optimized boiling point range effectively covers the medium and low temperature ranges required for hydrogen pre-cooling. While providing efficient cooling capacity, it avoids the operational difficulties of more complex ratios and significantly reduces the risk of freezing of heavy components in the deep cold zone, improving system operation safety.

[0022] The device and method for low-temperature precooling of hydrogen described in the present invention have the following beneficial effects: (1) The mixed refrigerant is a combination of methane, ethylene, nitrogen and butane. The four components are simpler, easier to adjust the ratio, and more operational.

[0023] (2) Optimize the mixed refrigerant pre-cooling temperature to reduce the total energy consumption of hydrogen pre-cooling and liquid nitrogen consumption.

[0024] (3) The mixed refrigerant refrigeration process sets a low-temperature separator with a temperature of -10~-100℃, which reduces energy consumption and avoids the problem of heavy hydrocarbon freezing and blocking at low temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. The drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0026] Figure 1 It is a schematic diagram of the present invention; Figure 2 This is a schematic diagram of a second embodiment of the present invention; In the figure, 101-nitrogen compressor, 102-mixed refrigerant compressor, 103-nitrogen cooler, 104-mixed refrigerant cooler, 105-main heat exchanger, 106-subcooler, 107-mixed refrigerant final stage separation tank, 108-mixed refrigerant medium-pressure separation tank, 109-mixed refrigerant low-pressure separation tank, 110-liquid nitrogen separation tank, 111-cryogenic adsorber, 112-normal-para-hydrogen converter, 113-valve one, 114-valve two, 115-valve three, 116-valve four. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention. Example 1

[0029] like Figure 1 As shown, this embodiment provides a device for low-temperature pre-cooling of hydrogen, which mainly includes: a main heat exchanger 105, a subcooler 106, a mixed refrigerant compressor 102, a mixed refrigerant cooler 104, a mixed refrigerant final-stage separation tank 107, a mixed refrigerant medium-pressure separation tank 108, a mixed refrigerant low-pressure separation tank 109, a nitrogen compressor 101, a nitrogen cooler 103, a liquid nitrogen separation tank 110, a low-temperature adsorber 111, a normal-para-hydrogen converter 112, and several throttle valves and connecting pipelines.

[0030] Specifically, the raw hydrogen first enters the first channel of the main heat exchanger 105 through a pipeline for initial heat exchange. After its temperature drops, it flows into the first channel of the subcooler 106 for deep cooling. The cooled hydrogen enters the cryogenic adsorber 111 to remove trace impurities (such as oxygen, nitrogen, and methane), and then flows into the normal-para-hydrogen converter 112 for molecular structure conversion. The converted hydrogen then returns to the second channel of the subcooler 106 for final cooling, ultimately being output as pre-cooled hydrogen that meets the pre-liquefaction requirements.

[0031] In the mixed refrigerant circulation system, the high-pressure gaseous mixed refrigerant output by the mixed refrigerant compressor 102 is cooled by the cooler 104 before entering the mixed refrigerant final-stage separation tank 107 for preliminary gas-liquid separation. The separated liquid refrigerant then flows through a pipeline into the second channel of the main heat exchanger 105 for cooling. After decompression by valve 113, it flows into the eighth channel of the main heat exchanger 105 as a gas-liquid mixed state, providing primary low-temperature cooling for the system.

[0032] Meanwhile, the gaseous refrigerant separated by the mixed refrigerant final-stage separator 107 enters the third channel of the main heat exchanger 105 for cooling before flowing into the mixed refrigerant intermediate-pressure separator 108 for a second gas-liquid separation. The intermediate-pressure liquid refrigerant enters the sixth channel of the main heat exchanger 105 for further heat exchange, then passes through valve 2 114 and is reduced in pressure before flowing into the mixed refrigerant low-pressure separator 109. The low-pressure liquid refrigerant, after exiting the mixed refrigerant low-pressure separator 109, again enters the eighth channel of the main heat exchanger 105 to provide cooling.

[0033] The gaseous refrigerant separated by the mixed refrigerant medium-pressure separator 108 enters the fifth channel of the main heat exchanger 105 for cooling, then passes through valve three 115 for pressure reduction and enters the seventh channel of the main heat exchanger 105 for heat exchange. The gaseous refrigerant separated by the mixed refrigerant low-pressure separator 109 merges with the liquid refrigerant and also enters the eighth channel of the main heat exchanger 105. After completing the reheating process, it returns to the mixed refrigerant compressor 102, forming a closed loop.

[0034] In the nitrogen circulation refrigeration system, high-pressure nitrogen output from nitrogen compressor 101 flows through pipelines into the fourth channel of main heat exchanger 105 and the third channel of subcooler 106, where it is cooled and liquefied. The liquefied nitrogen is throttled by valve 4 116 to form a gas-liquid mixture, which then enters liquid nitrogen separator 110 for gas-liquid separation. The separated liquid nitrogen flows through a pipeline into the fourth channel of subcooler 106, providing low-temperature cooling. The gaseous nitrogen then merges with the reheated nitrogen, reheats through the ninth channel of main heat exchanger 105, and returns to the inlet of compressor 101, completing the nitrogen cycle.

[0035] The mixed refrigerant used in this example consists of methane, ethylene, nitrogen, and butane, with their volume fractions controlled within the ranges of 25-35%, 20-40%, 10-20%, and 25-40%, respectively. This combination offers simple composition, flexible adjustment, and strong adaptability to cold zones. Specifically, the operating temperature range of the mixed refrigerant medium-pressure separator tank is set between -10°C and -100°C, effectively preventing freezing and blockage of heavy components such as butane, thereby improving system safety.

[0036] The device is equipped with a dual refrigerant system, multi-temperature zone distribution and heat recovery mechanism. It is suitable for the pre-liquefaction pre-cooling process of hydrogen with a purity of ≥99.9% and a pressure range of 1~30MPa. It has comprehensive advantages such as high energy efficiency, strong safety and strong adaptability. Example 2

[0037] like Figure 2 As shown, this embodiment is a simplified structural solution based on the first embodiment, and specifically includes a main heat exchanger 105, a subcooler 106, a mixed refrigerant compressor 102, a mixed refrigerant cooler 104, a mixed refrigerant medium-pressure separation tank 108, a mixed refrigerant low-pressure separation tank 109, a liquid nitrogen separation tank 110, a low-temperature adsorber 111, a normal-para-hydrogen converter 112, a nitrogen compressor 101, a nitrogen cooler 103, and a plurality of throttle valves.

[0038] The raw hydrogen first enters the first channel of the main heat exchanger 105 for preliminary heat exchange, then enters the first channel of the subcooler 106 for further deep cooling, and after the trace impurities are removed by the low-temperature adsorber 111, it enters the normal-para-hydrogen converter 112 to complete the normal-para-hydrogen conversion, and then refluxes to the second channel of the subcooler 106 for final cooling, and the output is pre-cooled hydrogen that meets the temperature and hydrogen isomer ratio requirements.

[0039] In this embodiment, the mixed refrigerant final stage separation tank 107 and its associated second channel of the main heat exchanger are eliminated.

[0040] After being compressed by compressor 102, the mixed refrigerant is cooled by cooler 104 and directly enters mixed refrigerant medium-pressure separator tank 108 for gas-liquid separation. The medium-pressure liquid refrigerant enters the fifth channel of main heat exchanger 105 for heat exchange, then is throttled by valve 2 114 and enters mixed refrigerant low-pressure separator tank 109 to continue releasing cooling energy. The medium-pressure vapor refrigerant enters the fourth channel of main heat exchanger 105 for heat exchange, then is throttled by valve 3 115 and enters the sixth channel for cooling output.

[0041] After the liquid phase separated from the mixed refrigerant low-pressure separation tank 109 merges with the gas phase mixed refrigerant, it enters the seventh channel of the main heat exchanger 105 to complete the reheating process, and finally flows back to the mixed refrigerant compressor 102 to form a closed loop circulation.

[0042] Different from the first embodiment, this embodiment eliminates the heat exchange path of nitrogen through the fourth channel of the main heat exchanger 105 and the third channel of the subcooler 106, and instead uses external liquid nitrogen to directly provide cooling capacity.

[0043] After throttling through the external liquid supply pipeline, the liquid nitrogen forms a gas-liquid mixture and enters the liquid nitrogen separator 110 for gas-liquid separation. The liquid nitrogen enters the fourth channel of the subcooler 106, providing low-temperature cooling support. The separated gaseous nitrogen merges with the nitrogen at the second outlet of the subcooler 106 and flows through the main pipe to the nitrogen compressor 101. After compression, it is cooled by the nitrogen cooler 103 and no longer recirculates in the system. Instead, it is directly delivered as finished cold nitrogen for external use.

[0044] This structure simplifies the heavy component path by eliminating the final separation tank and related channels of the mixed refrigerant, effectively reduces the number of control valves and throttling components, and reduces the difficulty of operation and management; at the same time, it uses external liquid nitrogen as the cold source, avoiding the large amount of energy consumption and equipment required for the self-circulating liquefaction and heat exchange path in the nitrogen system, further compressing the system volume.

[0045] It is particularly suitable for industrial hydrogen production scenarios with external liquid nitrogen supply, such as skid-mounted liquid hydrogen devices and remote site pre-cooling systems. It can significantly improve the device integration and operation and maintenance convenience, while ensuring system operation stability and energy economy. Example

[0046] This embodiment provides a method for low-temperature precooling of hydrogen, suitable for the deep precooling stage of the hydrogen liquefaction process. This method consists of four functional pathways: a cooling and conversion pathway for the raw hydrogen, a circulating cooling pathway for the mixed refrigerant, a circulating cooling pathway for nitrogen, and a pathway for cooling exchange and heat recovery between the various working fluids. These pathways work together synchronously and in parallel during system operation, forming a complete precooling process.

[0047] 1. Cooling and conversion path of raw hydrogen: The raw hydrogen enters the first channel of the main heat exchanger 105 through a pipeline, exchanges heat with the reflux refrigerant, and its temperature drops to between -162°C and -183°C. The hydrogen then flows into the first channel of the subcooler 106 for further cooling, with its temperature dropping to between -173°C and -196°C.

[0048] The cooled hydrogen enters cryogenic adsorber 111, where trace impurities (including oxygen, nitrogen, methane, and argon) are removed. It then flows into ortho-parahydrogen converter 112, where a catalytic reaction converts some orthohydrogen into parahydrogen, improving its low-temperature stability. The converted hydrogen then flows back to the second channel of subcooler 106 for a second cooling step, ultimately delivering pre-cooled hydrogen with a temperature and molecular structure that meet the requirements for subsequent liquefaction.

[0049] 2. Mixed refrigerant circulation cooling path: After being compressed in the compressor 102, the mixed refrigerant is cooled to the target temperature by the mixed refrigerant cooler 104 and then enters the separation and heat exchange system to achieve staged throttling and cooling release.

[0050] In the complete structure, the refrigerant first enters the mixed refrigerant final separation tank 107 for initial gas-liquid separation. The separated liquid refrigerant flows into the second channel of the main heat exchanger 105 for heat exchange. After throttling and pressure reduction through valve 113, the gas-liquid refrigerant flows into the seventh channel to provide low-temperature cooling.

[0051] The gas phase refrigerant enters the mixed refrigerant medium pressure separation tank 108 and is separated again. The separated medium pressure liquid phase refrigerant enters the fifth channel of the main heat exchanger 105 for heat exchange, and then flows into the mixed refrigerant low pressure separation tank 109 after throttling through valve 2 114 to release the cooling capacity of the third temperature zone.

[0052] The gaseous refrigerant separated by the mixed refrigerant medium-pressure separator 108 flows into the fourth channel of the main heat exchanger 105 for cooling. It is then throttled by valve three 115 and enters the sixth channel, releasing its cooling capacity and participating in heat exchange with other low-temperature refrigerant branches. The gaseous and liquid refrigerants separated by the mixed refrigerant low-pressure separator 109 are finally reheated in the seventh channel and returned to the compressor 102, forming a closed-loop operation.

[0053] In the simplified structure, the mixed refrigerant final separation tank 107 and the second channel of the main heat exchanger 105 are cancelled. After cooling, the mixed refrigerant directly enters the mixed refrigerant medium-pressure separation tank 108 as the grading starting point. The structure is more compact and convenient for modular integration.

[0054] 3. Nitrogen circulation cooling path: After being compressed to the target pressure by compressor 101, nitrogen is cooled by cooler 103. In the complete structure, it sequentially passes through the eighth channel of main heat exchanger 105 and the third channel of subcooler 106 for heat exchange. After cooling to the liquid nitrogen temperature range, it is throttled by valve 4 116 to form a gas-liquid mixed nitrogen, which enters liquid nitrogen separation tank 110 for gas-liquid separation. The liquid nitrogen is supplied to the fourth channel of subcooler 106 as a low-temperature cooling source. The gaseous nitrogen is reheated through the ninth channel of main heat exchanger 105 and returned to compressor 101, completing the closed loop.

[0055] In the simplified structure, nitrogen is no longer liquefied in the main heat exchanger 105 or the subcooler 106. Instead, external liquid nitrogen is directly used for cooling after throttling and separation. After compression, the nitrogen is cooled only in the cooler 103 and output as finished cold nitrogen.

[0056] 4. Cooling capacity distribution and heat recovery path: Through the multi-channel structure of the main heat exchanger 105, mixed refrigerants from different temperature zones achieve multi-stage cooling, from high pressure to low pressure. The flow of hydrogen, refrigerant, and nitrogen is set to countercurrent heat exchange to maximize heat exchange efficiency.

[0057] In the heat recovery path, all low-pressure refrigerants are returned to the compressor after being reheated in the seventh channel. The gaseous nitrogen separated in the liquid nitrogen path is returned to the nitrogen cycle after being reheated in the ninth channel, realizing residual cold recovery and energy efficiency utilization.

[0058] This method is suitable for pre-cooling liquid hydrogen with a purity between 99.9% and 99.999% and a pressure of 130 MPa. Through the coordinated control of a dual-circuit mixed refrigerant and nitrogen, it meets cryogenic cooling requirements in the -173°C to -196°C range. It is particularly well-suited for a variety of applications, including large-scale hydrogen production by water electrolysis, distributed liquid hydrogen storage and transportation, and skid-mounted process modules. Its secure structure, clear path, and precise temperature control meet the stability and energy efficiency requirements of industrial-grade continuous operation.

[0059] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Without departing from the spirit and scope of the present invention, modifications and variations made by those skilled in the art without departing from the spirit and scope of the present invention should be within the scope of protection of the appended claims.

Claims

1. A device for low-temperature precooling of hydrogen, characterized in that: The invention comprises a main heat exchanger (105) provided with a plurality of heat exchange channels, wherein the inlet of the first channel is connected to the hydrogen raw material pipeline, and the outlet is connected to the inlet of the first channel of the subcooler (106), forming a preliminary heat exchange path for hydrogen; the outlet of the first channel of the subcooler (106) is connected to the low-temperature adsorber (111) and the positive-parahydrogen converter (112) in sequence, and the outlet of the positive-parahydrogen converter (112) is connected to the inlet of the second channel of the subcooler (106), forming a hydrogen pre-cooling and molecular conversion closed-loop path; the mixed refrigerant refrigeration system comprises a mixed refrigerant compressor (102), a mixed refrigerant cooler (104), a mixed refrigerant terminal (106), and a mixed refrigerant compressor (102). The mixed refrigerant compressor (102) is connected to the inlet of the cooler (104), and one end of the cooler (104) outlet is connected to the inlet of the mixed refrigerant final-stage separation tank (107); the liquid phase outlet of the mixed refrigerant final-stage separation tank (107) is connected to the second channel of the main heat exchanger (105), and the second channel is connected to the seventh channel through valve 1 (113); the gas phase outlet of the mixed refrigerant final-stage separation tank (107) is connected to the third channel of the main heat exchanger (105), and the The third channel is connected to the inlet of the mixed refrigerant medium-pressure separation tank (108); the liquid phase outlet of the mixed refrigerant medium-pressure separation tank (108) is connected to the sixth channel of the main heat exchanger (105), valve two (114), and the mixed refrigerant low-pressure separation tank (109) in sequence; the gas phase outlet of the mixed refrigerant medium-pressure separation tank (108) is connected to the fifth channel of the main heat exchanger (105), and is connected to the seventh channel through valve three (115); the liquid phase and gas phase outlets of the mixed refrigerant low-pressure separation tank (109) merge and are connected to the eighth channel of the main heat exchanger (105), and the outlet of the eighth channel is connected to the inlet of the compressor (102) , forming a mixed refrigerant closed-loop circulation path; a nitrogen circulation system, comprising a nitrogen compressor (101), a nitrogen cooler (103) and a liquid nitrogen separation tank (110), wherein the outlet of the compressor (101) is connected to the nitrogen cooler (103) and the fourth channel of the main heat exchanger (105) in sequence; the outlet of the third channel of the subcooler (106) is connected to the inlet of the liquid nitrogen separation tank (110) through valve four (116), the liquid phase outlet of the liquid nitrogen separation tank (110) is connected to the fourth channel of the subcooler (106), and the gas phase outlet is connected to the ninth channel of the main heat exchanger (105), forming a nitrogen refrigeration and reheating path.

2. The hydrogen low-temperature precooling device according to claim 1, characterized in that: Each separation tank in the mixed refrigerant system is provided with an independent heat exchange branch, which is respectively connected to different temperature zone channels of the main heat exchanger (105). The liquid phase refrigerant of the mixed refrigerant final separation tank (107) is cooled through the second channel, and after being throttled by valve one (113), it provides low temperature section cooling capacity at the upper part of the eighth channel. The mixed refrigerant low-pressure separation tank (109) provides the middle cooling capacity through the lower part of the eighth channel. The gas phase refrigerant of the mixed refrigerant medium-pressure separation tank (108) is cooled through the fifth channel, and after being throttled by valve three (115), it provides terminal cooling capacity through the seventh channel.

3. The hydrogen low-temperature precooling device according to claim 1, characterized in that: The low-temperature adsorber (111) and the normal-parahydrogen converter (112) are sequentially arranged and connected after the supercooler (106). After being heated through corresponding processes, they are cooled to corresponding temperatures through the cooler (106), thereby forming an impurity removal and molecular conversion functional module.

4. The hydrogen low-temperature precooling device according to claim 1, characterized in that: In the main heat exchanger (105), the heat exchange channels of hydrogen, mixed refrigerant and nitrogen are distributed from the high temperature zone to the low temperature zone along the hydrogen flow direction, and the flow directions are arranged relative to each other to form a countercurrent heat exchange structure.

5. The hydrogen low-temperature precooling device according to claim 1, characterized in that: The mixed refrigerant refrigeration system eliminates the mixed refrigerant final-stage separation tank (107) and the corresponding second channel of the main heat exchanger (105), and the mixed refrigerant compressor (102) is directly connected to the mixed refrigerant medium-pressure separation tank (108) after passing through the mixed refrigerant cooler (104).

6. The hydrogen low-temperature precooling device according to claim 1, characterized in that: The nitrogen circulation refrigeration system eliminates the cooling path of nitrogen through the fourth channel of the main heat exchanger (105) and the third channel of the subcooler (106), and uses external liquid nitrogen instead. The external liquid nitrogen enters the liquid nitrogen separation tank (110) for gas-liquid separation after throttling, and the liquid phase liquid nitrogen is connected to the fourth channel of the subcooler (106) for cooling.

7. The hydrogen low-temperature precooling device according to claim 1, characterized in that: The nitrogen output by the nitrogen compressor (101) is cooled by the nitrogen cooler (103) and no longer flows back to the nitrogen circulation system, but is consumed as a utility of the device.

8. The hydrogen low-temperature precooling device according to claim 1, characterized in that: The nitrogen compressor (101) and the mixed refrigerant compressor (102) may be reciprocating, screw, or centrifugal compressors.

9. The hydrogen low-temperature precooling device according to claim 1, characterized in that: The nitrogen cooler (103) and the mixed refrigerant cooler (104) can be air-cooled, water-cooled, ammonia-cooled, lithium bromide-cooled, propane-cooled, or a combination of two thereof; the main heat exchanger (105) and the subcooler (106) can be coil-wound heat exchangers, plate-fin heat exchangers, or printed circuit board heat exchangers.

10. A method for low-temperature precooling of hydrogen, achieved by the device for low-temperature precooling of hydrogen according to any one of claims 1 to 9, characterized in that: The steps include: Hydrogen precooling and conversion step: the raw hydrogen passes through the main heat exchanger (105), the subcooler (106), the low-temperature adsorber (111) and the normal-parahydrogen converter (112) in sequence for heat exchange cooling, impurity removal and molecular structure conversion. The converted hydrogen returns to the subcooler for further cooling and is output as precooled hydrogen that meets the temperature and structure requirements. Mixed refrigerant circulation cooling steps: After being compressed and cooled, the mixed refrigerant enters the mixed refrigerant final separation tank, the mixed refrigerant medium-pressure separation tank, and the mixed refrigerant low-pressure separation tank in sequence for multi-stage gas-liquid separation. Each separation product flows into different channels of the main heat exchanger, releases cold energy through throttling, is reheated in the main heat exchanger, and finally flows back to the compressor to form a closed-loop cooling supply; Nitrogen circulation cooling steps: After compression and cooling, nitrogen passes through the main heat exchanger and subcooler in sequence for liquefaction, throttling, and separation. The liquid nitrogen is supplied to the subcooler to provide cooling capacity, and the gaseous nitrogen is reheated through the main heat exchanger and returned to the compressor, forming a closed cycle path; Cold distribution and heat recovery steps: Different channels in the main heat exchanger are responsible for releasing cold in high, medium and low temperature zones respectively, forming a countercurrent heat exchange between hydrogen and the refrigerant, and completing heat recovery in the low temperature channel to achieve an efficient and energy-saving deep cold heat exchange process.

11. The method for low-temperature precooling of hydrogen according to claim 10, characterized in that: The raw hydrogen pressure is between 1 and 8 MPa or 20 and 30 MPa, and the purity is between 99.9% and 99.999%.

12. The method for low-temperature precooling of hydrogen according to claim 10, characterized in that: The operating temperature of the raw hydrogen after passing through the main heat exchanger (105) is between -162 and -183°C, and the operating temperature of the raw hydrogen after passing through the subcooler (106) is between -173 and -196°C.

13. The method for low-temperature precooling of hydrogen according to claim 10, characterized in that: The inlet and outlet operating pressures of the nitrogen compressor (101) are respectively between 0.1 and 0.76 MPa and 1.6 and 6 MPa.

14. The method for low-temperature precooling of hydrogen according to claim 10, characterized in that: The inlet and outlet operating pressures of the mixed refrigerant compressor (102) are respectively between 0.15 and 0.6 MPa and 1.5 and 5 MPa.

15. The method for low-temperature precooling of hydrogen according to claim 10, characterized in that: The operating temperature of the mixed refrigerant medium-pressure separation tank (108) is between -10 and -100°C.

16. The method for low-temperature precooling of hydrogen according to claim 10, characterized in that: The mixed refrigerant is composed of at least four gases of methane, ethylene, nitrogen and butane, wherein the volume fraction ranges are: methane 25-35%, ethylene 20-40%, nitrogen 10-20%, butane 25-40%.

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