Device and method for preparing liquefied hydrogen through helium expansion

Abstract

The invention discloses a device and a method for preparing liquefied hydrogen through helium expansion, and relates to the technical field of hydrogen liquefaction. Multi-stage expansion refrigeration is combined with an ortho-parahydrogen converter, low-pressure helium subjected to expansion cooling through an expansion machine at each stage is combined with low-pressure helium subjected to expansion cooling at the previous stage after being provided with cooling capacity through a heat exchanger at the current stage, and the low-pressure helium is returned to the heat exchanger at the previous stage; the low-pressure helium which provides the cooling capacity goes out of the heat exchanger and is serially driven to the multi-stage compression unit through the compression end of the expansion machine, so that the circulation of a refrigerant is realized; precooling is conducted through helium expansion, liquid nitrogen input or nitrogen liquefaction throttling circulation refrigeration in an existing nitrogen precooling technology is avoided, the technological process is simplified, and the load and cost of a compressor are reduced. Orthohydrogen can be converted into parahydrogen in a low-temperature environment through the multi-stage ortho-parahydrogen converter, the ortho-hydrogen concentration and the liquid hydrogen evaporation loss are effectively reduced in the process, and the stability of a liquid hydrogen product is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen liquefaction, and in particular to a device and method for producing liquefied hydrogen by helium expansion. Background Art

[0002] As an efficient and clean energy carrier, the importance of hydrogen energy is becoming increasingly prominent. In many fields such as transportation and industry, the application of hydrogen is becoming more and more extensive. Especially in high-end fields such as fuel cell vehicles and aerospace, hydrogen energy is regarded as an important direction for future energy development. However, the storage and transportation of hydrogen have always been the key bottleneck restricting its large-scale application. Traditional hydrogen storage methods, such as high-pressure gaseous storage and solid-state storage, have many shortcomings in energy density, safety and cost. In contrast, liquid hydrogen has the advantages of high energy density, increased vehicle (equipment) driving range, high hydrogen storage purity, low-pressure liquid storage, low transportation cost and safety of use compared to large-scale high-pressure gaseous forms. It is considered to be an ideal way to achieve large-scale and commercial storage and transportation of hydrogen energy.

[0003] Achieving large-scale, efficient, and intensive hydrogen liquefaction is a key challenge in liquid hydrogen production technology. Commonly used industrial hydrogen liquefaction processes include the Linde-Hampson cycle liquefaction system based on the Joule-Thompson effect, the Claude cycle liquefaction system using liquid nitrogen precooling, and the reverse Brayton cycle system using helium expansion for refrigeration and liquefaction. Thanks to significant advances in helium refrigeration technology and the process safety advantages of the turbine expanders used in the helium expansion process, the process of producing liquefied hydrogen using helium expansion has achieved practical application on a certain scale. The reverse Brayton cycle system uses helium as the cryogenic refrigerant, forming a helium refrigeration cycle independent of the feed hydrogen supply. The precooled helium is expanded and cooled to the liquid hydrogen temperature range through a multi-stage turbine expander. A heat exchanger then provides cooling to the feed hydrogen, which has undergone precooling and catalytic conversion of normal and para-hydrogen, ultimately cooling and liquefying the gaseous hydrogen. However, the traditional helium-refrigerated hydrogen liquefaction process usually uses nitrogen pre-cooling and then uses colder helium for deep-cold liquefaction. Since the latent heat of vaporization of liquid nitrogen is small, relying solely on liquid nitrogen for pre-cooling will cause the compressor load to be too large, thereby increasing energy consumption. Therefore, the shortcomings of this process method need further optimization and improvement.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The object of the present invention is to provide an apparatus and method for producing liquefied hydrogen by helium expansion, aiming to achieve efficient conversion of raw hydrogen to liquid hydrogen while reducing the load and cost of the compressor.

[0006] The present invention is achieved in that:

[0007] In a first aspect, the present invention provides an apparatus for producing liquefied hydrogen by helium expansion, comprising a hydrogen liquefaction and conversion unit and a refrigeration cycle unit, wherein the hydrogen liquefaction and conversion unit comprises a multi-stage heat exchanger and at least one stage of normal-para hydrogen converter, and the refrigeration cycle unit comprises a multi-stage expander, a compression unit, and a first cooler;

[0008] A normal-parahydrogen converter is provided between two adjacent heat exchangers. The number of stages of the heat exchanger is consistent with the number of stages of the expander. Both the heat exchanger and the expander are n-stage, and each expander has an expansion end and a compression end.

[0009] A hydrogen cooling channel, a refrigerant cooling channel, and a refrigerant reheating channel are provided on each of the first-stage heat exchanger to the n-1-stage heat exchanger. A hydrogen cooling channel and a refrigerant reheating channel are provided on the n-stage heat exchanger. The outlet of the hydrogen cooling channel on the heat exchanger is connected to the inlet of the hydrogen cooling channel on the heat exchanger of the next stage. The normal-parahydrogen converter is located between two adjacent stages of the heat exchanger.

[0010] The outlet of the compression unit is connected to the first cooler. The outlet of the first cooler is divided into two paths. One path is connected to the inlet of the expansion end of the first-stage expander, and the other path is connected to the inlet of the refrigerant cooling channel on the first-stage heat exchanger. The outlet of the expansion end of the first-stage expander merges with the outlet of the refrigerant reheating channel of the second-stage heat exchanger and then connects to the inlet of the refrigerant reheating channel on the first-stage heat exchanger.

[0011] The outlet of the refrigerant cooling channel from the first-stage heat exchanger to the n-2-stage heat exchanger is divided into two paths, one of which is connected to the inlet of the expansion end of the expander of the next stage, and the other is connected to the inlet of the refrigerant cooling channel on the next-stage heat exchanger. The outlet of the expansion end of the expander merges with the outlet of the refrigerant reheating channel of the next-stage heat exchanger and then connects to the inlet of the refrigerant reheating channel of the corresponding stage heat exchanger.

[0012] The outlet of the refrigerant cooling channel on the n-1th stage heat exchanger is connected to the inlet of the expansion end of the nth stage expander, and the outlet of the expansion end of the nth stage expander is connected to the inlet of the refrigerant reheating channel of the nth stage heat exchanger;

[0013] The outlet of the refrigerant reheating channel of the first-stage heat exchanger is connected to the inlet of the compression end of the first-stage expander, and the compression ends of the multi-stage expanders are connected in series, and the outlet of the compression end of the n-th stage expander is connected to the inlet of the compression unit.

[0014] In an optional embodiment, a second cooler is further provided on the connecting pipeline between the outlet of the compression end of the n-th stage expander and the inlet of the compression unit.

[0015] In an optional embodiment, the number of stages of the multi-stage heat exchanger and the multi-stage expander is 4-6.

[0016] In an optional embodiment, the outlet of the hydrogen cooling flow channel of the n-th stage heat exchanger is connected to a liquid hydrogen output pipeline, and a liquid hydrogen throttle valve is provided on the liquid hydrogen output pipeline.

[0017] In an optional embodiment, the normal-para hydrogen converter is multi-stage, and each stage of the normal-para hydrogen converter is located between two adjacent stages of heat exchangers. The outlet of the hydrogen cooling channel on the heat exchanger is connected to the inlet of the corresponding normal-para hydrogen converter, and the outlet of the normal-para hydrogen converter is connected to the inlet of the hydrogen cooling channel on the corresponding next stage of heat exchanger.

[0018] In a second aspect, the present invention provides a method for producing liquefied hydrogen by helium expansion, wherein the liquefied hydrogen is produced using the apparatus described in any one of the aforementioned embodiments, comprising:

[0019] The raw hydrogen is cooled in the hydrogen cooling channel on the multi-stage heat exchanger in turn, and is processed by the normal-para-hydrogen converter between the two adjacent heat exchangers;

[0020] After being compressed and cooled by the compression unit and the first cooler, the high-pressure refrigerant is divided into two streams. The first high-pressure refrigerant is cooled by the expansion end of the first-stage expander to obtain low-pressure refrigerant. The low-pressure refrigerant is then combined with the refrigerant output from the outlet of the refrigerant recuperation channel of the second-stage heat exchanger and enters the refrigerant recuperation channel on the first-stage heat exchanger to provide cooling for the hydrogen and the second high-pressure refrigerant.

[0021] The outlet of the refrigerant cooling channel from the first stage heat exchanger to the n-2 stage heat exchanger is divided into two streams. One stream enters the expansion end of the expander of the next stage to be cooled to obtain low-pressure refrigerant, which is then combined with the refrigerant output from the outlet of the refrigerant reheating channel of the next stage heat exchanger and enters the refrigerant reheating channel of the corresponding stage heat exchanger to provide cooling for hydrogen and the other stream.

[0022] The material output from the refrigerant cooling channel on the n-1 stage heat exchanger enters the expansion end of the n stage expander for cooling to obtain low-pressure refrigerant, and then enters the refrigerant reheating channel of the n stage heat exchanger to provide cooling capacity for hydrogen cooling;

[0023] The material output from the refrigerant reheating channel of the first-stage heat exchanger enters the compression end of the first-stage expander, and is then compressed in sequence by the compression end of the multi-stage expander, and then enters the compression unit and the first cooler for compression and cooling, completing the refrigerant refrigeration cycle.

[0024] In an optional embodiment, the refrigerant includes helium and hydrogen, and the mole fraction of the helium is 60% to 99.5%, and the mole fraction of the hydrogen is 0.5% to 40%.

[0025] In an optional embodiment, the high-pressure refrigerant has a temperature of 35°C-45°C and a pressure of 4000kPaA-5000kPaA;

[0026] The temperature of the refrigerant after reheating in the first stage heat exchanger is 35℃-40℃, and the pressure is 550kPaA-650kPaA.

[0027] In an optional embodiment, the raw hydrogen is purified and pre-compressed, and the temperature of the raw hydrogen is 35° C. to 45° C., and the pressure is 2500 kPaA to 3500 kPaA.

[0028] In an optional embodiment, the raw hydrogen is cooled to -260°C to -240°C through a multi-stage heat exchanger, and the pressure is reduced to 2940kPaA to 2960kPaA;

[0029] Preferably, the temperature of the liquid hydrogen product formed after passing through the liquid hydrogen throttle valve is -260°C to -240°C, and the pressure is 100kPaA to 120kPaA.

[0030] In an optional embodiment, the number of stages of the multi-stage heat exchanger and the multi-stage expander is 5;

[0031] The raw hydrogen is cooled to a temperature of -100°C to -90°C through the first stage heat exchanger, cooled to a temperature of -175°C to -165°C through the second stage heat exchanger, cooled to a temperature of -215°C to -210°C through the third stage heat exchanger, cooled to a temperature of -240°C to -235°C through the fourth stage heat exchanger, and cooled to a temperature of -255°C to -250°C through the fifth stage heat exchanger;

[0032] After expansion and cooling at the expansion end of the first-stage expander, the temperature is -105°C to -85°C and the pressure is 550kPaA-650kPaA. The temperature of the refrigerant output from the refrigerant reheating channel of the second-stage heat exchanger is -110°C to -90°C and the pressure is 550kPaA-650kPaA. The temperature of the second high-pressure refrigerant after cooling through the first-stage heat exchanger is -105°C to -85°C and the pressure is 4450kPaA-4500kPaA.

[0033] After expansion and cooling at the expansion end of the second-stage expander, the temperature is -178°C to -168°C and the pressure is 560kPaA-660kPaA. The refrigerant temperature output from the refrigerant reheating flow channel of the third-stage heat exchanger is -180°C to -170°C and the pressure is 560kPaA-660kPaA. After cooling through the second-stage heat exchanger, the temperature of the refrigerant is -178°C to -168°C and the pressure is 4445kPaA-4495kPaA.

[0034] After expansion and cooling at the expansion end of the third-stage expander, the temperature is -220°C to -210°C and the pressure is 570kPaA-670kPaA. The temperature of the refrigerant output from the refrigerant reheating flow channel of the fourth-stage heat exchanger is -225°C to -215°C and the pressure is 570kPaA-670kPaA. After cooling through the third-stage heat exchanger, the temperature of the refrigerant is -220°C to -210°C and the pressure is 4440kPaA-4490kPaA.

[0035] After expansion and cooling at the expansion end of the fourth-stage expander, the temperature is -245°C to -230°C and the pressure is 580kPaA-680kPaA. The refrigerant temperature output from the refrigerant reheating flow channel of the fifth-stage heat exchanger is -245°C to -235°C and the pressure is 580kPaA-680kPaA. After cooling through the fourth-stage heat exchanger, the temperature of the refrigerant is -240°C to -235°C and the pressure is 4435kPaA-4485kPaA.

[0036] After expansion and cooling at the expansion end of the fifth-stage expander, the temperature is -260°C to -250°C and the pressure is 590kPaA to 660kPaA.

[0037] The present invention has the following beneficial effects: it combines multi-stage expansion refrigeration with an ortho-parahydrogen converter. The low-pressure helium expanded and cooled by each stage expander provides cooling through the current stage heat exchanger, then merges with the low-pressure helium expanded and cooled by the previous stage and returns to the previous stage heat exchanger. The low-pressure helium that has provided cooling exits the heat exchanger and is then driven in series through the compression end of the expander to a multi-stage compression unit, achieving refrigerant circulation. The use of helium expansion for pre-cooling avoids the need for liquid nitrogen input or nitrogen liquefaction throttling cycle refrigeration in existing nitrogen pre-cooling technologies, simplifies the process flow, and reduces the load and cost of the compressor. The multi-stage ortho-parahydrogen converter can convert orthohydrogen into parahydrogen at low temperatures. This process effectively reduces orthohydrogen concentration and liquid hydrogen evaporation loss, thereby improving the stability of the liquid hydrogen product.

[0038] Furthermore, existing helium expansion processes generally use pure helium as a raw material. In contrast, this invention uses helium containing trace amounts of hydrogen as the expansion medium. This unique formula effectively lowers the helium temperature, significantly improving refrigeration efficiency and providing a superior technical solution for liquid hydrogen production. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 A diagram of an apparatus for producing liquefied hydrogen by expanding helium according to an embodiment of the present invention.

[0041] Explanation of the main component symbols: 10-Helium expansion device for producing liquefied hydrogen; 101-first stage heat exchanger; 102-second stage heat exchanger; 103-third stage heat exchanger; 104-fourth stage heat exchanger; 105-fifth stage heat exchanger; 201-first stage normal-para hydrogen converter; 202-second stage normal-para hydrogen converter; 203-third stage normal-para hydrogen converter; 204-fourth stage normal-para hydrogen converter; 301-first stage expander; 302-second stage expander; 303-third stage expander; 304-fourth stage expander; 305-fifth stage expander; 301A-expansion end of first stage expander; 30 1B-compression end of the first-stage expander; 302A-expansion end of the second-stage expander; 302B-compression end of the second-stage expander; 303A-expansion end of the third-stage expander; 303B-compression end of the third-stage expander; 304A-expansion end of the fourth-stage expander; 304B-compression end of the fourth-stage expander; 305A-expansion end of the fifth-stage expander; 305B-compression end of the fifth-stage expander; 401-compression unit; 501-first cooler; 502-second cooler; 601-liquid hydrogen throttle valve; 001-hydrogen cooling flow channel; 002-refrigerant cooling flow channel; 003-refrigerant reheating flow channel. DETAILED DESCRIPTION

[0042] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the embodiments of the present invention. It should be understood that the described embodiments are only a portion of the embodiments of the present invention, not all of them. Generally, the components of the embodiments of the present invention described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations.

[0044] In the description of the present invention, it should be noted that the terms "inner" and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the product of the application is typically placed when in use. These terms are intended solely to facilitate the description of the present invention and simplify the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," etc., etc., are used solely for distinction and should not be construed as indicating or implying relative importance.

[0045] It should also be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "disposed" and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0046] The present invention provides an apparatus 10 for producing liquefied hydrogen by helium expansion, comprising a hydrogen liquefaction and conversion unit and a refrigeration cycle unit. The hydrogen liquefaction and conversion unit is used to cool the raw hydrogen in stages to obtain a liquid hydrogen product; the refrigeration cycle unit is used to provide a multi-stage refrigerant for hydrogen refrigeration and realize the circulation of the refrigerant.

[0047] The hydrogen liquefaction and conversion unit includes a multi-stage heat exchanger and a multi-stage normal-parahydrogen converter. The refrigeration cycle unit includes a multi-stage expander, a compression unit 401 and a first cooler 501. The number of stages of the heat exchanger is consistent with the number of stages of the expander, and both the heat exchanger and the expander have n stages, where n is greater than or equal to 2, such as 2, 3, 4, 5, 6, 7, 8, 9, etc. The specific number of stages is not limited and is set according to process requirements.

[0048] Figure 1 The figure shows a five-stage heat exchanger, which specifically includes a first-stage heat exchanger 101, a second-stage heat exchanger 102, a third-stage heat exchanger 103, a fourth-stage heat exchanger 104, and a fifth-stage heat exchanger 105. A normal-parahydrogen converter is provided between two adjacent heat exchangers. Figure 1 The multi-stage normal-para hydrogen converter is four-stage, specifically including a first-stage normal-para hydrogen converter 201, a second-stage normal-para hydrogen converter 202, a third-stage normal-para hydrogen converter 203 and a fourth-stage normal-para hydrogen converter 204.

[0049] like Figure 1As shown, the multi-stage expander also has five stages, specifically including a first-stage expander 301, a second-stage expander 302, a third-stage expander 303, a fourth-stage expander 304, and a fifth-stage expander 305. Each stage expander has an expansion end and a compression end, i.e., the first-stage expander 301 has a first-stage expander expansion end 301A and a first-stage expander compression end 301B, the second-stage expander 302 has a second-stage expander expansion end 302A and a second-stage expander compression end 302B, the third-stage expander 303 has a third-stage expander expansion end 303A and a third-stage expander compression end 303B, the fourth-stage expander 304 has a fourth-stage expander expansion end 304A and a fourth-stage expander compression end 304B, and the fifth-stage expander 305 has a fifth-stage expander expansion end 305A and a fifth-stage expander compression end 305B.

[0050] The number of heat exchanger stages and expander stages is not limited to Figure 1 In the fifth stage, for n-stage heat exchangers and n-stage expanders, the first-stage heat exchanger 101 uses the cold source provided by the first-stage expander 301 to cool the raw hydrogen, the second-stage heat exchanger 102 uses the cold source provided by the second-stage expander 302 to cool the raw hydrogen, and so on, the n-stage heat exchanger uses the cold source provided by the n-stage expander to cool the raw hydrogen.

[0051] Furthermore, hydrogen cooling channel 001, refrigerant cooling channel 002, and refrigerant reheating channel 003 are provided on each of the first-stage heat exchanger 101 through the n-1-stage heat exchanger. The n-stage heat exchanger is provided with hydrogen cooling channel 001 and refrigerant reheating channel 003. The outlet of hydrogen cooling channel 001 on the heat exchanger is connected to the inlet of the corresponding n-para hydrogen converter, and the outlet of the n-para hydrogen converter is connected to the inlet of hydrogen cooling channel 001 on the corresponding next-stage heat exchanger. In this way, the raw hydrogen is cooled step by step through the n-stage heat exchangers. The n-para hydrogen converter is used between two adjacent heat exchangers for the n-para catalytic conversion of hydrogen, converting the orthohydrogen into parahydrogen at a low temperature. This process effectively reduces the orthohydrogen concentration and the amount of liquid hydrogen evaporation loss, thereby improving the stability of the liquid hydrogen product.

[0052] The outlet end of the compression unit 401 is connected to the first cooler 501. The outlet of the first cooler 501 is divided into two paths, one path is connected to the inlet of the expansion end 301A of the first-stage expander, and the other path is connected to the inlet of the refrigerant cooling channel 002 on the first-stage heat exchanger 101. The outlet of the expansion end 301A of the first-stage expander is merged with the outlet of the refrigerant reheating channel 003 of the second-stage heat exchanger 102 and then connected to the inlet of the refrigerant reheating channel 003 on the first-stage heat exchanger 101, providing refrigerant for cooling hydrogen and high-pressure refrigerant.

[0053] Similarly, the outlet of the refrigerant cooling channel 002 from the first-stage heat exchanger 101 to the n-2-stage heat exchanger is divided into two paths: one path connects to the inlet of the expansion end of the expander in the next stage, and the other path connects to the inlet of the refrigerant cooling channel 002 in the next-stage heat exchanger. The outlet of the expansion end of the expander merges with the outlet of the refrigerant reheating channel 003 of the next-stage heat exchanger and then connects to the inlet of the refrigerant reheating channel 003 of the corresponding stage heat exchanger, providing refrigerant for cooling the hydrogen and refrigerant. The outlet of the refrigerant cooling channel 002 on the n-1-stage heat exchanger connects to the inlet of the expansion end of the n-stage expander, and the outlet of the expansion end of the n-stage expander connects to the inlet of the refrigerant reheating channel 003 of the n-stage heat exchanger, providing refrigerant for cooling the hydrogen.

[0054] Furthermore, the outlet of the refrigerant reheating channel 003 of the first-stage heat exchanger 101 is connected to the inlet of the compression end 301B of the first-stage expander, and the compression ends of the multi-stage expanders are connected in series. The outlet of the compression end of the n-th stage expander is connected to the inlet of the compression unit 401. The refrigerant is pressurized by the compression end of the multi-stage expander, and then enters the compression unit 401 for further compression and is cooled by the first cooler 501 to obtain high-pressure refrigerant, thereby realizing the circulation of the refrigerant.

[0055] In some embodiments, a second cooler 502 is further provided on the connecting pipeline between the outlet of the compression end of the n-th stage expander and the inlet of the compression unit 401. The second cooler 502 is used for cooling before entering the compression unit 401 to reduce the energy consumption of the compression unit 401.

[0056] In a preferred embodiment, the number of stages of the multi-stage heat exchanger and the multi-stage expander is 4-6. Within this range of stages, it can better adapt to the working conditions and achieve efficient conversion from raw hydrogen to liquid hydrogen while reducing the load and cost of the compressor.

[0057] In some embodiments, the outlet of the hydrogen cooling channel 001 of the nth stage heat exchanger is connected to a liquid hydrogen output pipeline, and a liquid hydrogen throttle valve 601 is provided on the liquid hydrogen output pipeline. The liquid hydrogen pressure is regulated by the liquid hydrogen throttle valve 601 to meet the parameter requirements of the product.

[0058] Specifically, each expander stage can be a commercially available cryogenic turbine expander, the output shaft of which is in driving connection with a shaft-driven compressor. The helium compressor used in compression unit 401 can be single-stage or multi-stage (not limited to two-stage, three-stage, or four-stage), depending on the specific application. Helium compressor types include reciprocating, screw, or centrifugal compressors. The heat exchanger at each stage can be plate-fin, coil-wound, multi-pass convection, or other types.

[0059] The para-hydrogen converter used in the embodiment of the present invention can be a single-stage conversion or a multi-stage conversion (not limited to two-stage, three-stage, four-stage, etc.) according to the specific application situation. The para-hydrogen converter types include adiabatic para-hydrogen converter, isothermal para-hydrogen converter or continuous para-hydrogen converter, and its para-hydrogen conversion catalyst includes but is not limited to activated carbon, chromium-aluminum alloy, nickel-chromium alloy, Fe(OH)3, CO(OH)3, Cr(OH)3 and Mn(OH)4, etc. and mixtures thereof in any proportion.

[0060] An embodiment of the present invention further provides a method for producing liquefied hydrogen by helium expansion. The method of producing liquefied hydrogen by helium expansion 10 provided in an embodiment of the present invention comprises the following steps:

[0061] Hydrogen liquefaction and conversion: The raw hydrogen is cooled in sequence through the hydrogen cooling channel 001 on the multi-stage heat exchanger to achieve step-by-step cooling of the raw hydrogen; at the same time, it is processed by the ortho-para-hydrogen converter between the two adjacent heat exchangers, and the ortho-para-hydrogen converter is used to perform ortho-para catalytic conversion of hydrogen, converting ortho-hydrogen into para-hydrogen under low temperature conditions. This process effectively reduces the ortho-hydrogen concentration and the evaporation loss of liquid hydrogen, and improves the stability of the liquid hydrogen product.

[0062] Refrigerant cycle:

[0063] After compression and cooling by the compression unit 401 and the first cooler 501, the high-pressure refrigerant is divided into two streams. The first high-pressure refrigerant is cooled by the expansion end 301A of the first-stage expander to obtain low-pressure refrigerant. After merging with the refrigerant output from the outlet of the refrigerant reheating flow path 003 of the second-stage heat exchanger 102, it enters the refrigerant reheating flow path 003 on the first-stage heat exchanger 101 to provide cooling for the hydrogen and the second high-pressure refrigerant. Similarly, from the first-stage heat exchanger 101 to the outlet of the refrigerant cooling flow path 002 on the n-2-stage heat exchanger, two streams are divided. One stream enters the expansion end of the next-stage expander to be cooled and obtain low-pressure refrigerant. After merging with the refrigerant output from the outlet of the refrigerant reheating flow path 003 of the next-stage heat exchanger, it enters the refrigerant reheating flow path 003 of the corresponding stage heat exchanger to provide cooling for the hydrogen and the other stream. The material output from the refrigerant cooling channel 002 on the n-1 stage heat exchanger enters the expansion end of the n stage expander to be cooled to obtain low-pressure refrigerant, and then enters the refrigerant reheating channel 003 of the n stage heat exchanger to provide cooling capacity for hydrogen cooling.

[0064] Furthermore, the material output from the refrigerant reheating channel 003 of the first-stage heat exchanger 101 enters the compression end of the first-stage expander 301, is then compressed in sequence through the compression end of the multi-stage expander, and then enters the compression unit 401 and the first cooler 501 for compression and cooling, completing the refrigeration cycle of the refrigerant.

[0065] It should be noted that the present invention combines multi-stage expansion refrigeration with a normal-parahydrogen converter, and utilizes helium refrigeration cycle and reflux gas thermal management technology to accurately control temperature and energy conversion to ensure the stability of liquid hydrogen products.

[0066] In some embodiments, the refrigerant includes helium and hydrogen, with the mole fraction of helium ranging from 60% to 99.5% (e.g., 60%, 70%, 80%, 90%, 99%, etc.), and the mole fraction of hydrogen ranging from 0.5% to 40% (e.g., 0.5%, 1%, 10%, 20%, 30%, 40%, etc.). This embodiment of the present invention creatively uses helium containing trace amounts of hydrogen as the expansion medium. This unique formula can effectively reduce the temperature of the helium and significantly improve the refrigeration effect, providing a better technical solution for liquid hydrogen production.

[0067] In some embodiments, the temperature of the high-pressure refrigerant generated after compression and cooling by the compression unit 401 and the first cooler 501 is 35°C-45°C, such as 35°C, 40°C, 45°C, etc.; the pressure of the high-pressure refrigerant is 4000kPaA-5000kPaA, such as 4000kPaA, 4500kPaA, 5000kPaA, etc. The temperature of the refrigerant after reheating output by the refrigerant reheating channel 003 on the first-stage heat exchanger 101 is 35°C-40°C, such as 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, etc.; and the pressure is 550kPaA-650kPaA, such as 550kPaA, 580kPaA, 600kPaA, 620kPaA, 650kPaA, etc.

[0068] In some embodiments, the raw hydrogen is purified and pre-compressed, and the temperature of the raw hydrogen is 35°C to 45°C (e.g., 35°C, 40°C, 45°C, etc.), and the pressure is 2500kPaA to 3500kPaA (e.g., 2500kPaA, 2800kPaA, 3000kPaA, 3200kPaA, 3500kPaA, etc.). The raw hydrogen is cooled to -260°C to -240°C (e.g., -260°C, -255°C, -250°C, -245°C, -240°C, etc.) through a multi-stage heat exchanger, and the pressure is reduced to 2940kPaA to 2960kPaA (e.g., 2940kPaA, 2950kPaA, 2960kPaA, etc.). The liquid hydrogen product formed after passing through the liquid hydrogen throttle valve 601 has a temperature of -260°C to -240°C (e.g., -260°C, -255°C, -250°C, -245°C, -240°C, etc.) and a pressure of 100kPaA to 120kPaA (e.g., 100kPaA, 110kPaA, 120kPaA, etc.). The purified and pre-compressed hydrogen is cooled to a certain temperature through a multi-stage heat exchanger, and in the cooling stage, undergoes a para-hydrogen catalytic conversion of hydrogen through a multi-stage para-hydrogen converter, ultimately cooling to, for example, -252°C, and then liquefying and throttling to obtain the liquid hydrogen product.

[0069] like Figure 1 As shown, the number of stages of the multi-stage heat exchanger and the multi-stage expander is 5. The specific steps and operating conditions of each link are as follows:

[0070] The raw hydrogen is cooled to a temperature of -100°C to -90°C through the first-stage heat exchanger 101, cooled to a temperature of -175°C to -165°C through the second-stage heat exchanger 102, cooled to a temperature of -215°C to -210°C through the third-stage heat exchanger 103, cooled to a temperature of -240°C to -235°C through the fourth-stage heat exchanger 104, and cooled to a temperature of -255°C to -250°C through the fifth-stage heat exchanger 105;

[0071] After expansion and cooling at the expansion end of the first-stage expander 301, the temperature is -105°C to -85°C and the pressure is 550kPaA-650kPaA. The refrigerant output from the refrigerant reheating channel 003 of the second-stage heat exchanger 102 has a temperature of -110°C to -90°C and a pressure of 550kPaA-650kPaA. The temperature of the second high-pressure refrigerant after cooling through the first-stage heat exchanger 101 is -105°C to -85°C and the pressure is 4450kPaA-4500kPaA.

[0072] After expansion and cooling at the expansion end of the second-stage expander 302, the temperature is -178°C to -168°C and the pressure is 560kPaA-660kPaA. The temperature of the refrigerant output from the refrigerant reheating flow path 003 of the third-stage heat exchanger 103 is -180°C to -170°C and the pressure is 560kPaA-660kPaA. After cooling through the second-stage heat exchanger 102, the temperature of the refrigerant is -178°C to -168°C and the pressure is 4445kPaA-4495kPaA.

[0073] After expansion and cooling at the expansion end of the third-stage expander 303, the temperature is -220°C to -210°C and the pressure is 570kPaA-670kPaA. The temperature of the refrigerant output from the refrigerant reheating flow path 003 of the fourth-stage heat exchanger 104 is -225°C to -215°C and the pressure is 570kPaA-670kPaA. After cooling through the third-stage heat exchanger 103, the temperature of the refrigerant is -220°C to -210°C and the pressure is 4440kPaA-4490kPaA.

[0074] After expansion and cooling at the expansion end of the fourth-stage expander 304, the temperature is -245°C to -230°C and the pressure is 580kPaA-680kPaA. The refrigerant output from the refrigerant reheating flow path 003 of the fifth-stage heat exchanger 105 has a temperature of -245°C to -235°C and a pressure of 580kPaA-680kPaA. After cooling through the fourth-stage heat exchanger 104, the temperature of the refrigerant is -240°C to -235°C and the pressure is 4435kPaA-4485kPaA.

[0075] After expansion and cooling at the expansion end of the fifth-stage expander 305, the temperature is -260°C to -250°C, and the pressure is 590kPaA to 660kPaA.

[0076] It should be noted that by regulating the operating temperature, pressure and other parameters of each link, the energy consumption and load of the compressor can be further reduced, while achieving stable and efficient preparation of liquid hydrogen products.

[0077] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0078] Example 1

[0079] This embodiment provides a method for producing liquefied hydrogen by expanding helium. Figure 1 The device 10 for preparing liquefied hydrogen by expanding helium comprises the following steps:

[0080] The molar fraction of 99% helium (containing 1% hydrogen) is used as the expansion cooling medium, and the multi-stage compression unit is used. Figure 1As shown, the helium expander has five-stage expansion; the heat exchanger has five-stage heat exchange; the normal-para-hydrogen converter has four-stage adiabatic catalytic conversion; and the throttling stage of liquid hydrogen leaving the cryogenic cold box is one-stage throttling.

[0081] Hydrogen liquefaction and conversion system

[0082] The purified and pre-compressed raw hydrogen (temperature: 40°C, pressure: 3000kPaA) first enters the first-stage heat exchanger 101 and is cooled to -95°C (2990kPaA), and then enters the first-stage normal-parahydrogen converter 201 for catalytic conversion (the conversion is carried out at -95 to -93°C, and the normal-parahydrogen conversion catalyst is an iron-based catalyst Fe(OH)3). After the hydrogen leaves the first-stage normal-parahydrogen converter 201, it enters the second-stage heat exchanger 102 and is cooled to -170°C (2980kPaA), and then enters the second-stage normal-parahydrogen converter 202 for further catalytic conversion. After leaving the converter, the hydrogen enters the third-stage heat exchanger 102. 03 is cooled to -213°C (2970kPaA), and then sent to the third-stage normal-para-hydrogen converter 203 for the next catalytic conversion. After leaving the converter, the hydrogen is sent to the fourth-stage heat exchanger 104 for cooling to -237°C (2960kPaA), and then enters the fourth-stage normal-para-hydrogen converter 204 for final conversion. After the normal-para-hydrogen conversion, the hydrogen enters the fifth-stage heat exchanger 105, and the outlet temperature is stabilized at about -252°C (2950kPaA) under the extremely low temperature environment provided by the helium refrigeration cycle. Finally, it is throttled by the liquid hydrogen throttle valve 601 to form a liquid hydrogen product (-252.7°C, 110kPaA) and transported to the downstream unit.

[0083] Helium refrigeration cycle system

[0084] Refrigeration stage:

[0085] ① Helium with a molar fraction of 99% (containing 1% hydrogen) is first compressed and cooled to 40°C high-pressure helium (4500 kPaA) through compression unit 401 and first cooler 501, and then divided into two streams. The first high-pressure helium (40°C, 4500 kPaA) is expanded and cooled to -97.5°C low-pressure helium (610 kPaA) through the expansion end 301A of the first-stage expander. This low-pressure helium is then combined with the refrigerant (-97.8°C, 610 kPaA) of the downstream second-stage heat exchanger that recovers cold energy. The low-pressure helium then enters the first-stage heat exchanger 101 to provide cold energy for the hydrogen (40°C, 3000 kPaA) and the second high-pressure helium (40°C, 4500 kPaA). The helium is then reheated to 37°C (600 kPaA) and returned to the upstream first-stage expander compression end 301B.

[0086] ② The second stream of high-pressure helium (40°C, 4500 kPaA) is cooled to -95°C in the first-stage heat exchanger 101 and then divided into two streams of sub-high-pressure helium (4490 kPaA). The first stream of sub-high-pressure helium (-95°C, 4490 kPaA) is expanded and cooled to -172.9°C low-pressure helium (620 kPaA) at the expansion end 302A of the second-stage expander. The low-pressure helium is then combined with the refrigerant (-173°C, 620 kPaA) of the downstream third-stage heat exchanger for recovering cold, and then enters the second-stage heat exchanger 102 to provide coldness for the hydrogen (-95°C, 2990 kPaA) and the second stream of sub-high-pressure helium (-95°C, 4490 kPaA). The gas is then reheated to -97.8°C and returned to the upper first-stage heat exchanger 101.

[0087] ③ The second stream of sub-high-pressure helium (-95°C, 4490 kPaA) is cooled to -170°C in the second-stage heat exchanger 102 and then divided into two streams of medium-pressure helium (4480 kPaA). The first stream of medium-pressure helium (-170°C, 4480 kPaA) is expanded and cooled to low-pressure helium (630 kPaA) at -214.9°C at the expansion end 303A of the third-stage expander. The low-pressure helium is combined with the refrigerant (-215.9°C, 630 kPaA) of the downstream fourth-stage heat exchanger for recovering cold energy, and then enters the third-stage heat exchanger 103 to provide cold energy for hydrogen (-170°C, 2980 kPaA) and the second stream of medium-pressure helium (-170°C, 4480 kPaA). The gas is then reheated to -173°C and returned to the upper second-stage heat exchanger 102.

[0088] ④ The second stream of medium-pressure helium (-170°C, 4480 kPaA) is cooled to -213°C in the third-stage heat exchanger 103 and then divided into two streams of sub-medium-pressure helium (4470 kPaA). The first stream of sub-medium-pressure helium (-213°C, 4470 kPaA) is expanded and cooled to -239.2°C low-pressure helium (640 kPaA) at the expansion end 304A of the fourth-stage expander. The low-pressure helium is combined with the refrigerant (-239°C, 640 kPaA) of the fifth-stage heat exchanger for recovering cold energy downstream and enters the fourth-stage heat exchanger to provide cold energy for hydrogen (-213°C, 2970 kPaA) and the second stream of sub-medium-pressure helium (-213°C, 4470 kPaA). The reheat is then reheated to -215.9°C and returned to the upper third-stage heat exchanger 103.

[0089] ⑤ The second stream of sub-medium-pressure helium (-213°C, 4470kPaA) is cooled to -237°C (4460kPaA) via the fourth-stage heat exchanger, and then fed into the fifth-stage expander expansion end 305A to be expanded and cooled to low-pressure helium (650kPaA) at -252.8°C. The low-pressure helium (-252.8°C, 650kPaA) directly enters the fifth-stage heat exchanger 105 as the fifth-stage heat exchanger refrigerant to provide the required cooling capacity for the liquefaction of hydrogen (-237°C, 2960kPaA), and then is reheated to -239°C before returning to the upper fourth-stage heat exchanger 104, completing the refrigeration stage.

[0090] Circulation stage: The low-pressure helium expanded and cooled by each stage of the turbine expander provides cooling through the current stage heat exchanger, then merges with the low-pressure helium expanded and cooled by the previous stage and returns to the previous stage heat exchanger. The low-pressure helium after providing cooling exits the heat exchanger and is then driven in series through the compression end of the turbine expander to the multi-stage compression unit 401. That is, the low-pressure helium (37°C, 600 kPaA) after exiting the first stage heat exchanger 101 and completing cooling returns to the first stage expander compression end 301B, the second stage expander compression end 302B, the third stage expander compression end 303B, the fourth stage expander compression end 304B, the fifth stage expander compression end 305B and the second cooler 502 of the multi-stage series connection, and is then transported to the multi-stage compression unit 401 and the first cooler 501 for compression and cooling into high-pressure helium (40°C, 4500 kPaA). The high-pressure helium is then divided into two streams and transported to the downstream unit for cooling, thus forming a closed helium expansion and refrigeration cycle system.

[0091] After testing: the unit energy consumption index of this embodiment is 0.7906kW / Nm 3 Purify hydrogen and reduce the proportion of helium (90%) in the refrigeration cycle system (energy consumption index: 0.7921kW / Nm 3 Purified hydrogen, see Example 2 for details) is about 0.19% less; compared to a refrigeration cycle system with an 80% helium ratio (energy consumption index: 0.8014kW / Nm 3 Purified hydrogen, see Example 3 for details) is about 1.37% less; than the refrigeration cycle system with a 70% helium ratio (energy consumption index: 0.8101kW / Nm 3 Purification of hydrogen, see Example 4) is about 2.46% less; in summary, the ratio of the expansion cooling medium in this embodiment is the best under the device, which reduces the energy consumption of the system and improves the energy utilization rate.

[0092] Example 2

[0093] The only difference from Example 1 is that the proportion of helium in the refrigerant medium of the refrigeration cycle system is reduced to 90%.

[0094] This embodiment also uses Figure 1The device 10 for preparing liquefied hydrogen by expanding helium comprises the following steps:

[0095] The molar fraction of 90% helium (containing 10% hydrogen) is used as the expansion cooling medium, and the multi-stage compression unit is used. Figure 1 As shown, the helium expander has five-stage expansion; the heat exchanger has five-stage heat exchange; the normal-para-hydrogen converter has four-stage adiabatic catalytic conversion; and the throttling stage of liquid hydrogen leaving the cryogenic cold box is one-stage throttling.

[0096] Hydrogen liquefaction and conversion system

[0097] The purified and pre-compressed raw hydrogen (temperature: 40°C, pressure: 3000kPaA) first enters the first-stage heat exchanger 101 and is cooled to -95°C (2990kPaA), and then enters the first-stage normal-parahydrogen converter 201 for catalytic conversion (the conversion is carried out at -95 to -93°C, and the normal-parahydrogen conversion catalyst is an iron-based catalyst Fe(OH)3). After the hydrogen leaves the first-stage normal-parahydrogen converter 201, it enters the second-stage heat exchanger 102 and is cooled to -170°C (2980kPaA), and then enters the second-stage normal-parahydrogen converter 202 for further catalytic conversion. After leaving the converter, the hydrogen enters the third-stage heat exchanger 102. 03 is cooled to -213°C (2970kPaA), and then sent to the third-stage normal-para-hydrogen converter 203 for the next catalytic conversion. After leaving the converter, the hydrogen is sent to the fourth-stage heat exchanger 104 for cooling to -237°C (2960kPaA), and then enters the fourth-stage normal-para-hydrogen converter 204 for final conversion. After the normal-para-hydrogen conversion, the hydrogen enters the fifth-stage heat exchanger 105, and the outlet temperature is stabilized at about -252°C (2950kPaA) under the extremely low temperature environment provided by the helium refrigeration cycle. Finally, it is throttled by the liquid hydrogen throttle valve 601 to form a liquid hydrogen product (-252.7°C, 110kPaA) and transported to the downstream unit.

[0098] Helium refrigeration cycle system

[0099] Refrigeration stage:

[0100] ① Helium with a molar fraction of 90% (containing 10% hydrogen) is first compressed and cooled to 40°C high-pressure helium (4500 kPaA) through compression unit 401 and first cooler 501, and then divided into two streams. The first high-pressure helium (40°C, 4500 kPaA) is expanded and cooled to -94.6°C low-pressure helium (610 kPaA) through the expansion end 301A of the first-stage expander. This low-pressure helium is then combined with the refrigerant (-98.6°C, 610 kPaA) of the downstream second-stage heat exchanger that recovers cold energy. The low-pressure helium then enters the first-stage heat exchanger 101 to provide cold energy to the hydrogen (40°C, 3000 kPaA) and the second high-pressure helium (40°C, 4500 kPaA). The helium is then reheated to 37°C (600 kPaA) and returned to the upstream first-stage expander compression end 301B.

[0101] ② The second stream of high-pressure helium (40°C, 4500 kPaA) is cooled to -95°C in the first-stage heat exchanger 101 and then divided into two streams of sub-high-pressure helium (4490 kPaA). The first stream of sub-high-pressure helium (-95°C, 4490 kPaA) is expanded and cooled to -171.5°C low-pressure helium (620 kPaA) at the expansion end 302A of the second-stage expander. This low-pressure helium is then combined with the refrigerant (-172.8°C, 620 kPaA) of the downstream third-stage heat exchanger for recovering cold, and then enters the second-stage heat exchanger 102 to provide cold energy for the hydrogen (-95°C, 2990 kPaA) and the second stream of sub-high-pressure helium (-95°C, 4490 kPaA). The gas is then reheated to -98.6°C and returned to the upper first-stage heat exchanger 101.

[0102] ③ The second stream of sub-high-pressure helium (-95°C, 4490 kPaA) is cooled to -170°C in the second-stage heat exchanger 102 and then divided into two streams of medium-pressure helium (4480 kPaA). The first stream of medium-pressure helium (-170°C, 4480 kPaA) is expanded and cooled to -213.6°C low-pressure helium (630 kPaA) at the expansion end 303A of the third-stage expander. This low-pressure helium is combined with the refrigerant (-216.7°C, 630 kPaA) of the downstream fourth-stage heat exchanger for recovering cold, and then enters the third-stage heat exchanger 103 to provide cold energy for the hydrogen (-170°C, 2980 kPaA) and the second stream of medium-pressure helium (-170°C, 4480 kPaA). After that, it is reheated to -172.8°C and returns to the upper second-stage heat exchanger 102.

[0103] ④ The second stream of intermediate-pressure helium (-170°C, 4480 kPaA) is cooled to -213°C in the third-stage heat exchanger 103 and then divided into two streams of sub-intermediate-pressure helium (4470 kPaA). The first stream of sub-intermediate-pressure helium (-213°C, 4470 kPaA) is expanded and cooled to -238.1°C low-pressure helium (640 kPaA) at the expansion end 304A of the fourth-stage expander. This low-pressure helium is then combined with the refrigerant (-239.3°C, 640 kPaA) from the downstream fifth-stage heat exchanger for recovering cold. The low-pressure helium then enters the fourth-stage heat exchanger to provide coldness for the hydrogen (-213°C, 2970 kPaA) and the second stream of sub-intermediate-pressure helium (-213°C, 4470 kPaA). The reheat is then reheated to -216.7°C and returned to the upper third-stage heat exchanger 103.

[0104] ⑤ The second stream of sub-medium-pressure helium (-213°C, 4470kPaA) is cooled to -237°C (4460kPaA) via the fourth-stage heat exchanger, and then fed into the fifth-stage expander expansion end 305A to be expanded and cooled to low-pressure helium (650kPaA) at -252.7°C. The low-pressure helium (-252.7°C, 650kPaA) directly enters the fifth-stage heat exchanger 105 as the fifth-stage heat exchanger refrigerant to provide the required cooling capacity for the liquefaction of hydrogen (-237°C, 2960kPaA), and then is reheated to -239.3°C before returning to the upper fourth-stage heat exchanger 104, completing the refrigeration stage.

[0105] Circulation stage: The low-pressure helium expanded and cooled by each stage of the turbine expander provides cooling through the current stage heat exchanger, then merges with the low-pressure helium expanded and cooled by the previous stage and returns to the previous stage heat exchanger. The low-pressure helium after providing cooling exits the heat exchanger and is then driven in series through the compression end of the turbine expander to the multi-stage compression unit 401. That is, the low-pressure helium (37°C, 600 kPaA) after exiting the first stage heat exchanger 101 and completing cooling returns to the first stage expander compression end 301B, the second stage expander compression end 302B, the third stage expander compression end 303B, the fourth stage expander compression end 304B, the fifth stage expander compression end 305B and the second cooler 502 of the multi-stage series connection, and is then transported to the multi-stage compression unit 401 and the first cooler 501 for compression and cooling into high-pressure helium (40°C, 4500 kPaA). The high-pressure helium is then divided into two streams and transported to the downstream unit for cooling, thus forming a closed helium expansion and refrigeration cycle system.

[0106] Example 3

[0107] The only difference from Example 1 is that the proportion of helium in the refrigerant medium of the refrigeration cycle system is reduced to 80%.

[0108] This embodiment also uses Figure 1 The device 10 for preparing liquefied hydrogen by expanding helium comprises the following steps:

[0109] The molar fraction of 80% helium (containing 20% hydrogen) is used as the expansion cooling medium, and the multi-stage compression unit is used. Figure 1 As shown, the helium expander has five-stage expansion; the heat exchanger has five-stage heat exchange; the normal-para-hydrogen converter has four-stage adiabatic catalytic conversion; and the throttling stage of liquid hydrogen leaving the cryogenic cold box is one-stage throttling.

[0110] Hydrogen liquefaction and conversion system

[0111] The purified and pre-compressed raw hydrogen (temperature: 40°C, pressure: 3000kPaA) first enters the first-stage heat exchanger 101 and is cooled to -95°C (2990kPaA), and then enters the first-stage normal-parahydrogen converter 201 for catalytic conversion (the conversion is carried out at -95 to -93°C, and the normal-parahydrogen conversion catalyst is an iron-based catalyst Fe(OH)3). After the hydrogen leaves the first-stage normal-parahydrogen converter 201, it enters the second-stage heat exchanger 102 and is cooled to -170°C (2980kPaA), and then enters the second-stage normal-parahydrogen converter 202 for further catalytic conversion. After leaving the converter, the hydrogen enters the third-stage heat exchanger 102. 03 is cooled to -213°C (2970kPaA), and then sent to the third-stage normal-para-hydrogen converter 203 for the next catalytic conversion. After leaving the converter, the hydrogen is sent to the fourth-stage heat exchanger 104 for cooling to -237°C (2960kPaA), and then enters the fourth-stage normal-para-hydrogen converter 204 for final conversion. After the normal-para-hydrogen conversion, the hydrogen enters the fifth-stage heat exchanger 105, and the outlet temperature is stabilized at about -252°C (2950kPaA) under the extremely low temperature environment provided by the helium refrigeration cycle. Finally, it is throttled by the liquid hydrogen throttle valve 601 to form a liquid hydrogen product (-252.7°C, 110kPaA) and transported to the downstream unit.

[0112] Helium refrigeration cycle system

[0113] Refrigeration stage:

[0114] ① Helium with a molar fraction of 80% (containing 20% hydrogen) is first compressed and cooled to 40°C high-pressure helium (4500 kPaA) through compression unit 401 and first cooler 501, and then divided into two streams. The first high-pressure helium (40°C, 4500 kPaA) is expanded and cooled to -91.5°C low-pressure helium (610 kPaA) through the expansion end 301A of the first-stage expander. This low-pressure helium is then combined with the refrigerant (-99.8°C, 610 kPaA) of the downstream second-stage heat exchanger that recovers cold energy. The low-pressure helium then enters the first-stage heat exchanger 101 to provide cold energy to the hydrogen (40°C, 3000 kPaA) and the second high-pressure helium (40°C, 4500 kPaA). The helium is then reheated to 37°C (600 kPaA) and returned to the upstream first-stage expander compression end 301B.

[0115] ② The second stream of high-pressure helium (40°C, 4500 kPaA) is cooled to -95°C in the first-stage heat exchanger 101 and then divided into two streams of sub-high-pressure helium (4490 kPaA). The first stream of sub-high-pressure helium (-95°C, 4490 kPaA) is expanded and cooled to -170°C low-pressure helium (620 kPaA) at the expansion end 302A of the second-stage expander. This low-pressure helium is combined with the refrigerant (-172.2°C, 620 kPaA) of the downstream third-stage heat exchanger for recovering cold, and then enters the second-stage heat exchanger 102 to provide cold energy for the hydrogen (-95°C, 2990 kPaA) and the second stream of sub-high-pressure helium (-95°C, 4490 kPaA). It is then reheated to -99.8°C and returned to the upper first-stage heat exchanger 101.

[0116] ③ The second stream of sub-high-pressure helium (-95°C, 4490 kPaA) is cooled to -170°C in the second-stage heat exchanger 102 and then divided into two streams of medium-pressure helium (4480 kPaA). The first stream of medium-pressure helium (-170°C, 4480 kPaA) is expanded and cooled to -212.3°C low-pressure helium (630 kPaA) at the expansion end 303A of the third-stage expander. This low-pressure helium is combined with the refrigerant (-218.3°C, 630 kPaA) of the downstream fourth-stage heat exchanger for recovering cold, and then enters the third-stage heat exchanger 103 to provide cold energy for the hydrogen (-170°C, 2980 kPaA) and the second stream of medium-pressure helium (-170°C, 4480 kPaA). After that, it is reheated to -172.2°C and returns to the upper second-stage heat exchanger 102.

[0117] ④ The second stream of intermediate-pressure helium (-170°C, 4480 kPaA) is cooled to -213°C in the third-stage heat exchanger 103 and then divided into two streams of sub-intermediate-pressure helium (4470 kPaA). The first stream of sub-intermediate-pressure helium (-213°C, 4470 kPaA) is expanded and cooled to -237°C low-pressure helium (640 kPaA) at the expansion end 304A of the fourth-stage expander. This low-pressure helium is then combined with the refrigerant (-239.4°C, 640 kPaA) from the downstream fifth-stage heat exchanger for recovering cold. The low-pressure helium then enters the fourth-stage heat exchanger to provide coldness for the hydrogen (-213°C, 2970 kPaA) and the second stream of sub-intermediate-pressure helium (-213°C, 4470 kPaA). The reheat is then reheated to -218.3°C and returned to the upper third-stage heat exchanger 103.

[0118] ⑤ The second stream of sub-medium-pressure helium (-213°C, 4470 kPaA) is cooled to -237°C (4460 kPaA) via the fourth-stage heat exchanger and then fed into the fifth-stage expander expansion end 305A to be expanded and cooled to low-pressure helium (650 kPaA) at -252.7°C. The low-pressure helium (-252.7°C, 650 kPaA) directly enters the fifth-stage heat exchanger 105 as the fifth-stage heat exchanger refrigerant to provide the required cooling capacity for the liquefaction of hydrogen (-237°C, 2960 kPaA), and then is reheated to -239.4°C before returning to the upper fourth-stage heat exchanger 104, completing the refrigeration stage.

[0119] Circulation stage: The low-pressure helium expanded and cooled by each stage of the turbine expander provides cooling through the current stage heat exchanger, then merges with the low-pressure helium expanded and cooled by the previous stage and returns to the previous stage heat exchanger. The low-pressure helium after providing cooling exits the heat exchanger and is then driven in series through the compression end of the turbine expander to the multi-stage compression unit 401. That is, the low-pressure helium (37°C, 600 kPaA) after exiting the first stage heat exchanger 101 and completing cooling returns to the first stage expander compression end 301B, the second stage expander compression end 302B, the third stage expander compression end 303B, the fourth stage expander compression end 304B, the fifth stage expander compression end 305B and the second cooler 502 of the multi-stage series connection, and is then transported to the multi-stage compression unit 401 and the first cooler 501 for compression and cooling into high-pressure helium (40°C, 4500 kPaA). The high-pressure helium is then divided into two streams and transported to the downstream unit for cooling, thus forming a closed helium expansion and refrigeration cycle system.

[0120] Example 4

[0121] The only difference from Example 1 is that the proportion of helium in the refrigerant medium of the refrigeration cycle system is reduced to 70%.

[0122] This embodiment also uses Figure 1 The device 10 for preparing liquefied hydrogen by expanding helium comprises the following steps:

[0123] The molar fraction of 70% helium (containing 30% hydrogen) is used as the expansion cooling medium, and the multi-stage compression unit is used. Figure 1 As shown, the helium expander has five-stage expansion; the heat exchanger has five-stage heat exchange; the normal-para-hydrogen converter has four-stage adiabatic catalytic conversion; and the throttling stage of liquid hydrogen leaving the cryogenic cold box is one-stage throttling.

[0124] Hydrogen liquefaction and conversion system

[0125] The purified and pre-compressed raw hydrogen (temperature: 40°C, pressure: 3000kPaA) first enters the first-stage heat exchanger 101 and is cooled to -95°C (2990kPaA), and then enters the first-stage normal-parahydrogen converter 201 for catalytic conversion (the conversion is carried out at -95 to -93°C, and the normal-parahydrogen conversion catalyst is an iron-based catalyst Fe(OH)3). After the hydrogen leaves the first-stage normal-parahydrogen converter 201, it enters the second-stage heat exchanger 102 and is cooled to -170°C (2980kPaA), and then enters the second-stage normal-parahydrogen converter 202 for further catalytic conversion. After leaving the converter, the hydrogen enters the third-stage heat exchanger 102. 03 is cooled to -213°C (2970kPaA), and then sent to the third-stage normal-para-hydrogen converter 203 for the next catalytic conversion. After leaving the converter, the hydrogen is sent to the fourth-stage heat exchanger 104 for cooling to -237°C (2960kPaA), and then enters the fourth-stage normal-para-hydrogen converter 204 for final conversion. After the normal-para-hydrogen conversion, the hydrogen enters the fifth-stage heat exchanger 105, and the outlet temperature is stabilized at about -252°C (2950kPaA) under the extremely low temperature environment provided by the helium refrigeration cycle. Finally, it is throttled by the liquid hydrogen throttle valve 601 to form a liquid hydrogen product (-252.7°C, 110kPaA) and transported to the downstream unit.

[0126] Helium refrigeration cycle system

[0127] Refrigeration stage:

[0128] ① Helium with a molar fraction of 70% (containing 30% hydrogen) is first compressed and cooled to 40°C high-pressure helium (4500 kPaA) through the compression unit 401 and the first cooler 501, and then divided into two streams. The first high-pressure helium (40°C, 4500 kPaA) is expanded and cooled to -92.3°C low-pressure helium (560 kPaA) through the expansion end 301A of the first-stage expander. This low-pressure helium is then combined with the refrigerant (-100°C, 560 kPaA) of the downstream second-stage heat exchanger that recovers cold energy. The low-pressure helium then enters the first-stage heat exchanger 101 to provide cold energy for the hydrogen (40°C, 3000 kPaA) and the second high-pressure helium (40°C, 4500 kPaA). The helium is then reheated to 37.4°C (550 kPaA) and returned to the upstream first-stage expander compression end 301B.

[0129] ② The second stream of high-pressure helium (40°C, 4500 kPaA) is cooled to -95°C in the first-stage heat exchanger 101 and then divided into two streams of sub-high-pressure helium (4490 kPaA). The first stream of sub-high-pressure helium (-95°C, 4490 kPaA) is expanded and cooled to -170.6°C low-pressure helium (570 kPaA) at the expansion end 302A of the second-stage expander. This low-pressure helium is then combined with the refrigerant (-171.9°C, 570 kPaA) of the downstream third-stage heat exchanger for recovering cold, and then enters the second-stage heat exchanger 102 to provide cold energy for the hydrogen (-95°C, 2990 kPaA) and the second stream of sub-high-pressure helium (-95°C, 4490 kPaA). It is then reheated to -100°C and returned to the upper first-stage heat exchanger 101.

[0130] ③ The second stream of sub-high-pressure helium (-95°C, 4490 kPaA) is cooled to -170°C in the second-stage heat exchanger 102 and then divided into two streams of medium-pressure helium (4480 kPaA). The first stream of medium-pressure helium (-170°C, 4480 kPaA) is expanded and cooled to -212.2°C low-pressure helium (580 kPaA) at the expansion end 303A of the third-stage expander. This low-pressure helium is combined with the refrigerant (-219°C, 580 kPaA) of the downstream fourth-stage heat exchanger for recovering cold, and then enters the third-stage heat exchanger 103 to provide cold energy for the hydrogen (-170°C, 2980 kPaA) and the second stream of medium-pressure helium (-170°C, 4480 kPaA). After that, it is reheated to -171.9°C and returns to the upper second-stage heat exchanger 102.

[0131] ④ The second stream of intermediate-pressure helium (-170°C, 4480 kPaA) is cooled to -213°C in the third-stage heat exchanger 103 and then divided into two streams of sub-intermediate-pressure helium (4470 kPaA). The first stream of sub-intermediate-pressure helium (-213°C, 4470 kPaA) is expanded and cooled to -236.7°C low-pressure helium (592 kPaA) at the expansion end 304A of the fourth-stage expander. This low-pressure helium is then combined with the refrigerant (-239.5°C, 590 kPaA) from the downstream fifth-stage heat exchanger for recovering cold. The low-pressure helium then enters the fourth-stage heat exchanger to provide coldness for the hydrogen (-213°C, 2970 kPaA) and the second stream of sub-intermediate-pressure helium (-213°C, 4470 kPaA). The reheat is then reheated to -219°C and returned to the upper third-stage heat exchanger 103.

[0132] ⑤ The second stream of sub-medium-pressure helium (-213°C, 4470kPaA) is cooled to -237°C (4460kPaA) via the fourth-stage heat exchanger, and then fed into the fifth-stage expander expansion end 305A to expand and cool to low-pressure helium (600kPaA) at -252.2°C. The low-pressure helium (-252.2°C, 600kPaA) directly enters the fifth-stage heat exchanger 105 as the fifth-stage heat exchanger refrigerant to provide the required cooling capacity for the liquefaction of hydrogen (-237°C, 2960kPaA), and then is reheated to -239.5°C before returning to the upper fourth-stage heat exchanger 104, completing the refrigeration stage.

[0133] Circulation stage: The low-pressure helium expanded and cooled by each stage of the turbine expander provides cooling through the current stage heat exchanger, then merges with the low-pressure helium expanded and cooled by the previous stage and returns to the previous stage heat exchanger. The low-pressure helium after providing cooling exits the heat exchanger and is then driven in series through the compression end of the turbine expander to the multi-stage compression unit 401. That is, the low-pressure helium (37.4°C, 550 kPaA) after exiting the first stage heat exchanger 101 and completing cooling returns to the first stage expander compression end 301B, the second stage expander compression end 302B, the third stage expander compression end 303B, the fourth stage expander compression end 304B, the fifth stage expander compression end 305B and the second cooler 502 in the multi-stage series, and is then transported to the multi-stage compression unit 401 and the first cooler 501 for compression and cooling into high-pressure helium (40°C, 4500 kPaA). The high-pressure helium is then divided into two streams and transported to the downstream unit for cooling, thus forming a closed helium expansion and refrigeration cycle system.

[0134] In summary, the present invention provides an apparatus and method for producing liquefied hydrogen by helium expansion, which has the following advantages over conventional helium expansion processes for producing liquefied hydrogen:

[0135] (1) The present invention uses helium expansion for pre-cooling, avoiding the need for liquid nitrogen input or nitrogen liquefaction throttling cycle refrigeration in existing nitrogen pre-cooling technologies, simplifying the process flow and reducing the load and cost of the compressor. The working media of the present invention are limited to nitrogen and hydrogen, and the closed helium refrigeration cycle system and hydrogen liquefaction system are independent of each other. The system has the characteristics of large liquefaction capacity, strong independence, simple operation, wide practicality, and excellent liquefaction efficiency.

[0136] (2) The present invention uses a unique formula of helium (containing a trace amount of hydrogen) to perform multi-stage expansion refrigeration, forming a larger number of lower temperature gradients, thereby reducing the heat transfer temperature difference between the cold and hot sides and loss; in addition, the present invention utilizes the thermal management technology of helium refrigeration cycle and reflux gas to accurately control temperature and energy conversion, thereby reducing system energy consumption and improving energy utilization.

[0137] (3) The present invention can produce high-purity liquid hydrogen. Orthohydrogen can be converted into parahydrogen under low-temperature conditions through a multi-stage ortho-parahydrogen converter. This process effectively reduces the orthohydrogen concentration and the evaporation loss of liquid hydrogen, and improves the stability of the liquid hydrogen product. The ortho-parahydrogen converter is arranged outside the heat exchange flow channel. Although it may increase some cooling consumption, the gas and liquid channels in the device are not easily blocked, maintenance is convenient, adjustment is flexible, and operation is reliable.

[0138] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A device for producing liquefied hydrogen by expanding helium, characterized in that: It includes a hydrogen liquefaction and conversion unit and a refrigeration cycle unit, wherein the hydrogen liquefaction and conversion unit includes a multi-stage heat exchanger and at least one stage of normal-para hydrogen converter, and the refrigeration cycle unit includes a multi-stage expander, a compression unit and a first cooler; A normal-parahydrogen converter is provided between two adjacent heat exchangers, the number of stages of the heat exchanger is consistent with the number of stages of the expander, and both the heat exchanger and the expander are n-stage, and each stage of the expander has an expansion end and a compression end; A hydrogen cooling channel, a refrigerant cooling channel, and a refrigerant reheating channel are provided on each of the first-stage heat exchanger to the n-1-stage heat exchanger. A hydrogen cooling channel and a refrigerant reheating channel are provided on the n-stage heat exchanger. The outlet of the hydrogen cooling channel on the heat exchanger is connected to the inlet of the hydrogen cooling channel on the next-stage heat exchanger. The normal-parahydrogen converter is located between two adjacent stages of the heat exchanger. The outlet of the compression unit is communicated with the first cooler. The outlet of the first cooler is divided into two paths, one path is communicated with the inlet of the expansion end of the first-stage expander, and the other path is communicated with the inlet of the refrigerant cooling channel on the first-stage heat exchanger. The outlet of the expansion end of the first-stage expander merges with the outlet of the refrigerant reheating channel of the second-stage heat exchanger and then communicates with the inlet of the refrigerant reheating channel on the first-stage heat exchanger. The outlet of the refrigerant cooling channel from the first-stage heat exchanger to the n-2-stage heat exchanger is divided into two paths, one path is connected to the inlet of the expansion end of the expander of the next stage, and the other path is connected to the inlet of the refrigerant cooling channel on the heat exchanger of the next stage. The outlet of the expansion end of the expander merges with the outlet of the refrigerant reheating channel of the heat exchanger of the next stage and then connects to the inlet of the refrigerant reheating channel of the heat exchanger of the corresponding stage. The outlet of the refrigerant cooling channel on the n-1th stage heat exchanger is connected to the inlet of the expansion end of the nth stage expander, and the outlet of the expansion end of the nth stage expander is connected to the inlet of the refrigerant reheating channel of the nth stage heat exchanger; The outlet of the refrigerant reheating channel of the first-stage heat exchanger is connected to the inlet of the compression end of the first-stage expander, and the compression ends of the multi-stage expanders are connected in series, and the outlet of the compression end of the n-th stage expander is connected to the inlet of the compression unit.

2. The device according to claim 1, characterized in that A second cooler is further provided on the connecting pipeline between the outlet of the compression end of the n-th stage expander and the inlet of the compression unit.

3. The device according to claim 1 or 2, characterized in that The number of stages of the multi-stage heat exchanger and the multi-stage expander is 4-6.

4. The device according to claim 1, characterized in that The outlet of the hydrogen cooling flow channel of the n-th stage heat exchanger is connected to a liquid hydrogen output pipeline, and a liquid hydrogen throttle valve is provided on the liquid hydrogen output pipeline.

5. The device according to claim 1, characterized in that The normal-para hydrogen converter is multi-stage, and each stage of the normal-para hydrogen converter is located between two adjacent stages of heat exchangers. The outlet of the hydrogen cooling channel on the heat exchanger is connected to the inlet of the corresponding normal-para hydrogen converter, and the outlet of the normal-para hydrogen converter is connected to the inlet of the hydrogen cooling channel on the corresponding next stage of the heat exchanger.

6. A method for producing liquefied hydrogen by helium expansion, characterized in that: The device according to any one of claims 1 to 5 is used to prepare liquefied hydrogen, comprising: The raw hydrogen is cooled by the hydrogen cooling channel on the multi-stage heat exchanger in sequence, and is processed by the normal-para-hydrogen converter between two adjacent stages of the heat exchanger; The high-pressure refrigerant compressed and cooled by the compression unit and the first cooler is divided into two streams. The first high-pressure refrigerant is cooled by the expansion end of the first-stage expander to obtain low-pressure refrigerant, which is then combined with the refrigerant output from the outlet of the refrigerant recuperation flow channel of the second-stage heat exchanger and enters the refrigerant recuperation flow channel on the first-stage heat exchanger to provide cooling capacity for the hydrogen and the second high-pressure refrigerant. The outlet of the refrigerant cooling flow channel from the first-stage heat exchanger to the n-2-stage heat exchanger is divided into two streams. One stream enters the expansion end of the expander of the next stage to be cooled to obtain low-pressure refrigerant, which is then combined with the refrigerant output from the outlet of the refrigerant reheating flow channel of the next stage heat exchanger and then enters the refrigerant reheating flow channel of the corresponding stage heat exchanger to provide cooling for hydrogen and the other stream. The material output from the refrigerant cooling channel on the n-1 stage heat exchanger enters the expansion end of the n stage expander for cooling to obtain low-pressure refrigerant, and then enters the refrigerant reheating channel of the n stage heat exchanger to provide cooling capacity for hydrogen cooling; The material output from the refrigerant reheating channel of the first-stage heat exchanger enters the compression end of the first-stage expander, is then compressed in sequence by the compression end of the multi-stage expander, and then enters the compression unit and the first cooler for compression and cooling, completing the refrigerant refrigeration cycle.

7. The method according to claim 6, characterized in that The refrigerant includes helium and hydrogen, and the molar fraction of the helium is 60% to 99.5%, and the molar fraction of the hydrogen is 0.5% to 40%; Preferably, the temperature of the high-pressure refrigerant is 35°C-45°C, and the pressure is 4000kPaA-5000kPaA; The temperature of the refrigerant after reheating in the first-stage heat exchanger is 35°C-40°C, and the pressure is 500kPaA-650kPaA.

8. The method according to claim 7, characterized in that The raw hydrogen is purified and pre-compressed, and has a temperature of 35° C. to 45° C. and a pressure of 2500 kPaA to 3500 kPaA.

9. The method according to claim 8, characterized in that The raw hydrogen is cooled to -260°C to -240°C through the multi-stage heat exchanger, and the pressure is reduced to 2940kPaA to 2960kPaA; Preferably, the temperature of the liquid hydrogen product formed after passing through the liquid hydrogen throttle valve is -260°C to -240°C, and the pressure is 100kPaA to 120kPaA.

10. The method according to claim 9, characterized in that The number of stages of the multi-stage heat exchanger and the multi-stage expander is 5; The raw hydrogen is cooled to a temperature of -100°C to -90°C through the first stage heat exchanger, cooled to a temperature of -175°C to -165°C through the second stage heat exchanger, cooled to a temperature of -215°C to -210°C through the third stage heat exchanger, cooled to a temperature of -240°C to -235°C through the fourth stage heat exchanger, and cooled to a temperature of -255°C to -250°C through the fifth stage heat exchanger; The temperature of the refrigerant after expansion and cooling at the expansion end of the first-stage expander is -105°C to -85°C and the pressure is 550kPaA-650kPaA. The temperature of the refrigerant output from the refrigerant reheating flow channel of the second-stage heat exchanger is -110°C to -90°C and the pressure is 550kPaA-650kPaA. The temperature of the second high-pressure refrigerant after cooling through the first-stage heat exchanger is -105°C to -85°C and the pressure is 4450kPaA-4500kPaA. The temperature of the refrigerant after expansion and cooling at the expansion end of the second-stage expander is -178°C to -168°C and the pressure is 560kPaA-660kPaA. The temperature of the refrigerant output from the refrigerant reheating flow channel of the third-stage heat exchanger is -180°C to -170°C and the pressure is 560kPaA-660kPaA. The temperature of the refrigerant after cooling by the second-stage heat exchanger is -178°C to -168°C and the pressure is 4445kPaA-4495kPaA. The temperature of the refrigerant after expansion and cooling at the expansion end of the third-stage expander is -220°C to -210°C and the pressure is 570kPaA-670kPaA. The temperature of the refrigerant output from the refrigerant reheating flow channel of the fourth-stage heat exchanger is -225°C to -215°C and the pressure is 570kPaA-670kPaA. The temperature of the refrigerant after cooling through the third-stage heat exchanger is -220°C to -210°C and the pressure is 4440kPaA-4490kPaA. The temperature of the refrigerant after expansion and cooling at the expansion end of the fourth-stage expander is -245°C to -230°C and the pressure is 580kPaA-680kPaA. The temperature of the refrigerant output from the refrigerant reheating flow channel of the fifth-stage heat exchanger is -245°C to -235°C and the pressure is 580kPaA-680kPaA. The temperature of the refrigerant after cooling by the fourth-stage heat exchanger is -240°C to -235°C and the pressure is 4435kPaA-4485kPaA. After expansion and cooling at the expansion end of the fifth-stage expander, the temperature is -260°C to -250°C and the pressure is 590kPaA to 660kPaA.

Images