A hydrogen liquefaction system using cascade refrigeration and a split continuous converter
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HANGZHOU ZHONGTAI CRYOGENIC TECH CORP
- Filing Date
- 2023-05-23
- Publication Date
- 2026-07-24
Smart Images
Figure CN116608644B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of refrigeration and cryogenic engineering technology, and specifically relates to a hydrogen liquefaction system employing cascade refrigeration and a split continuous converter. Background Technology
[0002] The massive extraction and utilization of fossil fuels has led to enormous carbon dioxide emissions, which have become one of the most pressing environmental problems facing the world today. To achieve the goals of "carbon peaking and carbon neutrality," the development and utilization of green and clean energy is an important research direction for the future.
[0003] Hydrogen energy is considered the most promising clean energy source in the 21st century, playing an indispensable role in improving the energy structure, promoting the energy revolution, and achieving energy conservation and emission reduction.
[0004] Liquid hydrogen has a much higher density than gaseous hydrogen, thus offering a higher energy storage density for the same volume. Liquid hydrogen offers significant economic advantages in hydrogen energy storage and long-distance transportation, making it a crucial solution for the large-scale application of hydrogen energy in the future. However, the high energy consumption and low efficiency of the hydrogen liquefaction process hinder its industrialization. Therefore, there is an urgent need to provide a hydrogen liquefaction system that can improve efficiency and reduce equipment energy consumption. Summary of the Invention
[0005] The purpose of this invention is to solve the problems of high energy consumption and low efficiency in the hydrogen liquefaction process in the prior art, and to provide a hydrogen liquefaction system using cascade refrigeration and a split continuous converter.
[0006] The specific technical solution adopted in this invention is as follows:
[0007] This invention provides a hydrogen liquefaction system employing cascade refrigeration and a split-type continuous converter, comprising a compressor unit, a precooling cold box, a cryogenic cold box, a heat exchanger unit, an expander unit, an external cryogenic adsorber for the cold box, a gas-liquid separator group, and a liquid hydrogen storage tank; the specific structure of the system is as follows:
[0008] External feedstock hydrogen is connected to the inlet of the first pipeline, and the outlet of the first pipeline is connected to the inlet of the feedstock hydrogen compressor unit. The outlet of the feedstock hydrogen compressor unit has two branches: a first hydrogen refrigeration channel and a second pipeline. The second pipeline is connected to the first hot-side inlet of the first-stage heat exchanger, and the first hot-side outlet of the first-stage heat exchanger is connected to the inlet of the feedstock hydrogen cryogenic adsorber via the third pipeline. The outlet of the feedstock hydrogen cryogenic adsorber is connected to the first hot-side inlet of the second-stage heat exchanger via the fourth pipeline. The first hot-side outlet of the second-stage heat exchanger is connected to the inlet of the cryogenic adsorber inside the cold box via the fifth pipeline. The outlet of the cryogenic adsorber inside the cold box is connected to the tube-side inlet of the first-stage isothermal converter via the sixth pipeline. The tube-side outlet of the first-stage isothermal converter is connected to the hot-side inlet of the first-stage continuous converter via the seventh pipeline. The hot-side outlet of the first-stage continuous converter is connected to the hot-side inlet of the second-stage continuous converter via the eighth pipeline. The hot-side outlet of the second-stage continuous converter is connected to the first hot-side inlet of the fifth-stage heat exchanger via the ninth pipeline. The first hot-side outlet of the fifth-stage heat exchanger is connected to the tube-side inlet of the second-stage isothermal converter via the tenth pipeline. The tube-side outlet of the second-stage isothermal converter is connected to the ejector inlet via pipe eleven. The ejector outlet is connected to the hot-side inlet of the third-stage continuous converter via pipe twelfth. The hot-side outlet of the third-stage continuous converter is connected to the product hydrogen-liquid separator via pipes thirteenth and fourteenth. The bottom of the product hydrogen-liquid separator is connected to a liquid hydrogen storage tank.
[0009] The precooling section of the hydrogen liquefaction system uses propylene and carbon dioxide cycle refrigeration for cascade refrigeration to assist nitrogen cycle precooling; the cryogenic section uses an improved dual-pressure hydrogen cycle refrigeration, in which the first-stage continuous converter is separated from the third-stage heat exchanger, and the second-stage continuous converter is separated from the fourth-stage heat exchanger, forming a separate continuous converter.
[0010] Furthermore, the specific structure of the aforementioned nitrogen cycle precooling is as follows: the outlet of the medium-pressure nitrogen compressor unit is connected to the nitrogen inlet of the nitrogen-propylene heat exchanger via a first nitrogen channel. The nitrogen outlet of the nitrogen-propylene heat exchanger is connected to the inlet of a second nitrogen channel, and the outlet of the second nitrogen channel has two branches: a third nitrogen channel and a fourth nitrogen channel.
[0011] The outlet of the third nitrogen channel is connected to the second nitrogen inlet of the secondary heat exchanger, and it branches into two branches within the secondary heat exchanger. One branch connects sequentially to the nitrogen-liquid separator via the second nitrogen outlet, the ninth nitrogen channel, and the tenth nitrogen channel of the secondary heat exchanger. The other branch enters the medium-pressure nitrogen expander unit via the seventh nitrogen channel. The liquid nitrogen outlet of the nitrogen-liquid separator is connected to the inlet of the twelfth nitrogen channel, and the outlet of the twelfth nitrogen channel has two branches: the thirteenth nitrogen channel and the fifteenth nitrogen channel. The outlets of the thirteenth and fifteenth nitrogen channels are respectively connected to the shell-side inlet of the primary isothermal converter and the liquid nitrogen inlet of the cryogenic adsorber in the cold box. The outlet of the medium-pressure nitrogen expander unit is connected to the inlet of the eighth nitrogen channel.
[0012] The shell-side outlet of the primary isothermal converter and the nitrogen outlet of the cryogenic adsorber in the cold box are respectively connected to the inlets of the fourteenth and sixteenth nitrogen channels. The outlets of the fourteenth, sixteenth, and eighth nitrogen channels, as well as the eleventh nitrogen channel (connected to the nitrogen outlet of the nitrogen-liquid separator), converge into the seventeenth nitrogen channel. The outlet of the seventeenth nitrogen channel is connected to the first nitrogen inlet of the secondary heat exchanger, and the first nitrogen outlet of the secondary heat exchanger is connected to the nitrogen inlet of the primary heat exchanger via the nineteenth nitrogen channel. The nitrogen outlet of the primary heat exchanger is connected to the inlet of the twenty-first nitrogen channel.
[0013] The outlet of the fourth nitrogen channel is connected to the inlet of the high-pressure nitrogen expander. The outlet of the high-pressure nitrogen expander is connected to the secondary heat exchanger through the fifth nitrogen channel, and then connected to the pipeline between the low-pressure nitrogen compressor unit and the medium-pressure nitrogen compressor unit through the sixth nitrogen channel.
[0014] An eighteenth nitrogen channel is also provided at the outlet of the eighth nitrogen channel. The outlet of the eighteenth nitrogen channel is connected to the secondary heat exchanger and then exits through the twentieth nitrogen channel. The nitrogen channels converge through the twentieth and twenty-first nitrogen channels to the twenty-second nitrogen channel, and then connect in sequence to the low-pressure nitrogen compressor unit and the medium-pressure nitrogen compressor unit to form a nitrogen circulation precooling system.
[0015] Furthermore, the specific structure of the aforementioned cascade cooling is as follows:
[0016] The cascade refrigeration system comprises propylene cycle refrigeration and carbon dioxide cycle refrigeration. The carbon dioxide cycle refrigeration consists of a carbon dioxide compressor unit, a carbon dioxide expander unit, and a propylene-carbon dioxide heat exchanger. The propylene-carbon dioxide heat exchanger receives the cooling capacity provided by the carbon dioxide cycle refrigeration. The propylene cycle refrigeration consists of a propylene-carbon dioxide heat exchanger, a nitrogen-propylene heat exchanger, a propylene compressor unit, and a propylene expansion valve. The nitrogen-propylene heat exchanger receives the cooling capacity provided by the propylene cycle refrigeration and provides cooling capacity for pre-cooling the nitrogen cycle.
[0017] Furthermore, the specific structure of the improved dual-pressure hydrogen cycle refrigeration described above is as follows:
[0018] The first hydrogen refrigeration channel is connected to the inlet of the medium-pressure hydrogen compressor unit. The outlet of the medium-pressure hydrogen compressor unit is connected to the second hot-side inlet of the first-stage heat exchanger via the second hydrogen refrigeration channel. The second hot-side outlet of the first-stage heat exchanger is connected to the inlet of the circulating hydrogen cryogenic adsorber via the third hydrogen refrigeration channel. The outlet of the circulating hydrogen cryogenic adsorber is connected to the second hot-side inlet of the second-stage heat exchanger via the fourth hydrogen refrigeration channel. The second hot-side outlet of the second-stage heat exchanger is connected to the inlet of the fifth hydrogen refrigeration channel, and the outlet of the fifth hydrogen refrigeration channel is connected to the inlets of the sixth and seventh hydrogen refrigeration channels. The outlet of the sixth hydrogen refrigeration channel is connected to the hot-side inlet of the third-stage heat exchanger, and the hot-side outlet of the third-stage heat exchanger is connected to the hot-side inlet of the fourth-stage heat exchanger via the ninth hydrogen refrigeration channel. The hot-side outlet of the fourth-stage heat exchanger is connected to the inlet of the tenth hydrogen refrigeration channel, and the outlet of the tenth hydrogen refrigeration channel is connected to the eleventh and twelfth hydrogen refrigeration channels. The outlet of the eleventh hydrogen refrigeration channel is connected to the second hot-side inlet of the fifth-stage heat exchanger. The second hot-side outlet of the fifth-stage heat exchanger sequentially passes through the fourteenth hydrogen refrigeration channel and is throttled and cooled by a high-pressure throttling valve before entering the fifteenth hydrogen refrigeration channel. The outlet of the fifteenth hydrogen refrigeration channel is connected to the inlet of the medium-pressure gas-liquid separator. The gas phase outlet of the medium-pressure gas-liquid separator is connected to the inlet of the sixteenth hydrogen refrigeration channel. The bottom liquid phase outlet of the medium-pressure gas-liquid separator is provided with the seventeenth and eighteenth hydrogen refrigeration channels, respectively. The seventeenth hydrogen refrigeration channel is connected to the shell-side inlet of the second-stage isothermal converter, and the shell-side outlet of the second-stage isothermal converter is connected to the inlet of the twenty-fourth hydrogen refrigeration channel. The bottom outlet of the medium-pressure gas-liquid separator sequentially passes through the eighteenth hydrogen refrigeration channel and is throttled and cooled by a medium-pressure throttling valve before entering the nineteenth hydrogen refrigeration channel, and then connects to the inlet of the low-pressure gas-liquid separator. The liquid phase outlet of the low-pressure gas-liquid separator is connected to the cold-side inlet of the third-stage continuous converter via the twenty-first hydrogen refrigeration channel, and the cold-side outlet of the third-stage continuous converter is connected to the inlet of the twenty-second hydrogen refrigeration channel. The gas phase outlet of the low-pressure gas-liquid separator is connected to the inlet of the twentieth hydrogen refrigeration channel. The outlets of the twentieth and twenty-second hydrogen refrigeration channels converge at the inlet of the twenty-third hydrogen refrigeration channel, which in turn connects to the first cold-side inlet of the fifth-stage heat exchanger. The first cold-side outlet of the fifth-stage heat exchanger connects to the first cold-side inlet of the fourth-stage heat exchanger via the twenty-seventh hydrogen refrigeration channel. The first cold-side outlet of the fourth-stage heat exchanger connects to the first cold-side inlet of the third-stage heat exchanger via the thirty-first hydrogen refrigeration channel. The first cold-side outlet of the third-stage heat exchanger connects to the first cold-side inlet of the second-stage heat exchanger via the thirty-eighth hydrogen refrigeration channel. The first cold-side outlet of the second-stage heat exchanger connects to the first cold-side inlet of the first-stage heat exchanger via the fortieth hydrogen refrigeration channel. The first cold-side outlet of the first-stage heat exchanger, after reheating via the forty-second hydrogen refrigeration channel, connects to the low-pressure hydrogen compressor unit.
[0019] The outlet of the seventh hydrogen refrigeration channel is connected to the inlet of the high-pressure hydrogen expander unit, and the outlet of the high-pressure hydrogen expander unit is connected to the inlet of the eighth hydrogen refrigeration channel.
[0020] The outlet of the twelfth hydrogen refrigeration channel is connected to the inlet of the medium-pressure hydrogen expander, and the outlet of the medium-pressure hydrogen expander is connected to the inlet of the thirteenth hydrogen refrigeration channel. The outlets of the thirteenth, twenty-fourth, and sixteenth hydrogen refrigeration channels converge and connect to the inlet of the twenty-fifth hydrogen refrigeration channel. The outlet of the twenty-fifth hydrogen refrigeration channel is connected to the second cold-side inlet of the fifth-stage heat exchanger, and after reheating, it exits through the twenty-sixth hydrogen refrigeration channel. The outlet of the twenty-sixth hydrogen refrigeration channel is connected to the inlets of the twenty-eighth and twenty-ninth hydrogen refrigeration channels. The outlet of the twenty-ninth hydrogen refrigeration channel is connected to the cold-side inlet of the second-stage continuous converter, and the cold-side outlet of the second-stage continuous converter is connected to the inlet of the thirty-second hydrogen refrigeration channel. The outlet of the twenty-eighth hydrogen refrigeration channel is connected to the second cold-side inlet of the fourth-stage heat exchanger, and the second cold-side outlet of the fourth-stage heat exchanger is connected to the inlet of the thirtieth hydrogen refrigeration channel. The outlets of the thirtieth, eighth, and thirty-second hydrogen refrigeration channels converge to the inlet of the thirty-third hydrogen refrigeration channel. The outlet of the 33rd hydrogen refrigeration channel is connected to the inlet of the second cold side of the tertiary heat exchanger, and the outlet of the second cold side of the tertiary heat exchanger is connected to the inlet of the 35th hydrogen refrigeration channel.
[0021] A branch line, the 34th hydrogen refrigeration channel, is provided on the 33rd hydrogen refrigeration channel. The outlet of the 34th hydrogen refrigeration channel is connected to the cold-side inlet of the first-stage continuous converter. The cold-side outlet of the first-stage continuous converter is connected to the inlet of the 36th hydrogen refrigeration channel. The outlets of the 36th and 35th hydrogen refrigeration channels converge and connect to the inlet of the 37th hydrogen refrigeration channel. The outlet of the 37th hydrogen refrigeration channel is connected to the second cold-side inlet of the second-stage heat exchanger, and the second cold-side outlet of the second-stage heat exchanger is connected to the second cold-side inlet of the first-stage heat exchanger via the 39th hydrogen refrigeration channel. The second cold-side outlet of the first-stage heat exchanger is connected to the medium-pressure hydrogen compressor unit via the 41st hydrogen refrigeration channel.
[0022] Furthermore, the aforementioned circulating hydrogen cryogenic adsorber and raw material hydrogen cryogenic adsorber are filled with molecular sieves for removing impurities that are prone to freezing and clogging in the cryogenic channel.
[0023] Furthermore, a nitrogen throttling valve is provided between the ninth and tenth nitrogen channels. An end throttling valve is provided between the thirteenth and fourteenth pipes. A high-pressure throttling valve is provided between the fourteenth and fifteenth hydrogen refrigeration channels. A medium-pressure throttling valve is provided between the eighteenth and nineteenth hydrogen refrigeration channels.
[0024] Preferably, the first-stage isothermal converter and the second-stage isothermal converter are tubular fixed-bed reactors, wherein the feed hydrogen is introduced into the tube side channel and the refrigerant is introduced into the shell side channel, and the tube side channel is filled with a corresponding catalytic performance of the hydrogen conversion catalyst according to the cooling temperature zone.
[0025] Preferably, the first-stage continuous converter, the second-stage continuous converter, and the third-stage continuous converter are aluminum plate-fin heat exchangers, wherein the feed hydrogen channel is filled with a neutral hydrogen conversion catalyst with corresponding catalytic performance according to the cooling temperature zone.
[0026] Preferably, the pre-cooling cold box is an atmospheric pressure cold box, and the cryogenic cold box is a vacuum cold box.
[0027] Preferably, the gas phase outlet of the aforementioned product hydrogen-liquid separator merges with the hydrogen evaporated from the liquid hydrogen storage tank through the fifteenth channel and then enters the ejector to recover hydrogen.
[0028] Compared with the prior art, the present invention has the following advantages:
[0029] (1) The present invention adopts a hydrogen liquefaction system with cascade refrigeration and a split continuous converter. According to the temperature zone, the corresponding cooling capacity is provided and the corresponding type of positive and negative hydrogen conversion catalyst is set. With the goal of the lowest specific energy consumption, the optimized system process parameters can meet the design requirements with the lowest refrigerant flow rate.
[0030] (2) The hydrogen liquefaction system provided by the present invention has strong adaptability to different gas sources. The external low-temperature adsorber in the cold box can effectively prevent impurities such as carbon dioxide, methane and nitrogen in the product hydrogen from freezing and blocking during the cooling process.
[0031] (3) In the hydrogen liquefaction system provided by the present invention, the continuous converter is separated from the main heat exchanger, which reduces the equipment cost and maintenance cost;
[0032] (4) The hydrogen liquefaction system provided by the present invention has the advantages of high hydrogen liquefaction rate, high purity of liquid hydrogen and high secondary hydrogen content in the product. It can achieve a secondary hydrogen content of not less than 98% in the liquid hydrogen product, and can produce 13 to 25 tons of liquefied hydrogen per day. The specific energy consumption of the system does not exceed 9.5 kWh / kg liquid hydrogen. Attached Figure Description
[0033] Figure 1 A schematic diagram of a hydrogen liquefaction system employing cascade refrigeration and a split-type continuous converter is provided for an embodiment.
[0034] In the diagram: HE1—First-stage heat exchanger, HE2—Second-stage heat exchanger, S3—Low-temperature adsorber in the cold box, R1—First-stage isothermal converter, V1—Nitrogen throttling valve, D1—Nitrogen-liquid separator, HE7—Nitrogen-propylene heat exchanger, V5—Propylene throttling valve, HE8—Propylene-carbon dioxide heat exchanger, HE3-1—Third-stage heat exchanger, HE4-1—Fourth-stage heat exchanger, HE5—Fifth-stage heat exchanger, HE3-2—First-stage continuous converter, HE4-2—Second-stage continuous converter, HE6—Third-stage continuous converter, R2—Second-stage isothermal converter, V2—High-pressure throttling valve, V3—Medium-pressure throttling valve, D2—Medium-pressure gas-liquid separator, D3—Low-pressure gas-liquid separator, J—Ejector, V4—End throttling valve, D4—Product hydrogen-liquid mixture. Separator, C1—Feed Hydrogen Compressor Unit, C2—Low-Pressure Hydrogen Compressor Unit, C3—Medium-Pressure Hydrogen Compressor Unit, C4—Low-Pressure Nitrogen Compressor Unit, C5—Medium-Pressure Nitrogen Compressor Unit, C6—Propylene Compressor Unit, C7—Carbon Dioxide Compressor Unit, E1—High-Pressure Hydrogen Expander Unit, E2—Medium-Pressure Hydrogen Expander Unit, E3—High-Pressure Nitrogen Expander Unit, E4—Medium-Pressure Nitrogen Expander Unit, E5—Carbon Dioxide Expander Unit, S1—Circulating Hydrogen Low-Temperature Adsorber, S2—Feed Hydrogen Low-Temperature Adsorber, H1—First Channel, H2—Second Channel, H3—Third Channel, H4—Fourth Channel, H5—Fifth Channel, H6—Sixth Channel, H7—Seventh Channel, H8—Eighth Channel, H9—Ninth Channel, H10—Tenth Channel, H11—Tenth Channel Channel 1, H12—Twelfth channel, H13—Thirteenth channel, H14—Fourteenth channel, H15—Fifteenth channel, N1—First nitrogen channel, N2—Second nitrogen channel, N3—Third nitrogen channel, N4—Fourth nitrogen channel, N5—Fifth nitrogen channel, N6—Sixth nitrogen channel, N7—Seventh nitrogen channel, N8—Eighth nitrogen channel, N9—Ninth nitrogen channel, N10—Tenth nitrogen channel, N11—Eleventh nitrogen channel, N12—Twelfth nitrogen channel, N13—Thirteenth nitrogen channel, N14—Fourteenth nitrogen channel, N15—Fifteenth nitrogen channel, N16—Sixteenth nitrogen channel, N17—Seventeenth nitrogen channel, N18—Eighteenth nitrogen channel, N19—Nineteenth nitrogen channel, N20—Twentieth nitrogen channel, N21 —Nitrogen channel 21, N22—Nitrogen channel 22, A1—First hydrogen refrigeration channel, A2—Second hydrogen refrigeration channel, A3—Third hydrogen refrigeration channel, A4—Fourth hydrogen refrigeration channel, A5—Fifth hydrogen refrigeration channel, A6—Sixth hydrogen refrigeration channel, A7—Seventh hydrogen refrigeration channel, A8—Eighth hydrogen refrigeration channel, A9—Ninth hydrogen refrigeration channel, A10—Tenth hydrogen refrigeration channel, A11—Eleventh hydrogen refrigeration channel, A12—Twelfth hydrogen refrigeration channel, A13—Thirteenth hydrogen refrigeration channel, A14—Fourteenth hydrogen refrigeration channel, A15—Fifteenth hydrogen refrigeration channel, A16—Sixteenth hydrogen refrigeration channel, A17—Seventeenth hydrogen refrigeration channel, A18—Eighteenth hydrogen refrigeration channel, A19—Nineteenth hydrogen refrigeration channelA20—Twentieth hydrogen refrigeration channel, A21—Twenty-first hydrogen refrigeration channel, A22—Twenty-second hydrogen refrigeration channel, A23—Twenty-third hydrogen refrigeration channel, A24—Twenty-fourth hydrogen refrigeration channel, A25—Twenty-fifth hydrogen refrigeration channel, A26—Twenty-sixth hydrogen refrigeration channel, A27—Twenty-seventh hydrogen refrigeration channel, A28—Twenty-eighth hydrogen refrigeration channel, A29—Twenty-ninth hydrogen refrigeration channel, A30—Thirtieth hydrogen refrigeration channel, A31—Thirty-first hydrogen refrigeration channel, A32—Thirty-second hydrogen refrigeration channel, A33—Thirty-third hydrogen refrigeration channel, A34—Thirty-fourth hydrogen refrigeration channel, A35—Thirty-fifth hydrogen refrigeration channel, A36—Thirty-sixth hydrogen refrigeration channel, A37—Thirty-seventh hydrogen refrigeration channel, A38—Thirty-eighth hydrogen refrigeration channel, A39—Thirty-ninth hydrogen refrigeration channel, A40—Fortieth hydrogen refrigeration channel, A41—Forty-first hydrogen refrigeration channel, A42—Forty-second hydrogen refrigeration channel. Detailed Implementation
[0035] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly, provided that there is no mutual conflict.
[0036] like Figure 1 As shown, this invention provides a hydrogen liquefaction system employing cascade refrigeration and a split-type continuous converter. The system includes an atmospheric pressure compressor unit, a precooling cold box, a cryogenic cold box, an expander unit, an external cryogenic adsorber, a gas-liquid separator group, and a liquid hydrogen storage tank, all interconnected by pipelines. The precooling cold box contains a primary heat exchanger HE1, a secondary heat exchanger HE2, an internal cryogenic adsorber S3, a primary isothermal converter R1, a nitrogen throttling valve V1, a nitrogen-liquid separator D1, a nitrogen-propylene heat exchanger HE7, a propylene throttling valve V5, and a propylene-carbon dioxide heat exchanger HE8. The cryogenic chamber contains a three-stage heat exchanger HE3-1, a four-stage heat exchanger HE4-1, a five-stage heat exchanger HE5, a first-stage continuous converter HE3-2, a second-stage continuous converter HE4-2, a third-stage continuous converter HE6, a second-stage isothermal converter R2, a high-pressure throttling valve V2, a medium-pressure throttling valve V3, a medium-pressure gas-liquid separator D2, a low-pressure gas-liquid separator D3, an ejector J, a terminal throttling valve V4, and a product hydrogen-liquid separator D4. The compressor units include a feedstock hydrogen compressor unit C1, a low-pressure hydrogen compressor unit C2, a medium-pressure hydrogen compressor unit C3, a low-pressure nitrogen compressor unit C4, a medium-pressure nitrogen compressor unit C5, a propylene compressor unit C6, and a carbon dioxide compressor unit C7. The expander units include a high-pressure hydrogen expander unit E1, a medium-pressure hydrogen expander unit E2, a high-pressure nitrogen expander unit E3, a medium-pressure nitrogen expander unit E4, and a carbon dioxide expander unit E5. The cold box external low-temperature adsorber includes a circulating hydrogen low-temperature adsorber S1 and a raw material hydrogen low-temperature adsorber S2.
[0037] The precooling section of this hydrogen liquefaction system uses cascade refrigeration assisted nitrogen cycle precooling, and the cryogenic section uses a modified dual-pressure hydrogen cycle refrigeration. The specific connection method is as follows: Figure 1 As shown.
[0038] Feed hydrogen enters feed hydrogen compressor unit C1 through the first pipe H1. The outlet of feed hydrogen compressor unit C1 is connected to the first hot-side inlet of the first-stage heat exchanger HE1 through the second pipe H2. The first hot-side outlet of the first-stage heat exchanger HE1 is connected to the inlet of the feed hydrogen cryogenic adsorber S2 through the third pipe H3. The outlet of the feed hydrogen cryogenic adsorber S2 is connected to the first hot-side inlet of the second-stage heat exchanger through the fourth pipe H4. The first hot-side outlet of the second-stage heat exchanger is connected to the inlet of the cryogenic adsorber S3 in the cold box through the fifth pipe H5. The outlet of the cryogenic adsorber S3 in the cold box is connected to the tube-side inlet of the first-stage isothermal converter R1 through the sixth pipe H6. The tube-side outlet of the first-stage isothermal converter R1 is connected to the hot-side inlet of the first-stage continuous converter HE3-2 through the seventh pipe H7. The hot-side outlet of the first-stage continuous converter HE3-2 is connected to the hot-side inlet of the second-stage continuous converter HE4-2 through the eighth pipe H8. The hot-side outlet of the second-stage continuous converter HE4-2 is connected to the first hot-side inlet of the fifth-stage heat exchanger HE5 through the ninth pipe H9. The first hot-side outlet of the five-stage heat exchanger HE5 is connected to the tube-side inlet of the second-stage isothermal converter R2 via the tenth pipe HE10. The tube-side outlet of the second-stage isothermal converter R2 is connected to the inlet of ejector J via the eleventh pipe H11. The outlet of ejector J is connected to the hot-side inlet of the third-stage continuous converter HE6 via the twelfth pipe H12. The hot-side outlet of the third-stage continuous converter HE6 is connected to the product hydrogen-liquid separator D4 via the thirteenth pipe H13, the end throttle valve V4, and the fourteenth pipe H14. The bottom of the product hydrogen-liquid separator D4 is connected to a liquid hydrogen storage tank, forming a flow pipeline for the entire process from raw material hydrogen to liquid hydrogen. In this embodiment, the gas phase outlet of the product hydrogen-liquid separator D4 merges with the hydrogen evaporated from the liquid hydrogen storage tank via the fifteenth channel H15 and then enters ejector J to recover hydrogen.
[0039] The precooling section of this hydrogen liquefaction system uses propylene pressure cycle refrigeration and carbon dioxide cycle refrigeration in a cascade refrigeration system to assist nitrogen cycle precooling, which can reduce the overall energy consumption of the hydrogen liquefaction system.
[0040] The cryogenic section employs an improved dual-pressure hydrogen cycle refrigeration system, in which the first-stage continuous converter HE3-2 is separated from the third-stage heat exchanger HE3, and the second-stage continuous converter HE4-2 is separated from the fourth-stage heat exchanger HE4, forming a separate continuous converter. This bypasses the complex design and manufacturing challenges of filling catalysts in multi-flow plate-fin heat exchangers, and also facilitates catalyst replacement and component replacement in case of damage.
[0041] The nitrogen cycle precooling uses nitrogen from the air separation unit as the refrigerant. The outlet of the medium-pressure nitrogen compressor unit C5 is connected to the nitrogen inlet of the nitrogen-propylene heat exchanger HE7 via the first nitrogen channel N1. The nitrogen outlet of the nitrogen-propylene heat exchanger HE7 is connected to the inlet of the second nitrogen channel N2. The outlet of the second nitrogen channel N2 has two branches: the third nitrogen channel N3 and the fourth nitrogen channel N4.
[0042] The outlet of the fourth nitrogen channel N4 is connected to the inlet of the high-pressure nitrogen expander unit E3. The outlet of the high-pressure nitrogen expander unit E3 is connected to the secondary heat exchanger HE2 through the fifth nitrogen channel N5. After being expanded by the high-pressure nitrogen expander unit E3, the fourth nitrogen channel N4 enters the secondary heat exchanger HE2 as the fifth nitrogen channel N5 to provide cooling capacity. Subsequently, it is connected to the pipeline between the low-pressure nitrogen compressor unit C4 and the medium-pressure nitrogen compressor unit C5 through the sixth nitrogen channel N6.
[0043] The outlet of the third nitrogen channel N3 is connected to the second nitrogen inlet of the secondary heat exchanger HE2. Within HE2, the nitrogen splits into two branches. One branch enters the medium-pressure nitrogen expander E4 via the seventh nitrogen channel N7 and then connects to the inlet of the eighth nitrogen channel N8. The other branch sequentially passes through the second nitrogen outlet of HE2, the ninth nitrogen channel N9, the nitrogen throttling valve V1, and the tenth nitrogen channel N10 for throttling and cooling before connecting to the nitrogen-liquid separator D1. The liquid phase enters the twelfth nitrogen channel N12, and the gas phase enters the eleventh nitrogen channel N11. The liquid nitrogen in the twelfth nitrogen channel N12 flows into two separate streams: the thirteenth nitrogen channel N13 and the fifteenth nitrogen channel N15. The outlets of the thirteenth and fifteenth nitrogen channels N13 and N15 are connected to the shell-side inlet of the first-stage isothermal converter R1 and the liquid nitrogen inlet of the cryogenic adsorber S3 in the cold box, respectively.
[0044] Nitrogen gas, heated and vaporized from the shell-side outlet of the primary isothermal converter R1 and the nitrogen outlet of the cryogenic adsorber S3 in the cold box, enters the fourteenth nitrogen channel N14 and the sixteenth nitrogen channel N16, respectively. The outlets of the fourteenth nitrogen channel N14, the sixteenth nitrogen channel N16, the eighth nitrogen channel N8, and the eleventh nitrogen channel N11 (connected to the nitrogen outlet of the nitrogen-liquid separator D1) converge into the seventeenth nitrogen channel N17. The outlet of the seventeenth nitrogen channel N17 connects to the first nitrogen inlet of the secondary heat exchanger HE2. The first nitrogen outlet of the secondary heat exchanger HE2 connects to the nitrogen inlet of the primary heat exchanger HE1 via the nineteenth nitrogen channel N19. The nitrogen outlet of the primary heat exchanger HE1 connects to the inlet of the twenty-first nitrogen channel N21.
[0045] An eighteenth nitrogen channel N18 is also provided at the outlet of the eighth nitrogen channel N8. The outlet of the eighteenth nitrogen channel N18 is connected to the secondary heat exchanger HE2 and then exits through the twentieth nitrogen channel N20. The nitrogen channels N20 and N21 converge and then connect to the twenty-second nitrogen channel N22, which in turn connects to the low-pressure nitrogen compressor unit C4 and the medium-pressure nitrogen compressor unit C5, forming a nitrogen circulation precooling system.
[0046] Cascade refrigeration employs propylene and carbon dioxide (CO2) cycles. The CO2 cycle uses pure CO2 as the refrigerant, compressed by CO2 compressor unit C7 and expanded by CO2 expander unit E5 to provide cooling for the propylene cycle. The propylene-CO2 heat exchanger HE8 receives the cooling energy from the CO2 compression by CO2 compressor unit C7 and the expansion by CO2 expander unit E5. The propylene cycle uses pure propylene as the refrigerant, compressed by propylene compressor unit C6, cooled by propylene-CO2 heat exchanger HE8, and throttled by propylene expansion valve V5. In the nitrogen-propylene heat exchanger HE7, the temperature of the first nitrogen channel N1 (298 K) in the nitrogen cycle is reduced to 225 K in the second nitrogen channel N2, thus constituting cascade refrigeration.
[0047] The improved dual-pressure hydrogen cycle refrigeration system uses raw hydrogen as the refrigerant. The inlet of the first pipe H1 is connected to external raw hydrogen, and the outlet of the first pipe H1 is connected to the inlet of the raw hydrogen compressor unit C1. The outlet of the raw hydrogen compressor unit C1 is connected to the inlet of the medium-pressure hydrogen compressor unit C3 through the first hydrogen refrigeration channel A1. The outlet of the medium-pressure hydrogen compressor unit C3 is connected to the second hot-side inlet of the first-stage heat exchanger HE1 through the second hydrogen refrigeration channel A2. The second hot-side outlet of the first-stage heat exchanger HE1 is connected to the inlet of the circulating hydrogen cryogenic adsorber S1 through the third hydrogen refrigeration channel A3. The outlet of the circulating hydrogen cryogenic adsorber S1 is connected to the second hot-side inlet of the second-stage heat exchanger HE2 through the fourth hydrogen refrigeration channel A4. The second hot-side outlet of the second-stage heat exchanger HE2 is connected to the inlet of the fifth hydrogen refrigeration channel A5, and the outlet of the fifth hydrogen refrigeration channel A5 is connected to the inlets of the sixth hydrogen refrigeration channel A6 and the seventh hydrogen refrigeration channel A7. The outlet of the sixth hydrogen refrigeration channel A6 is connected to the hot-side inlet of the third-stage heat exchanger HE3-1. The hot-side outlet of the third-stage heat exchanger HE3-1 is connected to the hot-side inlet of the fourth-stage heat exchanger HE4-1 via the ninth hydrogen refrigeration channel A9. The hot-side outlet of the fourth-stage heat exchanger HE4-1 is connected to the inlet of the tenth hydrogen refrigeration channel A10. The outlet of the tenth hydrogen refrigeration channel A10 is connected to the eleventh hydrogen refrigeration channel A11 and the twelfth hydrogen refrigeration channel A12. The outlet of the eleventh hydrogen refrigeration channel A11 is connected to the second hot-side inlet of the fifth-stage heat exchanger HE5. The second hot-side outlet of the fifth-stage heat exchanger HE5 is connected to the inlet of the medium-pressure gas-liquid separator D2 via the fourteenth hydrogen refrigeration channel A14 and the fifteenth hydrogen refrigeration channel A15. The gas phase outlet of the medium-pressure gas-liquid separator D2 is connected to the inlet of the sixteenth hydrogen refrigeration channel A16. The bottom liquid phase outlet of the medium-pressure gas-liquid separator D2 is equipped with a seventeenth hydrogen refrigeration channel A17 and an eighteenth hydrogen refrigeration channel A18. The seventeenth hydrogen refrigeration channel A17 is connected to the shell-side inlet of the second-stage isothermal converter R2, and the shell-side outlet of the second-stage isothermal converter R2 is connected to the inlet of the twenty-fourth hydrogen refrigeration channel A24. The bottom outlet of the medium-pressure gas-liquid separator D2 is connected to the inlet of the low-pressure gas-liquid separator D3 via the eighteenth hydrogen refrigeration channel A18 and the nineteenth hydrogen refrigeration channel A19. The liquid phase outlet of the low-pressure gas-liquid separator D3 is connected to the cold-side inlet of the three-stage continuous converter HE6 via the twenty-first hydrogen refrigeration channel A21, and the cold-side outlet of the three-stage continuous converter HE6 is connected to the inlet of the twenty-second hydrogen refrigeration channel A22. The gas phase outlet of the low-pressure gas-liquid separator D3 is connected to the inlet of the twentieth hydrogen refrigeration channel A20. The outlets of the twentieth hydrogen refrigeration channel A20 and the twenty-second hydrogen refrigeration channel A22 converge at the inlet of the twenty-third hydrogen refrigeration channel A23, and are connected to the first cold side inlet of the five-stage heat exchanger HE5 through the twenty-third hydrogen refrigeration channel A23.The first cold-side outlet of the fifth-stage heat exchanger HE5 is connected to the first cold-side inlet of the fourth-stage heat exchanger HE4-1 via the twenty-seventh hydrogen refrigeration channel A27. The first cold-side outlet of the fourth-stage heat exchanger HE4-1 is connected to the first cold-side inlet of the third-stage heat exchanger HE3-1 via the thirty-first hydrogen refrigeration channel A31. The first cold-side outlet of the third-stage heat exchanger HE3-1 is connected to the first cold-side inlet of the second-stage heat exchanger HE2 via the thirty-eighth hydrogen refrigeration channel A38. The first cold-side outlet of the second-stage heat exchanger HE2 is connected to the first cold-side inlet of the first-stage heat exchanger HE1 via the fortieth hydrogen refrigeration channel A40. The first cold-side outlet of the first-stage heat exchanger HE1 is connected to the low-pressure hydrogen compressor unit C2 via the forty-second hydrogen refrigeration channel A42.
[0048] The outlet of the seventh hydrogen refrigeration channel A7 is connected to the inlet of the high-pressure hydrogen expander unit E1, and the outlet of the high-pressure hydrogen expander unit E1 is connected to the inlet of the eighth hydrogen refrigeration channel A8.
[0049] The outlet of the twelfth hydrogen refrigeration channel A12 is connected to the inlet of the medium-pressure hydrogen expander unit E2, and the outlet of the medium-pressure hydrogen expander unit E2 is connected to the inlet of the thirteenth hydrogen refrigeration channel A13. The outlets of the thirteenth hydrogen refrigeration channel A13, the twenty-fourth hydrogen refrigeration channel A24, and the sixteenth hydrogen refrigeration channel A16 converge and connect to the inlet of the twenty-fifth hydrogen refrigeration channel A25. The outlet of the twenty-fifth hydrogen refrigeration channel A25 is connected to the second cold-side inlet of the fifth-stage heat exchanger HE5, and the second cold-side outlet of the fifth-stage heat exchanger HE5 is connected to the inlet of the twenty-sixth hydrogen refrigeration channel A26. The outlet of the twenty-sixth hydrogen refrigeration channel A26 is connected to the inlet of the twenty-eighth hydrogen refrigeration channel A28 and the twenty-ninth hydrogen refrigeration channel A29. The outlet of the twenty-ninth hydrogen refrigeration channel A29 is connected to the cold-side inlet of the second-stage continuous converter HE4-2, and the cold-side outlet of the second-stage continuous converter HE4-2 is connected to the inlet of the thirty-second hydrogen refrigeration channel A32. The outlet of the 28th hydrogen refrigeration channel A28 is connected to the second cold-side inlet of the fourth-stage heat exchanger HE4-1. The second cold-side outlet of the fourth-stage heat exchanger HE4-1 is connected to the inlet of the 30th hydrogen refrigeration channel A30. The outlets of the 30th hydrogen refrigeration channel A30, the 8th hydrogen refrigeration channel A8, and the 32nd hydrogen refrigeration channel A32 converge at the inlet of the 33rd hydrogen refrigeration channel A33. The outlet of the 33rd hydrogen refrigeration channel A33 is connected to the second cold-side inlet of the third-stage heat exchanger HE3-1, and after reheating, it exits through the 35th hydrogen refrigeration channel A35.
[0050] A branch, the 34th hydrogen refrigeration channel A34, is installed on the 33rd hydrogen refrigeration channel A33. The outlet of the 34th hydrogen refrigeration channel A34 is connected to the cold-side inlet of the first-stage continuous converter HE3-2. The cold-side outlet of the first-stage continuous converter HE3-2 is connected to the inlet of the 36th hydrogen refrigeration channel A36. The outlet of the 36th hydrogen refrigeration channel A36 and the outlet of the 35th hydrogen refrigeration channel A35 converge and connect to the inlet of the 37th hydrogen refrigeration channel A37. The outlet of the 37th hydrogen refrigeration channel A37 is connected to the second cold-side inlet of the second-stage heat exchanger HE2. The second cold-side outlet of the second-stage heat exchanger HE2 is connected to the second cold-side inlet of the first-stage heat exchanger HE1 via the 39th hydrogen refrigeration channel A39. The second cold-side outlet of the first-stage heat exchanger HE1 is connected to the medium-pressure hydrogen compressor unit C3 via the 41st hydrogen refrigeration channel A41, forming an improved dual-pressure hydrogen cycle refrigeration system.
[0051] In this embodiment, the first-stage isothermal converter R1 and the second-stage isothermal converter R2 are tubular fixed-bed reactors, in which the feed hydrogen flows through the tube side and the refrigerant flows through the shell side. The tube side is filled with a corresponding catalytic performance for the conversion of n- and para-n-hydrogen according to the cooling temperature zone. The first-stage continuous converter HE3-2, the second-stage continuous converter HE4-2, and the third-stage continuous converter HE6 are aluminum plate-fin heat exchangers, in which the feed hydrogen channel is filled with a corresponding catalytic performance for the conversion of n- and para-n-hydrogen according to the cooling temperature zone.
[0052] To prevent impurities such as carbon dioxide, methane, and nitrogen in the product hydrogen from freezing and clogging during the cooling process, the circulating hydrogen cryogenic adsorber S1 and the raw material hydrogen cryogenic adsorber S2 are filled with molecular sieves to remove impurities that are prone to freezing and clogging in the cryogenic channel.
[0053] A specific method for using a hydrogen liquefaction system employing cascade refrigeration and a split-type continuous converter is as follows:
[0054] (1) After the raw material hydrogen is compressed to 6 MPa through low-temperature methanol washing and pressure swing adsorption process, it enters the liquefaction system and a stream is separated as the hydrogen source for the improved dual-pressure hydrogen cycle refrigeration in the liquefaction system. The compressed product hydrogen is first cooled by the first-stage heat exchanger HE1 in the pre-cooling box and then enters the raw material hydrogen low-temperature adsorber S2 to remove impurities such as carbon dioxide and methane that are prone to freezing and clogging in the subsequent low-temperature channel. Then it is cooled by the second-stage heat exchanger HE2 and enters the low-temperature adsorber S3 in the cold box to further remove nitrogen and other impurities. The purified hydrogen from the low-temperature adsorber S3 in the cold box enters the first-stage isothermal converter R1 for cooling, while the secondary hydrogen content is increased from 25% to more than 45%. The product hydrogen then exits the pre-cooling box.
[0055] (2) The product hydrogen from the pre-cooling box passes through the first-stage continuous converter HE3-2 and the second-stage continuous converter HE4-2 in sequence to cool down and increase the secondary hydrogen content to more than 82%. Then it enters the fifth-stage heat exchanger HE5 for cooling. The product hydrogen from the fifth-stage heat exchanger HE5 enters the second-stage isothermal converter R2 to increase the secondary hydrogen content to more than 93%. The product hydrogen then passes through the ejector J and enters the third-stage continuous converter HE6 for cooling down and increasing the secondary hydrogen content to more than 98%. Finally, after end throttling and gas-liquid separation, liquid hydrogen is obtained and enters the storage tank.
[0056] The hydrogen liquefaction system provided in this embodiment includes an atmospheric pressure precooling box, a vacuum cryogenic box, a cryogenic adsorber, a compressor unit, a gas-liquid separator group, and an expander unit. The precooling section uses propylene / carbon dioxide cascade refrigeration assisted by a nitrogen cycle, with a cooling temperature range of 298 K to 83.5 K; the cryogenic section uses a modified dual-pressure hydrogen cycle refrigeration, with a cooling temperature range of 83.5 K to 25 K. The raw material hydrogen is liquefied after being cooled in a multi-stage heat exchanger, reacted in a multi-stage ortho- and para-hydrogen converter, and throttled by a terminal throttling valve. In the above system, the product hydrogen channel of the plate-fin heat exchanger is filled with an ortho- and para-hydrogen conversion catalyst and separated from the main heat exchanger, achieving a para-hydrogen content of not less than 98% in the liquid hydrogen product. The system can produce 13-25 tons of liquefied hydrogen per day, with a specific energy consumption of no more than 9.5 kWh / kg liquid hydrogen. This hydrogen liquefaction system has low energy consumption; the precooling box and cryogenic box adopt different design schemes, and the continuous converter is separated from the main heat exchanger, reducing operating costs, equipment costs, and maintenance costs.
[0057] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.
Claims
1. A hydrogen liquefaction system employing cascade refrigeration and a split-type continuous converter, characterized in that, The system includes a compressor unit, a precooling cold box, a cryogenic cold box, a heat exchanger unit, an expander unit, an external cryogenic adsorber for the cold box, a gas-liquid separator unit, and a liquid hydrogen storage tank. The compressor unit includes a feedstock hydrogen compressor unit (C1), a low-pressure nitrogen compressor unit (C4), a medium-pressure nitrogen compressor unit (C5), a propylene compressor unit (C6), and a carbon dioxide compressor unit (C7). The precooling cold box contains a primary heat exchanger (HE1), a secondary heat exchanger (HE2), an internal cryogenic adsorber (S3), and a primary isothermal converter (R1). The cryogenic cold box contains a tertiary heat exchanger (HE3-). 1) Four-stage heat exchanger (HE4-1), five-stage heat exchanger (HE5), first-stage continuous converter (HE3-2), second-stage continuous converter (HE4-2), third-stage continuous converter (HE6), second-stage isothermal converter (R2), ejector (J), and product hydrogen-liquid separator (D4); expander units include high-pressure hydrogen expander (E1), medium-pressure hydrogen expander (E2), high-pressure nitrogen expander (E3), medium-pressure nitrogen expander (E4), and carbon dioxide expander (E5); cold box external cryogenic adsorber includes feedstock hydrogen cryogenic adsorber (S2); Raw hydrogen from the outside is pressurized by the raw hydrogen compressor unit (C1) and separated into two streams: circulating hydrogen and raw hydrogen. The raw hydrogen enters a pre-cooling box and undergoes cooling, adsorption purification, and conversion of n- and para-hydrogen to obtain pre-cooled raw hydrogen. The circulating hydrogen enters a pre-cooling box and undergoes cooling and adsorption purification to obtain pre-cooled circulating hydrogen. The cryogenic box receives the pre-cooled raw hydrogen and pre-cooled circulating hydrogen from the pre-cooling box. The pre-cooled raw hydrogen undergoes further cooling and conversion of n- and para-hydrogen to obtain liquid hydrogen product. The specific structure of this system is as follows: External feedstock hydrogen is connected to the inlet of the first pipeline (H1), and the outlet of the first pipeline (H1) is connected to the inlet of the feedstock hydrogen compressor unit (C1). The outlet of the feedstock hydrogen compressor unit (C1) has two branches: a first hydrogen refrigeration channel (A1) and a second pipeline (H2). The second pipeline (H2) is connected to the first hot-side inlet of the first-stage heat exchanger (HE1), and the first hot-side outlet of the first-stage heat exchanger (HE1) is connected to the inlet of the feedstock hydrogen cryogenic adsorber (S2) via the third pipeline (H3). The outlet of the feedstock hydrogen cryogenic adsorber (S2) is connected to the first hot-side inlet of the second-stage heat exchanger (HE2) via the fourth pipeline (H4). The first hot-side outlet of the second-stage heat exchanger (HE2) is connected to the inlet of the cryogenic adsorber (S3) inside the cold box via the fifth pipeline (H5). The outlet of the cryogenic adsorber (S3) inside the cold box is connected to the tube-side inlet of the first-stage isothermal converter (R1) via the sixth pipeline (H6). The tube-side outlet of the first-stage isothermal converter (R1) is connected to the first-stage isothermal converter (R1) via the seventh pipeline (H7). The hot-side inlet of the continuous converter (HE3-2) is connected; the hot-side outlet of the first-stage continuous converter (HE3-2) is connected to the hot-side inlet of the second-stage continuous converter (HE4-2) via the eighth pipe (H8); the hot-side outlet of the second-stage continuous converter (HE4-2) is connected to the first hot-side inlet of the fifth-stage heat exchanger (HE5) via the ninth pipe (H9); the first hot-side outlet of the fifth-stage heat exchanger (HE5) is connected to the tube of the second-stage isothermal converter (R2) via the tenth pipe (HE10). The tube side outlet of the second-stage isothermal converter (R2) is connected to the inlet of the ejector (J) via the eleventh pipe (H11); the outlet of the ejector (J) is connected to the hot-side inlet of the third-stage continuous converter (HE6) via the twelfth pipe (H12); the hot-side outlet of the third-stage continuous converter (HE6) is connected to the product hydrogen-liquid separator (D4) via the thirteenth pipe (H13) and the fourteenth pipe (H14) in sequence; the bottom of the product hydrogen-liquid separator (D4) is connected to a liquid hydrogen storage tank. The low-pressure nitrogen compressor unit (C4), medium-pressure nitrogen compressor unit (C5), high-pressure nitrogen expander unit (E3), and medium-pressure nitrogen expander unit (E4) are connected to the equipment inside the pre-cooling box via pipelines to form a nitrogen circulation pre-cooling system; the propylene compressor unit (C6), carbon dioxide compressor unit (C7), and carbon dioxide expander unit (E5) are connected to the equipment inside the pre-cooling box via pipelines to form a cascade refrigeration system, providing cooling capacity for the circulating nitrogen in the pre-cooling box; The high-pressure hydrogen expander (E1) and the medium-pressure hydrogen expander (E2) are respectively connected to the equipment inside the cryogenic box through pipelines, forming an improved dual-pressure hydrogen cycle refrigeration system to provide cooling capacity for the cryogenic box; wherein the first-stage continuous converter (HE3-2) is separated from the third-stage heat exchanger (HE3-1), and the second-stage continuous converter (HE4-2) is separated from the fourth-stage heat exchanger (HE4-1), forming a separate continuous converter; The gas phase outlet of the product hydrogen-liquid separator (D4) merges with the hydrogen evaporated from the liquid hydrogen storage tank through the fifteenth channel (H15) and then enters the ejector (J) to recover hydrogen.
2. The hydrogen liquefaction system according to claim 1, characterized in that, The specific structure of the nitrogen cycle precooling is as follows: The outlet of the medium-pressure nitrogen compressor unit (C5) is connected to the nitrogen inlet of the nitrogen-propylene heat exchanger (HE7) through the first nitrogen channel (N1); the nitrogen outlet of the nitrogen-propylene heat exchanger (HE7) is connected to the inlet of the second nitrogen channel (N2), and the outlet of the second nitrogen channel (N2) is provided with two branches: the third nitrogen channel (N3) and the fourth nitrogen channel (N4). The outlet of the third nitrogen channel (N3) is connected to the second nitrogen inlet of the secondary heat exchanger (HE2), and splits into two branches in the secondary heat exchanger (HE2). One branch connects to the nitrogen-liquid separator (D1) via the second nitrogen outlet, the ninth nitrogen channel (N9), and the tenth nitrogen channel (N10) of the secondary heat exchanger (HE2); the other branch enters the medium-pressure nitrogen expander (E4) via the seventh nitrogen channel (N7). The liquid nitrogen outlet of the nitrogen-liquid separator (D1) is connected to the tenth nitrogen inlet. The inlet of the twelfth nitrogen channel (N12) is connected to the inlet of the twelfth nitrogen channel (N12), and the outlet of the thirteenth nitrogen channel (N13) and the fifteenth nitrogen channel (N15) are provided. The outlet of the thirteenth nitrogen channel (N13) and the outlet of the fifteenth nitrogen channel (N15) are respectively connected to the shell-side inlet of the first-stage isothermal converter (R1) and the liquid nitrogen inlet of the cryogenic adsorber (S3) in the cold box. The outlet of the medium-pressure nitrogen expander unit (E4) is connected to the inlet of the eighth nitrogen channel (N8). The shell-side outlet of the primary isothermal converter (R1) and the nitrogen outlet of the cryogenic adsorber (S3) in the cold box are respectively connected to the inlets of the fourteenth nitrogen channel (N14) and the sixteenth nitrogen channel (N16); the outlets of the fourteenth nitrogen channel (N14), the sixteenth nitrogen channel (N16), the eighth nitrogen channel (N8), and the eleventh nitrogen channel (N11) leading from the nitrogen outlet of the nitrogen-liquid separator (D1) converge into the seventeenth nitrogen channel (N17); the outlet of the seventeenth nitrogen channel (N17) is connected to the first nitrogen inlet of the secondary heat exchanger (HE2), and the first nitrogen outlet of the secondary heat exchanger (HE2) is connected to the nitrogen inlet of the primary heat exchanger (HE1) through the nineteenth nitrogen channel (N19); the nitrogen outlet of the primary heat exchanger (HE1) is connected to the inlet of the twenty-first nitrogen channel (N21); The outlet of the fourth nitrogen channel (N4) is connected to the inlet of the high-pressure nitrogen expander (E3). The outlet of the high-pressure nitrogen expander (E3) is connected to the secondary heat exchanger (HE2) through the fifth nitrogen channel (N5), and then connected to the pipeline between the low-pressure nitrogen compressor unit (C4) and the medium-pressure nitrogen compressor unit (C5) through the sixth nitrogen channel (N6). The outlet of the eighth nitrogen channel (N8) is also provided with an eighteenth nitrogen channel (N18). The outlet of the eighteenth nitrogen channel (N18) is connected to the secondary heat exchanger (HE2) and then exits through the twentieth nitrogen channel (N20). The twentieth nitrogen channel (N20) and the twenty-first nitrogen channel (N21) converge into the twenty-second nitrogen channel (N22) and then connect to the low-pressure nitrogen compressor unit (C4) and the medium-pressure nitrogen compressor unit (C5) in sequence to form a nitrogen circulation precooling.
3. The hydrogen liquefaction system according to claim 2, characterized in that, The specific structure of the cascade cooling system is as follows: The cascade refrigeration includes propylene cycle refrigeration and carbon dioxide cycle refrigeration; the carbon dioxide cycle refrigeration consists of a carbon dioxide compressor unit (C7), a carbon dioxide expander unit (E5), and a propylene-carbon dioxide heat exchanger (HE8); the propylene-carbon dioxide heat exchanger (HE8) receives the cooling capacity provided by the carbon dioxide cycle refrigeration; the propylene cycle refrigeration consists of a propylene-carbon dioxide heat exchanger (HE8), a nitrogen-propylene heat exchanger (HE7), a propylene compressor unit (C6), and a propylene throttling valve (V5); the nitrogen-propylene heat exchanger (HE7) receives the cooling capacity provided by the propylene cycle refrigeration and provides cooling capacity for the precooling of the nitrogen cycle.
4. The hydrogen liquefaction system according to claim 3, characterized in that, The specific structure of the dual-pressure hydrogen cycle refrigeration is as follows: The first hydrogen refrigeration channel (A1) is connected to the inlet of the medium-pressure hydrogen compressor unit (C3). The outlet of the medium-pressure hydrogen compressor unit (C3) is connected to the second hot-side inlet of the first-stage heat exchanger (HE1) via the second hydrogen refrigeration channel (A2). The second hot-side outlet of the first-stage heat exchanger (HE1) is connected to the inlet of the circulating hydrogen cryogenic adsorber (S1) via the third hydrogen refrigeration channel (A3). The outlet of the circulating hydrogen cryogenic adsorber (S1) is connected to the second hot-side inlet of the second-stage heat exchanger (HE2) via the fourth hydrogen refrigeration channel (A4). The second hot-side outlet of the second-stage heat exchanger (HE2) is connected to the inlet of the fifth hydrogen refrigeration channel (A5). The outlet connects to the inlet of the sixth hydrogen refrigeration channel (A6) and the seventh hydrogen refrigeration channel (A7); the outlet of the sixth hydrogen refrigeration channel (A6) is connected to the hot-side inlet of the third-stage heat exchanger (HE3-1), and the hot-side outlet of the third-stage heat exchanger (HE3-1) is connected to the hot-side inlet of the fourth-stage heat exchanger (HE4-1) via the ninth hydrogen refrigeration channel (A9); the hot-side outlet of the fourth-stage heat exchanger (HE4-1) is connected to the inlet of the tenth hydrogen refrigeration channel (A10), and the outlet of the tenth hydrogen refrigeration channel (A10) is connected to the eleventh hydrogen refrigeration channel (A11) and the twelfth hydrogen refrigeration channel (A12); the outlet of the eleventh hydrogen refrigeration channel (A11) is connected to the inlet of the fifth-stage heat exchanger (H... The second hot-side inlet of the five-stage heat exchanger (HE5) is connected to the fourth hot-side outlet of the five-stage heat exchanger (HE5). The outlet of the fifth hot-side outlet of HE5 passes through the fourteenth hydrogen refrigeration channel (A14) and the high-pressure throttling valve (V2) for throttling and cooling before entering the fifteenth hydrogen refrigeration channel (A15). The outlet of the fifteenth hydrogen refrigeration channel (A15) is connected to the inlet of the medium-pressure gas-liquid separator (D2). The gas phase outlet of the medium-pressure gas-liquid separator (D2) is connected to the inlet of the sixteenth hydrogen refrigeration channel (A16). The bottom liquid phase outlet of the medium-pressure gas-liquid separator (D2) is respectively equipped with the seventeenth hydrogen refrigeration channel (A17) and the eighteenth hydrogen refrigeration channel (A18), wherein the seventeenth hydrogen refrigeration channel (A17) is connected to the second isothermal converter. The shell-side inlet of the reactor (R2) is connected, and the shell-side outlet of the second-stage isothermal converter (R2) is connected to the inlet of the twenty-fourth hydrogen refrigeration channel (A24); the bottom outlet of the medium-pressure gas-liquid separator (D2) passes through the eighteenth hydrogen refrigeration channel (A18) and the medium-pressure throttling valve (V3) for throttling and cooling before entering the nineteenth hydrogen refrigeration channel (A19), and then connects to the inlet of the low-pressure gas-liquid separator (D3); the liquid phase outlet of the low-pressure gas-liquid separator (D3) is connected to the cold-side inlet of the third-stage continuous converter (HE6) through the twenty-first hydrogen refrigeration channel (A21), and the cold-side outlet of the third-stage continuous converter (HE6) is connected to the inlet of the twenty-second hydrogen refrigeration channel (A22);The gas phase outlet of the low-pressure gas-liquid separator (D3) is connected to the inlet of the twentieth hydrogen refrigeration channel (A20). The outlets of the twentieth hydrogen refrigeration channel (A20) and the twenty-second hydrogen refrigeration channel (A22) converge at the inlet of the twenty-third hydrogen refrigeration channel (A23), which in turn connects to the first cold-side inlet of the fifth-stage heat exchanger (HE5). The first cold-side outlet of the fifth-stage heat exchanger (HE5) is connected to the first cold-side inlet of the fourth-stage heat exchanger (HE4-1) via the twenty-seventh hydrogen refrigeration channel (A27). The outlet is connected to the first cold-side inlet of the third-stage heat exchanger (HE3-1) via the thirty-first hydrogen refrigeration channel (A31); the first cold-side outlet of the third-stage heat exchanger (HE3-1) is connected to the first cold-side inlet of the second-stage heat exchanger (HE2) via the thirty-eighth hydrogen refrigeration channel (A38); the first cold-side outlet of the second-stage heat exchanger (HE2) is connected to the first cold-side inlet of the first-stage heat exchanger (HE1) via the fortieth hydrogen refrigeration channel (A40); and the first cold-side outlet of the first-stage heat exchanger (HE1) is connected to the low-pressure hydrogen compressor unit (C2) after being reheated via the forty-second hydrogen refrigeration channel (A42). The outlet of the seventh hydrogen refrigeration channel (A7) is connected to the inlet of the high-pressure hydrogen expander unit (E1), and the outlet of the high-pressure hydrogen expander unit (E1) is connected to the inlet of the eighth hydrogen refrigeration channel (A8). The outlet of the twelfth hydrogen refrigeration channel (A12) is connected to the inlet of the medium-pressure hydrogen expander (E2), and the outlet of the medium-pressure hydrogen expander (E2) is connected to the inlet of the thirteenth hydrogen refrigeration channel (A13). The outlets of the thirteenth hydrogen refrigeration channel (A13), the twenty-fourth hydrogen refrigeration channel (A24), and the sixteenth hydrogen refrigeration channel (A16) converge and connect to the inlet of the twenty-fifth hydrogen refrigeration channel (A25). The outlet of the twenty-fifth hydrogen refrigeration channel (A25) is connected to the second cold-side inlet of the fifth-stage heat exchanger (HE5), and after reheating, it exits through the twenty-sixth hydrogen refrigeration channel (A26). The outlet of the twenty-sixth hydrogen refrigeration channel (A26) is connected to the inlets of the twenty-eighth hydrogen refrigeration channel (A28) and the twenty-ninth hydrogen refrigeration channel (A29). The outlet of the twenty-ninth hydrogen refrigeration channel (A29) is connected to the second-stage continuous converter. The cold-side inlet of (HE4-2) is connected, and the cold-side outlet of the second-stage continuous converter (HE4-2) is connected to the inlet of the 32nd hydrogen refrigeration channel (A32); the outlet of the 28th hydrogen refrigeration channel (A28) is connected to the second cold-side inlet of the fourth-stage heat exchanger (HE4-1), and the second cold-side outlet of the fourth-stage heat exchanger (HE4-1) is connected to the inlet of the 30th hydrogen refrigeration channel (A30); the outlets of the 30th hydrogen refrigeration channel (A30), the 8th hydrogen refrigeration channel (A8), and the 32nd hydrogen refrigeration channel (A32) converge at the inlet of the 33rd hydrogen refrigeration channel (A33); the outlet of the 33rd hydrogen refrigeration channel (A33) is connected to the second cold-side inlet of the third-stage heat exchanger (HE3-1), and the second cold-side outlet of the third-stage heat exchanger (HE3-1) is connected to the inlet of the 35th hydrogen refrigeration channel (A35); A branch line, the 34th hydrogen refrigeration channel (A34), is provided on the 33rd hydrogen refrigeration channel (A33); the outlet of the 34th hydrogen refrigeration channel (A34) is connected to the cold-side inlet of the first-stage continuous converter (HE3-2); the cold-side outlet of the first-stage continuous converter (HE3-2) is connected to the inlet of the 36th hydrogen refrigeration channel (A36); the outlet of the 36th hydrogen refrigeration channel (A36) and the outlet of the 35th hydrogen refrigeration channel (A35) converge and connect to the inlet of the 37th hydrogen refrigeration channel (A37); the outlet of the 37th hydrogen refrigeration channel (A37) is connected to the second cold-side inlet of the second-stage heat exchanger (HE2); the second cold-side outlet of the second-stage heat exchanger (HE2) is connected to the second cold-side inlet of the first-stage heat exchanger (HE1) through the 39th hydrogen refrigeration channel (A39); the second cold-side outlet of the first-stage heat exchanger (HE1) is connected to the medium-pressure hydrogen compressor unit (C3) through the 41st hydrogen refrigeration channel (A41).
5. The hydrogen liquefaction system according to claim 4, characterized in that, The circulating hydrogen cryogenic adsorber (S1) and the raw material hydrogen cryogenic adsorber (S2) are filled with molecular sieves for removing impurities that are prone to freezing and clogging in the cryogenic channel.
6. The hydrogen liquefaction system according to claim 4, characterized in that, A nitrogen throttling valve (V1) is provided between the ninth nitrogen channel (N9) and the tenth nitrogen channel (N10); an end throttling valve (V4) is provided between the thirteenth pipe (H13) and the fourteenth pipe (H14); a high-pressure throttling valve (V2) is provided between the fourteenth hydrogen refrigeration channel (A14) and the fifteenth hydrogen refrigeration channel (A15); and a medium-pressure throttling valve (V3) is provided between the eighteenth hydrogen refrigeration channel (A18) and the nineteenth hydrogen refrigeration channel (A19).
7. The hydrogen liquefaction system according to claim 1, characterized in that, The first-stage isothermal converter (R1) and the second-stage isothermal converter (R2) are tubular fixed-bed reactors, in which the feed hydrogen is introduced into the tube side channel and the refrigerant is introduced into the shell side channel, and the tube side channel is filled with a corresponding catalytic performance of the positive and negative hydrogen conversion catalyst according to the cooling temperature zone.
8. The hydrogen liquefaction system according to claim 1, characterized in that, The first-stage continuous converter (HE3-2), the second-stage continuous converter (HE4-2), and the third-stage continuous converter (HE6) are aluminum plate-fin heat exchangers, wherein the feed hydrogen channels are filled with corresponding catalytic performance of the ortho- and para-hydrogen conversion catalyst according to the cooling temperature zone.
9. The hydrogen liquefaction system according to claim 1, characterized in that, The precooling box is an atmospheric pressure box, and the cryogenic box is a vacuum box.