A small hydrogen liquefaction device

Abstract

The present invention proposes a small hydrogen liquefaction device, including: a cold box and a hydrogen liquefaction box; the cold box has a hydrogen inlet, a hydrogen outlet, a liquid nitrogen inlet, and an exhaust port, wherein the hydrogen inlet is used to input raw hydrogen; a first-stage normal-parahydrogen converter is arranged inside the cold box; the hydrogen liquefaction box includes a vacuum cylinder and a liquid storage tank, a refrigerator and a condenser installed on the cold head of the refrigerator; a heat exchange tube is coiled on the cold head of the refrigerator, and the output end of the heat exchange tube is connected to the input end of the condenser; the hydrogen outlet of the cold box is connected to the input end of the heat exchange tube; the output end of the condenser is connected to the liquid storage tank via a second-stage normal-parahydrogen converter. The setting of the two-stage normal-parahydrogen converter in the present invention can effectively avoid the evaporation of liquid hydrogen and energy waste caused by heat release during storage, thereby realizing efficient and safe liquid hydrogen production, and the overall structure has high integration and small size.

Description

Technical Field

[0001] The present invention relates to the field of ultra-low temperature engineering and hydrogen application technology, and in particular to a small-scale hydrogen liquefaction device. Background Art

[0002] Liquid hydrogen has high energy density and low temperature characteristics, and is often used in fields such as rocket propulsion and space exploration. Hydrogen liquefaction refers to a series of processes and conditions that cool hydrogen to its liquefaction point and keep it in liquid form. Normally, hydrogen is a mixture of orthohydrogen (o-H2) and parahydrogen (p-H2). Orthohydrogen and parahydrogen are two spin isomers of molecular hydrogen. They have the same chemical properties but different physical properties. There is an energy difference between the two. During the liquefaction process, as the temperature changes, the equilibrium concentration of the orthohydrogen and parahydrogen mixture will change, that is, orthohydrogen will spontaneously convert to parahydrogen. The resulting liquid hydrogen is in a non-equilibrium state, which will lead to evaporation and loss of liquid hydrogen.

[0003] And due to the extremely low temperature and high pressure characteristics of liquid hydrogen, the safety requirements for storage and transportation facilities are relatively high. Therefore, in order to meet the demand for liquid hydrogen supply in the scientific research process and improve the preparation efficiency and liquefaction safety of liquid hydrogen, it is necessary to design a miniaturized hydrogen liquefaction equipment suitable for the supply of liquid hydrogen in the scientific research process. Summary of the invention

[0004] In order to solve the technical problems existing in the background technology, the present invention proposes a small-scale hydrogen liquefaction device.

[0005] The present invention provides a small-scale hydrogen liquefaction device, comprising: a cold box and a hydrogen liquefaction box;

[0006] The cold box has a hydrogen inlet, a hydrogen outlet, a liquid nitrogen inlet, and an exhaust port, wherein the hydrogen inlet is used to input raw hydrogen, the hydrogen outlet is used to output raw hydrogen, the liquid nitrogen inlet is used to input liquid nitrogen, and the exhaust port is used to discharge nitrogen formed by evaporation of internal liquid nitrogen; liquid nitrogen and a first-level normal-parahydrogen converter immersed in liquid nitrogen are installed inside the cold box, the first-level normal-parahydrogen converter includes a gas pipeline and a catalyst installed in the gas pipeline, the input end of the gas pipeline is connected to the hydrogen inlet of the cold box, and the output end of the gas pipeline is connected to the hydrogen outlet of the cold box;

[0007] The hydrogen liquefaction tank includes a vacuum cylinder with an internal vacuum pump, a liquid storage tank arranged inside the vacuum cylinder, a refrigerator installed on the top of the vacuum cylinder, and a condenser installed on the cold head of the refrigerator; a heat exchange tube is coiled on the cold head of the refrigerator, the condenser and the heat exchange tube are both located inside the vacuum cylinder, and the output end of the heat exchange tube is connected to the input end of the condenser;

[0008] The hydrogen outlet of the cold box is connected to the input end of the heat exchange tube via a delivery pipeline; the output end of the condenser is connected to the liquid storage tank via a secondary normal-parahydrogen converter.

[0009] Preferably, the gas transmission pipeline in the first-stage normal-parahydrogen converter is configured as a coil structure.

[0010] Preferably, the cold box is also provided with a sampling port, and the output end of the first-stage normal-parahydrogen converter is divided into two paths, one of which is connected to the hydrogen outlet and the other is connected to the sampling port.

[0011] Preferably, the cold box includes an outer cylinder, an inner cylinder located inside the outer cylinder, and a vacuum interlayer located between the outer cylinder and the inner cylinder; the first-stage normal-parahydrogen converter is arranged in the inner cylinder, and one or more groups of radiation shields and foam layers attached to the radiation shields are arranged inside the inner cylinder and above the first-stage normal-parahydrogen converter, the radiation shields and the foam layers are arranged on the top cover of the inner cylinder, and the top cover of the inner cylinder and the inner cylinder are detachably assembled; the input end and the output end of the first-stage normal-parahydrogen converter are respectively connected to the hydrogen inlet and the hydrogen outlet arranged on the top cover of the inner cylinder through the radiation shield and the foam layer.

[0012] Preferably, a return air pipe connecting the liquid storage tank and the condenser is provided between the two; a second sensor for detecting the start time of liquid accumulation inside the liquid storage tank is provided at the bottom of the liquid storage tank; the two-stage normal-parahydrogen converter includes a gas pipeline and a catalyst installed in the gas pipeline, one end of the gas pipeline is connected to the output end of the condenser, and the other end is connected to the liquid storage tank.

[0013] Preferably, the refrigerator adopts two-stage refrigeration, its cold head includes a primary cold head and a secondary cold head, the heat exchange tube includes a primary heat exchange tube coiled on the primary cold head and a secondary heat exchange tube coiled on the secondary cold head, and the primary heat exchange tube is connected to the secondary heat exchange tube.

[0014] Preferably, the refrigerator is provided with one or more groups, the delivery pipeline is divided into one or more branches, and each branch is connected to the heat exchange pipe in one group of refrigerators.

[0015] Preferably, a cold screen is provided inside the vacuum cylinder. The cold screen is a cylindrical structure, and a cold screen flange is installed on the top of the cold screen. The cold screen flange is fixed to the top cover of the vacuum cylinder through an upper suspension rod and is in contact with the cold head of the refrigerator. The liquid storage tank is located inside the cold screen and is suspended below the cold screen flange through a lower suspension rod.

[0016] Preferably, the condenser includes an outer cover shell and a condensing core arranged in the outer cover shell, the condensing core includes a plurality of fins arranged in a matrix, and the fins are a sheet structure formed at the angle where any longitudinal groove intersects with any transverse groove by processing a plurality of criss-cross grooves on the copper material.

[0017] Preferably, the hydrogen liquefaction tank also includes an infusion neck tube, the input end of the infusion neck tube is located inside the liquid storage tank, and the output end is located outside the vacuum cylinder, and the output end of the infusion neck tube is divided into multiple branches, one of which is used for vacuuming, one is used for taking liquid, one is used for connecting a pressure gauge, and another is used for installing a safety valve; the hydrogen liquefaction tank also includes a capacitive level gauge and a differential pressure gauge for detecting the liquid level inside the liquid storage tank.

[0018] Preferably, it also includes an explosion-proof positive pressure cabinet, which includes a cabinet body, electrical components installed inside the cabinet body, wiring holes opened on the cabinet body for lines to pass through and connect with corresponding electrical components, and a nitrogen delivery system for maintaining and obtaining positive pressure conditions inside the cabinet body; the tops of the cold box and the hydrogen liquefaction box are both provided with wiring ports, an explosion-proof box with the wiring masks covered inside, wiring holes opened on the explosion-proof box for lines to pass through, and a nitrogen delivery system for maintaining and obtaining positive pressure conditions inside the explosion-proof box.

[0019] In the present invention, a primary normal-para hydrogen converter is arranged inside the cold box, and a gas transmission pipeline in the primary normal-para hydrogen converter is connected to a hydrogen inlet and a hydrogen outlet respectively. The hydrogen liquefaction box is set to a vacuum cylinder structure with internal vacuum pumping, and its liquid storage tank and the secondary normal-para-hydrogen converter are set inside the vacuum cylinder, the refrigerator in the refrigeration assembly is installed on the top of the vacuum cylinder, the condenser is installed on the cold head of the refrigerator, the heat exchange tube is coiled on the cold head of the refrigerator, and the condenser and the heat exchange tube are set inside the vacuum cylinder, the output end of the heat exchange tube is connected to the input end of the condenser, the hydrogen outlet of the cold box is connected to the input end of the heat exchange tube via a transmission pipeline, and the output end of the condenser is connected to the liquid storage tank via the secondary normal-para-hydrogen converter, so that high-purity hydrogen enters the cold box after decompression, and the room temperature hydrogen is cooled to a preset temperature inside the cold box, and is converted by the primary normal-para-hydrogen converter and then transported to the hydrogen liquefaction box, so as to exchange heat with the cold head through the heat exchange tube coiled on the cold head of the refrigerator, and then enter the condenser to condense to form liquid hydrogen, and the condensed liquid hydrogen is converted by the secondary normal-para-hydrogen converter and then enters the liquid storage tank for storage. The device has high integration and small size. The two-stage normal-para hydrogen converter can complete the conversion of the spin state of hydrogen molecules during the liquefaction process, avoiding liquid hydrogen evaporation and energy waste due to heat release during storage, realizing efficient and safe liquid hydrogen production, and ensuring the hydrogen liquefaction rate. The structural setting of the vacuum cylinder can isolate the corresponding liquid storage tank and condenser in a vacuum environment without contact with the outside world, preventing liquid hydrogen from re-evaporating into hydrogen due to external heat during the storage and conversion process, thereby avoiding storage losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is an axonometric diagram of a small-scale hydrogen liquefaction device proposed by the present invention;

[0021] Figure 2A top view of a small-scale hydrogen liquefaction device proposed by the present invention;

[0022] Figure 3 A cross-sectional view of the cold box in a small-scale hydrogen liquefaction device proposed by the present invention;

[0023] Figure 4 This is a schematic diagram of the internal structure of the cold box in a small-scale hydrogen liquefaction device proposed by the present invention;

[0024] Figure 5 This is a schematic diagram of the installation of the first-stage normal-parahydrogen converter, radiation shield, foam layer and inner cylinder top cover in a small-scale hydrogen liquefaction device proposed by the present invention;

[0025] Figure 6 A cross-sectional view of the hydrogen liquefaction tank of a small hydrogen liquefaction device proposed by the present invention;

[0026] Figure 7 This is a schematic diagram of the internal structure of the hydrogen liquefaction box in a small hydrogen liquefaction device proposed by the present invention after removing the vacuum cylinder and the cold shield;

[0027] Figure 8 The present invention provides a schematic structural diagram of a condensing core in a small-scale hydrogen liquefaction device. DETAILED DESCRIPTION

[0028] Reference Figure 1-2 A small-scale hydrogen liquefaction device proposed in the present invention includes: a cold box 1, a hydrogen liquefaction box 2, an explosion-proof positive pressure cabinet 3, and a skid-mounted platform 4, and the explosion-proof positive pressure cabinet 3, the cold box 1, and the hydrogen liquefaction box 2 are all installed on the skid-mounted platform 4.

[0029] Reference Figure 3-4 A sensor 1 is provided inside the cold box 1 for real-time detection of its internal temperature. The cold box 1 has a hydrogen inlet, a hydrogen outlet, a liquid nitrogen inlet, an exhaust port, and a sampling port, wherein the hydrogen inlet is used to input raw hydrogen, the hydrogen outlet is used to output raw hydrogen, the liquid nitrogen inlet is used to input liquid nitrogen, and the exhaust port is used to discharge nitrogen formed by evaporation of internal liquid nitrogen.

[0030] The cold box 1 includes an outer cylinder 101, an inner cylinder 102 located inside the outer cylinder 101, and a vacuum interlayer 103 located between the outer cylinder 101 and the inner cylinder 102. The inner cylinder 102 is filled with liquid nitrogen and a first-level normal parahydrogen converter 5 immersed in liquid nitrogen. The first-level normal parahydrogen converter 5 includes a gas pipeline and a catalyst installed in the gas pipeline. The input end of the gas pipeline is connected to the hydrogen inlet of the cold box 1. The output end of the gas pipeline is divided into two paths, one of which is connected to the hydrogen outlet and the other is connected to the sampling port. During operation, hydrogen enters the first-level normal parahydrogen converter 5 from the hydrogen inlet to be converted using the catalyst in the first-level normal parahydrogen converter 5; while converting, the gas pipeline of the first-level normal parahydrogen converter 5 is used to exchange heat with the liquid nitrogen in the cold box 1, so that the normal temperature hydrogen is cooled to a preset temperature and then output from the hydrogen outlet, and the nitrogen generated by evaporation of the cold box 1 is discharged through the exhaust port. The sampling port can sample and detect at any time during the operation.

[0031] Reference Figure 5 In addition, one or more groups of radiation shields 7 and polyurethane foam layers 8 attached to the radiation shields 7 are arranged between the first-stage normal-parahydrogen converter 5 and the top cover of the inner tube 102 to reduce the radiation and convection heat leakage of the cold box 1. The radiation shield 7 and the foam layer 8 are installed on the top cover of the inner tube 102, and the hydrogen inlet and the hydrogen outlet are both arranged on the top cover of the inner tube 102. The top cover of the inner tube 102 and the inner tube 102 can be detachably assembled. The input end and the output end of the first-stage normal-parahydrogen converter 5 are respectively connected to the hydrogen inlet and the hydrogen outlet through the radiation shield 7 and the foam layer 8, so that the first-stage normal-parahydrogen converter 5 and the radiation shield 7 together with the foam layer 8 attached to the radiation shield 7 are integrated on the top cover of the inner tube 102. When the top cover of the inner tube 102 is removed, the first-stage normal-parahydrogen converter 5 and the radiation shield 7 together with the foam layer 8 attached to the radiation shield 7 can be taken out.

[0032] The gas pipeline in the primary normal-parahydrogen converter 5 is arranged in a coil structure, which can increase the filling amount of the internal catalyst on the one hand, and reduce the height of the primary normal-parahydrogen converter 5 while ensuring a sufficient path length on the other hand. This can reduce the height of the entire cold box 1 on the one hand, and reduce the minimum filling amount of liquid nitrogen in the cold box 1 on the other hand.

[0033] Reference Figure 6-7The hydrogen liquefaction tank 2 includes a vacuum cylinder 201 with an internal vacuum pump, a liquid storage tank 202 arranged inside the vacuum cylinder 201, a refrigerator 204 installed on the top of the vacuum cylinder 201, and a condenser 205 installed on the cold head of the refrigerator 204; a heat exchange tube 206 is coiled on the cold head of the refrigerator 204. Specifically: the refrigerator 204 adopts two-stage refrigeration, and its cold head includes a primary cold head and a secondary cold head. The heat exchange tube 206 includes a primary heat exchange tube 2061 coiled on the primary cold head and a secondary heat exchange tube 2062 coiled on the secondary cold head. The primary heat exchange tube 2061, the secondary heat exchange tube 2062 and the condenser 205 are all located inside the vacuum cylinder 201, and the output end of the primary heat exchange tube 2061 is connected to the secondary heat exchange tube 2062, and the output end of the secondary heat exchange tube 2062 is connected to the input end of the condenser 205.

[0034] The hydrogen outlet of the cold box 1 is connected to the input end of the primary heat exchange pipe 2061 via the delivery pipeline 16. The low-temperature hydrogen outputted from the cold box 1 enters the primary heat exchange pipe 2061 to exchange heat with the primary cold head of the refrigerator 204 to further reduce the temperature, and then enters the secondary heat exchange pipe 2062 from the primary heat exchange pipe 2061 to exchange heat with the secondary cold head of the refrigerator 204, and finally enters the condenser 205 from the secondary heat exchange pipe 2062 to liquefy into liquid hydrogen.

[0035] The secondary normal-para hydrogen converter 203 includes a gas pipeline and a catalyst installed in the gas pipeline, and one end of the gas pipeline of the secondary normal-para hydrogen converter 203 is connected to the output end of the condenser 205, and the other end is connected to the liquid storage tank 202. The liquid hydrogen condensed by the condenser 205 is converted by the secondary normal-para hydrogen converter 203 and then enters the liquid storage tank 202 for storage.

[0036] In addition, a return air pipe 9 is provided between the liquid storage tank 202 and the condenser 205 to balance the pressure of the liquid storage tank 202 and the condenser 205 through the return air pipe 9, so as to ensure that the liquid hydrogen in the condenser 205 flows smoothly into the liquid storage tank 202. In addition, after the liquid hydrogen in the liquid storage tank 202 evaporates to form gaseous hydrogen, the gaseous hydrogen can enter the condenser 205 through the return air pipe 9 and then condense again and flow back into the liquid storage tank 202 to achieve lossless storage. A sensor 2 for detecting the start time of liquid accumulation in the liquid storage tank 202 is provided at the bottom of the liquid storage tank 202 to detect the time when the liquid storage tank 202 starts to accumulate liquid.

[0037] A cold shield 11 is provided inside the vacuum cylinder 201. The cold shield 11 is a cylindrical structure, and a cold shield flange 12 is installed on the top of the cold shield 11. The cold shield flange 12 is fixed to the top cover of the vacuum cylinder 201 through an upper suspension rod 13 and contacts the cold head of the refrigerator 204. The liquid storage tank 202 is located inside the cold shield 11 and is suspended below the cold shield flange 12 through a lower suspension rod 14. During operation, the cold shield 11 forms heat exchange with the cold head of the refrigerator 204 through the cold shield flange 12 to form a low-temperature barrier between the liquid storage tank 202 and the vacuum cavity, thereby reducing the radiation heat leakage of the device.

[0038] Furthermore, the exterior of the cold shield 11 is wrapped with super insulation material to further reduce radiation heat leakage. In addition, since non-metallic materials have low thermal conductivity, the upper suspension rod 13 and the lower suspension rod 14 in this embodiment are both made of non-metallic materials to reduce solid heat leakage of the device.

[0039] Reference Figure 8 The condenser 205 includes an outer casing and a condenser core disposed in the outer casing. The condenser core includes a plurality of fins arranged in a matrix. The fins are formed by processing a plurality of crisscross grooves on the copper material to form a sheet structure at the angle where any longitudinal groove intersects with any transverse groove. This structural design has the following advantages:

[0040] 1. Complex fin structures can be formed through simple groove processing, which reduces production costs. The groove design can guide the medium to flow evenly and reduce flow resistance;

[0041] 2. The lamellar structure formed at the intersection of the grooves enhances the overall mechanical strength;

[0042] 3. The matrix-arranged fin structure can achieve efficient heat exchange in a limited space, which is suitable for applications with limited space;

[0043] 4. The criss-cross grooves form a large number of fins, which significantly increase the contact area with the cooling medium and enhance the heat exchange effect.

[0044] In addition, the hydrogen liquefaction tank 2 in this embodiment also includes a capacitive level gauge and a differential pressure gauge for detecting the liquid level inside the liquid storage tank 202. During operation, the capacitive level gauge continuously displays the liquid level inside the liquid storage tank 202, and the differential pressure gauge detects the highest and lowest pressures of the liquid storage tank 202 and converts them into liquid level values. In this way, the two liquid level values ​​can refer to each other to ensure the accuracy of the liquid level.

[0045] The explosion-proof positive pressure cabinet 3 in this embodiment includes a cabinet, electrical components installed inside the cabinet, wiring holes opened on the cabinet for lines to pass through and connect with corresponding electrical components, and a nitrogen delivery system for maintaining and obtaining positive pressure conditions inside the cabinet; the tops of the cold box 1 and the hydrogen liquefaction box 2 are both provided with wiring ports, explosion-proof boxes that cover the wiring masks inside them, wiring holes opened on the explosion-proof box for lines to pass through, and a nitrogen delivery system for maintaining and obtaining positive pressure conditions inside the explosion-proof box. When working, the lines of the cold box 1 and the hydrogen liquefaction box 2 are all led out from the wiring ports in the explosion-proof box, then pass through the wiring holes on the explosion-proof box, and then are introduced into the corresponding equipment in the cabinet through the wiring holes on the explosion-proof positive pressure cabinet 3. During operation, the nitrogen delivery system in the explosion-proof positive pressure cabinet 3 circulates nitrogen into and out of the cabinet so that the internal space of the cabinet always maintains and obtains positive pressure conditions; and the nitrogen delivery system in the explosion-proof box circulates nitrogen into and out of the box so that the internal space of the explosion-proof box always maintains and obtains positive pressure conditions, thereby ensuring the safety of the entire equipment.

[0046] The hydrogen liquefaction tank 2 also includes an infusion neck tube 15, the input end of the infusion neck tube 15 is located in the liquid storage tank 202, and the output end is located outside the vacuum cylinder 201, and the output end of the infusion neck tube 15 is divided into multiple branches, one of which is used for vacuuming, one is used for taking liquid, one is used for connecting a pressure gauge, and another is used for installing a safety valve.

[0047] In addition, the refrigerator 204 in this embodiment is provided with one or more groups, and the delivery pipeline 16 is divided into one or more branches, each branch is connected to the heat exchange tube 206 in one group of refrigerators 204. When using, the user can control the operation of one or more groups of refrigeration components according to their different requirements for the liquefaction rate.

[0048] As can be seen from the above, the present invention sets a first-stage normal-parahydrogen converter 5 inside the cold box 1, and connects the gas pipeline in the first-stage normal-parahydrogen converter 5 to the hydrogen inlet and the hydrogen outlet respectively. The hydrogen liquefaction box 2 is set to a vacuum cylinder 201 structure with an internal vacuum pump, and its liquid storage tank 202 and the second-stage normal-parahydrogen converter 203 are set inside its vacuum cylinder 201, and the refrigerator 204 in its refrigeration assembly is installed on the top of the vacuum cylinder 201, and the condenser 205 is installed on the cold head of the refrigerator 204. The heat exchange tube 206 is coiled on the cold head of the refrigerator 204, and the condenser 205 and the heat exchange tube 206 are set inside the vacuum cylinder 201, and the output end of the heat exchange tube 206 is connected to the input end of the condenser 205, and the hydrogen outlet of the cold box 1 is connected via the gas pipeline. The delivery pipeline 16 is connected to the input end of the heat exchange tube 206, and the output end of the condenser 205 is connected to the liquid storage tank 202 via the secondary normal para-hydrogen converter 203, so that the high-purity hydrogen enters the cold box 1 after decompression, and the room temperature hydrogen is cooled to a preset temperature inside the cold box 1, and is transported to the hydrogen liquefaction tank 2 after being converted by the primary normal para-hydrogen converter, so as to exchange heat with the cold head through the heat exchange tube 206 coiled on the cold head of the refrigerator 204, and then enter the condenser 205 to condense into liquid hydrogen, and the condensed liquid hydrogen is converted by the secondary normal para-hydrogen converter 203 and then enters the liquid storage tank 202 for storage. The device has high integration and small size; the setting of the two-stage normal para-hydrogen converter can effectively improve the hydrogen liquefaction rate, and the structural setting of the vacuum cylinder 201 can isolate the corresponding liquid storage tank 202 and the condenser 205 in a vacuum environment, so as not to contact the outside world, and avoid the liquid hydrogen from re-evaporating into hydrogen due to external heat during the storage and conversion process, thereby avoiding storage loss.

[0049] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A small hydrogen liquefaction device, characterized in that: include: A cold box (1) and a hydrogen liquefaction box (2); The cold box (1) has a hydrogen inlet, a hydrogen outlet, a liquid nitrogen inlet, and an exhaust port; the cold box (1) is filled with liquid nitrogen and a first-stage normal-parahydrogen converter (5) immersed in the liquid nitrogen; the first-stage normal-parahydrogen converter (5) comprises a gas pipeline and a catalyst installed in the gas pipeline; the input end of the gas pipeline is connected to the hydrogen inlet of the cold box (1), and the output end of the gas pipeline is connected to the hydrogen outlet of the cold box (1); the gas pipeline is arranged in a coil structure, which can reduce the height of the entire cold box (1) on the one hand, and reduce the minimum filling amount of liquid nitrogen in the cold box (1) on the other hand; The hydrogen liquefaction tank (2) comprises a vacuum cylinder (201) with an evacuated interior, a liquid storage tank (202) arranged inside the vacuum cylinder (201), a refrigerator (204) installed on the top of the vacuum cylinder (201), and a condenser (205) installed on the cold head of the refrigerator (204); a heat exchange tube (206) is coiled on the cold head of the refrigerator (204); the condenser (205) and the heat exchange tube (206) are both located inside the vacuum cylinder (201), and the output end of the heat exchange tube (206) is connected to the input end of the condenser (205); The hydrogen outlet of the cold box (1) is connected to the input end of the heat exchange tube (206) via a delivery pipeline (16); the output end of the condenser (205) is connected to the liquid storage tank (202) via a secondary normal-parahydrogen converter (203).

2. The small-scale hydrogen liquefaction device according to claim 1, characterized in that: The cold box (1) is also provided with a sampling port. The output end of the first-stage normal-parahydrogen converter (5) is divided into two paths, one of which is connected to the hydrogen outlet and the other is connected to the sampling port.

3. The small-scale hydrogen liquefaction device according to claim 1, characterized in that: The cold box (1) comprises an outer cylinder (101), an inner cylinder (102) located inside the outer cylinder (101), and a vacuum interlayer (103) located between the outer cylinder (101) and the inner cylinder (102); a first-stage normal-parahydrogen converter (5) is arranged inside the inner cylinder (102); one or more groups of radiation shields (7) and a foam layer (8) attached to the radiation shields (7) are arranged inside the inner cylinder (102) and above the first-stage normal-parahydrogen converter (5); the radiation shields (7) and the foam layer (8) are fixed on the top cover of the inner cylinder (102); the top cover of the inner cylinder (102) and the inner cylinder (102) are detachably assembled; the input end and the output end of the first-stage normal-parahydrogen converter (5) are connected to the hydrogen inlet and the hydrogen outlet arranged on the top cover of the inner cylinder (102) through the radiation shield (7) and the foam layer (8), respectively.

4. The small-scale hydrogen liquefaction device according to claim 1, characterized in that: A return air pipe (9) is provided between the liquid storage tank (202) and the condenser (205) to connect the two. A second sensor for detecting the start time of liquid accumulation inside the liquid storage tank (202) is provided at the bottom of the liquid storage tank (202). The two-stage normal-parahydrogen converter (203) comprises a gas transmission pipeline and a catalyst installed in the gas transmission pipeline. One end of the gas transmission pipeline is connected to the output end of the condenser (205), and the other end is connected to the liquid storage tank (202).

5. The small-scale hydrogen liquefaction device according to claim 1, characterized in that: The refrigerator (204) adopts two-stage refrigeration, wherein the cold head thereof comprises a primary cold head and a secondary cold head, the heat exchange tube (206) comprises a primary heat exchange tube (2061) coiled on the primary cold head and a secondary heat exchange tube (2062) coiled on the secondary cold head, and the primary heat exchange tube (2061) is connected to the secondary heat exchange tube (2062).

6. The small-scale hydrogen liquefaction device according to claim 1, characterized in that: One or more groups of refrigerators (204) are provided, and the delivery pipeline (16) is divided into one or more branches, each branch being connected to a heat exchange pipe (206) in one group of refrigerators (204).

7. The small-scale hydrogen liquefaction device according to claim 1, characterized in that: A cold screen (11) is provided inside the vacuum cylinder (201), the cold screen (11) being a cylindrical structure, and a cold screen flange (12) is installed at the top of the cold screen (11); the cold screen flange (12) is fixed to the top cover of the vacuum cylinder (201) through an upper suspension rod (13), and is in contact with the cold head of the refrigerator (204); the liquid storage tank (202) is located inside the cold screen (11) and is suspended below the cold screen flange (12) through a lower suspension rod (14); the condenser (205) comprises an outer cover shell and a condensing core arranged in the outer cover shell, the condensing core comprises a plurality of fins arranged in a matrix, and the fins are formed by machining a plurality of crisscross grooves on a copper material to form a sheet structure at the angle where any longitudinal groove intersects with any transverse groove.

8. The small-scale hydrogen liquefaction device according to claim 1, characterized in that: The hydrogen liquefaction tank (2) further comprises a liquid infusion neck tube (15), the input end of the liquid infusion neck tube (15) being located inside the liquid storage tank (202), and the output end of the liquid infusion neck tube (15) being located outside the vacuum cylinder (201), and the output end of the liquid infusion neck tube (15) is divided into a plurality of branches, one of which is used for vacuuming, one is used for taking liquid, one is used for connecting a pressure gauge, and another is used for installing a safety valve; the hydrogen liquefaction tank (2) further comprises a capacitance level gauge and a differential pressure gauge for detecting the liquid level inside the liquid storage tank (202).

9. The small-scale hydrogen liquefaction device according to any one of claims 1 to 8, characterized in that: The invention also comprises an explosion-proof positive pressure cabinet (3), which comprises a cabinet body, electrical components installed inside the cabinet body, wiring holes provided on the cabinet body for lines to pass through the cabinet body and connect with corresponding electrical components, and a nitrogen delivery system for maintaining and obtaining positive pressure conditions inside the cabinet body; the tops of the cold box (1) and the hydrogen liquefaction box (2) are both provided with wiring ports, an explosion-proof box for housing the wiring ports inside the cold box, wiring holes provided on the explosion-proof box for lines to pass through, and a nitrogen delivery system for maintaining and obtaining positive pressure conditions inside the explosion-proof box.

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