Stirling cryogenic liquefaction system and method of controlling the same

Abstract

The application discloses a Stirling low-temperature liquefaction system and a control method thereof. The Stirling low-temperature liquefaction system comprises a Stirling refrigerating machine unit, a liquid storage unit, a cooling water unit and a control unit. The Stirling refrigerating machine unit comprises a Stirling refrigerating machine and an internal combustion engine connected through a power transmission mechanism. The Stirling refrigerating machine comprises a condensing head for liquefying gas, and the condensing head is provided with a cold-end heat exchanger. The cold-end heat exchanger adopts a finned heat exchanger or a tubular heat exchanger. The cold-end heat exchanger is directly connected with the liquid storage unit. A water cooler of the Stirling refrigerating machine is connected with the inlet and outlet of the cooling water unit. The control unit is electrically connected with the internal combustion engine, the power transmission mechanism, the liquid storage unit and the cooling water unit respectively. By using the application, the liquefaction efficiency of the liquefaction system is improved, the "zero emission" of the liquefaction process is realized, the internal combustion engine is used to drive the Stirling refrigerating machine to liquefy gas, the energy utilization efficiency is improved, and the dependence of the conventional liquefaction system on electricity is solved.

Description

Technical Field

[0001] This invention relates to the field of gas liquefaction technology, and in particular to a Stirling cryogenic liquefaction system and its control method. Background Technology

[0002] Gas liquefaction refers to the process of changing a substance from a gaseous state to a liquid state. There are two methods to achieve gas liquefaction: lowering the temperature and compressing the volume. Cryogenic gas liquefaction is a technology that physically transforms a gas into a liquid through compression and cooling. The volume of the liquefied gas is greatly reduced, making it easier to store, transport, and utilize. However, it also faces problems such as high energy consumption, high technical requirements, and high equipment costs.

[0003] In the gas liquefaction production process, besides fixed costs such as raw gas purchase, labor wages, and financial expenses, electricity costs account for the vast majority of the total processing costs. Furthermore, the refrigeration system consumes the largest proportion of electricity during the gas cooling process. Therefore, improving the refrigeration and heat transfer efficiency of the refrigeration system and utilizing energy rationally and efficiently are crucial aspects of energy conservation and consumption reduction in gas liquefaction systems.

[0004] Chinese patent document CN108518919A discloses a cascaded natural gas liquefaction system using a pulse tube Stirling refrigerator, and Chinese patent document CN108413705A discloses a cascaded regenerative natural gas liquefaction system using a pulse tube Stirling refrigerator.

[0005] The liquefaction system using a pulse-tube Stirling refrigerator has the advantages of reducing system power consumption and improving system efficiency, but it also suffers from problems such as too many components and a less compact structure. Furthermore, current Stirling refrigerators generally use electricity to drive the motor, significantly reducing energy utilization efficiency. Summary of the Invention

[0006] This invention provides a Stirling cryogenic liquefaction system and its control method, which improves the liquefaction efficiency of the liquefaction system while using an internal combustion engine to drive a Stirling refrigeration unit for gas liquefaction, thereby improving energy utilization efficiency and solving the dependence of conventional liquefaction systems on electricity.

[0007] A Stirling cryogenic liquefaction system includes a Stirling refrigeration unit, a liquid storage unit, a cooling water unit, and a control unit; The Stirling refrigeration unit includes a Stirling refrigeration unit and an internal combustion engine connected by a power transmission mechanism; the Stirling refrigeration unit includes a condenser head for liquefied gas, and the condenser head is provided with a cold end heat exchanger; the cold end heat exchanger is a finned heat exchanger or a tubular heat exchanger, and is vacuum-sealed inside a vacuum chamber. The cold-end heat exchanger is directly connected to the liquid storage unit; the water cooler of the Stirling refrigerator is connected to the inlet and outlet of the cooling water unit.

[0008] The control unit is electrically connected to the internal combustion engine, the power transmission mechanism, the liquid storage unit, and the cooling water unit, respectively.

[0009] Furthermore, the finned heat exchanger is made of copper, and its structure includes an outer shell and external heat exchange fins, external heat exchange channels, and internal heat exchange fins disposed within the outer shell. The external and internal heat exchange fins can be milled from the same material or welded together from multiple sets of fins. The flow area of ​​the external heat exchange channel gradually decreases along the gas flow direction. The upper part of the outer shell is provided with a first air inlet pipe, and the lower part is provided with a first liquid outlet pipe connected to the liquid storage unit. The external heat exchange channel is connected to the first liquid outlet pipe through a first liquid collection channel.

[0010] Furthermore, the tubular heat exchanger includes a base, a shell mounted on the base, a second air inlet pipe mounted on the upper part of the shell, and a second liquid outlet pipe mounted on the base. The second liquid outlet pipe is connected to a liquid storage unit. The shell contains a U-shaped heat exchange tube, supporting fins, and heat exchange fins. The supporting fins and heat exchange fins are interlaced on the U-shaped heat exchange tube at certain intervals to form an upper heat exchange channel, a middle heat exchange channel, and a lower heat exchange channel, which are connected end to end in sequence, and the number of channels decreases step by step. The U-shaped heat exchange tube is welded to the base. The inlet of the upper heat exchange channel is connected to the second air inlet pipe, and the outlet of the lower heat exchange channel is connected to the second liquid outlet pipe through a second liquid collection channel.

[0011] Furthermore, the supporting fins are made of stainless steel, the heat exchange fins are made of copper, and the U-shaped heat exchange tube is a thin-walled round tube made of stainless steel. The supporting fins and heat exchange fins are welded and fixed to the outer wall of the U-shaped heat exchange tube.

[0012] Furthermore, the liquid storage unit includes a cryogenic storage tank and a pressure sensor and a liquid level sensor installed in the cryogenic storage tank; the cryogenic storage tank is equipped with a gas supply pipeline with an electromagnetic shut-off valve and is connected to a cold end heat exchanger through the pipeline. The control unit is electrically connected to the pressure sensor, level sensor, and electromagnetic shut-off valve in the liquid storage unit.

[0013] Furthermore, the pipeline adopts a single-pipeline structure, and the pipeline outlet is located in the upper gas phase space of the cryogenic storage tank; Alternatively, the pipeline may adopt a dual-pipeline structure, including an outlet gas pipeline and an inlet liquid pipeline. The inlet of the outlet gas pipeline is located in the upper gas phase space of the cryogenic storage tank, and the outlet of the inlet liquid pipeline is located in the lower liquid phase space of the cryogenic storage tank.

[0014] Furthermore, the power transmission mechanism includes a torque and speed sensor, a coupling, a clutch, and a cross drive shaft connected in sequence. The torque and speed sensor is connected in sequence to the high-elasticity coupling and flywheel of the Stirling refrigeration machine, and the cross drive shaft is connected to the crankshaft of the internal combustion engine. The control unit is electrically connected to the torque and speed sensor and the clutch in the power transmission mechanism.

[0015] A control method for a Stirling cryogenic liquefaction system includes: The cryogenic storage tank is equipped with a gas supply line with an electromagnetic shut-off valve to control the pressure of the cryogenic storage tank. When the pressure sensor on the cryogenic storage tank detects that the pressure of the cryogenic storage tank is lower than the set pressure, the control unit controls the electromagnetic shut-off valve to open to supply gas. By adjusting the gas pressure of the cryogenic storage tank, the temperature of the cold end heat exchanger of the Stirling refrigerator can be adjusted. A liquid level sensor is installed on the cryogenic storage tank to monitor the liquid level in the tank. When the liquid level in the cryogenic storage tank is detected to be higher than the set liquid level, the control unit controls the internal combustion engine to shut down, thereby stopping the Stirling refrigeration unit. The torque and speed sensor in the power transmission mechanism is used to monitor the speed and input power of the Stirling refrigerator. If the speed and input power are abnormal, the control unit controls to reduce or increase the fuel supply to the internal combustion engine. The clutch in the power transmission mechanism is used to control the connection and disconnection of the Stirling refrigeration unit and the internal combustion engine, which is achieved by controlling the on and off of the clutch in the transmission mechanism through the control unit.

[0016] The cooling water unit must be turned on before the Stirling refrigerator. When the cooling water temperature is lower than the set temperature, the control unit can control the clutch to de-energize and close, and start the Stirling refrigerator. When the temperature and pressure of the cooling water in the cooling water unit deviate from the set target value, the control unit controls the internal combustion engine to shut down.

[0017] This invention employs an internal combustion engine to drive a Stirling refrigerator. The internal combustion engine can utilize coalbed methane, shale gas, biogas, diesel oil, gasoline, and other fuels. More preferably, the internal combustion engine can directly use natural gas as fuel, utilizing locally available resources. A portion of the natural gas is used for combustion to drive the engine, while the remainder can be liquefied and recovered in the cold-end heat exchanger of the Stirling refrigerator as a product output. Furthermore, it is also highly compatible with the liquefaction of gases such as hydrogen and oxygen, demonstrating broad application prospects.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The liquid storage system of this invention is directly connected to the condenser head of a Stirling refrigerator via pipelines. Under the low-temperature negative pressure of the condenser head, the gas enters the cold-end heat exchanger along the pipeline, where it is cooled and liquefied, and then flows back to the cryogenic storage tank under gravity. In particular, with a dual-pipeline structure, the gas enters the cold-end heat exchanger from the top of the condenser head along the outlet pipeline, continuously cooling along the gas flow and gravity direction until liquefied, and then flows back to the cryogenic storage tank along the inlet pipeline. During the gas liquefaction process, the flow resistance is low and the flow velocity is high, greatly improving the liquefaction efficiency and achieving gas liquefaction through non-powered circulation. The gas liquefaction process is closed-loop, with no gas emissions, no waste of cold energy or environmental pollution, and the system has low cost and simple structure.

[0019] 2. The Stirling cryogenic liquefaction system of this invention uses an internal combustion engine as a power source to directly drive the piston of the Stirling refrigerator to push the working gas to do work, generating thermal potential energy, i.e., temperature difference, without relying on an electric motor. This not only solves the problem of power shortage but also has significant advantages in the liquefaction and recovery of unconventional natural gas such as coalbed methane and rock formation gas.

[0020] 3. Finned heat exchangers are processed from the same material, resulting in excellent heat exchange performance. Along the gas flow direction, the flow area of ​​the outer heat exchange channel in a finned heat exchanger gradually decreases. As the gas flows and absorbs heat within the heat exchange channel, its volume gradually decreases, and its flow velocity slows down. Reducing the flow area ensures that the gas maintains a high flow velocity during the liquefaction process, improving heat transfer efficiency. Tubular heat exchangers have the advantage of a large heat exchange area, which is more conducive to pre-cooling the gas inside the shell and creating a larger negative pressure, while also exhibiting low gas flow resistance. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a Stirling cryogenic liquefaction system according to the present invention; Figure 2 This is a structural diagram of the finned cold-end heat exchanger used in this invention; Figure 3 This is a structural diagram of the tubular cold-end heat exchanger used in this invention; Figure 4 This invention provides a single-pipeline liquefaction process for a Stirling cryogenic liquefaction system. Figure 5 This invention relates to a dual-pipeline liquefaction process for a Stirling cryogenic liquefaction system.

[0022] In the diagram: 1-Stirling refrigerator unit; 101-Stirling refrigerator; 102-Condenser head; 103-Cold end heat exchanger; 104-Vacuum enclosure; 105-Internal combustion engine; 106-Finned heat exchanger; 107-Tube heat exchanger; 108-Shell; 109-External heat exchange fins; 110-External heat exchange channel; 111-Internal heat exchange fins; 112-First inlet pipe; 113-First liquid collection channel; 114-First liquid outlet pipe; 115-Shell; 116-Base; 117-U-shaped heat exchange tube; 118-Support fins; 119-Heat exchange fins; 120-Upper heat exchange channel; 121- 122-Lower heat exchanger channel; 123-Second air inlet pipe; 124-Second liquid collection channel; 125-Second liquid outlet pipe; 126-Flywheel; 127-High-elasticity coupling; 128-Crankshaft; 129-Water cooler; 2-Liquid storage unit; 201-Cryogenic storage tank; 202-Pressure sensor; 203-Level sensor; 204-Pipeline; 205-Air outlet pipeline; 206-Liquid inlet pipeline; 207-Maintenance air pipeline; 208-Solenoid shut-off valve; 3-Cooling water unit; 4-Control unit; 5-Torque and speed sensor; 6-Coupling; 7-Clutch; 8-Cross drive shaft. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not constitute any limitation thereof.

[0024] like Figure 1 As shown, a Stirling cryogenic liquefaction system mainly includes a Stirling refrigeration unit 1, a liquid storage unit 2, a cooling water unit 3, and a control unit 4.

[0025] The Stirling refrigeration unit 1 includes a Stirling refrigeration unit 101 and an internal combustion engine 105; the Stirling refrigeration unit 101 and the internal combustion engine 105 are connected by a power transmission mechanism. The power transmission mechanism includes a torque-speed sensor 5, a coupling 6, a clutch 7, and a cross drive shaft 8 connected in sequence. The torque-speed sensor 5 is sequentially connected to the high-elasticity coupling 127 and the flywheel 126 of the Stirling refrigeration unit 101, and the cross drive shaft 8 is connected to the crankshaft 128 of the internal combustion engine 105. In this invention, the internal combustion engine 105 can use natural gas, diesel, gasoline, etc., as fuel.

[0026] The Stirling refrigerator 101 includes a condenser head 102 for liquefied gas; a cold-end heat exchanger 103 is provided in the condenser head 102, and the cold-end heat exchanger 103 is vacuum-sealed inside a vacuum chamber 104. The water cooler 129 of the Stirling refrigerator 101 is connected to the inlet and outlet of the cooling water unit 3.

[0027] The liquid storage unit 2 is directly connected to the condenser head 102 of the Stirling refrigerator 101 via pipe 204. Under the low-temperature negative pressure of the condenser head 102, the gas enters the cold-end heat exchanger 103 along pipe 204, where it is cooled and liquefied, and then flows back to the low-temperature storage tank 201 under gravity. In this invention, the cold-end heat exchanger 103 can adopt either a finned heat exchanger 106 or a tubular heat exchanger 107.

[0028] like Figure 2 As shown, the finned heat exchanger 106 includes a shell 108, external heat exchange fins 109, external heat exchange channels 110, internal heat exchange fins 111, a first air inlet pipe 112, a first liquid collection channel 113, and a first liquid outlet pipe 114. The finned heat exchanger 106 is made of copper, and the flow area of ​​the external heat exchange channel 110 gradually decreases along the gas flow direction.

[0029] like Figure 3 As shown, the tubular heat exchanger 107 includes a shell 115, a base 116, a U-shaped heat exchange tube 117, supporting fins 118, heat exchange fins 119, a second air inlet pipe 123, a second liquid collection channel 124, and a second liquid outlet pipe 125. The supporting fins 118 and heat exchange fins 119 are interlaced at certain intervals on the U-shaped heat exchange tube 117, forming an upper heat exchange channel 120, a middle heat exchange channel 121, and a lower heat exchange channel 122, which are connected end-to-end, with the number of channels decreasing progressively. The supporting fins 118 are made of stainless steel; the heat exchange fins 119 are made of copper; the U-shaped heat exchange tube 117 is a thin-walled round tube made of stainless steel; the supporting fins 118 and heat exchange fins 119 are welded to the outer wall of the U-shaped heat exchange tube 117 by vacuum brazing.

[0030] like Figure 4 As shown, the liquid storage unit 2 includes a cryogenic storage tank 201, a pressure sensor 202, a liquid level sensor 203, a pipeline 204, a gas supply pipeline 207, and a solenoid shut-off valve 208. The pipeline 204 can be a single-pipeline structure, with gas and liquid flowing within the same pipeline. In the single-pipeline structure, the outlet of the pipeline 204 must be located in the upper gas phase space of the cryogenic storage tank 201.

[0031] like Figure 5 As shown, the pipeline can also be a dual-pipeline structure, including an outlet pipe 205 and an inlet pipe 206. In the dual-pipeline structure, the inlet of the outlet pipe 205 is located in the upper gas phase space of the cryogenic storage tank 201, and the outlet of the inlet pipe 206 is located in the lower liquid phase space of the cryogenic storage tank 201.

[0032] In particular, with the dual-pipeline structure, the gas enters the cold-end heat exchanger 103 from the top of the condenser head 102 along the outlet pipe 205, continuously cooling along the gas flow and gravity direction until liquefied, and then flowing back to the cryogenic storage tank 201 along the liquid inlet pipe 206. The low flow resistance and high flow velocity during gas liquefaction greatly improve liquefaction efficiency and achieve non-powered circulating liquefaction of the gas. The gas liquefaction process is closed-loop, with no gas emissions, no waste of cold energy or environmental pollution, and the system has low cost and simple structure.

[0033] In this invention, the control unit 4 is electrically connected to the torque and speed sensor 5, clutch 7 and internal combustion engine 105 in the Stirling refrigeration unit 1, to the pressure sensor 202, liquid level sensor 203 and electromagnetic shut-off valve 208 in the liquid storage unit 2, and to the cooling water unit 3.

[0034] The control process of control unit 4 specifically includes: The electromagnetic shut-off valve 208 is used to control the pressure of the cryogenic storage tank 201. When the pressure sensor 202 detects that the pressure of the cryogenic storage tank 201 is lower than the set pressure, the control unit 4 controls the electromagnetic shut-off valve 208 to open to replenish gas, and adjusts the temperature of the Stirling refrigerator cold end heat exchanger 103 by regulating the gas pressure of the cryogenic storage tank 201.

[0035] The liquid level sensor 203 is used to monitor the liquid level of the cryogenic storage tank 201. When the liquid level of the cryogenic storage tank 201 is detected to be higher than the set liquid level, the control unit 4 controls the internal combustion engine 105 to shut down, thereby stopping the Stirling refrigeration unit 101.

[0036] Torque-speed sensor 5 is used to monitor the speed and input power of the Stirling refrigerator. If the speed and input power are abnormal, the control unit controls to reduce or increase the fuel supply to the internal combustion engine. The clutch 7 is used to control the connection and disconnection of the Stirling refrigeration unit 101 and the internal combustion engine 105, which is achieved by controlling the on and off of the clutch 7 in the transmission mechanism through the control unit 4.

[0037] The cooling water unit 3 must be turned on before the Stirling refrigerator 101. When the cooling water temperature is lower than the set temperature, the control unit 4 can control the clutch 7 to de-energize and close, and start the Stirling refrigerator 101. When the temperature and pressure of the cooling water in the cooling water unit 3 deviate from the set target value, the control unit 4 controls the internal combustion engine 105 to be turned off.

[0038] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A Stirling cryogenic liquefaction system, characterized in that, It includes a Stirling refrigeration unit (1), a liquid storage unit (2), a cooling water unit (3), and a control unit (4); The Stirling refrigerator unit (1) includes a Stirling refrigerator (101) and an internal combustion engine (105) connected by a power transmission mechanism; the Stirling refrigerator (101) includes a condenser head (102) for liquefied gas, and the condenser head (102) is provided with a cold end heat exchanger (103); the cold end heat exchanger (103) is a finned heat exchanger (106) or a tubular heat exchanger (107), and is vacuum-sealed inside a vacuum chamber (104); The cold end heat exchanger (103) is directly connected to the liquid storage unit (2); the water cooler (129) of the Stirling refrigerator (101) is connected to the inlet and outlet of the cooling water unit (3); The control unit (4) is electrically connected to the internal combustion engine (105), the power transmission mechanism, the liquid storage unit (2), and the cooling water unit (3), respectively; The power transmission mechanism includes a torque and speed sensor (5), a coupling (6), a clutch (7), and a cross drive shaft (8) connected in sequence. The torque and speed sensor (5) is connected in sequence to the high-elasticity coupling (127) and flywheel (126) of the Stirling refrigerator (101). The cross drive shaft (8) is connected to the crankshaft (128) of the internal combustion engine (105). The control unit (4) is electrically connected to the torque and speed sensor (5) and the clutch (7) in the power transmission mechanism. The control method for the Stirling cryogenic liquefaction system is as follows: The cryogenic storage tank (201) of the liquid storage unit (2) is equipped with a gas supply line (207) with an electromagnetic shut-off valve (208) to control the pressure of the cryogenic storage tank (201). When the pressure sensor (202) installed on the cryogenic storage tank (201) detects that the pressure of the cryogenic storage tank (201) is lower than the set pressure, the control unit (4) controls the electromagnetic shut-off valve (208) to open to supply gas. By adjusting the gas pressure of the cryogenic storage tank (201), the temperature of the cold end heat exchanger of the Stirling refrigerator is adjusted. A liquid level sensor (203) is installed on the cryogenic storage tank (201) to monitor the liquid level of the cryogenic storage tank (201). When the liquid level of the cryogenic storage tank (201) is detected to be higher than the set liquid level, the control unit (4) controls the internal combustion engine (105) to shut down, thereby stopping the Stirling refrigeration unit (101). The torque and speed sensor (5) in the power transmission mechanism is used to monitor the speed and input power of the Stirling refrigerator (101). If the speed and input power are abnormal, the control unit (4) controls to reduce or increase the fuel supply to the internal combustion engine (105). The clutch (7) in the power transmission mechanism is used to control the connection and disconnection of the Stirling refrigerator (101) and the internal combustion engine (105), which is achieved by controlling the power on and off of the clutch (7) in the power transmission mechanism through the control unit (4); The cooling water unit (3) must be turned on before the Stirling refrigerator (101). When the cooling water temperature is lower than the set temperature, the control unit (4) controls the clutch (7) to be de-energized and closed, and starts the Stirling refrigerator (101). When the temperature and pressure of the cooling water in the cooling water unit (3) deviate from the set target value, the control unit (4) controls the internal combustion engine (105) to be turned off.

2. The Stirling cryogenic liquefaction system according to claim 1, characterized in that, The finned heat exchanger (106) is made of copper and has a structure including a shell (108) and external heat exchange fins (109), external heat exchange channels (110) and internal heat exchange fins (111) disposed inside the shell (108). The external heat exchange fins (109) and internal heat exchange fins (111) are milled on the same material or welded together by multiple sets of fins. The flow area of ​​the external heat exchange channel (110) gradually decreases along the gas flow direction. The upper part of the shell (108) is provided with a first air inlet pipe (112) and the lower part is provided with a first liquid outlet pipe (114) connected to the liquid storage unit (2). The external heat exchange channel (110) is connected to the first liquid outlet pipe (114) through the first liquid collection channel (113).

3. The Stirling cryogenic liquefaction system according to claim 1, characterized in that, The tubular heat exchanger (107) includes a base (116), a shell (115) mounted on the base (116), a second air inlet pipe (123) mounted on the upper part of the shell (115), and a second liquid outlet pipe (125) mounted on the base (116). The second liquid outlet pipe (125) is connected to a liquid storage unit (2). The shell (115) contains a U-shaped heat exchange tube (117), supporting fins (118), and heat exchange fins (119). 119) The U-shaped heat exchange tubes (117) are interspersed at certain intervals to form an upper heat exchange channel (120), a middle heat exchange channel (121), and a lower heat exchange channel (122), which are connected end to end in sequence, and the number of channels decreases step by step; the U-shaped heat exchange tubes (117) are welded to the base (116); the inlet of the upper heat exchange channel (120) is connected to the second air inlet pipe (123), and the outlet of the lower heat exchange channel (122) is connected to the second liquid outlet pipe (125) through the second liquid collection channel (124).

4. The Stirling cryogenic liquefaction system according to claim 3, characterized in that, The supporting fins (118) are made of stainless steel; the heat exchange fins (119) are made of copper; the U-shaped heat exchange tube (117) is a thin-walled round tube made of stainless steel; the supporting fins (118) and the heat exchange fins (119) are welded and fixed to the outer wall of the U-shaped heat exchange tube (117).

5. The Stirling cryogenic liquefaction system according to claim 1, characterized in that, The liquid storage unit (2) includes a cryogenic storage tank (201) and a pressure sensor (202) and a liquid level sensor (203) installed in the cryogenic storage tank (201); the cryogenic storage tank (201) is equipped with a gas supply pipeline (207) with an electromagnetic shut-off valve (208) and is connected to a cold end heat exchanger (103) through a pipeline (204); The control unit (4) is electrically connected to the pressure sensor (202), liquid level sensor (203) and electromagnetic shut-off valve (208) in the liquid storage unit (2).

6. The Stirling cryogenic liquefaction system according to claim 5, characterized in that, The pipeline (204) adopts a single pipeline structure, and the outlet of the pipeline (204) is located in the upper gas phase space of the cryogenic storage tank (201); Alternatively, the pipeline (204) adopts a dual-pipeline structure, including an outlet pipeline (205) and an inlet pipeline (206). The inlet of the outlet pipeline (205) is located in the upper gas phase space of the cryogenic storage tank (201), and the outlet of the inlet pipeline (206) is located in the lower liquid phase space of the cryogenic storage tank (201).

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