A hydrogen liquefaction precooling system suitable for variable load conditions

Abstract

The present application relates to the technical field of cryogenic engineering equipment. In order to solve the technical problem that the traditional turbine expansion refrigeration as a pre-cooling system for hydrogen liquefaction equipment cannot meet the working conditions of large load changes, a hydrogen liquefaction pre-cooling system suitable for variable load conditions is proposed. A normal temperature gas storage system is set at the room temperature end of the refrigeration cycle, and a low-temperature liquefied gas storage tank is set at the low-temperature end. Under low-load conditions, the normal temperature gas storage system adds the stored gaseous pre-cooling medium to the refrigeration cycle, and uses the extra refrigeration capacity due to the load reduction to cool and liquefy the pre-cooling medium and store it in a low-temperature liquefied gas storage tank; under high-load conditions, the low-temperature liquefied gas storage tank consumes the pre-stored low-temperature liquid pre-cooling medium to supplement the insufficient refrigeration capacity of the refrigeration cycle, and the excess pre-cooling medium is recycled to the normal temperature gas storage system. The present invention overcomes the disadvantage that turbine expansion refrigeration cannot achieve large load changes, and greatly improves work efficiency, reliability and stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of cryogenic engineering equipment, and in particular relates to a hydrogen liquefaction precooling system suitable for variable load working conditions. Background Art

[0002] Hydrogen energy is a clean and efficient future energy source. Due to its diverse sources, storability, renewable energy, electrical and combustible properties, zero pollution, and zero emissions, hydrogen has become a key option for international energy transformation and is considered the clean energy source with the greatest development potential in the 21st century. As the global climate and environmental protection situation becomes increasingly severe and the pressure to address climate change continues to grow, hydrogen energy has attracted worldwide attention, and energy supply reform has become a hot topic in current sociopolitical, economic, and technological circles. Hydrogen produced from renewable energy sources such as wind, solar, hydropower, and tidal power, also known as "green hydrogen," is the primary source of hydrogen energy in the future. It can be used in transportation, civil applications, and power generation and storage, and is also expected to be used on a large scale in the chemical industry, such as replacing coke as a reducing agent. However, the volatility of renewable energy generation places special demands on the downstream green hydrogen production systems (water electrolysis and hydrogen liquefaction units).

[0003] As described in invention patent CN114963688A, traditional hydrogen liquefaction equipment generally includes a precooling system, a main refrigeration system, and a liquefaction system. The precooling system provides precooling of approximately 70 to 120K for the main refrigeration system and liquefaction system. It includes a precooling heat exchanger and a cooling system that provides a cold source for the precooling system. The cooling system is coupled to the main refrigeration system and the liquefaction system via the precooling heat exchanger. Common precooling systems use two cooling schemes: open cryogenic liquid precooling and closed cryogenic refrigeration. Open cryogenic liquid precooling systems use liquid nitrogen or liquefied natural gas as the cold source. The former is particularly suitable for situations where stable and inexpensive liquid nitrogen is available on site, such as a nearby air separation unit that can provide a stable and inexpensive liquid nitrogen resource. The latter is particularly suitable for situations such as liquefied natural gas ports where the cold energy from liquefied natural gas vaporization needs to be recovered. Closed low-temperature refrigeration pre-cooling systems are generally turbine expansion refrigeration systems, auto-cascade mixed working fluid throttling refrigeration systems or heat recovery refrigeration systems. They are suitable for scenarios where electricity prices are cheap or cryogenic liquids such as liquid nitrogen and liquefied natural gas are not easily available on site.

[0004] Because high-quality renewable energy sources are often located in remote, inaccessible areas with limited transportation, it is difficult to continuously obtain low-cost cryogenic liquid resources such as liquid nitrogen through transportation. Therefore, the hydrogen liquefaction unit that matches renewable energy to achieve fully off-grid green hydrogen production should adopt closed low-temperature refrigeration as the cooling solution for the pre-cooling system, using off-grid electricity to generate the required cooling capacity on-site. In addition, when the hydrogen liquefaction unit matches the renewable energy power output with large fluctuations, the load of the pre-cooling system will also fluctuate significantly, thus placing requirements on the pre-cooling system to operate stably under variable load conditions.

[0005] Turbine expansion refrigeration is a common and mature technology for achieving refrigeration in the 70-120K temperature range. It is commonly used in liquefied natural gas (LNG) liquefaction, skid-mounted nitrogen generation, liquefied air energy storage, and air separation systems of various sizes. Its advantages include mature technology, simple process flow and control, a wide range of key equipment suppliers, and low equipment costs. The basic principle of turbine expansion refrigeration is to use compressed high-pressure working gas, which is pre-cooled by returning low-pressure cold working gas through a countercurrent heat exchanger. It is then expanded to a low temperature by a turbine expander to achieve refrigeration. Throttling with a throttle valve further liquefies the working gas. However, operating a turbine expander significantly outside its design range can significantly reduce efficiency and become susceptible to surge. Furthermore, if the inlet temperature of the turbine expander is too low, the expanded working gas can partially liquefy, causing droplets to impact and damage the high-speed impeller. Therefore, the process requires precise control of the working fluid flow, pressure, and temperature at the turboexpander inlet within a narrow design range. Otherwise, the efficiency, stability, and reliability of the turboexpander will be significantly reduced, and in severe cases, the turbine may be damaged. Therefore, the traditional turboexpansion refrigeration cycle used as a precooling system cannot cope with large load fluctuations. Summary of the Invention

[0006] Based on the needs of off-grid renewable energy green liquid hydrogen production mode, this invention proposes a pre-cooling system suitable for variable load conditions. While retaining many advantages of turbine expansion refrigeration, it can match the variable load conditions. To this end, this invention adopts the following technical solutions:

[0007] A hydrogen liquefaction precooling system suitable for variable load working conditions comprises a normal temperature gas storage system, a refrigeration cycle, a precooling heat exchanger I, a precooling heat exchanger II and a cryogenic liquefied gas storage tank.

[0008] The hydrogen liquefaction precooling system is filled with a precooling medium, which is methane, nitrogen, hydrogen, argon, neon, helium, or any mixture of the above gases. The precooling medium is compressed, precooled, and expanded in the refrigeration cycle to generate refrigeration, and the refluxed low-temperature precooling medium provides cooling for precooling heat exchanger I and precooling heat exchanger II. A suitable precooling medium is selected according to the precooling temperature required by the hydrogen liquefaction device.

[0009] The normal temperature gas storage system is provided with a return air interface and a gas supply interface; the top of the low-temperature liquefied gas storage tank is provided with a liquid inlet interface and a gas outlet interface, and the bottom is provided with a liquid supply interface; the pre-cooling heat exchanger I is provided with a low-pressure pre-cooling working medium channel; the pre-cooling heat exchanger II is provided with a low-temperature liquid pre-cooling working medium channel.

[0010] The return air interface of the normal temperature gas storage system is connected to the working fluid recovery interface of the refrigeration cycle, and the air supply interface of the normal temperature gas storage system is connected to the working fluid replenishment interface of the refrigeration cycle; the function of the normal temperature gas storage system is to store pre-cooling working fluid, and when the pre-cooling system is under high load conditions, it recovers excess normal temperature gaseous pre-cooling working fluid in the system, and when the pre-cooling system is under low load conditions, it replenishes the system with insufficient pre-cooling working fluid.

[0011] The refrigeration cycle is coupled with the main refrigeration system and liquefaction system in the hydrogen liquefaction device through the pre-cooling heat exchanger I to provide a temperature from room temperature to the boiling point of the pre-cooling medium T b Pre-cooling; the refrigeration cycle is coupled with the main refrigeration system and liquefaction system in the hydrogen liquefaction device through the pre-cooling heat exchanger II to provide the pre-cooling working medium boiling point temperature T b Pre-cooling; the function of the refrigeration cycle is to use the refrigeration cycle to cool and liquefy the pre-cooling working medium. The liquefied pre-cooling working medium will pass through the low-temperature liquefied gas storage tank, and then pass through the pre-cooling heat exchanger I and the pre-cooling heat exchanger II in sequence to be vaporized and reheated, thereby outputting cold capacity to the main refrigeration system and liquefaction system of the hydrogen liquefaction device as pre-cooling.

[0012] The liquid inlet interface of the cryogenic liquefied gas storage tank is connected to the liquid outlet interface of the refrigeration cycle, the liquid supply interface of the cryogenic liquefied gas storage tank is connected to the cold end inlet of the cryogenic liquid pre-cooling working medium channel of the pre-cooling heat exchanger II, and the gas outlet interface of the cryogenic liquefied gas storage tank is connected to the cold end inlet of the low-pressure pre-cooling working medium channel of the pre-cooling heat exchanger I; the function of the cryogenic liquefied gas storage tank is to store the additional cryogenic liquid pre-cooling working medium produced by the refrigeration cycle when the pre-cooling system is in low-load working condition, and to provide pre-stored cryogenic liquid pre-cooling working medium as cooling output when the pre-cooling system is in high-load working condition.

[0013] Preferably, the normal temperature gas storage system further comprises a return air valve FV0, a ​​booster compressor, a gas storage container, a pressure gauge PT0 and a low-pressure gas supply valve FV1; the return air interface, the return air valve FV0, the booster compressor, the gas storage container, the low-pressure gas supply valve FV1 and the gas supply interface are sequentially connected through pipelines; the pressure gauge PT0 is arranged on the gas storage container; wherein, the gas storage container is one or more parallel pressure vessels, specifically seamless steel cylinders, welded steel cylinders, hoop-wound composite gas cylinders, fully wound composite gas cylinders or steel belt-wound steel cylinders, and can withstand a maximum storage pressure p 0_max Higher than the high pressure side pressure p of the refrigeration cycle h; The pressure gauge PT0 provided on the gas storage container is used to monitor the storage pressure p0 in the gas storage container; when the pre-cooling system is in high-load working condition, the return air valve FV0 is opened, the booster compressor is started, and the low-pressure air supply valve FV1 is closed. The excess room-temperature gaseous pre-cooling working medium in the refrigeration cycle enters the booster compressor through the working medium recovery interface, the return air interface, and the return air valve FV0, is compressed to the storage pressure p0, and is stored in the gas storage container; when the pre-cooling system is in low-load working condition, the return air valve FV0 and the booster compressor are closed, and the air supply valve FV1 is opened. After the pre-cooling working medium pre-stored in the gas storage container is decompressed, it is replenished into the refrigeration cycle through the air supply interface and the working medium replenishment interface.

[0014] In this application, the concepts of high pressure and low pressure are relative. High pressure is used to describe the pressure of the pipelines, equipment and working fluids from the outlet of the circulating compressor to the inlet side of the turbine expander in the refrigeration cycle, and low pressure is used to describe the pressure of the pipelines, equipment and working fluids from the outlet of the turbine expander to the inlet side of the circulating compressor unit in the refrigeration cycle.

[0015] Preferably, the normal temperature gas storage system further comprises a high pressure gas supply valve FV2, which is connected to the upstream pipeline of the low pressure gas supply valve FV1 and the return air interface through a pipeline; when the pre-cooling system is under low load, if the gas storage pressure p0 in the gas storage container is higher than the high pressure side pressure p h When the low-pressure air supply valve FV1 is closed and the high-pressure air supply valve FV2 is opened, the pre-cooling working medium is replenished into the refrigeration cycle from the return air interface and the working medium recovery interface. When the gas pressure p0 in the gas storage container gradually decreases and is lower than the high-pressure side pressure p h When the high-pressure air supply valve FV2 is closed and the low-pressure air supply valve FV1 is opened, the pre-cooling working fluid is replenished into the refrigeration cycle from the air supply interface and the working fluid replenishment interface; such a design can make full use of the high-pressure potential energy of the pre-cooling working fluid stored in the gas storage container, reduce the flow of the circulating compressor in the refrigeration cycle, and reduce the energy consumption of the system.

[0016] If the gas storage container in the ambient temperature gas storage system is a pressure vessel, it requires a booster compressor with a high outlet pressure and a high pressure ratio, which is relatively high in both initial fixed asset investment and subsequent operation and maintenance costs. Preferably, the gas storage container in the ambient temperature gas storage system is one or more parallel atmospheric pressure gas bags. These atmospheric pressure gas bags have the advantages of low cost and low energy consumption. Although atmospheric pressure gas bags occupy more space than pressure vessels, storage space can be easily and cheaply obtained in remote renewable energy production sites.

[0017] Preferably, a normal temperature gas storage system using a normal pressure gas bag as a gas storage container includes a return air interface, a return air valve FV0, a ​​gas storage container, an air supply pump, a purifier, a low-pressure air supply valve FV1 and an air supply interface, which are connected in sequence through pipelines; the return air interface is connected to the working medium recovery interface of the refrigeration cycle, and the air supply interface is connected to the working medium replenishment interface of the refrigeration cycle; the function of the air supply pump is to pump out the pre-cooled working medium in the normal pressure gas bag and replenish it into the refrigeration cycle through the working medium replenishment interface located at the low-pressure inlet end of the circulating compressor of the refrigeration cycle. Since the storage pressure p0 of the normal pressure gas bag is close to normal pressure, it is close to the low-pressure side pressure p l The difference is not much, so the lift of the air supply pump does not need to be too high, and the energy consumption and cost are much lower than the booster compressor required when using a pressure vessel; the function of the purifier is to remove impurities in the pre-cooling working fluid, because the atmospheric pressure air bag is more likely to contaminate the stored gas than the pressure vessel.

[0018] Preferably, the refrigeration cycle also includes a circulating compressor, a turbine expander, a throttle valve JTV1 and a liquid outlet interface; the pre-cooling heat exchanger I is also provided with a high-pressure pre-cooling working medium channel and a low-pressure pre-cooling working medium channel; the top of the low-temperature liquefied gas storage tank is also provided with a steam return interface. The circulating compressor high-pressure outlet, the high-temperature end inlet of the high-pressure pre-cooling working medium channel, the low-temperature end outlet of the high-pressure pre-cooling working medium channel, the turbine expander, the throttle valve JTV1, the liquid outlet interface and the liquid inlet interface are connected in sequence through pipelines; the liquid supply interface, the low-temperature end inlet of the low-temperature liquid pre-cooling working medium channel, the high-temperature end outlet of the low-temperature liquid pre-cooling working medium channel and the steam return interface are connected in sequence through pipelines; the gas outlet interface, the low-temperature end inlet of the low-pressure pre-cooling working medium channel, the high-temperature end outlet of the low-pressure pre-cooling working medium channel and the low-pressure inlet of the circulating compressor are connected in sequence through pipelines; the working medium recovery interface is provided on the high-pressure outlet end pipeline of the circulating compressor, and the working medium replenishment interface is provided on the low-pressure inlet end pipeline of the circulating compressor; the pre-cooling working medium passes through the circulating compressor from the low-pressure p l Compression to high pressure p h First, it passes through the high-pressure pre-cooling medium channel in the pre-cooling heat exchanger I and is pre-cooled by the low-pressure pre-cooling medium with a lower temperature flowing back; then, the pre-cooling medium enters the turbine expander and expands to the intermediate pressure p m Then it enters the throttle valve JTV1 and expands to the low pressure p l The pre-cooling medium that has undergone secondary expansion through the throttle valve JTV1 is partially liquefied, and the vapor-liquid two-phase pre-cooling medium enters the cryogenic liquefied gas storage tank through the liquid outlet interface and the liquid inlet interface; the cryogenic liquid pre-cooling medium in the cryogenic liquefied gas storage tank enters the cryogenic liquid pre-cooling medium channel of the pre-cooling heat exchanger II through the liquid supply interface at the bottom under the action of gravity and thermal siphon, and the vaporized phase changes to gaseous state, providing the pre-cooling medium boiling point temperature T to the main refrigeration system and liquefaction system of the hydrogen liquefaction device. bThe gaseous pre-cooling medium returns to the cryogenic liquefied gas storage tank through the steam return interface; the gaseous pre-cooling medium at the top of the cryogenic liquefied gas storage tank enters the low-pressure pre-cooling medium flow channel in the pre-cooling heat exchanger I through the gas outlet interface, providing room temperature T for the inflowing high-pressure and high-temperature pre-cooling medium and the main refrigeration system and liquefaction system of the hydrogen liquefaction device. amb To the boiling point of the pre-cooling medium T b Pre-cooling of the temperature zone; the reheated low-pressure pre-cooling medium finally returns to the low-pressure inlet of the circulating compressor.

[0019] Preferably, the refrigeration cycle further includes a bypass valve FV3, which connects the pipelines of the low-pressure inlet and the high-pressure outlet of the circulation compressor; by controlling the opening of the bypass valve FV3, the flow regulation of the circulation compressor under variable load conditions can be achieved.

[0020] Preferably, the refrigeration cycle further includes a throttle valve JTV0, which connects a pipeline between the turbine expander inlet and the throttle valve JTV1 outlet; by controlling the opening of the throttle valve JTV0, flow regulation and stabilization of the turbine expander under variable load conditions can be achieved.

[0021] Preferably, the refrigeration cycle further includes a pressure gauge PT1, a pressure gauge PT2 and a pressure gauge PT3; the pressure gauge PT1 is arranged on the high-pressure outlet pipeline of the circulation compressor, the pressure gauge PT2 is arranged on the turbine expander outlet pipeline, and the pressure gauge PT3 is arranged on the low-pressure inlet pipeline of the circulation compressor.

[0022] In order to further simplify the control and reduce the impact of the air supply process on the flow through the circulating compressor and the turbine expander, it is preferred that the air storage container is one or more parallel pressure vessels; the refrigeration cycle also includes a throttle valve JTV2; the pre-cooling heat exchanger I is also provided with an air supply channel; the working medium supply interface, the air supply channel, the throttle valve JTV2 and the turbine expander outlet are connected in sequence through pipelines; when the pre-cooling system is under low load, the return air valve FV0 and the booster compressor are closed, the air supply valve FV1 is opened, and the air pre-stored in the air storage is returned to the compressor. The pre-cooling working fluid in the container enters the air supply channel in the pre-cooling heat exchanger I through the air supply interface and the working fluid supply interface, is pre-cooled by the returning low-pressure cold pre-cooling working fluid, and then merges with the main circulating fluid from the turbine expander after throttling expansion through the throttle valve JTV2. The main circulating fluid then enters the throttle valve JTV1 for further throttling expansion. This design allows the air supply flow to be independently controlled by the air supply valve FV1 and the throttle valve JTV2, without passing through the circulating compressor and the turbine expander, greatly simplifying the control of the turbine expander inlet operating conditions and the circulating compressor flow.

[0023] The beneficial effects of the present invention are as follows:

[0024] Hydrogen produced from renewable energy sources such as wind, solar, hydropower, and tidal power, also known as "green hydrogen," is a major source of future hydrogen energy. However, the volatility of renewable energy generation places special demands on the downstream green hydrogen production systems (water electrolysis and hydrogen liquefaction units). Since high-quality renewable energy sources are often located in remote, inaccessible areas, hydrogen liquefaction units that utilize renewable energy sources should utilize closed-loop low-temperature refrigeration as the cooling solution for the pre-cooling system. When the power output of hydrogen liquefaction units fluctuates significantly with renewable energy sources, the load on the pre-cooling system also fluctuates significantly, necessitating stable operation of the pre-cooling system under variable load conditions. Turbine expansion refrigeration is the most common technology for achieving refrigeration in the 70-120K temperature range. However, turbine expander efficiency decreases significantly when operating significantly outside of its design range, and surge is more likely to occur. Excessively low turbine expander inlet temperatures can cause partial liquefaction of the expanded gaseous medium, resulting in droplets that can impact and damage the high-speed impeller. Therefore, traditional turbine expansion refrigeration as a pre-cooling system for hydrogen liquefaction equipment matched with renewable energy cannot meet the working conditions of large load changes.

[0025] To solve the above problems, the present invention innovatively proposes to set up a normal temperature gas storage system at the room temperature end of the refrigeration cycle and a low temperature liquefied gas storage tank at the low temperature end. When the pre-cooling system is under low load, the normal temperature gas storage system will add the stored gaseous pre-cooling medium to the refrigeration cycle. While maintaining the stable temperature, pressure and flow of the refrigeration cycle, the pre-cooling medium will be cooled and liquefied by using the extra refrigeration capacity due to the load reduction, and stored in the low temperature liquefied gas storage tank. When the pre-cooling system is under high load, the low temperature liquefied gas storage tank consumes the pre-stored low temperature liquid pre-cooling medium to supplement the insufficient refrigeration capacity of the refrigeration cycle. In order to maintain the stable temperature, pressure and flow of the refrigeration cycle, the excess pre-cooling medium that has been vaporized and reheated will be recycled into the normal temperature gas storage system. This technical solution retains many advantages of turbine expansion refrigeration, such as mature technology, simple process flow, multiple key equipment suppliers, and low equipment cost. At the same time, it overcomes the disadvantage of turbine expansion refrigeration that it cannot achieve large load changes, greatly improving the working efficiency, reliability and stability of the turbine expander. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of a first embodiment of a hydrogen liquefaction precooling system suitable for variable load conditions according to the present invention.

[0027] Figure 2 This is a schematic diagram of a second embodiment of a hydrogen liquefaction precooling system suitable for variable load conditions according to the present invention.

[0028] Figure 3 This is a schematic diagram of a third embodiment of a hydrogen liquefaction precooling system suitable for variable load conditions according to the present invention.

[0029] Figure 4 This is a schematic diagram of a fourth embodiment of a hydrogen liquefaction precooling system suitable for variable load conditions according to the present invention.

[0030] The corresponding relationship between the reference numerals and component names is as follows:

[0031] 1. Normal temperature gas storage system; 2. Refrigeration cycle; 3. Precooling heat exchanger I; 4. Precooling heat exchanger II; 5. Cryogenic liquefied gas storage tank;

[0032] 10. Return air valve FV0; 11. Booster compressor; 12. Air storage container; 13. Pressure gauge PT0; 14. Low-pressure air supply valve FV1; 15. High-pressure air supply valve FV2; 16. Air supply pump; 17. Purifier; 100. Return air interface; 101. Air supply interface;

[0033] 20. Circulating compressor; 21. Bypass valve FV3; 22. Pressure gauge PT1; 23. Turbine expander; 24. Pressure gauge PT2; 25. Throttle valve JTV1; 26. Throttle valve JTV0; 27. Pressure gauge PT3; 28. Throttle valve JTV2; 200. Working fluid recovery port; 201. Working fluid replenishment port; 202. Liquid outlet port;

[0034] 30. Low-pressure pre-cooling medium channel; 31. High-pressure pre-cooling medium channel; 32. Air supply channel;

[0035] 40. Low temperature liquid pre-cooling working medium channel;

[0036] 500. Liquid inlet interface; 501. Liquid supply interface; 502. Steam return interface; 503. Gas outlet interface. DETAILED DESCRIPTION

[0037] To make the purpose, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings of the embodiments of the present invention. However, the embodiments described are only some embodiments of the present invention, not all. Based on the embodiments of the present invention, other embodiments that are not creative work by those skilled in the art are within the scope of protection of the present invention.

[0038] Implementation Case 1:

[0039] like Figure 1 As shown, a hydrogen liquefaction precooling system suitable for variable load working conditions includes a normal temperature gas storage system (1), a refrigeration cycle (2), a precooling heat exchanger I (3), a precooling heat exchanger II (4) and a low temperature liquefied gas storage tank (5).

[0040] The hydrogen liquefaction precooling system is filled with a precooling medium. In this embodiment, the precooling medium is nitrogen.

[0041] The normal temperature gas storage system (1) is provided with a return air interface (100) and a gas supply interface (101); the refrigeration cycle (2) is provided with a working medium recovery interface (200), a working medium replenishment interface (201) and a liquid outlet interface (202); the precooling heat exchanger I (3) is provided with a low-pressure precooling working medium channel (30); the precooling heat exchanger II (4) is provided with a low-temperature liquid precooling working medium channel (40); the top of the low-temperature liquefied gas storage tank (5) is provided with a liquid inlet interface (500) and a gas outlet interface (503), and the bottom is provided with a liquid supply interface (501).

[0042] The return air interface (100) of the normal temperature gas storage system (1) is connected to the working medium recovery interface (200) of the refrigeration cycle (2), and the air supply interface (101) of the normal temperature gas storage system (1) is connected to the working medium supply interface (201) of the refrigeration cycle (2); the refrigeration cycle (2) is coupled with the main refrigeration system and the liquefaction system in the hydrogen liquefaction device through the precooling heat exchanger I (3) and the precooling heat exchanger II (4); the liquid inlet interface (500) of the low temperature liquefied gas storage tank (5) is connected to the liquid outlet interface (202) of the refrigeration cycle, the liquid supply interface (501) of the low temperature liquefied gas storage tank (5) is connected to the cold end inlet of the low temperature liquid precooling working medium channel (40) of the precooling heat exchanger II (4), and the gas outlet interface (503) of the low temperature liquefied gas storage tank (5) is connected to the cold end inlet of the low pressure precooling working medium channel (30) of the precooling heat exchanger I (3).

[0043] The working principle of using this embodiment to provide pre-cooling for a hydrogen liquefaction device under variable load conditions is as follows:

[0044] The high pressure side pressure of the refrigeration cycle (2) is p h =10~50bar, low pressure side pressure is p l =1atm; the refrigeration cycle (2) realizes refrigeration and liquefaction by compression, precooling and expansion of nitrogen as a working medium, and the liquefied nitrogen is stored in a low-temperature liquefied gas storage tank (5), wherein the low-temperature liquid nitrogen is drawn out from the liquid supply interface (501) at the bottom of the low-temperature liquefied gas storage tank (5), enters the low-temperature liquid precooling working medium flow channel (40) of the precooling heat exchanger II (4) to be vaporized, and provides precooling of nitrogen boiling point temperature Tb(pl)=77.4K to the main refrigeration system and liquefaction system of the hydrogen liquefaction device; and the cold nitrogen in the low-temperature liquefied gas storage tank (5) is drawn out from the gas outlet interface (503) at the top, enters the low-pressure precooling working medium flow channel (30) of the precooling heat exchanger I (3) to be reheated and release cold energy, and provides the main refrigeration system and liquefaction system of the hydrogen liquefaction device with a temperature of room temperature T amb Until nitrogen is at boiling point T b (p l )=77.4K pre-cooling.

[0045] The function of the normal temperature gas storage system (1) is to store a large amount of nitrogen. When the pre-cooling system is in a high-load working condition, the liquid nitrogen stored in the low-temperature liquefied gas storage tank (5) is consumed in large quantities and vaporized into gaseous nitrogen, the liquid level drops, and the pressure in the refrigeration cycle (2) and the low-temperature liquefied gas storage tank (5) increases; the nitrogen in the refrigeration cycle (2) will be recovered through the return air interface (100) and stored in the normal temperature gas storage system (1), thereby maintaining the pressure in the refrigeration cycle (2) stable. On the contrary, when the pre-cooling system is in a low-load working condition, the refrigeration cycle (2) uses the additional refrigeration capacity to cool and produce liquid nitrogen and store it in the low-temperature liquefied gas storage tank (5), the gaseous nitrogen in the refrigeration cycle (2) and the low-temperature liquefied gas storage tank (5) decreases, and the pressure decreases; at this time, the nitrogen stored in the normal temperature gas storage system (1) will be supplemented to the refrigeration cycle through the gas supply interface (101) to maintain the pressure of the refrigeration cycle (2).

[0046] Implementation Case 2:

[0047] like Figure 2 As shown, a schematic diagram of a hydrogen liquefaction precooling system suitable for variable load conditions includes a normal temperature gas storage system (1), a refrigeration cycle (2), a precooling heat exchanger I (3), a precooling heat exchanger II (4) and a low temperature liquefied gas storage tank (5).

[0048] The hydrogen liquefaction precooling system is filled with a precooling medium. In this embodiment, the precooling medium is nitrogen.

[0049] The normal temperature gas storage system (1) comprises a return air interface (100), a return air valve FV0 (10), a booster compressor (11), a gas storage container (12), a pressure gauge PT0 (13), a low pressure gas supply valve FV1 (14), a high pressure gas supply valve FV2 (15) and a gas supply interface (101). The gas storage container (12) is a gas storage container with a maximum storage pressure of p 0_max pressure vessel.

[0050] The refrigeration cycle (2) is provided with a circulation compressor (20), a bypass valve FV3 (21), a pressure gauge PT1 (22), a turbine expander (23), a pressure gauge PT2 (24), a throttle valve JTV1 (25), a throttle valve JTV0 (26), a working fluid recovery interface (200), a working fluid replenishment interface (201) and a liquid outlet interface (202).

[0051] A low-pressure pre-cooling working medium channel (30) and a high-pressure pre-cooling working medium channel (31) are provided in the pre-cooling heat exchanger I (3).

[0052] A low-temperature liquid pre-cooling medium channel (40) is provided in the pre-cooling heat exchanger II (4).

[0053] The top of the cryogenic liquefied gas storage tank (5) is provided with a liquid inlet interface (500), a steam return interface (502) and a gas outlet interface (503), and the bottom is provided with a liquid supply interface (501).

[0054] The return air interface (100), the return air valve FV0 (10), the booster compressor (11), the air storage container (12), the low-pressure air supply valve FV1 (14) and the air supply interface (101) are connected in sequence through pipelines; the pressure gauge PT0 (13) is arranged on the air storage container (12); the high-pressure air supply valve FV2 (15) is connected to the upstream pipeline of the low-pressure air supply valve FV1 (14) and the return air interface (100) through a pipeline; the return air interface (100) is connected to the working medium recovery interface (200), and the air supply interface (101) is connected to the working medium replenishment interface (201).

[0055] The high-pressure outlet of the circulating compressor (20), the high-temperature end inlet of the high-pressure pre-cooling working medium channel (31), the low-temperature end outlet of the high-pressure pre-cooling working medium channel (31), the turbine expander (23), the throttle valve JTV1 (25), the liquid outlet interface (202) and the liquid inlet interface (500) are sequentially connected through pipelines; the liquid supply interface (501), the low-temperature end inlet of the low-temperature liquid pre-cooling working medium channel (40), the high-temperature end outlet of the low-temperature liquid pre-cooling working medium channel (40) and the steam return interface (502) are sequentially connected through pipelines; the gas outlet interface (503), the low-temperature end inlet of the low-pressure pre-cooling working medium channel (30), the high-temperature end outlet of the low-pressure pre-cooling working medium channel (30) and the low-pressure inlet of the circulating compressor (20) are sequentially connected through pipelines. The bypass valve FV3 (21) is connected to the pipelines of the low-pressure inlet and the high-pressure outlet of the circulation compressor (20); the throttle valve JTV0 (26) is connected to the pipelines of the turbine expander (23) inlet and the throttle valve JTV1 (25) outlet; the pressure gauge PT1 (22) is arranged on the high-pressure outlet pipeline of the circulation compressor (20), the pressure gauge PT2 (24) is arranged on the outlet pipeline of the turbine expander (23), and the pressure gauge PT3 (27) is arranged on the low-pressure inlet pipeline of the circulation compressor (20); the working medium recovery interface (200) is arranged on the high-pressure outlet end pipeline of the circulation compressor (20), and the working medium replenishment interface (201) is arranged on the low-pressure inlet end pipeline of the circulation compressor (20).

[0056] The working principle of using this embodiment to provide pre-cooling for a hydrogen liquefaction device under variable load conditions is as follows:

[0057] The pre-cooling working medium nitrogen passes through the circulation compressor (20) from the low pressure p l Compression to high pressure p h First, it passes through the high-pressure pre-cooling medium channel (31) in the pre-cooling heat exchanger I (3) and is pre-cooled by the low-pressure nitrogen gas with a lower temperature. Then, the pre-cooled cold nitrogen gas enters the turbine expander (23) and is expanded to the intermediate pressure p m, its temperature drops; then it enters the throttle valve JTV1 (25) and expands again to the low pressure p l The nitrogen gas that has undergone secondary expansion through the throttle valve JTV1 (25) is further cooled and partially liquefied, and the saturated nitrogen gas in vapor and liquid phases enters the cryogenic liquefied gas storage tank (5) through the liquid outlet interface (202) and the liquid inlet interface (500); the liquid nitrogen in the cryogenic liquefied gas storage tank (5) enters the cryogenic liquid precooling medium channel (40) of the precooling heat exchanger II (4) through the liquid supply interface (501) at the bottom under the action of gravity and thermal siphon, and the vaporized phase changes to gaseous state, providing the precooling medium with a boiling point temperature T to the main refrigeration system and liquefaction system of the hydrogen liquefaction device. b (p l )=77.4K pre-cooling, the vaporized cold nitrogen returns to the cryogenic liquefied gas storage tank (5) through the return steam interface (502); the saturated gaseous nitrogen at the top of the cryogenic liquefied gas storage tank (5) enters the low-pressure pre-cooling working medium flow channel (30) in the pre-cooling heat exchanger I (3) through the outlet interface (503), providing room temperature T for the inflowing high-pressure and high-temperature nitrogen and the main refrigeration system and liquefaction system of the hydrogen liquefaction device amb To the boiling point of the pre-cooling medium T b (p l )=77.4K temperature zone pre-cooling; the reheated low-pressure nitrogen is finally returned to the low-pressure inlet of the circulation compressor (20), forming a cycle; by controlling the opening of the bypass valve FV3 (21), the flow rate of the circulation compressor (20) under variable load conditions can be regulated; by controlling the opening of the throttle valve JTV0 (26), the flow rate of the turbine expander (23) under variable load conditions can be regulated and stabilized.

[0058] When the precooling system is under high load:

[0059] The high load of the precooling heat exchanger II (4) causes the liquid nitrogen passing through the cryogenic liquid precooling medium flow channel (40) to evaporate more violently, and the thermal siphon force is greater, which spontaneously increases the liquid nitrogen flow through the cryogenic liquid precooling medium flow channel (40), and more liquid nitrogen is consumed, and the cooling capacity of the precooling heat exchanger II (4) increases, which also causes the liquid nitrogen level in the cryogenic liquefied gas storage tank (5) to continuously decrease, causing the high-pressure side pressure p of the refrigeration cycle (2) to increase. h and low pressure side pressure p l All increased.

[0060] At this time, the return air valve FV0 (10) is opened, the booster compressor (11) is started, the low-pressure air supply valve FV1 (14) and the high-pressure air supply valve (15) are closed, and the excess room-temperature gaseous nitrogen in the refrigeration cycle (2) enters the booster compressor (11) through the working fluid recovery interface (200), the return air interface (100), and the return air valve FV0 (10), is compressed to the storage pressure p0, and is stored in the gas storage container (12); the opening of the return air valve FV0 (10) is adjusted to control the return air flow rate to maintain the high-pressure side pressure p0 of the refrigeration cycle (2). h .

[0061] By closing the bypass valve FV3 (21) or reducing its opening, the flow rate of the cold nitrogen gas from the cryogenic liquefied gas storage tank (5) into the low-pressure pre-cooling working medium flow channel (30) of the pre-cooling heat exchanger I (3) via the gas outlet interface (503) is increased to maintain the low-pressure side pressure p of the refrigeration cycle (2). l ;

[0062] If the total cooling capacity increased by the increase in the flow rate of cold nitrogen gas entering the low-pressure pre-cooling medium flow channel (30) of the pre-cooling heat exchanger I (3) is sufficient to meet the load increase of the pre-cooling heat exchanger I (3), the pressure and temperature at the inlet end of the turbine expander (23) remain basically unchanged, and thus can be maintained at a stable design operating condition; if the total cooling capacity increased by the increase in the flow rate of cold nitrogen gas entering the low-pressure pre-cooling medium flow channel (30) of the pre-cooling heat exchanger I (3) is insufficient to meet the load increase of the pre-cooling heat exchanger I (3), the temperature at the inlet end of the turbine expander (23) will increase. At this time, it is necessary to further increase the opening of the return air valve FV0 (10), increase the return air flow rate, and reduce the high-pressure side pressure p of the refrigeration cycle (2). h , i.e., the pressure at the inlet of the turbine expander (23); on the other hand, such control reduces the flow of the high-pressure precooling medium flow channel (31) through the precooling heat exchanger I (3), which can reduce the temperature at the inlet end of the turbine expander (23), so that the turbine expander (23) does not deviate too far from the stable operating condition.

[0063] When the precooling system is in low load condition:

[0064] The load of the precooling heat exchanger II (4) is reduced, so that the evaporation amount of liquid nitrogen passing through its cryogenic liquid precooling medium flow channel (40) is reduced, and the thermal siphon force is effective, which spontaneously reduces the flow rate of liquid nitrogen passing through the cryogenic liquid precooling medium flow channel (40), and the cooling capacity of the precooling heat exchanger II (4) is reduced. Extra liquid nitrogen is produced and stored in the cryogenic liquefied gas storage tank (5), and the liquid nitrogen level increases, which causes the high-pressure side pressure p of the refrigeration cycle (2) to increase. h and low pressure side pressure p l All decreased;

[0065] Close the return valve FV0 (10) and the booster compressor (11). If the gas pressure p0 in the gas storage container (12) is higher than the high pressure side pressure p h When the low-pressure air supply valve FV1 (14) is closed and the high-pressure air supply valve FV2 (15) is opened, the normal-temperature nitrogen is supplied to the refrigeration cycle from the return air interface (100) and the working fluid recovery interface (200); when the gas storage pressure p0 in the gas storage container (12) gradually decreases and becomes lower than the high-pressure side pressure p h When the high pressure air supply valve FV2 (15) is closed, the low pressure air supply valve FV1 (14) is opened, and the nitrogen at room temperature is supplied to the refrigeration cycle through the self-supply air interface and the working fluid supply interface; the opening of the bypass valve FV3 (21) is controlled, and the high pressure side pressure p of the refrigeration cycle (2) is maintained. h and low pressure side pressure p l .

[0066] As the bypass valve FV3 (21) is opened, the flow rate of cold nitrogen in the cryogenic liquefied gas storage tank (5) entering the low-pressure pre-cooling working medium flow channel (30) of the pre-cooling heat exchanger I (3) through the gas outlet interface (503) increases.

[0067] If the total cooling capacity is reduced due to the reduction in the flow rate of the cold nitrogen gas entering the low-pressure pre-cooling working medium flow channel (30) of the pre-cooling heat exchanger I (3) is smaller than the load reduction of the pre-cooling heat exchanger I (3), the pressure and temperature at the inlet end of the turbine expander (23) remain substantially unchanged, the opening degree of the throttle valve JTV0 (26) is opened and controlled so that the flow rate of the turbine expander (23) remains unchanged, and the excess nitrogen flow is throttled and cooled through the throttle valve JTV0 (26) and partially liquefied before merging with the nitrogen flow from the turbine expander (23) and the throttle valve JTV1 (25);

[0068] If the total cooling capacity is reduced due to the reduction in the flow rate of cold nitrogen entering the low-pressure pre-cooling working medium flow channel (30) of the pre-cooling heat exchanger I (3) than the load reduction of the pre-cooling heat exchanger I (3), the temperature at the inlet end of the turbine expander (23) will increase. At this time, the throttle valve JTV0 (26) should be closed, and the opening of the low-pressure air supply valve FV1 (14) or the high-pressure air supply valve FV2 (15) should be reduced, and the opening of the bypass valve FV3 (21) should be increased to reduce the high-pressure side pressure p of the refrigeration cycle (2). h , i.e., the pressure at the inlet of the turbine expander (23); on the other hand, such control reduces the flow of the high-pressure precooling medium flow channel (31) through the precooling heat exchanger I (3), which can reduce the temperature at the inlet end of the turbine expander (23), so that the turbine expander (23) does not deviate too far from the stable operating condition.

[0069] Implementation Case 3:

[0070] like Figure 3 As shown, a hydrogen liquefaction precooling system suitable for variable load conditions is different from Implementation Case 2 in that:

[0071] The normal temperature gas storage system (1) is provided with a return air interface (100), a return air valve FV0 (10), a gas storage container (12), an air supply pump (16), a purifier (17), a low-pressure air supply valve FV1 (14) and a gas supply interface (101); wherein the gas storage container (12) is a normal pressure gas bag.

[0072] When the pre-cooling system is in a high-load condition, the return air valve FV0 (10) is opened, the low-pressure air supply valve FV1 (14) and the air supply pump (16) are closed, and the excess room-temperature gaseous nitrogen in the refrigeration cycle (2) is depressurized through the working medium recovery interface (200), the return air interface (100), and the return air valve FV0 (10) and stored in the gas storage container (12); the opening of the return air valve FV0 (10) is adjusted to control the return air flow rate to maintain the high-pressure side pressure p of the refrigeration cycle (2) h .

[0073] When the pre-cooling system is in a low-load condition, the return air valve FV0 (10) is closed, the low-pressure air supply valve FV1 (14) and the air supply pump (16) are opened, and the nitrogen gas at normal temperature and pressure in the gas storage container (12) is pressurized, purified by the purifier (17), and then supplied to the refrigeration cycle (2) through the air supply interface (101) and the working medium supply interface (201); the opening of the bypass valve FV3 (21) is controlled, and the high-pressure side pressure p of the refrigeration cycle (2) is maintained. h and low pressure side pressure p l .

[0074] Implementation Case 4:

[0075] like Figure 4 As shown, a hydrogen liquefaction precooling system suitable for variable load conditions is different from the embodiment 2 in that: the high-pressure air supply valve FV2 (15) is cancelled in the normal temperature gas storage system (1); the throttle valve JTV0 (26) is cancelled in the refrigeration cycle (2); the throttle valve JTV2 (28) is also provided in the refrigeration cycle (2); the precooling heat exchanger I (3) also includes an air supply channel (32); wherein the working medium supply interface (201), the high-temperature end inlet of the air supply channel (32), the low-temperature end outlet of the air supply channel (32), the throttle valve JTV2 (28) and the outlet of the turbine expander (23) are connected in sequence through pipelines.

[0076] When the pre-cooling system is in low-load operation, the return air valve FV0 (10) and the booster compressor (11) are closed, and the air supply valve FV1 (14) is opened. The high-pressure room-temperature nitrogen gas pre-stored in the gas storage container (12) enters the air supply channel (32) in the pre-cooling heat exchanger I (3) through the air supply interface (101) and the working medium supply interface (201), is pre-cooled by the refluxed low-pressure cold nitrogen gas, and then throttled and expanded by the throttle valve JTV2 (28) and merged with the main circulation fluid from the turbine expander (23), and then enters the throttle valve JTV1 (25) for further throttling and expansion.

Claims

1. A hydrogen liquefaction precooling system suitable for variable load conditions, characterized in that: The precooling system includes a normal temperature gas storage system, a refrigeration cycle, a precooling heat exchanger I, a precooling heat exchanger II and a low temperature liquefied gas storage tank; The pre-cooling system is filled with a pre-cooling medium; The normal temperature gas storage system is provided with a return air interface and a gas supply interface; The refrigeration cycle is provided with a working medium recovery interface, a working medium replenishment interface and a liquid outlet interface; The top of the cryogenic liquefied gas storage tank is provided with a liquid inlet interface and a gas outlet interface, and the bottom is provided with a liquid supply interface; The precooling heat exchanger 1 is provided with a low-pressure precooling working medium channel; The precooling heat exchanger II is provided with a low-temperature liquid precooling medium channel; The return air interface of the normal temperature gas storage system is connected to the working medium recovery interface of the refrigeration cycle, and the air supply interface of the normal temperature gas storage system is connected to the working medium supply interface of the refrigeration cycle; the liquid inlet interface of the low temperature liquefied gas storage tank is connected to the liquid outlet interface of the refrigeration cycle, the liquid supply interface of the low temperature liquefied gas storage tank is connected to the cold end inlet of the low temperature liquid pre-cooling working medium channel of the pre-cooling heat exchanger II, and the air outlet interface of the low temperature liquefied gas storage tank is connected to the cold end inlet of the low pressure pre-cooling working medium channel of the pre-cooling heat exchanger I; the refrigeration cycle is coupled with the main refrigeration system and the liquefaction system in the hydrogen liquefaction device through the pre-cooling heat exchanger I to provide a temperature from room temperature T amb To the boiling point of the pre-cooling medium T b The refrigeration cycle is coupled with the main refrigeration system and liquefaction system in the hydrogen liquefaction device through the precooling heat exchanger II to provide a precooling working fluid boiling point temperature T b Pre-cooling.

2. The hydrogen liquefaction precooling system suitable for variable load conditions according to claim 1, characterized in that: The pre-cooling medium is methane, nitrogen, hydrogen, argon, neon, helium or a mixture of the above gases.

3. The hydrogen liquefaction precooling system suitable for variable load conditions according to claim 1, characterized in that: The normal temperature gas storage system also includes a return air valve FV0, a ​​booster compressor, a gas storage container, a pressure gauge PT0 and a low-pressure gas supply valve FV1; The return air interface, return air valve FV0, booster compressor, air storage container, low-pressure air supply valve FV1 and air supply interface are connected in sequence through pipelines; The pressure gauge PT0 is arranged on the gas storage container; The gas storage container is a pressure container, and the pressure container is a seamless steel cylinder, a welded steel cylinder, a hoop-wound composite material gas cylinder, a fully-wound composite material gas cylinder, or a steel strip-wound container.

4. The hydrogen liquefaction precooling system suitable for variable load conditions according to claim 3, characterized in that: The normal temperature gas storage system further includes a high-pressure gas supply valve FV2 , which is connected to an upstream pipeline of the low-pressure gas supply valve FV1 and a return air interface via a pipeline.

5. The hydrogen liquefaction precooling system suitable for variable load conditions according to claim 1, characterized in that: The normal temperature gas storage system further comprises a return air valve FV0, a ​​gas storage container, an air supply pump, a purifier and a low pressure air supply valve FV1; The return air interface, return air valve FV0, air storage container, air supply pump, purifier, low-pressure air supply valve FV1 and air supply interface are connected in sequence through pipelines; The gas storage container is a normal pressure gas bag.

6. The hydrogen liquefaction precooling system suitable for variable load conditions according to any one of claims 1 to 5, characterized in that: The refrigeration cycle also includes a circulation compressor, a turbine expander, a throttle valve JTV1 and a liquid outlet interface; The precooling heat exchanger 1 is provided with a high-pressure precooling medium channel; The top of the cryogenic liquefied gas storage tank is also provided with a steam return interface; The high-pressure outlet of the circulating compressor, the high-temperature inlet of the high-pressure pre-cooling working medium channel, the low-temperature outlet of the high-pressure pre-cooling working medium channel, the turbine expander, the throttle valve JTV1, the liquid outlet interface and the liquid inlet interface are connected in sequence through pipelines; The liquid supply interface, the low-temperature end inlet of the low-temperature liquid pre-cooling working medium channel, the high-temperature end outlet of the low-temperature liquid pre-cooling working medium channel and the steam return interface are connected in sequence through pipelines; The gas outlet interface, the low-temperature end inlet of the low-pressure pre-cooling working medium channel, the high-temperature end outlet of the low-pressure pre-cooling working medium channel and the low-pressure inlet of the circulating compressor are connected in sequence through pipelines; The working medium recovery interface is arranged on the pipeline at the high-pressure outlet end of the circulation compressor, and the working medium replenishment interface is arranged on the pipeline at the low-pressure inlet end of the circulation compressor.

7. The hydrogen liquefaction precooling system suitable for variable load conditions according to claim 6, characterized in that: The refrigeration cycle further includes a bypass valve FV3; the bypass valve FV3 is connected to the pipeline of the low-pressure inlet and the high-pressure outlet of the circulation compressor.

8. The hydrogen liquefaction precooling system suitable for variable load conditions according to claim 6, characterized in that: The refrigeration cycle further includes a throttle valve JTV0 , which is connected to a pipeline between an inlet of the turbine expander and an outlet of the throttle valve JTV1 .

9. The hydrogen liquefaction precooling system suitable for variable load conditions according to claim 6, characterized in that: The refrigeration cycle further includes a pressure gauge PT1, a pressure gauge PT2 and a pressure gauge PT3; the pressure gauge PT1 is arranged on the high-pressure outlet pipeline of the circulation compressor, the pressure gauge PT2 is arranged on the turbine expander outlet pipeline, and the pressure gauge PT3 is arranged on the low-pressure inlet pipeline of the circulation compressor.

10. The hydrogen liquefaction precooling system suitable for variable load conditions according to any one of claims 1 to 3, characterized in that: The refrigeration cycle also includes a throttle valve JTV2; The precooling heat exchanger 1 is also provided with an air supply channel; The working fluid supply interface, the air supply channel, the throttle valve JTV2 and the outlet of the turbine expander are connected in sequence through pipelines; The refrigeration cycle also includes a circulation compressor, a turbine expander, a throttle valve JTV1 and a liquid outlet interface; The precooling heat exchanger 1 is also provided with a high-pressure precooling medium channel; The top of the cryogenic liquefied gas storage tank is also provided with a steam return interface; The high-pressure outlet of the circulating compressor, the high-temperature inlet of the high-pressure pre-cooling working medium channel, the low-temperature outlet of the high-pressure pre-cooling working medium channel, the turbine expander, the throttle valve JTV1, the liquid outlet interface and the liquid inlet interface are connected in sequence through pipelines; The liquid supply interface, the low-temperature end inlet of the low-temperature liquid pre-cooling working medium channel, the high-temperature end outlet of the low-temperature liquid pre-cooling working medium channel and the steam return interface are connected in sequence through pipelines; The gas outlet interface, the low-temperature end inlet of the low-pressure pre-cooling working medium channel, the high-temperature end outlet of the low-pressure pre-cooling working medium channel and the low-pressure inlet of the circulating compressor are connected in sequence through pipelines; The working medium recovery interface is provided on the high-pressure outlet pipeline of the circulating compressor; The refrigeration cycle further includes a bypass valve FV3 , which is connected to a pipeline of a low-pressure inlet and a high-pressure outlet of the circulation compressor.

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