Refrigerating system and control method thereof

Abstract

The invention provides a refrigerating system and a control method thereof. The refrigerating system comprises a first-stage heat exchanger, at least one second-stage heat exchanger and a controller. The first-stage heat exchanger is provided with a first heat release channel and a first heat absorption channel which are not communicated. And the gaseous methane can exchange heat with the liquid nitrogen in the first-stage heat exchanger. And an outlet of the first heat release channel is used for outputting liquid methane. The second-stage heat exchanger is provided with a second heat release channel and a second heat absorption channel which are not communicated. An inlet of the second heat absorption channel communicates with an outlet of the first heat release channel. And the liquid methane can exchange heat with the to-be-rectified substance in the second-stage heat exchanger. And an outlet of the second heat absorption channel communicates with an inlet of the first heat release channel, so that gaseous methane obtained after liquid methane is vaporized is introduced into the first heat release channel. And the outlet of the second heat release channel is used for introducing the liquefied to-be-rectified substance into the rectifying tower. The controller is used for controlling operation of the refrigerating system. According to the refrigerating system, the temperature requirement of low-temperature refrigeration is met, and the cost is reduced.

Description

Technical Field

[0001] The present application relates to the field of cryogenic distillation technology, and in particular to a refrigeration system and a control method thereof. Background Art

[0002] Cryogenic distillation is a widely used process in petroleum, chemical, and pharmaceutical production. Cryogenic distillation utilizes the differences in boiling points of various components at specific temperatures and pressures to separate light and heavy components. Typically, the required refrigeration temperature for cryogenic distillation reaches -100°C.

[0003] In the related art, a low-temperature refrigerator, such as a Stirling refrigerator or a GM refrigerator, is usually used to provide low-temperature refrigeration for the low-temperature distillation process, but the cost of the low-temperature refrigerator is relatively high. Summary of the Invention

[0004] In view of this, embodiments of the present application hope to provide a refrigeration system and a control method thereof to replace a low-temperature refrigerator to provide refrigeration in a low-temperature temperature range for a low-temperature distillation process.

[0005] To achieve the above objectives, a first aspect of an embodiment of the present application provides a refrigeration system, comprising:

[0006] A primary heat exchanger having a first heat release channel and a first heat absorption channel that are not connected to each other, the inlet of the first heat release channel being used to introduce gaseous methane, and the inlet of the first heat absorption channel being used to introduce liquid nitrogen, so that gaseous methane can exchange heat with liquid nitrogen in the primary heat exchanger, the outlet of the first heat release channel being used to output liquid methane, and the outlet of the first heat absorption channel being connected to the external environment, so as to discharge nitrogen formed after vaporization of the liquid nitrogen to the external environment;

[0007] At least one secondary heat exchanger, the secondary heat exchanger having a second heat release channel and a second heat absorption channel that are not connected to each other, the inlet of the second heat absorption channel being connected to the outlet of the first heat release channel for admitting liquid methane, the inlet of the second heat release channel being used for admitting a substance to be distilled, the liquid methane being able to exchange heat with the substance to be distilled in the secondary heat exchanger, the outlet of the second heat absorption channel being connected to the inlet of the first heat release channel for passing gaseous methane formed after vaporization of the liquid methane into the first heat release channel, and the outlet of the second heat release channel being used for passing the liquefied substance to be distilled into the distillation column;

[0008] A controller is used to control the operation of the refrigeration system.

[0009] In some embodiments, the refrigeration system includes a first regulating valve and a first pressure sensor, the first pressure sensor is arranged at the inlet of the first heat release channel, and the first regulating valve is arranged at the inlet of the first heat absorption channel. The first pressure sensor is used to detect the pressure of the gaseous methane at the inlet of the first heat release channel and transmit it to the controller. The controller can control the first regulating valve to adjust the input speed of liquid nitrogen according to the pressure signal of the first pressure sensor.

[0010] In some embodiments, the refrigeration system includes a second regulating valve and a second pressure sensor, and the second pressure sensor and the second regulating valve are arranged at the outlet of the first heat absorption channel. The second pressure sensor is used to detect the pressure of the nitrogen at the outlet of the first heat absorption channel and transmit it to the controller. The controller can control the second regulating valve to adjust the nitrogen exhaust speed according to the pressure signal of the second pressure sensor.

[0011] In some embodiments, the refrigeration system includes a first branch, the inlet of the second heat absorption channel is connected to the outlet of the first heat release channel through the first branch, and the refrigeration system includes a liquid tank and a liquid pump, the liquid tank and the liquid pump are arranged on the first branch, the liquid tank is used to receive liquid methane flowing out of the outlet of the first heat release channel, and the liquid pump pumps the liquid methane in the liquid tank to the inlet of the second heat absorption channel.

[0012] In some embodiments, the refrigeration system includes a liquid level sensor, which is disposed in the liquid tank and is used to detect liquid level information of the liquid methane in the liquid tank and transmit the information to the controller;

[0013] The controller is configured to control the disconnection of the liquid tank from the secondary heat exchanger when the liquid level information of the liquid methane in the liquid tank is lower than a first preset value; and to control the liquid tank to deliver liquid methane to the secondary heat exchanger when the liquid level information of the liquid methane in the liquid tank is not less than the first preset value;

[0014] The refrigeration system is provided with a methane supply port, which is used at least to replenish gaseous methane to the first heat release channel when the liquid level information of the liquid methane in the liquid tank is lower than a first preset value.

[0015] In some embodiments, the refrigeration system includes a second branch for transporting gaseous methane vaporized under the pressure of the liquid pump to the liquid tank.

[0016] In some embodiments, the refrigeration system includes a gas concentration detector, which is disposed outside the liquid tank and is used to detect whether gaseous methane in the liquid tank is leaking.

[0017] In some embodiments, the refrigeration system includes a third pressure sensor and a solenoid valve. The third pressure sensor is arranged in the liquid tank, and is used to detect the pressure of the gaseous methane in the liquid tank and transmit it to the controller. The controller is used to control the solenoid valve to open when the pressure of the gaseous methane in the liquid tank exceeds a set value, so as to discharge the gaseous methane in the liquid tank to the external environment.

[0018] In some embodiments, the refrigeration system includes a third branch, a fourth pressure sensor and a third regulating valve. The outlet of the liquid pump is connected to the liquid tank through the third branch. The third regulating valve and the fourth pressure sensor are arranged on the third branch. The fourth pressure sensor is used to detect the pressure of the liquid methane at the outlet of the liquid pump and transmit it to the controller. The controller is used to control the third regulating valve to adjust the pressure at the outlet of the liquid pump according to the pressure signal of the fourth pressure sensor.

[0019] In some embodiments, the refrigeration system includes a flow sensor and a fourth regulating valve, which are arranged at the inlet of the second heat absorption channel. The flow sensor is used to detect the flow of liquid methane at the inlet of the second heat absorption channel and transmit it to the controller. The controller is used to control the fourth regulating valve to adjust the delivery rate of liquid methane according to the flow signal of the flow sensor.

[0020] In some embodiments, the refrigeration system includes a fifth pressure sensor and a fifth regulating valve. The fifth pressure sensor is arranged at the outlet of the second heat absorption channel. The fifth pressure sensor is used to detect the pressure of the gaseous methane at the outlet of the second heat absorption channel and transmit it to the controller. The controller is used to control the fifth regulating valve to adjust the output rate of the gaseous methane according to the pressure signal of the fifth pressure sensor.

[0021] In some embodiments, the at least one secondary heat exchanger includes a first heat exchanger, a second heat exchanger, and a third heat exchanger; the first branch includes a first main line, a first branch line, a second branch line, and a third branch line; the liquid tank and the liquid pump are provided on the first main line; one end of the first branch line, the second branch line, and the third branch line are respectively used to connect to the first main line; and the other ends of the first branch line, the second branch line, and the third branch line are respectively used to connect to the first heat exchanger, the second heat exchanger, and the third heat exchanger;

[0022] The refrigeration system further includes a fourth branch, a fifth branch, and a sixth branch. The outlets of the second heat absorption channels of the first heat exchanger, the second heat exchanger, and the third heat exchanger are connected to the inlet of the first heat release channel through the fourth branch, the fifth branch, and the sixth branch, respectively.

[0023] A second aspect of an embodiment of the present application provides a control method for a refrigeration system, which is applied to any of the above refrigeration systems. The control method includes:

[0024] Obtaining liquid level information of a liquid tank of the refrigeration system;

[0025] Determine whether the liquid level information exceeds a first preset value. If so, control the liquid tank to deliver liquid methane to the secondary heat exchanger. If not, control the outlet of the liquid tank to close, and control the methane supply port of the refrigeration system to replenish gaseous methane to the first heat release channel.

[0026] In some embodiments, after controlling the liquid tank to deliver liquid methane to the secondary heat exchanger, the control method further includes:

[0027] Collecting data signals from the liquid tank, the primary heat exchanger, and the secondary heat exchanger of the refrigeration system;

[0028] Determine whether the data signal exceeds a preset range; if so, adjust the input rate of liquid nitrogen and / or the discharge rate of nitrogen and / or the output rate of liquid methane and / or the output rate of gaseous methane so that the data signal is within the preset range; wherein the data signal includes at least one of a pressure signal, a temperature signal, and a flow signal.

[0029] The refrigeration system provided in an embodiment of the present application comprises a primary heat exchanger and at least one secondary heat exchanger. Liquid nitrogen is used to condense gaseous methane into liquid methane in the primary heat exchanger. The inlet of the second heat absorption channel of the secondary heat exchanger is connected to the outlet of the first heat release channel of the primary heat exchanger, thereby allowing the liquid methane condensed by the primary heat exchanger to enter. The liquid methane in the second heat absorption channel absorbs heat and vaporizes into gaseous methane, which is then returned to the primary heat exchanger for condensation. The liquid methane liquefies the material to be distilled in the second heat release channel of the secondary heat exchanger. For example, the material to be distilled is condensed into liquid and returned to the cryogenic distillation tower, where reverse gas-liquid exchange continues, achieving separation of light and heavy components of the material to be distilled. A controller can improve the reliability of the circulation between the primary and secondary heat exchangers by comprehensively controlling the parameters of the primary and secondary heat exchangers. By combining methane and liquid nitrogen, the refrigeration system does not require additional refrigerant or a compressor, and can meet the temperature range requirements of cryogenic distillation, reducing equipment and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the structure of a refrigeration system provided in one embodiment of the present application;

[0031] Figure 2 A schematic structural diagram of a refrigeration system provided in another embodiment of the present application;

[0032] Figure 3 A flow chart of a control method for a refrigeration system provided in this application;

[0033] Figure 4 A schematic flow chart of a control method for a refrigeration system provided in another embodiment of the present application.

[0034] Description of Reference Numerals

[0035] 10. Refrigeration system; 10a. Methane supply port; 11. Primary heat exchanger; 11a. First heat release channel; 11b. First heat absorption channel; 12. Secondary heat exchanger; 12a. Second heat release channel; 12b. Second heat absorption channel; 14. Liquid tank; 15. Liquid pump; V1. First regulating valve; V2. Second regulating valve; V3. Third regulating valve; V4. Fourth regulating valve; V5. Fifth regulating valve; V6. Sixth regulating valve; V7. Seventh regulating valve; V8. Eighth regulating valve; V9. Ninth regulating valve; P1. First pressure sensor; P2. Second pressure sensor; P3. Third pressure sensor; P4. Fourth pressure sensor; P5. Fifth pressure sensor;

[0036] P6, sixth pressure sensor; P7, seventh pressure sensor; L1, first flow sensor; L2, second flow sensor; L3, third flow sensor; EX1, first heat exchanger; EX2, second heat exchanger; EX3, third heat exchanger; T1, first temperature sensor; T2, second temperature sensor; T3, third temperature sensor; T4, fourth temperature sensor; T5, fifth temperature sensor; T6, sixth temperature sensor;

[0037] T7, seventh temperature sensor; T8, eighth temperature sensor; LS, liquid level sensor; GD, gas concentration detector; EV, solenoid valve. DETAILED DESCRIPTION

[0038] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0039] In the description of the embodiments of the present application, it should be noted that the terms "upper," "top," "inner," and "outer" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of the embodiments of the present application and to simplify the description. They do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present application. Furthermore, the terms "first," "second," and "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] In the description of the embodiments of this application, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of this application based on the specific circumstances.

[0041] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiments of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0042] Cryogenic distillation is a widely used process in petroleum, chemical, and pharmaceutical production. The cryogenic distillation process uses the differences in boiling points of each component at a specific temperature and pressure to separate light and heavy components. Usually, the refrigeration temperature range required for the material in cryogenic distillation reaches -100°C.

[0043] In the related art, low-temperature refrigerators, such as Stirling refrigerators or GM refrigerators, are usually used to provide low-temperature refrigeration for the low-temperature distillation process. On the one hand, the cost of low-temperature refrigerators is relatively high; on the other hand, if a conventional refrigerator with lower cost is used, it cannot meet the refrigeration temperature range required by the low-temperature distillation process.

[0044] Based on the above situation, the first aspect of the embodiment of the present application provides a refrigeration system 10, see Figure 1 and Figure 2The refrigeration system 10 includes a primary heat exchanger 11, at least one secondary heat exchanger 12, and a controller. The primary heat exchanger 11 has a first heat release channel 11a and a first heat absorption channel 11b, which are not interconnected. The inlet of the first heat release channel 11a is used to introduce gaseous methane. The inlet of the first heat absorption channel 11b is used to introduce liquid nitrogen. Gaseous methane can exchange heat with liquid nitrogen in the primary heat exchanger 11. The outlet of the first heat release channel 11a is used to output liquid methane. The outlet of the first heat absorption channel 11b is connected to the external environment and is used to discharge nitrogen gas formed after vaporization of liquid nitrogen to the external environment. The secondary heat exchanger 12 has a second heat release channel 12a and a second heat absorption channel 12b, which are not interconnected. The inlet of the second heat absorption channel 12b is connected to the outlet of the first heat release channel 11a and is used to introduce liquid methane. The inlet of the second heat release channel 12a is used to introduce a substance to be distilled. Liquid methane can exchange heat with the substance to be distilled in the secondary heat exchanger 12. The outlet of the second heat-absorbing channel 12b is connected to the inlet of the first heat-releasing channel 11a, allowing the gaseous methane formed after the liquid methane is vaporized to pass into the first heat-releasing channel 11a. The outlet of the second heat-releasing channel 12a is used to pass the liquefied material to be distilled into the distillation column. A controller is used to control the operation of the refrigeration system 10.

[0045] It should be noted that the refrigeration system 10 in the present application can be applied to low-temperature distillation systems, and can also be applied to other process production, scientific research experiments, biological sample storage, high-temperature equipment cooling, etc., without limitation here.

[0046] Illustratively, the refrigeration system 10 can serve as part of a cryogenic distillation system, and at least a portion of the secondary heat exchanger 12 of the refrigeration system 10 can be integrated with a cryogenic distillation tower of the cryogenic distillation system. The material to be distilled in the cryogenic distillation tower is directly liquefied in the secondary heat exchanger 12, and the liquefied material to be distilled can flow back to the cryogenic distillation tower.

[0047] It should be noted that the controller in the present application can be a programmable logic controller (PLC), which is connected to the host computer through a switch, wherein the host computer is used to set the parameters, data display, curve display and data storage of the refrigeration system 10; the PLC is used to collect and monitor the pressure, temperature, liquid level, flow and other signals in the refrigeration system 10 of the present application, as well as to collect and monitor the methane concentration in the environment, and to control the refrigeration system 10 in the present application.

[0048] For example, the host computer program is SIMATIC WinCC (Windows Control Center).

[0049] For example, refrigeration system 10 can communicate with a host computer via Ethernet, enabling the host computer to collect and process process parameters, display data and curves, set control parameters, store data, and implement signal alarms and interlocking functions. When a parameter exceeds a limit, the background color of the parameter changes, and an alarm device activates an audible and visual alarm.

[0050] In the present application, the first-stage heat exchanger 11 uses liquid nitrogen to cool the gaseous methane, condensing the gaseous methane into liquid methane. The liquid nitrogen absorbs heat and becomes nitrogen and is discharged from the first-stage heat exchanger 11. The second-stage heat exchanger 12 in the present application uses the liquid methane output by the first-stage heat exchanger 11 to cool the material to be distilled in the second heat release channel 12a of the second-stage heat exchanger 12. After liquefaction, the material to be distilled can flow back into the low-temperature distillation tower and undergo reverse gas-liquid exchange on the packing surface of the low-temperature distillation tower. In the continuous reverse gas-liquid exchange, the light and heavy components of the material to be distilled are separated.

[0051] It should be noted that the secondary heat exchanger 12 of the refrigeration system 10 in this embodiment can be one or more according to the requirements of the cryogenic distillation system. The "multiple" in this embodiment refers to two or more. Among them, one secondary heat exchanger 12 can correspond to one cryogenic distillation tower.

[0052] The primary heat exchanger 11 has a first heat release channel 11a and a first heat absorption channel 11b that are not interconnected. This allows the liquid nitrogen in the first heat absorption channel 11b to cool the gaseous methane in the first heat release channel 11a. Liquid nitrogen enters and nitrogen gas exits the inlet and outlet of the first heat absorption channel 11b; gaseous methane enters and liquid methane exits the inlet and outlet of the first heat release channel 11a.

[0053] It should be noted that the inlet of the first heat release channel 11a is used to introduce gaseous methane, which can be gaseous methane introduced from outside the refrigeration system 10, or gaseous methane provided by the secondary heat exchanger 12, or a combination of the two, which is not limited here.

[0054] It can be understood that under standard atmospheric pressure, the liquefaction temperature of gaseous methane is approximately -161.5°C, and the boiling point of liquid nitrogen is approximately -196°C. As the pressure increases, the liquefaction temperature of gaseous methane and the boiling point of liquid nitrogen also increase. In this way, the temperature of liquid nitrogen is sufficient to cool the gaseous methane and improve the efficiency of condensing gaseous methane into liquid methane.

[0055] Similarly, the secondary heat exchanger 12 includes a second heat-releasing channel 12a and a second heat-absorbing channel 12b, which are not interconnected. The liquid methane in the second heat-absorbing channel 12b cools the material to be distilled in the second heat-releasing channel 12a, causing the liquid methane introduced through the inlet of the second heat-absorbing channel 12b to absorb heat and vaporize into gaseous methane. The material to be distilled introduced through the inlet of the second heat-releasing channel 12a is typically gas located at the top of a cryogenic distillation column. The material to be distilled in the second heat-releasing channel 12a releases heat to condense into a liquid, which then returns to the cryogenic distillation column for continued reverse gas-liquid exchange, achieving separation of the light and heavy components.

[0056] The inlet of the second heat absorbing channel 12b is connected to the outlet of the first heat releasing channel 11a, and the outlet of the second heat absorbing channel 12b is connected to the inlet of the first heat releasing channel 11a. That is to say, a methane loop is formed between the second heat absorbing channel 12b and the first heat releasing channel 11a of the primary heat exchanger 11. The liquid methane entering the second heat absorbing channel 12b absorbs heat and vaporizes into gaseous methane, which is then discharged from the outlet of the second heat absorbing channel 12b. The gaseous methane formed after vaporization enters the first heat releasing channel 11a, and is then condensed into liquid methane in the first heat releasing channel 11a again, thereby circulating back and forth in the methane loop.

[0057] The refrigeration system 10 provided in an embodiment of the present application comprises a primary heat exchanger 11 and at least one secondary heat exchanger 12. Liquid nitrogen is used to condense gaseous methane into liquid methane in the primary heat exchanger 11. The inlet of the second heat absorption channel 12b of the secondary heat exchanger 12 is connected to the outlet of the first heat release channel 11a of the primary heat exchanger 11, thereby allowing the liquid methane condensed by the primary heat exchanger 11 to enter. The liquid methane in the second heat absorption channel 12b absorbs heat and vaporizes into gaseous methane, which is then returned to the primary heat exchanger 11 for cyclic condensation. The liquid methane liquefies the material to be distilled in the second heat release channel 12a of the secondary heat exchanger 12. For example, the material to be distilled is condensed into liquid and returned to the cryogenic distillation tower for further reverse gas-liquid exchange, thereby achieving separation of light and heavy components of the material to be distilled. A controller can improve the circulation reliability between the primary heat exchanger 11 and the secondary heat exchanger 12 by comprehensively regulating the parameters of the primary heat exchanger 11 and the secondary heat exchanger 12. The refrigeration system 10 uses methane and liquid nitrogen in combination, does not require additional refrigerant, does not require a compressor, and can meet the temperature zone requirements of cryogenic distillation, thereby reducing equipment costs and maintenance costs.

[0058] For some examples, see Figure 1The refrigeration system 10 includes a first regulating valve V1 and a first pressure sensor P1. The first pressure sensor P1 is located at the inlet of the first heat release channel 11a. The first regulating valve V1 is located at the inlet of the first heat absorption channel 11b. The first pressure sensor P1 is used to detect the pressure of the gaseous methane at the inlet of the first heat release channel 11a and transmit it to the controller. The controller can control the first regulating valve V1 to adjust the liquid nitrogen input rate based on the pressure signal from the first pressure sensor P1.

[0059] The first regulating valve V1 is arranged at the inlet of the first heat absorption channel 11b, and is used to control the speed of liquid nitrogen input into the first heat absorption channel 11b. It can be understood that the faster the input speed of liquid nitrogen, the higher the heat exchange efficiency between the liquid nitrogen in the first heat absorption channel 11b and the gaseous methane in the first heat release channel 11a in the primary heat exchanger 11, and the faster the gaseous methane at the inlet of the first heat release channel 11a enters the first heat release channel 11a and condenses into liquid methane, thereby effectively reducing the pressure of the gaseous methane at the inlet of the first heat release channel 11a.

[0060] Exemplarily, the first regulating valve V1 is a pneumatic regulating valve.

[0061] It should be noted that the first regulating valve V1 and the regulating valves described below can output signals to the analog output channel after being processed by the PID control program, and convert the current signal into a pressure signal through an electrical converter to adjust the opening, thereby controlling the flow rate and / or pressure of the circulating medium and increasing the stability of the process parameters of the refrigeration system 10 during the refrigeration process.

[0062] Exemplarily, a first temperature sensor T1 is further provided at the inlet of the first heat release channel 11 a , and the first temperature sensor T1 is used to detect the temperature of the gaseous methane at the inlet of the first heat release channel 11 a and transmit it to the controller to monitor the working status of the refrigeration system 10 .

[0063] In this embodiment, a first regulating valve V1 is provided at the inlet of the first heat absorption channel 11b of the primary heat exchanger 11, and a first pressure sensor P1 is provided at the inlet of the first heat release channel 11a of the primary heat exchanger 11. The controller only needs to control the first regulating valve V1 to adjust the input speed of liquid nitrogen according to the pressure signal fed back by the first pressure sensor P1, thereby controlling the heat exchange efficiency of the primary heat exchanger 11, and further controlling the pressure of the gaseous methane at the inlet of the first heat release channel 11a, thereby improving the reliability and convenience of controlling the primary heat exchanger 11.

[0064] For some examples, see Figure 1The refrigeration system 10 includes a second regulating valve V2 and a second pressure sensor P2. The second pressure sensor P2 and the second regulating valve V2 are located at the outlet of the first heat absorption channel 11b. The second pressure sensor P2 detects the pressure of the nitrogen at the outlet of the first heat absorption channel 11b and transmits the pressure to the controller. The controller controls the second regulating valve V2 to adjust the nitrogen exhaust rate based on the pressure signal from the second pressure sensor P2.

[0065] It can be understood that when the first regulating valve V1 provided at the inlet of the first heat absorption channel 11b of the primary heat exchanger 11 is adjusted to change the input speed of liquid nitrogen, the speed of the nitrogen at the outlet of the first heat absorption channel 11b of the primary heat exchanger 11 will also change accordingly. Therefore, a second pressure sensor P2 and a second regulating valve V2 are provided at the outlet of the first heat absorption channel 11b of the primary heat exchanger 11 to regulate the pressure of the nitrogen at the outlet of the first heat absorption channel 11b to be within an allowable range, which can improve the stability of the primary heat exchanger 11 and thereby improve the stability and reliability of the refrigeration system 10.

[0066] Exemplarily, a second temperature sensor T2 is also provided at the outlet of the first heat absorption channel 11b of the primary heat exchanger 11. The second temperature sensor T2 is used to detect the temperature of the nitrogen at the outlet of the first heat absorption channel 11b and transmit it to the controller to monitor the working status of the refrigeration system 10.

[0067] For some examples, see Figure 1 Refrigeration system 10 includes a first branch. The inlet of second heat absorption channel 12b is connected to the outlet of first heat release channel 11a via the first branch. Refrigeration system 10 includes a liquid tank 14 and a liquid pump 15. Both liquid tank 14 and liquid pump 15 are located in the first branch. Liquid tank 14 receives liquid methane flowing from the outlet of first heat release channel 11a. Liquid pump 15 pumps the liquid methane in liquid tank 14 to the inlet of second heat absorption channel 12b.

[0068] The inlet of the second heat absorption channel 12b is connected to the outlet of the first heat release channel 11a through the first branch. That is, after the liquid methane flows out from the outlet of the first heat release channel 11a, it flows through the first branch to the inlet of the second heat absorption channel 12b, thereby performing heat exchange in the secondary heat exchanger 12.

[0069] The liquid tank 14 is used to receive and store a certain amount of liquid methane, and supply it to one or more secondary heat exchangers 12 through the liquid pump 15. The liquid methane stored in the liquid tank 14 can be supplied to multiple secondary heat exchangers 12, and the total cooling capacity of the refrigeration system 10 can be adjusted according to demand, thereby improving the versatility of the refrigeration system 10 while also improving the stability of the refrigeration system 10.

[0070] Exemplarily, a third temperature sensor T3 is provided between the outlet of the first heat release channel 11a and the liquid tank 14. The third temperature sensor T3 is used to detect the temperature of the liquid methane that has just been condensed at the outlet of the first heat release channel 11a and transmit it to the controller to monitor the working status of the refrigeration system 10.

[0071] Exemplarily, a fourth temperature sensor T4 is provided between the liquid methane inlet of the liquid pump 15 and the liquid tank 14. The fourth temperature sensor T4 is used to detect the temperature of the liquid methane output from the liquid tank 14 to the inlet of the liquid pump 15 and transmit it to the controller to monitor the working status of the refrigeration system 10.

[0072] Exemplarily, the liquid pump 15 is a piston pump.

[0073] For example, the liquid pump 15 is equipped with an explosion-proof electrical cabinet, which enables local / remote startup and status indication of the liquid pump 15. The liquid pump 15 is hardwired to the PLC digital input and output module, enabling basic functions such as starting and stopping the liquid pump 15, status feedback, and fault alarms on the host computer's monitoring screen.

[0074] For some examples, see Figure 1 The refrigeration system 10 includes a liquid level sensor LS. The liquid level sensor LS is provided in the liquid tank 14. The liquid level sensor LS is used to detect the liquid level information of the liquid methane in the liquid tank 14 and transmit it to the controller. The controller is used to control the disconnection of the liquid tank 14 from the secondary heat exchanger 12 when the liquid level information of the liquid methane in the liquid tank 14 is lower than a first preset value; and to control the liquid tank 14 to deliver liquid methane to the secondary heat exchanger 12 when the liquid level information of the liquid methane in the liquid tank 14 is not less than the first preset value. The refrigeration system 10 is provided with a methane supply port 10a. The methane supply port 10a is used at least to replenish gaseous methane to the first heat release channel 11a when the liquid level information of the liquid methane in the liquid tank 14 is lower than the first preset value.

[0075] Controlling the disconnection of the liquid tank 14 from the secondary heat exchanger 12 and controlling the liquid tank 14 to deliver liquid methane to the secondary heat exchanger 12 can be achieved by controlling the start and stop of the liquid pump 15, or a valve can be set between the liquid tank 14 and the liquid pump 15, and the controller can achieve this by simultaneously controlling the start and stop of the valve and the liquid pump 15.

[0076] Exemplarily, the refrigeration system 10 is provided with an on-off valve at the methane supply port 10 a for controlling the opening and closing of the methane supply port 10 a.

[0077] The methane supply port 10a is at least used to replenish gaseous methane to the first heat release channel 11a when the liquid level information of the liquid methane in the liquid tank 14 is lower than the first preset value. In addition, the methane supply port 10a can also replenish gaseous methane to the first heat release channel 11a when the liquid level information of the liquid methane in the liquid tank 14 is higher than the first preset value. That is to say, from the start of the refrigeration system 10, the methane supply port 10a can always introduce gaseous methane, thereby ensuring that the methane circuit has sufficient methane for circulation.

[0078] In this embodiment, a liquid level sensor LS is provided in the liquid tank 14, and the controller controls the disconnection and connection between the liquid tank 14 and the secondary heat exchanger 12 according to the liquid level of the liquid tank 14, thereby controlling the operation of the secondary heat exchanger 12. The liquid level signal can ensure that the secondary heat exchanger 12 is supplied with sufficient liquid methane when it is working, thereby improving the working stability and reliability of the secondary heat exchanger 12.

[0079] For some examples, see Figure 1 The refrigeration system 10 includes a second branch for delivering gaseous methane vaporized under the pressure of the liquid pump 15 to the liquid tank 14 .

[0080] Specifically, the liquid pump 15 has three interfaces, one of which is the liquid methane input port, one is the liquid methane output port, and one is the gaseous methane output port. The second branch connects the gaseous methane output port of the liquid pump 15 with the liquid tank 14, thereby transporting the gaseous methane generated when the liquid pump 15 pumps liquid methane back to the liquid tank 14, improving the utilization rate of methane and reducing the methane loss in the methane circuit. At the same time, the methane transported to the secondary heat exchanger 12 is almost completely liquid methane, increasing the heat exchange reliability.

[0081] Exemplarily, the refrigeration system 10 further includes a communicating vessel branch, and the inlet of the first heat release channel 11a is connected to the top of the liquid tank 14 through the communicating vessel branch. The communicating vessel branch acts as a communicating vessel, so that the liquid methane condensed from the liquid nitrogen can naturally flow from the outlet of the first heat release channel 11a to the liquid tank 14, and the gaseous methane at the top of the liquid tank 14 can return to the inlet of the first heat release channel 11a through the communicating vessel branch and be cooled into liquid methane again by the primary heat exchanger 11.

[0082] Illustratively, a fifth temperature sensor T5 is further provided on the second branch, and the fifth temperature sensor T5 is used to detect the temperature of the gaseous methane at the gaseous methane output port of the liquid pump 15 and transmit the temperature to the controller to monitor the working status of the refrigeration system 10 .

[0083] For some examples, see Figure 1The refrigeration system 10 includes a gas concentration detector GD. The gas concentration detector GD is arranged outside the liquid tank 14 and is used to detect whether the gaseous methane in the liquid tank 14 is leaking.

[0084] For example, since gaseous methane is lighter than air, arranging the gas concentration detector GD above the liquid tank 14 can improve the accuracy of gaseous methane leakage detection.

[0085] Here, by providing a gas concentration detector GD for detecting methane outside the liquid tank 14 , the situation where the concentration of methane in the air is too high after the liquid tank 14 leaks can be improved, thereby improving the safety of the refrigeration system 10 .

[0086] For some examples, see Figure 1 Refrigeration system 10 includes a third pressure sensor P3 and a solenoid valve EV. The third pressure sensor P3 is located in liquid tank 14 and is used to detect the pressure of the gaseous methane in liquid tank 14 and transmit the pressure to the controller. The controller is configured to control solenoid valve EV to open when the pressure of the gaseous methane in liquid tank 14 exceeds a set value, thereby venting the gaseous methane in liquid tank 14 to the external environment.

[0087] It should be noted that the solenoid valve EV can also be opened and closed according to the pressure of the first pressure sensor P1.

[0088] For example, when the refrigeration system 10 is started up, the methane supply port 10a continues to replenish gaseous methane to the first heat release channel 11a when the liquid level information of the liquid methane in the liquid tank 14 is higher than the first preset value. Therefore, when the pressure of the gaseous methane at the inlet of the first heat release channel 11a of the primary heat exchanger 11 exceeds the set value, the solenoid valve EV can be controlled to open to relieve the pressure at the inlet of the first heat release channel 11a, thereby improving the safety of the refrigeration system 10.

[0089] In this way, by detecting the pressure of the gaseous methane in the liquid tank 14, when the pressure of the gaseous methane in the liquid tank 14 exceeds the set value, the solenoid valve EV is controlled to open to discharge the gaseous methane in the liquid tank 14 to the external environment, thereby improving the safety of the refrigeration system 10 and improving the methane leakage in the methane circuit.

[0090] For some examples, see Figure 1 The refrigeration system 10 includes a third branch, a fourth pressure sensor P4, and a third regulating valve V3. The outlet of the liquid pump 15 is connected to the liquid tank 14 via the third branch. The third regulating valve V3 and the fourth pressure sensor P4 are located on the third branch. The fourth pressure sensor P4 detects the pressure of the liquid methane at the outlet of the liquid pump 15 and transmits it to the controller. The controller controls the third regulating valve V3 to adjust the pressure at the outlet of the liquid pump 15 based on the pressure signal from the fourth pressure sensor P4.

[0091] The outlet of the liquid pump 15 is connected to the liquid tank 14 via the third branch, which means that the outlet of the liquid pump 15 for discharging liquid methane is connected to the liquid tank 14 via the third branch. The third branch is used to return excess liquid methane discharged by the liquid pump 15 to the liquid tank 14.

[0092] It should be noted that the third branch is used to regulate the pressure between the outlet of the liquid pump 15 discharging liquid methane and the inlet of the second heat absorption channel 12b of the secondary heat exchanger 12, that is, the fourth pressure sensor P4 is arranged at the outlet of the liquid pump 15 discharging liquid methane.

[0093] In this embodiment, when the pressure between the outlet of the liquid pump 15 discharging liquid methane and the inlet of the second heat absorption channel 12b of the secondary heat exchanger 12 exceeds a preset range, the controller appropriately adjusts the flow rate and speed of the fluid medium flowing through the third regulating valve V3, thereby changing the speed of the liquid methane flowing back to the liquid tank 14 through the third branch, and further adjusting the pressure between the liquid pump 15 and the inlet of the second heat absorption channel 12b, so that the pressure here is within a safe range, thereby improving the safety and reliability of the refrigeration system 10.

[0094] For some examples, see Figure 1 The refrigeration system 10 includes a flow sensor and a fourth regulating valve V4. These flow sensor and fourth regulating valve V4 are located at the inlet of the second heat absorption channel 12b. The flow sensor detects the flow rate of liquid methane at the inlet of the second heat absorption channel 12b and transmits the information to a controller. The controller controls the fourth regulating valve V4 based on the flow rate signal from the flow sensor to adjust the liquid methane delivery rate.

[0095] Here, by setting a flow sensor and a fourth regulating valve V4 at the inlet of the second heat absorption channel 12b of the secondary heat exchanger 12, the delivery rate of the liquid methane entering the inlet of the second heat absorption channel 12b can be adjusted by the fourth regulating valve V4 according to the actual heat exchange demand of the secondary heat exchanger 12, so that the refrigeration system 10 can more accurately control the heat exchange efficiency of the secondary heat exchanger 12, thereby improving the response speed and accuracy of the regulation of the refrigeration system 10.

[0096] For some examples, see Figure 1 The refrigeration system 10 includes a fifth pressure sensor P5 and a fifth regulating valve V5. The fifth pressure sensor P5 is located at the outlet of the second heat absorption channel 12b. The fifth pressure sensor P5 detects the pressure of the gaseous methane at the outlet of the second heat absorption channel 12b and transmits the pressure to a controller. The controller controls the fifth regulating valve V5 to adjust the output rate of the gaseous methane based on the pressure signal from the fifth pressure sensor P5.

[0097] It should be noted that the fifth regulating valve V5 is disposed between the outlet of the second heat absorption channel 12b and the inlet of the first heat release channel 11a, and the fifth pressure sensor P5 is disposed between the outlet of the second heat absorption channel 12b and the fifth regulating valve V5. This allows the pressure of the gaseous methane between the outlet of the second heat absorption channel 12b and the fifth regulating valve V5 to be controlled by adjusting the fifth regulating valve V5, thereby maintaining the pressure at the outlet of the second heat absorption channel 12b of the secondary heat exchanger 12 within a safe range and improving the safety and reliability of the refrigeration system 10. Furthermore, the pressure of the gaseous methane at the first pressure sensor P1 can be influenced by adjusting the fifth regulating valve V5, thereby adjusting the delivery rate of the gaseous methane from the secondary heat exchanger 12 to the primary heat exchanger 11.

[0098] For some examples, see Figure 2 At least one secondary heat exchanger 12 includes a first heat exchanger EX1, a second heat exchanger EX2, and a third heat exchanger EX3. The first branch circuit includes a first main circuit, a first branch circuit, a second branch circuit, and a third branch circuit. A liquid tank 14 and a liquid pump 15 are provided on the first main circuit. One end of the first branch circuit, the second branch circuit, and the third branch circuit are respectively connected to the first main circuit, and the other ends of the first branch circuit, the second branch circuit, and the third branch circuit are respectively connected to the first heat exchanger EX1, the second heat exchanger EX2, and the third heat exchanger EX3. The refrigeration system 10 also includes a fourth branch circuit, a fifth branch circuit, and a sixth branch circuit. The outlets of the second heat absorption channels 12b of the first heat exchanger EX1, the second heat exchanger EX2, and the third heat exchanger EX3 are connected to the inlet of the first heat release channel 11a via the fourth branch circuit, the fifth branch circuit, and the sixth branch circuit, respectively.

[0099] It is understandable that the aforementioned flow sensor and fourth regulating valve V4 , fifth pressure sensor P5 and fifth regulating valve V5 may be respectively provided at the inlet and outlet of the first heat exchanger EX1 , the second heat exchanger EX2 and the third heat exchanger EX3 .

[0100] Exemplarily, for ease of description, the first branch, the second branch and the third branch are each provided with a first flow sensor L1, a second flow sensor L2 and a third flow sensor L3, as well as a fourth regulating valve V4, a fifth regulating valve V5 and a sixth regulating valve V6, and the fourth branch, the fifth branch and the sixth branch are respectively provided with a fifth pressure sensor P5, a sixth pressure sensor P6 and a seventh pressure sensor P7, a sixth temperature sensor T6, a seventh temperature sensor T7 and an eighth temperature sensor T8, as well as a seventh regulating valve V7, an eighth regulating valve V8 and a ninth regulating valve V9.

[0101] In this embodiment, three secondary heat exchangers 12 are provided, wherein one secondary heat exchanger 12 corresponds to one cryogenic distillation tower, so that the refrigeration system 10 can be applied to cooling one, two or three cryogenic distillation towers at the same time, thereby increasing the application scenarios of the refrigeration system 10.

[0102] A second aspect of the present application provides a control method for a refrigeration system 10, which is applicable to the refrigeration system 10 provided in any embodiment of the present application. Figure 3 , control methods include:

[0103] S100: Acquire liquid level information of a liquid tank of a refrigeration system;

[0104] S200: Determine whether the liquid level information exceeds a first preset value. If so, control the liquid tank to deliver liquid methane to the secondary heat exchanger. If not, control the outlet of the liquid tank to be closed, and replenish gaseous methane to the first heat release channel through the methane supply port of the refrigeration system.

[0105] In step S100, the liquid level sensor LS provided in the liquid tank 14 is connected to the analog input channel of the PLC via the safety barrier, and data is processed by software programming and displayed on the host computer.

[0106] In step S200, in order to continuously deliver liquid methane to the secondary heat exchanger 12 and improve the stability of the refrigeration system 10, it is necessary to first determine whether the liquid methane storage amount in the liquid tank 14 collected by the liquid level sensor LS can continuously supply the secondary heat exchanger 12, that is, to determine whether the liquid level information exceeds a first preset value.

[0107] It should be noted that in step S200, when determining whether the liquid level exceeds the first preset value, a threshold value can be incorporated into the actual determination process for judgment and control. For example, during the actual determination and control process, if the liquid level in liquid tank 14 is greater than or equal to 25L, liquid tank 14 is controlled to deliver liquid methane to secondary heat exchanger 12. If the liquid level in liquid tank 14 is less than or equal to 20L, the outlet of liquid tank 14 is controlled to be closed, and gaseous methane is replenished to the first heat release channel 11a through the methane replenishment port 10a of the refrigeration system 10. This can alleviate the frequent on-off switching of the methane circuit, thereby improving the stability and reliability of the refrigeration system 10.

[0108] In addition, it can be understood that steps S100 and S200 can be preparatory steps for the refrigeration system 10 in the initial state before starting the methane circuit and refrigerating the low-temperature distillation tower. After the controller controls the liquid tank 14 to transport liquid methane to the secondary heat exchanger 12, the methane supply port 10a of the refrigeration system 10 still continues to replenish gaseous methane to the first heat release channel 11a, thereby ensuring that there is sufficient methane to circulate in the methane circuit and that there is sufficient liquid methane in the liquid tank 14 to supply the secondary heat exchanger 12, so that the secondary heat exchanger 12 can continue to refrigerate the low-temperature distillation tower.

[0109] For some examples, see Figure 4 After the control liquid tank 14 delivers liquid methane to the secondary heat exchanger 12, the control method further includes:

[0110] S300: collecting data signals from the liquid tank, primary heat exchanger, and secondary heat exchanger of the refrigeration system;

[0111] S400: Determine whether the data signal exceeds a preset range. If so, adjust the input rate of liquid nitrogen and / or the discharge rate of nitrogen and / or the output rate of liquid methane and / or the output rate of gaseous methane so that the data signal is within the preset range; wherein the data signal includes at least one of a pressure signal, a temperature signal, and a flow signal.

[0112] For example, in step S400, the pressure at the inlet of the first heat release channel 11a through which the gaseous methane is input into the first-stage heat exchanger 11 can be adjusted by adjusting the input speed of the liquid nitrogen. For example, by increasing the input speed of the liquid nitrogen, the heat exchange rate of the first-stage heat exchanger 11 is accelerated, thereby increasing the speed at which the gaseous methane is condensed into liquid methane, thereby reducing the pressure of the gaseous methane at the inlet of the first heat release channel 11a.

[0113] In this embodiment, data signals are collected at the liquid tank 14, the primary heat exchanger 11, and the secondary heat exchanger 12, and the controller program controls each regulating valve to adjust the input rate of liquid nitrogen, the discharge rate of nitrogen, the output rate of liquid methane, and the output rate of gaseous methane, so that each data signal is controlled within a preset range, thereby automatically adjusting the refrigeration system 10 and improving the stability and safety of the refrigeration system 10.

[0114] The various embodiments / implementations provided in this application can be combined with each other without causing any contradiction.

[0115] The foregoing description is merely a preferred embodiment of the present application and is not intended to limit the present application. Persons skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A refrigeration system, characterized in that: include: A primary heat exchanger, wherein the primary heat exchanger has a first heat release channel and a first heat absorption channel which are not connected to each other, the inlet of the first heat release channel is used to introduce gaseous methane, and the inlet of the first heat absorption channel is used to introduce liquid nitrogen, gaseous methane can exchange heat with liquid nitrogen in the primary heat exchanger, the outlet of the first heat release channel is used to output liquid methane, and the outlet of the first heat absorption channel is connected to the external environment, and is used to discharge nitrogen formed after the liquid nitrogen is vaporized to the external environment; At least one secondary heat exchanger, the secondary heat exchanger having a second heat release channel and a second heat absorption channel which are not connected to each other, the inlet of the second heat absorption channel being connected to the outlet of the first heat release channel for introducing liquid methane, the inlet of the second heat release channel being used for introducing a substance to be distilled, the liquid methane can exchange heat with the substance to be distilled in the secondary heat exchanger, the outlet of the second heat absorption channel being connected to the inlet of the first heat release channel for introducing gaseous methane formed after the liquid methane is vaporized into the first heat release channel, and the outlet of the second heat release channel being used for introducing the liquefied substance to be distilled into the distillation tower; A controller is used to control the operation of the refrigeration system.

2. The refrigeration system according to claim 1, characterized in that: The refrigeration system includes a first regulating valve and a first pressure sensor, wherein the first pressure sensor is disposed at the entrance of the first heat release channel, and the first regulating valve is disposed at the entrance of the first heat absorption channel, and the first pressure sensor is used to detect the pressure of the gaseous methane at the entrance of the first heat release channel and transmit it to the controller, and the controller can control the first regulating valve to adjust the input speed of the liquid nitrogen according to the pressure signal of the first pressure sensor; And / or, the refrigeration system includes a second regulating valve and a second pressure sensor, the second pressure sensor and the second regulating valve are arranged at the outlet of the first heat absorption channel, the second pressure sensor is used to detect the pressure of the nitrogen at the outlet of the first heat absorption channel and transmit it to the controller, and the controller can control the second regulating valve to adjust the exhaust speed of the nitrogen according to the pressure signal of the second pressure sensor.

3. The refrigeration system according to claim 1, characterized in that: The refrigeration system includes a first branch, and the inlet of the second heat absorption channel is connected to the outlet of the first heat release channel through the first branch. The refrigeration system includes a liquid tank and a liquid pump, and the liquid tank and the liquid pump are arranged on the first branch. The liquid tank is used to receive liquid methane flowing out of the outlet of the first heat release channel, and the liquid pump pumps the liquid methane in the liquid tank to the inlet of the second heat absorption channel.

4. The refrigeration system according to claim 3, characterized in that: The refrigeration system comprises a liquid level sensor, which is arranged in the liquid tank, and is used to detect the liquid level information of the liquid methane in the liquid tank and transmit it to the controller; The controller is used to control the disconnection of the liquid tank from the secondary heat exchanger when the liquid level information of the liquid methane in the liquid tank is lower than a first preset value; and to control the liquid tank to transport the liquid methane to the secondary heat exchanger when the liquid level information of the liquid methane in the liquid tank is not less than the first preset value; The refrigeration system is provided with a methane supply port, and the methane supply port is at least used to replenish gaseous methane to the first heat release channel when the liquid level information of the liquid methane in the liquid tank is lower than a first preset value.

5. The refrigeration system according to claim 3, characterized in that: The refrigeration system includes a second branch for conveying gaseous methane vaporized under the pressure of the liquid pump to the liquid tank.

6. The refrigeration system according to claim 5, characterized in that: The refrigeration system comprises a gas concentration detector, which is arranged outside the liquid tank and is used to detect whether the gaseous methane in the liquid tank is leaking; And / or, the refrigeration system includes a third pressure sensor and a solenoid valve, the third pressure sensor is arranged in the liquid tank, and is used to detect the pressure of the gaseous methane in the liquid tank and transmit it to the controller, and the controller is used to control the solenoid valve to open when the pressure of the gaseous methane in the liquid tank exceeds a set value, so as to discharge the gaseous methane in the liquid tank to the external environment; And / or, the refrigeration system includes a third branch, a fourth pressure sensor and a third regulating valve, the outlet of the liquid pump is connected to the liquid tank through the third branch, the third regulating valve and the fourth pressure sensor are arranged on the third branch, the fourth pressure sensor is used to detect the pressure of liquid methane at the outlet of the liquid pump and transmit it to the controller, and the controller is used to control the third regulating valve to adjust the pressure at the outlet of the liquid pump according to the pressure signal of the fourth pressure sensor.

7. The refrigeration system according to claim 1, characterized in that: The refrigeration system includes a flow sensor and a fourth regulating valve, the flow sensor and the fourth regulating valve are arranged at the inlet of the second heat absorption channel, the flow sensor is used to detect the flow of liquid methane at the inlet of the second heat absorption channel, and transmit it to the controller, the controller is used to control the fourth regulating valve to adjust the delivery speed of liquid methane according to the flow signal of the flow sensor; And / or, the refrigeration system includes a fifth pressure sensor and a fifth regulating valve, the fifth pressure sensor is arranged at the outlet of the second heat absorption channel, the fifth pressure sensor is used to detect the pressure of the gaseous methane at the outlet of the second heat absorption channel and transmit it to the controller, and the controller is used to control the fifth regulating valve to adjust the output speed of the gaseous methane according to the pressure signal of the fifth pressure sensor.

8. The refrigeration system according to claim 3, characterized in that: The at least one secondary heat exchanger includes a first heat exchanger, a second heat exchanger and a third heat exchanger, the first branch includes a first main road, a first branch road, a second branch road and a third branch road, the liquid tank and the liquid pump are arranged on the first main road, one end of the first branch road, the second branch road and the third branch road are respectively used to connect to the first main road, and the other ends of the first branch road, the second branch road and the third branch road are respectively used to connect to the first heat exchanger, the second heat exchanger and the third heat exchanger; The refrigeration system also includes a fourth branch, a fifth branch and a sixth branch, and the outlets of the second heat absorption channels of the first heat exchanger, the second heat exchanger and the third heat exchanger are connected to the inlet of the first heat release channel through the fourth branch, the fifth branch and the sixth branch respectively.

9. A control method for a refrigeration system, applied to the refrigeration system according to any one of claims 1 to 8, characterized in that: The control method comprises: Acquiring liquid level information of a liquid tank of the refrigeration system; Determine whether the liquid level information exceeds a first preset value. If so, control the liquid tank to deliver liquid methane to the secondary heat exchanger. If not, control the outlet of the liquid tank to close, and control the methane supply port of the refrigeration system to replenish gaseous methane to the first heat release channel.

10. The control method according to claim 9, characterized in that: After controlling the liquid tank to deliver liquid methane to the secondary heat exchanger, the control method further includes: Collecting data signals from the liquid tank, the primary heat exchanger, and the secondary heat exchanger of the refrigeration system; Determine whether the data signal exceeds a preset range. If so, adjust the input speed of liquid nitrogen and / or the discharge speed of nitrogen and / or the output speed of liquid methane and / or the output speed of gaseous methane to make the data signal within the preset range; wherein the data signal includes at least one of a pressure signal, a temperature signal, and a flow signal.

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