A low-temperature liquid tank truck unloading device, unloading system and control method

Abstract

The present invention discloses an unloading device, unloading system and control method for a low-temperature liquid tank truck. The unloading device includes a compressor, a regenerator, a cooling device, a control valve group, and also includes a low-temperature liquid storage tank interface and a tank truck interface. The control valve group selects to connect the storage tank interface with the second heat exchange outlet and / or the first heat exchange inlet of the regenerator, and connects the tank truck interface with the first heat exchange inlet and / or the second heat exchange outlet. The device, system and control method of the present invention are simple to operate, can efficiently realize normal temperature pressurized unloading, and are suitable for existing gas filling stations.

Description

Technical Field

[0001] The present invention relates to the field of cryogenic liquid transportation, and in particular to an unloading device, an unloading system and a control method for a cryogenic liquid tank truck. Background Art

[0002] How to avoid incomplete unloading and reduce gas emission in the unloading of cryogenic liquid tank trucks is a technical problem that needs to be generally solved. Unloading by normal temperature boosting system with compressor extraction pressure is a new type of unloading method. The applicant has filed a patent application for this technology with application number 201810322454.9. This unloading method can boost pressure at room temperature to realize the unloading of cryogenic liquid tank trucks. However, in this technology, normal temperature boosting transportation and low temperature gas recovery are realized by switching the four-way reversing valve connected between the regenerator and the compressor. Since the four-way reversing valve itself has poor stability in low temperature environment and is inconvenient to operate, in order to improve the valve control stability and ensure the normal inlet temperature of the compressor, the system needs to set an air-temperature heat exchanger before the four-way reversing valve. And in order to ensure the normal operation of the two processes of normal temperature boosting transportation and low temperature gas recovery, two are generally required. Adding two heat exchangers to the unloading device will increase the cost of the device and make the overall volume larger. In addition, in order to realize the unloading of cryogenic liquids and the recovery of cryogenic gases, the existing normal temperature boosting system does not match the hoses and connection methods commonly used in gas stations. When implementing the system, professionals are required to configure hoses and control valves. The control process is complicated and often causes system failures due to misoperation. In particular, when performing the equalization operation between the tank truck and the storage tank, after configuring the external hoses and valves of the unloading device, it is necessary to rely on the valve control outside the unloading device, making it difficult to promote the unloading device as an independent product. Summary of the invention

[0003] In order to overcome at least one of the defects of the prior art described above, the present invention provides an unloading device, an unloading system and a control method for a cryogenic liquid tank truck.

[0004] The technical solution adopted by the present invention to solve the problem is:

[0005] A low-temperature liquid tank truck unloading device, comprising: a compressor, a regenerator, a cooling device, a control valve group, a storage tank interface and a tank truck interface; the regenerator comprises a first heat exchange side and a second heat exchange side, the first heat exchange side has a first heat exchange inlet and a first heat exchange outlet, the second heat exchange side has a second heat exchange inlet and a second heat exchange outlet; the control valve group is used to select the storage tank interface to be connected to the second heat exchange outlet and / or the first heat exchange inlet, and select the tank truck interface to be connected to the first heat exchange inlet and / or the second heat exchange outlet;

[0006] The first heat exchange outlet is connected to the compressor inlet, and the cooling device is connected between the compressor outlet and the second heat exchange inlet.

[0007] Preferably, the control valve group includes a first control valve, a second control valve, a third control valve, and a fourth control valve. The low-temperature liquid storage tank interface is connected to one end of the first control valve and the second control valve, respectively, and the tank truck interface is connected to one end of the third control valve and the fourth control valve, respectively. The other end of the first control valve and the fourth control valve is connected to the first heat exchange inlet, and the other end of the second control valve and the third control valve is connected to the second heat exchange outlet.

[0008] Preferably, it also includes an oil-gas separator, which is connected between the compressor and the cooling device and has an oil outlet connected to the compressor.

[0009] The present invention also provides an unloading system, comprising the above-mentioned unloading device, and also comprising a tank truck and a low-temperature liquid storage tank; the tank truck has a tank truck gas phase port and a tank truck liquid phase port, the low-temperature liquid storage tank has a tank first gas phase port and a tank liquid phase port, the tank truck gas phase port is connected to the tank truck interface, the tank truck liquid phase port is connected to the tank liquid phase port, and the tank first gas phase port is connected to the tank interface.

[0010] Preferably, a bypass pipeline is connected between the first gas phase port of the storage tank and the liquid phase port of the storage tank, and a bypass valve is provided on the bypass pipeline.

[0011] Preferably, a first liquid inlet valve is provided on the pipeline connecting the liquid phase port of the tank truck and the liquid phase port of the storage tank, and a gas outlet valve is connected between the first gas phase port of the storage tank and the storage tank interface.

[0012] Preferably, the storage tank also has a second gas phase port of the storage tank, and the first liquid inlet valve is divided into two paths at one end away from the liquid phase port of the tank truck, one path is connected to the liquid phase port of the storage tank through the second liquid inlet valve, and the other path is connected to the second gas phase port of the storage tank through the third liquid inlet valve.

[0013] The present invention also provides a control method for a low-temperature liquid tank truck unloading system, wherein the control valve group selects to connect the storage tank interface with the first heat exchange inlet, selects to connect the tank truck interface with the second heat exchange outlet, operates the compressor, and controls the low-temperature liquid in the tank truck to enter the storage tank; after unloading is completed, the control valve selects to connect the storage tank interface with the second heat exchange outlet, selects to connect the tank truck interface with the first heat exchange inlet, controls the low-temperature gas in the tank truck to enter the tank truck interface, and enters the liquid phase port of the tank truck from the storage tank interface; after the gas pressure in the tank truck drops to a predetermined value, the compressor is turned off.

[0014] Preferably, when the gas pressure in the storage tank is higher than the gas pressure in the tank truck, the control valve group selects to connect the storage tank interface with both the second heat exchange outlet and the first heat exchange inlet, and selects to connect the tank truck interface with both the first heat exchange inlet and the second heat exchange outlet.

[0015] Preferably, the storage tank also has a second gas phase port of the storage tank; during the unloading process, when the gas pressure in the storage tank is higher than a preset value, the low-temperature liquid flowing out of the liquid phase port of the tank truck is controlled to enter the second gas phase port of the storage tank.

[0016] The unloading device provided by the present invention does not need to be provided with an air-temperature heat exchanger, saves the four-way reversing valve, and sets the valve assembly before the heat regenerator. The valve assembly does not need to be set through the internal pipeline of the unloading device, so that the performance is more stable and the structure is simple. The external interface of the unloading device is a storage tank interface and a tank truck interface, and a control valve group is set. When in use, the storage tank interface and the tank truck interface are simply connected to the hose flanges of the existing gas station storage tank and tank truck respectively. It is plug-and-play with the existing gas station equipment. The unloading system of the present invention provided on this basis can realize the unloading of low-temperature gas efficiently and recover the low-temperature gas in the tank truck by operating the control valve group, and the emission of low-temperature gas is reduced, the unloading is clean, and it is energy-saving and environmentally friendly. The control method provided by the present invention is simple to operate and can be operated and used by ordinary technicians. It has comprehensive functions and can achieve the purposes of unloading, leveling pressure, reducing storage tank pressure, and recovering low-temperature gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of an unloading device for a cryogenic liquid tank truck according to an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of an unloading system for a cryogenic liquid tank truck according to an embodiment of the present invention;

[0019] Figure 3 This is a working state diagram of a low-temperature liquid tank truck unloading system according to an embodiment of the present invention;

[0020] Figure 4 Another working state diagram of the low-temperature liquid tank truck unloading system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] For better understanding and implementation, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0023] See also Figure 1 , a schematic diagram of an unloading device 100 for a cryogenic liquid tank truck. In this embodiment, the cryogenic liquid is specifically liquefied natural gas (LNG). In other embodiments, it can also be used to unload other liquids with similar cryogenic characteristics, such as liquid oxygen, liquid nitrogen, etc., which are not limited here. The unloading device 100 includes a compressor 1, a regenerator 5, a cooling device 6, and a control valve group 101. The unloading device 100 also includes a cryogenic liquid storage tank interface 11 and a tank truck interface 12, which are provided on the packaging shell of the unloading device 100 as external interfaces. The cryogenic liquid storage tank interface 11 is used to connect the cryogenic liquid storage tank when unloading, and the tank truck interface 12 is used to connect the tank truck for transporting the cryogenic liquid when unloading.

[0024] The regenerator 5 includes a first heat exchange side and a second heat exchange side, and the first heat exchange side and the second heat exchange side exchange heat with each other efficiently. In this embodiment, the regenerator 5 is a shell and tube heat exchanger. The first heat exchange side is a tube-side heat exchange channel, and the second heat exchange side is a shell-side heat exchange channel. In other embodiments, the regenerator 5 is a plate-fin heat exchanger. Figure 1 As shown, the first heat exchange side has a first heat exchange inlet b and a first heat exchange outlet c, and the second heat exchange side has a second heat exchange inlet d and a second heat exchange outlet a. The first heat exchange inlet b and the first heat exchange outlet c are respectively located at the two ends of the regenerator 5, and the second heat exchange outlet a and the second heat exchange inlet d are respectively located at the upper and lower ends of the regenerator 5.

[0025] The first heat exchange outlet c is connected to the inlet of the compressor 1, the outlet of the compressor 1 is connected to one port of the cooling device 6, and the other port of the cooling device 6 is connected to the second heat exchange inlet d, that is, the cooling device 6 is connected between the outlet of the compressor 1 and the second heat exchange inlet d.

[0026] In this embodiment, the cooling device 6 is an air cooler having a cooling coil. The cooling device 6 also includes a cooling fan 61, which accelerates the air flow around the cooling coil of the cooling device 6 to improve the cooling efficiency.

[0027] The control valve group 101 is used to select the connection between the storage tank interface 11 and the second heat exchange outlet a and / or the first heat exchange inlet b, and the connection between the tank car interface 12 and the first heat exchange inlet b and / or the second heat exchange outlet a. The "and / or" mentioned in the technical solution of the present invention here means that the control valve group 11 can connect the storage tank interface 11 with the second heat exchange outlet a and the first heat exchange inlet b at the same time, and can also choose to connect the storage tank interface 11 with any one of the second heat exchange outlet a and the first heat exchange inlet b; the control valve group 11 can connect the tank car interface 12 with the first heat exchange inlet b and the second heat exchange outlet a at the same time, and can also choose to connect the storage tank interface 12 with any one of the first heat exchange inlet b and the second heat exchange outlet a. The "and / or" here does not mean a parallel technical solution, but means that the control valve group 11 has these parallel functions.

[0028] In this embodiment, the structure of the control valve group 101 is as follows: Figure 1 As shown, it includes a first control valve 7, a second control valve 8, a third control valve 9, and a fourth control valve 10. Among them, the cryogenic liquid storage tank interface 11 is connected to one end of the first control valve 7 and the second control valve 8 respectively, and the tank car interface 12 is connected to one end of the third control valve 9 and the fourth control valve 10 respectively. The other end of the first control valve 7 and the fourth control valve 10 is connected to the first heat exchange inlet b, and the other end of the second control valve 8 and the third control valve 9 is connected to the second heat exchange outlet a. In this embodiment, the first control valve 7, the second control valve 8, the third control valve 9, and the fourth control valve 10 are stop valves. In other embodiments, other valve control structures that can realize the functions of the control valve group 101 of the present invention can also be used, which are also within the protection scope of the present invention. The four-control valve setting structure of the present invention makes the operation simple and the performance reliable when used in the unloading device, and can achieve technical effects different from other embodiments.

[0029] In this embodiment, the unloading device 100 also includes an oil-gas separator 2, and the oil-gas separator 2 is connected between the compressor 1 and the cooling device 6. Specifically, the inlet of the oil-gas separator 2 is connected to the outlet of the compressor 1, and the air outlet of the oil-gas separator 2 is connected to the cooling coil of the cooling device 6 through the safety valve 4. In addition, the oil-gas separator 2 also has an oil outlet connected to the compressor 1 to provide return oil for the compressor. An oil return control valve 3 is provided on the connecting pipeline between the oil outlet and the oil return port of the compressor 1. Since the viscosity of the oil is too high at low temperatures, the efficiency of oil-gas separation will be reduced. The oil-gas separator is arranged before the cooling device, between the compressor and the cooling device, to ensure the normal operation of the oil-gas separator. This is also a major improvement of the present invention.

[0030] This embodiment also provides a low-temperature liquid tank truck unloading system, which includes an unloading device 100 , a tank truck 13 and a low-temperature liquid storage tank 14 .

[0031] like Figure 2 As shown, the tank truck 13 has a tank truck gas phase port 132 and a tank truck liquid phase port 131. The cryogenic liquid storage tank 14 has a tank first gas phase port 142 and a tank liquid phase port 141. The tank first gas phase port 142 is arranged at the upper end or top of the cryogenic liquid storage tank 14, and the tank liquid phase port 141 is arranged at the lower end or bottom of the cryogenic liquid storage tank 14. The tank truck gas phase port 132 is connected to the tank truck interface 12 of the unloading device 100, the tank truck liquid phase port 131 is connected to the tank liquid phase port 141, and the tank first gas phase port 142 is connected to the tank interface 11.

[0032] In a preferred embodiment, a bypass pipeline is connected between the liquid phase port 141 of the storage tank and the first gas phase port 142 of the storage tank, and a bypass valve 16 is provided on the bypass pipeline.

[0033] In a preferred embodiment, a first liquid inlet valve 15 is provided on the pipeline connecting the liquid phase port 131 of the tank truck and the liquid phase port 141 of the storage tank. Figure 3 As shown. In this embodiment, an outlet valve 20 is provided on the pipeline connecting the first gas phase port 142 of the storage tank and the storage tank interface 11 of the unloading device 100. The end of the outlet valve 20 away from the first gas phase port 142 of the storage tank is connected to the above-mentioned bypass pipeline. In this embodiment, the storage tank 14 also has a second gas phase port 143 of the storage tank. The first gas phase port 142 of the storage tank and the second gas phase port 143 of the storage tank are both located at the upper end or top of the storage tank 14. Correspondingly, the liquid phase port 141 of the storage tank is located at the lower end or bottom of the storage tank 14.

[0034] The first liquid inlet valve 15 is connected to the storage tank 14 at one end away from the liquid phase port 131 of the tanker in two ways. One pipeline is connected to the liquid phase port 141 of the storage tank 14, and the second liquid inlet valve 17 is arranged on the pipeline. The other pipeline is connected to the second gas phase port 142 of the storage tank 14, and the third liquid inlet valve 21 is arranged on the pipeline. The pipeline of the two pipelines is connected to the liquid phase port 131 of the tanker. The first liquid inlet valve 15 is arranged on the pipeline. The first liquid inlet valve 15 is also connected to the bypass pipeline at one end away from the liquid phase port 131 of the tanker in one end.

[0035] Using the cryogenic liquid tank truck unloading system as described above, the specific control method is as follows:

[0036] like Figure 3 In the unloading process shown, the control valve group 101 selects to connect the storage tank interface 11 with the first heat exchange inlet, selects to connect the tank truck interface with the second heat exchange outlet, runs the compressor, and controls the low-temperature liquid in the tank truck to enter the storage tank.

[0037] Specifically, open the first control valve 7 and the third control valve 9, close the second control valve 8 and the fourth control valve 10, open the first liquid inlet valve 15, the second liquid inlet valve 17, and the gas outlet valve 20, and close the other valves. The liquid phase port 141 of the cryogenic liquid storage tank 14 is connected to the liquid phase port 131 of the tank truck 13, the gas phase port 132 of the tank truck 13 is connected to the second heat exchange outlet a of the regenerator 5, and the first gas phase port 142 of the cryogenic gas storage tank 14 is connected to the tank interface 11. When the compressor 1 is running, the low-temperature gas in the storage tank 14 is pumped to the first heat exchange side of the regenerator 5 to increase the temperature. After the unloading preparation is completed, as the compressor 1 is running, the low-temperature gas in the cryogenic liquid storage tank 14 is pumped to the first heat exchange side of the regenerator 5 through the gas outlet valve 20, the tank interface 11, and the first control valve 7 in sequence to increase the temperature.

[0038] The low-temperature gas is heated on the first heat exchange side of the regenerator 5 and enters the compressor 1 for pressurization. After that, the gas enters the cooling device 6 through the one-way valve 4 for cooling, thereby forming normal temperature pressurized transportation.

[0039] After the compressed and cooled gas is cooled again on the second heat exchange side of the regenerator 5, it is connected to the gas phase interface 132 of the tank truck 13 from the second heat exchange outlet a through the third control valve 9 and the tank truck interface 12 to form gas cooling and pressure delivery. The internal gas environment of the tank truck 13 is pressurized to establish a pressure difference between the tank truck 13 and the storage tank 14. As the pressure increases, the cryogenic liquid such as LNG in the tank truck 13 enters the cryogenic liquid storage tank 4 from the liquid phase port 131 of the tank truck through the first liquid inlet valve 15 to be unloaded. In this step, by choosing to open the second liquid inlet valve 17, the cryogenic liquid in the tank truck 13 enters the storage tank 14 from the liquid phase port 141 of the storage tank. You can also choose to open the third liquid inlet valve 21, and the cryogenic liquid in the tank truck 13 enters the storage tank 14 from the second gas phase port 143 of the storage tank.

[0040] In the control method of the preferred embodiment, when the BOG pressure inside the storage tank 14 is too high, that is, higher than a preset value, the low-temperature liquid flowing out of the liquid phase port 131 of the tank truck is controlled to enter the second gas phase port 143 of the storage tank. The second liquid inlet valve 17 is controlled to be closed, and the third liquid inlet valve 21 is opened, so that the low-temperature liquid in the tank truck 13 enters the storage tank 14 from the second gas phase port 143 of the storage tank, and the low-temperature liquid entering the storage tank 14 from the second gas phase port 143 of the storage tank cools the BOG inside the storage tank 14 to liquefy, thereby reducing the BOG pressure inside the storage tank 14. This control step can more intelligently control the state of the unloading system and improve the system stability.

[0041] The unloading step utilizes the compressor 1 at room temperature to extract the low-temperature gas in the compressed storage tank 14, thereby establishing a pressure difference between the low-temperature liquid tank truck 13 and the storage tank 14. The pressure difference is utilized to move the low-temperature liquid from the tank truck 13 to the storage tank 14, thereby achieving rapid unloading.

[0042] In a preferred embodiment, in the unloading step, before the cryogenic gas in the cryogenic liquid storage tank 4 enters the regenerator 5, the pressure between the cryogenic liquid storage tank 14 and the tank truck 13 can be equalized by the control valve group 101. Specifically, if the pressure in the cryogenic liquid storage tank 14 is higher than the pressure in the tank truck 13, the first control valve 7, the second control valve 8, the third control valve 9, and the fourth control valve 10 are opened, and the gas in the cryogenic liquid storage tank 13 flows to the cryogenic liquid tank truck 14. When the pressure in the cryogenic liquid storage tank 14 is nearly equal to the pressure in the tank truck 13, the control valve group 101 is closed.

[0043] In the control mode of this embodiment, after unloading is completed, the control valve 101 selects to connect the storage tank interface 11 with the second heat exchange outlet a, selects to connect the tank car interface 12 with the first heat exchange inlet b, controls the low-temperature gas in the tank car to enter the tank car interface 12, and enters the tank car liquid phase port 141 from the storage tank interface. Specifically, Figure 4As shown. After unloading is completed, open the second control valve 8, the fourth control valve 10, the bypass valve 16, and the second liquid inlet valve 17, and close other valves. After unloading is completed, the low-temperature gas remaining in the tank truck 13 enters the first heat exchange side of the regenerator 5 through the first heat exchange inlet b of the regenerator 5 for heat exchange and temperature increase, enters the compressor 1 from the first heat exchange outlet c for pressurization, and then passes through the cooling device 6 and the second heat exchange side of the regenerator 5 for cooling, and then enters the low-temperature liquid storage tank 14 from the second heat exchange outlet a, through the second control valve 8, the bypass valve 16, the second liquid inlet valve 17, and from the liquid phase port 141 of the storage tank. Since the low-temperature gas enters the storage tank 14 from the liquid phase port 141 of the storage tank, the low-temperature gas will be liquefied.

[0044] When the low-temperature gas in the tank truck 13 is recovered and the pressure in the tank truck 13 is reduced to a predetermined value (generally 0.1 MPa), the compressor 1 is turned off to complete the low-temperature gas recovery step.

[0045] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical schemes composed of any combination of the above-mentioned technical features. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.

Claims

1. A low-temperature liquid tank truck unloading device (100), characterized in that: include: A compressor (1), a regenerator (5), a cooling device (6), a control valve group (101), a storage tank interface (11) and a tank truck interface (12); The regenerator (5) comprises a first heat exchange side and a second heat exchange side, the first heat exchange side having a first heat exchange inlet (b) and a first heat exchange outlet (c), and the second heat exchange side having a second heat exchange inlet (d) and a second heat exchange outlet (a); The control valve group (101) is used to select the connection between the storage tank interface (11) and the second heat exchange outlet (a) and / or the first heat exchange inlet (b), and to select the connection between the tank truck interface (12) and the first heat exchange inlet (b) and / or the second heat exchange outlet (a); The first heat exchange outlet (c) is connected to the compressor (1) inlet, and the cooling device (6) is connected between the compressor (1) outlet and the second heat exchange inlet (d); The control valve group (101) comprises a first control valve (7), a second control valve (8), a third control valve (9), and a fourth control valve (10); the storage tank interface (11) is connected to one end of the first control valve (7) and the second control valve (8), respectively; the tank car interface (12) is connected to one end of the third control valve (9) and the fourth control valve (10), respectively; the other ends of the first control valve (7) and the fourth control valve (10) are connected to the first heat exchange inlet (b); and the other ends of the second control valve (8) and the third control valve (9) are connected to the second heat exchange outlet (a); It also includes an oil-gas separator (2), which is connected between the compressor (1) and the cooling device (6) and has an oil outlet connected to the compressor (1).

2. A cryogenic liquid tank truck unloading system, characterized in that: It comprises the unloading device (100) as claimed in claim 1, and also comprises a tank truck (13) and a cryogenic liquid storage tank (14); the tank truck (13) has a tank truck gas phase port (132) and a tank truck liquid phase port (131), the cryogenic liquid storage tank (14) has a tank first gas phase port (142) and a tank liquid phase port (141), the tank truck gas phase port (132) is connected to the tank truck interface (12), the tank truck liquid phase port (131) is connected to the tank liquid phase port (141), and the tank first gas phase port (142) is connected to the tank interface (11).

3. The cryogenic liquid tank truck unloading system according to claim 2, characterized in that: A bypass pipeline is connected between the first gas phase port (142) of the storage tank and the liquid phase port (141) of the storage tank, and a bypass valve (16) is provided on the bypass pipeline.

4. The cryogenic liquid tank truck unloading system according to claim 3, characterized in that: A first liquid inlet valve (15) is provided on the pipeline connecting the tank truck liquid phase port (131) and the storage tank liquid phase port (141), and a gas outlet valve (20) is connected between the storage tank first gas phase port (142) and the storage tank interface (11).

5. The cryogenic liquid tank truck unloading system according to claim 4, characterized in that: The cryogenic liquid storage tank (14) further comprises a second gas phase port (143) of the storage tank, and the first liquid inlet valve (15) is divided into two paths at one end away from the liquid phase port (131) of the tank truck, one path being connected to the liquid phase port (141) of the storage tank via the second liquid inlet valve (17), and the other path being connected to the second gas phase port (143) of the storage tank via the third liquid inlet valve (21).

6. A control method for a cryogenic liquid tank truck unloading system as claimed in any one of claims 2 to 5, characterized in that: The control valve group (101) selects to connect the storage tank interface (11) with the first heat exchange inlet (b), selects to connect the tank truck interface (12) with the second heat exchange outlet (a), operates the compressor (1), and controls the cryogenic liquid in the tank truck to enter the cryogenic liquid storage tank (14); After unloading is completed, the control valve group (101) selects to connect the storage tank interface (11) with the second heat exchange outlet (a), and selects to connect the tank truck interface (12) with the first heat exchange inlet (b), so as to control the low-temperature gas in the tank truck to enter the tank truck interface (12), and enter the storage tank liquid phase port (141) from the storage tank interface; After the gas pressure in the tank truck (13) drops to a predetermined value, the compressor (1) is turned off.

7. The control method of the low-temperature liquid tank truck unloading system according to claim 6, characterized in that: When the gas pressure in the cryogenic liquid storage tank (14) is higher than the gas pressure in the tank truck (13), the control valve group (101) selects to connect the storage tank interface (11) with both the second heat exchange outlet (a) and the first heat exchange inlet (b), and selects to connect the tank truck interface (12) with both the first heat exchange inlet (b) and the second heat exchange outlet (a).

8. The control method of the low-temperature liquid tank truck unloading system according to claim 6, characterized in that: The cryogenic liquid storage tank also has a second gas phase port (143) of the storage tank; During the unloading process, when the gas pressure in the cryogenic liquid storage tank (14) is higher than a preset value, the cryogenic liquid flowing out of the liquid phase port (131) of the tank truck is controlled to enter the second gas phase port (143) of the storage tank.

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