LNG fuel cabin and tail gas recovery system thereof

Abstract

The utility model discloses an LNG fuel cabin and a tail gas recovery system thereof. The tail gas recovery system comprises a condensation mechanism, a nitrogen supply mechanism, a miscellaneous gas recovery mechanism, a tail gas emission mechanism and a natural gas storage mechanism, the output end of the liquid nitrogen supply device and the output end of the nitrogen supply device are respectively communicated with the nitrogen supply pipe; the number of the condensers is multiple. The nitrogen supply pipe passes through the interiors of the plurality of condensers and then passes through the nitrogen residual cold recovery device; the miscellaneous gas input pipe passes through the nitrogen residual cold recovery device, and the output end of the miscellaneous gas input pipe is communicated with the input ends of the plurality of condensers respectively; the output end of the miscellaneous gas output pipe is communicated with a tail gas emission mechanism; and the input end of the natural gas storage mechanism is communicated with the lower output end of the condenser. According to the scheme, nitrogen at different positions is fully utilized to recycle the to-be-recycled components, the method that direct combustion treatment is adopted to maintain the low pressure of the fuel cabin can be replaced, and the problem that waste is caused due to the fact that natural gas injected through an existing differential pressure method is mainly subjected to combustion treatment is solved.

Description

Technical Field

[0001] This utility model relates to the field of exhaust gas recovery, and in particular to an LNG fuel tank and its exhaust gas recovery system. Background Technology

[0002] LNG fuel tanks are refueled using a differential pressure method. LNG entering the tank will naturally evaporate, causing an increase in pressure that hinders refueling. Therefore, during refueling, the amount of gaseous natural gas needs to be continuously reduced to maintain a low pressure in the fuel tank. Currently, the primary method for pressurizing fuel tanks is direct combustion, but this method is too wasteful; because a 2000m³... 3 The initial refueling of the fuel tank may release 20 to 40 tons of natural gas, depending on the refueling process. While the existing technology for refueling natural gas using the differential pressure method is convenient, it is also costly and not conducive to sustainable development. Utility Model Content

[0003] The purpose of this invention is to propose an LNG fuel tank exhaust gas recovery system that first uses a nitrogen supply mechanism to deliver nitrogen to a condenser and a nitrogen residual cooling recovery device, and then uses a miscellaneous gas input pipe to first pass through the nitrogen residual cooling recovery device before being sent into the condenser, thus making full use of nitrogen at different locations to recover the components to be recovered.

[0004] This utility model also proposes an LNG fuel tank that uses the exhaust gas recovery system of the aforementioned LNG fuel tank.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] An LNG fuel tank exhaust gas recovery system includes: a condensation mechanism, a nitrogen supply mechanism, a miscellaneous gas recovery mechanism, an exhaust gas emission mechanism, and a natural gas storage mechanism;

[0007] The condensation mechanism includes: a condenser;

[0008] The nitrogen supply mechanism includes: a liquid nitrogen supply device, a nitrogen gas supply device, a nitrogen residual cooling recovery device, and a nitrogen supply pipe;

[0009] The output ends of the liquid nitrogen supply device and the nitrogen gas supply device are respectively connected to the nitrogen supply pipe; there are multiple condensers; the nitrogen supply pipe passes through the interior of multiple condensers and then through the nitrogen waste heat recovery device;

[0010] The impurity gas recovery mechanism includes: an impurity gas inlet pipe and an impurity gas outlet pipe;

[0011] The impurity gas input pipe passes through the nitrogen residual cooling recovery device, and the output end of the impurity gas input pipe is connected to the input end of the plurality of condensers respectively; the output end of the impurity gas output pipe is connected to the exhaust gas emission mechanism.

[0012] The input end of the natural gas storage device is connected to the output end of the condenser below.

[0013] Optimally, it may also include: a PLC module;

[0014] The PLC module is communicatively connected to the impurity gas recovery mechanism and the nitrogen supply mechanism;

[0015] The impurity gas recovery mechanism also includes: an intake gas composition detection device and an intake parameter detection device;

[0016] The intake gas composition detection device and the intake parameter detection device are respectively installed on the impurity gas input pipe and located between the input end of the impurity gas input pipe and the nitrogen residual cooling recovery device.

[0017] Optimally, the intake parameter detection device includes: an intake flow detection device, an intake temperature detection device, and an intake pressure detection device;

[0018] The intake flow detection device, intake temperature detection device, and intake pressure detection device are respectively installed on the impurity gas input pipe and located between the input end of the impurity gas input pipe and the nitrogen residual cooling recovery device.

[0019] Optimally, the exhaust emission mechanism includes: an exhaust pipe and an exhaust gas detection device;

[0020] The exhaust gas detection device includes: an exhaust gas composition detection device, an exhaust gas flow detection device, an exhaust gas temperature detection device, and an exhaust gas pressure detection device.

[0021] The input end of the exhaust pipe is connected to the output end of the miscellaneous gas output pipe; the exhaust gas flow detection device, the exhaust gas temperature detection device, and the exhaust gas pressure detection device are respectively installed on the exhaust pipe; the exhaust gas detection device is communicatively connected to the PLC module.

[0022] Alternatively, the condensation mechanism may further include: a transfer pipe and a transfer valve;

[0023] The output of one of the condensers is connected to the input of the other condenser via the adapter pipe, and the adapter valve is installed on the adapter pipe.

[0024] Alternatively, the impurity gas recovery mechanism may further include: an impurity gas valve body; the impurity gas valve body is installed on the impurity gas input pipe, and the impurity gas valve body is communicatively connected to the PLC module.

[0025] Alternatively, the transfer valve can be a solenoid valve, and the transfer valve is communicatively connected to the PLC module.

[0026] Optimally, the liquid nitrogen supply device and the nitrogen gas supply device each include: a nitrogen source container, a nitrogen outlet pipe, and a control valve;

[0027] The output end of the nitrogen source container is connected to the input end of the nitrogen outlet pipe, the output end of the nitrogen outlet pipe is connected to the input end of the nitrogen supply pipe, and the control valves are respectively installed on the nitrogen outlet pipe.

[0028] An LNG fuel tank is provided with the exhaust gas recovery system described above.

[0029] Compared with the prior art, one of the above technical solutions has the following beneficial effects:

[0030] This solution provides an LNG fuel tank exhaust gas recovery system. It first uses a nitrogen supply mechanism to deliver nitrogen to a condenser and a nitrogen residual cooling recovery device, and then uses a miscellaneous gas input pipe to send the nitrogen through the nitrogen residual cooling recovery device before entering the condenser. This fully utilizes nitrogen at different locations to recover the components to be recovered. This solution can replace the practice of direct combustion to maintain low pressure in the fuel tank and solves the problem of waste caused by the combustion of natural gas in the existing differential pressure refueling method. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of one embodiment of the exhaust gas recovery system for an LNG fuel tank;

[0032] in:

[0033] 1. Condensation mechanism; 2. Nitrogen supply mechanism; 3. Impurity gas recovery mechanism; 4. Exhaust gas emission mechanism; 5. Natural gas storage mechanism; 6. PLC module;

[0034] Condenser 11; Adapter pipe 12; Adapter valve 13;

[0035] Liquid nitrogen supply device 21, nitrogen gas supply device 22, nitrogen residual cooling recovery device 23, nitrogen supply pipe 24;

[0036] Nitrogen source container 201, nitrogen outlet pipe 202, control valve 203;

[0037] Impurity gas inlet pipe 31, impurity gas outlet pipe 32; intake gas composition detection device 33, intake parameter detection device 34; impurity gas valve body 35;

[0038] Intake flow detection device 341, intake temperature detection device 342, intake pressure detection device 343;

[0039] Exhaust pipe 41, exhaust gas detection device 42;

[0040] Exhaust gas composition detection device 421, exhaust gas flow detection device 422, exhaust gas temperature detection device 423, and exhaust gas pressure detection device 424. Detailed Implementation

[0041] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0042] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "transverse," "length," "width," "thickness," "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," "outer," "inner side," "outer side," "inner end," "outer end," "axial," "radial," and "circumferential," etc., indicating the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, features defined with "first" and "second" may explicitly or implicitly include one or more of these features, used to distinguish descriptive features, without any order or emphasis. In the description of this utility model, unless otherwise stated, "multiple" means two or more.

[0043] like Figure 1 An LNG fuel tank exhaust gas recovery system includes: a condensation unit 1, a nitrogen supply unit 2, a miscellaneous gas recovery unit 3, an exhaust gas emission unit 4, and a natural gas storage unit 5.

[0044] The condensation mechanism 1 includes: a condenser 11;

[0045] The nitrogen supply mechanism 2 includes: a liquid nitrogen supply device 21, a nitrogen gas supply device 22, a nitrogen residual cooling recovery device 23, and a nitrogen supply pipe 24;

[0046] The output end of the liquid nitrogen supply device 21 and the output end of the nitrogen supply device 22 are respectively connected to the nitrogen supply pipe 24; there are multiple condensers 11; the nitrogen supply pipe 24 passes through the interior of multiple condensers 11 and then passes through the nitrogen waste cooling recovery device 23.

[0047] The impurity gas recovery mechanism 3 includes: an impurity gas inlet pipe 31 and an impurity gas outlet pipe 32;

[0048] The impurity gas input pipe 31 passes through the nitrogen residual cooling recovery device 23, and the output end of the impurity gas input pipe 31 is connected to the input end of the plurality of condensers 11 respectively; the output end of the impurity gas output pipe 32 is connected to the exhaust gas emission mechanism 4.

[0049] The input end of the natural gas storage device 5 is connected to the output end of the condenser 11 below.

[0050] This solution provides an LNG fuel tank exhaust gas recovery system. It first uses a nitrogen supply mechanism 2 to deliver nitrogen to the condenser 11 and the nitrogen residual cooling recovery device 23. Then, it uses a miscellaneous gas input pipe 31 to send the nitrogen through the nitrogen residual cooling recovery device 23 before entering the condenser 11. This fully utilizes nitrogen at different locations to recover the components to be recovered. This solution can replace the practice of direct combustion to maintain the low pressure of the fuel tank and solves the problem of waste caused by the main combustion treatment of exhaust gas in existing LNG fuel tanks.

[0051] Specifically, the nitrogen supply mechanism 2 includes a liquid nitrogen supply device 21 and a nitrogen gas supply device 22. The liquid nitrogen supply device 21 is mainly used to store liquid nitrogen, and the nitrogen gas supply device 22 is mainly used to store nitrogen gas. Liquid nitrogen is obtained by cooling nitrogen gas to below -195.8°C, so the temperature of the nitrogen output from the liquid nitrogen supply device 21 is lower than the temperature of the nitrogen output from the nitrogen gas supply device 22. This scheme can select at least one of the liquid nitrogen supply device 21 and the nitrogen gas supply device 22 to output nitrogen to the nitrogen supply pipe 24 as needed, so that low-temperature liquid nitrogen and / or room-temperature nitrogen gas are output to the nitrogen supply pipe 24. When relatively lower-temperature nitrogen is required, this scheme can increase the liquid nitrogen output ratio of the liquid nitrogen supply device 21. When a relatively higher temperature nitrogen is required, this solution can increase the nitrogen output ratio of the nitrogen supply device 22; the nitrogen supply pipe 24 passes through the interior of the condenser 11 to provide cooling capacity to the condenser 11, and then passes through the nitrogen residual cooling recovery device 23; after the nitrogen provides the main cooling capacity to one or more condensers 11, it finally passes through the nitrogen residual cooling recovery device 23, and the cooling capacity of the nitrogen residual cooling recovery device 23 will be lower than that of the condenser 11; for this reason, this solution cleverly uses the nitrogen residual cooling recovery device 23 to further utilize the residual cooling of nitrogen, mainly when the gas to be recovered enters the impurity gas recovery mechanism 3, the gas to be recovered first passes through the nitrogen residual cooling recovery device 23 through the impurity gas input pipe 31, and then is output to the condenser 11. The nitrogen residual cooling recovery device 23 utilizes the residual cooling of nitrogen to pre-cool the gas to be recovered. The gas to be recovered can absorb the cooling capacity of the low-temperature nitrogen in the nitrogen residual cooling recovery device 23, and the temperature of the gas to be recovered is initially reduced. The gas to be recovered is then output to the condenser 11 through the output end of the miscellaneous gas input pipe 31. The gas to be recovered further absorbs cooling capacity in the condenser 11. Generally, the main components of the gas to be recovered are nitrogen and methane, and a small amount of ethane and propane, as well as trace amounts of helium and argon. Since this scheme can select either the liquid nitrogen supply device 21 or the nitrogen supply device 22 to output nitrogen at different temperatures to the nitrogen supply pipe 24 as needed, and the nitrogen in the nitrogen supply pipe 24 passes through the condenser 11, the minimum temperature of the condenser 11 can be -195°C. 8℃; When the condenser 11 needs to be heated, nitrogen can be supplied to the nitrogen supply pipe 24 using the nitrogen supply device 22; In this way, the temperature of the condenser 11 can be adjusted to -185.7℃, liquefying the argon. The argon sinks to the bottom wall of the condenser 11 under the action of gravity, and can be collected at the output end below the condenser 11. Alternatively, the argon recovery step can be omitted due to the small amount of argon. Similarly, the temperature of the condenser 11 can be adjusted to -185.7℃ to -83℃, so that the methane, ethane and propane components waiting to be recovered are liquefied separately or simultaneously. Single or multiple combustible gases can be collected at the output end below the condenser 11 through the natural gas storage device 5, so that the combustible gases are collected in the natural gas storage device 5.The remaining nitrogen and a small amount of helium are non-toxic gases and can be directly output to the exhaust gas emission mechanism 4 through the miscellaneous gas output pipe 32. The exhaust gas emission mechanism 4 then recovers the nitrogen and the small amount of helium or directly discharges them. In this way, this solution can utilize nitrogen from different locations to recover the components to be recovered. This solution can replace the practice of direct combustion to maintain low pressure in the fuel tank, solving the problem of waste caused by the main combustion treatment of exhaust gas in existing LNG fuel tanks.

[0052] Optimally, it also includes: PLC module 6;

[0053] The PLC module 6 is communicatively connected to the impurity gas recovery mechanism 3 and the nitrogen supply mechanism 2;

[0054] The impurity gas recovery mechanism 3 further includes: an intake gas composition detection device 33 and an intake parameter detection device 34;

[0055] The intake gas composition detection device 33 and the intake parameter detection device 34 are respectively installed on the impurity gas input pipe 31 and located between the input end of the impurity gas input pipe 31 and the nitrogen residual cooling recovery device 23.

[0056] This solution can be further equipped with a PLC module 6. The PLC module 6 is a known mechanism, a digital computing and operating electronic system designed for industrial applications. It typically employs a programmable memory, storing instructions for performing logical operations, sequential control, timing, counting, and arithmetic operations. It controls various types of mechanical equipment or production processes through digital or analog input / output. In this solution, the PLC module 6 is communicatively connected to the impurity gas recovery mechanism 3 and the nitrogen supply mechanism 2. The intake gas composition detection device 33 can be a known mechanism for detecting gas composition, used to analyze the gas to be recovered input at the input end of the impurity gas input pipe 31. The intake parameter detection device 34 can detect the physical parameters of the gas to be recovered, such as at least one of flow rate, temperature, and pressure. The intake gas composition detection device 33 and the intake parameter detection device 34 can feed back the detection results to the PLC module 6. The PLC module 6 can adjust the nitrogen supply mechanism 2 according to the detection results, and can adjust the output parameters of the liquid nitrogen supply device 21 and the nitrogen supply device 22, thereby controlling the cooling capacity of the condenser 11 and the nitrogen residual cooling recovery device 23 by controlling the cooling capacity of the nitrogen supply pipe 24.

[0057] The communication connection method here refers to the communication established between connected devices through signal transmission and interaction, which can be divided into wired connection and wireless connection; wired connection is such as conventional data cable connection; wireless connection is such as conventional WiFi, Bluetooth, infrared, NFC, etc.

[0058] Optimally, the intake parameter detection device 34 includes: an intake flow detection device 341, an intake temperature detection device 342, and an intake pressure detection device 343;

[0059] The intake flow detection device 341, intake temperature detection device 342, and intake pressure detection device 343 are respectively installed on the impurity gas input pipe 31 and located between the input end of the impurity gas input pipe 31 and the nitrogen residual cooling recovery device 23.

[0060] In this preferred embodiment, before the gas to be recovered enters the condenser 11, the parameters of the gas to be recovered are detected using an inlet flow rate detection device 341, an inlet temperature detection device 342, and an inlet pressure detection device 343. The inlet flow rate detection device 341 detects the flow rate of the gas to be recovered, the inlet temperature detection device 342 detects the temperature of the gas to be recovered, and the inlet pressure detection device 343 detects the pressure of the gas to be recovered. In this way, the inlet parameter detection device 34 can feed back the flow rate, temperature, and pressure parameters of the gas to be recovered as inlet detection results to the PLC module 6. The PLC module 6 adjusts the output parameters of the liquid nitrogen supply device 21 and the nitrogen supply device 22 according to the above inlet detection results.

[0061] Optimally, the exhaust emission mechanism 4 includes: an exhaust pipe 41 and an exhaust gas detection device 42;

[0062] The exhaust gas detection device 42 includes: an exhaust gas composition detection device 421, an exhaust gas flow detection device 422, an exhaust gas temperature detection device 423, and an exhaust gas pressure detection device 424.

[0063] The input end of the exhaust pipe 41 is connected to the output end of the miscellaneous gas output pipe 32; the exhaust gas flow detection device 422, the exhaust gas temperature detection device 423 and the exhaust gas pressure detection device 424 are respectively installed on the exhaust pipe 41; the exhaust gas detection device 42 is communicatively connected to the PLC module 6.

[0064] This solution can also be equipped with an exhaust gas composition detection device 421, an exhaust gas flow detection device 422, an exhaust gas temperature detection device 423, and an exhaust gas pressure detection device 424, all with exhaust gas detection functions, in the exhaust pipe 41. Similar to the intake parameter detection device 34, the exhaust gas composition detection device 421 can be used to analyze the gas composition of the exhaust gas in the exhaust pipe 41; the exhaust gas flow detection device 422 is used to detect the flow rate of the exhaust gas in the exhaust pipe 41, the exhaust gas temperature detection device 423 is used to detect the temperature of the exhaust gas in the exhaust pipe 41, and the exhaust gas pressure detection device 424 is used to detect the pressure of the exhaust gas in the exhaust pipe 41. Thus, the exhaust gas composition detection device 421, exhaust gas flow detection device 422, exhaust gas temperature detection device 423, and exhaust gas pressure detection device 424 acquire the composition, flow, temperature, and pressure parameters of the exhaust gas at the time of discharge, and can feed the results back to the PLC module 6 in real time. The PLC module 6, in conjunction with the feedback from the impurity gas recovery mechanism 3, controls the cooling capacity of the condenser 11 and the nitrogen residual cooling recovery device 23 in real time by controlling the cooling capacity of the nitrogen supply pipe 24.

[0065] Alternatively, the condensation mechanism 1 may further include: a transfer pipe 12 and a transfer valve 13;

[0066] The output of one of the condensers 11 is connected to the input of the other condenser 11 via the adapter pipe 12, and the adapter valve 13 is installed on the adapter pipe 12.

[0067] The system can have multiple condensers 11. A connecting pipe 12 connects two adjacent condensers 11. The connecting pipe 12 is equipped with a connecting valve 13, which controls the flow rate and pressure of the connecting pipe 12. Some condensers 11 are interconnected. When the gas to be recovered is input through the impurity gas input pipe 31, the gas passes through the inlet parameter detection device 34. The PLC module 6 determines whether to open or close the connecting valve 13 based on the result. This can be done manually or automatically. For example, when the flow rate of the gas to be recovered is large, at least two condensers 11 can be used to recover the gas synchronously. The connecting valve 13 can be replaced by a known valve body.

[0068] Alternatively, the impurity gas recovery mechanism 3 may further include an impurity gas valve body 35; the impurity gas valve body 35 is installed on the impurity gas input pipe 31, and the impurity gas valve body 35 is communicatively connected to the PLC module 6.

[0069] A miscellaneous gas inlet pipe 31 is equipped with a miscellaneous gas valve body 35. Since there are multiple condensers 11, and the inlet end of each condenser 11 is connected to the miscellaneous gas inlet pipe 31, the gas to be recovered can be output to different condensers 11 through different miscellaneous gas inlet pipes 31 after the gas to be recovered is introduced into the miscellaneous gas inlet pipe 31. In this regard, the PLC module 6 can control the miscellaneous gas valve body 35 according to the feedback from the intake gas composition detection device 33 and the intake parameter detection device 34, thereby controlling the gas to be recovered to enter part of the miscellaneous gas inlet pipe 31 and enter different condensers 11. Since some condensers 11 are connected by a transfer pipe 12, the PLC module 6 can flow through a specific number of condensers 11, thereby controlling the path of the gas to be recovered according to the feedback result, ensuring that the temperature of the condenser 11 is suitable for the gas to be recovered at a specific parameter, thus improving the recovery efficiency.

[0070] Alternatively, the transfer valve 13 can be a solenoid valve, and the transfer valve 13 is communicatively connected to the PLC module 6.

[0071] The PLC module 6 can control the solenoid valve in real time based on the feedback results of the intake gas composition detection device 33 and the intake parameter detection device 34, thereby controlling the connection state between the condenser 11 and the condenser 11.

[0072] Optimally, the liquid nitrogen supply device 21 and the nitrogen supply device 22 respectively include: a nitrogen source container 201, a nitrogen outlet pipe 202, and a control valve 203;

[0073] The output end of the nitrogen source container 201 is connected to the input end of the nitrogen outlet pipe 202, the output end of the nitrogen outlet pipe 202 is connected to the input end of the nitrogen supply pipe 24, and the control valves 203 are respectively installed on the nitrogen outlet pipe 202.

[0074] Liquid nitrogen supply device 21 and nitrogen gas supply device 22 each include a nitrogen source container 201, a nitrogen outlet pipe 202, and a control valve 203. The nitrogen source container 201 of liquid nitrogen supply device 21 is used to store and / or transfer liquid nitrogen; the nitrogen source container 201 of nitrogen gas supply device 22 is used to store and / or transfer nitrogen gas; after receiving nitrogen from nitrogen source container 201, nitrogen outlet pipe 202 can be pressurized (e.g., using a pump) and delivered to nitrogen supply pipe 24. Control valve 203 can control the flow rate of nitrogen in nitrogen outlet pipe 202. Liquid nitrogen supply device 21 and nitrogen gas supply device 22 can adjust control valve 203 according to instructions from PLC module 6 to match the flow rate, temperature, and pressure parameters of the gas to be recovered, ensuring that the system can adjust the cooling capacity of condenser 11 and nitrogen waste cooling recovery device 23 in real time according to the input of the gas to be recovered.

[0075] An LNG fuel tank is provided with an exhaust gas recovery system for an LNG fuel tank according to any of the above embodiments.

[0076] This system can determine whether it is operating normally by measuring the temperatures of the intake air temperature detection device 342 and the exhaust air temperature detection device 423. It can also determine the actual recovery effect of the system by measuring the flow difference between the intake air flow detection device 341 and the exhaust air flow detection device 422. Furthermore, it can determine the difference between theory and practice by analyzing the composition of the exhaust gas composition detection device 421 and the intake gas composition detection device 33. The composition analysis can serve as a data reference for subsequent system improvements.

[0077] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A tail gas recovery system for an LNG fuel tank, characterized in that, include: Condensation system, nitrogen supply system, miscellaneous gas recovery system, exhaust gas emission system, and natural gas storage system; The condensation mechanism includes: a condenser; The nitrogen supply mechanism includes: a liquid nitrogen supply device, a nitrogen gas supply device, a nitrogen residual cooling recovery device, and a nitrogen supply pipe; The output ends of the liquid nitrogen supply device and the nitrogen gas supply device are respectively connected to the nitrogen supply pipe; there are multiple condensers; the nitrogen supply pipe passes through the interior of multiple condensers and then through the nitrogen waste heat recovery device; The impurity gas recovery mechanism includes: an impurity gas inlet pipe and an impurity gas outlet pipe; The impurity gas input pipe passes through the nitrogen residual cooling recovery device, and the output end of the impurity gas input pipe is connected to the input end of the plurality of condensers respectively; the output end of the impurity gas output pipe is connected to the exhaust gas emission mechanism. The input end of the natural gas storage device is connected to the output end of the condenser below.

2. The LNG fuel tank exhaust gas recovery system according to claim 1, characterized in that, Also includes: PLC module; The PLC module is communicatively connected to the impurity gas recovery mechanism and the nitrogen supply mechanism; The impurity gas recovery mechanism also includes: an intake gas composition detection device and an intake parameter detection device; The intake gas composition detection device and the intake parameter detection device are respectively installed on the impurity gas input pipe and located between the input end of the impurity gas input pipe and the nitrogen residual cooling recovery device.

3. The LNG fuel tank exhaust gas recovery system according to claim 2, characterized in that, The intake parameter detection device includes: an intake flow detection device, an intake temperature detection device, and an intake pressure detection device; The intake flow detection device, intake temperature detection device, and intake pressure detection device are respectively installed on the impurity gas input pipe and located between the input end of the impurity gas input pipe and the nitrogen residual cooling recovery device.

4. The LNG fuel tank exhaust gas recovery system according to claim 3, characterized in that, The exhaust emission mechanism includes: an exhaust pipe and an exhaust gas detection device; The exhaust gas detection device includes: an exhaust gas composition detection device, an exhaust gas flow detection device, an exhaust gas temperature detection device, and an exhaust gas pressure detection device. The input end of the exhaust pipe is connected to the output end of the miscellaneous gas output pipe; the exhaust gas flow detection device, the exhaust gas temperature detection device, and the exhaust gas pressure detection device are respectively installed on the exhaust pipe; the exhaust gas detection device is communicatively connected to the PLC module.

5. The LNG fuel tank exhaust gas recovery system according to claim 2, characterized in that, The condensation mechanism also includes: a transfer pipe and a transfer valve; The output of one of the condensers is connected to the input of the other condenser via the adapter pipe, and the adapter valve is installed on the adapter pipe.

6. The exhaust gas recovery system for an LNG fuel tank according to claim 5, characterized in that, The impurity gas recovery mechanism further includes: an impurity gas valve body; the impurity gas valve body is installed on the impurity gas input pipe, and the impurity gas valve body is communicatively connected to the PLC module.

7. The LNG fuel tank exhaust gas recovery system according to claim 5, characterized in that, The adapter valve is a solenoid valve, and the adapter valve is communicatively connected to the PLC module.

8. A tail gas recovery system for an LNG fuel tank according to any one of claims 1-7, characterized in that, The liquid nitrogen supply device and the nitrogen gas supply device each include: a nitrogen source container, a nitrogen outlet pipe, and a control valve; The output end of the nitrogen source container is connected to the input end of the nitrogen outlet pipe, the output end of the nitrogen outlet pipe is connected to the input end of the nitrogen supply pipe, and the control valves are respectively installed on the nitrogen outlet pipe.

9. An LNG fuel tank, characterized in that, The system includes an exhaust gas recovery system for an LNG fuel tank as described in any one of claims 1-8.

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