Truck loading waste gas liquid nitrogen cryogenic recovery system

Abstract

The utility model discloses a liquid nitrogen cryogenic recovery system for truck loading waste gas, and relates to the technical field of waste gas. According to the technical scheme, the device comprises a first feeding and discharging heat exchanger, a second feeding and discharging heat exchanger, a first secondary cooler, a second secondary cooler, a first liquid nitrogen cooler and a second liquid nitrogen cooler; a tube pass feeding hole of the liquid nitrogen cooler I and a tube pass feeding hole of the liquid nitrogen cooler II are connected with a liquid nitrogen feeding pipeline and a low-temperature nitrogen feeding pipeline, a valve I and a valve II are arranged on the liquid nitrogen feeding pipeline, and a valve III and a valve IV are arranged on the low-temperature nitrogen feeding pipeline; a valve V and a valve VI are respectively arranged on tube pass discharging pipelines of the liquid nitrogen cooler I and the liquid nitrogen cooler II; and a valve VII and a valve VIII are respectively arranged on nitrogen discharging pipelines of the liquid nitrogen cooler I and the liquid nitrogen cooler II. When the liquid nitrogen coolers are switched, the standby liquid nitrogen coolers are subjected to precooling and subzero treatment, so that the standby liquid nitrogen coolers can reach the use temperature after being switched, and the effective treatment of loading waste gas and the stable operation of the system are ensured.

Description

Technical Field

[0001] The utility model relates to the technical field of waste gas treatment, in particular to a liquid nitrogen deep-cold recovery system for loading waste gas. Background Art

[0002] The loading exhaust gas is treated by the "Freon condensation + adsorption" process, which uses Freon to cool the loading exhaust gas, so that most of the oil is liquefied and recovered, and the remaining small amount of oil and gas is recovered by adsorption to achieve qualified discharge of loading exhaust gas. However, this method has the following problems: the adsorption material needs to be replaced frequently and cannot reach the condensation temperature in time, which affects loading and consumes a lot of materials.

[0003] When a liquid nitrogen cryogenic unit is used to treat loading waste gas, the liquid nitrogen cryogenic unit includes a standby inlet and outlet heat exchanger, a standby secondary cooler, and a standby liquid nitrogen cooler. The waste gas is cooled multiple times to recover the oil phase and form qualified waste gas that can be discharged. However, this treatment process has the following problems: when the liquid nitrogen cryogenic unit runs for too long, it is easy to cause frost in the liquid nitrogen cooler, causing its pressure difference to be too high, and as the pressure difference increases, the non-methane total hydrocarbon value in the exhaust gas gradually increases, causing shutdown, which is not conducive to operation, and the liquid nitrogen cooler needs to be reheated. The current reheating operation is as follows: the two liquid nitrogen coolers are automatically switched at a fixed time. After switching, the low-temperature nitrogen at the outlet of the secondary cooler pipe is heated by a heater, and the heated nitrogen reheats the liquid nitrogen cooler that has been switched off. However, since the spare liquid nitrogen cooler is not cooled, it will not reach the use temperature after direct switching, which may easily lead to unqualified exhaust gas. Utility Model Content

[0004] The technical problem to be solved by the utility model is: to overcome the shortcomings of the prior art and provide a liquid nitrogen cryogenic recovery system for loading waste gas, which can pre-cool and cryogenically treat the spare liquid nitrogen cooler in advance when the liquid nitrogen cooler is switched, so as to ensure that it can reach the use temperature after switching, thereby ensuring the effective treatment of the loading waste gas and the smooth operation of the system.

[0005] The technical solution of the utility model is:

[0006] The loading waste gas liquid nitrogen deep cold recovery system comprises an inlet and outlet heat exchanger 1 and an inlet and outlet heat exchanger 2, the shell side feed ports of the inlet and outlet heat exchanger 1 and the inlet and outlet heat exchanger 2 are connected with a loading waste gas feed pipeline, the shell side discharge ports of the inlet and outlet heat exchanger 1 and the inlet and outlet heat exchanger 2 are respectively connected with a shell side discharge pipeline, and the shell side discharge pipeline is connected to the shell side feed ports of the secondary cooler 1 and the secondary cooler 2 through the shell side feed pipeline; the secondary cooler 1 and the secondary cooler The shell-side discharge ports of the second heat exchanger are respectively connected to the shell-side discharge pipelines, and the shell-side discharge pipelines are connected to the shell-side feed ports of the liquid nitrogen cooler 1 and the liquid nitrogen cooler 2 through the shell-side feed pipelines; the shell-side discharge ports of the liquid nitrogen cooler 1 and the liquid nitrogen cooler 2 are respectively connected to the shell-side discharge pipelines, and the shell-side discharge pipelines are connected to the tube-side feed ports of the inlet and outlet heat exchanger 1 and the inlet and outlet heat exchanger 2 through the tube-side feed pipelines; the tube-side discharge ports of the inlet and outlet heat exchanger 1 and the inlet and outlet heat exchanger 2 A waste gas discharge pipeline is connected; the pipe-side feed ports of the liquid nitrogen cooler 1 and the liquid nitrogen cooler 2 are connected with a liquid nitrogen feed pipeline and a low-temperature nitrogen feed pipeline, the pipe-side discharge ports of the liquid nitrogen cooler 1 and the liquid nitrogen cooler 2 are respectively connected with a pipe-side discharge pipeline and a nitrogen discharge pipeline, the pipe-side discharge pipeline is connected with the pipe-side feed ports of the secondary cooler 1 and the secondary cooler 2 through the pipe-side feed pipeline, and the pipe-side discharge ports of the secondary cooler 1 and the secondary cooler 2 are connected with a low-temperature nitrogen discharge pipeline; valves 1 and 2 are respectively provided on the liquid nitrogen feed pipelines of the liquid nitrogen cooler 1 and the liquid nitrogen cooler 2, valves 3 and 4 are respectively provided on the low-temperature nitrogen feed pipelines of the liquid nitrogen cooler 1 and the liquid nitrogen cooler 2, valves 5 and 6 are respectively provided on the pipe-side discharge pipelines of the liquid nitrogen cooler 1 and the liquid nitrogen cooler 2, and valves 7 and 8 are respectively provided on the nitrogen discharge pipelines of the liquid nitrogen cooler 1 and the liquid nitrogen cooler 2.

[0007] Preferably, the loading exhaust gas feed pipeline is provided with a fan and connected to a salt cooler.

[0008] Preferably, the tube-side discharge ports of the secondary cooler 1 and the secondary cooler 2 are also connected to a rewarming nitrogen discharge pipeline, and a vaporizer is connected to the rewarming nitrogen discharge pipeline.

[0009] Preferably, a valve is provided on the rewarming nitrogen discharge pipeline.

[0010] Preferably, the shell-side feed ports of the first inlet and outlet heat exchanger and the second inlet and outlet heat exchanger are also connected to a nitrogen feed pipeline.

[0011] Preferably, liquid collecting tanks are respectively provided at the bottoms of the first inlet and outlet heat exchanger, the second inlet and outlet heat exchanger, the first secondary cooler, the second secondary cooler, the first liquid nitrogen cooler and the second liquid nitrogen cooler.

[0012] Preferably, valves are respectively provided on the loading exhaust gas feed pipeline, the shell-side discharge pipeline and the tube-side feed pipeline of the inlet and outlet heat exchanger 1 and the inlet and outlet heat exchanger 2; valves are respectively provided on the shell-side feed pipeline, shell-side discharge pipeline, tube-side feed pipeline and low-temperature nitrogen discharge pipeline of the secondary cooler 1 and the secondary cooler 2; valves are respectively provided on the shell-side feed pipeline and shell-side discharge pipeline of the liquid nitrogen cooler 1 and the liquid nitrogen cooler 2.

[0013] Compared with the prior art, the utility model has the following beneficial effects:

[0014] The cryogenic recovery system of the utility model can not only cool the loading exhaust gas to recover the oil phase therein and form qualified exhaust gas for external discharge, but also can pre-cool and cryogenically treat the spare liquid nitrogen cooler in advance when the liquid nitrogen cooler is switched, so as to ensure that it can reach the use temperature after switching, thereby ensuring the effective treatment of the loading exhaust gas and the smooth operation of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of a loading waste gas liquid nitrogen deep cold recovery system of the utility model.

[0016] In the figure, 1. Inlet and outlet heat exchanger 1; 2. Inlet and outlet heat exchanger 2; 3. Loading exhaust gas feed pipeline; 4. Secondary cooler 1; 5. Secondary cooler 2; 6. Liquid nitrogen cooler 1; 7. Liquid nitrogen cooler 2; 8. Exhaust gas discharge pipeline; 9. Liquid nitrogen feed pipeline; 10. Low-temperature nitrogen feed pipeline; 11. Nitrogen discharge pipeline; 12. Low-temperature nitrogen discharge pipeline; 13. Valve 1; 14. Valve 2; 15. Valve 3; 16. Valve 4; 17. Valve 5; 18. Valve 6; 19. Valve 7; 20. Valve 8; 21. Rewarming nitrogen discharge pipeline; 22. Valve; 23. Liquid collecting tank. DETAILED DESCRIPTION

[0017] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0018] Example 1

[0019] like Figure 1As shown, the loading waste gas liquid nitrogen deep cold recovery system of this embodiment includes an inlet and outlet heat exchanger 1 and an inlet and outlet heat exchanger 2. The shell side feed ports of the inlet and outlet heat exchanger 1 and the inlet and outlet heat exchanger 2 are connected to a loading waste gas feed pipeline 3. A valve 22 is provided on the loading waste gas feed pipeline 3. The loading waste gas enters the shell side of the inlet and outlet heat exchanger 1 or the inlet and outlet heat exchanger 2 2 through the loading waste gas feed pipeline 3. The shell-side discharge ports of the inlet and outlet heat exchanger 1 and the inlet and outlet heat exchanger 2 are respectively connected with shell-side discharge pipelines, and the shell-side discharge pipelines are connected with the shell-side feed ports of the secondary cooler 1 and the secondary cooler 2 through the shell-side feed pipelines. The shell-side discharge pipelines and the tube-side feed pipelines of the inlet and outlet heat exchanger 1 and the inlet and outlet heat exchanger 2 are respectively provided with valves 22, and the shell-side feed pipelines of the secondary cooler 4 and the secondary cooler 2 are provided with valves. After being cooled by the inlet and outlet heat exchanger 1 or the inlet and outlet heat exchanger 2, the loading exhaust gas enters the shell side of the secondary cooler 4 or the secondary cooler 25 for further cooling. The shell side discharge ports of the secondary cooler 14 and the secondary cooler 25 are respectively connected to the shell side discharge pipeline, and the shell side discharge pipeline is connected to the shell side feed port of the liquid nitrogen cooler 16 and the liquid nitrogen cooler 27 through the shell side feed pipeline, and the tube side feed port of the liquid nitrogen cooler 16 and the liquid nitrogen cooler 27 is connected to the liquid nitrogen feed pipeline 9; the shell side discharge pipelines of the secondary cooler 14 and the secondary cooler 25, and the shell side feed pipelines of the liquid nitrogen cooler 16 and the liquid nitrogen cooler 27 are respectively provided with valves 22. After further cooling, the loading waste gas enters the shell side of the liquid nitrogen cooler 16 or the liquid nitrogen cooler 27 for deep cooling to become qualified waste gas that can be discharged (temperature is about -50℃~-70℃).

[0020] At the same time, in this embodiment, Figure 1 As shown, the shell side discharge ports of liquid nitrogen cooler 1 6 and liquid nitrogen cooler 2 7 are respectively connected to shell side discharge pipelines, and the shell side discharge pipelines are connected to the tube side feed ports of inlet and outlet heat exchanger 1 and inlet and outlet heat exchanger 2 through the tube side feed pipelines. Valves 22 are respectively provided on the shell side discharge pipelines of liquid nitrogen cooler 1 6 and liquid nitrogen cooler 2 7. The qualified waste gas after deep cooling is then used as a cooling medium to enter the tube side of inlet and outlet heat exchanger 1 or inlet and outlet heat exchanger 2 2, and the coldness of the qualified waste gas is recovered while the loading waste gas in the shell side is preliminarily cooled. The tube side discharge ports of inlet and outlet heat exchanger 1 and inlet and outlet heat exchanger 2 2 are connected to waste gas discharge pipelines 8, and the qualified waste gas after the coldness is recovered is discharged from the waste gas discharge pipeline 8.

[0021] Among them, Figure 1As shown, the tube-side discharge ports of liquid nitrogen cooler 1 6 and liquid nitrogen cooler 2 7 are respectively connected to tube-side discharge pipelines, and the tube-side discharge pipelines are connected to the tube-side feed ports of secondary cooler 1 4 and secondary cooler 2 5 through tube-side feed pipelines, and the tube-side discharge ports of secondary cooler 1 4 and secondary cooler 2 5 are connected to low-temperature nitrogen discharge pipelines 12; valves 22 are respectively provided on the tube-side feed pipelines and low-temperature nitrogen discharge pipelines 12 of secondary cooler 1 4 and secondary cooler 2 5. The low-temperature nitrogen coming out of the tube-side of liquid nitrogen cooler 1 6 and liquid nitrogen cooler 2 7 enters the tube-side of secondary cooler 1 4 or secondary cooler 2 5 to cool the waste gas in the shell side, and the low-temperature nitrogen coming out of the tube-side of secondary cooler 1 4 or secondary cooler 2 5 enters the pipeline network through the low-temperature nitrogen discharge pipeline 12 for standby use.

[0022] In addition, in this embodiment, if Figure 1 As shown, the pipe-side feed ports of the liquid nitrogen cooler 1 6 and the liquid nitrogen cooler 2 7 are also connected to a low-temperature nitrogen feed pipeline 10, and the pipe-side discharge ports are also connected to a nitrogen discharge pipeline 11; at the same time, valve 13 and valve 2 14 are respectively provided on the liquid nitrogen feed pipeline 9 of the liquid nitrogen cooler 1 6 and the liquid nitrogen cooler 2 7, valve 3 15 and valve 4 16 are respectively provided on the low-temperature nitrogen feed pipeline 10 of the liquid nitrogen cooler 1 6 and the liquid nitrogen cooler 2 7, valve 5 17 and valve 6 18 are respectively provided on the pipe-side discharge pipelines of the liquid nitrogen cooler 1 6 and the liquid nitrogen cooler 2 7, and valve 7 19 and valve 8 20 are respectively provided on the nitrogen discharge pipelines 11 of the liquid nitrogen cooler 1 6 and the liquid nitrogen cooler 2 7.

[0023] To ensure the smooth operation of the system, when the pressure difference of the running liquid nitrogen cooler 1 6 or liquid nitrogen cooler 2 7 is high, it is necessary to switch. Take the high pressure difference of liquid nitrogen cooler 27 as an example for explanation: open valve three 15 on the low-temperature nitrogen feed pipeline 10 of liquid nitrogen cooler 16 and valve seven 19 on the nitrogen discharge pipeline 11, and use low-temperature nitrogen to pre-cool the liquid nitrogen cooler 6; then close valve three 15 on the low-temperature nitrogen feed pipeline 10 of liquid nitrogen cooler 16, and open valve one 13 on its liquid nitrogen feed pipeline 9, and use liquid nitrogen to deep-cool the liquid nitrogen cooler 6; finally, close valve two 14 on the liquid nitrogen feed pipeline 9 of liquid nitrogen cooler 27 and valve six 18 on its pipe-side discharge pipeline, close valve seven 19 on the nitrogen discharge pipeline 11 of liquid nitrogen cooler 16, open valve five 17 on the pipe-side discharge pipeline of liquid nitrogen cooler 16, and complete the switching from liquid nitrogen cooler 27 to liquid nitrogen cooler 16. At the same time, open the valve 8 20 on the nitrogen discharge pipeline 11 of the liquid nitrogen cooler 2 7 to release the nitrogen in the pipeline of the liquid nitrogen cooler 2 7 to prevent safety accidents such as explosions. At the same time, after switching, the liquid nitrogen cooler 2 7 can be naturally reheated during the placement process.

[0024] Working principle:

[0025] The loading waste gas enters the shell side of the inlet and outlet heat exchanger 1 or the inlet and outlet heat exchanger 2 from the loading waste gas feed pipeline 3, and exchanges heat with the deep-cooled qualified waste gas coming out of the shell side of the liquid nitrogen cooler 1 or the liquid nitrogen cooler 2 7, thereby achieving the initial cooling of the waste gas. After that, the waste gas comes out from the shell side discharge pipeline and enters the shell side of the secondary cooler 1 4 or the secondary cooler 2 5 through the shell side feed pipeline, and is further cooled by the low-temperature nitrogen in the tube side. After coming out from the shell side discharge pipeline, it enters the shell side of the liquid nitrogen cooler 1 6 or the liquid nitrogen cooler 2 7 through the shell side feed pipeline, and is deep-cooled by the liquid nitrogen entering the tube side through the liquid nitrogen feed pipeline 9. After the waste gas is cooled three times, the oil phase therein is recovered to form qualified waste gas. After the qualified waste gas comes out from the shell side discharge pipeline, it enters the tube side of the inlet and outlet heat exchanger 1 or the inlet and outlet heat exchanger 2 2 through the tube side feed pipeline, and the loading waste gas in the shell side is preliminarily cooled, the cold energy of the qualified waste gas is recovered, and finally discharged from the waste gas discharge pipeline 8.

[0026] The liquid nitrogen in the tube side of the liquid nitrogen cooler 1 6 or the liquid nitrogen cooler 2 7 deep cools the exhaust gas in the shell side to form low-temperature nitrogen, which comes out from the tube side discharge pipeline and then enters the tube side of the secondary cooler 1 4 or the secondary cooler 2 5 through the tube side feed pipeline to further cool the exhaust gas in the shell side. Subsequently, the low-temperature nitrogen in the tube side enters the pipeline network through the low-temperature nitrogen discharge pipeline 12 for standby use.

[0027] When the pressure difference of the running liquid nitrogen cooler 27 is high, it is necessary to switch to the liquid nitrogen cooler 16 to ensure the normal operation of the system. At this time, it is necessary to open the valve 3 15 on the low-temperature nitrogen feed pipeline 10 of the liquid nitrogen cooler 16 and the valve 7 19 on the nitrogen discharge pipeline 11, and use the low-temperature nitrogen to pre-cool the liquid nitrogen cooler 16; then close the valve 3 15 on the low-temperature nitrogen feed pipeline 10 of the liquid nitrogen cooler 16, and open the valve 13 on the liquid nitrogen feed pipeline 9, and use liquid nitrogen to deep-cool the liquid nitrogen cooler 16; finally, close the valve 2 14 on the liquid nitrogen feed pipeline 9 of the liquid nitrogen cooler 27 and the valve 6 18 on the pipe-side discharge pipeline, and close the valve 7 19 on the nitrogen discharge pipeline 11 of the liquid nitrogen cooler 16, open the valve 5 17 on the pipe-side discharge pipeline of the liquid nitrogen cooler 16, and complete the switching of the liquid nitrogen cooler 27 to the liquid nitrogen cooler 16. At the same time, open the valve 8 20 on the nitrogen discharge pipeline 11 of the liquid nitrogen cooler 2 7 to release the nitrogen in the pipeline of the liquid nitrogen cooler 2 7 to prevent safety accidents such as explosions. At the same time, after switching, the liquid nitrogen cooler 2 7 can be naturally reheated during the placement process.

[0028] After using the system of this embodiment, the loading exhaust gas treatment was relatively stable and did not affect the loading; and the actual loading average time was shortened from the original 35 minutes to 20 minutes, achieving effective treatment of loading exhaust gas. After the liquid nitrogen cooler 1 6 and the liquid nitrogen cooler 2 7 were switched, the non-methane total hydrocarbons decreased from a monthly average of 62.47 mg / m 3 Reduced to an average of 12.29 mg / m 3 The exhaust gas compliance rate increased from 74.74% per month to 98.96% per month, achieving smooth operation of the system.

[0029] Example 2

[0030] On the basis of Example 1, a fan is provided on the loading exhaust gas feed pipeline 3 and connected to a salt cooler. After being pressurized by the fan, the loading exhaust gas is pre-cooled by the salt cooler and then enters the shell side of the inlet and outlet heat exchanger 1 or the inlet and outlet heat exchanger 2 for preliminary cooling.

[0031] Example 3

[0032] On the basis of Example 1, Figure 1 As shown, the pipe outlets of the secondary cooler 1 4 and the secondary cooler 2 5 are also connected to a rewarming nitrogen discharge pipeline 21, to which a vaporizer is connected, and a valve is provided on the rewarming nitrogen discharge pipeline 21. Part of the low-temperature nitrogen coming out of the pipes of the secondary cooler 1 4 and the secondary cooler 2 5 is used as a precooling medium when the liquid nitrogen cooler 1 6 and the liquid nitrogen cooler 2 7 are switched, and part of it is rewarmed by the vaporizer to form normal-temperature nitrogen and then enters the pipe network for other uses.

[0033] Example 4

[0034] On the basis of Example 1, the shell side feed ports of the inlet and outlet heat exchanger 1 and the inlet and outlet heat exchanger 2 are also connected with nitrogen feed pipelines. The nitrogen in the nitrogen feed pipeline enters the system together with the loading exhaust gas, which can reduce the oxygen content in the exhaust gas to below 6%, prevent explosion when the oxygen content in the exhaust gas is too high, and ensure the safe operation of the system.

[0035] Example 5

[0036] On the basis of Example 1, Figure 1 As shown, liquid collecting tanks 23 are respectively provided at the bottom of the inlet and outlet heat exchanger 1, the inlet and outlet heat exchanger 2, the secondary cooler 1, the secondary cooler 2, the secondary cooler 2, the liquid nitrogen cooler 1, and the liquid nitrogen cooler 2, and the condensed materials at the bottom of the shell side of the inlet and outlet heat exchanger 1, the inlet and outlet heat exchanger 2, the secondary cooler 1, the secondary cooler 2, the secondary cooler 2, the liquid nitrogen cooler 1, and the liquid nitrogen cooler 2, are recovered into the liquid collecting tank 23.

Claims

1. Loading waste gas liquid nitrogen cryogenic recovery system, characterized in that: The invention comprises an inlet and outlet heat exchanger 1 (1) and an inlet and outlet heat exchanger 2 (2), wherein the shell side feed ports of the inlet and outlet heat exchanger 1 (1) and the inlet and outlet heat exchanger 2 (2) are connected to a loading waste gas feed pipeline (3), the shell side discharge ports of the inlet and outlet heat exchanger 1 (1) and the inlet and outlet heat exchanger 2 (2) are respectively connected to a shell side discharge pipeline, and the shell side discharge pipeline is connected to the shell side feed ports of the secondary cooler 1 (4) and the secondary cooler 2 (5) through the shell side feed pipeline; the shell side discharge ports of the secondary cooler 1 (4) and the secondary cooler 2 (5) are respectively connected to a shell side discharge pipeline The shell-side discharge pipeline is connected to the shell-side feed ports of the liquid nitrogen cooler 1 (6) and the liquid nitrogen cooler 2 (7) through the shell-side feed pipeline; the shell-side discharge ports of the liquid nitrogen cooler 1 (6) and the liquid nitrogen cooler 2 (7) are respectively connected to the shell-side discharge pipeline, and the shell-side discharge pipeline is connected to the tube-side feed ports of the inlet and outlet heat exchanger 1 (1) and the inlet and outlet heat exchanger 2 (2) through the tube-side feed pipeline; the tube-side discharge ports of the inlet and outlet heat exchanger 1 (1) and the inlet and outlet heat exchanger 2 (2) are connected to the exhaust gas discharge pipeline (8); the liquid nitrogen cooler 1 (6) and the liquid nitrogen cooler 2 (7) The pipe-side feed port is connected to a liquid nitrogen feed pipeline (9) and a low-temperature nitrogen feed pipeline (10); the pipe-side discharge ports of the liquid nitrogen cooler 1 (6) and the liquid nitrogen cooler 2 (7) are respectively connected to a pipe-side discharge pipeline and a nitrogen discharge pipeline (11); the pipe-side discharge pipeline is connected to the pipe-side feed ports of the secondary cooler 1 (4) and the secondary cooler 2 (5) through the pipe-side feed pipeline; the pipe-side discharge ports of the secondary cooler 1 (4) and the secondary cooler 2 (5) are connected to a low-temperature nitrogen discharge pipeline (12); the liquid nitrogen cooler 1 (6) and the liquid nitrogen cooler 2 (7) are connected to the pipe-side discharge ports of the secondary cooler 1 (4) and the secondary cooler 2 (5); A valve 1 (13) and a valve 2 (14) are respectively provided on the nitrogen feed pipeline (9), a valve 3 (15) and a valve 4 (16) are respectively provided on the low-temperature nitrogen feed pipeline (10) of the liquid nitrogen cooler 1 (6) and the liquid nitrogen cooler 2 (7), a valve 5 (17) and a valve 6 (18) are respectively provided on the pipe-side discharge pipelines of the liquid nitrogen cooler 1 (6) and the liquid nitrogen cooler 2 (7), and a valve 7 (19) and a valve 8 (20) are respectively provided on the nitrogen discharge pipelines (11) of the liquid nitrogen cooler 1 (6) and the liquid nitrogen cooler 2 (7).

2. The loading waste gas liquid nitrogen cryogenic recovery system according to claim 1, characterized in that: The loading waste gas feed pipeline (3) is provided with a fan and connected to a salt cooler.

3. The loading waste gas liquid nitrogen cryogenic recovery system according to claim 1, characterized in that: The pipe-side discharge ports of the secondary cooler 1 (4) and the secondary cooler 2 (5) are also connected to a rewarming nitrogen discharge pipeline (21), and a vaporizer is connected to the rewarming nitrogen discharge pipeline (21).

4. The loading waste gas liquid nitrogen cryogenic recovery system as claimed in claim 3, characterized in that: The rewarming nitrogen discharge pipeline (21) is provided with a valve.

5. The loading waste gas liquid nitrogen cryogenic recovery system according to claim 1, characterized in that: The shell side feed ports of the inlet and outlet heat exchanger 1 (1) and the inlet and outlet heat exchanger 2 (2) are also connected to a nitrogen feed pipeline.

6. The loading waste gas liquid nitrogen cryogenic recovery system according to claim 1, characterized in that: The bottoms of the inlet and outlet heat exchanger 1 (1), the inlet and outlet heat exchanger 2 (2), the secondary cooler 1 (4), the secondary cooler 2 (5), the liquid nitrogen cooler 1 (6) and the liquid nitrogen cooler 2 (7) are respectively provided with liquid collecting tanks (23).

7. The loading waste gas liquid nitrogen cryogenic recovery system according to claim 1, characterized in that: Valves (22) are respectively provided on the loading waste gas feed pipeline (3), the shell-side discharge pipeline and the tube-side feed pipeline of the first inlet and outlet heat exchanger (1) and the second inlet and outlet heat exchanger (2); valves (22) are respectively provided on the shell-side feed pipeline, the shell-side discharge pipeline, the tube-side feed pipeline and the low-temperature nitrogen discharge pipeline (12) of the first secondary cooler (4) and the second secondary cooler (5); valves (22) are respectively provided on the shell-side feed pipeline and the shell-side discharge pipeline of the first liquid nitrogen cooler (6) and the second liquid nitrogen cooler (7).

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