Cold energy recovery system for emptying low-temperature nitrogen of normal-pressure liquid nitrogen storage tank

Abstract

The invention discloses a normal-pressure liquid nitrogen storage tank emptying low-temperature nitrogen cooling capacity recovery system, and relates to the technical field of cryogenic cooling, the normal-pressure liquid nitrogen storage tank emptying low-temperature nitrogen cooling capacity recovery system comprises a liquid nitrogen storage tank, a standby adjusting valve on the liquid nitrogen storage tank is connected with a low-temperature supercharger through a pipeline, and the outlet end of the low-temperature supercharger is connected with a vacuum heat preservation pipeline; the outlet end of the vacuum heat preservation pipeline is connected with an emptying pipeline and a conveying pipeline used for being connected with a nitrogen pipeline in an air separation device, and the output end of the nitrogen pipeline is further connected with a heat exchanger. The supercharged low-temperature nitrogen is conveyed to a nitrogen pipeline in the air separation device through a vacuum heat preservation pipeline and a conveying pipeline, so that the supercharged low-temperature nitrogen is converged with nitrogen produced by the air separation device, then enters the heat exchanger, is subjected to heat exchange with positive flow air in the heat exchanger, is reheated and then is discharged out of the cold box, and therefore the purpose of recycling cold energy is achieved.

Description

Technical Field

[0001] The present invention relates to the field of deep cooling technology, and in particular to a low-temperature nitrogen cooling capacity recovery system for emptying a normal-pressure liquid nitrogen storage tank. Background Art

[0002] The gas phase working pressure of the atmospheric standby regulating valve is usually controlled at around 15KPa. The pressure of the evaporated low-temperature (-195.8℃) nitrogen is low, and the pressure of the nitrogen pipeline in the air separation unit is around 40KPa, which results in the low-temperature nitrogen evaporated from the liquid nitrogen storage tank being unable to be directly sent into the nitrogen pipeline in the air separation unit for mixing. With the continuous construction of the project, there are more and more large-scale atmospheric low-temperature liquid storage tanks. Since the liquid nitrogen produced by the air separation and liquefaction units has no supercooling, there is a natural evaporation of 3%-7% during the liquid feeding, storage and filling process. For a long time, the air separation industry has not found a way to efficiently utilize it, resulting in large cooling capacity and nitrogen losses. Summary of the invention

[0003] The object of the present invention is to provide a low-temperature nitrogen refrigeration recovery system for emptying a normal-pressure liquid nitrogen storage tank, which can effectively recover the emptied refrigeration and nitrogen, avoid wasting refrigeration, and greatly save enterprise costs.

[0004] To achieve the purpose of the present invention, the technical scheme adopted is: a low-temperature nitrogen refrigeration recovery system for emptying a normal-pressure liquid nitrogen storage tank, comprising a liquid nitrogen storage tank, a vent valve and a spare regulating valve on the liquid nitrogen storage tank, the spare regulating valve on the liquid nitrogen storage tank is connected to a low-temperature booster through a pipeline, the outlet end of the low-temperature booster is connected to a vacuum insulation pipeline, the outlet end of the vacuum insulation pipeline is connected to a vent pipeline and a conveying pipeline for connecting to a nitrogen pipeline in an air separation device, and the output end of the nitrogen pipeline is also connected to a heat exchanger.

[0005] Furthermore, it also includes a liquid nitrogen gasification backup system storage tank, a vaporizer, and a piston nitrogen compressor connected in sequence, and a parallel pipeline is also connected between the vaporizer inlet and the vacuum insulation pipeline; the vaporizer outlet is also connected to a gasification pipeline, and the piston nitrogen compressor inlet is provided with a low-pressure nitrogen pipeline connected to a heat exchanger; the piston nitrogen compressor outlet is also provided with a gas supply pipeline 1 for connecting to a gas supply device, and the outlet end of the gasification pipeline is connected in parallel to the gas supply pipeline 1.

[0006] Furthermore, the piston nitrogen compressor outlet is also provided with a second gas supply pipeline for connecting to a liquefaction device or a filling system.

[0007] Furthermore, the outlet pressure of the low-temperature booster is 45 KPa to 55 KPa.

[0008] Furthermore, a regulating valve is installed between the cryogenic booster and the standby regulating valve on the liquid nitrogen storage tank.

[0009] Furthermore, a low-pressure check valve is installed between the cryogenic booster and the standby regulating valve on the liquid nitrogen storage tank, and the low-pressure check valve is linked to the cryogenic booster.

[0010] Furthermore, an emergency shut-off valve is installed at the inlet end of the delivery pipeline, and the emergency shut-off valve is linked to the low-temperature booster.

[0011] Furthermore, an online trace oxygen analyzer is installed on the pipeline between the liquid nitrogen storage tank and the cryogenic booster, and the online trace oxygen analyzer is linked to the emergency shut-off valve.

[0012] Furthermore, a low-pressure check valve is installed on the pipeline between the liquid nitrogen storage tank and the cryogenic booster.

[0013] Furthermore, the sealing gas of the low-temperature booster is high-purity nitrogen.

[0014] The beneficial effects of the present invention are:

[0015] The present invention pressurizes the low-temperature nitrogen discharged from the atmospheric standby regulating valve, so that the pressurized gas can enter the nitrogen pipeline in the air separation device for mixing, and then is sent to the heat exchanger for reheating or sent to the piston nitrogen compressor for use after reheating, thereby effectively recovering the vented cold and nitrogen, avoiding waste of cold, and greatly saving enterprise costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings illustrate exemplary embodiments of the present invention and together with the description serve to explain the principles of the present invention. These drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification.

[0017] Figure 1 The present invention provides a flow chart of a system for recovering low-temperature nitrogen from an atmospheric-pressure liquid nitrogen storage tank.

[0018] Markings and corresponding parts names in the attached drawings:

[0019] 1. Liquid nitrogen storage tank, 2. Cryogenic booster, 3. Vacuum insulation pipeline, 4. Transportation pipeline, 5. Liquid nitrogen gasification backup system storage tank, 6. Vaporizer, 7. Piston nitrogen compressor, 8. Parallel pipeline, 9. Gasification pipeline, 10. Low-pressure nitrogen pipeline, 11. Gas supply pipeline 1, 12. Gas supply pipeline 2, 13. Venting pipeline, 14. Air separation unit, 15. Nitrogen pipeline, 16. Heat exchanger. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below in conjunction with the accompanying drawings and implementation methods. It is understood that the specific implementation methods described herein are only used to explain the relevant content, rather than to limit the present invention. It is also necessary to explain that, for ease of description, only the parts related to the present invention are shown in the accompanying drawings.

[0021] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0022] like Figure 1 As shown, the present invention provides a cold recovery system for emptying low-temperature nitrogen from a normal-pressure liquid nitrogen storage tank, comprising a liquid nitrogen storage tank 1 for storing liquid nitrogen, the liquid nitrogen storage tank 1 having a spare regulating valve and a venting valve, wherein the venting valve is used to ensure the safety of the liquid nitrogen storage tank 1, and the spare regulating valve on the liquid nitrogen storage tank 1 is connected to a low-temperature booster 2 through a pipeline, the low-temperature booster 2 boosts the nitrogen drawn out through the spare regulating valve on the liquid nitrogen storage tank 1, and the outlet end of the low-temperature booster 2 is connected to a vacuum insulation pipeline 3, and the vacuum insulation pipeline 3 can be made of a vacuum tube or a stainless steel pipe. The insulation method of bare tubes and aluminum tubes is adopted, and the outlet end of the vacuum insulation pipe 3 is respectively connected to the vent pipe 13 and the conveying pipe 4 used to be connected to the nitrogen pipe 15 in the air separation device 14, and the output end of the nitrogen pipe 15 is also connected to the heat exchanger 16, so that the nitrogen pressurized by the low-temperature booster 2 can be sent to the nitrogen pipe 15 in the air separation device 14, merged with the nitrogen generated by the air separation device 14, and sent to the heat exchanger 16 after mixing to exchange heat with the positive flow air in the heat exchanger 16, and then discharged from the cold box after reheating, so as to achieve the purpose of recovering cold and nitrogen.

[0023] The present invention also includes a liquid nitrogen gasification backup system storage tank 5, a vaporizer 6, and a piston nitrogen compressor 7 connected in sequence, wherein the vaporizer 6 is an air bath type vaporizer, and the vaporizer 6 is used to reheat the nitrogen pressurized by the low-temperature booster 2, and the piston nitrogen compressor 7 is used to compress the reheated nitrogen to meet the needs of users; a parallel pipeline 8 is also connected between the vaporizer 6 inlet and the vacuum insulation pipeline 3, so that the nitrogen pressurized by the low-temperature booster 2 can be sent to the vaporizer 6 through the parallel pipeline 8 for reheating. Heat, the reheated nitrogen can be sent to the piston nitrogen compressor 7 for compression. At the same time, the inlet of the piston nitrogen compressor 7 is provided with a low-pressure nitrogen pipeline 10 connected to the heat exchanger 16, so that the nitrogen pressurized by the low-temperature booster 2 can be sent to the nitrogen pipeline 15 of the air separation device 14, merged with the nitrogen generated by the air separation device 14, and sent to the heat exchanger 16 after mixing to exchange heat with the positive flow air in the heat exchanger 16, so that the nitrogen reheated by the heat exchanger 16 can be sent to the piston nitrogen compressor 7 for compression.

[0024] The outlet of the vaporizer 6 is also connected to a gasification pipeline 9, and the outlet of the piston nitrogen compressor 7 is also provided with a gas supply pipeline 11 for connecting to a gas supply device. The outlet end of the gasification pipeline 9 is connected in parallel to the gas supply pipeline 11, so that a part of the nitrogen reheated by the vaporizer 6 can enter the piston nitrogen compressor 7 for compression, and the other part of the nitrogen reheated by the vaporizer 6 can be sent to the gas supply pipeline 11 through the gasification pipeline 9 and mixed with the nitrogen compressed by the piston nitrogen compressor 7, and finally through the gas supply pipeline 11 Supply gas to users; at the same time, after being pressurized by the low-temperature booster 2, it is sent to the nitrogen pipeline 15 of the air separation unit 14 for mixing, and after being reheated by the heat exchanger 16, it is sent to the piston nitrogen compressor 7 through the low-pressure nitrogen pipeline 10 for compression, while the other part of the nitrogen reheated by the vaporizer 6 can be sent to the gas supply pipeline 11 through the gasification pipeline 9 and mixed with the nitrogen compressed by the piston nitrogen compressor 7, and finally it can also supply gas to users through the gas supply pipeline 11, thereby realizing the recovery of cold energy.

[0025] The outlet of the piston nitrogen compressor 7 in the recovery system is also provided with a gas supply pipeline 12 for connecting to a liquefaction device or a filling system, so that the nitrogen reheated by the vaporizer 6 can be sent into the gas supply pipeline 11 through the gasification pipeline 9 and mixed with the nitrogen compressed by the piston nitrogen compressor 7. It can also be directly supplied to the liquefaction device or the filling system through the gas supply pipeline to meet the user's usage needs.

[0026] In the present invention, the outlet pressure of the cryogenic booster 2 is 45KPa to 55KPa. Since the gas phase working pressure of the liquid nitrogen storage tank 1 is usually controlled at about 15KPa, in order to ensure that the gas phase in the liquid nitrogen storage tank 1 can enter the nitrogen pipeline 15 in the air separation unit 14 and mix with the nitrogen generated by it, the cryogenic booster 2 can pressurize the nitrogen of about 15KPa to 45KPa to 55KPa, so that the gas phase of the liquid nitrogen storage tank 1 has sufficient pressure to enter the nitrogen pipeline 15 in the air separation unit 14, and enter the heat exchanger 16 after mixing with the nitrogen generated by the air separation unit 14. Preferably, the outlet pressure of the cryogenic booster 2 is 50KPa; the outlet pressure of the piston nitrogen compressor 7 is 0.65MPa.

[0027] In order to prevent the pressure of the liquid nitrogen storage tank 1 from dropping to negative pressure under the suction of the cryogenic booster 2, a regulating valve is installed in front of the cryogenic booster 2 to automatically adjust the pressure of the liquid nitrogen storage tank 1. Specifically, the valve is opened when the pressure of the liquid nitrogen storage tank 1 increases, and is closed when the pressure of the liquid nitrogen storage tank 1 decreases.

[0028] In order to prevent the cryogenic booster 2 from suddenly stopping during operation and causing overpressure due to the nitrogen with a pressure of about 40KPa in the air separation unit 14 flowing back to the liquid nitrogen storage tank 1 through the pipeline, an emergency shut-off valve is installed at the inlet end of the delivery pipeline 4, and a low-pressure check valve is installed between the cryogenic booster 2 and the standby regulating valve on the liquid nitrogen storage tank 1; at the same time, the low-pressure check valve and the emergency shut-off valve are linked to the cryogenic booster 2, so that when the cryogenic booster 2 stops, the low-pressure check valve and the emergency shut-off valve are closed in a chain.

[0029] In order to prevent air from entering the pipeline in this recovery system and causing pollution, the cryogenic booster 2 uses high-purity nitrogen as sealing gas; at the same time, an online trace oxygen analyzer is also installed on the pipeline between the liquid nitrogen storage tank 1 and the cryogenic booster 2. The online trace oxygen analyzer detects the oxygen content in the pipeline online and alarms when it detects that the oxygen content exceeds the standard; at the same time, the online trace oxygen analyzer is linked to the low-pressure check valve, the emergency shut-off valve, and the cryogenic booster 2. When the online trace oxygen analyzer detects that the oxygen content exceeds the standard, the low-pressure check valve and the emergency shut-off valve are closed, and the cryogenic booster 2 is shut down.

[0030] When the recycling system is working:

[0031] Working mode 1: The nitrogen in the liquid nitrogen storage tank 1 is pressurized by the low-temperature booster 2 and then sent to the nitrogen pipeline 15 of the air separation device 14 through the delivery pipeline 4, mixed with the nitrogen generated by the air separation device 14, and then sent to the heat exchanger 16 after mixing to exchange heat with the positive flow air in the heat exchanger 16, and finally sent to the piston nitrogen compressor 7 to be compressed to 0.65MPa, and finally delivered to the user through the air supply pipeline 11.

[0032] Working mode 2: The nitrogen in the liquid nitrogen storage tank 1 is pressurized by the low-temperature booster 2 and then sent to the vaporizer 6 through the parallel pipe 8 for reheating. The reheated nitrogen is sent to the piston nitrogen compressor 7 and compressed to 0.65MPa, and finally transported to the user through the gas supply pipe 11.

[0033] In the description of this specification, the description with reference to the terms "one embodiment / method", "some embodiments / methods", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments / methods or examples. In addition, those skilled in the art may combine and combine the different embodiments / methods or examples described in this specification and the features of the different embodiments / methods or examples, unless they are contradictory.

[0034] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0035] It should be understood by those skilled in the art that the above embodiments are only for the purpose of clearly illustrating the present invention, and are not intended to limit the scope of the present invention. For those skilled in the art, other changes or modifications may be made based on the above disclosure, and these changes or modifications are still within the scope of the present invention.

Claims

1. Low-temperature nitrogen cooling capacity recovery system for emptying atmospheric pressure liquid nitrogen storage tank, characterized in that: The invention comprises a liquid nitrogen storage tank (1), wherein the liquid nitrogen storage tank (1) is provided with a vent valve and a standby regulating valve, wherein the standby regulating valve on the liquid nitrogen storage tank (1) is connected to a cryogenic booster (2) via a pipeline, wherein the outlet end of the cryogenic booster (2) is connected to a vacuum insulation pipeline (3), wherein the outlet end of the vacuum insulation pipeline (3) is connected to a vent pipeline (13) and a delivery pipeline (4) for connecting to a nitrogen pipeline (15) in an air separation device (14), and the output end of the nitrogen pipeline (15) is also connected to a heat exchanger (16).

2. The system for recovering low-temperature nitrogen from an atmospheric pressure liquid nitrogen storage tank according to claim 1, characterized in that: The invention also comprises a liquid nitrogen gasification backup system storage tank (5), a vaporizer (6), and a piston nitrogen compressor (7) which are connected in sequence, and a parallel pipeline (8) is also connected between the vaporizer (6) inlet and the vacuum insulation pipeline (3); the vaporizer (6) outlet is also connected to a vaporization pipeline (9), and the piston nitrogen compressor (7) inlet is provided with a low-pressure nitrogen pipeline (10) connected to a heat exchanger (16); the piston nitrogen compressor (7) outlet is also provided with a gas supply pipeline (11) for connecting to a gas supply device, and the outlet end of the vaporization pipeline (9) is connected in parallel to the gas supply pipeline (11).

3. The system for recovering low-temperature nitrogen from an atmospheric pressure liquid nitrogen storage tank according to claim 2, characterized in that: The outlet of the piston nitrogen compressor (7) is also provided with a second gas supply pipeline (12) for connecting to a liquefaction device or a filling system.

4. The system for recovering low-temperature nitrogen from an atmospheric pressure liquid nitrogen storage tank according to claim 2 or 3, characterized in that: The outlet pressure of the low-temperature booster (2) is 45 KPa to 55 KPa.

5. The system for recovering low-temperature nitrogen from an atmospheric pressure liquid nitrogen storage tank according to claim 2 or 3, characterized in that: A regulating valve is also installed between the low-temperature booster (2) and the standby regulating valve on the liquid nitrogen storage tank (1).

6. The system for recovering low-temperature nitrogen from an atmospheric pressure liquid nitrogen storage tank according to claim 2 or 3, characterized in that: A low-pressure check valve is also installed between the cryogenic booster (2) and the standby regulating valve on the liquid nitrogen storage tank (1), and the low-pressure check valve is linked to the cryogenic booster (2).

7. The system for recovering low-temperature nitrogen from an atmospheric pressure liquid nitrogen storage tank according to claim 6, characterized in that: An emergency shut-off valve is installed at the inlet end of the delivery pipeline (4), and the emergency shut-off valve is linked to the low-temperature booster (2).

8. The system for recovering low-temperature nitrogen from an atmospheric pressure liquid nitrogen storage tank according to claim 7, characterized in that: An online trace oxygen analyzer is also installed on the pipeline between the liquid nitrogen storage tank (1) and the cryogenic booster (2), and the online trace oxygen analyzer is linked to the emergency shut-off valve.

9. The system for recovering low-temperature nitrogen from an atmospheric pressure liquid nitrogen storage tank according to claim 6, characterized in that: A low-pressure check valve is also installed on the pipeline between the liquid nitrogen storage tank (1) and the low-temperature booster (2).

10. The low-temperature nitrogen cooling capacity recovery system for emptying a normal-pressure liquid nitrogen storage tank according to claim 2 or 3, characterized in that: The sealing gas of the low-temperature booster (2) is high-purity nitrogen.

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