Normal pressure liquid nitrogen storage tank venting low temperature nitrogen gas cooling capacity recovery system

Abstract

The application discloses a kind of normal-pressure liquid nitrogen storage tank venting low-temperature nitrogen cold quantity recovery system, it is related to cryogenic technology field, including liquid nitrogen storage tank, spare regulating valve on the liquid nitrogen storage tank is connected with cryogenic booster by pipeline, the outlet end of cryogenic booster is connected with vacuum insulation pipeline, vacuum insulation pipeline outlet end is connected with venting pipeline and the conveying pipeline for being connected with nitrogen pipeline in air separation device, and the output end of nitrogen pipeline is also connected with heat exchanger. By vacuum insulation pipeline, conveying pipeline, the low-temperature nitrogen after pressurization is sent to nitrogen pipeline in air separation device, to merge with the nitrogen produced by air separation device, then enter heat exchanger, and carry out heat exchange with the air of positive flow in heat exchanger, after reheat, exit cold box, to achieve the purpose of recovering cold quantity.

Description

Technical Field

[0001] This invention relates to the field of cryogenic technology, and more specifically, to a system for recovering cryogenic nitrogen cooling capacity by venting an atmospheric pressure liquid nitrogen storage tank. Background Technology

[0002] The working pressure of the gas phase of the atmospheric pressure standby regulating valve is usually controlled at around 15 kPa. The pressure of the evaporated low-temperature (-195.8℃) nitrogen is too low. The pressure of the nitrogen pipeline in the air separation unit is around 40 kPa. This means that the low-temperature nitrogen evaporated from the liquid nitrogen storage tank cannot be directly fed into the nitrogen pipeline in the air separation unit for mixing. As projects continue to be built, there are more and more large atmospheric pressure low-temperature liquid storage tanks. Since the liquid nitrogen produced by the air separation and liquefaction units has no subcooling, 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 an efficient way to utilize this, resulting in a large loss of cooling capacity and nitrogen. Summary of the Invention

[0003] The purpose of this invention is to provide a low-temperature nitrogen cooling energy recovery system for venting liquid nitrogen storage tanks at atmospheric pressure, which can effectively recover the vented cooling energy and nitrogen, avoid waste of cooling energy, and greatly save enterprise costs.

[0004] To achieve the objective of this invention, the technical solution adopted is as follows: a cryogenic nitrogen energy recovery system for venting liquid nitrogen storage tank at atmospheric pressure, comprising a liquid nitrogen storage tank, a venting valve and a standby regulating valve on the liquid nitrogen storage tank, the standby regulating valve on the liquid nitrogen storage tank being connected to a cryogenic booster via a pipeline, the outlet end of the cryogenic booster being connected to a vacuum insulation pipeline, the outlet end of the vacuum insulation pipeline being connected to a venting pipeline and a conveying pipeline for connecting to the nitrogen pipeline in the air separation unit, and the output end of the nitrogen pipeline being connected to a heat exchanger.

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

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

[0007] Furthermore, the outlet pressure of the cryogenic booster is 45 kPa to 55 kPa.

[0008] Furthermore, a regulating valve is also installed between the cryogenic booster and the spare 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 conveying pipeline, and the emergency shut-off valve is linked to the cryogenic 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 also installed on the pipeline between the liquid nitrogen storage tank and the cryogenic booster.

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

[0014] The beneficial effects of this invention are:

[0015] This invention pressurizes the low-temperature nitrogen discharged from the atmospheric pressure standby regulating valve, allowing the pressurized gas to enter the nitrogen pipeline in the air separation unit for mixing. After mixing, the gas is sent to a heat exchanger for reheating and reuse, or after reheating, it is sent to a piston nitrogen compressor for use. This effectively recovers the vented cold energy and nitrogen, avoids waste of cold energy, and greatly saves enterprise costs. Attached Figure Description

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

[0017] Figure 1 This is a flowchart of the low-temperature nitrogen cooling capacity recovery system for venting an atmospheric pressure liquid nitrogen storage tank provided by the present invention.

[0018] The attached diagram shows the markings and corresponding component names:

[0019] 1. Liquid nitrogen storage tank; 2. Cryogenic booster; 3. Vacuum insulated pipeline; 4. Conveying pipeline; 5. Liquid nitrogen vaporization backup system storage tank; 6. Vaporizer; 7. Piston nitrogen compressor; 8. Parallel pipeline; 9. Vaporization pipeline; 10. Low-pressure nitrogen pipeline; 11. Gas supply pipeline one; 12. Gas supply pipeline two; 13. Vent pipeline; 14. Air separation unit; 15. Nitrogen pipeline; 16. Heat exchanger. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] like Figure 1 As shown, the present invention provides a cryogenic nitrogen energy recovery system for venting a liquid nitrogen storage tank at atmospheric pressure. The system includes a liquid nitrogen storage tank 1 for storing liquid nitrogen. The liquid nitrogen storage tank 1 has a backup regulating valve and a vent valve. The vent valve ensures the safety of the liquid nitrogen storage tank 1. The backup regulating valve on the liquid nitrogen storage tank 1 is connected to a cryogenic booster 2 via a pipeline. The cryogenic booster 2 pressurizes the nitrogen gas drawn from the backup regulating valve on the liquid nitrogen storage tank 1. The outlet end of the cryogenic booster 2 is connected to a vacuum insulated pipe 3. The vacuum insulated pipe 3 can be made of vacuum tubing or stainless steel. The insulation method of bare pipe and aluminum pipe is adopted. The outlet end of vacuum insulation pipe 3 is connected to vent pipe 13 and conveying pipe 4 for connecting to nitrogen pipe 15 in air separation unit 14. The output end of nitrogen pipe 15 is also connected to heat exchanger 16, so that nitrogen gas pressurized by low temperature booster 2 can be sent into nitrogen pipe 15 in air separation unit 14, merge with nitrogen gas generated by air separation unit 14, and after mixing, be sent into heat exchanger 16 to exchange heat with the positive flow air in heat exchanger 16. After reheating, it exits the cold box, thereby achieving the purpose of recovering cold energy and nitrogen gas.

[0023] The invention also includes a liquid nitrogen vaporization backup system storage tank 5, a vaporizer 6, and a piston nitrogen compressor 7 connected in sequence. The vaporizer 6 is an air-bath type vaporizer, used to reheat the nitrogen gas pressurized by the cryogenic booster 2. The piston nitrogen compressor 7 is used to compress the reheated nitrogen gas to meet user needs. A parallel pipe 8 is also connected between the inlet of the vaporizer 6 and the vacuum insulation pipe 3, allowing the nitrogen gas pressurized by the cryogenic booster 2 to be fed into the vaporizer 6 for reheating via the parallel pipe 8. The reheated nitrogen gas can be sent to the piston nitrogen compressor 7 for compression. At the same time, the inlet of the piston nitrogen compressor 7 is equipped with a low-pressure nitrogen pipeline 10 connected to a heat exchanger 16, so that the nitrogen gas pressurized by the cryogenic booster 2 can be sent to the nitrogen pipeline 15 of the air separation unit 14, where it will merge with the nitrogen gas produced by the air separation unit 14. After mixing, it will be sent to the heat exchanger 16 to exchange heat with the positive flow air in the heat exchanger 16, so that the nitrogen gas 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 vaporization pipe 9, and the outlet of the piston nitrogen compressor 7 is also equipped with a gas supply pipe 11 for connection to the gas supply equipment. The outlet end of the vaporization pipe 9 is connected in parallel to the gas supply pipe 11, so that part of the nitrogen gas reheated by the vaporizer 6 can enter the piston nitrogen compressor 7 for compression, while the other part of the nitrogen gas reheated by the vaporizer 6 can be sent through the vaporization pipe 9 into the gas supply pipe 11 to mix with the nitrogen gas compressed by the piston nitrogen compressor 7, and finally pass through the gas supply pipe 11. The system supplies gas to users; at the same time, the nitrogen gas is pressurized by the low-temperature booster 2 and sent to the nitrogen pipeline 15 of the air separation unit 14 for mixing. 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. Another part of the nitrogen gas, after being reheated by the vaporizer 6, can be sent to the gas supply pipeline 11 through the vaporization pipeline 9 to mix with the nitrogen gas compressed by the piston nitrogen compressor 7. Finally, it can also be supplied to users through the gas supply pipeline 11, realizing the recovery and use of cold energy.

[0025] The outlet of the piston nitrogen compressor 7 in the recovery system is also equipped with a second gas supply pipe 12 for connection with the liquefaction unit or filling system. This allows the nitrogen gas reheated by the vaporizer 6 to be sent through the vaporization pipe 9 into the first gas supply pipe 11 to mix with the nitrogen gas compressed by the piston nitrogen compressor 7. Alternatively, it can be directly supplied to the liquefaction unit or filling system through the gas supply pipe to meet the user's needs.

[0026] In this invention, the outlet pressure of the cryogenic booster 2 is 45 kPa to 55 kPa. Since the gas phase working pressure of the liquid nitrogen storage tank 1 is typically controlled at around 15 kPa, 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 generated nitrogen, the cryogenic booster 2 can boost the nitrogen gas from approximately 15 kPa to 45 kPa to 55 kPa. This ensures that the gas phase in the liquid nitrogen storage tank 1 has sufficient pressure to enter the nitrogen pipeline 15 in the air separation unit 14, and after mixing with the nitrogen generated by the air separation unit 14, it enters the heat exchanger 16. Preferably, the outlet pressure of the cryogenic booster 2 is 50 kPa; the outlet pressure of the piston nitrogen compressor 7 is 0.65 MPa.

[0027] To prevent the pressure of liquid nitrogen storage tank 1 from dropping to negative pressure under the suction of cryogenic booster 2, a regulating valve is installed in front of cryogenic booster 2 to automatically regulate the pressure of liquid nitrogen storage tank 1. Specifically, the valve opens wider when the pressure of liquid nitrogen storage tank 1 increases and closes narrower when the pressure of liquid nitrogen storage tank 1 decreases.

[0028] To prevent overpressure caused by nitrogen gas at a pressure of approximately 40 kPa flowing back into the liquid nitrogen storage tank 1 through the pipeline when the cryogenic booster 2 suddenly stops during operation, 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 interlocked and closed.

[0029] To prevent air from entering the pipelines of this recovery system and causing contamination, the cryogenic booster 2 uses high-purity nitrogen as the sealing gas. Simultaneously, an online trace oxygen analyzer is installed on the pipeline between the liquid nitrogen storage tank 1 and the cryogenic booster 2. The online trace oxygen analyzer continuously monitors the oxygen content in the pipeline and alarms when the oxygen content exceeds the standard. Furthermore, 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 excessive oxygen content, the low-pressure check valve and the emergency shut-off valve close, and the cryogenic booster 2 stops.

[0030] When this recycling system is in operation:

[0031] Operating mode 1: The nitrogen gas in the liquid nitrogen storage tank 1 is pressurized by the cryogenic booster 2 and then sent to the nitrogen pipeline 15 of the air separation unit 14 through the delivery pipeline 4. It is mixed with the nitrogen gas generated by the air separation unit 14 and then sent to the heat exchanger 16 to exchange heat with the positive flow air in the heat exchanger 16. Finally, it is sent to the piston nitrogen compressor 7 to be compressed to 0.65MPa and finally delivered to the user through the gas supply pipeline 11.

[0032] Operating mode 2: The nitrogen in the liquid nitrogen storage tank 1 is pressurized by the cryogenic booster 2 and then sent to the vaporizer 6 through the parallel pipeline 8 for reheating. The reheated nitrogen is then sent to the piston nitrogen compressor 7 and compressed to 0.65MPa. Finally, it is delivered to the user through the gas supply pipeline 11.

[0033] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0034] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0035] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A cryogenic nitrogen cooling capacity recovery system for venting liquid nitrogen storage tanks at atmospheric pressure, characterized in that, The system includes a liquid nitrogen storage tank (1), which has a vent valve and a standby regulating valve. The standby regulating valve on the liquid nitrogen storage tank (1) is connected to a cryogenic booster (2) via a pipeline. The outlet end of the cryogenic booster (2) is connected to a vacuum insulation pipeline (3). The outlet end of the vacuum insulation pipeline (3) is connected to a vent pipeline (13) and a conveying pipeline (4) for connecting to the nitrogen pipeline (15) in the air separation unit (14). The outlet end of the nitrogen pipeline (15) is also connected to a heat exchanger (16). The system also includes liquid nitrogen in sequence. The system includes a gasification backup storage tank (5), a vaporizer (6), and a piston nitrogen compressor (7). The inlet of the vaporizer (6) is connected to the vacuum insulation pipe (3) via a parallel pipe (8). The outlet of the vaporizer (6) is also connected to a gasification pipe (9). The inlet of the piston nitrogen compressor (7) is provided with a low-pressure nitrogen pipe (10) connected to the heat exchanger (16). The outlet of the piston nitrogen compressor (7) is also provided with a gas supply pipe (11) for connection to the gas supply equipment. The outlet end of the gasification pipe (9) is connected in parallel to the gas supply pipe (11).

2. The atmospheric pressure liquid nitrogen storage tank venting and cryogenic nitrogen cold energy recovery system according to claim 1, characterized in that, The outlet of the piston nitrogen compressor (7) is also provided with a second gas supply pipe (12) for connection to a liquefaction device or filling system.

3. The atmospheric pressure liquid nitrogen storage tank venting and cryogenic nitrogen cold energy recovery system according to claim 1 or 2, characterized in that, The outlet pressure of the cryogenic booster (2) is 45 kPa to 55 kPa.

4. The atmospheric pressure liquid nitrogen storage tank venting cryogenic nitrogen cold energy recovery system according to claim 1 or 2, characterized in that, A regulating valve is also installed between the cryogenic booster (2) and the standby regulating valve on the liquid nitrogen storage tank (1).

5. The atmospheric pressure liquid nitrogen storage tank venting cryogenic nitrogen cold energy recovery system according to claim 1 or 2, 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).

6. The atmospheric pressure liquid nitrogen storage tank venting and cryogenic nitrogen cooling capacity recovery system according to claim 5, characterized in that, An emergency shut-off valve is installed at the inlet end of the conveying pipeline (4), and the emergency shut-off valve is linked to the cryogenic booster (2).

7. The atmospheric pressure liquid nitrogen storage tank venting cryogenic nitrogen cold energy recovery system according to claim 6, 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.

8. The atmospheric pressure liquid nitrogen storage tank venting cryogenic nitrogen cold energy recovery system according to claim 1 or 2, characterized in that, The sealing gas of the cryogenic booster (2) is high-purity nitrogen.

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