Purging system and purging method adopting mobile energy storage and liquid nitrogen vaporization

Abstract

The purging system comprises a liquid nitrogen vacuum storage tank, a water bath type vaporizer, a liquid nitrogen tank car and a movable energy storage device, the liquid nitrogen vacuum storage tank is connected with a liquid nitrogen inlet of the water bath type vaporizer through a liquid nitrogen output pipeline, and a liquid nitrogen outlet valve is arranged on the liquid nitrogen output pipeline; the movable energy storage device is used for supplying steam to the water bath type vaporizer and connected with the steam supply pipe, the steam supply pipe is connected with a steam inlet of the water bath type vaporizer, a steam manual stop valve is arranged on the steam supply pipe, and a nitrogen outlet of the water bath type vaporizer is connected with the nitrogen output pipeline. The nitrogen output pipeline is connected with a medium-pressure nitrogen pipeline, a nitrogen stop valve and a medium-pressure nitrogen boundary area valve are arranged on the medium-pressure nitrogen pipeline, and the medium-pressure nitrogen pipeline is connected with an interconnection pipeline. The invention has the advantages of reduced cost, high cleanliness, small arrangement space, less control nodes, easy control of the flow pressure of vaporized nitrogen, and safe and simple operation.

Description

Technical Field

[0001] This invention relates to the field of nitrogen purging technology, specifically to a purging system and method employing mobile energy storage and liquid nitrogen vaporization. Background Technology

[0002] Because the nitrogen interconnection pipeline lacks the necessary conditions for pipeline ventilation due to land acquisition issues for municipal public utility tunnels, in order to ensure the nitrogen needs for purging some of BASF's process pipelines in the early stages, the existing method used is as follows: Figure 1 The temporary liquid nitrogen vaporization supply method shown is used to ensure supply. There are three existing liquid nitrogen self-pressurizing vaporizers: Self-pressurizing vaporizer A, Self-pressurizing vaporizer B, and Self-pressurizing vaporizer C. Self-pressurizing vaporizers B and C are used as ambient temperature vaporizers for liquid nitrogen. New equipment such as self-regulating pressure valves, cryogenic valves, and instrument monitoring devices are added. Liquid nitrogen in the vacuum tank is pressurized and vaporized into nitrogen gas, which is then piped to BASF. However, the pipeline purging line is 2.9 kilometers long with many vertical tension bends, making purging difficult. There is no on-site gas source, and the pipeline cleanliness requirements are high for use with sealed nitrogen. Furthermore, the internal corrosion of 300 meters of pipeline within the company is unknown, which will significantly increase the difficulty of pipeline purging. To solve these problems, a combination of 10 air compressors is currently used to increase the nitrogen pressure to meet the demand. However, this purging method requires a large amount of electricity, resulting in high costs, and the arrangement of 10 air compressors requires a large space, which is difficult to accommodate on-site. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a purging system and purging method that uses mobile energy storage and liquid nitrogen vaporization, which can reduce costs, achieve high cleanliness, require small layout space, have fewer control nodes, make it easy to control the flow and pressure of vaporized nitrogen, and is safe and easy to operate, meeting the requirements for purging use.

[0004] This invention is achieved through the following technical solution: a purging system employing mobile energy storage and liquid nitrogen vaporization, comprising a liquid nitrogen vacuum storage tank, a water bath vaporizer, a liquid nitrogen tank truck, and a mobile energy storage device. The liquid nitrogen vacuum storage tank is connected to the liquid nitrogen inlet of the water bath vaporizer via a liquid nitrogen output pipeline. A liquid nitrogen outlet valve is installed on the liquid nitrogen output pipeline. The liquid nitrogen tank truck is used to replenish liquid nitrogen to the liquid nitrogen vacuum storage tank. The mobile energy storage device is used to supply steam to the water bath vaporizer. The mobile energy storage device is connected to a steam supply pipeline via a temporary valve pipe. The steam supply pipeline is connected to the steam inlet of the water bath vaporizer. A manual steam shut-off valve is installed on the steam supply pipeline. The nitrogen outlet of the water bath vaporizer is connected to a nitrogen output pipeline. The nitrogen output pipeline is connected to a medium-pressure nitrogen pipeline. A nitrogen shut-off valve and a medium-pressure nitrogen boundary valve are installed on the medium-pressure nitrogen pipeline. The medium-pressure nitrogen pipeline is connected to an interconnecting pipeline extending from outside the plant area to inside the plant area.

[0005] Furthermore: the medium-pressure nitrogen pipeline is connected to a low-pressure nitrogen pipeline via a connecting valve, and the low-pressure nitrogen pipeline is connected to the interconnecting pipeline.

[0006] Furthermore: the liquid nitrogen vacuum storage tank is provided with a liquid nitrogen filling port, and the liquid nitrogen filling port is provided with a liquid nitrogen filling valve, through which the liquid nitrogen tanker replenishes liquid nitrogen to the liquid nitrogen vacuum storage tank.

[0007] Furthermore: the insulation layer of the water bath vaporizer is connected to a local thermometer.

[0008] Furthermore, a total of three mobile energy storage devices are provided, and each of the three mobile energy storage devices can supply steam to the water bath vaporizer independently or simultaneously.

[0009] Furthermore, the water bath vaporizer is connected to a self-pressurizing vaporizer A.

[0010] Furthermore, the vaporization flow rate of the water bath vaporizer is 28,000 cubic meters per hour.

[0011] Furthermore, the water bath vaporizer is connected to a water pump.

[0012] The purging method employing mobile energy storage and liquid nitrogen vaporization includes the following steps:

[0013] S1. Fill the liquid nitrogen vacuum storage tank with liquid nitrogen using a mobile tanker truck and confirm that the liquid nitrogen content in the liquid nitrogen vacuum storage tank is sufficient.

[0014] S2. Connect the mobile energy storage device to the steam supply pipe through a temporary valve pipe, and set the steam outlet pressure of the mobile energy storage device to 0.5MPa-0.6MPa and the temperature to 158℃;

[0015] S3. Open the steam supply valve of the mobile energy storage device to preheat the pipes, and open the manual steam shut-off valve to start preheating the water bath vaporizer to about 60°C.

[0016] S4. After confirming that the water bath vaporizer has finished preheating, open the liquid nitrogen outlet valve to introduce the liquid nitrogen in the liquid nitrogen vacuum storage tank into the water bath vaporizer for heat exchange and vaporization with the steam.

[0017] S5. Gradually open the liquid nitrogen outlet valve to increase the flow rate of vaporized liquid nitrogen, and simultaneously control the steam outlet pressure of the mobile energy storage device to ensure that all liquid nitrogen is vaporized;

[0018] S6. When both the local thermometer and the local pressure gauge meet the standards, open the nitrogen shut-off valve and the medium-pressure nitrogen boundary valve to supply nitrogen and purge the interconnected pipelines.

[0019] Further: During the process of completely vaporizing liquid nitrogen as described in step S5, the pressure of the liquid nitrogen vacuum storage tank is monitored. When the pressure of the liquid nitrogen vacuum storage tank is lower than the set value, the self-pressurizing vaporizer A is activated to pressurize the liquid nitrogen vacuum storage tank. During the process of purging the interconnected pipeline as described in step S6, the steam manual shut-off valve and the liquid nitrogen outlet valve are adjusted according to the readings of the local thermometer and the local pressure machine.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention utilizes a pre-production water bath vaporizer combined with a mobile energy storage device to vaporize liquid nitrogen in a liquid nitrogen vacuum storage tank. This solves the problem of lacking on-site gas sources for purging medium-pressure nitrogen pipelines and interconnected pipelines. Furthermore, relying on a self-pressurizing vaporizer A and a self-regulating pressure stabilizer, the purging flow rate of the vaporized liquid nitrogen is guaranteed, allowing the vaporized nitrogen to overcome the resistance losses caused by the 2.9 km pipeline and tension bends. Liquid nitrogen is replenished to the liquid nitrogen vacuum storage tank via liquid nitrogen tank trucks, ensuring the purity of the liquid nitrogen source. The liquid nitrogen replenished by the tank trucks is the same medium transported during the later formal operation of the interconnected pipelines, meeting the nitrogen quality requirements before the formal operation of the interconnected pipelines. Additionally... By using mobile energy storage and liquid nitrogen vaporization instead of combined air compressors, a more feasible and better option is provided for projects where temporary power supply and space for air compressor placement cannot be reserved during peak periods. This also avoids the possibility of air compressor failure and eliminates the need for parallel pipeline fabrication, leak detection, pressure testing, and air compressor equipment commissioning, reducing workload and significantly minimizing the investment of manpower and resources. It achieves the effect of easy control of vaporized nitrogen flow and pressure, smaller layout space, fewer control nodes, safe and simple operation, and high system reliability. It also provides a clean air source for purging 300 meters of pipelines within the company's plant area, providing conditions for rectifying corrosion caused by water pressure testing in the plant's pipelines. Attached Figure Description

[0022] Figure 1 Flowchart of the existing temporary liquid nitrogen vaporization supply process;

[0023] Figure 2 This is a connection diagram of the liquid nitrogen vacuum storage tank and water bath vaporizer of the present invention;

[0024] Figure 3 This is a schematic diagram of the structure of the water bath vaporizer of the present invention;

[0025] Figure 4 This is a schematic diagram showing the connection between the medium-pressure nitrogen pipeline and the low-pressure nitrogen pipeline of the present invention;

[0026] Figure 5 This is a schematic diagram of the interconnected pipeline structure of the present invention.

[0027] Explanation of reference numerals in the attached diagram: 1-Liquid nitrogen vacuum storage tank, 2-Water bath vaporizer, 3-Liquid nitrogen output pipeline, 4-Liquid nitrogen inlet, 5-Liquid nitrogen outlet valve, 6-Temporary valve pipe, 7-Steam supply pipe, 8-Steam inlet, 9-Manual steam shut-off valve, 10-Nitrogen outlet, 11-Nitrogen output pipeline, 12-Medium-pressure nitrogen pipeline, 13-Nitrogen shut-off valve, 14-Medium-pressure nitrogen boundary valve, 15-Interconnecting pipeline, 16-Connecting valve, 17-Low-pressure nitrogen pipeline, 18-Liquid nitrogen filling port, 19-Liquid nitrogen filling valve, 20-Local thermometer, 21-Self-pressurizing vaporizer A, 22-Water pump, 23-Self-pressurizing vaporizer B, 24-Self-pressurizing vaporizer C, 25-Self-regulating pressure stabilizing valve, 26-External pipe gallery section of air separation station, 27-Entryway of enterprise plant area, 28-Internal section of enterprise plant area. Detailed Implementation

[0028] The present invention will now be described in detail with reference to embodiments.

[0029] Reference Figures 2 to 5 The purging system employs mobile energy storage and liquid nitrogen vaporization, including a liquid nitrogen vacuum storage tank 1, a water bath vaporizer 2, a liquid nitrogen tanker, and a mobile energy storage device. The liquid nitrogen vacuum storage tank 1 is connected to the liquid nitrogen inlet 4 of the water bath vaporizer 2 via a liquid nitrogen output pipeline 3. A liquid nitrogen outlet valve 5 is installed on the liquid nitrogen output pipeline 3. The liquid nitrogen tanker is used to replenish liquid nitrogen to the liquid nitrogen vacuum storage tank 1. The mobile energy storage device is used to supply steam to the water bath vaporizer 2. The mobile energy storage device is connected to the steam supply system via a temporary valve pipe 6. Steam supply pipe 7 is connected to the steam inlet 8 of water bath vaporizer 2. Steam supply pipe 7 is equipped with a manual steam shut-off valve 9. Nitrogen outlet 10 of water bath vaporizer 2 is connected to nitrogen output pipe 11. Nitrogen output pipe 11 is connected to medium-pressure nitrogen pipeline 12. Medium-pressure nitrogen pipeline 12 is equipped with nitrogen shut-off valve 13 and medium-pressure nitrogen boundary valve 14. Medium-pressure nitrogen pipeline 12 is connected to interconnection pipeline 15. Interconnection pipeline 15 extends from outside the plant area to inside the plant area.

[0030] The interconnected pipeline is divided into three sections: 15 sections outside the air separation station, 26 sections outside the factory gate, 27 sections inside the factory area, and 28 sections inside the factory area.

[0031] Both liquid nitrogen tank trucks and mobile energy storage devices are existing products.

[0032] The medium-pressure nitrogen pipeline 12 is connected to the low-pressure nitrogen pipeline 17 via the connecting valve 16, and the low-pressure nitrogen pipeline 17 is connected to the interconnecting pipeline 15.

[0033] When the medium-pressure nitrogen pipeline 12 needs to suspend gas supply during construction, in order to ensure seamless gas switching for the enterprise, a connecting valve 16 is added between the medium-pressure nitrogen pipeline 12 and the low-pressure nitrogen pipeline 17 to conduct joint nitrogen supply for the enterprise. The low-pressure nitrogen pipeline 17 also adopts mobile energy storage and liquid nitrogen vaporization purging methods.

[0034] The liquid nitrogen vacuum storage tank 1 is equipped with a liquid nitrogen filling port 18, and a liquid nitrogen filling valve 19 is installed on the liquid nitrogen filling port 18. The liquid nitrogen tank truck replenishes liquid nitrogen to the liquid nitrogen vacuum storage tank 1 through the liquid nitrogen filling port 18.

[0035] The insulation layer of the water bath vaporizer 2 is connected to the local thermometer 20.

[0036] The temperature of the vaporized nitrogen is monitored by a local thermometer 20 to prevent liquid purging during vaporization. Additionally, a digital thermometer is installed on the insulation layer of the water bath vaporizer 2 before insulation is applied to monitor the water temperature and prevent the tank from freezing due to excessively low temperatures.

[0037] Three mobile energy storage devices are installed, and each device can supply steam to the water bath vaporizer 2 independently or simultaneously.

[0038] Each mobile energy storage device can provide 2t (0.5-0.6MPa, 158℃) of heat to the water bath vaporizer 2. When providing heat, the mobile energy storage devices should supply energy one by one. When the mobile energy storage devices need to switch or supply energy in parallel, the outlet pressure of the mobile energy storage devices should be set reasonably to prevent gas leakage.

[0039] The water bath vaporizer 2 is connected to a self-pressurizing vaporizer A21.

[0040] The vaporization flow rate of liquid nitrogen in water bath vaporizer 2 is 28,000 cubic meters per hour.

[0041] The water bath vaporizer 2 is connected to a water pump 22.

[0042] This invention employs mobile energy storage and liquid nitrogen vaporization to replace the combined air compressor purging system. When the interconnected pipeline 15 lacks normal ventilation, a backup liquid nitrogen vaporization system (not yet operational) combined with a commercially available mobile energy storage device vaporizes the liquid nitrogen in the liquid nitrogen vacuum storage tank 1 via a water bath vaporizer 2. To meet the specific pipeline purging conditions, the self-pressurizing liquid nitrogen vaporizer A21 and the newly added self-regulating pressure valve 25 ensure the purging flow rate of the vaporized liquid nitrogen. This solves the problem of lacking a local gas source for purging the medium-pressure nitrogen pipeline 12. The self-pressurizing vaporizer A21 in the liquid nitrogen vacuum storage tank 1 ensures the pressure and flow rate of the vaporized liquid nitrogen used for purging, allowing the vaporized nitrogen to overcome the resistance losses caused by the 2.9 km pipeline and tension bends. This ensures efficient pipeline cleaning. Simultaneously, liquid nitrogen is transported to the company's air separation site via liquid nitrogen tank trucks and injected into the liquid nitrogen vacuum storage tank 1. The purity of the liquid nitrogen source guarantees the cleanliness of the vaporized nitrogen, with a purity of 99.999%, meeting the company's high nitrogen quality requirements before the formal commissioning of the interconnected pipeline 15. Furthermore, it effectively reduces purging costs, providing a more feasible and better option for projects where temporary power supply and space for air compressor installation cannot be reserved during peak periods. The alternative solution also avoids the possibility of air compressor failure and reduces workload, such as eliminating the need for parallel pipeline fabrication, leak detection, pressure testing, and air compressor equipment commissioning, significantly reducing the investment of manpower and resources.

[0043] The purging method employing mobile energy storage and liquid nitrogen vaporization includes the following steps:

[0044] S1. Fill the liquid nitrogen vacuum storage tank 1 with liquid nitrogen using a mobile tanker truck, and confirm that the liquid nitrogen content in the liquid nitrogen vacuum storage tank 1 is sufficient.

[0045] S2. Connect the mobile energy storage device to the steam supply pipe 7 through the temporary valve pipe 6, and set the steam outlet pressure of the mobile energy storage device to 0.5MPa-0.6MPa and the temperature to 158℃.

[0046] S3. Open the steam supply valve of the mobile energy storage device to preheat the pipes, and open the manual steam shut-off valve 9 to start preheating the water bath vaporizer 2 to about 60°C.

[0047] S4. After confirming that the water bath vaporizer 2 has been preheated, open the liquid nitrogen outlet valve 5 to introduce the liquid nitrogen in the liquid nitrogen vacuum storage tank 1 into the water bath vaporizer 2 for heat exchange and vaporization with steam.

[0048] S5. Gradually open the liquid nitrogen outlet valve 5 to increase the flow rate of vaporized liquid nitrogen, and simultaneously control the steam outlet pressure of the mobile energy storage device to ensure that all liquid nitrogen is vaporized.

[0049] During the complete vaporization of liquid nitrogen described in step S5, the pressure of the liquid nitrogen vacuum storage tank 1 is monitored. When the pressure of the liquid nitrogen vacuum storage tank 1 is lower than the set value, the self-pressurizing vaporizer A21 is activated to pressurize the liquid nitrogen vacuum storage tank 1. The set value is approximately 0.5 MPa.

[0050] S6. When both the local thermometer 20 and the local pressure gauge meet the standards, open the nitrogen shut-off valve 13 and the medium-pressure nitrogen boundary valve 14 to supply nitrogen and purge the interconnecting pipeline 15.

[0051] During the purging process of the interconnected pipeline 15 described in step S6, the steam manual shut-off valve 9 and the liquid nitrogen outlet valve 5 are adjusted according to the readings of the local thermometer 20 and the local pressure machine.

[0052] The steam flow rate supplied to the water bath vaporizer 2 is controlled by adjusting the manual steam shut-off valve 9, and the liquid nitrogen quantity is controlled by adjusting the liquid nitrogen outlet valve 5, thereby adjusting the vaporized liquid nitrogen flow rate and ensuring the purging quality.

[0053] In this embodiment, the purging nitrogen gas flow rate is 36270 Nm³. 3 The output pressure is 0.28 MPa.G, the output temperature is 41.92℃, and the purging velocity reaches 33 m / s.

[0054] The purging frequency is once a day, and each purging time is 45 minutes. During the purging process, a wooden hammer is used to tap the bottom tension bend along the pipe gallery to remove surface corrosion through vibration.

[0055] Pipeline purging process: High-volume purging is used, followed by intermittent gas supply and desiccation to achieve optimal purging results. After 6 purging cycles, target testing is conducted; the passing standard is the absence of rust and debris.

[0056] The above detailed description is a specific description of feasible embodiments of the present invention. These embodiments are not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included in the patent scope of this case.

Claims

1. The purge system adopts mobile energy storage and liquid nitrogen vaporization, which is characterized by: It includes a liquid nitrogen vacuum storage tank, a water bath vaporizer, a liquid nitrogen tank truck, and a mobile energy storage device. The liquid nitrogen vacuum storage tank is connected to the liquid nitrogen inlet of the water bath vaporizer through a liquid nitrogen output pipeline. A liquid nitrogen outlet valve is provided on the liquid nitrogen output pipeline. The liquid nitrogen tank truck is used to replenish liquid nitrogen to the liquid nitrogen vacuum storage tank. The mobile energy storage device is used to supply steam to the water bath vaporizer. The mobile energy storage device is connected to a steam supply pipe through a temporary valve pipe. The steam supply pipe is connected to the steam inlet of the water bath vaporizer. A steam manual stop valve is provided on the steam supply pipe. The nitrogen outlet of the water bath vaporizer is connected to a nitrogen output pipeline. The nitrogen output pipeline is connected to a medium-pressure nitrogen pipeline. A nitrogen stop valve and a medium-pressure nitrogen boundary valve are provided on the medium-pressure nitrogen pipeline. The medium-pressure nitrogen pipeline is connected to an interconnected pipeline, and the interconnected pipeline extends from outside the factory to inside the factory.

2. The purge system using mobile energy storage and liquid nitrogen vaporization according to claim 1, characterized in that: The medium-pressure nitrogen pipeline is connected to a low-pressure nitrogen pipeline via a connecting valve, and the low-pressure nitrogen pipeline is connected to the interconnected pipeline.

3. The purge system using mobile energy storage and liquid nitrogen vaporization according to claim 1 is characterized in that: The liquid nitrogen vacuum storage tank is provided with a liquid nitrogen filling port, and the liquid nitrogen filling port is provided with a liquid nitrogen filling valve, and the liquid nitrogen tank truck replenishes liquid nitrogen to the liquid nitrogen vacuum storage tank through the liquid nitrogen filling port.

4. The purge system using mobile energy storage and liquid nitrogen vaporization according to claim 1, characterized in that: The insulation layer of the water bath type vaporizer is connected to an on-site thermometer.

5. The purging system using mobile energy storage and liquid nitrogen vaporization according to claim 3 is characterized in that: A total of three mobile energy storage devices are provided, and the three mobile energy storage devices can supply steam to the water bath vaporizer independently or simultaneously.

6. The purging system using mobile energy storage and liquid nitrogen vaporization according to claim 5 is characterized in that: The water bath vaporizer is connected to a self-pressurizing vaporizer A.

7. The purging system using mobile energy storage and liquid nitrogen vaporization according to claim 6 is characterized in that: The vaporized liquid nitrogen flow rate of the water bath vaporizer is 28,000 cubic meters per hour.

8. The purging system using mobile energy storage and liquid nitrogen vaporization according to claim 7 is characterized in that: The water bath vaporizer is connected with a water pump.

9. The purging method using mobile energy storage and liquid nitrogen vaporization is characterized by: The following steps are included: S1. Fill the liquid nitrogen vacuum storage tank with liquid nitrogen by using a mobile tank truck and confirm that the liquid nitrogen content in the liquid nitrogen vacuum storage tank is sufficient; S2. Connect the mobile energy storage device to the steam supply pipe through a temporary valve pipe, and set the steam outlet pressure of the mobile energy storage device to 0.5MPa-0.6MPa and the temperature to 158°C; S3. Open the steam supply valve of the mobile energy storage device to preheat the pipe, and open the steam manual stop valve to start preheating the water bath vaporizer to about 60°C; S4. After confirming that the water bath vaporizer is preheated, open the liquid nitrogen outlet valve, and introduce the liquid nitrogen in the liquid nitrogen vacuum storage tank into the water bath vaporizer to perform heat exchange and vaporization with the steam; S5. Gradually open the liquid nitrogen outlet valve to increase the flow rate of vaporized liquid nitrogen, and simultaneously control the steam outlet pressure of the mobile energy storage device to ensure that all the liquid nitrogen is vaporized; S6. When the local thermometer and local pressure gauge are up to standard, open the nitrogen shut-off valve and the medium-pressure nitrogen boundary valve to transport nitrogen and purge the interconnected pipelines.

10. The purging method using mobile energy storage and liquid nitrogen vaporization according to claim 9, characterized in that: In the process of vaporizing all the liquid nitrogen in step S5, the pressure of the liquid nitrogen vacuum storage tank is monitored. When the pressure of the liquid nitrogen vacuum storage tank is lower than the set value, the self-pressurizing vaporizer A is put into use to increase the pressure of the liquid nitrogen vacuum storage tank. In the process of purging the interconnected pipeline in step S6, the steam manual stop valve and the liquid nitrogen outlet valve are adjusted according to the readings of the local thermometer and the local press.

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