A vent gas recovery system for an air separation liquid nitrogen storage tank

Abstract

The utility model provides a kind of emptying gas recovery system of air separation liquid nitrogen storage tank, including liquid nitrogen storage tank, nitrogen storage tank and air separation cold box, the liquid nitrogen storage tank top is equipped with venting pipe and with the recovery pipe bypassing the venting pipe, the venting pipe free end is equipped with venting valve, the recovery pipe with the nitrogen storage tank lower end intercommunication, the nitrogen storage tank upper end is equipped with the intercommunication pipe of the sealed gas pipeline intercommunication with air separation cold box, the recovery pipe is equipped with first switch valve, the intercommunication pipe is equipped with second switch valve.The utility model can recover the venting nitrogen by setting the nitrogen storage tank intercommunication with liquid nitrogen storage tank, then supply the recovered nitrogen to air separation cold box as sealing gas, realize recycling, and further can realize the effect of energy saving and consumption reduction.

Description

Technical Field

[0001] This utility model relates to the field of air separation equipment, and in particular to an air venting recovery system for an air separation liquid nitrogen storage tank. Background Technology

[0002] In the air separation unit, the liquid storage tank serves as a storage function. When the unit is shut down, the liquid storage tank can also be vaporized into product gas of qualified purity by the liquid vaporizer and supplied to the downstream workshop as a backup system. Due to the loss of cold energy, the liquid will continue to vaporize, and the internal pressure of the storage tank will increase. In order to ensure the pressure of the storage tank, the storage tank needs to be continuously vented by setting a vent valve to stabilize the pressure within the design pressure requirement range.

[0003] Air separation liquid storage tanks contain commonly used gases such as oxygen, nitrogen, and argon. For devices with large liquid production volumes, the venting capacity is very large, which means that the gas is wasted. Utility Model Content

[0004] To address the problem of wasted vented air in existing air-separated liquid nitrogen storage tanks, this invention provides an air venting recovery system for air-separated liquid nitrogen storage tanks that can recycle and reuse the vented air.

[0005] This utility model provides an air venting and recovery system for an air separation liquid nitrogen storage tank, including a liquid nitrogen storage tank, a nitrogen storage tank, and an air separation cold box. The top of the liquid nitrogen storage tank is provided with a venting pipe and a recovery pipe that bypasses the venting pipe. The free end of the venting pipe is provided with a venting valve. The recovery pipe is connected to the lower end of the nitrogen storage tank. The upper end of the nitrogen storage tank is provided with a connecting pipe that is connected to the sealing gas pipeline of the air separation cold box. The recovery pipe is provided with a first switch valve, and the connecting pipe is provided with a second switch valve.

[0006] As a further improvement of this utility model, the lower end of the nitrogen storage tank is provided with an air inlet pipe connected to the recovery pipe, and the air inlet pipe is provided with a first pressure gauge and a temperature sensor.

[0007] As a further improvement of this utility model, the upper end of the nitrogen storage tank is provided with an exhaust pipe connected to the connecting pipe, and the exhaust pipe is provided with a pressure sensor and a gas purity sensor.

[0008] As a further improvement of this utility model, the liquid nitrogen storage tank is provided with an upper liquid inlet pipe and a lower liquid inlet pipe that are connected to the air separation unit.

[0009] As a further improvement of this utility model, the upper liquid inlet pipe is provided with a third switching valve, and the lower liquid inlet pipe is provided with a fourth switching valve.

[0010] As a further improvement of this utility model, a second pressure gauge is provided at one end of the connecting pipe near the air separation cold box.

[0011] As a further improvement of this utility model, the intake pipe and the recovery pipe, as well as the exhaust pipe and the connecting pipe, are all sealed and connected by flanges.

[0012] The beneficial effects of this utility model are: by setting up a nitrogen storage tank connected to the liquid nitrogen storage tank, the vented nitrogen can be recovered, and then the recovered nitrogen can be supplied to the air separation cold box as a sealing gas for reuse, thereby achieving the effect of energy saving and consumption reduction. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the air release and recovery system of an air separation liquid nitrogen storage tank according to the present invention; Figure 2 This is a schematic diagram of the nitrogen storage tank in the air release and recovery system of the air separation liquid nitrogen storage tank of this utility model.

[0014] Attached reference numerals: 1-Liquid nitrogen storage tank; 2-Nitrogen storage tank; 3-Air separation cold box; 4-Vent pipe; 5-Recovery pipe; 6-Vent valve; 7-First switching valve; 8-Second switching valve; 9-Third switching valve; 10-Fourth switching valve; 11-Inlet pipe; 12-Exhaust pipe; 13-Connecting pipe. Detailed Implementation

[0015] In the description of this utility model, it should be understood that if there are descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientation or positional relationship, the orientation description may be based on the orientation or positional relationship shown in the accompanying drawings. This is only for the convenience of describing this utility model and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this utility model.

[0016] In the description of this utility model, if there is a description of quantity, "several" means one or more, "more than" means two or more, "greater than," "less than," "exceeding," etc. are understood to exclude the number itself, while "above," "below," "within," etc. are understood to include the number itself. If there is a description of "first" or "second," it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the order of the indicated technical features.

[0017] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0018] like Figure 1 and Figure 2As shown, this utility model discloses an air venting and recovery system for an air separation liquid nitrogen storage tank, including a liquid nitrogen storage tank 1, a nitrogen storage tank 2, and an air separation cold box 3. The top of the liquid nitrogen storage tank 1 is provided with a venting pipe 4 and a recovery pipe 5 that bypasses the venting pipe 4. The free end of the venting pipe 4 is provided with a venting valve 6. The recovery pipe 5 is connected to the lower end of the nitrogen storage tank 2. The upper end of the nitrogen storage tank 2 is provided with a connecting pipe 13 that is connected to the sealing gas pipeline of the air separation cold box 3. The recovery pipe 5 is provided with a first switching valve 7, and the connecting pipe 13 is provided with a second switching valve 8.

[0019] When the pressure in the liquid storage tank is too high, the nitrogen gas generated in the liquid storage tank can enter the nitrogen storage tank 2 through the recovery pipe 5 and the first switching valve 7. The nitrogen gas in the nitrogen storage tank 2 can be connected to the sealing gas pipeline of the air separation cold box 3 through the connecting pipe 13, so that it can enter the air separation cold box 3 as sealing gas, thereby realizing the recovery and utilization of the vented air. When the nitrogen pressure in the nitrogen storage tank 2 is too high, the excess nitrogen gas in the liquid nitrogen storage tank 1 can be directly vented into the atmosphere through the vent pipe 4 and the vent valve 6.

[0020] The air separation cold box 3 is a large box structure containing various cryogenic equipment (such as heat exchangers, distillation columns, etc.), with an internal temperature that can reach as low as -196℃. The main function of the cold box sealing gas is to form a sealing layer between the inside and outside of the cold box, preventing impurities such as outside air from entering the cold box and preventing the formation of negative pressure inside the cold box. Under the pressure difference between the inside and outside, the cold box body is prone to collapse. During normal operation of the device, it is necessary to fill the cold box with dry inert gas, such as nitrogen or waste nitrogen, to ensure that the pressure inside the cold box is a slight positive pressure, about 200-500 Pa. The pressure of liquid nitrogen storage tank 1 is 15 kPa. It can be adjusted to the design sealing gas pressure of the cold box through a pressure reducing valve, and the gas that has been continuously vented from it is introduced into the cold box, so that the vented gas from liquid nitrogen storage tank 1 can be recovered and utilized.

[0021] In this invention, the nitrogen storage tank 2 has an inlet pipe 11 at its lower end, connected to the recovery pipe 5. The inlet pipe 11 is equipped with a first pressure gauge and a temperature sensor. The nitrogen storage tank 2 has an exhaust pipe 12 at its upper end, connected to the connecting pipe 13. The exhaust pipe 12 is equipped with a pressure sensor and a gas purity sensor. These are used to monitor various parameters of the nitrogen storage tank 2, observe whether the pressure is within the normal design value, and ensure the safety of the equipment.

[0022] In this utility model, the liquid nitrogen storage tank 1 is provided with an upper liquid inlet pipe and a lower liquid inlet pipe that are connected to the air separation unit. The upper liquid inlet pipe is provided with a third switch valve 9, and the lower liquid inlet pipe is provided with a fourth switch valve 10.

[0023] In this invention, a second pressure gauge is provided at one end of the connecting pipe 13 near the air separation cold box 3, which serves as an observation record during on-site inspections to ensure the stability of the device.

[0024] In this invention, the intake pipe 11 and the recovery pipe 5, as well as the exhaust pipe 12 and the connecting pipe 13, are all sealed and connected by flanges. Installation is convenient and quick.

[0025] This invention, by setting up a nitrogen storage tank 2 connected to the liquid nitrogen storage tank 1, can recover the vented nitrogen gas, and then supply the recovered nitrogen gas to the air separation cold box 3 as a sealing gas for reuse, thereby achieving the effect of energy saving and consumption reduction.

[0026] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the protection scope of the present invention.

Claims

1. An air venting recovery system for an air separation liquid nitrogen storage tank, characterized in that: The system includes a liquid nitrogen storage tank, a nitrogen gas storage tank, and an air separation cold box. The liquid nitrogen storage tank is equipped with a vent pipe at the top and a recovery pipe that bypasses the vent pipe. The vent pipe is equipped with a vent valve at its free end. The recovery pipe is connected to the lower end of the nitrogen gas storage tank. The upper end of the nitrogen gas storage tank is equipped with a connecting pipe that is connected to the sealing gas pipeline of the air separation cold box. The recovery pipe is equipped with a first switch valve, and the connecting pipe is equipped with a second switch valve.

2. The venting air recovery system for the air separation liquid nitrogen storage tank according to claim 1, characterized in that: The nitrogen storage tank is provided with an air inlet pipe at the lower end, which is connected to the recovery pipe. The air inlet pipe is equipped with a first pressure gauge and a temperature sensor.

3. The venting air recovery system for the air separation liquid nitrogen storage tank according to claim 2, characterized in that: The nitrogen storage tank is equipped with an exhaust pipe at the upper end that is connected to the connecting pipe. The exhaust pipe is equipped with a pressure sensor and a gas purity sensor.

4. The venting air recovery system for the air separation liquid nitrogen storage tank according to claim 1, characterized in that: The liquid nitrogen storage tank is equipped with an upper inlet pipe and a lower inlet pipe that are connected to the air separation unit.

5. The venting air recovery system for the air separation liquid nitrogen storage tank according to claim 4, characterized in that: The upper inlet pipe is equipped with a third switch valve, and the lower inlet pipe is equipped with a fourth switch valve.

6. The venting air recovery system for the air separation liquid nitrogen storage tank according to claim 1, characterized in that: A second pressure gauge is provided at one end of the connecting pipe near the air separation cold box.

7. The venting air recovery system for the air separation liquid nitrogen storage tank according to claim 3, characterized in that: The intake pipe and the recovery pipe, as well as the exhaust pipe and the connecting pipe, are all sealed together by flanges.

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