Device for preparing high-purity nitrogen by recovering waste nitrogen on upper tower of air separation tower

Abstract

The utility model belongs to the technical field of air separation waste nitrogen utilization, and particularly relates to a device for preparing high-purity nitrogen by recovering waste nitrogen on an upper tower of an air separation tower. According to the device, waste nitrogen at the top of the upper tower of the air separation tower is boosted by the booster device through the waste nitrogen rectifying tower and then fed into the waste nitrogen rectifying tower for rectification, high-purity nitrogen is obtained through rectification and purification in the waste nitrogen rectifying tower, and the boosted nitrogen of the high-purity nitrogen is fed into a 0.7 Mpa nitrogen pipe network to be used as shielding gas and replacement gas of the device; according to the utility model, nitrogen resources in the waste nitrogen are fully utilized, and oxygen and argon in the waste nitrogen are enriched at the bottom of the waste nitrogen rectifying tower and then are conveyed to the upper part of the air separation tower for rectification, so that the recycling of the oxygen and the argon in the waste nitrogen is also realized; the high-purity nitrogen is prepared by purifying the waste nitrogen at the top of the upper tower of the air separation tower, and the waste nitrogen does not need to be purified by a water washing tower and a molecular sieve, so that the production cost is low compared with nitrogen preparation by air.

Description

Technical Field

[0001] The utility model belongs to the technical field of utilization of polluted nitrogen in air separation, in particular to a device for recovering polluted nitrogen from an air separation tower and preparing high-purity nitrogen. Background Art

[0002] With the rise of my country's coal chemical, petrochemical, and nonferrous metallurgical industries, new demands have been placed on air separation technology. Safety, reliability, energy conservation, and emission reduction are fundamental requirements and prerequisites for air separation technology, essential for building a resource-saving, environmentally friendly society, and for scientific development. Existing technologies use a combination of upper and lower towers for air separation, producing high-purity nitrogen at the top of the lower tower and high-purity liquid oxygen in the evaporator at the bottom of the upper tower. When using this combination of upper and lower towers to produce high-purity nitrogen and liquid oxygen, a large amount of contaminated nitrogen is generated at the top of the upper tower. This contaminated nitrogen, after rewarming, is primarily used as a cooling source for circulating water in the water-cooling tower and as regeneration gas for molecular sieves. Due to the high nitrogen content in this contaminated nitrogen, its use as cooling source and regeneration gas results in a waste of nitrogen resources. However, this contaminated nitrogen also contains 0.3% to 2.0% oxygen and 0.2% to 0.6% argon, making it difficult to use as shielding gas or replacement gas for system equipment. Therefore, it is necessary to purify this contaminated nitrogen to produce high-purity nitrogen. Utility Model Content

[0003] Based on the existing technical problems, the utility model provides a device for recovering contaminated nitrogen from an air separation tower to prepare high-purity nitrogen. The utility model enables the contaminated nitrogen to be purified to prepare high-purity nitrogen and send it to a 0.7Mpa nitrogen pipeline network as protective gas and device replacement gas.

[0004] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0005] A device for recovering contaminated nitrogen from the upper tower of an air separation tower to prepare high-purity nitrogen comprises a booster device, a turbine expander, a contaminated nitrogen distillation tower, and a high-pressure plate heat exchanger. The inlet of the booster device is connected to the contaminated nitrogen outlet at the top of the upper tower of the air separation tower via a pipeline and a high-pressure plate heat exchanger. The booster device is provided with an outlet a and an outlet b. Outlet a is connected to the bottom of the contaminated nitrogen distillation tower via a high-pressure plate heat exchanger. Outlet b is connected to the contaminated nitrogen distillation tower via a high-pressure plate heat exchanger and a turbine expander in sequence. The gas phase outlet at the top of the contaminated nitrogen distillation tower is connected to a tower top condenser via a pipeline. The non-condensable steam outlet of the tower top condenser is connected to the high-pressure plate heat exchanger via a pipeline. The condensate outlet of the tower top condenser is divided into two outlets via a pipeline, one outlet being connected to the top of the contaminated nitrogen distillation tower and the other being connected to the high-pressure plate heat exchanger. The kettle of the contaminated nitrogen distillation tower is connected to the kettle of the lower tower of the air separation tower via a pipeline.

[0006] Furthermore, the booster device includes three or more boosters connected in series, the outlet b of the booster device is set at any booster outlet from the secondary booster to the final booster, and the outlet a of the booster device is set at the final booster outlet.

[0007] Furthermore, the cold liquid inlet of the top condenser is also connected to the kettle of the crude argon tower through a pipeline and a liquid oxygen pump, and the cold liquid outlet of the top condenser is connected to the bottom of the air separation tower through a pipeline.

[0008] Furthermore, the condensate outlet of the top condenser is divided into two routes through a pipeline, one route is connected to the top of the dirty nitrogen distillation tower, and the other route is connected to the 0.7Mpa nitrogen pipeline network through a high-pressure plate heat exchanger. A booster is installed on the pipeline connecting the high-pressure plate heat exchanger and the 0.7Mpa nitrogen pipeline network.

[0009] Furthermore, a nitrogen buffer tank is provided on the pipeline connecting the booster and the 0.7Mpa nitrogen pipeline network.

[0010] Furthermore, a circulating water cooler is provided at the outlet of each stage of the supercharger device. Beneficial effects

[0011] 1. The utility model increases the pressure of the contaminated nitrogen gas at the top of the air separation tower by a booster device and then sends it to the contaminated nitrogen distillation tower for distillation, thereby obtaining high-purity nitrogen at the top of the contaminated nitrogen distillation tower. The high-purity nitrogen is condensed in a tower top condenser to obtain high-purity liquid nitrogen. Part of the liquid nitrogen is refluxed into the contaminated nitrogen distillation tower, and the other part of the liquid nitrogen is converted into gas after being reheated by a high-pressure plate heat exchanger and enters the booster for pressure increase. The pressurized nitrogen is sent to a 0.7 MPa nitrogen pipeline network for use as protective gas and replacement gas for the device; the nitrogen resource in the contaminated nitrogen is fully utilized, and at the same time, the oxygen and argon in the contaminated nitrogen are enriched at the bottom of the contaminated nitrogen distillation tower and sent to the upper part of the air separation tower for distillation, thereby realizing the recovery and utilization of oxygen and argon in the contaminated nitrogen.

[0012] 2. The utility model utilizes the contaminated nitrogen gas at the top of the air separation tower to purify and prepare high-purity nitrogen. The contaminated nitrogen gas does not need to be purified by a water washing tower and molecular sieve. Compared with preparing nitrogen from air, the production cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural diagram of the utility model;

[0014] In the figure: 1-first-stage booster; 2-second-stage booster; 3-third-stage booster; 4-fourth-stage booster; 5-fifth-stage booster; 6-turbine expander; 7-high-pressure plate heat exchanger; 8-air separation tower; 9-dirty nitrogen distillation tower; 10-tower top condenser; 11-nitrogen buffer tank. DETAILED DESCRIPTION Example 1

[0015] Reference Figure 1 In order to make the contaminated nitrogen gas generated in the upper tower of the air separation tower 8 in industrial production fully used as protective gas and replacement gas for the device, the utility model provides a device for recovering the contaminated nitrogen gas in the upper tower of the air separation tower to prepare high-purity nitrogen, including a booster device, a turbine expander 6, a contaminated nitrogen distillation tower 9, and a high-pressure plate heat exchanger 7. The inlet of the booster device is connected to the contaminated nitrogen outlet at the top of the upper tower of the air separation tower 8 through a pipeline and the high-pressure plate heat exchanger 7. The booster device is provided with an outlet a and an outlet b. The outlet a is connected to the contaminated nitrogen outlet at the top of the upper tower of the air separation tower 8 through the high-pressure plate heat exchanger 7. Connected to the bottom of the dirty nitrogen distillation tower 9, the outlet b is connected to the dirty nitrogen distillation tower 9 in turn through the high-pressure plate heat exchanger 7 and the turbine expander 6; the booster device includes five boosters connected in series, namely a first-stage booster 1, a second-stage booster 2, a third-stage booster 3, a fourth-stage booster 4, and a fifth-stage booster 5. A circulating water cooler is provided at the outlet of each stage of the booster device to cool the compressed dirty nitrogen gas using circulating water. The outlet b of the booster device is provided at the outlet of the second-stage booster 2, and the outlet a of the booster device is provided at the outlet of the second-stage booster 2. The outlet of the five-stage booster 5; the gas phase outlet of the top of the dirty nitrogen distillation tower 9 is connected to the top condenser 10 through a pipeline, and the non-condensable steam outlet of the top condenser 10 is connected to the high-pressure plate heat exchanger 7 through a pipeline. The condensate outlet of the top condenser 10 is divided into two ways through the pipeline, one way is connected to the top of the dirty nitrogen distillation tower 9, and high-purity liquid nitrogen is used as the top reflux liquid of the dirty nitrogen distillation tower. The other way is connected to the 0.7Mpa nitrogen pipe network through the high-pressure plate heat exchanger 7. A booster is set on the pipe connecting the high-pressure plate heat exchanger 7 and the 0.7Mpa nitrogen pipe network. A nitrogen buffer tank 11 is provided on the pipeline connecting the booster and the 0.7Mpa nitrogen pipeline network; the cold liquid inlet of the top condenser 10 is also connected to the crude argon tower kettle through a pipeline and a liquid oxygen pump, and the cold liquid outlet of the top condenser 10 is connected to the bottom of the upper tower of the air separation tower 8 through a pipeline, and the liquid oxygen produced by the crude argon tower is used to condense the high-purity nitrogen at the top of the dirty nitrogen distillation tower 9; the kettle of the dirty nitrogen distillation tower 9 is connected to the kettle of the lower tower of the air separation tower 8 through a pipeline, and the oxygen-rich argon-rich liquid in the kettle of the dirty nitrogen distillation tower is sent to the lower tower of the air separation tower 8 for recycling.

[0016] The utility model works as follows: The contaminated nitrogen gas at the top of the air separation tower 8 is pressurized by a booster and then fed into a contaminated nitrogen distillation tower 9 for distillation. High-purity nitrogen is obtained at the top of the contaminated nitrogen distillation tower 9. The high-purity nitrogen is condensed in an overhead condenser 10 to produce high-purity liquid nitrogen. A portion of the liquid nitrogen is refluxed into the contaminated nitrogen distillation tower 9, while the remaining portion is reheated in a high-pressure plate heat exchanger 7, converted into a gaseous state, and then pressurized by a booster. The pressurized nitrogen is then fed to a 0.7 MPa nitrogen pipeline network for use as protective gas and replacement gas for the device. The oxygen-rich and argon-rich liquid in the kettle of the contaminated nitrogen distillation tower is fed to the lower tower of the air separation tower 8 for recycling.

[0017] Another embodiment differs from embodiment 1 in that: the booster device includes three boosters connected in series, namely a first-stage booster 1, a second-stage booster 2, and a third-stage booster 3; the outlet b of the booster device is arranged at the outlet of the second-stage booster 2; and the outlet a of the booster device is arranged at the outlet of the third-stage booster 3.

[0018] Another embodiment differs from embodiment 1 in that the booster device includes three boosters connected in series, namely a first-stage booster 1, a second-stage booster 2, and a third-stage booster 3, and the outlet a and outlet b of the booster device are both arranged at the outlet of the third-stage booster 3.

[0019] Another embodiment is different from embodiment 1 in that: the booster device includes five boosters connected in series, namely a first-stage booster 1, a second-stage booster 2, a third-stage booster 3, a fourth-stage booster 4, and a fifth-stage booster 5; the outlet b of the booster device is set at the outlet of the fourth-stage booster 4, and the outlet a of the booster device is set at the outlet of the fifth-stage booster 5.

[0020] Modifications and changes to the invention made by those familiar with the present invention are all within the patent scope of the present invention, and are not limited to those described in the embodiments.

Claims

1. A device for recovering polluted nitrogen from an air separation tower to prepare high-purity nitrogen, characterized in that: The invention comprises a booster device, a turbine expander, a dirty nitrogen distillation tower, and a high-pressure plate heat exchanger. The inlet of the booster device is connected to the dirty nitrogen outlet at the top of the upper tower of the air separation tower through a pipeline and a high-pressure plate heat exchanger. The booster device is provided with an outlet a and an outlet b. Outlet a is connected to the bottom of the dirty nitrogen distillation tower through a high-pressure plate heat exchanger. Outlet b is connected to the dirty nitrogen distillation tower through a high-pressure plate heat exchanger and a turbine expander in sequence. The gas phase outlet at the top of the dirty nitrogen distillation tower is connected to the top condenser through a pipeline. The non-condensable steam outlet of the top condenser is connected to the high-pressure plate heat exchanger through a pipeline. The condensate outlet of the top condenser is divided into two routes through a pipeline, one route is connected to the top of the dirty nitrogen distillation tower, and the other route is connected to the high-pressure plate heat exchanger. The tower kettle of the dirty nitrogen distillation tower is connected to the tower kettle of the lower tower of the air separation tower through a pipeline.

2. The device for recovering polluted nitrogen from an air separation tower to prepare high-purity nitrogen according to claim 1, wherein: The booster device comprises three or more boosters connected in series, the outlet b of the booster device is arranged at any booster outlet from the secondary booster to the final booster, and the outlet a of the booster device is arranged at the final booster outlet.

3. The device for recovering polluted nitrogen from an air separation tower to prepare high-purity nitrogen according to claim 1, wherein: The cold liquid inlet of the tower top condenser is also connected to the crude argon tower kettle through a pipeline and a liquid oxygen pump, and the cold liquid outlet of the tower top condenser is connected to the bottom of the air separation tower through a pipeline.

4. The device for recovering polluted nitrogen from an air separation tower to prepare high-purity nitrogen according to claim 1, wherein: The condensate outlet of the top condenser is divided into two routes through a pipeline, one route is connected to the top of the dirty nitrogen distillation tower, and the other route is connected to the 0.7Mpa nitrogen pipeline network through a high-pressure plate heat exchanger. A booster is set on the pipeline connecting the high-pressure plate heat exchanger and the 0.7Mpa nitrogen pipeline network.

5. The device for recovering polluted nitrogen from an air separation tower to prepare high-purity nitrogen according to claim 4, characterized in that: A nitrogen buffer tank is installed on the pipeline connecting the booster and the 0.7Mpa nitrogen pipeline network.

6. The device for recovering polluted nitrogen from an air separation tower to prepare high-purity nitrogen according to claim 1, characterized in that: A circulating water cooler is provided at the outlet of each stage of the supercharger device.

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