System for preparing nitrogen and liquid nitrogen by using liquid oxygen

Abstract

The utility model discloses a system for preparing nitrogen and liquid nitrogen by using liquid oxygen. The system comprises an air filter, an air compressor, a pre-cooling unit, a purifier system and a cold box, a main heat exchanger, a rectifying tower, a subcooler, a condenser, an evaporator and a liquid nitrogen tank are arranged in the cold box; the purifier system is sequentially connected with a main heat exchanger and a rectifying tower; base liquid air of the rectifying tower is fed into a subcooler through a pipeline and then enters an evaporator arranged at the top of the rectifying tower; the top of the evaporator is sequentially connected with a subcooler and a main heat exchanger; the top of the rectifying tower is connected with an evaporator, a condenser and a main heat exchanger; the evaporator and the condenser are both connected with the liquid nitrogen tank; the liquid oxygen storage tank outside the cold box is connected with the condenser, and the top of the condenser is sequentially connected with the subcooler and the main heat exchanger. The system is low in energy consumption and stable in equipment, 99.999% of pure nitrogen and liquid nitrogen products are produced through evaporation cold energy of liquid oxygen, and vaporization filling export sales of the liquid oxygen can be achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of nitrogen and liquid nitrogen preparation, in particular to a system for preparing nitrogen and liquid nitrogen by utilizing liquid oxygen. Background Art

[0002] Current market conditions indicate that major steel and smelting companies nationwide are experiencing overcapacity and excess production capacity, leading to a significant surplus of liquid oxygen in their associated air separation equipment. This surplus cannot be consumed and must be released, resulting in waste. However, the booming new energy market, particularly in industries like photovoltaics, lithium batteries, and chip electronics, requires significant quantities of nitrogen and liquid nitrogen as shielding gases in production processes. Therefore, to balance and offset demand for nitrogen and liquid nitrogen and reduce liquid oxygen release, new systems and processes are needed to address these emerging market needs. Utility Model Content

[0003] The purpose of the utility model is to provide a system for producing nitrogen gas and liquid nitrogen by utilizing liquid oxygen in order to address the deficiencies in the prior art.

[0004] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0005] Provided is a system for producing nitrogen gas and liquid nitrogen using liquid oxygen, comprising an air filter, an air compressor, a pre-cooling unit, a purifier system and a cold box;

[0006] The air filter, air compressor, pre-cooling unit and purifier system are connected in sequence through pipelines. The cold box is equipped with a main heat exchanger E1, a distillation tower T1, a subcooler E2, a condenser K2, an evaporator K1 and a liquid nitrogen tank LV1;

[0007] The low-pressure process air outlet of the purifier system is connected to the main heat exchanger E1 and the bottom of the distillation tower T1 through a pipeline. The bottom liquid air of the distillation tower T1 is sent to the subcooler E2 through a pipeline and then enters the evaporator K1 arranged at the top of the distillation tower T1. The low-temperature contaminated nitrogen outlet at the top of the evaporator K1 is connected to the subcooler E2 and the main heat exchanger E1 through a pipeline, so that the low-temperature contaminated nitrogen is reheated and then led out of the cold box.

[0008] The nitrogen outlet at the top of the distillation tower T1 is connected to the evaporator K1, the condenser K2 and the main heat exchanger E1 respectively through branch pipelines. One of the three nitrogen streams is reheated by the main heat exchanger E1 and then sent out of the cold box as a nitrogen product; the liquid nitrogen outlets of the evaporator K1 and the condenser K2 are both connected to the liquid nitrogen tank LV1 through pipelines; the liquid oxygen storage tank outside the cold box is connected to the condenser K2 through a pipeline, and the gas oxygen outlet at the top of the condenser K2 is connected to the subcooler E2 and the main heat exchanger E1 through pipelines.

[0009] Furthermore, the air inlet end of the air filter is connected to a raw air pipeline.

[0010] Furthermore, the purifier system includes a first molecular sieve adsorber and a second molecular sieve adsorber used alternately in parallel, and an electric heater.

[0011] Furthermore, part of the low-temperature contaminated nitrogen gas after reheating that is led out of the cold box enters the electric heater through the pipeline, and the other part is discharged into the air at high altitude.

[0012] Furthermore, the liquid nitrogen outlet at the bottom of the liquid nitrogen tank LV1 is connected to the upper part of the distillation tower T1 and the subcooler E2 through branch pipelines.

[0013] Furthermore, the liquid nitrogen passing through the supercooler E2 is sent out of the cold box and connected to the liquid nitrogen tank LN2 for storage as a backup product.

[0014] Furthermore, the gas oxygen outlet of the main heat exchanger E1 is connected to the oxygen compressor through a pipeline.

[0015] Furthermore, the oxygen compressor is connected to a plurality of oxygen cylinders.

[0016] The present invention adopts the above technical solution, and compared with the prior art, has the following technical effects:

[0017] The system of the utility model utilizes liquid oxygen to produce nitrogen, has low energy consumption, requires fewer process equipment, does not require expander equipment, and is stable, safe and reliable. It utilizes the evaporation cold energy of liquid oxygen to produce 99.999% pure nitrogen and liquid nitrogen products, and can realize the vaporization, filling and export of liquid oxygen. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of a system for producing nitrogen gas and liquid nitrogen using liquid oxygen according to the present invention;

[0019] The accompanying drawings are as follows:

[0020] 1-air filter, 2-air compressor, 3-precooling unit, 4-purifier system, 5-main heat exchanger E1, 6-distillation tower T1, 7-subcooler E2, 8-condenser K2, 9-evaporator K1, 10-liquid nitrogen tank LV1, 11-liquid nitrogen tank LN2, 12-liquid oxygen storage tank, 13-oxygen compressor, 14-oxygen cylinder, 401-first molecular sieve adsorber, 402-second molecular sieve adsorber, 403-electric heater. DETAILED DESCRIPTION

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention. It should be noted that, unless there is a conflict, the embodiments and features in the embodiments of the present invention may be combined with each other.

[0022] refer to Figure 1 , the utility model provides a system for producing nitrogen gas and liquid nitrogen by using liquid oxygen, comprising an air filter 1, an air compressor 2, a pre-cooling unit 3, a purifier system 4 and a cold box;

[0023] The air filter 1, air compressor 2, pre-cooling unit 3 and purifier system 4 are connected in sequence through pipelines. The air inlet end of the air filter 1 is connected to the raw air pipeline. The cold box is equipped with a main heat exchanger E15, a distillation tower T16, a subcooler E27, a condenser K28, an evaporator K19 and a liquid nitrogen tank LV110.

[0024] The low-pressure process air outlet of purifier system 4 is connected to the main heat exchanger E15 and the bottom of distillation tower T16 via pipelines. The bottom liquid air of distillation tower T16 is sent to the subcooler E27 via pipelines and then enters the evaporator K19 installed at the top of distillation tower T16. The low-temperature contaminated nitrogen outlet at the top of evaporator K19 is connected to the subcooler E27 and the main heat exchanger E15 via pipelines, so that the low-temperature contaminated nitrogen is reheated and then led out of the cold box.

[0025] The nitrogen outlet at the top of distillation tower T16 is connected to the evaporator K19, condenser K28 and main heat exchanger E15 through branch pipelines. One of the three nitrogen streams is reheated in the main heat exchanger E15 and then sent out of the cold box as a nitrogen product. The liquid nitrogen outlets of evaporator K19 and condenser K28 are both connected to the liquid nitrogen tank LV110 through pipelines. The liquid oxygen storage tank 12 outside the cold box is connected to the condenser K28 through a pipeline. The gas oxygen outlet at the top of condenser K28 is connected to the subcooler E27 and the main heat exchanger E15 through pipelines.

[0026] In this embodiment, the liquid nitrogen outlet at the bottom of the liquid nitrogen tank LV110 is connected to the upper part of the distillation tower T16 and the subcooler E27 through branch pipelines; the liquid nitrogen passing through the subcooler E27 is sent out of the cold box and connected to the liquid nitrogen tank LN211 for backup product storage.

[0027] In this embodiment, the gas oxygen outlet of the main heat exchanger E15 is connected to the oxygen compressor 13 through a pipeline, and the oxygen compressor 13 is connected to a plurality of oxygen cylinders 14.

[0028] As a preferred example, the purifier system 4 includes a first molecular sieve adsorber 401 and a second molecular sieve adsorber 402 used alternately in parallel, and an electric heater 403; part of the low-temperature contaminated nitrogen gas after being reheated and led out of the cold box enters the electric heater 403 through a pipeline, and the other part is discharged into the air at high altitude.

[0029] The specific process flow of the system for producing nitrogen gas and liquid nitrogen from liquid oxygen of the utility model is as follows:

[0030] After the raw air passes through air filter 1, dust and impurities are filtered out. The filtered air then flows into air compressor 2, where it is compressed to a predetermined pressure and converted into low-pressure air. The low-pressure air from compressor 2 is pre-cooled to a predetermined temperature by pre-cooling unit 3, and then enters purifier system 4 (a first molecular sieve adsorber 401 and a second molecular sieve adsorber 402 are used alternately). Water, CO2, C2H2, etc. are removed from the pre-cooled low-pressure air to generate low-pressure processed air.

[0031] Low-pressure process air enters the main heat exchanger E1 of the cold box, where it is cooled to its saturation temperature with moisture. It is then fed into the bottom of distillation tower T1 for distillation. The liquid air at the bottom of distillation tower T1 passes through cooler E2, where it is decompressed by a throttle valve and enters evaporator K1. The liquid air is heated by nitrogen at the top of distillation tower T1 and converted into low-temperature contaminated nitrogen gas. This gas is then reheated by subcooler E2 and main heat exchanger E1 before exiting the cold box. A portion of the gas enters the electric heater 403 of the purifier system 4 and serves as regeneration gas to heat and activate the first and second molecular sieve adsorbers 401 and 402, while the remaining portion is vented to high altitude.

[0032] The nitrogen at the top of distillation tower T1 is split into three streams. One stream enters evaporator K1, where it is condensed into liquid nitrogen and enters liquid nitrogen tank LV1. Another stream enters condenser K2, where it is condensed into liquid nitrogen by excess liquid oxygen and also enters liquid nitrogen tank LV1. The last stream is reheated in main heat exchanger E1, then sent out of the cold box and into the pipeline network for use in downstream production lines. Liquid nitrogen is drawn from the bottom of liquid nitrogen tank LV1 and split into two streams. One stream flows back into distillation tower T1 as reflux liquid for distillation, while the other stream, as product liquid nitrogen, passes through cooler E2, is sent out of the cold box and connected to liquid nitrogen tank LN2 for backup product storage.

[0033] The liquid oxygen storage tank 12 is connected to the condenser K2 in the cold box. The liquid oxygen is heated by the nitrogen at the top of the distillation tower T1 and evaporated into gaseous oxygen. After passing through the cooler E2 and the main heat exchanger E1 for reheating, it is sent out of the cold box and connected to the oxygen compressor 13. After being pressurized by the oxygen compressor 13, it is filled into the oxygen cylinder 14 and shipped as oxygen product to scattered users.

[0034] Example 1

[0035] The system for producing nitrogen gas and liquid nitrogen using liquid oxygen has specific process parameters as shown in Table 1 (the demand for gaseous nitrogen is large, and the demand for liquid nitrogen is small):

[0036] Table 1

[0037] name Data indicators Compressed air (low-pressure processing air) flow rate <![CDATA[8000Nm 3 / h]]> Compressed air (low-pressure processing air) pressure 5.3Barg Nitrogen product flow <![CDATA[3500Nm 3 / h]]> Nitrogen product pressure 4.65 Barg Liquid nitrogen product flow <![CDATA[100Nm 3 / h]]> Product purity O3≤3ppm Liquid oxygen flow rate <![CDATA[200Nm 3 / h]]> Oxygen filling pressure 150Barg

[0038] Example 2

[0039] The system for producing nitrogen gas and liquid nitrogen using liquid oxygen has specific process parameters as shown in Table 2 (the demand for gaseous nitrogen is small, and the demand for liquid nitrogen is large):

[0040] Table 2

[0041] name Data indicators Compressed air (low-pressure processing air) flow rate <![CDATA[8000Nm 3 / h]]> Compressed air (low-pressure processing air) pressure 5.3Barg Nitrogen product flow <![CDATA[1600Nm 3 / h]]> Nitrogen product pressure 4.65 Barg Liquid nitrogen product flow <![CDATA[2000Nm 3 / h]]> Product purity O3≤3ppm Liquid oxygen flow rate <![CDATA[1850Nm 3 / h]]> Oxygen filling pressure 150Barg

[0042] The above description is only a preferred embodiment of the present invention and does not limit the implementation method and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A system for producing nitrogen gas and liquid nitrogen using liquid oxygen, characterized in that: It includes an air filter (1), an air compressor (2), a pre-cooling unit (3), a purifier system (4) and a cold box; The air filter (1), air compressor (2), pre-cooling unit (3) and purifier system (4) are connected in sequence through pipelines, and the cold box is provided with a main heat exchanger E1 (5), a distillation tower T1 (6), a subcooler E2 (7), a condenser K2 (8), an evaporator K1 (9) and a liquid nitrogen tank LV1 (10); The low-pressure processed air outlet of the purifier system (4) is connected to the main heat exchanger E1 (5) and the bottom of the distillation tower T1 (6) in sequence through pipelines. The bottom liquid air of the distillation tower T1 (6) is sent to the subcooler E2 (7) through a pipeline and then enters the evaporator K1 (9) arranged at the top of the distillation tower T1 (6); the low-temperature contaminated nitrogen outlet at the top of the evaporator K1 (9) is connected to the subcooler E2 (7) and the main heat exchanger E1 (5) in sequence through pipelines, so that the low-temperature contaminated nitrogen is reheated and then led out of the cold box; The nitrogen outlet at the top of the distillation tower T1 (6) is connected to the evaporator K1 (9), the condenser K2 (8) and the main heat exchanger E1 (5) respectively through branch pipelines. One of the three nitrogen streams is sent out of the cold box as a nitrogen product after being reheated by the main heat exchanger E1 (5); the liquid nitrogen outlets of the evaporator K1 (9) and the condenser K2 (8) are connected to the liquid nitrogen tank LV1 (10) through pipelines; the liquid oxygen storage tank (12) outside the cold box is connected to the condenser K2 (8) through a pipeline, and the gas oxygen outlet at the top of the condenser K2 (8) is connected to the subcooler E2 (7) and the main heat exchanger E1 (5) in sequence through pipelines.

2. The system for producing nitrogen gas and liquid nitrogen using liquid oxygen according to claim 1, characterized in that: The air inlet end of the air filter (1) is connected to the raw air pipeline.

3. The system for producing nitrogen gas and liquid nitrogen using liquid oxygen according to claim 1, characterized in that: The purifier system (4) includes a first molecular sieve adsorber (401) and a second molecular sieve adsorber (402) used alternately in parallel, and an electric heater (403).

4. The system for producing nitrogen gas and liquid nitrogen using liquid oxygen according to claim 3, characterized in that: A portion of the low-temperature contaminated nitrogen gas that has been reheated and is led out of the cold box enters the electric heater (403) through a pipeline, and the other portion is discharged to the air at high altitude.

5. The system for producing nitrogen gas and liquid nitrogen using liquid oxygen according to claim 1, characterized in that: The liquid nitrogen outlet at the bottom of the liquid nitrogen tank LV1 (10) is connected to the upper part of the distillation tower T1 (6) and the subcooler E2 (7) through branch pipelines.

6. The system for producing nitrogen gas and liquid nitrogen using liquid oxygen according to claim 5, characterized in that: The liquid nitrogen that has passed through the supercooler E2 (7) is sent out of the cold box and connected to the liquid nitrogen tank LN2 (11) for storage as a backup product.

7. The system for producing nitrogen gas and liquid nitrogen using liquid oxygen according to claim 1, wherein: The gas oxygen outlet of the main heat exchanger E1 (5) is connected to the oxygen compressor (13) through a pipeline.

8. The system for producing nitrogen gas and liquid nitrogen using liquid oxygen according to claim 7, characterized in that: The oxygen compressor (13) is connected to a plurality of oxygen cylinders (14).

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