Two-step process for preparing high-purity nitrogen

Abstract

The application discloses a two-step high-purity nitrogen preparation process, and a device required by the process comprises a filter, an air compressor, an air precooling system, a purification system, a main heat exchanger, a nitrogen column, a main condensation evaporator I, a supercooler, an argon removal column, a main condensation evaporator II and an expander. The raw material air is separated by a nitrogen column rectification to obtain pressure nitrogen, and then the pressure nitrogen is introduced into the argon removal column as raw material gas to continue rectification, so that high-quality nitrogen product and low-quality nitrogen product can be obtained at the same time, the high-quality nitrogen product can meet the production process requirements of high-end chips, and the low-quality nitrogen product can be supplied to users with relatively low requirements on impurities such as argon content and oxygen content, so that the demand of users on different quality nitrogen products can be met to the maximum extent. The application can also provide high-quality liquid nitrogen product.

Description

Technical Field

[0001] This invention relates to the field of air separation technology, specifically to a two-step process for producing high-purity nitrogen. Background Technology

[0002] In chip manufacturing and production, high-quality nitrogen is required for atmosphere protection and purging to ensure quality and performance. With the continuous development of chip technology, the quality requirements for the protective nitrogen used are also increasing. Currently, most chip manufacturers use conventional nitrogen generators to produce nitrogen as a product. Nitrogen produced by conventional generators has a high argon (Ar) content, generally above 1000 ppm, while high-end chip manufacturing processes require Ar content to be controlled below 3 ppm. This presents new challenges for nitrogen production. Summary of the Invention

[0003] The purpose of this invention is to provide a two-step process for producing high-purity nitrogen, thereby overcoming the shortcomings of existing technologies.

[0004] The technical solution adopted in this invention is as follows:

[0005] A two-step process for producing high-purity nitrogen, the equipment required for the process includes a filter, an air compressor, an air precooling system, a purification system, a main heat exchanger, a nitrogen tower, a main condenser-evaporator I, a subcooler, an argon removal tower, a main condenser-evaporator II, and an expander;

[0006] The filter, air compressor, air precooling system and purification system are located outside the cold box, while the main heat exchanger, nitrogen tower, main condenser-evaporator I, subcooler, argon removal tower, main condenser-evaporator II and expander are located inside the cold box. The main condenser-evaporator I is located above the nitrogen tower, and the main condenser-evaporator II is located above the argon removal tower. The nitrogen tower and the argon removal tower are coupled and arranged in parallel.

[0007] The filter, air compressor, air precooling system, purification system, and main heat exchanger are connected in sequence, and the cooling outlet of the main heat exchanger is connected to the air inlet at the bottom of the nitrogen tower.

[0008] The liquid air outlet at the bottom of the nitrogen tower is connected to the subcooler, the subcooler is connected to the main condenser-evaporator I, a throttling valve is installed on the connecting pipe between the subcooler and the main condenser-evaporator I, the oxygen-enriched air outlet of the main condenser-evaporator I is connected to the subcooler, the subcooler is connected to the main heat exchanger, part of the reheat outlet of the main heat exchanger is connected to the expander, the expander is connected to the main heat exchanger, and the main heat exchanger is connected to the purification system and the external vent pipe respectively.

[0009] The pressurized nitrogen outlet at the top of the nitrogen tower is connected to the main condenser-evaporator I and the argon removal tower, respectively. The liquid nitrogen outlet of the main condenser-evaporator I is connected to the top of the nitrogen tower.

[0010] The low-quality liquid nitrogen outlet at the bottom of the argon tower is connected to the main condenser-evaporator II. A throttling valve is installed on the connecting pipeline between the low-quality liquid nitrogen outlet at the bottom of the argon tower and the main condenser-evaporator II. The low-quality nitrogen outlet of the main condenser-evaporator II is connected to the subcooler and the main heat exchanger in sequence. The main heat exchanger is connected to the external low-quality nitrogen product supply network for users.

[0011] The high-quality nitrogen outlet at the top of the argon removal tower is connected to the main condenser-evaporator II and the main heat exchanger, respectively. The high-quality liquid nitrogen outlet of the main condenser-evaporator II is connected to the top of the argon removal tower and the external high-quality liquid nitrogen storage tank, respectively. The main heat exchanger is connected to the external high-quality nitrogen product supply network for users.

[0012] The process includes the following steps:

[0013] Step 1: After filtering out dust and mechanical impurities, the raw air enters the air compressor and is compressed to the set pressure; then it is pre-cooled by the air pre-cooling system and then purified in the purification system.

[0014] Step 2: A small portion of the purified air is used as instrument air, and the remainder is introduced into the main heat exchanger to be cooled to the saturation temperature and, after retaining a certain amount of moisture, enters the bottom of the nitrogen tower to participate in distillation.

[0015] Step 3: After the air is distilled in the nitrogen tower, it is separated into liquid air and pressurized nitrogen. The liquid air is subcooled by the cooler and throttled by the expansion valve before being introduced into the main condenser-evaporator I as a cold source. It is vaporized into oxygen-enriched air. The oxygen-enriched air is then reheated by the cooler and partially reheated by the main heat exchanger before being introduced into the expander to expand and obtain the required cooling capacity. After the expanded oxygen-enriched air is reheated by the main heat exchanger, part of it is used as waste nitrogen regeneration and introduced into the purification system, while the rest is vented as waste nitrogen. The pressurized nitrogen is divided into two streams. One stream of pressurized nitrogen is introduced into the main condenser-evaporator I as a heat source and liquefied into liquid nitrogen. The liquid nitrogen is introduced into the top of the nitrogen tower as reflux liquid, while the other stream of pressurized nitrogen is introduced into the bottom of the argon removal tower for further distillation.

[0016] Step 4: After the pressurized nitrogen is distilled in the argon removal tower, it is separated into low-quality liquid nitrogen and high-quality nitrogen. The low-quality liquid nitrogen is introduced into the main condenser-evaporator II as a cold source after being throttled by the throttle valve. It is vaporized into low-quality nitrogen. The low-quality nitrogen is then reheated in the cooler and the main heat exchanger before exiting the cold box as low-quality nitrogen product. The high-quality nitrogen is divided into two streams. One stream of high-quality nitrogen is introduced into the main condenser-evaporator II as a heat source and liquefied into high-quality liquid nitrogen. Part of the high-quality liquid nitrogen is introduced into the top of the argon removal tower as reflux liquid, and the rest exits the cold box as high-quality liquid nitrogen product. The other stream of high-quality nitrogen is reheated in the main heat exchanger before exiting the cold box as high-quality nitrogen product.

[0017] Furthermore, the air compressor is a turbine air compressor.

[0018] Furthermore, the expander is a turbine expander.

[0019] Furthermore, in step one, the air is compressed to 0.6-1.0 MPa by an air compressor.

[0020] Furthermore, in step one, the air is pre-cooled to 5-8°C by an air pre-cooling system.

[0021] Furthermore, in step three, the air is separated into liquid air and pressurized nitrogen after being distilled in a nitrogen tower. The liquid air has a pressure of 0.5-0.9 MPa and a purity of 35%-38% O2, while the pressurized nitrogen has a pressure of 0.5-0.9 MPa and a purity of 3 ppm O2 and ≥1000 ppm Ar.

[0022] Furthermore, in step four, the pressurized nitrogen gas is separated into low-quality liquid nitrogen and high-quality nitrogen gas after being distilled in an argon removal tower. The low-quality liquid nitrogen has a pressure of 0.3-0.5 MPa and a purity of 5 ppm O2 and ≥1500 ppm Ar, while the high-quality nitrogen gas has a pressure of 0.3-0.5 MPa and a purity of ≤3 ppm Ar.

[0023] Furthermore, in step four, the high-quality nitrogen product is produced at room temperature, at a pressure of 0.3-0.5 MPa, and with a purity of ≤3 ppmAr.

[0024] Furthermore, in step four, the low-quality nitrogen product is produced at room temperature and pressure with a purity of 5 ppm O2 and ≥1500 ppm Ar.

[0025] Furthermore, in step four, the high-quality liquid nitrogen product has a pressure of 0.3-0.5 MPa and a purity of ≤3 ppmAr.

[0026] The beneficial effects of this invention are:

[0027] 1. This invention is a two-step process for producing high-purity nitrogen. First, pressurized nitrogen is obtained by separating the raw material air through nitrogen distillation. Then, this pressurized nitrogen is introduced as the feed gas into an argon removal tower for further distillation. This process can simultaneously produce high-quality and low-quality nitrogen products. The high-quality nitrogen product has a pressure of 0.3-0.5 MPa and a purity of ≤3 ppmAr, which meets the requirements of high-end chip manufacturing processes. The low-quality nitrogen product is produced at atmospheric pressure with a purity of 5 ppmO2 and ≥1500 ppmAr, which can be supplied to users with relatively low requirements for argon and oxygen content and other impurities. This process can meet users' needs for nitrogen products of different qualities to the greatest extent. This invention can also provide high-quality liquid nitrogen products with a pressure of 0.3-0.5 MPa and a purity of ≤3 ppmAr.

[0028] 2. The equipment required for the process of this invention adopts a dual-tower series design, with the addition of an argon removal tower. The pressurized nitrogen generated by the nitrogen tower distillation is directly introduced into the argon removal tower as raw material. The dual towers are coupled and arranged in parallel, which reduces the cooling loss of the equipment, lowers the energy consumption of the equipment, and also reduces the height of the equipment, saving equipment investment. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the apparatus required for the process of this invention. Detailed Implementation

[0030] The present invention will be further explained below with reference to embodiments and accompanying drawings. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0031] A two-step process for producing high-purity nitrogen, the apparatus required for the process is as follows: Figure 1 As shown, it includes a filter 1, an air compressor 2, an air precooling system 3, a purification system 4, a main heat exchanger 6, a nitrogen tower 8, a main condenser-evaporator I9, a subcooler 10, an argon removal tower 11, a main condenser-evaporator II5, and an expander 7; the air compressor 2 can be a turbo air compressor, and the expander 7 can be a turbo expander;

[0032] Filter 1, air compressor 2, air precooling system 3 and purification system 4 are located outside the cold box. Main heat exchanger 6, nitrogen tower 8, main condenser-evaporator I9, subcooler 10, argon removal tower 11, main condenser-evaporator II5 and expander 7 are located inside the cold box. Main condenser-evaporator I9 is ​​located above nitrogen tower 8, and main condenser-evaporator II5 is located above argon removal tower 11. The nitrogen tower and argon removal tower are coupled and arranged in parallel.

[0033] Filter 1, air compressor 2, air precooling system 3, purification system 4, and main heat exchanger 6 are connected in sequence. The cooling outlet of the main heat exchanger 6 is connected to the air inlet at the bottom of the nitrogen tower 8.

[0034] The liquid air outlet at the bottom of nitrogen tower 8 is connected to subcooler 10. Subcooler 10 is connected to main condenser-evaporator I9. A throttling valve is installed on the connecting pipe between subcooler 10 and main condenser-evaporator I9. The oxygen-enriched air outlet of main condenser-evaporator I9 is ​​connected to subcooler 10. Subcooler 10 is connected to main heat exchanger 6. Part of the reheat outlet of main heat exchanger 6 is connected to expander 7. Expander 7 is connected to main heat exchanger 6. Main heat exchanger 6 is connected to purification system 4 and external vent pipe respectively.

[0035] The pressure nitrogen outlet at the top of nitrogen tower 8 is connected to the main condenser-evaporator I9 and the argon removal tower 11, respectively. The liquid nitrogen outlet of the main condenser-evaporator I9 is ​​connected to the top of nitrogen tower 8.

[0036] The low-quality liquid nitrogen outlet at the bottom of the argon removal tower 11 is connected to the main condenser evaporator II5. A throttling valve is installed on the connecting pipeline between the low-quality liquid nitrogen outlet at the bottom of the argon removal tower 11 and the main condenser evaporator II5. The low-quality nitrogen outlet of the main condenser evaporator II5 is connected to the subcooler 10 and the main heat exchanger 6 in sequence. The main heat exchanger 6 is connected to the external low-quality nitrogen product supply network for users.

[0037] The high-quality nitrogen outlet at the top of the argon removal tower 11 is connected to the main condenser-evaporator II5 and the main heat exchanger 6, respectively. The high-quality liquid nitrogen outlet of the main condenser-evaporator II5 is connected to the top of the argon removal tower 11 and the external high-quality liquid nitrogen storage tank, respectively. The main heat exchanger 6 is connected to the external high-quality nitrogen product supply network for users.

[0038] The functions of the above components are as follows:

[0039] Filter 1 is used to filter out dust and mechanical impurities from the raw material air;

[0040] Air compressor 2 is used to compress filtered air to a set pressure;

[0041] Air precooling system 3 is used to precool filtered and compressed air;

[0042] Purification system 4 is used to purify filtered, compressed, and pre-cooled air, removing substances such as moisture, CO2, and C2H2.

[0043] The main heat exchanger 6 is used to cool the purified air (excluding instrument air), reheat the low-quality nitrogen, some high-quality nitrogen, and expanded oxygen-enriched air, and partially reheat the oxygen-enriched air.

[0044] Nitrogen tower 8 is used to distill air into liquid air and pressurized nitrogen.

[0045] The main condenser-evaporator I9 is ​​used for heat exchange between liquid air and part of the pressurized nitrogen. The liquid air is vaporized into oxygen-enriched air, and the pressurized nitrogen is liquefied into liquid nitrogen.

[0046] Subcooler 10 is used to subcool liquid air and reheat oxygen-enriched air and low-quality nitrogen.

[0047] Argon tower 11 is used to distill part of the pressurized nitrogen gas into low-quality liquid nitrogen and high-quality nitrogen gas.

[0048] The main condenser-evaporator II5 is used for heat exchange between low-quality liquid nitrogen and some high-quality nitrogen. Low-quality liquid nitrogen is vaporized into low-quality nitrogen, and high-quality nitrogen is liquefied into high-quality liquid nitrogen.

[0049] Expander 7 is used to expand partially cooled oxygen-enriched air to produce the cooling capacity required by the device.

[0050] The process includes the following steps:

[0051] Step 1: After the raw material air is filtered through filter 1 to remove dust and mechanical impurities, it enters air compressor 2 to compress the air to a set pressure of 0.6-1.0 MPa; then it is pre-cooled to 5-8℃ by air pre-cooling system 3 and then enters purification system 4 for purification to remove substances such as moisture, CO2, and C2H2.

[0052] Step 2: A small portion of the purified air is used as instrument air (not shown in the figure), and the remainder is introduced into the main heat exchanger 6 to be cooled to the saturation temperature and then enters the bottom of the nitrogen tower 8 to participate in the distillation after being moistened to a certain extent.

[0053] Step 3: After distillation in nitrogen tower 8, air is separated into liquid air (pressure 0.5-0.9 MPa, purity 35%-38% O2) and pressurized nitrogen (pressure 0.5-0.9 MPa, purity 3 ppm O2, ≥1000 ppm Ar). The liquid air is subcooled by cooler 10 and throttled by a throttling valve before being introduced into the main condenser-evaporator 19 as a cold source, where it is vaporized into oxygen-enriched air. The oxygen-enriched air is then reheated sequentially by cooler 10 and part of the main heat exchanger 6. The expansion unit 7 is introduced to generate the required cooling capacity for the expansion process. The expanded oxygen-enriched air is reheated to room temperature by the main heat exchanger 6. Part of it is then introduced into the purification system 4 as waste nitrogen regeneration gas and heated to serve as the regeneration gas for the purification system 4. The remaining part is released as waste nitrogen gas. The pressurized nitrogen gas is divided into two streams. One stream of pressurized nitrogen gas is introduced into the main condenser evaporator I9 as a heat source and liquefied into liquid nitrogen. The liquid nitrogen gas is introduced into the top of the nitrogen tower 8 as reflux liquid. The other stream of pressurized nitrogen gas is introduced into the bottom of the argon removal tower 11 for further distillation.

[0054] Step 4: After distillation in argon removal tower 11, pressurized nitrogen is separated into low-quality liquid nitrogen (pressure 0.3-0.5 MPa, purity 5 ppm O2, ≥1500 ppm Ar) and high-quality nitrogen (pressure 0.3-0.5 MPa, purity ≤3 ppm Ar). The low-quality liquid nitrogen is throttled by a throttling valve and introduced into the main condenser-evaporator II5 as a cold source, where it is vaporized into low-quality nitrogen. The low-quality nitrogen is then reheated in cooler 10 and main heat exchanger 6 to room temperature before exiting the cold box as the low-quality nitrogen product (atmospheric pressure, purity 5 ppm O2). 2. High-quality nitrogen (≥1500ppmAr); The high-quality nitrogen is divided into two streams. One stream of high-quality nitrogen is introduced into the main condenser-evaporator II5 as a heat source and liquefied into high-quality liquid nitrogen. Part of the high-quality liquid nitrogen is introduced into the top of the argon removal tower 11 as reflux liquid, and the rest exits the cold box as high-quality liquid nitrogen product (pressure 0.3-0.5MPa, purity ≤3ppmAr). The other stream of high-quality nitrogen is reheated to room temperature by the main heat exchanger 6 and then exits the cold box as high-quality nitrogen product (pressure 0.3-0.5MPa, purity ≤3ppmAr).

Claims

1. A two-step process for producing high purity nitrogen, characterized in that, The equipment required for the process includes a filter, an air compressor, an air precooling system, a purification system, a main heat exchanger, a nitrogen tower, a main condenser-evaporator I, a subcooler, an argon removal tower, a main condenser-evaporator II, and an expander; The filter, air compressor, air precooling system and purification system are located outside the cold box, while the main heat exchanger, nitrogen tower, main condenser-evaporator I, subcooler, argon removal tower, main condenser-evaporator II and expander are located inside the cold box. The main condenser-evaporator I is located above the nitrogen tower, and the main condenser-evaporator II is located above the argon removal tower. The nitrogen tower and the argon removal tower are coupled and arranged in parallel. The filter, air compressor, air precooling system, purification system, and main heat exchanger are connected in sequence, and the cooling outlet of the main heat exchanger is connected to the air inlet at the bottom of the nitrogen tower. The liquid air outlet at the bottom of the nitrogen tower is connected to the subcooler, the subcooler is connected to the main condenser-evaporator I, a throttling valve is installed on the connecting pipe between the subcooler and the main condenser-evaporator I, the oxygen-enriched air outlet of the main condenser-evaporator I is connected to the subcooler, the subcooler is connected to the main heat exchanger, part of the reheat outlet of the main heat exchanger is connected to the expander, the expander is connected to the main heat exchanger, and the main heat exchanger is connected to the purification system and the external vent pipe respectively. The pressurized nitrogen outlet at the top of the nitrogen tower is connected to the main condenser-evaporator I and the argon removal tower, respectively. The liquid nitrogen outlet of the main condenser-evaporator I is connected to the top of the nitrogen tower. The low-quality liquid nitrogen outlet at the bottom of the argon tower is connected to the main condenser-evaporator II. A throttling valve is installed on the connecting pipeline between the low-quality liquid nitrogen outlet at the bottom of the argon tower and the main condenser-evaporator II. The low-quality nitrogen outlet of the main condenser-evaporator II is connected to the subcooler and the main heat exchanger in sequence. The main heat exchanger is connected to the external low-quality nitrogen product supply network for users. The high-quality nitrogen outlet at the top of the argon removal tower is connected to the main condenser-evaporator II and the main heat exchanger, respectively. The high-quality liquid nitrogen outlet of the main condenser-evaporator II is connected to the top of the argon removal tower and the external high-quality liquid nitrogen storage tank, respectively. The main heat exchanger is connected to the external high-quality nitrogen product supply network for users. The process includes the following steps: Step 1: After filtering out dust and mechanical impurities, the raw air enters the air compressor and is compressed to the set pressure; then it is pre-cooled by the air pre-cooling system and then purified in the purification system. Step 2: A small portion of the purified air is used as instrument air, and the remainder is introduced into the main heat exchanger to be cooled to the saturation temperature and, after retaining a certain amount of moisture, enters the bottom of the nitrogen tower to participate in distillation. Step 3: After the air is distilled in the nitrogen tower, it is separated into liquid air and pressurized nitrogen. The liquid air is subcooled by the cooler and throttled by the expansion valve before being introduced into the main condenser-evaporator I as a cold source. It is vaporized into oxygen-enriched air. The oxygen-enriched air is then reheated by the cooler and partially reheated by the main heat exchanger before being introduced into the expander to expand and obtain the required cooling capacity. After the expanded oxygen-enriched air is reheated by the main heat exchanger, part of it is used as waste nitrogen regeneration and introduced into the purification system, while the rest is vented as waste nitrogen. The pressurized nitrogen is divided into two streams. One stream of pressurized nitrogen is introduced into the main condenser-evaporator I as a heat source and liquefied into liquid nitrogen. The liquid nitrogen is introduced into the top of the nitrogen tower as reflux liquid, while the other stream of pressurized nitrogen is introduced into the bottom of the argon removal tower for further distillation. Step 4: After the pressurized nitrogen is distilled in the argon removal tower, it is separated into low-quality liquid nitrogen and high-quality nitrogen. The low-quality liquid nitrogen is introduced into the main condenser-evaporator II as a cold source after being throttled by the throttle valve. It is vaporized into low-quality nitrogen. The low-quality nitrogen is then reheated in the cooler and the main heat exchanger before exiting the cold box as low-quality nitrogen product. The high-quality nitrogen is divided into two streams. One stream of high-quality nitrogen is introduced into the main condenser-evaporator II as a heat source and liquefied into high-quality liquid nitrogen. Part of the high-quality liquid nitrogen is introduced into the top of the argon removal tower as reflux liquid, and the rest exits the cold box as high-quality liquid nitrogen product. The other stream of high-quality nitrogen is reheated in the main heat exchanger before exiting the cold box as high-quality nitrogen product.

2. The process for producing high purity nitrogen in two steps according to claim 1, characterized in that, The air compressor is a turbine air compressor.

3. The process for producing high purity nitrogen in two steps according to claim 1, characterized in that, The expander is a turbine expander.

4. The process for producing high purity nitrogen in two steps according to claim 1, characterized in that, In step one, the air is compressed to 0.6-1.0 MPa by an air compressor.

5. The process as claimed in claim 1, wherein, In step one, the air is pre-cooled to 5-8°C by an air pre-cooling system.

6. The process for producing high purity nitrogen in two steps according to claim 1, characterized in that, In step three, air is separated into liquid air and pressurized nitrogen after being distilled in a nitrogen tower. The liquid air has a pressure of 0.5-0.9 MPa and a purity of 35%-38% O2, while the pressurized nitrogen has a pressure of 0.5-0.9 MPa and a purity of 3 ppm O2 and ≥1000 ppm Ar.

7. The process as claimed in claim 1, wherein, In step four, the pressurized nitrogen gas is separated into low-quality liquid nitrogen and high-quality nitrogen gas after being distilled in an argon removal tower. The low-quality liquid nitrogen has a pressure of 0.3-0.5 MPa and a purity of 5 ppm O2 and ≥1500 ppm Ar. The high-quality nitrogen gas has a pressure of 0.3-0.5 MPa and a purity of ≤3 ppm Ar.

8. The process of claim 1, wherein the process is a two-step process for producing high purity nitrogen. In step four, the high-quality nitrogen product is produced at room temperature, at a pressure of 0.3-0.5 MPa, and with a purity of ≤3 ppmAr.

9. The process for producing high purity nitrogen according to claim 1, wherein In step four, the low-quality nitrogen product is produced at room temperature and pressure with a purity of 5 ppm O2 and ≥1500 ppm Ar.

10. The process for producing high purity nitrogen in two steps according to claim 1, characterized in that, In step four, the high-quality liquid nitrogen product has a pressure of 0.3-0.5 MPa and a purity of ≤3 ppmAr.

Images