An air separation unit (ASU) is a crucial piece of equipment in various industries, playing a vital role in separating atmospheric air into its primary components, such as nitrogen, oxygen, and argon. As a reputable air separation unit supplier, I am delighted to share the working principle of an air separation unit in detail.
1. The Initial Stage: Air Intake and Pre - treatment
The process of an air separation unit begins with the intake of atmospheric air. Atmospheric air is a mixture mainly composed of about 78% nitrogen, 21% oxygen, and small amounts of other gases like argon, carbon dioxide, water vapor, and trace impurities.
The air is first drawn into the ASU through a large - scale air intake system. This intake system is equipped with filters to remove large - sized particles such as dust, pollen, and other debris from the air. These filters are designed to ensure that the air entering the subsequent processing stages is relatively clean, preventing damage to the internal components of the ASU.
After passing through the initial filters, the air enters a pre - cooling unit. Here, the air is cooled to a lower temperature, typically around 5 - 10 degrees Celsius. This cooling step helps to reduce the volume of the air, making it more suitable for further processing. Additionally, it causes a significant amount of water vapor in the air to condense and be removed. The condensed water is drained out of the system, which is important because water vapor can freeze in the subsequent cryogenic stages and cause blockages in the equipment.
2. Compression and Purification
Once the air is pre - treated, it is sent to a compressor. The compressor plays a crucial role in increasing the pressure of the air. Usually, the air is compressed to a pressure ranging from 5 to 10 bar. Compression not only increases the density of the air but also provides the necessary energy for the subsequent separation process.
After compression, the air enters a purification system. This system is designed to remove remaining impurities such as carbon dioxide, water vapor, and hydrocarbons. One common purification method is the use of molecular sieves. Molecular sieves are porous materials with tiny pores of a specific size. They can selectively adsorb molecules based on their size and polarity. For example, carbon dioxide and water vapor molecules are adsorbed onto the surface of the molecular sieves, leaving the air relatively pure.
The purification process is often carried out in a twin - bed configuration. While one bed is in the adsorption mode, removing impurities from the incoming air, the other bed is being regenerated. Regeneration typically involves heating the molecular sieve bed and passing a small amount of purified air through it in the reverse direction to desorb the adsorbed impurities and restore the adsorption capacity of the molecular sieve.
3. Cryogenic Cooling
The purified and compressed air then enters the cryogenic section of the air separation unit. Cryogenic cooling is the key step in separating the air into its components. The air is gradually cooled to extremely low temperatures, typically below - 170 degrees Celsius.
This cooling is achieved through a series of heat exchangers and expansion processes. The heat exchangers are designed to transfer heat between different streams of air and refrigerants. For example, cold product gases (such as nitrogen and oxygen) leaving the separation column are used to cool the incoming compressed air in the heat exchangers.
One important expansion device used in the cryogenic cooling process is the turbo - expander. The compressed air is allowed to expand through the turbo - expander, which causes a significant drop in temperature due to the Joule - Thomson effect. As the air expands, it does work on the turbine blades of the turbo - expander, converting some of its internal energy into mechanical energy, which can be used to drive other equipment in the ASU, such as the compressor.
4. Distillation in the Separation Column
After reaching the cryogenic temperature, the air enters the separation column. The separation column is a tall, vertical vessel where the actual separation of the air components occurs based on their different boiling points.
The separation column is usually divided into multiple trays or packed sections. The lower part of the column is called the high - pressure column, and the upper part is the low - pressure column. The compressed and cooled air enters the high - pressure column. At the bottom of the high - pressure column, the air is at a relatively high pressure and contains a mixture of liquid and vapor phases.
Nitrogen, which has a lower boiling point (- 196 degrees Celsius) compared to oxygen (- 183 degrees Celsius), vaporizes more readily and rises to the top of the high - pressure column, while oxygen, which is heavier, tends to accumulate at the bottom in the liquid phase.
The nitrogen vapor from the top of the high - pressure column is then sent to the low - pressure column after being further cooled. In the low - pressure column, a similar distillation process occurs. At the bottom of the low - pressure column, liquid oxygen with a high purity can be obtained. The nitrogen vapor from the top of the low - pressure column can be further processed to obtain high - purity nitrogen gas.
5. Product Extraction and Storage
Once the separation is completed in the distillation column, the separated products (nitrogen, oxygen, and argon) are extracted from the appropriate locations in the column.
High - purity oxygen can be withdrawn from the bottom of the low - pressure column as a liquid or vapor, depending on the specific requirements of the end - user. Nitrogen is typically taken from the top of the low - pressure column as a gas. Argon, which is present in the air in small amounts, can be extracted from a side stream of the low - pressure column and further purified in a separate argon column.
The extracted products are then stored in appropriate storage facilities. Liquid products such as liquid oxygen and liquid nitrogen are stored in cryogenic storage tanks, which are well - insulated to minimize heat transfer and prevent vaporization. Gaseous products can be stored in high - pressure gas cylinders or in large - scale storage vessels.
Applications and Our Product Offerings
Air separation units have a wide range of applications in different industries. In the steel industry, oxygen is used for steelmaking processes to increase the efficiency of the combustion and reduce the production of impurities. Nitrogen is used for blanketing and purging in various industrial processes to prevent oxidation and explosion. In the chemical industry, both oxygen and nitrogen are used as raw materials for the production of various chemicals.
As an air separation unit supplier, we offer a variety of high - quality products to meet the diverse needs of our customers. For example, our 2025 New China Manufacturer Air Separation Equipment Liquid Air Separation Unit Cryogenic Air Separation Plant is designed with advanced technology and high - quality components, ensuring reliable and efficient operation. It can produce large quantities of oxygen, nitrogen, and argon with high purity.
Our CNCD Customized Sales Cryogenic Air Separation Plant provides customized solutions. We understand that different customers have different requirements in terms of production capacity, product purity, and operating conditions. Therefore, we can tailor - make the air separation plant according to the specific needs of each customer.
Another notable product is our High Purity Oxygen Nitrogen Generators With Remote Conrtol System. This generator is equipped with a remote control system, allowing users to monitor and control the operation of the equipment from a distance. It is suitable for applications where continuous and stable supply of high - purity oxygen and nitrogen is required.
Conclusion and Call to Action
In conclusion, the working principle of an air separation unit is a complex but well - defined process that involves multiple stages of pre - treatment, compression, purification, cryogenic cooling, distillation, and product extraction. Each stage is crucial for ensuring the efficient and reliable separation of atmospheric air into its valuable components.
If you are in need of an air separation unit for your industrial applications, we are here to provide you with the best solutions. Our products are designed to meet the highest quality standards and offer excellent performance. We invite you to contact us for more information and to discuss your specific requirements. Our team of experts is ready to assist you in choosing the most suitable air separation unit for your business.
References
- Perry, R. H., & Green, D. W. (Eds.). (1997). Perry's Chemical Engineers' Handbook. McGraw - Hill.
- Kohl, A. L., & Nielsen, R. B. (1997). Gas Purification. Gulf Publishing Company.
- Ruhe, H., & Storch, W. (2002). Cryogenic Air Separation Technology. Springer - Verlag.