Air Separation Equipment

Cryogenic Air Separation Plant: Working Principle and Application

Air separation plant is an indispensable and important equipment in modern industrial production. As the global demand for industrial gases continues to grow, air separation plants provide the market with reliable, efficient and economical solutions for gas production. They are particularly suitable for the stable supply of large-scale, high-purity gases, helping companies to reduce unit production costs and realize economies of scale.

What is an Air Separation Unit?

An air separation unit (ASU) is an industrial facility that uses cryogenic distillation to separate atmospheric air into its main components: nitrogen, oxygen, and sometimes argon, as well as other rare gases.

This type of facility typically consists of the following core components: 

Air Compressor 

Air Purification System 

Heat Exchanger 

Cryogenic Cooling System 

Distillation Tower 

Working in tandem, the ASU is able to consistently and efficiently separate and supply a wide range of industrial gases with the required purity.

Working Principle of Air Separation Unit 

Although air separation unit can adopt a variety of technologies, low-temperature liquefaction and fractional distillation is the most widely used core process at present. Its workflow consists of the following main steps: 

1. Compression 

First, atmospheric air is drawn into the unit, where it is pressurized by a multi-stage compressor to a gauge pressure of 5 to 10 bar. This process is designed to increase cooling efficiency and optimize subsequent separations.

2. Purification 

The compressed air enters a purification system that removes moisture, carbon dioxide and trace contaminants. This step prevents impurities from freezing and clogging the pipes at low temperatures and ensures the safe and stable operation of the subsequent equipment.

3. Cooling 

The purified air is cooled down by a heat exchanger and a refrigeration cycle to a liquefied state. This process relies on the difference in boiling points of the components in the air to form a low-temperature liquid air.

4. Separation 

The liquefied air is fed into a distillation column where it is separated by the different boiling points of the components: 

Nitrogen boils at about -196°C 

Oxygen boils at about -183°C 

Argon boils at about -186°C 

As the air slowly rises in the column, the temperature gradually increases and the different components evaporate at their respective boiling points and are collected in layers. For example, oxygen vapor rises to the top of the tower, while nitrogen liquid collects at the bottom. Argon, on the other hand, is usually extracted as a by-product in the middle layer of the tower.

5. Collection, Storage and Transportation 

The separated gases are piped to storage tanks where they are stored in liquid or gaseous form and the supply is distributed according to industrial demand.

Main Applications Of Air Separation Units

Medical Industry 

Provides high purity oxygen and other medical technology gases for life support systems in hospitals, clinics, etc.

Industrial Manufacturing 

Widely used in processes such as metal smelting, chemical production, waste water treatment and semiconductor manufacturing, supplying high purity gases such as oxygen, nitrogen and argon.

Food & Beverage 

Nitrogen is used in the food and beverage industry for modified atmosphere packaging (MAP) and food preservation to extend product shelf life.

Energy & Steel 

High purity oxygen is used for oxygen-enriched combustion in power plants and steel mills to improve combustion efficiency and reduce emissions.

Chengde: The trusted manufacturer of air separation plants 

With over 20 years of experience in cryogenic engineering and industrial gas plant manufacturing, Chengde has become one of the world's leading suppliers of air separation plants.

We have 3 production sites with a total area of 69,000 square meters and excellent production capacity.

Chengde owns and operates more than 100 air separation plants in more than 10 countries around the world, with daily oxygen production ranging from 50 tons to 4,000 tons per day, and is developing plants with a single oxygen production of up to 7,000 tons per day.

We provide end-to-end services from project needs assessment, schematic design, 3D modeling, equipment fabrication, on-site installation to commissioning and delivery, ensuring the delivery of high-quality and cost-effective solutions.

Chengde has built more than 1,000 Air Separation Plants across a wide range of industries including Oil & Gas, Refining, Chemical, Metallurgy, Power, Mining, etc., and has won numerous awards and certifications for safety in the industry.

Chengde's core strengths 

On-demand design: cost-effective gas supply solutions tailored to different project requirements.

Engineering Capability: Full coverage of material procurement, equipment assembly, electrical system and piping installation, and FAT testing of containerized air separation components.

Industry experience: applicable to various application scenarios such as steel, non-ferrous metals, petrochemicals, energy, mining and so on.

Quality Assurance: Strict control of manufacturing processes, always ensuring compliance with international safety standards.

FAQs

Q: Why is cryogenic fractionation chosen over other methods for air separation plants?

A: Cryogenic Fractionation is the most mature and cost-effective industrial solution, relying on the difference in boiling points of the gas components to enable large-scale continuous and stable production of high-purity gases.

Q: What industries can Chengde's air separation equipment serve?

A: Our equipment is widely used in: 

oil and gas, petroleum refining, chemicals and petrochemicals, power generation, iron and steel, non-ferrous metal smelting, food processing, medical industry, and mining such as gold and copper.

Q: What is the maximum capacity of Chengde's air separation plants?

A: Chengde currently has a single unit in operation with a capacity of up to 3,800 tons of oxygen per day, and the maximum capacity under development is targeted at 7,000 tons of oxygen per day, which meets the air demand of all types of large and medium-sized enterprises.

Q: How does Chengde ensure the safety and quality of its air separation plants?

A: Since our inception in 2002, we have completed over 1,000 plant deliveries and have accumulated more safety-related awards than any other comparable industrial gas company, ensuring stable project operation and employee safety.

Whether your business involves steel, non-ferrous metals, petrochemical energy, advanced gasification or oxygen-rich combustion processes, Chengde has the technical expertise and project experience to help you design, manufacture and operate a safe and reliable air separation plant to meet your specific gas supply needs.