Overview of Air Separation Units:
Air separation units (ASUs) are essential core equipment in modern industrial systems. They use scientific methods to separate and extract nitrogen and oxygen, the major components of air, along with smaller amounts of argon and rare gases. They provide stable, pure industrial gases for a wide range of industries, including steelmaking, petrochemicals, metalworking, electronics manufacturing, energy, healthcare, and food. The increasing demand for high-purity oxygen, nitrogen, and argon, particularly amidst the energy transition and the development of new materials, has further highlighted the application value of ASUs.
The operating principle of ASUs is primarily based on cryogenic distillation technology. After air is compressed, cooled, and liquefied, thermodynamic processes within a distillation tower exploit the differences in boiling points between its components for efficient separation. Although adsorption and membrane separation have also been applied in some applications in recent years, cryogenic distillation remains the mainstream and preferred process due to its high production capacity, high purity, and stable operation.
Methods of Air Separation
Cryogenic Distillation
Cryogenic distillation is the most classic and widely used air separation technology. The basic process includes air compression, pre-cooling, purification, liquefaction, and distillation. A turbine expander provides cooling, gradually liquefying the air. In the distillation tower, nitrogen, due to its lower boiling point (-196°C), evaporates preferentially, while oxygen, due to its higher boiling point (-183°C), condenses later. Through multiple cycles, high-purity separation is achieved.
This method not only produces gaseous oxygen, nitrogen, and argon, but also directly outputs cryogenic liquid products such as liquid oxygen, liquid nitrogen, and liquid argon. It is suitable for large-scale continuous operation and is widely used in high-demand sectors such as metallurgy and steelmaking, chemical raw materials, clean energy, and aerospace.
Adsorption Method
The adsorption method utilizes the selective adsorption capacity of molecular sieve materials (such as 5A, 13X, or carbon molecular sieves) for different gases. For example, molecular sieves have a stronger adsorption capacity for nitrogen, producing oxygen-enriched gas with an oxygen concentration of up to 93%. Carbon molecular sieves, on the other hand, have a lower adsorption capacity and are used to produce high-purity nitrogen. The adsorption method features compact equipment, simple operation, and low investment costs, making it suitable for small and medium-sized applications. However, due to technical limitations, it's currently impossible to simultaneously produce high-purity oxygen and nitrogen products. Therefore, cryogenic methods are still the primary method used in high-end applications.
Membrane Separation
Membrane separation utilizes the selectivity of organic polymer membranes for differences in the permeation rates of gas molecules. Oxygen permeates the membrane at approximately 4–5 times the rate of nitrogen, resulting in oxygen-enriched air. This method is simple to process and requires compact equipment, making it suitable for applications requiring portable or low-concentration oxygen enrichment, such as environmental protection and medical supplemental oxygen supply. However, its purity and production capacity are limited, with oxygen concentrations typically ranging from 28% to 35%, making it difficult to meet the high-purity gas needs of large-scale industry.
Composition of Air and Challenges of the Separation Process
Air is primarily composed of nitrogen (78%), oxygen (21%), and argon (approximately 1%), with trace amounts of rare gases such as neon, helium, krypton, and xenon. Their boiling point differences make separation feasible, but small amounts of impurities in the air can pose challenges:
Water vapor and carbon dioxide: They freeze easily at low temperatures, potentially blocking pipes and heat exchangers;
Mechanical impurities: They can wear or damage key air compressor components;
Hydrocarbons (such as acetylene): They pose a risk of accumulation and explosion at low temperatures;
Rare gases: Although present in low concentrations, they require special handling during the separation process, often controlled by specialized discharge valves.
Air separation units often require sophisticated air purification systems and strict process controls to ensure long-term stable and safe operation.
Application Value of Air Separation Units
Metallurgy: Provides oxygen for blast furnace ironmaking and converter steelmaking, accelerating combustion reactions and improving production efficiency;
Chemical and Petrochemical: Serves as a core gas source for processes such as ammonia synthesis, ethylene cracking, and coal gasification;
Energy and Environmental Protection: Widely used in oxygen-enriched combustion in power plants, wastewater treatment, and waste incineration;
Healthcare: Provides medical oxygen to hospitals and emergency medical services, ensuring life support;
Food and Electronics: Nitrogen is used in food preservation and chip manufacturing to ensure quality and safety.
NEWTEK's EPC Capabilities and Turnkey Project Advantages
Against the backdrop of global energy transition and the accelerated development of high-end manufacturing, air separation units (ASUs) are not just single pieces of equipment but complex systems. Leveraging its extensive industry experience and cross-disciplinary resource integration capabilities, NEWTEK offers clients one-stop EPC (Engineering, Procurement, Construction) and turnkey project services, encompassing engineering design, equipment manufacturing, installation and commissioning, project management, and after-sales operations and maintenance.
Engineering Design Capabilities: NEWTEK boasts a professional design team familiar with the entire ASU process, from process design and equipment selection to piping layout, ensuring scientific, efficient, and energy-efficient solutions.
Equipment and Technology Advantages: Integrating industry-leading cryogenic distillation technology, advanced molecular sieve purification systems, and high-efficiency, energy-saving turboexpanders ensures long-term, stable system operation.
Project Management and Coordination: For large and complex industrial projects, NEWTEK excels at resolving cross-departmental and cross-regional communication and interface challenges, ensuring seamless integration and efficient progress across design, procurement, construction, and commissioning. Turnkey Service: Customers can rely on NEWTEK's comprehensive support from project inception to final production. By providing installation guidance, operator training, remote technical support, and preventive maintenance, we help customers shorten construction cycles and reduce operational risks.
Wide Industry Coverage: NEWTEK's solutions have served a wide range of sectors, including textiles, metallurgy, chemicals, and energy. With a rich practical experience, we can customize optimal air separation system solutions for customers in various industries.
Conclusion
As the cornerstone of industrial gas supply, air separation units are supporting the development of the global manufacturing and energy industries with greater efficiency, safety, and environmental friendliness. From breakthroughs in principles to mature processes and then to large-scale applications, their value and significance continue to grow.
Leveraging its strong EPC capabilities and turnkey engineering capabilities, NEWTEK is helping global customers resolve technical and management challenges in complex projects, ensuring the safe, reliable, and efficient operation of industrial gas systems. With the development of clean energy and emerging industries, NEWTEK will continue to promote the upgrading and application of air separation technology with innovation and expertise, creating greater value for customers.
