The Air Separation Unit remains a key piece of equipment across a wide range of applications and industries. 

As the growing demand for industrial gasses continues to increase, the ASU provides a reliable and efficient method for producing these gasses at the required purity levels. At the same time, the air separation process offers a cost-effective means of producing high-purity gasses compared to other methods, generating them in large quantities, leading to economies of scale and reduced per-unit production costs over time.

But what exactly is an Air Separation Unit, how does it work and what are its key applications? Here’s a guide to the ASU, written from our experience in cryogenic engineering and design and manufacture of these structures.

What is an Air Separation Unit?

An Air Separation Unit (ASU) is an industrial facility used to separate atmospheric air into its primary components (namely nitrogen, oxygen, and, in some cases, argon and other rare gasses). These units are typically composed of elements such as air compressors, an air purification system, heat exchangers, cryogenic cooling systems and distillation columns, among others.

Case study: Download our Air Separation Unit success story

How does an Air Separation Unit work?

While there are various methods that can be performed by an Air Separation Unit, fractional distillation is the primary separation technique employed.

The main working principle behind an ASU is the separation of air via its liquefying and distilling processes. A simplified overview of how an ASU typically operates looks like this:

  • Compression: in this stage, atmospheric air is drawn into the ASU and passed through a series of compressors to increase its pressure. The purpose is to make the subsequent cooling and separation processes more efficient, with typical pressure ranges going between 5 and 10 bar gauge. 
  • Purification: before further processing, the compressed air is typically purified to remove impurities (including moisture, carbon dioxide, or trace contaminants). This step ensures that the separated gasses are of high purity and avoids issues such as the freezing or plugging of the cryogenic equipment.
  • Cooling: the now purified, compressed air is cooled down to cryogenic temperatures using a series of heat exchangers and refrigeration cycles. This results in liquefying the air, as cryogenic distillation relies on the differences in boiling points of the various components.
  • Separation: the now cold, liquefied air is fed into a distillation column (or a series of distillation columns), so that the air is separated into its primary components based on differences in boiling points:
  • Nitrogen has a lower boiling point (-196°C or -321°F) than oxygen (-183°C or -297°F).
  • Argon, if being separated, has an even lower boiling point (-186°C or -303°F).

As the air ascends the column, it is gradually warmed, and different components evaporate at their respective boiling points. For instance, oxygen-rich vapor rises to the top of the column, while nitrogen-rich liquid collects at the bottom. The argon, if present, is usually extracted as a side product at an intermediate point in the column.

  • Collection, storage and delivery: the separated gasses are collected and sent to storage tanks, either pressurized tanks or cryogenic tanks. From there, the gasses can then be distributed and supplied to various industries and applications, depending on their purity requirements.

Across these operations, it’s key for the Air Separation Unit to operate presenting a very tight integration of heat exchangers and separation columns, ensuring its efficiency.

Keep reading: Applied cryogenic technologies in the industry

Applications of an ASU

  • Healthcare: the use of oxygen and other technical gasses in the healthcare industry can benefit from an ASU
  • Industrial processes: the Air Separation Unit is part of the applied cryogenic technologies in the industry for processes such as metal fabrication, chemical production, and wastewater treatment. It’s also involved in generating high-purity gasses for the semiconductor industry for processes like wafer manufacturing and device fabrication.
  • Food and beverage: nitrogen is used as part of what are known as the ‘food gasses’, used in the food and beverage industry for packaging and preserving products.
  • Energy production: an ASU can provide high-purity oxygen for use in combustion processes in power plants and steel mills.

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Cryospain, experts in ASU projects

With our two-decade knowledge and experience in cryogenic engineering, at Cryospain we are one of the leading suppliers of state-of-the-art air separation plants. Our strength lies in our capacity to adjust to each project’s needs, considering its full lifecycle, potential and limitations. 

Through a combination of innovative technologies and end-to-end engineering services, we’ve designed, manufactured and implemented a series of successful ASU projects, all while complying with the relevant standards. 

As such, our involvement goes from procuring the materials, to assembling the equipment, electrics and piping, as well as taking care of crucial processes such as factory acceptance testing (FAT) for the containerized ASU’s components. It’s precisely our capacity to dedicate to planning, drawings, calculations and 3D modeling that makes us our strength, so that we can provide a tailored, end-to-end service.

Finally, we present an outstanding production capacity, with two large-scale workshops and two industrial hubs which sum up a combined 2600m2 dedicated to realizing our clients’ projects while guaranteeing the highest quality standards. 

Our success stories include: 

  • The provision of components for a containerized ASU project, a kind of prefabricated or modular ASU that facilitates transport, assembly, commissioning and installation. The result was a containerized ASU plant that presents cutting-edge rapid cooling and refrigeration technology, guaranteeing its cost-effectiveness. 
  • An integral cryogenic pipe-in-pipe system for a new Air Separation Unit in Ostrava (Czech Republic) for a major steel production company.
  • Two cryogenic piping projects in Poland and Russia, involving vacuum-insulated piping (VIP) for an Air separation unit (ASU) as part of a modern steel mill. The projects prioritized reducing its environmental impact in the area, so that it produces up to three times fewer emissions than a traditional mill.

Looking for a reliable, state-of-the-art and personalized Air Separation Unit project? Look no further. At Cryospain, we adapt to each project’s needs all while ensuring the highest manufacturing quality and taking into account cost-effectiveness. Get in touch with us and speak to our team about how we can help you.

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