An Air Separation Unit is an industrial installation that separates atmospheric (outdoor) air into nitrogen, oxygen and argon gas. The gases are then delivered by pipeline or trucked to industrial users.

The ASU’s operating principle
The underlying technology is based on the fact that each of these gases has a different boiling point. The outside air is drawn in and first filtered and compressed. Then the air - a mixture of gases - is cooled to -173°C so that it becomes almost liquid. The cooled gas mixture is then separated in three distillation columns into pure oxygen, nitrogen, and argon.

The ASU in Moerdijk consists of several large modules, the heaviest of which weighs 580 tonnes and has dimensions of 10 x 10 x 65 metres. The modules were transferred at Moerdijk harbour to a pontoon by means of floating cranes. They were then transported by self-propelled modular transporter (SPMT) across the site to their ultimate destination, where two large cranes hoisted them into place.

Strategic location
The location in Moerdijk was strategically chosen, as Project Director Abel Slabbekoorn confirms: "The site is conveniently located near a number of major customers in the Moerdijk industrial port. And Moerdijk is at a junction of pipelines to Rotterdam and Antwerp. From this location, we can reach a large part of the Benelux via our pipelines. We can now also deliver liquefied gases by truck to customers in the Netherlands who are currently supplied from Belgium. For these customers, it will result in lower transport costs and consequently a reduced CO₂ footprint for supplying the gases."

Oxygen from the ASU will be used in the chemical and glass industries and for steel production, among other applications, while the nitrogen will be used mainly as an inert safety gas in a range of industries, and in food packaging. The argon extracted will also be used as an inert safety gas in the metals, automotive, electronics and food industries.

Reduced CO₂ footprint
The energy consumption of the new ASU will be approximately 10% lower than ASUs of the previous generation. "We achieved this through the more compact, modular construction of the ASU and because of improvements to air compressors, heat exchangers and turbines," Abel explains. "This not only reduces the specific energy consumption - and therefore the costs we charge our customers - but also the CO₂ footprint."

"We’ve also concluded a 25-megawatt power purchase agreement, which means that the ASUs are supplied with green power from wind farms in the North Sea. In time, the ASU will run entirely on renewable energy."

New opportunities for renewable energy
A well-known problem with renewable energy sources, such as sun and wind, is that the power they provide is highly dependent on local weather conditions. Nevertheless, supply and demand on the national grid must be perfectly balanced at all times.

A system that can store energy temporarily - when supply exceeds demand - and then use this energy when demand goes up again, is therefore an important driver for the wider use of renewable energy.

That’s why Air Liquide developed the innovative ALIVE™ system used for the first time in Moerdijk. The installation uses cryogenic liquid air for temporary energy storage. This allows energy consumption to be reduced for a period of time, without production falling. This helps to stabilise the grid, while security of supply is still guaranteed.

ASU construction is currently in full swing in Moerdijk and the start of production is planned for the summer of 2022.