US-based oxygen delivery specialist Oxair has supplied four pressure swing adsorption (PSA) oxygen tonnage plants to mines in Western Australia, removing risks associated with high pressure gas cylinders and bulk cryogenic liquefied gas.

Regarded as one of the world’s biggest mining hotspots, Western Australia is famous for its gold mines, in addition to its large-scale production of nickel and lithium.

With a continuous supply of high-purity oxygen needed for the mining proccess, a PSA plant purifies oxygen taken directly from the air by filtering out nitrogen. 

Capable of producing over 2kg of oxygen per day, Oxair’s PSA tonnage plants using around three kilowatts (kw) of electricity per 100 cubic feet of oxygen produced. 

How does PSA work?

Put simply, in PSA, specialised adsorbent materials such as zeolite or molecular sieves cause gas molecules to adhere to the surface of the material before the process is ‘swung’ to low pressure, causing the adsorbed material to desorb, separating the target gas from nitrogen.

The PSA process features two vessels, each one containing a zeolite molecular sieve as an adsorber. Compressed air passes through one adsorber, at which point the sieve selectively adsorbs the nitrogen. This is due to points of entry through the sieve being a particular size to allow oxygen molecules to pass through but not nitrogen molecules, producing oxygen as a product gas.

An inlet airflow is switched to the second adsorber once the first adsorber becomes saturated with nitrogen. The first adsorber undergoes regeneration by desorbing nitrogen through depressurisation and purging with some of the product oxygen. This process is repeated while the pressure continually swings between a higher level to allow adsorption and a lower level to allow desorption.

The bespoke oxygen generators can be designed according to the mine’s requirements and is suitable for outdoor or covered facilities. 

Stating that Oxair supplies equipment to mining operations around the world, David Cheeseman, Oxair, added, “Technical advances are transforming the sector all the time and innovation in autonomous underground mining and automated surface vehicles is accelerating the pace of sustainable solutions for equipment safety and reducing emissions.” 

By entirely replacing conventional oxygen cylinders with PSA systems, Oxair aims to boost production, improve safety, and save money.

Speaking to gasworld earlier in the year, Cheeseman explained the PSA process in more detail. “This unique process separates oxygen from compressed air. The gas is then stored in a buffer tank and made available for the end-user on demand,” he said.

“It eliminates residual wastage on un-consumed tanks and ensures clean and high-quality oxygen delivery free from rust, as most conventional tanks are made of carbon steel and prone to corrosion.”

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