The short answer
Industrial oxygen is simply oxygen separated from air (air is about 21% oxygen and 78% nitrogen) and concentrated for use in industry, hospitals and processes. A PSA oxygen plant produces it on site by removing the nitrogen from compressed air, leaving 93–95% oxygen.
PSA stands for Pressure Swing Adsorption. The plant pushes compressed air through vessels packed with zeolite molecular sieves (ZMS) — a material that adsorbs (traps) nitrogen under pressure and lets oxygen pass. Two towers alternate: while one produces oxygen, the other releases its trapped nitrogen at low pressure, so the supply is continuous.
What does PSA mean?
"Pressure Swing Adsorption" describes exactly how it works. *Adsorption* is nitrogen sticking to the surface of the zeolite. *Pressure swing* is the trick that makes it continuous: nitrogen is adsorbed at high pressure, then released when the pressure is dropped (swung) back down. By swinging the pressure up and down in two towers out of step with each other, the plant produces oxygen without a break.
It is a purely physical process — no chemical reaction, no consumables burned. The zeolite is not used up; it works for years. The only inputs are electricity and air.
How a PSA oxygen plant works — step by step
An IIGAS PSA oxygen plant is a skid-mounted, PLC-automatic system. Air becomes bottled-quality oxygen through these stages:
- 11 · Air compressionA screw air compressor draws in atmospheric air and compresses it to about 7.5 bar g.
- 22 · Cooling & dryingThe air is cooled, and a refrigerated dryer plus auto drain removes moisture — dry air is essential, because water would blind the zeolite.
- 33 · FiltrationActivated-carbon and multi-stage filters strip oil and particulates so only clean, dry air reaches the sieves.
- 44 · Twin-tower PSA separationThe air enters two towers packed with zeolite molecular sieves. Under pressure the sieve adsorbs nitrogen and lets oxygen through. When one tower saturates, quick-changeover valves switch to the second while the first depressurises and purges its nitrogen — giving continuous flow.
- 55 · Surge & storageThe 93–95% oxygen passes to a surge vessel that steadies purity and pressure, then to a storage tank (and, if required, a cylinder-filling booster).
- 66 · MonitoringAn online oxygen analyser watches purity continuously, with audio-visual alarms, all managed from an HMI touch-screen panel.
Delivery is typically 93% ±3% oxygen at about 4.5–6 kg/cm²g, with an atmospheric dew point around −40 °C.
PSA oxygen vs cryogenic oxygen — which do you need?
There are two ways to separate oxygen from air. Choosing right saves a lot of money:
| PSA oxygen plant | Cryogenic (ASU) | |
|---|---|---|
| Purity | 93–95% | 99.5%+ (up to 99.7%) |
| Best for | On-site use, cutting, brazing, aquaculture, ozone, medical (with extra polishing) | High purity, large scale, liquid product, cylinder filling for resale |
| Scale | Small–medium, modular | Medium–very large |
| Running cost | Low — electricity + air only | Higher; more complex |
| Start-up | Minutes (PLC automatic) | Hours; skilled operation |
| Footprint | Compact skid | Large plant |
Rule of thumb: if you need a steady on-site supply at 93–95% purity and want the lowest running cost, PSA wins. If you need very high purity, liquid oxygen, or cylinders to sell, a cryogenic air-separation unit is the answer. IIGAS builds both and will tell you honestly which fits.
Why generate oxygen on site
- ✓No more cylinder deliveries, rentals, demurrage or supply interruptions — you make what you use.
- ✓Low operating cost: no fuel, only electricity and air; the zeolite lasts for years.
- ✓Fast payback where you currently buy bottled or liquid oxygen in any volume.
- ✓Reliable and automatic — PLC-controlled, skid-mounted, designed for Indian ambient conditions, ASME Sec VIII pressure vessels.
- ✓Scalable — add modules or a cylinder-filling booster as demand grows.
What industrial oxygen is used for
On-site PSA oxygen suits a wide range of uses: oxy-fuel cutting and welding, brazing and glass work, steel and foundry processes, aquaculture and fish farming, wastewater treatment and ozone generation, and — with additional purification to pharmacopoeia grade — medical oxygen for hospitals. The right purity and pressure depend on the application, which is part of what IIGAS specifies with you.