How PSA oxygen generation works
Ambient air is approximately 78% nitrogen, 21% oxygen and 1% other gases (mostly argon). PSA systems exploit the fact that zeolite molecular sieves preferentially adsorb nitrogen at elevated pressure. Compressed air passes through one of two vessels containing molecular sieve; nitrogen is adsorbed; oxygen passes through to a buffer tank at 93–95% concentration. Once the vessel is saturated, the system swings to the second vessel and the first is depressurised, releasing the adsorbed nitrogen back to atmosphere. This swing happens every 30–60 seconds in a continuous cycle. The result is a steady, on-demand supply of high-concentration oxygen with no consumable except compressed air and electricity.
Why PSA beats the alternatives
There are three ways to supply oxygen to an ozone generator: cylinder gas, liquid oxygen (LOX), or on-site PSA. Cylinder gas is acceptable for very small lab-scale ozone systems but uneconomic at any meaningful capacity — and the logistics of changing cylinders in a 24/7 operation are impractical. LOX requires a vacuum-insulated bulk storage tank, regular tanker deliveries, vapouriser controls and supply contracts; it makes sense at very high capacities (>2,000 Nm³/h equivalent) but for most industrial NZ applications the total cost of ownership is significantly higher than PSA. PSA is the sweet spot for the 1–100 Nm³/h range that covers most ozone installations: no deliveries, no contracts, no consumable beyond electricity, typically 5-year payback against LOX, and 10-year payback against cylinder gas.
PSA system components
A complete PSA package supplied by us includes: an oil-free or oil-removed compressed air supply (with redundancy options); refrigerated air dryer to remove water vapour; particulate and oil-coalescing filters; air receiver tank; the PSA module itself (twin molecular-sieve vessels with automatic switching valves); oxygen buffer tank; oxygen purity analyser with low-purity alarm and ozone-generator interlock; flow and pressure instrumentation; PLC control with HMI; and full SCADA integration. We size the compressed-air system, the PSA module and the buffer tank as a matched set — getting any one of them wrong destabilises the entire ozone system downstream. We also specify the molecular-sieve charge with appropriate over-sizing for the New Zealand climate (high humidity in coastal locations places extra demand on the air dryer).
Applications beyond ozone
While most of our PSA systems feed ozone generators, the same technology serves many other industrial applications in New Zealand. Aquaculture facilities use PSA oxygen directly for water oxygenation in high-density tanks and during fish transport. Medical facilities use higher-purity PSA (93%) oxygen for clinical applications. Glass and metal industries use PSA oxygen for combustion enhancement. Wastewater treatment plants use PSA-supplied oxygen to enrich activated sludge aeration and reduce footprint. We supply complete PSA systems for all these applications, often as standalone projects without an associated ozone generator.
Reliability, maintenance and energy
PSA systems are widely regarded as the most reliable industrial gas-generation technology available — there are no consumables other than the air dryer's refrigerant and the eventual molecular-sieve replacement (typically 7–15 years, depending on duty and inlet air quality). The control valves cycle millions of times in service and are designed for 5+ year intervals between rebuilds. Energy consumption is dominated by the air compressor — modern variable-speed compressors paired with right-sized PSA modules deliver power figures around 0.4–0.6 kWh per Nm³ of 93% O₂. We service the complete PSA package including compressor, dryer, filters, PSA valves and molecular sieve as part of our standard maintenance contracts. With proper service a PSA system will outlast the ozone generator it feeds.
