Nitrogen Generation
On-site N₂ for inerting, blanketing and purging — no more cylinders.
Nitrogen generators produce high-purity N₂ from compressed air using Pressure Swing Adsorption (PSA) with carbon molecular sieves, or hollow-fibre membranes.
How it works
- 1
Clean, dry compressed air enters the CMS bed under pressure.
Feed air must be clean and dry: oil-free or well-filtered compressed air at 7–8 bar, 1 µm and 0.01 µm coalescing filters, activated carbon, and a dryer giving −40 °C dew point. Oil or water reaching the carbon molecular sieve poisons it permanently — pre-treatment is the whole life of the machine.
- 2
Oxygen and moisture adsorb on the sieve; nitrogen passes through.
Inside the CMS vessel the sieve's pore size (~3 Å) lets the smaller, faster-diffusing oxygen molecules enter the micropores while nitrogen slips past. Oxygen, CO₂ and residual moisture are adsorbed under pressure; nitrogen leaves the top of the bed at product purity.
- 3
Second bed regenerates by depressurization.
As the online bed saturates, the second bed is vented to atmosphere. Dropping the pressure releases the adsorbed oxygen (this is the 'swing' in pressure swing adsorption) and regenerates the sieve with no heat and no consumables. A short pressure-equalisation step between beds recovers energy and steadies purity.
- 4
Beds alternate to give continuous N₂ flow into a buffer tank.
Solenoid or angle-seat valves swap the beds on a fixed cycle (typically 60–120 s) so product flow is continuous. The buffer tank absorbs the switch-over ripple, and an inline O₂ analyser diverts off-spec gas to vent until purity recovers. Higher purity means more air per unit of nitrogen — 95 % N₂ needs ~2.5 Nm³ air/Nm³, 99.999 % needs ~10.
Key components
Cyclone separator, 1 µm and 0.01 µm coalescing filters, activated carbon tower and a refrigerated + desiccant dryer chain. Target: <0.003 mg/m³ oil and −40 °C PDP. This is the single most important maintenance item on a PSA plant.
Twin carbon-molecular-sieve towers, snowstorm-filled and spring-loaded so the bed cannot fluidise and dust. Sieve life is 8–10 years if kept dry and oil-free; a sudden purity fall usually means bed dusting, channelling or contamination.
Fast-acting angle-seat or butterfly valves with pilot solenoids, sequenced by the PLC (adsorb → equalise → vent → repressurise). Millions of cycles per year — seat leakage is the most frequent purity fault, so the annual valve/seal kit is not optional.
Receiver downstream of the beds that smooths the cyclic delivery, holds pressure during bed switching, and provides surge capacity for intermittent large users (blanketing, purging, packaging).
Zirconia or electrochemical cell reading residual oxygen in ppm or %. Interlocked to a vent valve that dumps off-spec gas before it reaches the plant. Calibrate monthly with span gas; a drifting cell silently sends off-spec nitrogen to process.
Typical operating parameters
Problem solving videos
Safety notes
- •Asphyxiation hazard — N₂ displaces O₂ in confined spaces.
- •Install O₂ monitors in enclosed rooms.
- •Always vent to safe location.
Maintenance schedule
- •Monthly: check O₂ analyser calibration.
- •6-monthly: inlet coalescing/carbon filters.
- •Annual: valve cycle test, CMS life check.
Problem solving matrix
| Issue | Likely cause | Fix |
|---|---|---|
| Purity drop | Contaminated CMS / valve leak | Check pre-treatment, cycle valves |
| Low flow | High demand / low air pressure | Verify compressor & buffer |
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