Small Scale Cryogenic Nitrogen Plant
This model is built for sites where gas consumption isn't massive (50-1000 Nm³/h) but purity is non-negotiable. If you need oxygen content held steady under 3ppm, or if the plant wants some liquid nitrogen on hand for backup, a small scale cryogenic nitrogen plant is the only real answer. PSA can't hit that purity level reliably. Liquid nitrogen bulk tanks leave you exposed to delivery schedules and price swings. Unit ships on a skid. Level the ground, hook up power, water, and instrument air, wait 8-10 hours for cooldown, and you've got spec gas.
Basic Process Flow
Air side: Oil-free screw compressor pushes air to 0.7-0.9MPa → Chiller knocks temp down to 5-8℃ → Molecular sieve unit strips out H₂O and CO₂ completely (dew point below -65℃).
Cold box side: Clean air enters the brazed aluminum heat exchanger, crosses against returning cold nitrogen and waste gas, temp gets dragged down to roughly -170℃ → Feeds into the distillation column. Oxygen boils at -183℃, nitrogen at -196℃. Nitrogen goes up, concentrates at the top, gets drawn off as pure product. Cold losses are covered by the turboexpander; the booster end recovers a bit of expansion work on the side.
This small scale cryogenic nitrogen plant runs a standard low-pressure cycle. Cold box is packed with perlite for insulation. Outside of the box is ambient temp while the inside sits at -190℃. Valve switching, expander RPM, liquid levels-all monitored on the DCS. No one needs to stand there watching it.
Technical Specs
Actual numbers depend heavily on site conditions-altitude, cooling water inlet temp, voltage stability. Table below shows figures for standard design conditions.
| Parameter | Reference Value | Notes |
|---|---|---|
| N₂ Production Rate | 100 / 300 / 500 Nm³/h | Based on 0℃ standard conditions, customizable |
| N₂ Purity | ≤ 2ppm O₂ (by volume) | Real-time analyzer reading, oxygen level barely fluctuates |
| Cold Box Outlet Pressure | 0.5 - 0.7 MPa(G) | Low pressure from column; add a reciprocating compressor downstream if high pressure needed |
| Liquid N₂ Production | 5% - 8% of gas output | This liquid goes to storage tank, covers cold loss or fills cylinders |
| Temperature Range | -196℃ (liquid phase) to ambient +3℃ | Gas output temp stays close to ambient |
| Unit Power Consumption | 0.42 - 0.58 kW·h/Nm³ | This number covers air compressor, chiller, cooling water pump-everything |
| Startup Time | 8-10 hours | Pulling temp down from ambient to -170℃ can't be rushed |
| Continuous Run Time | 24+ months | No shutdown for defrost needed unless something trips offline |
Why Go Cryo Over PSA?
Purity Stability. A small scale cryogenic nitrogen plant uses physical separation. Once that column profile is steady, oxygen level at the top barely moves. PSA purity curves look like a sawtooth-they jump every time a valve cycles and as the sieve ages.
Backend Maintenance Cost. PSA valves cycle constantly. Over a few years, you're looking at valve replacements and sieve top-ups. Cryo gear costs more upfront, but once it's running, it's just routine checks. No frequent consumables to swap out.
Liquid Backup Capability. PSA can't do this at all. Being able to pull off a bit of liquid and store it gives real redundancy for lines that can't lose nitrogen flow-think bright annealing furnaces or chip encapsulation.
A Note on Operating Conditions
This gear isn't meant for frequent start-stop cycles. If you're only running two shifts a day or your gas demand swings wildly, you're better off with a bulk liquid tank or PSA. A small scale cryogenic nitrogen plant is built for continuous duty, high-purity applications. Cycling it on and off frequently is hard on the cold box and kills the energy efficiency numbers.
About Shenger Gas
We don't keep standard skids sitting in inventory. Each unit is designed around the user's specific delivery pressure, purity tolerance, and local climate. Details like the flow passage layout in the brazed aluminum heat exchanger, the acceptable leak rate on the mole sieve switching valves, whether to spec oil-bearing or gas-bearing for the expander-all of this gets sorted during the technical review phase. If you've got a specific gas consumption curve or site constraints, send it over. Shenger Gas will provide a preliminary utility consumption table and general arrangement suggestion first.
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