Small Cryogenic Air Separation Unit

This small cryogenic air separation unit is designed based on actual medium-to-small gas consumption, not simply scaled down from a large plant. It is used for: cylinder filling, small chemical plants, food freezing, on-site gas supply for mines, electronics supporting gas, and hospital central oxygen supply. Typical requirements include producing both liquid oxygen and liquid nitrogen at the same time, skid-mounted, outdoor installation, and simple daily operation.

Air is compressed, then pre-cooled and purified to remove water, CO₂ and hydrocarbons. Otherwise they freeze and block the system at low temperature. Clean air goes into the main heat exchanger, cools down to below -170°C, then enters the rectification column. Nitrogen comes out from the top, oxygen or liquid oxygen from the bottom. The cold box is insulated and filled with perlite. More cold loss means higher energy consumption, no way around it.

elow is a common parameter range. Actual values depend on your working conditions:

This small cryogenic air separation unit can produce gas only, or both gas and liquid. Purified air temperature is normally 5–10°C. Rectification column operates between -173°C and -183°C. Ambient temperature range is -15°C to 45°C. It can sit outdoors without a separate building. If you are on a plateau, say above 3000m altitude, compressor selection and column conditions need to be recalculated.

Energy consumption is what users care about most. Take 200 Nm³/h oxygen at 99.6% purity as an example. Power consumption is about 0.45–0.55 kWh/Nm³ O₂. For nitrogen it is lower, around 0.18–0.25 kWh/Nm³ N₂. These are measured values under ISO conditions. If you need liquid oxygen or liquid nitrogen, or purity ≥99%, cryogenic is more efficient than PSA. If you only need 93% oxygen and no liquid, PSA is a better choice. We will tell you straight.

Customization depends on different situations. Higher altitude means adjusting the compression ratio. Higher cooling water temperature means larger heat exchange area. Different voltage and frequency mean changing the motor and VFD. Common custom options:

• Containerized skid, 20ft or 40ft
• Fully automatic PLC control with DCS interface, remote monitoring
• Pure nitrogen boost to above 8MPa
• Hydrogen-free argon production, but oxygen capacity needs to be ≥300 Nm³/h to be economical
• VFD compressor, saves power at partial load
• Special material heat exchanger for coastal or high-corrosion environments

We have ISO9001 and ISO14001. CE and ASME are available upon request. Services include process package design, P&ID review, on-site installation guidance, operator training, remote diagnosis, and spare parts supply. Training takes 3 to 5 days normally. Remote diagnosis response within 24 hours. We will suggest a list of wear parts, the rest as needed.

A common problem with small plants is copying large plant designs, which leads to high energy consumption, unstable operation, and frequent maintenance. Large plants have dedicated operators. Small plants may only have one or two people. So automation needs to be sufficient but not too complicated to repair. Expander selection is critical. A wrong selection adds 20% more energy consumption. Cold box sealing is another issue. Some manufacturers do not fill perlite properly. After six months the shell ices up and energy consumption keeps rising.

Shenger Gas has made specific optimizations on this small cryogenic air separation unit size, not just scaling down large plant drawings. In the 50 to 500 Nm³/h oxygen range, we solved these problems one by one. Every unit goes through cold and tightness testing before delivery, with real test curves. We match the expander ourselves. Perlite filling density and vibration times follow internal standards. Send us your working conditions: flow rate, purity, pressure, altitude, cooling water temperature, whether you need liquid. We calculate energy consumption, give you a proposal, and tell you the delivery date.

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