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Small Cryogenic Air Separation Units for High-Purity Oxygen & Nitrogen

Our small cryogenic air separation units (ASUs) are designed to produce high-purity gaseous oxygen, nitrogen, or both gases simultaneously through cryogenic distillation. With integrated air compression, molecular sieve purification, turboexpander refrigeration, and rectification systems, these plants provide a reliable gas supply for industrial manufacturing, metal processing, chemical production, and industrial gas distribution.

Small Cryogenic Air Separation Unit
A small cryogenic air separation unit (ASU) is a modular, engineering-grade plant that generates gaseous oxygen, nitrogen, and optional argon directly on-site. Designed to replace bulk liquid...
PSA Nitrogen Generation Equipment
The Pressure Swing Adsorption (PSA) Nitrogen Generation Equipment is an on-site nitrogen production system that separates nitrogen from compressed air using Carbon Molecular Sieve (CMS) adsorption...
Membrane Separation Nitrogen Generation Equipment
Membrane separation nitrogen generation equipment produces industrial-grade nitrogen directly from compressed air through selective gas permeation. Designed for continuous on-site operation, these...

Technical Specifications

Specific power includes the air compressor, pre-cooling unit, and molecular sieve regeneration heater, and excludes product boosters. Values are confirmed in the contract guarantee.

Parameter	Specification
Product Options	High-purity O₂, N₂, or O₂ + N₂ dual production
Capacity Range	50–500 Nm³/h O₂ (standard models)
Supply Scope	Air compressor, pre-cooling unit, molecular sieve purifier, cold box, heat exchanger, distillation column, PLC control
O₂ Purity	99.6% standard (95% optional industrial oxygen)
N₂ Purity	≤ 10 ppm O₂ standard; ≤ 5 ppm O₂ optional
Specific Power Consumption	0.60–0.75 kWh/Nm³ O₂ at 200 Nm³/h; 0.50–0.60 kWh/Nm³ O₂ at 500 Nm³/h (99.6% O₂, 0.02–0.05 bar(g) at cold box outlet, no liquid production)
Gas Moisture	Dew point below −60°C after purification
Product Gas Pressure at Cold Box Outlet	0.02–0.05 bar(g)
Booster Pressure	Optional 15–30 bar(g) pipeline supply / 150 bar(g) cylinder filling
Startup Time	12–24 hours to reach stable purity
Operating Conditions	20°C, 101.3 kPa(a), 65% RH reference
Turndown Range	70–105% of rated O₂ output at stable purity
Environmental Range	−10°C to +40°C; standard ≤1000 m altitude
Safety System	Automatic off-spec gas diversion and PLC protection logic

Cryogenic ASU vs. PSA and Membrane Technologies

Cryogenic Distillation

Typically advantageous above 300–500 Nm³/h O₂, or when the project needs 99.5%+ oxygen purity, liquid products (LOX, LIN, LAR), or simultaneous O₂ and N₂ supply. Below 300 Nm³/h, cryogenic specific power is higher and PSA is usually the lower-cost route.

Pressure Swing Adsorption (PSA)

Optimal for lower capacity or medium purity applications (90–95% O₂; 95–99.99% N₂), intermittent operation, and rapid startup needs.

Membrane Separation

Optimal for low-to-medium purity nitrogen requirements (95–99%) at variable flow rates.

Technology Selection Criteria

Final process route selection depends not only on nominal capacity thresholds but also on required product purity, delivery pressure, turndown flexibility, operating hours, backup requirements, and overall lifecycle cost (LCC) analysis.

Main Process Sequence

Process air intake
Dust filtration
Air compression
Mechanical pre-cooling
Molecular sieve purification
Turboexpander expansion
Dual-column rectification
Product gas delivery (direct from the cold box, or via an oxygen/nitrogen booster)

Equipment Execution

Air Compressor & Pre-Cooling: Industrial screw or centrifugal air compressor combined with an air-water cooling tower or refrigerant chiller to remove bulk moisture before adsorption.

Molecular Sieve Purifier: Dual-bed temperature swing adsorption (TSA) system using synthetic zeolite and alumina media to remove moisture, CO₂, and hydrocarbons.

Cold Box Enclosure: Weatherproof structural steel enclosure filled with expanded perlite insulation to maintain cryogenic operating temperatures.

Turboexpander: High-efficiency expansion turbine providing refrigeration through adiabatic expansion. Depending on configuration, the expander uses air-bearing or oil-lubricated bearing systems, with low oil pressure ESD protection applied to oil-lubricated designs.

Instrumentation & Controls: PLC-based control system with industrial HMI. Emergency shutdown (ESD) functions protect against critical conditions including expander overspeed, low lube oil pressure (oil-lubricated units), and high compressor discharge temperature.

Membrane Separation Nitrogen Generation Equipment

Utility Connection Requirements

Cooling Water: Continuous clean water circulation or closed-loop cooling system for compressor coolers.

Instrument Air: Clean, dry compressed air at 0.6 MPa (6.0 bar) for pneumatic valve operation.

Electrical Power: 380 V / 415 V / 440 V, 3-phase, 50 Hz / 60 Hz supply. Voltage tolerance shall comply with project requirements.

Site Design Conditions: Standard design supports elevations up to 1000 m ASL and ambient temperatures from −10°C to +40°C. Special conditions require revised heat exchanger and equipment sizing.

Safety Requirements: Oxygen service piping requires oil-free cleaning and assembly. Nitrogen installation areas require mechanical ventilation and continuous O₂ monitoring to prevent oxygen-deficiency hazards.

Customization

Engineering Modifications

Customized solutions are available for high-altitude sites (>1000 m ASL), tropical or desert environments, coastal corrosion protection, and classified electrical areas (including optional ATEX/IECEx components).

Packaging Formats

Available as skid-mounted modules, modular steel structures, or weatherproof outdoor enclosures.

Engineering Deliverables

Engineering Phase

PFD, P&ID, GA drawings, foundation loading data, and electrical single-line diagrams.

Delivery Phase

As-built drawings, pressure vessel certificates, factory test records, O&M manuals, and PLC backups.

Quality Testing

Factory Acceptance Testing (FAT)

Hydrostatic testing of applicable pressure vessels.
NDE inspection of critical pressure-containing welds.
Leak testing and control system loop checks.

Site Acceptance Testing (SAT)

Conducted after installation and cold box cooldown.
Performance verification includes flow capacity, product purity, and specific power consumption.
Test results are corrected according to contractual adjustment curves when site conditions differ from reference conditions.
Third-party inspection by SGS, TÜV, or Bureau Veritas can be arranged upon agreement.

FAQ

Q: How does on-site ASU oxygen cost compare with delivered liquid oxygen?

A: At USD 0.08/kWh and 0.55 kWh/Nm³, electricity for a 300 Nm³/h plant costs about USD 31 per tonne of oxygen, compared with USD 150–300 per tonne for delivered liquid oxygen.

Q: How long does a hot restart take after a short trip?

A: After a trip of less than 2–4 hours, a hot restart typically returns to on-spec purity within 2–4 hours. A cold start takes 12–24 hours.

Q: How much nitrogen can I produce while running oxygen at full load?

A: A 200 Nm³/h O₂ plant can typically produce 200–400 Nm³/h of gaseous nitrogen at ≤10 ppm O₂.

Q: How many operators are required?

A: A small skid-mounted ASU typically needs one operator per shift or remote monitoring after commissioning.

Q: What does a budgetary offer include?

A: Provide the required O₂ and N₂ flow, purity, delivery pressure, site temperature, and elevation.

Q: What warranty do you provide?

A: The standard warranty covers design, material, and workmanship for 12 months after commissioning or 18 months after shipment, whichever comes first.

Q: How much floor space and building height are required?

A: A 200 Nm³/h plant typically requires 300–500 m², including the compressor, cooling system, and cold box. The cold box is usually 12–18 m high.

Q: How is the cold box shipped?

A: The cold box typically ships as one module, approximately 2.5–3.5 m in diameter and 10–15 m long, on a flat-rack or special trailer.

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