Industrial Air Separation Unit

Shenger Gas focuses on cryogenic air separation and industrial gas engineering, providing industrial air separation unit solutions for the steel, chemical and energy sectors. For overseas users, we follow international standards such as ISO and ASME in equipment selection, process design and manufacturing control, in order to meet the demand of medium and large plants for safe, continuous and energy-efficient supply of oxygen, nitrogen and rare gases.

Product Positioning and System Configuration

An industrial air separation unit adopts cryogenic distillation technology: air is cooled down to its liquefaction temperature and then separated, yielding both gaseous and liquid oxygen, nitrogen and argon products. A typical system consists of:

• Inlet filtration and main air compressor system to provide a stable high-pressure air feed
• Molecular sieve purification unit for deep removal of moisture, CO₂, hydrocarbons and trace impurities
• Plate-fin heat exchangers and expansion turbine to provide efficient heat exchange and cryogenic refrigeration
• Cold box and distillation column system for low-temperature rectification of oxygen, nitrogen and argon
• Liquid storage tanks, vaporizers and pressure-reducing/regulating systems for product storage and distribution

Working Principle and Operating Characteristics

After compression, air enters the molecular sieve purification system where moisture and acidic impurities are removed. The purified air then passes through plate-fin heat exchangers and is cooled in counter-current flow against returning cold streams, with its temperature gradually reduced to near the liquefaction point.

A portion of the cooled air is expanded in an expansion turbine to perform work, generating the cryogenic refrigeration needed in the cold box. The liquefied air is separated in the primary and secondary distillation columns according to the differences in boiling points of each component. High-purity nitrogen is obtained at the top of the column, high-concentration liquid oxygen at the bottom, and crude argon can be withdrawn from an intermediate section and fed to the argon rectification system.

With automated control, this type of cryogenic air separation unit can operate stably over a wide load range, enabling multi-product co-production and continuous gas supply.

Energy Consumption and Automation Control

To reduce life-cycle cost, modern cryogenic ASUs place strong emphasis on overall energy efficiency and automation. By rationally distributing compression ratios, optimizing heat-exchange temperature differences, using high-efficiency expansion turbines and applying cold-energy recovery schemes, it is possible to lower specific energy consumption while maintaining product purity and load-following capability.

Control systems typically adopt integrated DCS/PLC architectures to achieve:

• Online monitoring and trend analysis of key parameters (purity, flow, pressure, liquid level, temperature)
• Start-up/shutdown sequence control and safety interlocks
• Load adjustment and economical operation modes at reduced night-time loads
• Remote diagnostics and operation & maintenance data recording for long-term optimization

Certification Standards and Design Codes

Equipment design and manufacturing can be tailored to the target market and user requirements by applying the corresponding standards, for example:

• Quality and safety management: ISO 9001, ISO 14001, ISO 45001 and related management systems
• Pressure vessels and piping: design and fabrication in accordance with ASME VIII, PED, GB and other applicable codes
• Electrical and control systems: compliance with IEC, CE and local electrical safety regulations
• Welding and non-destructive testing: execution in line with relevant welding qualifications and NDT standards, covering all critical pressure parts

Typical Industrial Applications

Industrial air separation units are widely used in steel, chemical, petrochemical, glass, coal-chemical, new energy and medical sectors, for example:

• Enriched oxygen for blast furnaces, BOF steelmaking and continuous casting protective gas systems
• Process oxygen supply for ethylene plants, ammonia synthesis, methanol production and oxidation reactors
• Glass furnace oxy-fuel boosting, protective and inerting gases for float glass production
• Oxygen, nitrogen and rare gas supply for coal gasification, IGCC and hydrogen-energy projects
• Regional medical liquid-oxygen stations and utility gas supply hubs for industrial parks

Operation, Maintenance and Life Cycle

With proper design and controlled operating conditions, modern cryogenic ASUs are typically designed for continuous run lengths of ≥24 months, and the cold box can operate for many years without opening for internal inspection. By using dual molecular-sieve beds with switching operation, redundant configuration of key valves and a structured maintenance strategy for online analyzers, the risk of unplanned shutdowns can be reduced.

Operation and maintenance focus on front-end purification performance, changes in heat-exchanger pressure drop, expansion turbine vibration and lubrication condition, as well as temperature and liquid-level profiles in the distillation columns. Combined with annual or major-overhaul inspections, these measures help maintain long-term stability in both energy consumption and product purity.

As a supplier of turnkey industrial gas and air separation equipment, Shenger Gas can adapt to the process requirements of different industries and plant scales, providing everything from scheme comparison and process-package design to complete-set manufacturing and commissioning support. If you are planning or upgrading an on-site gas supply system and wish to introduce a reliable industrial air separation unit to reduce your gas cost, you are welcome to contact the Shenger Gas engineering team for customized technical solutions and configuration recommendations for steel, chemical, energy and regional gas-station applications.

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