Industrial Air Separation Unit For Chemical Industry
The industrial air separation unit for chemical industry adopts proven cryogenic distillation technology to efficiently separate oxygen, nitrogen, and rare gases from air, and is suitable for continuous gas-demand scenarios such as large chemical parks, integrated refining–chemical complexes, coal-chemical plants, and ammonia synthesis units. The unit can operate under long-term full-load conditions to deliver oxygen, nitrogen, and instrument air with stable purity, providing a reliable basis for downstream oxidation, synthesis, protective atmospheres, and safety-related inerting processes.
Compared with bottled gases and liquid products delivered by tanker trucks, a cryogenic air separation package installed on site produces gas locally, reducing the impact of logistics and price fluctuations on production and helping chemical enterprises optimize long-term energy consumption and overall utility system configuration.
Product Scope and Configuration
This series of cryogenic air separation units is designed for medium and large chemical plants, with typical single-unit oxygen production capacity covering:
- Oxygen: 1,000–40,000 Nm³/h (≥99.5% O₂, available as gaseous or liquid product)
- Nitrogen: 1,000–50,000 Nm³/h (99.9–99.999% N₂)
- Cryogenic liquids: liquid oxygen, liquid nitrogen, and liquid argon configurable in required ratios
- Operating mode: continuous operation (typically designed for 8,000 h/year or more)
A typical packaged industrial air separation unit for chemical industry generally includes:
- Air compressor and downstream treatment system (precooling unit, air filters)
- Molecular sieve purification system (removal of moisture, CO₂ and hydrocarbon impurities)
- Main heat exchanger and cryogenic cold box (high- and low-pressure distillation columns, liquid-air/liquid-nitrogen reservoirs)
- Liquid storage tanks and pump skids (configured according to process requirements)
- Instrumentation and control system (DCS/PLC, analyzers, interlocks and protection)
- Utility interfaces (cooling water, circulating water, power supply, instrument air, etc.)
Principle and Structural Description
1. Process Principle (Cryogenic Distillation)
- The intake air is compressed and precooled, then sent to a molecular sieve purification system to remove moisture and CO₂, preventing freezing at low temperatures.
- The purified air is deeply cooled in a plate-fin heat exchanger to a temperature close to its liquefaction point.
- After expansion through a throttling valve or a turboexpander, a two-phase gas–liquid mixture is formed and fed into the high-pressure and low-pressure columns for staged rectification.
- By utilizing the differences in boiling points of oxygen, nitrogen and argon, multi-stage equilibrium separation is achieved inside the columns, producing high-purity oxygen, high-purity nitrogen, and crude/rectified argon products.
2. Main Structural Components
- Air compression section: Provides a stable inlet air pressure, typically in the range of 0.55–0.75 MPa (gauge).
- Air precooling and purification section: A chilled-water unit or closed-circuit cooling-water system combined with molecular sieve adsorber vessels to achieve dehumidification, CO₂ removal and hydrocarbon removal.
- Cryogenic cold box: Contains the main heat exchanger, high- and low-pressure distillation columns, liquid-air/liquid-nitrogen reservoirs, reboilers/condensers and other key equipment; it is the core of the entire unit.
- Liquid storage and pumping system: Configured with liquid oxygen, liquid nitrogen and liquid argon storage tanks and cryogenic pumps as required.
- Control and safety system: DCS/PLC, oxygen analyzers, dew-point meters, safety interlock systems and emergency shutdown systems.
Typical Product Specifications and Temperature Range
1. Typical Product Purity and Flow Rate
|
Product gas |
Purity range (vol.%) |
Typical flow range (Nm³/h) |
Outlet pressure (MPa, gauge) |
Outlet temperature (°C) |
|
Oxygen (gaseous) |
99.5–99.7% O₂ |
1,000–40,000 |
0.25–0.45 |
0 to +10 (adjustable) |
|
Oxygen (liquid) |
99.5–99.7% O₂ |
10–300 t/d (equivalent) |
Tank pressure 0.1–0.3 |
approx. -183 |
|
Nitrogen (gaseous) |
99.9–99.999% N₂ |
1,000–50,000 |
0.3–0.6 |
0 to +10 (adjustable) |
|
Nitrogen (liquid) |
99.9–99.999% N₂ |
10–300 t/d (equivalent) |
Tank pressure 0.1–0.3 |
approx. -196 |
|
Liquid argon |
≥99.99% Ar |
5–100 t/d (equivalent) |
Tank pressure 0.1–0.3 |
approx. -186 |
Note: The above are typical design ranges and can be customized according to the specific load and gas consumption profile of the chemical plant.
2. Typical Energy Consumption and Technical Parameters
|
Item |
Unit |
Typical range (reference) |
|
Overall power consumption per unit oxygen (≥99.5% O₂) |
kWh/Nm³ O₂ |
0.30–0.40 |
|
Specific power of air compressor |
kWh/Nm³ air |
≤ 0.11 |
|
Minimum operating temperature of cold box |
°C |
-180 to -196 |
|
Design operating load range |
% |
70–105 (load adjustable) |
|
Automation level |
- |
DCS/PLC fully automatic + remote monitoring |
|
Design continuous operation period (maintenance interval) |
months |
24–36 (depending on conditions and maintenance strategy) |
Technical Features and Engineering Highlights
- Uses plate-fin heat exchangers and a double-column distillation process, providing high heat-transfer efficiency with a relatively compact footprint.
- The molecular sieve purification system simultaneously removes moisture, CO₂ and part of the hydrocarbons to ensure long-term safe operation of the cold box.
- Can be integrated with variable-speed air compressors, evaporative cooling and cold-energy recovery schemes to reduce specific power consumption for oxygen and nitrogen production.
- Supports multiple product combinations, including pure oxygen, enriched oxygen, nitrogen and cryogenic liquids, allowing chemical plants to configure utilities flexibly.
- Key control points (top/bottom column analysis, purity, flow rate, dew point, etc.) are all monitored online and protected through interlocks.
Industrial Applications
In the chemical and refining industries, cryogenic air separation units mainly provide continuous gas supply for the following processes:
- Ammonia/urea plants: Supplying oxygen for syngas oxidation and inert nitrogen as protective gas.
- Ethylene, aromatics and downstream fine chemicals: Used for oxidation reactions, off-gas treatment and safety-related inerting.
- Coal-chemical and coal gasification projects: Providing large quantities of oxygen for staged air combustion, gasifiers and downstream processing units.
- Refineries and hydrotreating units: Used in off-gas treatment, sulfur recovery and nitrogen blanketing systems for explosion protection.
Selection Support and Engineering Services from Shenger Gas
When planning or upgrading utility systems for chemical plants, selecting an appropriate industrial air separation unit for chemical industry for a specific project requires comprehensive consideration of multiple factors, including plant scale, oxygen–nitrogen product ratio, load fluctuation, local electricity tariffs, and operation and maintenance strategy.
Shenger Gas has long specialized in industrial gases and air separation systems. Based on the gas consumption profiles of chemical parks and individual process units, we can assist with option comparison, technical parameter confirmation, energy-consumption evaluation, and engineering layout recommendations, providing owners with integrated solutions covering process package design, complete equipment supply, installation and commissioning, as well as training and maintenance support.
For further information on the configuration and application of cryogenic air separation units in the chemical industry, please feel free to contact the Shenger Gas technical team.
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