Technical note on the parameters of compressed air for air separation plants
air separation equipment (air separation equipment) as the core device of industrial gas production, its operation needs to be matched with compressed air system as the source of feed gas supply. In order to ensure the separation efficiency and product quality, the compressed air shall meet the following basic parameters:
1. pressure demand range
the compressed air pressure requirements of the air separation plant are directly related to the separation process:
- conventional cryogenic air separation system: compressed air of 0.5-1.0MPa (gauge pressure) shall be provided, which can meet the requirements of gas liquefaction and distillation process
- pressure swing adsorption (PSA) air separation system: usually 0.3-0.8MPa compressed air, through pressure fluctuations to achieve gas adsorption and desorption
2. traffic matching principle
the compressed air flow shall be determined according to the capacity of the air separation plant:
- small oxygen/nitrogen plant (capacity <100Nm & sup3;/h): supporting air compressor flow is usually 120-150Nm & sup3;/h
- medium air separation system (capacity 100-1000Nm & sup3;/h): compressed air supply with flow rate 500-800Nm & sup3;/h
- large air separation plant (capacity> 1000Nm & sup3;/h): adopting multi-machine parallel connection scheme, the total flow can reach thousands of Nm & sup3;/h
3. Air Quality Standards
in order to avoid impurities affecting the separation efficiency, the compressed air must meet the following purification requirements:
- solid particle control: need to filter to 1μm below to prevent molecular sieve adsorbent blockage
- humidity management: dew point temperature should be reduced to -40 ℃ below, to avoid freezing in the cold box
- oil purification: oil content <0.01 mg/m & sup3;, to prevent catalyst poisoning
4. special process adaptation
- liquid air preparation: a pre-cooling system is required to reduce the compressed air temperature below 10°C
- high purity gas production (e. g. electronic grade oxygen): need to be equipped with activated carbon oil removal device and catalyst dehydrocarbon unit
the parameters described in this description are applicable to the compressed air system of conventional air separation plant, and the specific design needs to be dynamically adjusted according to the separation process, capacity scale and product purity requirements.
