Eliminated from mechanical impurity by the air filter, the required amount of process air is compressed by air compressor to rated pressure. Afterwards, it goes into water-cooling tower for cleaning and pre-cooling. The removal of harmful components, such as moisture, CO2, C2H2 are carried out by activated alumina and molecule sieve in molecule sieve purifier, which will automatically alternate.
After purification, compressed air goes into main heat exchanger, and cooled down to its dew point temperature. Afterwards, it goes to lower column for primary rectification. In lower column, gas nitrogen is got the top of lower column, and then condensed into liquid nitrogen in evaporator-condenser. Part of liquid nitrogen is sent back to lower column as reflux. Balance liquid nitrogen and liquid air are sent into respective position of upper column via sub-cooler. Through secondary rectification, liquid oxygen is got at the bottom of upper column. After compression by liquid pump to rated pressure, liquid oxygen is warmed up ambient temperature, and delivered out of cold box into oxygen pipe as product. The waste nitrogen via sub-cooler goes to expander for expansion. Warmed up in heat exchangers, it is delivered out of cold box for purifying system for regeneration of molecular sieve.