Oxygen is generated from Compressed air by a separation process which uses the principle of selective adsorption. The air is passed through a bed of Zeolite Molecular Sieves (ZMS) which has a property of very high degree of affinity to nitrogen
In this System, there are two adsorbers filled with ZMS, where nitrogen along with any traces of moisture are adsorbed and product gas (dry oxygen) comes out and passes to Oxygen Surge Vessel..
The pressure in the adsorbers swings from atmospheric pressure to line pressure, which is why this process is known as Pressure Swing Adsorption (PSA).