Firstly raw air got into air compressor, be compressed to required pressure, came into cooling unit to be cooled, and then enter into molecular sieve adsorber to get rid of water、CO₂、C₂H₂ and other impurity.

The purified air got into rectification column, through main heat exchanger to exchange heat with reflux waste gas and product nitrogen, be cooled and then came into bottom of rectifying column, be rectified to the product nitrogen and oxygen-enriched liquid air. The liquid air in column bottom be sub-cooled and throttled, then got into condensing evaporator to exchange heat with nitrogen, the nitrogen be liquefied and to be as the reflux liquid of rectification column.  

Product nitrogen be lead from the top of rectification column, through main heat exchanger to be reheated and then get out of cold box. Then the product nitrogen came into nitrogen compressor, be compressed to 30~50 bar and got into electrical heater, be heated to user required temperature and then be sent out of battery limited to user.

The waste gas be lead from the top of condensing evaporator, through main heat exchanger for reheating, and adiabatic expansion in turbine expander to compensate cooling capacity of the plant. The waste gas from expander through sub-cooler and main heat exchanger to be reheated, and then got out of cold box to be as the regeneration air of purification system.

The liquid nitrogen product be suction from condensing evaporator to liquid nitrogen storage tank, the liquid nitrogen be vaporized in vaporizer and then got into nitrogen pipeline to sent to user.