The invention discloses a pure
nitrogen preparation device. The device comprises a filter, a
turbine air compressor, an air pre-cooling unit, alternatively used
molecular sieve adsorbers, an electricheater, a supercharged aftercooler, a main
heat exchanger, an expansion
machine, a first rectifying
tower, a second rectifying
tower, a first condensation
evaporator, a second condensation
evaporator,a subcooler, a
liquid nitrogen pump and a cold box. According to the device, the cold flow needed by the device is prepared through expansion of pressured air, the air enters the second rectifying
tower to participate in rectification after being expanded to a certain pressure, the extraction rate is high, and the
energy consumption is low; or the air is expanded to the normal pressure, the pressure ratio is high, the refrigerating
capacity efficiency is high, the refrigerating capacity is large, the starting time of the device can be shortened, the
electricity consumption is saved, the extraction rate is higher, the
energy consumption is lower, the high-pressure
nitrogen is discharged out of the cold box after being reheated, the dirty
nitrogen in the mixed part is used for air regeneration of alternatively used
molecular sieve adsorbers, the
oxygen content in the regenerated dirty nitrogen is reduced, and the service life of the electric heater is effectively prolonged.