The invention discloses a novel external pressurized and internal liquefied pure
nitrogen preparation device which comprises a filter, a
turbine air compressor, an air pre-cooling unit, alternatively-used
molecular sieve adsorbers, an electric heater, a main
heat exchanger, a supercharging expansion
machine, a rectification column I, a rectification column II, a condensing
evaporator I, a condensing
evaporator II, a subcooler, a liquefier and a
supercharger. The invention also discloses a novel external pressurized and internal liquefied pure
nitrogen preparation method. According to the device and method,
sewage nitrogen reflux expansion
refrigeration is adopted, the pressure utilization efficiency is high, and the
energy consumption of the device is low; double
tower parallel nitrogen production is adopted, the upper
tower pressure can be higher or lower than the lower
tower pressure, and two nitrogen products with the same
pressure level or different pressure levels can be preparedsimultaneously, and some
liquid nitrogen products can be prepared; and an internal liquefier and an external
supercharger are arranged, the external
supercharger is located outside a cold box, maintenance and overhaul are facilitated, the internal liquefier is located inside the cold box, the cold loss is small, meanwhile, the selected type of the external supercharger is not limited, and therefore the application range of the device and the method can be greatly increased.