Method and appliance for obtaining nitrogen by cryogenic separation of air

摘要

The nitrogen separation plant comprises a double column (4) possessing a pressure column (5), a low pressure column (6) and a main condenser (14). The air is condensed, purified, cooled in a heat exchanger (2) and conveyed to a rectifier (4).At least one nitrogen product fraction (19) is extracted from the low pressure column, and a nitrogen gas fraction (20) removed from the top part of the low pressure column, and an oxygenated liquid (28) removed from the lower part of the low pressure column (12,11). The nitrogen gas fraction is heated upstream from the indirect heat exchanger, condensed (21,22) and re-cooled. The condensate formed from indirect heat exchange downstream from the indirect heat exchange is brought to the pressure of the low pressure column (27).