Process and apparatus for generating high-purity nitrogen by low-temperature fractionation of air

Apparatus for generating high-purity nitrogen by low-temperature fractionation of air, comprising:

• a rectification system for nitrogen/oxygen separation which has at least a first rectifier column (4),
• a line (1) to introduce compressed air into the rectification system,
• a cycle line (24, 25, 26, 27, 28, 29) for feeding gaseous cycle nitrogen out of an upper region of the first rectifier column (4) to a cycle compressor (30),
• means (34a, 36) for liquefying a first part (35) of the compressed cycle nitrogen,
• means (52) for introducing a nitrogen fraction into a high-purity nitrogen column (39), the high-purity nitrogen column having a top condenser (54),
• a product line for removing high-purity nitrogen (56) from the upper region of the high-purity nitrogen column (39),
• means for directly or indirectly introducing at least a part-stream of the liquefied cycle nitrogen into the evaporation space of the top condenser (54) of the high-purity nitrogen column, and
• means to remove oxygen from the rectification system.