Three-column system for the cryogenic air separation with argon recovery

The method and apparatus are used for cryogenic air separation of air in a rectification system for nitrogen-oxygen separation, having a high pressure column (9), a low pressure column (11) and a medium pressure column (10) and also with a crude argon column (63) is. At least one feed air stream is introduced into the rectification system for nitrogen-oxygen separation (8, 19, 21). The low pressure column (11), at least one oxygen or nitrogen product stream (52, 54, 58) removed. At least one first argon-enriched stream (59, 61) is removed from the rectification system for nitrogen-oxygen separation and fed to the crude argon column (63). The crude argon column (63) is removed from an argon-rich fraction (75), whose argon content is greater than that of the first argon enriched stream (59, 61). The first argon enriched stream (59, 61) is removed from the medium pressure column (10).