METHOD FOR THE CRYOGENIC SEPARATION OF AIR, AND AIR SEPARATION PLANT

A method for cryogenic separation of air is disclosed in which an air separation unit (100-300) with a rectification column arrangement (10) is used, the installation having a pressure column (11), a low pressure column (12), a crude argon column (13) and a pure argon column (14). In the method, boil-off gas from an overhead gas condensing plant (13.10) associated with the crude argon column (13) is partially or completely fed into the low-pressure column (12) in a first feed-in region, and boil-off gas from an overhead gas condensing plant (14.10) associated with the pure argon column (14) and excess liquid from the overhead gas condensing plant (14.10) are partially or completely fed into the low-pressure column (12) in a shared second feed-in region. In one embodiment, a flash gas formed during expansion of the cooling fluid into an overhead gas condensing plant (13.10) associated with the crude argon column (13) may be fed into the low pressure column (12) in a second feed region partially or completely and separately from the boil-off gas formed thereby. The invention also relates to a corresponding air separation unit (100-200).