Abstract

The process and the apparatus are used to obtain argon using a three-column system for the fractionation of air, which has a high-pressure column (11), a low-pressure column (13) and a medium-pressure column (12). A first charge air stream (10, 64) is introduced into the high-pressure column (11), where it is separated into a first oxygen-enriched liquid and a first nitrogen top gas. A first oxygen-enriched fraction (23, 24, 26) from the high-pressure column (11) is introduced into the medium-pressure column (12), where it is separated into a second oxygen-enriched liquid and a second nitrogen top gas. A second oxygen-enriched fraction (33, 35), from the high-pressure column and/or from the medium-pressure column (12), is introduced into the low-pressure column (13), where it is separated into a third oxygen-enriched liquid and a third nitrogen top gas. An argon-containing fraction (68) from the low-pressure column (13) is introduced into a crude argon column (70), where it is separated into a crude argon top fraction and an oxygen-rich liquid. At least a part (73) of the crude argon top fraction (71) is passed into a crude argon condenser (29), where it is at least partially condensed by indirect heat exchange with at least a part (27) of the second oxygen-enriched liquid from the medium-pressure column (12). Oxygen-enriched vapour (32) which is formed in the process is returned to the medium-pressure column (12). A fraction (72) from the upper region of the crude argon column (70) and/or a part of the crude argon top fraction downstream of the crude argon condenser is obtained as crude argon product.