Method and unit for low-temperature air separation

A method for low-temperature air separation, in which an air separation unit with a first rectification column and a second rectification column is used, wherein

• the first rectification column is operated at a first pressure level and the second rectification column is operated at a second pressure level below the first pressure level,
• fluid which is oxygen-enriched compared to atmospheric air is drawn from the first rectification column in the form of one or more first material flows,
• at least one fraction of the fluid drawn from the first rectification column in the form of the one or more first material flows is heated in a heat exchanger,
• a fraction of the fluid heated in the heat exchanger is compressed using a compressor and returned to the first rectification column,
• a first fraction of the head gas of the first rectification column is condensed in the heat exchanger, and a second fraction thereof is discharged from the air separation unit in the form of at least one nitrogen-rich air product,
• additional fluid containing oxygen, nitrogen, and argon is drawn from the first rectification column and used as a second material flow or to form a second material flow which is transferred to the second rectification column, and
• an oxygen-rich sump liquid is formed in the sump of the second rectification column, and at least one fraction thereof is discharged in the form of a third material flow from the air separation unit, wherein
• a third rectification column is used, wherein the second rectification column and the third rectification column are designed as parts of a double column, the third rectification column is arranged below the second rectification column, and the third rectification column is supplied with air.