Double column system for the low-temperature fractionation of air.

摘要

The process and the apparatus serve for the low-temperature fractionation of air in a rectification system that has at least one pressure column and one low-pressure column. Feed air is compressed to a first pressure p1 in a first compressor, purified in a purification stage, cooled and at least in part introduced into the pressure column. At least one liquid fraction from the pressure column is fed into the low-pressure column. A nitrogen-rich fraction from the low-pressure column is warmed and mixed with feed air. The warmed nitrogen-rich fraction is mixed with the feed air downstream of the feed air purification stage. The mixture of feed air and nitrogen-rich fraction is further compressed in a second compressor to a second pressure p2 which is higher than the first pressure p1.