Abstract: Oxygen and nitrogen are produced by low-temperature separation of air in a rectification system that has a pressure column (4) and a low-pressure column (5). Charging air (1, 3) is introduced into pressure column (4). An oxygen-containing liquid fraction (8, 10) is removed from pressure column (4) and fed into low-pressure column (5). Gaseous nitrogen (17) from low-pressure column (5) is at least partially condensed in a top condenser (7) by indirect heat exchange with an evaporating cooling fluid (15). A nitrogen product stream (19) is removed from low-pressure column (5) and/or pressure column (4). An oxygen product stream (61, 62, 63) is pulled off from low-pressure column (5). The cooling fluid for top condenser (7) of low-pressure column (5) is formed by an intermediate liquid (15) that is drawn off from an intermediate point on low-pressure column (5).

Abstract: Oxygen and nitrogen are produced by low-temperature separation of air in a rectification system that has a pressure column (4) and a low-pressure column (5). Charging air (1, 3) is introduced into pressure column (4). An oxygen-containing liquid fraction (8, 10) is removed from pressure column (4) and fed into low-pressure column (5). Gaseous nitrogen (17) from low-pressure column (5) is at least partially condensed in a top condenser (7) by indirect heat exchange with an evaporating cooling fluid (15). A nitrogen product stream (19) is removed from low-pressure column (5) and/or pressure column (4). An oxygen product stream (61, 62, 63) is pulled off from low-pressure column (5). The cooling fluid for top condenser (7) of low-pressure column (5) is formed by an intermediate liquid (15) that is drawn off from an intermediate point on low-pressure column (5).

Abstract: 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.