Feed air is compressed to a first pressure in a main air compressor. A first sub-stream of the air compressed to the first pressure is cooled and fed at least in part to the distillation column system. A second sub-stream of the air compressed to the first pressure is cooled and at least partially liquefied in a low-pressure column bottom evaporator. The at least partially liquefied second sub-stream is introduced at least in part into the distillation column system. A liquid oxygen-enriched fraction is introduced into the evaporation chamber of a high-pressure top condenser. An argon-containing oxygen stream from an intermediate point in the low-pressure column is introduced into an argon column. The second sub-stream is introduced at least in part into an argon top condenser and partially evaporated therein. The second sub-stream is then introduced at least in part into the high-pressure column and/or into the low-pressure column.

The invention relates to an air separation plant for cryogenic separation, said plant being designed to carry out a high-air-pressure process, wherein nitrogen is removed from the pressure column, expanded in a turbine that is coupled to a cold booster, and heated. Separately from the nitrogen which is removed from the pressure column, nitrogen is removed from the low-pressure column and heated to the same temperature. Before expansion in the turbine that is coupled to the cold booster, the nitrogen removed from the pressure column is heated to a temperature in a temperature range of 100 to 50 C. During expansion, the nitrogen cools down to a temperature in a temperature range of 150 to 40 C. and is then heated again. The invention also relates to a corresponding air separation plant.

An air separation device comprises: a main heat exchanger; a nitrogen rectification column; a nitrogen condensers disposed in a top portion of the nitrogen rectification column; a high-purity oxygen rectification column; and an oxygen evaporator disposed in a bottom portion of the high-purity oxygen rectification column. An oxygen-containing fluid discharged from an intermediate stage of the nitrogen rectification column is rectified in the high-purity oxygen rectification column and is concentrated in the bottom portion of the high-purity oxygen rectification column.