Patent ID: 8826692

Claim:
A method for the low-temperature separation of air in a distillation column system which comprises at least one high-pressure column and one low-pressure column, said method comprising: feed air is introduced into the distillation column system, wherein a first part of the feed air is introduced in the gaseous state into the distillation column system and a second part of the feed air is introduced in the liquid state into the distillation column system and the second part comprises at least 30 mol % of the total feed air amount, wherein: the distillation column system in addition comprises a precolumn, the operating pressure of which is higher than the operating pressure of the high-pressure column, a first substream of the feed air is introduced into the precolumn, the precolumn comprises a top condenser which is constructed as a condenser-evaporator having a condensation compartment and an evaporation compartment, a gaseous fraction from the upper region of the precolumn is introduced into the condensation compartment of the top condenser, liquid formed in the condensation compartment is applied at least in part as reflux to the precolumn, and a second substream of the feed air is introduced at least in part in the liquid state into the evaporation compartment of the top condenser.