Method and device for producing air gases in a gaseous and liquid form with a high flexibility and by cryogenic distillation

A method of producing at least one air gas using cryogenic distillation is provided. The expanded streams coming from the two turbines are combined and then split into two fractions. The first fraction is sent to the medium-pressure column of the system in gaseous form, whereas the second fraction is returned to the cold end of the heat exchange line. At a temperature T4 below −100° C. and above T2, the second fraction is sent to a turbine where it expands up to a temperature T5, forming an air stream. This air stream is then warmed in the heat exchange line before being discharged into the atmosphere, so that the distillation is not disturbed. A liquid product is withdrawn from the column system as final product. The sole liquid product from the apparatus is liquid oxygen, but of course other products may be produced.