Apparatus for separating air comprising a device for breaking up a jet of cryogenic liquid in a gas flow, comprising a supply pipeline for the cryogenic liquid having an inside diameter greater than or equal to 10 mm, and a gas pipe of circular section, with a diameter d, the gas pipe comprising a portion having a reduction in diameter by a ratio of 20 to 50% at the point of injection of liquid and over a distance y wherein:

y=nd

and wherein the supply pipeline penetrates the gas pipe such that its end is in the portion of the pipe having the reduction in diameter and n is between 7 and 9.

A method for separating air by cryogenic distillation is provided, in which, at least one portion of the first oxygen-enriched liquid is sent from a first column to a first vaporizer-condenser where it is partially vaporized in the form of a film at a pressure higher than the second pressure forming a second oxygen-enriched liquid constituting at least 30% of the oxygen-enriched liquid sent to the first vaporizer-condenser and a third oxygen-enriched gas, an argon-enriched fluid is sent from a second column to a third column and the fluid is separated in the column forming an argon-rich flow at the top of the column and an oxygen-rich flow at the bottom of the column and the third oxygen-enriched gas is expanded in a turbine with production of work.