Method for separating air by cryogenic distillation

A method for separating air by cryogenic distillation, in which:

• i) a flow of air, which is compressed, purified and cooled, is sent to a first column operating under a first pressure where the flow of air separates forming a first oxygen-enriched liquid and a first nitrogen-enriched flow;
• ii) at least one portion of the first oxygen-enriched liquid is sent to a first vaporizer-condenser where the first oxygen-enriched liquid is partially vaporized at a pressure higher than a second pressure, thereby forming a second oxygen-enriched liquid and a third oxygen-enriched gas;
• iii) at least one portion of the first nitrogen-enriched flow is sent to a second column operating under the second pressure, lower than the first pressure;
• iv) a bottom of the second column is heated by a second bottom vaporizer-condenser;
• v) an argon-enriched fluid is sent from the second column to a third column and the argon-enriched fluid separates in the third column forming an argon-rich flow at a top of the third column and an oxygen-rich flow at a bottom of the third column;
• vi) the argon-rich flow condenses in the first vaporizer-condenser;
• and
• vii) the third oxygen-enriched gas is expanded in a turbine with production of work, optionally after heating,
• wherein the at least one portion of the first oxygen-enriched liquid that partially vaporizes in the first vaporizer-condenser is in the form of a film,
• wherein flow within the first vaporizer-condenser is co-current such that the second oxygen-enriched liquid and a portion of the third oxygen-enriched gas exit a lower portion of the first vaporizer-condenser, and the second oxygen-enriched liquid constitutes at least 30% of the at least one portion of the first oxygen-enriched liquid sent to the first vaporizer-condenser.