Method for separating air by cryogenic distillation and installation therefor

The invention concerns a method for separating air by cryogenic distillation using an apparatus comprising a medium pressure column ( 9 ) and a low pressure column ( 11 ) thermally communicating, which consists in cooling an amount of compressed and purified air V in an exchange line ( 10 ) to a cryogenic temperature and conveying at least part of it to the medium pressure column, conveying oxygen- and nitrogen-enriched flows (LR, LP) from the medium pressure column to the low pressure column and drawing nitrogen- and oxygen-enriched flows ( 35, 23 ) from the low pressure column. The invention is characterized in that the medium pressure column operates between 6 and 9 bar abs and the ratio between the total amount of air V entering the exchange line and the total volume of the exchange line ranges between 3000 and 6000 Nm 3 /h/m 3 .