Method and apparatus for separating air

Method and apparatus of separating a nitrogen from a compressed and purified feed stream in a cryogenic rectification plant that employs a distillation column to produce a nitrogen-rich vapor as a column overhead and an oxygen-rich liquid column bottoms. Reflux is generated for the column by condensing part of the nitrogen-rich vapor within a down-flow heat exchanger. A stream of the oxygen-rich liquid column bottoms is introduced into an ejector which draws a stream of an oxygen-rich liquid phase produced from the outlet of a down-flow heat exchanger. The combined oxygen-rich liquid exiting the ejector is fed to the down-flow heat exchanger to condense the nitrogen-rich vapor. In such manner, part of the oxygen-rich liquid phase is recirculated to prevent dry-out of the down-flow heat exchanger outlet and to maintain effective condensation of the nitrogen-rich vapor.