the present invention involves an efficient process for separating selected components of a gas stream by integrating a cryogenic separation unit and a membrane separation unit . two embodiments provide for the concurrent generation of an argon - rich stream in the gas or liquid phase , along with a nitrogen - rich product stream , both being produced from a stream normally comprising oxygen , nitrogen , and argon , e . g ., air . broadly , the novel system uses a membrane means to preferentially reject the oxygen component from the recycle stream of the cryogenic unit , concurrently accumulating the argon component to allow its separation as an argon - enriched product stream .