Separation of an oxygen-nitrogen mixture

Claim 1

A PROCESS FOR SEPARATING AN OXYGEN-NITROGEN MIXTURE COMPRISING THE STEPS OF PROVIDING AN OXYGEN-NITROGEN CONTAINING FEED GAS MIXTURE AT AMBIENT TEMPERATURE AND A FIRST HIGHER PRESSURE; CONTACTING THE FEED GAS WITH A PREVIOUSLY COOLED BED OF RECUPERATIVE MATERIAL THEREBY COOLING SUCH FEED GAS TO A FIRST SUBAMBIENT TEMPERATURE; FURTHER COOLING THE FEED GAS TO A SECOND LOWER SUBAMBIENT TEMPERATURE; CONTACTING THE FURTHER COOLED FEED GAS WITH A BED OF CRYSTALLINE ZEOLITIC MOLECULAR SIEVE MATERIAL HAVING APPARENT PORE SIZES OF AT LEAST 4.6 ANGSTROMS, THEREBY SELECTIVELY ABSORBING AT LEAST MOST OF SAID NITROGEN FROM THE GAS MIXTURE; DISCHARGING AN OXYGEN PRODUCT GAS FROM THE MOLECULAR SIEVE BED; AS A REGENERATION STROKE; TERMINATING THE FEED GAS-MOLECULAR SIEVE BED CONTACT, DRAWING THE COOLED NITROGEN DESORBATE GAS FROM SUCH BED IN A DIRECTION COUNTER-CURRENT TO THE PREVIOUS FEED GAS FLOW AND CONTACTING SUCH DESORBATE WITH THE RECUPERATIVE BED THEREBY RECOOLING SUCH BED FOR FURTHER CONTACTING WITH THE AMBIENT TEMPERATURE FEED GAS, SUCH DRAWING BEING OF SUFFICIENT DURATION AND MAGNITUDE TO REDUCE THE PRESSURE OF SAID MOLECULAR SIEVE BED TO A SECOND LOWER PRESSURE.