Method of producing oxygen

Claim 1

A PROCESS FOR PRODUCING OXYGEN BY THE LIQUEFACTION AND RECTIFICATION OF AIR, WHICH COMPRISES, PASSING A STREAM OF AIR THROUGH A PATH IN A HEAT EXCHANGE ZONE CONTAINING AT LEAST THREE PATHS IN HEAT EXCHANGE RELATION WITH EACH OTHER, PASSING, ESPECTIVELY, STREAMS OF OYGEN AND NITROGEN PRODUCTS OF RECTIFICATION THROUGH THE OTHER PATHS IN SAID ZONE IN HEAT EXCHANGE RELATION WITH THE AIR PASSING THERETHROUGH, THEREBY COOLING THE AIR TO A TEMPERATURE WUCH THAT SUBSTANTIALLY ALL MOISTURE IS REMOVED THEREFROM, PASSING THE AIR FROM THE FIRST ZONE THROUGH A PATH IN A SECOND ZONE IN HEAT EXCHANGE RELATION WITH STREAMS OF OXYGEN AND NITROGEN PRODUCTS OF RECTIFICATION, COOLING AT LEAST ONE OF SAID STREAMS FLOWING BETWEEN SAID FIRST ZONE AND SAID SECOND ZONE, THE AMOUNT OF COLD THUS INTRODUCED BEING ADEQUATE TO COMPENSATE FOR COLD LOSSES RESULTING FROM THE DIFFERENCE IN ENTHALPY BETWEEN THE AIR INTRODUCED INTO AND THE PRODUCTS OF RECTIFICATION WITHDRAWN FROM THE PROCESS AND FOR HEAT LEAKS INTO THE SYSTEM, PASSING THE AIR FROM SAID SECOND ZONE THROUGH A PATH IN A THIRD ZONE IN HEAT EXCHANGE RELATION WITH STREAMS OF OXYGEN AND NITROGEN PRODUCTS OF RECTIFICATION, MAINTAINING TEMPERATURE CONDITIONS WITHIN SAID SECOND AND THIRD ZONES SUCH AS TO EFFECT SUBSTANTIALLY NO CONDENSATION OF CONDENSIBLE CONSTITUENTS IN THE AIR IN ITS PASSAGE THROUGH SAID SECOND ZONE AND THE SUBSTANTIALLY COMPLETE REMOVAL OF CARBON DIOXIDE FROM THE AIR IN ITS PASSAGE THROUGH SAID THIRD ZONE, ND PERIODICALLY REVERSING THE FLOW OF AIR AND NITROGEN THROUGH THEIR RESPECTIVE PATHS IN THE FIRST AND THIRD ZONES, THE AIR UPON REVERSAL FLOWING THROUGH THE PATHS THROUGH WHICH HAD PREVIOUSLY FLOWED THE NITROGEN AND THE NITROGEN FLOWING THROUGH THE PATHS THROUGH WHICH HAD PREVIOUSLY FLOWED THE AIR, WHEREBY UPON EACH REVERSAL THE NITROGEN SUBSTANTIALLY COMPLETELY REMOVES THE CARBON DIOXIDE DEPOSITED IN SAID THIRD ZONE AND THE FROST DEPOSITED IN SAID FIRST ZONE DURING THE PRECEDING STEP OF THE PROCESS.