Process 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 TWO ZONES IN SERIES, EACH OF SAID ZONES CONTAINING AT LEAST THREE PATHS IN HEAT EXCHANGE RELATION WITH EACH OTHER, PASSING RESPECTIVELY STREAMS OF OXYGEN AND NITROGEN PRODUCTS OF RECTIFICATION THROUGH TWO OTHER PATHS IN SAID ZONES IN HEAT EXCHANGE RELATION WITH THE AIR PASSING THERETHROUGH, COOLING AT LEAST ONE OF SAID STREAMS DURING ITS FLOW BETWEEN THE FIRST ZONE AND THE SECOND ZONE, WITH DRAWING THE AIR FROM THE SECOND ZONE AT A TEMPERATURE SUSH THAT SUBSTANTIALLY ALL CARBON DIOXIDE IN SAID AIR HAS BEEN REMOVED FROM THE AIR IN ITS PASSAGE THROUGH ITS PATH IN SAID SECOND ZONE, MAINTAINING THE TEMPERATURE DIFFERENCE BETWEEN THE TEMPERATURE OF THE AIR LEAVING AND THE WEIGHTED AVERAGE TEMPERATURE OF THE NITROGEN AND OXYGEN ENTERING SAID SECOND ZONE SO THAT IT FALLS WITHIN THE RANGE OR FROM ABOUT 5* TO ABOUT 10* F., PASSING THE AIR FROM SAID SECOND ZONE TO THE HIGH-PRESSURE STAGE OF A TWO-STAGE RECTIFICATION SYSTEM IN INDIRECT HEAT EXCHANGE RELATION WITH A RECTIFICATION PRODUCT FROM THE LOW-PRESSURE STAGE OF SAID SYSTEM, WITHDRAWING A MINOR PORTION OF THE NITROGEN FROM THE HIGH-PRESSURE STAGE, EXPANDING THE NITROGEN THUS WITHDRAWN TO COOL THE SAME, IMPARTING THE COLD THUS PRODUCED TO THE RECTIFICATION PRODUCTS ENTERING THE LOW-PRESSURE STAGE, PERIODICALLY REVERSING THE FLOW OF AIR AND NITROGEN THROUGH THEIR RESPECTIVE PATHS IN SAID 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 SECOND ZONE DURING THE PRECEDING STEP OF THE PROCESS.