Improved process for the separation of air to produce a desired separation product in the gaseous phase under pressure

Claim 1

A PROCESS FOR THE SEPARATION OF AIR TO PRODUCE OXYGEN IN THE GASEOUS PHASE UNDER PRESSURE COMPRISING THE STEPS OF (1) SEPARATING THE AIR AT LOW TEMPERATURE IN A RECTIFICATION ZONE, (2) WITHDRAWING THE OXYGEN AS A LIQUID FROM THE RECTIFICATION ZONE, (3) INCREASING THE PRESSURE ON SAID WITHDRAWN LIQUID OXYGEN, (4) VAPORIZING THE COMPRESSED LIQUID BY COUNTERCURRENT HEAT EXCHANGE IN TWO STAGE HEAT EXCHANGE STEP WITH A GASEOUS HEATING MEDIUM COMPRISING A PORTION OF THE AIR TO BE SEPARATED IN THE FIRST STEP WHICH AIR HAS BEEN COMPRESSED TO A PRESSURE HIGHER THAN RECTIFICATION PRESSURE, (5) A PART OF SAID GASEOUS HEATING MEDIUM BEING USED TO WARM A PART OF A SEPARATED NITROGEN FRACTION WITHDRAWN FROM SAID RECTIFICATION ZONE BY TWO-STAGE HEAT EXCHANGE, (6) SAID PART OF SAID HEATING MEDIUM USED FOR THIS PURPOSE BEING ADMIXED WITH THE GASEOUS HEATING MEDIUM HAVING THE FIRST STAGE OF THE LIQUID OXYGEN VAPORIZATION STEP, (7) SAID ADMIXED GASEOUS HEATING MEDIUM EXPANDED ISENTROPICALLY TO A PRESSURE INTERMEDIATE ITS INITIAL PRESSURE AND THE RECTIFICATION PRESSURE, (8) SAID AIR TO BE SEPARATED BEING COOLED IN SWITCH EXCHANGERS BY HEAT EXCHANGE WITH A PART OF THE SEPARATED NITROGEN FRACTION WHILE (9) THE REMAINDER OF THE AIR IS FURTHER COMPRESSED TO PROVIDE THE GASEOUS HEATING MEDIUM.