Method of separating gaseous mixtures

Claim 1

IN THE METHOD OF TREATING AIR WHEREIN A STREAM OF COMPRESSED AIR, CONTAINING CARBON DIOXIDE AS AN IMPURITY, IS PASSED IN ONE DIRECTION OF FLOW THROUGH A REVERSING HEAT EXCHANGE ZONE IN HEAT EXCHANGE RELATION WITH RELATIVELY COOL COUNTERFLOWING FLUID, OBTAINED FROM THE AIR IN A LATTER STAGE OF TREATMENT AND NOT GREATER IN MASS QUANTITY THAN SAID STREAM OF AIR, TO EFFECT COOLING OF THE AIR AND RESULTANT PRECIPITATION OF THE IMPURITY IN A COLDER PORTION OF THE HEAT EXCHANGE ZONE, AND WHEREIN THE STREAM OF AIR AND A SECOND GASEOUS STREAM COMPRISING AT LEAST A PORTION OF SAID COUNTERFLOWING FLUID AND SUBSTANTIALLY FREE OF THE IMPURITY AND AT LOWER TEMPERATURE THAN SAID COLDER PORTION ARE ALTERNATED ONE WITH THE OTHER IN TWO PATHS OF THE HEAT EXCHANGE ZONE WHEREBY THE SECOND GASEOUS STREAM PASSES OVER PRECIPITATED IMPURITY AND EVAPORATES IT, AND FURTHER WHEREIN A PART OF THE STREAM OF COOLED AIR IS SUBJECTED TO EXPANSION WITH PRODUCTION OF EXTERNAL WORK AND ANOTHER PART IS SUBJECTED TO SUBSEQUENT TREATMENT IN COMPRESSED CONDITION; THE IMPROVEMENT WHICH COMPRISES COOLING THE STREAM OF COMPRESSED AIR IN THE HEAT EXCHANGE ZONE TO A TEMPERATURE BELOW THE PRECIPITATION TEMPERATURE OF THE IMPURITY, REMOVING THE STREAM OF COOLED AIR FROM THE HEAT EXCHANGE ZONE, PASSING A FLUID STREAM OF COOLED AIR, IN COUNTERCURRENT HEAT EXCHANGE WITH SAID STREAM OF COMPRESSED AIR THROUGH A SEPARATE PATH IN THE HEAT EXCHANGE ZONE DISPOSED IN HEAT EXCHANGE RELATION WITH AT LEAST A PART OF SAID COLDER PORTION WHEREBY SAID FLUID STREAM IS WARMED BY ADDITIONALLY COOLING SAID STREAM OF COMPRESSED AIR TO MAINTAIN A DIFFERENCE BETWEEN THE