Method for cooling a gaseous mixture to a low temperature

Claim 1

IN A METHOD FOR COOLING A GASEOUS MIXTURE TO LOW TEMPERATURE AND PRODUCING AT LEAST ONE CONSTITUENT OF THIS MIXTURE IN LIQUID PHASE, COMPRISING SUBJECTING A FIRST GASEOUS MIXTURE TO A FRACTIONATE CONDENSATION IN A PLURALITY OF HEAT-EXCHANGE STAGES WITH AT LEAST ONE OF THE CONDENSED FRACTIONS BEING EXPANDED TO A FIRST PRESSURE AND VAPORIZED IN HEAT EXCHANGE WITH SAID FIRST GASEOUS MIXTURE UNDERGOING FRACTIONATE CONDENSATION, EXPANDING TO A SECOND PRESSURE SAID AT LEAST ONE CONSTITUENT AFTER ITS CONDENSATION AND WITHDRAWING SAID EXPANDED CONSTITUENT AS PRODUCT, SAID FIRST PRESSURE BEING SUBSTANTIALLY HIGHER THAN SAID SECOND PRESSURE, THEREAFTER RECOMPRESSING SAID AT LEAST ONE FRACTION TO A THIRD PRESSURE SUBSTANTIALLY HIGHER THAN SAID FIRST PRESSURE, AND RECOMBINING SAID RECOMPRESSED FRACTION WITH SAID FIRST GASEOUS MIXTURE; THE IMPROVEMENT COMPRISING PROGRESSIVELY COOLING A SECOND GASEOUS MIXTURE IN A PLURALITY OF HEAT-EXCHANGE STAGES WITH SAID FIRST MIXTURE, SAID SECOND MIXTURE HAVING THE SAME MAIN COMPONENTS AS SAID FIRST MIXTURE, AND MAINTAINING SAID FIRST GASEOUS MIXTURE WITH SAID SECOND GASEOUS MIXTURE SEPARATE AT LEAST UNTIL THEY ARE UNDER CONDITIONS OF TEMPERATURE AND PRESSURE SUCH THAT SAID CONSTITUENT TO BE PRODUCED IN LIQUID PHASE IS AT LEAST MOSTLY CONDENSED WITHIN SAID SECOND GASEOUS MIXTURE AND SAID AT LEAST ONE CONDENSED FRACTION HAS BEEN WITHDRAWN FROM SAID FIRST GASEOUS MIXTURE FOR EXPANSION AND VAPORIZATION.