Separation of natural gas mixtures

Claim 1

THE METHOD OF SEPARATING NATURAL GAS MIXTURES COMPOSED SUBSTANTIALLY OF NITROGEN AND METHANE AND OF RECOVERING GASEOUS METHANE THEREFROM UNDER SUBSTANTIAL PRESSURE THAT INCLUDES THE FOLLOWING STEPS: COMPRESSING THE MIXTURE TO A HIGH PRESSURE, COOLING THE COMPRESSED MIXTURE TO A LOW TEMPERATURE, THROTTLING THE MIXTURE TO AN INTERMEDIATE PRESSURE TO COOL IT FURTHER, RECTIFYING THE THROTTLED MIXTURE AT THAT INTERMEDIATE PRESSURE TO SEPARATE ITS CONTAINED NITROGEN AND METHANE, COOLING AND PARTIALLY LIQUEFYING THE NITROGEN RESULTING FROM SAID RECTIFICATION TO FORM LIQUID REFLUX FOR USE IN RECTIFYING THE MIXTURE, PARTIALLY WARMING THE UNLIQUEFIED PORTION OF THE COOLED NITROGEN BY USING IT AS A COOLING AGENT IN COOLING THE COMPRESSED MIXTURE, EXPANDING THE NITROGEN SO WARMED TO A LOWER INTERMEDIATE PRESSURE WITH PERFORMANCE OF EXTERNAL WORK TO RECOOL IT TO A LOWER TEMPERATURE THAN BEFORE, USING THE NITROGEN SO EXPANDED AS A COOLING AGENT IN EFFECTING SAID COOLING AND PARTIAL LIQUEFACTION OF NITROGEN, AGAIN EXPANDING THE ONCE-EXPANDED NITROGEN TO SUBSTANTIALLY ATMOSPHERIC PRESSURE WITH PERFORMANCE OF EXTERNAL WORK TO RECOIL IT TO A LOW TEMPERATURE, USING THE TWICE-EXPANDED NITROGEN SO RECOOLED AS A FURTHER COOLING AGENT IN EFFECTING SAID COOLING AND PARTIAL LIQUEFACTION OF NITROGEN, THEREAFTER USING SAID TWICE-EXPANDED NITROGEN TO COOL THE COMPRESSED MIXTURE, AND UTILIZING THE SEPARATED METHANE AT THE INTERMEDIATE RECTIFICATION PRESSURE TO COOL THE COMPRESSED MIXTURE.

Claim 2

THE METHOD OF SEPARATING NATURAL GAS MIXTURES COMPOSED SUBSTANTIALLY OF NITROGEN AND METHANE AND OF RECOVERING GASEOUS METHANE THEREFROM UNDER SUBSTANTIAL PRESSURE THAT INCLUDES THE FOLLOWING STEPS: COMPRESSING THE MIXTURE TO A HIGH PRESSURE, COOLING THE COMPRESSED MIXTURE TO A LOW TEMPERATURE, THROTTLING THE MIXTURE TO AN INTERMEDIATE PRESSURE TO COOL IT FURTHER, RECTIFYING THE THROTTLED MIXTURE AT THAT INTERMEDIATE PRESSURE TO SEPARATE ITS CONTAINED NITROGEN AND METHANE, COOLING AND PARTIALLY LIQUEFYING THE NITROGEN RESULTING FROM SAID RECTIFICATION TO FORM LIQUID REFLUX FOR USE IN RECTIFYING THE MIXTURE, PARTIALLY WARMING THE UNLIQUEFIED PORTION OF THE COOLED NITROGEN BY USING IT AS A COOLING AGENT IN COOLING THE COMPRESSED MIXTURE, EXPANDING THE NITROGEN SO WARMED TO A LOWER INTERMEDIATE PRESSURE WITH PERFORMANCE OF EXTERNAL WORK TO RECOOL IT TO A LOWER TEMPERATURE THAN BEFORE, USING THE NITROGEN SO EXPANDED AS A COOLING AGENT IN EFFECTING SAID COOLING AND PARTIAL LIQUEFACTION OF NITROGEN, AGAIN EXPANDING THE ONCE-EXPANDED NITROGEN TO SUBSTANTIALLY ATMOSPHERIC PRESSURE WITH PERFORMANCE OF EXTERNAL WORK TO RECOIL IT TO A LOW TEMPERATURE, USING THE TWICE-EXPANDED NITROGEN SO RECOOLED AS A FURTHER COOLING AGENT IN EFFECTING SAID COOLING AND PARTIAL LIQUEFACTION OF NITROGEN, THEREAFTER USING SAID TWICE-EXPANDED NITROGEN TO COOL THE COMPRESSED MIXTURE, AND UTILIZING THE SEPARATED METHANE AT THE INTERMEDIATE RECTIFICATION PRESSURE TO COOL THE COMPRESSED MIXTURE.