Separation of mixtures of nitrogen and hydrocarbons

Abstract

Abstract METHOD AND SYSTEM PARTICULARLY DESIGNED FOR SEPARATING METHANE FROM MIXTURES OF NITROGEN AND METHANE, AND WHICH GENERALLY CONTAIN A MAJOR PROPORTION OF NITROGEN, WHICH INVOLVES, ACCORDING TO ONE EMBODIMENT, COOLING A COMPRESSED FEED MIXTURE, E.G., ONE CONTAINING 60% NITROGEN AND 40% METHANE, PASSING A MAJOR PORTION, E.G., 90%, OF THE COOLED COMPRESSED FEED MIXTURE INTO INDIRECT HEAT EXCHANGE RELATION WITH A FRACTIONATING COLUMN TO SUPPLY HEAT TO THE COLUMN, FURTHER COOLING THE REMAINING MINOR PORTION, E.G., 10%, OF THE COOLED COMPRESSED FEED MIXTURE, WITHDRAWING THE RESULTING COOLED MAJOR PORTION OF THE COMPRESSED FEED MIXTURE FROM HEAT EXCHANGE RELATION WITH THE COLUMN, COMBINING THE LAST-MENTIONED MAJOR PORTION OF THE COMPRESSED FEED MIXTURE WITH THE FURTHER COOLED MINOR PORTION OF THE COMPRESSED FEED MIXTURE, FURTHER COOLING THE RESULTING COMBINED COMPRESSED MIXTURE, REDUCING THE PRESSURE OF SUCH COMBINED COMPRESSED MIXTURE, INTRODUCING THE LAST-MENTIONED MIXTURE AS FEED INTO THE FRACTIONATING COLUMN, EFFECTING A SEPARATION OF THE LAST-MENTIONED MIXTURE IN THE COLUMN, WITHDRAWING HYDROCARBON IN SUBSTANTIALLY PURE LIQUID FORM FROM THE BOTTOM OF THE FRACTIONATING COLUMN, WITHDRAWING NITROGEN CONTAINING A MINOR PORTION OF HYDROCARBON, AS OVERHEAD VAPOR FROM THE FRACTIONATING COLUMN, AND PASSING SUCH OVERHEAD VAPOR INTO HEAT EXCHANGE RELATION WITH THE MINOR PORTION OF THE COMPRESSED MIXTURE AND WITH THE COMBINED COMPRESSED MIXTURE FOR FURTHER COOLING SAME AS AFORESAID. PREFERABLY, THE OVERHEAD VAPOR FROM THE FRACTIONATING COLUMN IS BROUGHT IN SEVERAL PASSES IN SERIES, IN HEAT EXCHANGE RELATION WITH THE MINOR PORTION OF THE COMPRESSED FEED MIXTURE AND WITH THE COMBINED COMPRESSED MIXTURE, EMPLOYING WORK EXPANSION FOLLOWING AT LEAST ONE OF SUCH PASSES FOR GREATER EFFICIENCY. THERE IS RECOVERED SUBSTANTIALLY PURE HYDROCARBON PRODUCT AT A PRESSURE CLOSE TO THAT OF THE FEED PRESSURE, AND BY ALLOWING SOME OF THE HYDROCARBON TO BE TAKEN OFF WITH THE OVERHEAD NITROGEN FROM THE COLUMN AND WHICH IS DISCARDED AS WASTE, SUBSTANTIALLY NO NET EXTERNAL POWER IS REQUIRED.

Inventors

• 👤 Michael L Hoffman

Bibliographic Details