Separation of low boiling hydrocarbons and nitrogen by fractionation with product stream heat exchange

Abstract

Abstract SYSTEM FOR THE SEPARATION OF GASES, PARTICULARLY OF MIXTURE OF A LOW BOILING HYDROCARBON AND NITROGEN, E.G., A MIXTURE OF METHANE AND NITROGEN, WHICH INVOLVED PROVIDING A MIXTURE OF SUCH LOW BOILING HYDROCARBON AND NITROGEN AT RELATIVELY HIGH PRESSURE, E.G., ABOUT 1.000 P.S.I., COOLING THE COMPRESSED GAS MIXTURE TO A TEMPERATURE CLOSE TO ITS SATURATION TEMPERATURE, PASSING THE COOLED COMPRESSED MIXTURE IN HEAT EXHANGE RELATION WITH THE LOWER PORTION OF A FRACTIONATING COLUMN OPERATING AT A PRESSURE SUBSTANTIALLY LOWER THAN THE PRESSURE OF THE COMPRESSED GAS MIXTURE, AND PROVIDING REBOIL HEAT TO THE COLUMN. SUBCOOLING THE EXISTING COMPRESSED FEED GAS MIXTURE, REDUCING THE PRESSURE OF THE SUBCOOLED COMPRESSED MIXTURE APPROXIMATELY TO THE PRESSURE IN THE COLUMN, INTRODUCING THE RESULTING MIXTURE AS FEED INTO THE FRACTIONATING COLUMN, AND EFFECTING A SEPARATION OF THE MIXTURE IN THE COLUMN INTO A NITGOGEN FRACTION AND A HYDROCARBON FRACTION, PASSING OVERHEAD NITROGEN FROOM THE COLUMN IN HEAT EXCHANGE RELATION WITH THE COMPRESSED FEED MIXTURE FOR SUBCOOLING SAME, PREFERABLY WORK EXPANDING THE EXITING NITROGEN AND RECYLING THE EXPANDED NITROGEN AGAIN IN HEAT EXCHANGE RELATION WITH THE COMPRESSED FEED MIXTURE, WORK EXPANDING THE EXITING NITROGEN AND FURTHER COOLING SAME, WITHDRAWING LOW BOILING HYDROCARBON IN SUBSTANTIALLY PURE LIQUID FORM FROM THE LOWER PORTION OF THE COLUMN, PASSING A PORTION OF SUCH LIQUID HYDROCARBON IN HEAT EXCHANGE RELATION WITH THE WORK EXPANDED NITROGEN FOR SUBCOOLING SUCH HYDROCARBON, THROTTLING THE SUBCOOLED PORTION OF LIQUID HYDROCARBON AND FURTHER REDUCING THE TEMPERATURE AND PRESSURE THEREOF, EMPLOYING THE THROTTLED HYDROCARBON TO PROVIDE CONDENSING DUTY IN THE UPPER PORTION OF THE COLUMN, PASSING THE RESULTING EXITING VAPORIZED HYDROCARBON AND THE MAIN PORTION OF THE LIQUID HYDROCARBON WITHDRAWN FROM THE COLUMN IN HEAT EXCHANGE RELATION WITH THE COMPRESSED FEED MIXTURE FOR COOLING SAME, COMPRESSING THE HYDROCARBON PRODUCT TO DESIRED PRESSURE, AND PASSING NITROGEN WITHDRAWN FROM HEAT EXCHANGE REALATION WITH LIQUD HYDROCARBON, INTO HEAT EXCHANGE RELATION WITH THE COMPRESSED GAS MIXTURE FOR COOLING SAME.

Inventors

• 👤 Michael L Hoffman

Bibliographic Details