Gas separation by plural fractionation with indirect heat exchange

Abstract

Abstract METHOD AND SYSTEM PARTICULARLY DESIGNED FOR SEPARATING METHANE FROM MIXTURES OF NITROGEN AND METHANE, WHICH INVOLVES, ACCORDING TO ONE EMBODIMENT, SEPARATING A MIXTURE OF METHANE AND NITROGEN IN AN INITIAL SEPARATION STAGE TO PRODUCE SAID NITROGEN VAPOR AND A METHANERICH LIQUID OF METHANE AND NITROGEN, FEEDING THE METHANERICH LIQUID TO A FRACTIONATING COLUMN IN HEAT EXCHANGE RELATION WITH THE INITIAL SEPARATION STAGE, WITHDRAWING METHANE IN SUBSTANTIALLY PURE FORM FROM THE BOTTOM OF THE FRACTIONATING COLUMN, SEPARATING A PORTION OF THE LASTMENTIONED LIQUID METHANE, SUBCOOLING THE SEPARATED PORTION OF LIQUID METHANE, THROTTLING THE SUBCOOLED LIQUID METHANE AND PASSING IT THROUGH A CONDENSER IN HEAT EXCHANGE RELATION WITH NITROGEN WITHDRAWN AS OVERHEAD FROM THE INITIAL SEPARATION ZONE, TO CONDENSE SUCH NITROGEN AND VAPORIZE THE METHANE, SUPPLYING CONDENSED LIQUID NITROGEN AS REFLUX TO THE TOP OF BOTH THE INITIAL SEPARATION ZONE AND FRACTIONATING COLUMN, AND PASSING NITROGEN VAPOR AND VAPORIZED METHANE FROM THE CONDENSER INTO HEAT EXCHANGE RELATION WITH LIQUID METHANE REFRIGERANT FOR SUBCOOLING SAME BEFORE THE LIQUID METHANE IS THROTTLED AND PASSED TO THE NITROGEN CONDENSER. THE NITROGEN AND METHANE VAPOR STREAMS FROM THE CONDENSER ARE ALSO PASSED IN HEAT EXCHANGE RELATION WITH THE METHANE-RICH LIQUID CONTAINING NITROGEN, FROM THE BOTTOM OF THE INITIAL SEPARATION ZONE PRIOR TO ITS BEING THROTTLED AND INTRODUCED AS FEED INTO THE FRACTIONATING COLUMN. ALSO, PREFERABLY THE VAPORIZED NITROGEN FORM THE CONDENSER IS BROUGHT IN SEVERAL PASSES IN SERIES, IN HEAT EXCHANGE RELATION WITH THE LIQUID METHANE REFRIGERANT FOR SUBCOOLING SAME, EMPLOYING WORK EXPANSION AFTER ONE OR MORE OF SUCH PASSES FOR GREATER EFFICIENCY. THE ASSOCIATED INITIAL SEPARATION ZONE AND MAIN FRACTIONATING COLUMN IN THE SYSTEM ARE OPERATED UNDER CONDITIONS TO EFFECT A "DIFFERENTIAL DISTILLATION IN THE COLUMN.

Inventors

• 👤 Michael L Hoffman

Bibliographic Details