Demethanization in ethylene recovery with condensed methane used as reflux and heat exchange medium

Claim 1

A PROCESS FOR RECOVERING ETHYLENE FROM A GASEOUS MIXTURE CONTAINING: HYDROGEN, METHANE ETHYLENE, AND ETHANE COMPRISING: (A) PASSING SAID MIXTURE THROUGH A FIRST HEAT EXCHANGE ZONE WHEREIN SAID MIXTURE JIS COOLED BY INDIRECT HEAT TRANSFER TO CONDENSE A PORTION THEREOF; (B) SEPARATING SAID CONDENSED PORTION OBTAINED IN STEP (A) AND INTRODUCING SAID CONDENSED PORTION INTO A DEMETHANIZATION FRACTIONATION ZONE; (C) PASSING THE UNCONDENSED PORTION FROM STEP (A) THROUGH A SECOND HEAT EXCHANGE ZONE WHEREIN SAID UNCONDENSED PORTION IS COOLED BY INDIRECT HEAT TRANSFER TO CONDENSE ANOTHER PORTION; (D) PASSING THE CONDENSED PORTION FROM STEP (C) TO THE DEMETHANIZATION FRACTION ZONE; (E) PASSING THE UNCONDENSED PORTION FROM STEP (C) THROUGH SAID FIRST AND SECOND HEAT EXCHANGE ZONES TO EFFECT COOLING BY INDIRECT HEAT TRANSFER; (F) RECOVERING A METHANE RICH OVERHEAD FROM SAID FRACTIONATION ZONE; (G) COOLING THE METHANE RICH OVERHEAD TO CONDENSE A PORTION THEREOF; (H) RETURNING A PORTION OF THE CONDENSED METHANE RICH OVERHEAD TO THE DEMETHANIZATION FRACTIONATION ZONE AS REFLUX; (I) PASSING THE REMAINING PORTION OF THE CONDENSED METHANE RICH PORTION AND THE UNCONDENSED METHANE RICH OVERHEAD THROUGH THE FIRST AND SECOND HEAT EXCHANGE ZONES TO EFFECT COOLING BY INDIRECT HEAT TRANSFER; (J) RECOVERING THE BOTTOMS FROM SAID DEMETHANIZATION FRACTIONATION ZONE AND INTRODUCING SAID BOTTOMS INTO A SECOND FRACTIONATION ZONE; AND (K) RECOVERING AN ETHYLENE RICH OVERHEAD FROM THE SECOND FRACTIONATION ZONE.