Separation of low molecular weight hydrocarbons from petroleum mixtures

Claim 1

IN A FRACTIONATION PROCESS FOR SEPARATING ETHANE AND ETHYLENE IN A PREDOMINANTLY C2 TO C4 HYDROCARBON FRACTION IN A UNITARY DISTILLATION ZONE CONTAINING A HIGH PRESSURE SECTION SEPARATED FROM A LOW PRESSURE SECTION BY A COMMON HEAT TRANSFER ZONE AND WHEREIN THE SAID PREDOMINANTLY C2 TO C4 FRACTION IS INITIALLY FED INTO THE HIGH PRESSURE SECTION, THE IMPROVEMENT WHICH COMPRISES THE STEPS OF WITHDRAWING FROM A LOWER PORTION OF THE HIGH PRESSURE SECTION A HEAVY RESIDUAL FRACTION CONTAINING PREDOMINANTLY C3 AND C4 HYDROCARBONS; WITHDRAWING FROM THE HIGH PRESSURE SECTION AN INTERMEDIATE SIDE STREAM FRACTION CONTAINING PREDOMINANTLY C2 HYDROCARBONS WITH A MINOR PROPORTION OF C3 HYDROCARBONS AND SENDING THIS FRACTION AS FEED TO THE LOW PRESSURE SECTION; WITHDRAWING A LIGHT LIQUID FRACTION CONDENSED ON THE PRESSURE SIDE OF THE SAID COMMON HEAT TRANSFER ZONE AND COMPRISING PREDOMINANTLY ETHYLENE AND CONTAINING SOME ETHANE FROM AN UPPER PORTION OF THE HIGH PRESSURE SECTION AS REFLUX TO THE LOW PRESSURE SECTION; WITHDRAWING A C2 AND HIGHER HYDROCARBON DISTILLATION RESIDUE STREAM FROM A LOWER PORTION OF THE LOW PRESSURE SECTION, THE C2 COMPONENT OF SAID DISTILLATION RESIDUE BEING PREDOMINANTLY ETHANE; AND TAKING OVERHEAD A PREDOMINANTLY ETHYLENE PRODUCT STREAM FROM THE LOW PRESSURE SECTION.