Low pressure noncryogenic processing for ethylene recovery

A process for recovering ethylene from a hydrocarbon gas feed stream containing components selected from the group consisting of hydrogen, nitrogen, methane, carbon monoxide, at least 5 mol % of ethylene, ethane, heavier saturated and unsaturated hydrocarbons and mixtures thereof which comprises:

• A. countercurrently contacting said hydrocarbon gas feed stream with a lean physical solvent selected from the group consisting of:
• 1) paraffinic solvents having molecular weights ranging from 75 to 140 and UOP characterization factors ranging from 12.0 to 13.5, said factors being independent of the aromatic content of said paraffinic solvents,
• 2) naphthenic solvents having molecular weights ranging from 75 to 130 and UOP characterization factors ranging from 10.5 to 12.0, said factors being independent of the aromatic content of said naphthenic solvents,
• 3) benzene, toluene, C.sub.8 -C.sub.10 aromatic compounds having methyl, ethyl or propyl aliphatic groups specifically constituting a subgroup of o-xylene, m-xylene, p-xylene, hemimllitene, pseudocumene, mesitylene, cumene, o-ethyltoluene, m-ethyltoluene, p-ethyltoluene, n-propylbenzene, isopropylbenzene, indane, durene, isodurene, prehnitene, crude xylenes, toluene transalkylation reaction effluents, extracted C.sub.9 naphtha reformates, C.sub.9 heart cuts of said reformates which are enriched in C.sub.9 alkylbenzenes, C.sub.7 -C.sub.9 alkyl aromatics, and mixtures thereof;
• and
• 4) dialkyl ethers of polyalkylene glycol, N-methyl pyrollidone, dimethylformamide, propylene carbonate, sulfolene and glycol triacetate,
• to produce an overhead stream which contains at least hydrogen and methane and an ethylene rich solvent bottoms stream having the methane content of final fractionated ethylene product corresponding to chemical grade ethylene of less than 5 mol % methane to polymer grade ethylene having its methane content ranging between 400 and 10 parts per million by weight, said countercurrent contacting taking place in a demethanizing-absorber column equipped with at least one reboiler and operating at pressures between 50 psig and 400 psig, and said lean physical solvent entering the top of the demethanizer-absorber column at 30 10.degree. F. to -40.degree. l F.;
• and
• B. regenerating the ethylene rich solvent in a distillation column equipped with at least one reflux condenser and at least one reboiler to produce ethylene plus hydrocarbon product as an overhead stream and said lean physical solvent as a bottom stream, said ethylene plus hydrocarbon product being suitable for bypassing a downstream demethanizer.