Patent ID: 7856847

Claim:
A process for separating a gas stream containing methane and ethane, ethylene, propane, propylene and heavier components into a volatile gas fraction containing a substantial amount of methane and a less volatile fraction containing a large portion of ethane, ethylene, propane, propylene and heavier components, the process comprising the steps of: a. splitting a hydrocarbon feed stream into a first inlet stream, a second inlet stream and a third inlet stream and cooling the first, second, and third inlet streams; b. supplying the first inlet stream and the second inlet stream to a cold separator; c. separating the first inlet stream and the second inlet stream to produce a first vapor stream and a first liquid stream; d. expanding the first vapor stream to produce an expanded first vapor stream and then supplying a demethanizer with the first liquid stream as a first tower feed stream and the expanded first vapor stream as a second tower feed stream; e. cooling and at least partially condensing the third inlet stream and then supplying a reflux separator with the third inlet stream and producing a reflux separator overhead stream and a reflux separator bottoms stream; f. supplying the demethanizer with the reflux separator bottoms stream as a third tower feed stream; g. cooling and substantially condensing and then supplying the demethanizer with the reflux separator overhead stream as a fourth tower feed stream, the demethanizer producing a demethanizer overhead stream containing a substantial amount of methane and lighter components and a demethanizer bottoms stream containing a major portion of recovered ethane, ethylene, propane, propylene and heavier components; h. warming and compressing the demethanizer overhead stream to produce a residue gas stream; and i. wherein an improvement comprises removing at least a portion of the residue gas stream as a residue gas reflux stream and cooling, substantially condensing and then supplying the residue gas reflux stream to the demethanizer as a reflux stream.