Patent ID: 7484385

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