Patent ID: 7818979
Filing Date: 2010-10-26
Classification: F25J

Abstract:
1. 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; b. separating the hydrocarbon feed stream into a first vapor stream and a first liquid stream; c. splitting the first vapor stream into a first separator overhead stream and a second separator overhead stream; d. 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, the demethanizer producing a demethanizer overhead stream containing a substantial amount methane and lighter components and a demethanizer bottoms stream containing a major portion of recovered ethane, ethylene, propane, propylene and heavier components; e. warming and compressing the demethanizer overhead stream to produce a residue gas stream; and f. wherein an improvement comprises the following: removing at least a portion of the residue gas stream as a residue gas reflux stream; combining the second separator overhead stream with the residue gas reflux stream to produce a combined reflux gas stream and then cooling and partially condensing the combined reflux gas stream to form a partially condensed combined reflux gas stream; supplying the partially condensed combined reflux gas stream to a reflux separator producing a reflux separator overhead stream and a reflux separator bottoms stream; supplying the demethanizer with the reflux separator bottoms stream as a third tower feed stream; and cooling, substantially condensing and then supplying the demethanizer with the reflux separator overhead stream as a fourth tower feed stream.