NOVELTY - Process (P1) for separating butenes and butanes involves contacting hydrocarbon mixture comprising butanes and butenes with lean solvent mixture comprising water and polar solvent in extractive distillation column; recovering an overheads fraction comprising butanes from the column; recovering enriched solvent fraction as bottoms fraction from the column; feeding bottoms fraction to stripper (52) to separate the butenes; recovering the lean solvent mixture; recovering and condensing the overheads fraction; and feeding water as reflux to top of the stripper wash section.    USE - For separating butenes and butanes by extractive distillation using a polar solvent (claimed).    ADVANTAGE - The process addresses the problem of separate liquid phases that form at the top of the stripper. The decline in separation efficiency that would be a result of separate liquid phases is therefore avoided. Additionally, make-up water is introduced at the optimal point in the process. The introduction of make-up water at the top of the stripper, instead of into the lean solvent recycle stream, enhances the separation of solvent from the butene product. Further, the method is highly energy efficient; the utilization of the enthalpy of the lean solvent recycle may be maximized. Several wash trays (such as about 10-15) are used above the stripper stages (packed beds), where the entire stripper overheads are washed with condensed water/solvent. Butenes are not refluxed back to the stripper. As a result, the amount of solvent in the stripper overheads and in the water reflux is greatly reduced. This results in a superior butenes product as well as less solvent losses. Also method has a lower solvent to feed ratio as compared to typical butane/butene separation processes. As a result of the improved tray efficiency of the stripper wash trays, improved overall absorption and stripping efficiency, improved heat integration and energy recovery, and lower solvent rate, process may have lower operating expenses and lower capital costs as compared to prior butane/butene separation schemes.    DETAILED DESCRIPTION - Process (P1) for separating butenes and butanes by extractive distillation using a polar solvent, involves contacting a hydrocarbon mixture comprising butanes and butenes with a lean solvent mixture comprising water and at least one polar solvent in an extractive distillation column to form an enriched solvent fraction comprising the butenes and solvent(s); recovering an overheads fraction comprising butanes from the extractive distillation column; recovering the enriched solvent fraction as a bottoms fraction from the extractive distillation column; feeding the bottoms fraction to a stripper (52) comprising a stripping section and a wash section to separate the butenes from the solvent mixture; recovering the lean solvent mixture as a bottoms fraction from the stripper; recovering a stripper overheads fraction comprising butenes and water from the stripper; condensing the overheads fraction to form a water fraction and a product butenes fraction; feeding water as a reflux to a top of the stripper wash section; feeding at least a portion of the condensed water fraction intermediate the top and bottom of the stripper wash section as a second reflux. An INDEPENDENT CLAIM is included for system for separating butenes and butanes by extractive distillation using a polar solvent, comprising: an extractive distillation column for contacting a hydrocarbon mixture comprising butanes and butenes with a lean solvent mixture comprising water and polar solvents to recover an enriched solvent fraction comprising the butenes and solvent(s) as a bottoms fraction and to recover an overheads fraction comprising the butanes; a stripper comprising a lower stripping section and an upper wash section to separate the bottoms fraction and recover an overheads fraction comprising butenes and water and a bottoms fraction comprising the lean solvent mixture; a stripper overheads system for condensing the overheads fraction to form a water fraction and a product butenes fraction; a flow conduit for feeding water as a reflux to a top of the stripper wash section; a flow conduit for feeding at least a portion of the condensed water fraction intermediate the top and bottom of the stripper wash section as a second reflux.    DESCRIPTION OF DRAWING(S) - The figure shows a simplified flow diagram of a process for separating butenes from butane.    Feed vaporizer (6)    Butane absorber (12)    Drum (24)    Butane product (30)    stripper (52)