Solvent extraction process

Claim 1

IN A SOLVENT EXTRACTION PROCESS FOR THE SEPARATION OF AN AROMATIC HYDROCARBON FROM A MIXTURE THEREOF WITH A NON-AROMATIC HYDROCARBON WHEREIN SAID MIXTURE IS CONTACTED IN A SOLVENT EXTRACTION ZONE WITH A SELECTIVE SOLVENT COMPRISING A SOLUTION OF PRIMARY AND SECONDARY SOLVENT CONSTITUENTS TO FORM A FAT SOLVENT STREAM AND A RAFFINATE STREAM, SAID PRIMARY SOLVENT BEING SOLUBLE WITH AND LESS VOLATILE THAN SAID AROMATIC HYDROCARBON AND SAID SECONDARY SOLVENT BOILING AT A TEMPERATURE BELOW SAID PRIMARY SOLVENT, THE IMPROVEMENT IN SAID PROCESS WHICH COMPRISES VAPORIZING DISSOLVED AROMATIC HYDROCARBON AND SECONDARY SOLVENT FROM SAID FAT SOLVENT STREAM IN A SOLVENT STRIPPING ZONE, THEREBY FORMING A LEAN SOLVENT STREAM, RECOVERING SECONDARY SOLVENT FROM THE RESULTING VAPORS, PASSING AT LEAST A PORTION OF THE RECOVERED SECONDARY SOLVENT IN INDIRECT HEAT EXCHARGE RELATIONSHIP WITH AT LEAST ONE OF SAID AFOREMENTIONED FAT SOLVENT AND LEAN SOLVENT STREAMS TO FORM THEREBY SECONDARY SOLVENT VAPORS OF GREATER HEAT CONTENT, PASSING SAID SECONDARY SOLVENT VAPORS INTO THE LOWER PORTION OF SAID SOLVENT STRIPPING ZONE AS A STRIPPING MEDIUM FOR THE REMOVAL OF RESIDUAL DISSOLVED AROMATIC HYDROCARBON FROM THE LEAN PRIMARY SOLVENT IN THE STRIPPING ZONE, RECOVERING FROM THE STRIPPING STEP A PREDOMINANTLY AROMATIC FRACTION AND A FRACTION CONTAINING AROMATIC AND NON-AROMATIC HYDROCARBONS, AND INTRODUCING THE LAST-MENTIONED FRACTION INTO THE LOWER PORTION OF SAID EXTRACTION ZONE.