Solvent extraction process

Claim 1

A PROCESS FOR SEPARATING A MIXTURE OF LIQUEFIED BUTANES, BUTENES AND BUTADIENE ACCORDING TO THEIR DEGREE OF UNSATURATION COMPRISING INTRODUCING SAID MIXTURE INTO A FIRST EXTRACTION ZONE AT AN INTERMEDIATE POINT, INTRODUCING A QUANTITY OF A FIRST SOLVENT HAVING A PREFERENTIAL SELECTIVITY FOR UNSATURATED HYDROCARBONS INTO SAID ZONE AT A POINT NEAR ONE END, COUNTERCURRENTLY CONTACTING SAID MIXTURE OF HYDROCARBONS AND SAID FIRST SOLVENT UNDER CONDITIONS TO FORM A FIRST RAFFINATE PHASE AND A FIRST EXTRACT PHASE, REMOVING THE FIRST RAFFINATE PHASE FROM SAID ONE END OF SAID FIRST ZONE, RECOVERING BUTANES FROM SAID FIRST RAFFINATE PHASE AS A FIRST PRODUCT OF THE PROCESS AND REMOVING SAID FIRST EXTRACT PHASE FROM THE OPPOSITE END OF SAID FIRST ZONE; INTRODUCING THIS EXTRACT PHASE INTO ONE END OF A FIRST INTERMEDIATE ZONE, INTRODUCING AN INTERMEDIATE PRODUCT RICH IN BUTENES AND AS SUBSEQUENTLY PRODUCED INTO SAID ONE END OF SAID FIRST INTERMEDIATE ZONE, INTRODUCING A SECOND QUANTITY OF SAID FIRST SOLVENT INTO SAID FIRST INTERMEDIATE ZONE AT THE OTHER END AND COUNTERCURRENTLY CONTACTING SAID EXTRACT PHASE AND SAID INTERMEDIATE PRODUCT RICH IN BUTENES WITH SAID SECOND QUANTITY OF SAID FIRST SOLVENT, REMOVING A BUTENE CONTAINING INTERMEDIATE RAFFINATE FREE FROM BUTADIENE FROM SAID OTHER END OF SAID FIRST INTERMEDIATE ZONE AND RECOVERING THE BUTENES THEREFROM AS A SECOND PRODUCT OF THE PROCESS AND REMOVING AN INTERMEDIATE EXTRACT PHASE FROM SAID ONE END OF SAID FIRST INTERMEDIATE ZONE; INTRODUCING THIS INTERMEDIATE EXTRACT PHASE INTO ONE END OF A SECOND INTERMEDIATE ZONE, REMOVING SOME INTERMEDIATE PRODUCT RICH IN BUTENES FROM SAID ONE END OF SAID SECOND INTERMEDIATE ZONE AND INTRODUCING SAME INTO SAID OPPOSITE END OF SAID FIRST EXTRACTION ZONE AS REFLUX AND REMOVING THE REMAINDER OF SAID INTERMEDIATE PRODUCT RICH IN BUTENES FROM SAID ONE END OF SAID SECOND INTERMEDIATE ZONE AND INTRODUCING SAME INTO SAID ONE END OF SAID FIRST INTERMEDIATE ZONE AS SAID INTERMEDIATE PRODUCT RICH IN BUTENES AND AS SUBSEQUENTLY PRODUCED, INTRODUCING A PORTION OF A BUTADIENE PRODUCT AS SUBSEQUENTLY PRODUCED INTO THE OTHER END OF SAID SECOND INTERMEDIATE ZONE AND CONTERCURRENTLY CONTACTING THIS BUTADIENE PRODUCT WITH SAID INTERMEDIATE EXTRACT PHASE IN SAID SECOND INTERMEDIATE ZONE AND REMOVING THEREFROM AN EXTRACT PHASE RICH IN BUTADIENE; INTRODUCING THIS LATTER EXTRACT PHASE RICH IN BUTADIENE INTO ONE END OF A SECONDARY EXTRACTION ZONE, INTRODUCING A SECONDARY SOLVENT IN WHICH BUTADIENE IS SOLUBLE INTO THE OTHER END OF SAID SECOND EXTRACTION ZONE AND COUNTERCURRENTLY CONTACTING SAID EXTRACT PHASE RICH IN BUTADIENE AND SAID SECONDARY SOLVENT, REMOVING A RAFFINATE PHASE FROM SAID OTHER END OF SAID SECOND EXTRACTION ZONE COMPRISING FIRST SOLVENT AND RECYCLING THIS RAFFINATE AS PRIMARY SOLVENT TO THE FIRST EXTRACTION ZONE AND TO THE FIRST INTERMEDIATE ZONE, REMOVING AN EXTRACT PHASE RICH IN BUTADIENE FROM SAID ONE END OF SAID SECOND EXTRACTION ZONE, RECOVERING SAID BUTADIENE FROM SECONDARY SOLVENT OF LAST SAID EXTRACT PHASE, RECYCLING SAID SECONDARY SOLVENT TO SAID SECONDARY EXTRACTION ZONE, INTRODUCING A PORTION OF SAID RECOVERED BUTADIENE INTO SAID OTHER END OF SAID SECOND INTERMEDIATE ZONE AS SAID BUTADIENE PRODUCT SUBSEQUENTLY PRODUCED AND REMOVING THE REMAINING PORTION OF SAID RECOVERED BUTADIENE AS A THIRD PRODUCT OF THE PROCESS.