Multistage xylene separation process

Claim 1

A PROCESS FOR RECOVERING HIGH YIELDS OF PARAXYLENE HAVING A PURITY IN EXCESS OF 95% FROM A HYDROCARBON FRACTION COMPRISING PARAXYLENE AND AT LEAST ONE OTHER XYLENE ISOMER WHICH COMPRISES COOLING SAID FRACTION TO A TEMPERATURE IN THE RANGE OF FROM ABOUT -75*F. TO -120*F. FOR A TIME SUFFICIENT TO CAUSE THE FORMATION OF A FIRST SLURRY COMPRISING A FIRST SOLID CRYSTAL PHASE AND A FIRST LIQUID PHASE, SEPARATING SAID PHASES IN A PRIMARY SEPARATION ZONE, RECOVERING SAID FIRST LIQUID PHASE, PASSING SAID FIRST SOLID CRYSTAL PHASE AND A FIRST RECYCLE STREAM IN CONCURRENT CONTACT AS A SECOND SLURRY TO AN INTERMEDIATE SEPARATION ZONE, ADJUSTING THE TEMPERATURE OF SAID SECOND SLURRY TO A TEMPERATURE IN THE RANGE OF FROM ABOUT 0*F. TO -30*F. TO THEREBY WARM THE OUTER LAYERS OF PARAXYLENE CRYSTALS IN SAID SECOND SLURRY AND FACILITATE ENRICHMENT OF THE ADHERING LIQUID LAYERS IN PARAXYLENE, SEPARATING SAID SECOND SLURRY IN SAID INTERMEDIATE SEPARATION ZONE TO RECOVER A SECOND SOLID CRYSTAL PHASE AND A SECOND LIQUID PHASE AS SAID FIRST RECYCLE STREAM TO CONTACT SECOND LIQUID PHASE AS SAID FIRST RECYCLE STREAM TO CONTACT SAID FIRST SOLID CRYSTAL PHASE RECOVERED FROM SAID PRIMARY SEPARATION ZONE, PASSING SAID SECOND CRYSTAL PHASE AND A SECOND RECYCLE STREAM IN CONCURRENT CONTACT AS A FINAL SLURRY TO A TERMINAL SEPARATION ZONE, ADJUSTING THE TEMPERATURE OF SAID FINAL SLURRY TO A TEMPERATURE IN THE RANGE OF FROM ABOUT 10*F. TO 4*F. TO THEREBY WARM THE OUTER LAYERS OF PARAXYLENE CRYSTALS IN SAID FINAL SLURRY AND FACILITATE ENRICHMENT OF THE ADHERING LIQUID LAYERS IN PARAXYLENE, SEPARATING SAID FINAL SLURRY IN SAID TERMINAL SEPARATION ZONE TO RECOVER A FINAL SOLID CRYSTAL PHASE PRODUCT HAVING A PARAXYLENE PURITY IN EXCESS OF 95% AND A FINAL LIQUID PHASE, AND PASSING AT LEAST A PORTION OF SAID FINAL LIQUID PHASE AS SAID SECOND RECYCLE STREAM TO CONTACT SAID SECOND SOLID CRYSTAL PHASE RECOVERED FROM SAID INTERMEDIATE SEPARATION ZONE.