Fractional crystallization control system

Claim 1

IN A PROCESS IN WHICH CRYSTALS AND ADHERING MOTHER LIQUOR ARE CONTINUOUSLY PASSES AS A SLURRY FROM A CHILLING ZONE THROUGH A FILTERING ZONE FROM WHICH A STREAM OF MOTHER LIQUOR IS WITHDRAWN, THE CRYSTALS AND REMAINING MOTHER LIQUOR ARE PASSED FROM SAID FILTERING ZONE INTO A REFLUX ZONE, THE CRYSTALS ARE PASSED FROM SAID REFLUX ZONE INTO A MELTING ZONE, HEAT IS INTRODUCED INTO SAID MELTING ZONE TO MELT THE CRYSTALS TO OBTAIN A MELT BY PASSING A HEAT EXCHANGE FLUID IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH THE CRYSTALS, A PORTION OF THE MELT IS WITHDRAWN FROM THE MELTING ZONE AS A PRODUCT STREAM, AND THE REMAINDER OF THE MELT IS PASSED COUNTERCURRENTLY TO THE MOVEMENT OF CRYSTALS AS REFLUX THEREFROM; THE IMPROVEMENT COMPRISING PASSING SAID HEAT EXCHANGE FLUID IN A VAPOROS STATE SUBSTANTIALLY AT THE CONDENSATION TEMPERATURE THEREOF IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH THE CRYSTALS AT SUCH A RATE OF FLOW THAT ONLY A PORTION OF SAID HEAT EXCHANGE FLUID IS CONDENSED, THE UNCONDENSED PORTION BEING SUFFICIENTLY GREAT TO SWEEP THE CONDENSED PORTION THROUGH THE INDIRECT HEAT EXCHANGE WITH THE CRYSTALS AND ELIMINATE THE FORMATION OF POCKETS OF SAID CONDENSED PORTION, PROVIDING A UNIFORM TEMPERATURE OF SAID HEAT EXCHANGE FLUID THROUGHOUT SAID INDIRECT HEAT EXCHANGE WITH THE CRYSTALS.