Crystallization method and apparatus

Claim 1

A PROCESS FOR THE RECOVERY OF A CRYSTALLIZABLE MATERIAL FROM A LIQUID MULTICOMPONENT MIXTURE CONTAINING SAID MATERIAL, WHICH PROCESS COMPRISES: PASSING SUCH A MIXTURE THROUGH A SERIES OF SEPARATION STAGES ALTERNATED WITH SURGE ZONES, EACH STAGE COMPRISING A CRYSTALLIZATION AND CRYSTAL PURIFICATION ZONE WHEREIN SAID MIXTURE IS COOLED TO PRODUCE CRYSTALS OF SAID MATERIAL, SAID CRYSTALS ARE MOVED IN A COMPACT, CONTINUOUS MASS TOWARD A MELTING SECTION IN SAID ZONE WHERE THE CRYSTALS ARE MELTED, A PORTION OF SAID MATERIAL IS WITHDRAWN IN MOLTEN PURIFIED FORM AND A PORTION OF MOLTEN CRYSTALLIZABLE MATERIAL IS FORCED COUNTERCURRENTLY TO THE MOVEMENT OF SAID CRYSTALS AND IN INTIMATE CONTACT THEREWITH, AND MOTHER LIQUOR IS WITHDRAWN FROM SAID ZONE; PASSING SAID MOTHER LIQUOR TO ONE OF SAID SURGE ZONES IMMEDIATELY DOWNSTREAM FROM SAID CRYSTALLIZATION AND PURIFICATION ZONE, FROM SAID SURGE ZONE, TO A SUBSEQUENT CRYSTALLIZATION AND CRYSTAL PURIFICATION ZONE; MEASURING THE LIQUID LEVEL IN EACH OF SAID SURGE ZONES; AND TOTALLY RECYCLING, TO THE CRYSTALLIZATION AND CRYSTAL PURIFICATION ZONE FROM WHICH IT WAS WITHDRAWN, THE PURIFIED MOLTEN CRYSTALLIZABLE MATERIAL AND MOTHER LIQUOR WHEN THE LIQUID LEVEL IN SAID SURGE ZONE IMMEDIATELY DOWNSTREAM EXCEEDS A PREDETERMINED MAXIMUM AND WHEN THE LEVEL IN THE SURGE ZONE IMMEDIATELY UPSTREAM FROM SAID LAST-MENTIONED CRYSTALLIZATION AND CRYSTAL PURIFICATION ZONE DROPS BELOW A PREDETERMINED MINIMUM; AND DISCONTINUING SAID RECYCLING WHEN PREDETERMINED DESIRED LIQUID LEVELS ARE PRESENT IN SAID SURGE ZONES.