Crystal purification process and apparatus

Claim 1

A PROCESS FOR THE PURIFICATION OF DISCRETE CRYSTALS OF AN ORGANIC COMPOUND CONTAINING OCCLUDED IMPURITIES, WHICH COMPRISES THE STEPS OF PASSING A FEED COMPRISING A THICK SLURRY OF SAID CRYSTALS INCLUDING A LIQUID, READILY-VAPORIZED REFRIGERANT INTO AN ELONGATED ENCLOSED PURIFICATION ZONE AT A POINT SPACED FROM THE LOWER END OF SAID ZONE UNDER CONDITIONS OF TEMPERATURE AND PRESSURE WHICH MAINTAIN SAID REFRIGERANT IN LIQUID PHASE; COMPRESSING SAID CATALYSTS INTO A COMPACT MASS IN THE LOWER END OF SAID ZONE WHILE MOVING THE LIQUID IN SAID SLURRY TO THE UPPER END; MELTING THE CATALYSTS IN SAID LOWER END AND MAINTAINING A MELT THERE; WITHDRAWING ONLY A PORTION OF SAID MELT FROM SAID LOWER END AS A PRODUCT; FORCING A PORTION OF SAID MELT THROUGH SAID CRYSTALS TO THE UPPER END OF SAID ZONE AS A REFLUX THEREBY WASHING OCCLUDED IMPURITIES FROM SAID CRYSTALS; MAINTAINING A PREDETERMINED LIQUID LEVEL IN SAID PURIFICATION ZONE; DISCONTINUING THE COMPRESSION STEP AND REDUCING THE PRESSURE IN SAID ZONE SO AS TO VAPORIZE A PORTION OF SAID REFRIGERANT AND FREEZE CRYSTALS OF SAID REFLUX MELT; WITHDRAWING VAPORIZED REFRIGERANT FROM THE UPPER PORTION OF SAID ZONE; WITHDRAWING A LIQUID LOWERMELTING STREAM FROM THE UPPER END OF SAID ZONE; AND PASSING ADDITIONAL FEED INTO SAID ZONE DURING THE PRESSURE REDUCING STEP.