Process and apparatus for fluidized bed drying

Claim 1

A PROCESS FOR DRYING PARTICULATE THEMOPLASTIC MATERIAL CONTAINING LIQUID DILUENT COMPRISING THE STEPS OF: (1) MAINTAINING A FLUIDIZED BED OF SAID MATERIAL IN A DRYING ZONE PROVIDED WITH A PERFORATE ONE-PIECE METAL PLATE IMMEDIATELY BELOW SAID BED; (2) PASSING HOT FLUIDIZING AND DRYING GAS UPWARDLY INTO SAID BED THRU SAID PLATE TO EFFECT FLUIDIZING AND DRYING OF SAID MATERIAL; (3) INTRODUCING FRESH SAID MATERIAL TO AND WITHDRAWING DRIED MATERIAL FROM SAID BED; (4) PROVIDING THE WALLS OF THE HOLES IN SAID PLATE AND THE BOTTOM SURFACE OF SAID PLATE WITH CERAMIC MATERIAL TO LOWER HEAT CONDUCTION THERETO FROM SAID GAS; (5) CIRCULATING A FLUID COOLANT LATERALLY THRU CONDUITS WITHIN SAID PLATE TO EXTRACT HEAT THEREFROM SO AS TO PERMIT HIGHER DRYING GAS TEMPERATURE THAN PERMISSIBLE WITHOUT STEPS (4) AND (5) AND AVOID INCIPIENT FUSION OF SAID MATERIAL AND STICKING THEREOF TO THE UPPER SURFACE OF SAID PLATE WHICH WOULD NORMALLY OCCUR; (6) WITHDRAWING DRYING GAS FROM AN UPPER SECTION OF THE DRYING ZONE OF STEP (1) ABOVE SAID BED; AND (7) USING HIGHER DRYING GAS TEMPERATURE THAN COULD BE USED WITHOUT STEPS (4) AND (5).