Process for fluid bed operation

Claim 1

IN THE METHOD OF EFFECTING CONTACT BETWEEN A SOLID AND A GAS WHEREIN A MASS OF DISCRETE PARTICLES OF THE SOLID IS EXPANDED TO FLUID BED CONDITION BY THE PASSAGE OF THE GAS UPWARDLY THERETHROUGH, THE IMPROVEMENT WHICH COMPRISES MAINTAINING THE MASS OF PARTICLES IN THE FORM OF A FLUID COLUMN COMPRISING AT LEAST TWO CONTIGUOUS FLUID BEDS OF SUFFICIENTLY DIFFERENT DEGREES OF EXPANDED FLUID AGITATION TO SUBSTANTIALLY PREVENT SHORT-CIRCUITING OF THE PARTICLES FROM ONE BED TO ANOTHER WHILE PERMITTING FLUID FLOW OF THE PARTICLES BY GRAVITY PROGRESSIVELY DOWNWARDLY THROUGH SAID BEDS BY (1) INTRODUCING INTO THE LOWER PORTION OF THE MASS ONLY A PORTION OF THE TOTAL AMOUNT OF GAS INTRODUCED INTO THE FLUID COLUMN BUT IN AMOUNT SUFFICIENT TO SUPPORT THE MASS OF PARTICLES IN SAID LOWER PORTION IN AN EXPANDED FLUID CONDITION HAVING AN APPARENT DENSITY OF ABOUT 75-90% OF THE UNEXPANDED BULK DENSITY OF THE MASS OF PARTICLES PRIOR TO CHARGING, AND (2) INTRODUCING INTO AN INTERMEDIATE PORTION OF THE MASS ANOTHER SUBSTANTIAL PORTION OF THE TOTAL AMOUNT OF THE GAS INTRODUCED INTO THE FLUID COLUMN SO AS TO SUPPORT THE MASS OF PARTICLES ABOVE THE AFOREMENTIONED MASS IN A MORE HIGHLY EXPANDED AND ACTIVELY AGITATED FLUID CONDITION HAVING AN APPARENT DENSITY OF ABOUT 55-75% OF THE UNEXPANDED BULK DENSITY OF THE MASS OF PARTICLES PRIOR TO CHARGING, THE UPPER BOUNDARY OF THE FLUIDIZED COLUMN RESEMBLING THAT OF A BOILING LIQUID AND BEING ESTABLISHED EXCLUSIVELY BY THE RATE OF INTRODUCTION OF GAS INTO SAID COLUMN WITH RESPECT TO THE RATE OF CHARGE OF SOLID PARTICLES TO THE COLUMN.