Catalytic treatment of alumina in fluidized beds

Claim 1

THE PROCESS FOR CALCINING FINELY DIVIDED ALUMINA SOLIDS TO YIELD THE ALPHA FORM OF ALUMINA, COMPRISING ESTABLISING AND MAINTAINING A PLURALITY OF SUCCESSIVE FLUIDIZED BEDS INCLUDING A FIRST BED MAINTAINED AT A SOLIDS CALCINING TEMPERATURE SUFFICIENT TO FORM GAMMA ALUMINA, A SECOND BED MAINTAINED AS A CATALYTIC CONVERSION BED, AND A THIRD BED MAINTAINED AS A SOLIDS COOLING BED; INTRODUCING ALUMINA INTO THE FIRST BED AND THERE CALCINING IT TO YIELD GAMMA ALUMINA; INTRODUCING SUCH GAMMA ALUMINA AND FINELY DIVIDED ALUMINUM FLUORIDE INTO THE SECOND BED AND THERE CONVERTING GAMMA ALUMINA TO ALPHA ALUMINA; TRANSFERRING SUCH ALPHA ALUMINA INTO THE THIRD BED; FLUIDIZING SOLIDS IN THE FIRST AND THIRD BEDS BY PASSING A STREAM OF GAS UPWARDLY FIRST THROUGH THE THIRD BED THENCE THROUGH THE FIRST BED THEREBY COOLING SOLIDS IN THE THIRD BED AND PREHEATING GAS PRIOR TO ITS ENTRY INTO THE FIRST DISCHARGING GASES EXITING FROM SAID FIRST BED AND SAID SECDISCHARGING GASES EXITING FROM SAID FIRST BED AND SAID SECOND BED AS SEPARATE STREAMS.