IMPROVED PROCESS FOR PREPARING ANHYDROUS ALUM EARTH

This invention relates to a method for the production of anhydrous alumina having a desired alpha -conversion from alumina trihydrate. This method is directed to production of anhydrous alumina having a desired alpha -conversion from alumina trihydrate in which water is removed in a precalcining zone wherein the alumina trihydrate is heated to a temperature below 450 DEG C. Then, the precalcined dehydrated alumina is recrystallized to alpha -alumina in a reaction chamber by directing an oxygen containing gas to the reaction chamber, mixing and suspending the precalcined alumina and fuel in the oxygen containing gas and feeding the mixture to a combustion zone, followed by exothermal recrystallization of the alumina which is initiated by rapidly heating the precalcined alumina by burning the fuel in the oxygen containing gas in the hot combustion zone and withdrawing the recrystallized alumina from the top of the reaction chamber suspended in a combustion gas stream. The recrystallized alumina is then separated from the gas stream and cooled to produce anhydrous alumina having the desired content of alpha -conversion.