PROCESS FOR PRODUCING ALUMINIUM OXIDE FROM ALUMINIUM HYDROXIDE

摘要

1. A process for producing water-free aluminium oxide from aluminium hydroxide in a circulating fluidised bed comprising a fluidised bed reactor (8), separator (6) and return flow line involves the following steps: the aluminium hydroxide is fed into the gas-side second stage of a two-stage suspension pre-heater (2) operated by the waste gases from the fluidised bed reactor (8) of the circulating fluidised bed and at least partially dewatered; dewatered aluminium hydroxide from the second stage of the suspension pre-heater (2) is fed into the gas-side first stage of a suspension pre-heater (5) operated by the waste gases from the fluidised bed reactor (8) of the circulating fluidised bed, further dewatered and then fed into the circulating fluidised bed which is operated by oxygen-containing fluidisation gas (10) indirectly heated in a subsequent cooling stage by the aluminium oxide produced and by oxygen-containing directly heated secondary gas (11) fed in at a higher level, wherein indirect heat of fluidisation gas is performed in the fluidised bed cooler (23), characterized in that the temperature in the circulating fluidised bed is set at between 850 and 1000 degree C., the aluminium oxide removed from the circulating fluidised bed is mixed for at least two minutes with 10 to 25 wt.% of the partially dewatered aluminium hydroxide yielded by the solid-side first stage of the suspension pre-heater (2), partially dewatered for at least 2 min., the mixed material is then cooled in a multistage suspension cooler (15, 16, 17, 18, 19, 20), heating secondary gas (11), and then in the fluidised bed cooler (23), indirectly heating fluidisation gas (10). 2. A process according to Claim 1, characterized in that the pressure loss in the reactor with fluidised bed is set to be ( 100 mbar. 3. A process according to Claim 1 or 2, characterized in that at least partially dewatered aluminium hydroxide from the second stage of the suspension pre-heater (2) is separated in a separator (3), arranged before an electric filter. 4. A process according to Claims 1, 2 or 3, characterized in that the final cooling of the obtained aluminium oxide is performed after the multistage cooling in a fluidised bed due to indirect heat exchange at the first stage of the fluidisation gas (10) for reactor (8) with a circulating fluidised and at further stages a fluid heat carrier medium is heated.