process for the production of industrial ceramics raw materials from alkalihaltiger alumina

摘要

Preparation of ceramic raw material on the basis of purified aluminum oxide from alumina comprises preparing an alumina raw material by Bayer process; calcinating the material to obtain a crystalline, alkali containing alumina consisting of gamma -alumina with an alpha -alumina (maximum 30%); subsequently thermally treating the alumina and processing in an intensive agitator to obtain an aqueous, alkaline suspension of alumina; contacting a bubble-forming carbon dioxide; separating dealklylated alumina from the liquid phase; and drying the dealkylated alumina to obtain purified alpha -aluminum oxide. Preparation of ceramic raw material on the basis of purified aluminum oxide from alumina comprises: (a) preparing an alumina raw material by Bayer process; (b) calcinating the material to obtain a crystalline, alkali containing alumina consisting of gamma -alumina with an alpha -alumina (maximum 30%), at 800-1200[deg]C for 0.5-3 hours; (c) subsequently thermally treating the obtained alumina; (d) processing the alumina exhibiting a Brunauer, Emmett and Teller surface of at least 30 m 2/g, and a specific particle size distribution with fine particles (less than 45 mu m) and coarse particles (less than 150 mu m) of less than 10%, in an intensive agitator with number of revolutions of 50-250 rpm to obtain an aqueous, alkaline suspension of alumina with a solid content of 60-1000 g/l; (e) contacting a bubble-forming carbon dioxide (4-10 g/kg of alumina) with a bubble diameter of 8 mu m with the aqueous, alkaline suspension of alumina at 2-10 bar; (f) continuously adjusting the retention time (10-100 seconds) of the suspension with a pressure difference of at least 2 bar; (g) separating the dealklylated alumina from the liquid phase; and (h) drying the dealkylated alumina at greater than 1200[deg]C for 4 hours to obtain purified alpha -aluminum oxide with at least 80% of alpha -aluminum oxide. Independent claims are included for: (1) a device for executing the preparation of ceramic raw material comprising an assembly for purifying and calcinating the alumina raw materials, a first assembly unit (1) for preparing the suspension, a second assembly unit (2) for carbon dioxide treatment of the suspension in the gas-tube, a third assembly unit (3) for separating dealkylated alumina and a fourth assembly unit (4) for drying the dealkylated alumina; and (2) the dealkylated aluminum oxide comprising at least 80% of alpha -oxide, remaining of transition alumina, sodium oxide (0.1 wt.%), silica (0.02 wt.%), boron oxide (0.001 wt.%), fluorine (0.01 wt.%) and chlorine (0.002 wt.%), where the Brunauer, Emmett and Teller surface of the dealkylated aluminum oxide is 0.5-10 m 2/g.