PROCEDURE FOR THE MANUFACTURE OF RAW MATERIALS FOR THE ALUMINUM BASED CERAMIC INDUSTRY WITH ALKALINE CONTENT.

摘要

Process for the manufacture of raw materials for the ceramic industry starting from purified aluminum oxide from alumina, which comprises a) preparing an alumina raw material by a Bayer process; b) calcining the material at 800 = T = 1200 ° C to obtain a crystalline alumina with an alkaline content; c) purify the crystalline alumina in aqueous suspension with the addition of CO2, separating the alumina; and d) subsequently heat the alumina; characterized in that e) an crystalline alumina, with an alkaline content, consisting mainly of gamma-Al2O3 with an α-Al2O3 content of a maximum of 30% is obtained by calcination for a time t = 0.5-3 hours; f) alumina shows a BET surface area of at least 30 m 2 / g and a specific particle distribution with a fine particle fraction (45 μm) of less than 10% and a selection of coarse particles ( 150 μm ) of less than 10% which is emulsified in an intensive stirrer with a speed of 50-250 rpm until an aqueous alkaline suspension with a solids content of 60-1000 g / l is obtained; g) CO2 is introduced by bubbling with a maximum bubble diameter of 8 mm in an amount of 4-10 g of CO2 per kg of alumina in the aqueous alkaline alumina suspension with a total pressure of P = 2-10 bar; h) during a residence time of 10-100 seconds, a continuously decreasing total pressure with a minimum pressure difference of 2 bar is adjusted in the suspension; i) the desalkalized alumina is separated from the liquid phase; and j) the desalkalized alumina is dried and subjected to thermal post-treatment at T 1200 ° C for a time t = max 4 hours to obtain the purified raw material for the ceramic industry containing a minimum of 80% of α-Al2O3, the rest being transition alumina and with a BET surface area of 0.5 to 10 m 2 / g.