HOCHTONERDEHALTIGER ROHSTOFF UND VERFAHREN ZUR HERSTELLUNG

High alumina compositions contain (wt%): alumina 50 -90; magnesium oxide 1 - 20; silica 0.5 - 15; aluminum nitride 0.1 - 15; ferric oxide 0.1 - 5; calcium oxide 0.1 - 7; fluorine 0.1 - 10; sodium oxide 0.1 - 6; potassium oxide 0.1 -2; aluminum 0.1 -10; silicon 0.1 - 3; iron 0.1 - 3; loss on ignition 0.1 - 15 and remaining materials 5 max. The main mineral components are bayerite, boehmite, corundum and spinel. Moisture content is 10 wt% max and 90% of the particles are below 500mu m. The specific surface is more than 50 m 2>/g and the average pore diameter less than 100 angstroms. An independent claim is included for a method for producing the raw material comprising: (A) dry milling an aluminum salt slag containing 20 - 60 wt% of NaCl, KCl, CaF 2, 35 - 75 Wt% of Al 2O 3, MgO or SiO 2and up to 15% of both metallic aluminum and aluminum nitride and, after adding water, mill dot produce a suspension containing 25 - 55 wt% solids, at least 90wt% of which has particle size below 500 mu m, the average particle being below 50 mu m; (B) the suspension is treated in a reactor fitted with a stirrer at a pH of 9 - 12 and 30 - 90[deg] C for 10 -60 minutes, producing aluminum hydroxide by reaction of metallic aluminum and aluminum nitride with water, liberating hydrogen and ammonia and forming a salt sol which is made alkaline by the ammonia; (C) filtering the product, washing the filter cake and spraying it with water to remove salts and sucking air through it to adjust its moisture content to 30 - 50 wt%; and (D) drying the product at 70 - 110[deg] C to a residual moisture content of less than 10 wt%.