OPTIMIZATION OF THE PROCESS OF PRODUCING REACTIVE ALUMINA USING A BALL MILL

The article presents the results of a study on the optimization of process parameters for producing finely dispersed alpha-aluminum oxide (reactive alumina) by dry grinding in a ball mill using the method of mathematical modeling of the process. The feedstock was commercially available calcined alumina characterized by an Al2O3 content >99 wt.%, D₅₀ = 80 μm and the absence of a submicron particle fraction. The varied process parameters were: the volumetric loading of the drum with grinding media (φ = 20, 30, 40%), the drum rotation speed (v = 60, 80, 100 rpm) and the concentration of grinding intensifier (ω = 0; 0.05; 0.1 wt.%). Using three-factor regression analysis, we obtained adequate mathematical models describing the influence of the specified parameters on the key characteristics of reactive alumina: median particle size (D₅₀), submicron fraction content (Q <1 μm), and specific surface area (Ssp). It was found that the dominant factor is the volumetric loading of the drum: an increase in φ from 20 to 40% reduces D₅₀ from 5.5 to 3.5 μm, increases Q to 12–14%, and Ssp to 5500–6000 cm²/g. The introduction of an intensifier in an amount of 0.05 wt.% additionally reduces the median particle size by 8–10%, and also increases the proportion of submicron particle fraction and the specific surface area of the resulting powder. It was revealed that at a drum rotation speed of 60 rpm, the grinding of alumina raw materials occurs predominantly by the attrition mechanism and is ineffective. Increasing the drum speed to 80 rpm is optimal for minimizing D₅₀ due to the balanced combination of impact and abrasive action of the grinding media.