Dusting and fluidity of alumina with different physicochemical properties

The objects of investigation were metallurgical aluminas from different manufacturers and with different physicochemical properties varying in wide limits: the content of the fraction −45 μ m was 4–60%, the losses during calcination were 0.5–1.2%, the content of the α phase was 2.5–23.0%, and the specific surface was 55–120 m 2 /g. The outflow time t out of the aluminas was measured using funnels with standard (2.4 mm) and increased (4 and 5 mm) orifices; the outflow time was 2–20 min. The correlations for the values of t out for the funnels with mentioned orifices were obtained. The outflow time decreased as the content of the fraction −45 μ m decreased and the water content in alumina increased. The dusting factors (DF) of aluminas were measured with the help of the developed dust counter, and the variation range was 0.5–8.0 mg/g. The dusting factor increased as the content of the fraction −45 μm and water content in aluminum increased. The main factor determining t out and DF is the granulometric composition of alumina. The effect of the form of alumina particles and moisture content in alumina on the t out and DF is established. The mechanism explaining the interrelation between the moisture and these values is suggested.