Fine dry grinding of zeolite in a laboratory ball mill

Abstract

This paper presents the importance and usage of natural zeolites, which was recently recognized in the industry. Therefore, the grinding properties of natural zeolite were studied with the emphasis on a kinetic study in a ball mill. The experimental mill employed was laboratory sized, 200 mm diameter, 191 mm length, providing a total mill volume of 6000 cm(3), with a total mass of 5.62 kg of steel balls of 25 mm diameter with a charge of 20% of the mill volume and with a rotation speed of 76 rpm. The breakage parameters were determined by using single sized feed fractions of -850 + 600 mum, -600 + 425 mum, and -425 + 300 mum for the zeolite samples. The S-i (specific rate of breakage) and B-i,B-j (primary breakage distribution) values were obtained for those feed size fractions in order to predict the product size distributions by simulation for comparison to the experimental data. From the experimental results, S-i values increased as the feed sizes became coarser, i.e., the highest S-i value was 0.85 min(-1) for -850 + 600 mum, while the lowest S-i value was 0.65 min(-1) for -425 + 300 mum feed ground in the mill. The B-i,B-j values obtained for the zeolite sample were gamma = 0.84, phi = 0.61, and beta = 4.25. The breakage parameters obtained showed that the zeolite is broken faster than quartz and slower than calcite and barite in terms of the a(T) values reported previously at the same experimental conditions. The simulations of the product size distributions of zeolite were in good agreement with the experimental data using a standard ball mill simulation program. The slowing-down effect was also seen in the mill after 4 min. of grinding.