Experimental Study of Operational Parameters on Product Size Distribution of Tumbling Mill

Abstract

To assess the effects of the mill operating parameters such as mill speed, ball filling, slurry concentration and slurry filling on grinding process and size distribution of mill product, it was endeavored to build a pilot model with smaller size than the mill. For this aim, a pilot mill with 1 m × 0.5 m was implemented. There are 15 lifters with 50 mm height and face angle of 30˚. In the present work, the combination of the balls (40% of the balls with 60 mm diameter, 40% of the balls with 40 mm diameter and 20% of the balls with 25 mm diameter) was used as grinding media with 10%, 15%, 20% and 25% of the total volume of the mill. The experiments were carried out at 60%, 70%, 80% and 90% of the critical speed. The feed of the mill is copper ore with the size smaller than 25.4 mm, which d80 and d50 of them are 12.7 and 8 mm, respectively and slurries with 40%, 50%, 60%, 70% and 80% of solid and the slurry filling between 0.5 and 2.5. The results showed that the best grinding and grading occurs at 70–80% of the critical speed and ball filling of 20–25%. Optimized grinding was observed when the slurry volume is 1–1.5 times of the ball bed voidage volume and the slurry concentration is between 60% and 70%. The mill grinding mechanism in this work is a combination of both impact and abrasion mechanisms.