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Abstract
The Sarcheshmeh mine processes 40,000 t/d of ore grading 0.9% Cu and 0.035% Mo. Grinding is affected in single-stage ball mills using 80 mm forged steel balls, with an average consumption of 850 g/t. One of its 5 m diameter, 8 m length ball mills was emptied to measure the ball size distribution. The broken balls were first separated from the total charge, and the remaining balls classified into five size intervals of +70 mm, -70 +60 mm, -60+50 mm, -50+40 mm, -40 mm. The charge was composed of 280,534 balls (excluding broken balls) with a total mass of 305,180 kg. It was found that 4.0% of the balls were broken; the size distribution of the charge was also markedly different from the desired one, particularly for the small-sized balls. For instance, 9% of the balls were expected to measure 2.54 to 3.18 cm in diameter, but none was found. On the other hand, the amount of top-size balls was 30% higher than expected. The radial hardness of balls, which was determined by cutting the balls in halves, showed that the hardness sharply drops when the balls become smaller than 65 mm. The unexpected ball size distribution was attributed to the rapid change in the ball's radial hardness. Based on the measured ball size distribution, a new ball makeup charge which uses 80% of 80 mm and 20% of 60 mm balls instead of 100% of 80 mm was proposed and implemented. The effect of the new ball makeup procedure in terms of ball consumption and grinding efficiency is being investigated.

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		KMPC Hemmat A Mineral Processing Digital Library
	All Years to Access Full-Text Export citations Measurement of ball size distribution in a 8 m x 5 m primary mill of Sacheshmeh Copper Mine By S. Banisi, M. Pourkani, M. Kargar and A.R. Laplante Published in Canadian Mineral Processors Conference (CMP) at 1999 Direct link: http://kmpchemmat.ir/pii/30973 Abstract The Sarcheshmeh mine processes 40,000 t/d of ore grading 0.9% Cu and 0.035% Mo. Grinding is affected in single-stage ball mills using 80 mm forged steel balls, with an average consumption of 850 g/t. One of its 5 m diameter, 8 m length ball mills was emptied to measure the ball size distribution. The broken balls were first separated from the total charge, and the remaining balls classified into five size intervals of +70 mm, -70 +60 mm, -60+50 mm, -50+40 mm, -40 mm. The charge was composed of 280,534 balls (excluding broken balls) with a total mass of 305,180 kg. It was found that 4.0% of the balls were broken; the size distribution of the charge was also markedly different from the desired one, particularly for the small-sized balls. For instance, 9% of the balls were expected to measure 2.54 to 3.18 cm in diameter, but none was found. On the other hand, the amount of top-size balls was 30% higher than expected. The radial hardness of balls, which was determined by cutting the balls in halves, showed that the hardness sharply drops when the balls become smaller than 65 mm. The unexpected ball size distribution was attributed to the rapid change in the ball's radial hardness. Based on the measured ball size distribution, a new ball makeup charge which uses 80% of 80 mm and 20% of 60 mm balls instead of 100% of 80 mm was proposed and implemented. The effect of the new ball makeup procedure in terms of ball consumption and grinding efficiency is being investigated.