Converting AG to SAG mills: The Gol-E-Gohar Iron Ore Company case

At the concentration plant of the Gol-E-Gohar Iron Ore Company (Iran) three 9 m × 2.05 m AG (autogenous) mills (fixed speed) are used in parallel in a dry operation. The performance of AG mills has been lower than the target value indicated by an increase in the product size (P80; 80% passing size) from 450 μm (target) to 515 μm and low power draw (50% of nominal). By simulation it was found that increasing the liner lifter face angle from 7 to 30° while keeping the original lifter height (i.e., 22.5 cm) could provide an appropriate charge trajectory. When the proposed liners installed in one of the AG mills, the throughput increased by 27%; when 5% (v/v balls were added the throughput increased by 40%. The product size also decreased from 515 to 501 μm.