Influence of Grinding and Classification Circuit on the Performance of Iron Ore Beneficiation - A Plant Scale Study

Process flowsheet has a greater effect on equipment performance and operating conditions. For this purpose, performance of two iron ore beneficiation plants with the same equipment and feed characteristics but different arrangements in the grinding and classification circuit has been investigated. The first difference between the two plants was the screening type of HPGR product. Wet screening in the second plant caused higher classification efficiency, decreasing the circulating load, removing the dust production during operation. Wet screening caused to increased the moisture of HPGR feed which helped in improving the lifetime of HPGR rolls by a protective layer on the surfaces of HPGR rolls and between studs. Furthermore, it led to a reduction of HPGR feed rate, roll speed, and operating pressure. The feed rate of Ball mill in the second plant is lower and it has a finer product. As a result, ball consumption and rejected materials from trommel screen was decreased and pulp lifters lifetime was increased. In the second plant as well as the first plant,, the same hydrocyclone overflow d(80) was achieved under lower operating pressure and the larger vortex finder diameter but the wear rate of hydrocyclone's internal parts has been approximately double. The iron grade of tailings in the second plant was lesser by 2% and the iron recovery noted to be higher by 2%. The energy consumption decreased by 2 kWh/t of the ground ore in the second plant. As a result, the second plant was considered to be more efficient.