Recovery of Iron Values from Slimes and Dewatering of the Concentrate

Abstract

During crushing and wet processing of iron ore on an average 15- 18% slimes (-100 mesh) are produced in the iron ore mines of Nationa Mineral Development Corporation (NMDC). About 50 to 65% by weight of slimes can be rec- overed and upgraded to +64% Fe by process of hydrocycloning. By the process of wet high intensity magnetic separation, the magnetic concentrate assaying +65% Fe with similar recovery can be achieved. Dewatering of hydrocyclone underflow and magnetic concentrate can be carried out by slow speed spiral classification. The classifier sand contains about 18 to 20% moisture. During the process ofdewatering the grade of slow speed classifier sand gets improved further. The concentrate obtained by hydrocyclone meets the specifications for blending with normal classifier sand for sinter making. The magnetic concentrate obtained by WHIMS meet the DRJ pellet grade specification or for alternative method of iron making. There are difficulties for operation ofthickenerfor water recovery directly form classifier overflow due to higher solid content and fastersettling rate. After removal of major portion of ultrafines from slimes as concentrate, the thickener operation becomes smooth and troublefree. On an average 70 to 75% of input water can be recovered by thickener.