Enhancing the Utilization Potential of a Low Grade Chromite Ore through Extensive Physical Separation

Abstract

Low grade chromite ore with less than 30% Cr₂O₃ was investigated with a view to enhance its utilization potential. The ore contained olivine, serpentine, and chrysotile as the gangue minerals. The chromite mineral contained alumina, magnesia, and FeO in its lattice. Critical mineralogical assessment indicated that enrichment to a level of 39-43% Cr₂O₃ may be possible. Beneficiation of the ore was undertaken using gravity based methods. Inadequate liberation prevented any significant enrichment at 0.9 mm top size. At 0.3 mm top size, the spiral concentration generated a concentrate with 40.5% Cr₂O₃ from the coarser fraction. The finer fraction was treated in a shaking table to generate another concentrate with 41.6% Cr₂O₃. The final combined concentrate assayed 41.2% Cr2O3 with a Cr/Fe ratio of 2.27. The middling from both treatments were rich in chromite content and were recommended to be included in the concentrates. Chromite recovery from the coarse reject was also beneficial. It was recommended that 8-10% solids content of the reject stream with 0.02 kg/t of Magnafloc flocculant may be used to achieve best settling characteristics of the reject fines.

Keywords:

• liberation
• spiral concentration
• tabling
• settling
• flocculation