Study of effect of process parameters and their interaction in the flotation of UG2 ore

Master Thesis


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University of Cape Town

Flotation is widely used in the mineral processing industry to extract valuable minerals from the ore. The fundamental steps in this separation process are the attachment of hydrophobic valuable minerals to bubbles, and the subsequent accumulation of the bubble-particle aggregates in the froth phase. Processing of UG2 ore for concentration of platinum group minerals (PGMs) is a challenging task. UG2 ore contains significant amounts of chromite which is hydrophilic in nature and reports to the concentrate by means of mechanical entrainment. This is a serious problem for the downstream smelting process, which generally has a constraint of 3 chromite. In order to optimise PGM and chromite grade and recovery in UG2 processing, a number of controls are available in a plant. Among the most important are froth height, air flow rate, depressant dosage and frother concentration. On an individual level, it is expected that an increase in froth height will result in the reduction of the mechanical entrainment of chromite due to an increase in the residence time of air in the froth zone, allowing more drainage of chromite from froth to pulp. High depressant dosage is expected to enhance the grade of PGM and will reduce the recovery of naturally floatable gangue in the concentrate. However, the increase of superficial air velocity will increase the water recovery and solid recovery, thus decreasing the PGM grade with a possible increase in recovery. Increase in frother concentration increases the thickness of bubble lamella and causes more water to flow through the Plateau borders and hence increases the water recovery. Apart from the individual effect of each process parameter the interaction of same play a significant role in the solid and water recovery that affect the chromite content and the PGM grade in the concentrate.

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