Investigation of the flotation behaviour of ball mill and IsaMill products

Master Thesis


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University of Cape Town

Valuable minerals that are used in various aspects of everyday life are buried in fossilised storages below the ground in the earth's crust. These minerals are mined as rocks which then have to be crushed in order to liberate these minerals of value. The liberated valuable minerals have to be winnowed from the rock powder. Flotation is the main process which is used in mineral processing to recover valuable minerals. This process uses the differences in surface properties of particles to separate hydrophobic particles from hydrophilic ones. The strong relationship between the method of crushing the rocks and the amount of valuable minerals which can be reclaimed from the crushed rock has long been realized in mineral processing. The type of mineral, the size to which the rock must be reduced to and the amount of energy needed for this size reduction are among the most important factors which guide the decision on the type of device to be used in pulverising mineral rocks. Physical properties, with the exception of particle size, of mill products have not been investigated as thoroughly as the chemical properties. Physical properties include surface roughness and particle shape. The differences in shape, between particles produced by different mills, with respect to these properties, have been attributed to differences in the breakage mechanisms in the mills used to grind the particles. There is contradicting literature on the breakage mechanisms that dominate in various mills. This confusion is exacerbated by the fact that different breakage mechanisms occur simultaneously in any one mill. The definition and determination of particle shape are also difficult. Subsequently, the effect of particle shape on flotation is a subject that is rife with contradictions which add to the complexity of the subject.

Includes bibliographical references.