The effect of frothers on bubble size distributions in flotation pulp phases and surface froths

Froth dynamics, i.e. the stability and mobility of the froth, are crucial i ndicators of various important features of flotation systems. For example, it is desirable that the froth collapses as soon as possible after it is sk immed off the cell in order to curtail losses in throughput. On the other h and, if the froth is too prone to collapse, it will not be sufficiently sta ble to support its load prior to skimming. Likewise, the mobility of the fr oth gives similar information on the performance of the flotation cell. For example, a sharp contrast can be observed between dry viscous (immobile) f roths and watery runny froths with high mobility. Several authors have rece ntly, shown that analysis of the structure of the froth in a flotation cell can be used to assess the performance of the cell. This implies that there is a close relationship between the bubble size distribution in the pulp a nd froth phases. Until very recently, it was not possible to verify, this hypothesis direct, since reliable measurements of bubble size distributions in especially the froth phase could not be obtained. With recent improvements in the machine vision technology originally developed at the University of Stellenbosch, it is now possible to measure bubble size distributions and stability in fr oth structure with a high degree of accuracy. Unlike previous methods, thes e improved algorithms can provide a derailed map of flow patterns in the fr oths, which can give a significantly better idea of operating conditions in the flotation cell. Consequently, in this experimental study the bubble si ze distribution in the pulp phase of a laboratory flotation cell was measur ement with a capillary tube system (UCT bubble size analyser;), while the b ubble size distribution in the froth phase was measured by use of digital i mage analysis. The relationship between these bubble size distributions in the pulp and froth phases is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.