Digital image processing as a tool for on-line monitoring of froth in flotation plants

Abstract As the most important separation technique in mineral processing, flotation has been the subject of intensive investigation over many years, but despite these efforts it remains a poorly understood process that defies generally useful mathematical modelling. As a result the control of industrial flotation plants is often based on the visual appearance of the froth phase, and depends to a large extent on the experience and ability of a human operator. These types of processes are consequently often controlled suboptimally owing to high personnel turnover, lack of fundamental understanding of plant dynamics, inaccuracy or unreliability of manual control systems, etc. By using techniques based on image colour analysis and Fast Fourier Transforms to process videographic data of the froth phase in a copper flotation plant, it is shown that an image processing system can distinguish between different copper levels in the froth down a rougher bank and extract global features from the visual characteristics of the surface froth. In this way it is possible to quantify the mineral content of the froth (based on colour), the average bubble size distribution, the direction of flow and the shape of the bubbles or the mobility of the froth. The overall image of the froth is analysed instead of attempting to identify the boundaries between bubbles.