Bubble Size Analysis and Boundary Conditions for Automatic Control of Industrial Flotation Cells

The gas dispersion has a high impact on flotation processes performance. To evaluate this effect, the bubble surface area flux (Sb) must be evaluated from superficial gas rate (Jg) and Sauter mean bubble diameter (D32) local measurements at industrial scale. Gas rate sensors and visual bubble caption techniques (video, photograph) have been developed successfully, but the commercial software for automated image analysis still has troubles when irregular big size bubbles and bubble clusters appears in industrial measurements, which prevents an accurate and more reliable bubble size estimation. Also, a criteria for bubble size distribution (BSD) diagnostic and control at industrial scale, has not been developed yet.In this work, measurements of BSD were carried out in large flotation cells, of different size, operating in several flotation circuits in Chile. Also, new semi-automatic software for image analysis was developed to overcome the troubles before mentioned and permitting more reliable bubble size estimations. Experimental results showed that under normal operating conditions BSD matched well with a lognormal distribution. From this reference two types of operating problems has been identified and the corresponding diagnosis criteria were established, which is a powerful tool for automatic control purposes.