Troubleshooting and Diagnostic of Industrial Flotation Cells

Abstract

The residence time distribution of liquid, gas and solid per size class was measured in large flotation cells in different flotation plants. The RTD measurement was developed using radioactive tracers. Results allowed the estimation of effective pulp volumes of 82–85% of the total nominal volume in large flotation cells. It was found that single large industrial flotation cells have different flow regimes and can be significantly different from a perfect mixer (N>1 or N<1). Measurement of RTD also allowed the identification of operating control problems such as solid segregation (affecting the mean residence time for kinetic modeling), cells embankment, and increasing short-circuit because of cell design characteristics and circuit arrangement (i.e. input-output location). Measurement of local superficial gas rate and improved measurement of bubble size distribution, using new software, allowed the estimation of the bubble surface area flux (S B around 40s −-1 ), key parameter describing the quality (level) of gas dispersion in industrial flotation cells. Also, typical boundaries for superficial gas rate (1–2 cm/s) and mean bubble size (1–2mm) have been identified for stable flotation operation from different plant experiences. Bubble load measurement was carried out for estimating the froth recovery in large flotation cells. Froth recovery is relevant for flotation process modeling and control because of the critical role the froth transport plays in large cells. Recent development on automated froth visual analysis (i.e., bubble size, bubble collapse and froth overflow velocity) poses new challenges to link this information with the actual internal process variables (i.e. froth recovery).