TROUBLESHOOTING INDUSTRIAL FLOTATION COLUMNS

Since the early 1980s flotation columns have been progressively incorp orated in milling operations all over the world. Improvements in final concentrate grade, using single cleaning stages, have been in most ca ses the reason for using this new technology. However, the main disadv antage with respect to conventional mechanical cells is the large spre ad of results, mainly in terms of recovery, which is normally compensa ted by a high circulating load and high capacities (overdesign). Besid es normal changes in Seed grade and flowrate, and the need for periodi c maintenance for gas spargers, the following common troubles in plant practice are discussed: improper calibration and maintenance of instr umentation to measure froth depth and gas rate bias definition and est imation uneven wash water distribution uneven froth depth in baffled c olumns lack of robustness of control strategies Proper boundaries for superficial wash water rate (0.1-0.2 cm/s), froth depth (0.5-1.0 m) an d superficial gas rate (1-2 cm/s), based on fundamental knowledge and experience in large size columns, are suggested for stable operation. Unfortunately, the lack of coordination between these variables is an important limitation for metallurgical improvements. The effect of alt itude on gas rate and gas holdup in flotation columns operating at 150 0-4500 m over the sea level is analysed.