Hydrodynamic and metallurgical characterization of industrial flotation banks for control purposes

An industrial flotation circuit consisting of five parallel rougher flotation banks, each bank provided with 9 cells of 42.5 m(3), was characterized. The airflow rate delivered over the cross-sectional area was directly measured using a simple device that provides a continuous measurement of local gas flow rate. The range of superficial gas rate was 0.8-1.2 cm/s. Gas holdup was measured using a pulp sampler providing estimations of local gas holdup of 15-22%. Bubble size distribution was measured using the UCT bubble size analyzer and the mean bubble size was compared with direct observations of the bubble size distribution near the pulp/froth interface. The Sauter average bubble size observed was 0.9-1.1 mm. The effective residence time of the liquid and solid phases was evaluated from residence time distribution (RTD) measurements, using radioactive tracers. The mean solid residence time was 5% lower than the mean liquid residence time. RTD of non-floatable mineral was also evaluated at different particle size classes. Measurements of grade, solid percentage and particle size profiles from the top to the bottom of different cells along the bank gave a complete diagnosis of particle distribution and mixing. The use of compressed air and the effect of pulp level on the bank flotation kinetics was evaluated. Thus, a useful correlation between mass recovery and enrichment ratio from industrial flotation cells was found for control purposes. (C) 2001 Published by Elsevier Science Ltd. All rights reserved.