Challenges in flotation scale-up: The impact of flotation kinetics and froth transport

Abstract

At present, data from industrial flotation operations is still limited and more tests and in-depth studies are required to improve the experimental procedures, measurement devices and analysis, to validate and interpret scale-up factors from batch to plant flotation operations.The new methodologies have contributed to improve predictions of flotation metallurgical performance using more refined scale-up methods, for example, analyzing the scale-up factor by size and liberation classes. These will allow for selecting the best equipment for each mineral and flotation stage (rougher, cleaner and scavenger).In this work, the effect of the pulp zone hydrodynamics affecting the collection residence time and flotation kinetics, and the froth transport, on the overall scale-up factors (typically around 1.8–2.3) was evaluated per particle size classes in the range of 22.5 to 300 µm. Two effects were found that partially explain the scale-up factor in the pulp zone, such as the pulp mixing regime (4–16%) depending on the cells number, and the solids segregation (2–7%) that decreases the residence time of larger particles. However, the most important contribution was the froth transport characteristics that determines the froth recovery which accounted for 48–58% of the scale-up factor, also increasing with particle size. In addition, it was found that the remaining percentage of the overall scale-up factor, around 31%, includes the uncertainty in the collection residence time estimation, which is lower than the effective pulp residence time, and the larger residence time of bubbles in industrial cells. Both effects hinder the identification of the actual flotation rate in the pulp zone.