The relationship between particle size, cell design and air recovery: the effect on flotation performance

Froth flotation is an established method of separating mineral from its associated ore. Although there has been many years of research and development, there remains much room for development. A 4 L bench-scale, continuously overflowing and recycling single species flotation system was developed for this work. It was used to investigate the effect of particle size and retrofit designs on air recovery, a measure of froth stability, as well as the solid and liquid flowrates of the system. Particle size had an effect on air recovery and flotation performance. An increase in solids flowrate corresponded with a decrease in the particle size in the concentrate. When air recovery was below 50 %, the peak in solids flowrate corresponded with the peak in air recovery. The addition of a retrofit design, a horizontal mesh of varying hole-size and thickness, was tested at a range of superficial gas velocities in a three-way full factorial trial. It was shown that a mesh of 30 mm hole-size and 40 mm thickness resulted in a statistically significant improvement in solids flowrate to the concentrate, when compared with the unmodified base case. Position Emission Particle Tracking (PEPT) provided an opportunity to make qualitative and quantitative assessments of particle behaviour within the pulp and froth. PEPT data indicated that in the unmodified base case, swirl from the pulp continued in the lower froth, a behaviour never observed before. Variation in mesh hole-size lead to visible changes in tracer trajectories, and an increase in mesh thickness resulted in both tracers entering the froth more frequently. This work has developed a novel experimental system capable of determining the effects of a range of operational and design parameters on air recovery and flotation performance, and has corroborated and justified the trends seen through statistical analysis and novel imaging techniques.Open Acces