Development of a froth dropback measurement device

This paper presents the development of a new device which can collect the detached particles from the froth phase directly as they fall out of the froth. The device consists of two concentric tubes separated by 10 mm gap and attached to a fl otation column. The bubbles are loaded in the column and rise through the gap between two tubes where a stable froth is formed. The particles that detach from the froth phase are collected in the inner tube, known as dropback chamber. Both dropback and concentrate particles are collected, weighed and froth recovery is measured as fraction of particles entering froth phase attached to air bubbles transferred as concentrate. Experiments have been performed using mixture of fi ne (60 G, d₉₀ = 110 μm) and coarse (50 N, d₉₀ = 370 μm) silica. The infl uence of froth depth and the gap between the pulp froth interface and dropback catcher on froth recovery has been investigated. Experiments have also been carried out varying the percentage of coarse particles in the feed. Results have shown that the presence of coarse particles has a detrimental effect on the froth recovery as well as on the froth stability