Estimation of Air Fraction Profiles in the Stabilized Froth and Froth Regions of a Flotation Column Using Conductivity Probes

In the collection zone of a flotation column, the air holdup is known to be relatively constant along the column height. The effect of the decrease in hydrostatic pressure with height may need to be taken into consideration, particularly for tall industrial columns. However, this phenomenon is readily ascertained. On the other hand, the changes at the pulp-froth interface, as well as the air fraction profile in the stabilized froth and froth zones, are still the subjects of investigation. An abrupt transition in air fraction at the interface is normally observed, while the bubble size starts increasing at the base of the froth, reaching a value of about two millimeters (Yianatos et al., 1986; Biswal et al, 1994). Above the wash-water-addition point, the average bubble size grows rapidly and the air fraction generally increases to values greater than 0.8 (Yianatos et al., 1986).