Investigations of gas holdup, interfacial area of bubbles and bubble size distributions in a pilot plant flotation column

Abstract

Hydrodynamic variables in flotation columns can affect flotation conditions. This paper discusses the relationships between bubble size distributions, gas holdups, interfacial area of bubbles and flotation kinetics by changing four factors: air velocity, solid percentage, frother dosage and particle size. The results demonstrated that the gas holdups were particularly affected by the solid percentage. The increase in the solid percentage resulted in higher bubble loadings, making air bubbles more stable and thus increasing gas holdups. The results showed that the gas holdups were directly proportional to the interfacial areas of bubbles. This is true when the interfacial areas of bubbles were modeled using either the Sauter mean diameters or the log-normal bubble size distributions. The bubble sizes were reduced predominantly in the case of the highest pulp densities. Thus, there were significant collisions between bubbles and particles, leading to high flotation rate constants. These results showed that the knowledge about bubble size distributions and gas holdups are required to explain the flotation kinetics at different flotation conditions.