Column flotation froths

A fundamental study on the behaviour of flotation column froths is presented. Three main aspects were considered: hydrodynamic, cleaning (rejection of hydraulically entrained particles) and selectivity (separation between particles of different hydrophobicity).Column froth hydrodynamics were studied in a two phase (gas-liquid) system. A model to estimate gas holdup from electrical conductivity was developed. Bubble coalescence was evaluated by means of local measurement of gas holdup and bubble size distribution, consequently bubble surface loss along the froth was determined. Mathematical models are developed to describe liquid entrainment and drainage throughout the froth.The cleaning action was evaluated by monitoring feed water penetration at different levels in the froth, which corresponds to the boundary (worst) condition of fine particles entrainment. Laboratory and plant-scale tracer tests showed that the main cleaning action occurs close to the froth/collection zone interface.Local grade and solids percentage along column froths, together with a mathematical model describing mass transport, was used to analyse mineral selectivity in column froths. Quantification of mineral loss from the froth, due to detachment and cleaning, is presented.A generalized model to describe particle settling against a bubble swarm was developed. Entrainment and segregation of particles in the wake of bubbles gives insight into the characteristics of the pulp entering the froth in a flotation column