A parametric study of froth stability and its effect on column flotation of fine particles

Laboratory flotation tests have been conducted to examine the effect of froth stability on the column flotation of finely pulverized coal. It has been demonstrated that the upgrading of coal in a flotation column can be significantly improved when froth stability is properly controlled through the manipulation of appropriate variables such as gas flow rate (V-g), wash water flow rate (V-w), froth height, wash water addition point, and feed solid concentration. Increases in wash water flow rate and gas flow rate promoted froth stability, resulting in higher combustible recovery, but possibly higher ash recovery as well. The optimum rates were determined to be 2 and 0.3 cm/s for V-g and V-w, respectively. The specific influence of wash water flow rate on water recovery was found to be closely related to how the frother dosage was maintained. Coal particles could stabilize or destabilize the froth, depending on their size and concentration in the cell. Those in -100 mesh fraction destabilized froth at lower concentrations and stabilized it at higher concentrations while micronized particles always showed froth-breaking power. The froth profiles of solid content and ash content were established at varying wash water flow rates and wash water addition points, from which it was concluded that froth cleaning occurred primarily at the pulp-froth interface and drainage above the wash water addition point. (C) 2000 Elsevier Science B.V. AU rights reserved.