Laboratory flotation tests have been conducted to examine the effect of fro
th stability on the column flotation of finely pulverized coal. It has been
demonstrated that the upgrading of coal in a flotation column can be signi
ficantly improved when froth stability is properly controlled through the m
anipulation of appropriate variables such as gas flow rate (V-g), wash wate
r 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 hi
gher 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 frot
her dosage was maintained. Coal particles could stabilize or destabilize th
e froth, depending on their size and concentration in the cell. Those in -1
00 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 es
tablished at varying wash water flow rates and wash water addition points,
from which it was concluded that froth cleaning occurred primarily at the p
ulp-froth interface and drainage above the wash water addition point. (C) 2
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