Effect of anionic flocculant on settling rate of iron ore ultra-fines

Abstract

The goethetic-hematite iron ore contains more goethite and kaolinite mineral. These mineral phases are more fragile nature. During crushing and screening, these phases generally report in the below 10 mm size fraction. The low grade fines generated during crushing and screening, is scrubbed using screw scrubber or screw classifier to remove below 100 µm size fractions. The overflow of screw scrubber contains mostly clay and goethite minerals which becomes difficult for settling. Hence the settling studies were carried out on this sample using anionic commercial flocculant at different solid concentration and flocculant dosages. It contains more than 96% of below 45 µm. The overflow contains 61.72% Fe(T), 3.91% SiO2, 3.81% Al2O3 and 3.94% LOI. The XRD and heating cycle studies were carried out to determine the mineral phase analysis. It contains around 65% hematite, 26% goethite and 9% kaolinite. Without addition of flocculant, the settling rate is at the desired level (2 m/hr) but at 35% solid concentration, the settling is very low (0.24 m/hr). The flocculant dosage was varied from 10 to 60 g/tonne of ore. It has been observed that at 10% solid concentration, minimum required dosage of flocculant is 10 g/tonne to achieve 2 m/hr settling rate. It has been observed that with increase in solid percentage, the settling rate of particles decreases. At 30% solid concentration, the requirement of flocculant is around 60 g/tonne. Once, the solid concentration of particles increases more than 30%, the settling rate becomes very slow even after adding the flocculant. In this study, the settling rate was optimised with respect to solid concentration and flocculant dosages.