Effects of ballasting particles on settling rate of iron ore tailings

The high density or large size grains are proposed to be added as ballasting particles to achieve a high settling rate and low supernatant turbidity for fine particle flocs during the settlement of ore tailings. Settling tests on iron ore tailings were carried out to evaluate the effects of size, density, and dosage of ballasting particles on initial settling rate and turbidity. The results showed that low density (2.65 g/cm(3)) particles and medium density (4.67 g/cm(3)) particles contributed to the increase in settling rate of the tailing slurry at all size fractions from 0.074 to 0.5 mm, with the peak performance obtained between 0.125-0.2 mm, whereas high density (6.14 g/cm(3)) particles only accelerated the process with the particle size not larger than 0.2 mm. It is supposed that there is a close relationship between ballasting particle properties and floc strength. The acceleration effect dominates when flocs are strong enough to bear the ballasting particles; deceleration occurs when ballasting particles are oversize, over-density, or overdosed, causing the breakage of flocs.