Processing of mill tailings in flocculant-assisted hydrocyclone with application to mine backfill preparation

Potential benefits of flocculant-assisted hydrocyclone in hydraulic backfill preparation from mill tailings were investigated through test work performed at both the laboratory and plant scale. Properties of flocculated backfill were also evaluated. The study was prompted by the need to improve the quality and quantity of the hydraulic backfill used in mines.;Standard cylinder settling tests were performed to assess the effectiveness of flocculation at various flocculant dosages and with different methods of flocculant solution preparation, as well as to test whether the flocculated-fill would retain its flocculant properties under typical handling operations in the plant. The settling rate was affected to some degree by different preparation methods of flocculant solution and by flocculated-fill handling; however, the largest effect occurred with the flocculant dosage. The settling rate was high at relatively low dosages of flocculant, but over-dosage had an adverse effect. The optimum flocculant dosage is likely to vary in practice, depending upon the particular conditions and circumstances under which the flocculation process is applied.;In the plant tests, a 5% higher recovery of solid to cyclone underflow was obtained at a flocculant dosage of 41 g/t compared to the recovery without flocculant. Flocculant proved to be more successful below a cyclone feed pulp density of 15%, as was demonstrated by both the laboratory and the plant tests. It was also found that for the flocculant to work properly, it needed to be applied in diluted form.;A series of permeability tests verified that flocculant had a positive effect on the permeability of hydraulic fills. The coefficient of permeability increased with increasing flocculant dosage and void ratio of hydraulic fill.;On the other hand, according to rheological and flowability tests, flocculant had a negative effect on the transportation properties of hydraulic fill slurry. Viscosity with flocculant increased slightly in comparison with no flocculant addition at different shear rates. Flocculant also lowered the flow rate of the tailing slurries.;Uniaxial compressive strength (UCS) tests indicated that hydraulic backfill production from flocculant-assisted hydrocyclone may provide savings in cement and electricity consumption. A 40% higher UCS value was obtained with a flocculant dosage of 41 g/t compared to the UCS without flocculant (i.e. 143 psi vs. 102 psi) after 14 days of curing. The UCS increased with increasing flocculant dosage.;Furthermore, higher recovery of solids from flocculant-assisted hydrocyclone would mean less environmental impact due to smaller amount of tailings that would need to be deposited into tailings dams.