Improving flocculation and dewatering performance of iron tailings thickeners

Most of the mineral processing and hydrometallurgical plants consume large volumes of water. A portion of this water is recycled to the process while the remainder is lost. This necessitates optimization of dewatering systems particularly in arid and semi-arid mining regions. In this paper the bench and full-scale flocculation behavior of iron ore tailings is investigated in order to improve the dewatering performance of tailings thickeners of an iron beneficiation plant. In the batch settling tests, the effect of flocculant dosage (5-20 g/t solid), slurry solids concentration (3-12 %), pH (4-12), and flocculant dilution (0.05-1 %) on the flocculation performance (settling rate, supernatant turbidity, and sediment volume) was studied. The results reveal that the flocculation performance improves at higher slurry pH and flocculate dosage as well as lower slurry solids content. In the plant-site experiments, the influence of increasing the slurry pH (from 8.1-11.2) and dosage of flocculant (from 8 to 13 g/t solid) together with flocculant injection strategy on the thickening performance was examined. The thickeners underflow density and overflow clarity increased with raising the slurry pH and flocculant dosage as well as distributing the flocculant solution at different locations along the feed stream. The proposed modifications were accompanied by a reduction of 23% in the total water consumption corresponding to an annual savings of $576,000.