Optimal Water Recovery with Emphasis on Flocculant Consumption Rate in the Thickener

Water plays a vital role in mineral processing as evidenced by the approximately 2 to 3 tons of water used for the treatment of one ton of ore. A major portion of this water may be recovered in thickeners. This study aimed to control the wet tailings output of the Hematite Gol-e-Gohar plant by changing  flocculant dosage and type and solid percentage in the feed in order to enhance effluent clarity and reduce water consumption. Materials and A series of settling experiments were performed using different combinations of the flocculants (A25, A26 Yazd, A26 Esfahan, A27, and A28), flocculant doses (20, 25, 30, 35, and 40 gr/ton), and solid loads in the feed (5, 7, 9, 10, and 11%) to the thickener. The L25 Taguchi design method was chosen to handle the five different levels of the three factors. Adopting a 95% confidence interval, the results of analysis of variance (ANOVA) revealed that flocculant consumption rate had a high effect on settling velocity (p = 0.006) while flocculant type and solid percentage in the feed had no significant effects. Moreover, it was found that A26 (Akhtar-chemistry Company, Yazd) used at a rate of 40 g/ton improved the settling performance to yield an optimal water clarity. Using the findings of this study in process planning at the plant led to a considerable reduction (from the original 0.86 to 0.49 m3) in average water consumption per ton of input material so that the solid content of the thickener underflow rose from 7 to 45%.