Dewatering of Fine Tailings for Disposal in Dams Using a Column Thickener, Deep Cone Classifier, and Hyperbaric Filtration
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Dewatering tailings to higher grades than paste produces a stable deposit that typically does not require retention dams and is called a \dry stack.\ A proposal of different dewatering techniques applied in the fine tailings produced after final desliming phase, obtained from the treating of phosphatic ores, is the main objective of this work. The dewatering techniques evaluated were column thickener, deep cone classifier, and hyperbaric filtration. Calcite and dolomite were the main mineral contained in the phosphate tailings and these have a very fine granulometry; the tailings presented different behaviours related to the dewatering technique applied. The test column thickener and deep cone classifier with the best operational parameters found to obtain a maximum percentage of solids in mass were similar to 71%25 and similar to 67%25, with values of yield stress similar to 200 Pa and similar to 100 Pa, respectively. In the hyperbaric filtration, a cake with similar to 10%25 moisture was obtained. This indicates that the transportation conditions are not the same. The overflow turbidity levels obtained from column thickener and deep cone classifier test did not exceed the value 100 NTU, whilst for the filtrate of the hyperbaric filter obtained values similar to 800 NTU. It was possible to preliminary estimate the recovery direct of water, considering each dewatering technique for final disposal of the tailings. The best dewatering techniques obtained were in the following order for the disposal in phosphate fine tailings dams; the hyperbaric filter showed an excellent dewatering capacity with productions rates around 160 kg h(-1) m(-2) for moisture cake of 10%25, followed by the column thickener and deep cone classifier with paste similar to 71%25 of solids (W/W) and high-density slurry similar to 67%25 of solids (W/W), respectively.
