Abstract

The final disposal in tailing dams using more concentrated slurries presents several advantages when compared with the conventional disposal due to some aspects: greater operational safety of the dams located in seismic regions, greater water recovery from the mineral process, reduction of the water evaporation in arid regions, greater ease of recovery of the land disposal and less environmental impact. The objective of the present work is to compare three different dewatering techniques applied to tailings obtained from the industrial process of phosphatic ores. The techniques evaluated were: deep cone thickener, paste thickener and hyperbaric filtration. The main results obtained showed: a) specific gravity of the sample is 3.06 g/cm3; b) the size distribution indicated 100% passing in 30 microns; c) the chemical analysis showed that magnesium, calcium and phosphorus are the more important elements; d) mineralogical analysis indicated predominance of calcite and dolomite; e) the sample presented a high value of specific surface area reaching the value of 0.976 m2/g; f) considering the techniques used, were obtained the following underflow concentrations in mass (w/w): 63% for deep cone thickener, 70% for paste thickener and 91% for the hyperbaric filter; g) the overflow turbidity levels obtained from deep cone thickener and paste thickener did not exceed the value of 100 NTU, while for the filtrate of the hyperbaric filter the value was 800 NTU; h) the yield stress values obtained were: 50 Pa for deep cone thickener and 200 Pa for paste thickener. The technique of dewatering more efficient for final disposal in tailings dams was the hyperbaric filter followed by the thickeners of paste and deep cone respectively.