Studies on the Rheological Characteristics of Flocculated Calcitic Ore Slurry

There are significant challenges associated with the settling and filtration of very fine-grained mineral particles. The present work aims at selecting the best dewatering aids that can improve filtration kinetics and filtrate quality (recycled process water) of a uranium ore processing plant. The effect of dewatering aids on slurry rheology and filtration of a calcitic ore containing 61.4% CaCO3 was investigated. The dewatering aids selected were polyacrylamide-based industrial flocculants of nonionic (NPAM-N100) and anionic (APAM- RF8180) type, an anionic surfactant (ASLS-sodium lauryl sulphate), and a nonionic exopolysaccharide surfactant (NEPS-guar gum). The slurry’s rheological behaviour was analyzed with the help of Herschel–Bulkley model. Optimum dosage of flocculant/surfactant was evaluated using rheological parameters. A wide variation in maximum shear stress (19.7–28.1 Pa) and maximum apparent viscosity (0.0141–0.0201 Pa.s) was noted with these dewatering aids at fixed shear rate of 862 s−1 (50% solids (w/w), ambient temperature 30 °C, d90 particle size 53 µm). The NPAM and NEPS gave best flocculation results at an optimum dosage of 90–110 g/t with a corresponding low capillary suction time (CST) and low zeta potential (−19 changed to −1.9 mV with 100 g/t NPAM, N100). An attempt was also made to correlate rheological parameters with CST values. The rheological parameters and zeta potential help in optimizing the dewatering aid dosages for better flocculation and filtration, and thereby reducing the overall production cost. Graphical Abstract: (Figure presented.). © The Institution of Engineers (India) 2023.