doi:10.3808/jei.200800108
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Parametric Modeling of Polymer-Assisted Slurry Sedimentation for Nickel Laterite Mining

S. Azam*

Environmental Systems Engineering, University of Regina, Regina, Saskathewan S4S 0A2, Canada

*Corresponding author. Tel: +1 306 3372369 Fax: +1 306 5854855 Email: shahid.azam@uregina.ca

Abstract


The increasing world nickel demand coupled with depleting laterite reserves throughout the globe requires that metal extraction be extended to the entire ore body. To improve process throughput, the sedimentation behaviour of blended laterite slurries is modified in gravity thickeners using synthetic polymers. Based on 2^4 factorial design, ionic type, charge density, molecular weight, and dosage of polymers were varied in bench-scale sedimentation tests. An improvement of 20 times and a decrease of four times were observed in the ki of the selected ore slurry. The corresponding ef was found to range from 7.6 (sf = 29.3%) to 10.8 (sf = 22.7%). The sedimentation behaviour of polymer-modified slurries was found to obey linear ki versus ef relationships following direct proportionality for flocculation and inverse proportionality for dispersion. Test data were used in the analysis of variance (ANOVA) to develop a parametric model for predicting ki (ef obtained from the ki versus ef relationships) and deciphering the relative significance of the various polymer parameters on ki variability. A new term, “parametric factor†(PF) that combined the various polymer parameters, was defined and used to understand the complex colloid-water-polymer interactions. The significance of polymer parameters varied in the order C, M, T, and D and both the ki and ef were maximized for a PF = 2.25 x 10-7 mol/L. The optimum polymer parameters for an improved sedimentation of the selected slurry were found to be T = cationic, C = 15%, M = 12 × 106 g/mol, and D = 4 mg/L.

Keywords: parametric modeling, polymer modification, slurry sedimentation, nickel laterites, mining engineering, gravity thickeners, hydraulic conductivity, void ratio


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