Rheology of nickel tailings slurries - concentration and temperature effects

Abstract

Queensland Nickel's tailings slurries contain a high concentration of dissolved ammonia. The ammonia is stripped by steam in a multi-stage bubble cap still. Blocking of the hubble caps by settling tailings is a common occurrence. This is undesirable as it affects the overall productivity of the plant. Understanding the settling, time-dependent and rheological behaviour of the tailings slurries is an important step towards solving this problem. The tailings slurries display yield stress and shear thinning behaviour where the viscosity decreases with increasing shear rate. At concentrations greater than 50wt% solids the yield stress and viscosity increases exponentially with concentration. Temperature appears to have only a small effect on the viscosity and yield stress. The time scale of settling for low solids slurry of 22.2wt% is relatively fast, in minutes, while that for the 50wt% sluny is in hours.