Effect of Rheology on Filtration of a Brecciated Limestone Ore Slurry

Abstract

The rheological behavior of the ore slurry plays a critical role in most of the mineral processing unit operations including filtration. This paper discusses the rheological tests conducted on a brecciated limestone ore slurry and the attempt to correlate the rheological behavior of the slurry with the filtration rate. Rheological experiments were carried out using a modular compact Rheometer. Solid concentration, temperature, particle size and particle size distribution (PSD) of the solids, shearing time, and surfactant dosages were found to have a significant impact on the slurry rheology. The Herschel–Bulkley model was used to describe the rheological behavior of the slurry. The variation of temperature was modeled using the Arrhenius type model equation, and the particle size distribution was incorporated using the Rosin–Rammler PSD model. It was found that the shear stress increased exponentially with an increase in solid concentration and a decrease in temperature. The maximum solid packing volume fraction was determined to be 0.647 and 0.569 at shear rates of 1400 and 503 s−1, respectively. The fluid flow activation energy was found to be 5.76 and 7.67 kJ/mol at 50% and 73% solids (w/w) respectively at a shear rate of 1120 s−1. Filtration rate was found to increase with an increase in temperature, particle size, and decrease in solid concentration. The addition of a surfactant, namely Guar gum to the slurry (up to 500 g/t), has not increased the shear stress (<23.4 Pa) or apparent viscosity (<0.0167 Pa·s) appreciably but increased the rate of filtration.