Improved suspension dewaterability using a novel pelleting flocculation device

Abstract

The decline in ore grades and increasing clay content in ore bodies present significant dewatering challenges for the mining industry, as finer grinding is required to liberate target minerals. This results in the production of fine mineral gangue, including clay minerals, which are discharged as tailings. Tailings are typically treated with flocculants to aggregate fine particles, improving settling and permeability. However, flocculation forms strong particle networks with reduced compressibility, constraining thickened slurry density and filter cake moisture.

This study demonstrates a novel vertical screw pelletiser prototype for pelleting flocculation of kaolin suspensions, aimed at improving both compressibility and permeability by forming compact pelletised aggregates. Using an oil-in-water emulsion and a polymer flocculant for adhesion, kaolin particles with a Sauter diameter of 1.4 µm were aggregated and pelletised into centimetre-sized pellets with solids fraction up to 0.15 v/v (0.31 w/w).

The dewatering properties of the pellets were quantified and modelled using comprehensive dewaterability analysis. Compared to the conventional flocculation methods, which typically improve permeability at the expense of compressibility, pelleting flocculation improved both the compressibility and permeability. The thickener modelling showed that, to achieve an underflow solids concentration of 0.20 v/v (0.40 w/w), systems fed with pelletised aggregates could operate at a solid flux 13 times higher than those using conventional flocculated aggregates. Similarly, to achieve a filter cake solids concentration of 0.40 v/v (0.64 w/w), filters fed with pelletised aggregates required 16 % less filtration area and 18 % shorter filtration time compared to conventional flocculated feeds. This work highlights pelleting flocculation as a promising alternative to conventional flocculation, resulting in significant improvements in the thickener performance and offering a practical solution to the challenges of processing fine and clay-rich tailings in mineral processing.