Physics of Novel System Hydrodynamics

NO TITLE LEADER & KEY PERSONNEL PROJECT SUMMARIES

P1.4 Solid-Liquid Separation and Dewatering

28 Investigation of water expression from thickened suspensions using high pressure dewatering rolls

Leader: Dr Anthony Stickland (UOM)

Key Personnel: Prof Peter Scales (UOM)

Prof Ken Williams (UON)

PhD Student: Sajid Hassan (UOM)

29 Influence of oscillatory motions on water migration, liquefaction and dewatering Leader: Prof Ken Williams (UON)

Key Personnel:

Dr Dusan Ilic, RA (UON)

PhD Student: Virat Gurung (UON)

This project is developing a new high pressure and clothless filtration technology for tailings dewatering. Designing and building a new prototype using wedge wire as the filtration surface has been completed, incorporating sensing and control systems. Engagement with a mining company has allowed demonstration of the High-Pressure Dewatering Roll (HPDR) to reduce cake moisture for mineral tailings from one of the world’s largest mines, comparable to that of filter presses but potentially less costly. A one-dimensional filtration model has been developed to support scale-up estimates. A two-fluid CFD model has been developed for solid-liquid separation that has demonstrated the potential for cake erosion.

30 Application of G forces in the expression of water from concentrated suspensions

Leader: Prof Anh Nguyen (UQ)

Key Personnel:

Prof Roe-Hoan Yoon, AI (VT)

Dr Liguang Wang, AI (UQ)

PhD Student: Andrew Doi (UQ)

Many mining operations are transitioning to pressure or centrifugation-enhanced dewatering methods to reduce the water content in their tailings streams. This project is exploring the relationship between chemical selection and dewatering in centrifugation systems. A range of dewatering reagents has been acquired, including PAM-based flocculants with different molecular structures, weights, and charge densities (low and high molecular weight anionic PAM with different charged densities (10% - 55%) and similar molecular weight, and high molecular weight cationic PAM). The chemical screening was completed using two fine-tailing samples and an in-house settling testing method. The six most effective reagents were selected for pilot-scale dewatering experiments using a solid bowl centrifuge. The cakes were characterised for rheological properties (yield stress, tack energy, stickiness) to assess the handleability and co-disposability of fine tailings with coarse rejects. Suitably selected chemicals were found to increase the performance of the dewatering process and enhance the handleability and co-disposability of the dewatered cakes. The co-disposal of dewatered fine tailings is found to be a good strategy for dry stacking tailings management.

This project uses novel oscillatory, low frequency motions to induce moisture migration through a concentrated sediment, which could lead to in-situ mechanical dewatering at low cost.

Theoretical models have been reviewed and summarised. Experiments are being conducted to measure dynamic moisture migration in partially saturated bulk solids. The measurements have initially focused on idealised soda lime silica glass beads in different size ranges (1-1.2, 2-2.5, 3.5-4 and 8-9 mm). Experiments to measure free-drained moisture content, bulk and particle densities have also been conducted. Trial simulations using DEM-SPH (Discrete Element Modelling, Smoothed-Particle Hydrodynamics) coupling have been explored at different scales (bulk and micro).

Leader: Prof Peter Scales (UOM)

Key Personnel:

L/Prof Kevin Galvin (UON) Dr Anthony Stickland (UOM)

Flocculation of tailings streams using high-molecular weight polymeric additives is the mainstay of dewatering and tailings management practice in the minerals industry. The key role of the polymeric additive is to increase the settling rate and hence the permeability of the particulate suspension. This same process increases the strength of the particulate bed and reduces the attainable solids concentration. In short, the minerals industry has always favoured speed of water removal over extent. This project looks to include an oil phase to the flocculated aggregate to provide a route to a low shear pelletisation processes. The work uses a model tailings suspension and an oil emulsion system (with analogies to road aggregate binders) for aggregation, along with conventional flocculants. Laboratory trials show both aggregation and densification in a helical uplift pelletiser. A continuous flow system is now being built.

32 Ultrafast particle recovery through formation of small hydrophobic aggregates

Leader: Prof George Franks (UOM)

Key Personnel:

A/Prof Liza Forbes (UQ)

Dr Eirini Goudeli, AI (UOM)

PhD Students:

Jackquline Eardley (UOM)

Lequan Zeng (UOM)

Selective aggregation of ultrafine particles to improve flotation recovery is an important aspect of decreasing the loss of valuable materials to waste. Adsorption isotherms and zeta potential measurements have been used to understand the adsorption of commercial reagents, including flocculants, dispersants, and collectors on the aggregation of quartz and hematite. The flocculated particles were made to attach to bubbles (generated by shaking a jar) with the addition of an appropriate surfactant. A techno-economic assessment of the process has been completed. A combined DEM-CFD simulation has been developed to determine the aggregation and breakage kernels of fine particles in environments like those found in flotation cells.