Kaiser, LK, Lamperd, JW, Loan, C & Cooling, DJ 2006, 'A New Approach to Bauxite Residue Dry Stacking: Utilizing Ciba® RHEOMAX™ ETD Technology', in R Jewell, S Lawson & P Newman (eds), Proceedings of the Ninth International Seminar on Paste and Thickened Tailings
, Australian Centre for Geomechanics, Perth, pp. 57-67.
Most mineral tailings are transported as slurry via a pipeline to a designated storage area. In principle, the
aims of above ground tailings storage are to contain the tailings, consolidate these tailings to maximise
storage efficiencies, aid rehabilitation, and maximise water recovery via efficient drainage and decant
systems. Recent advances in tailings management have focussed on thickening of the tailings prior to
deposition in the storage area to aid both consolidation and water recovery (Jewell et al, 2003). This is
commonly referred to as “thickened tailings disposal” or “sloped deposition”. These systems rely on
thickened slurry, which can be deposited in relatively thin layers on a sloped bed, allowing consolidation via
both gravity drainage and solar drying.
Over the past decade, significant advances have been made in the technology associated with thickening
dilute slurries (Arbuthnot et al., 2005; Crozier et al., 2005). Thickeners have become more efficient and
flocculants more effective. These advances have aided the development of thickened tailings disposal,
making the process more affordable. Many new tailings storage facilities are now adapting the process to
their specific needs.
Ciba Specialty Chemicals has developed a range of rheology modifying products, which could play an
important role in this type of tailings management process. These products modify the surface properties of
the tailings when added to a slurry at point of discharge. The application known as Ciba® RHEOMAX™
ETD technology has been investigated on a range mineral of ore types at both laboratory and operational
Alcoa World Alumina Australia (Alcoa) currently produces bauxite tailings (referred to as residues), which
are separated into coarse and fine fractions by cyclones. The coarse sand fraction is used for drainage layers,
perimeter embankments, and final capping of the storage areas. The fine mud fraction is stored via a method
of thickened residue disposal called “dry stacking”. This utilises a large diameter super thickener to dewater
the fine residue, producing a high density underflow slurry of around 45 to 50% solids w/w. The thickened
residue slurry is pumped to one of a number of drying beds and deposited in layers of up to 0.5m in depth.
The yield stress of the mud and the slope of the bed are designed to allow for an even distribution of slurry
across the bed.
The fine residue dewaters through a combination of drainage and evaporative drying to a final dry density of
around 70% solids w/w. Alcoa also routinely plough the mud with machinery to speed up the rate of
moisture loss to evaporation and reduce the dusting potential from the drying beds. This process, sometimes
referred to as “mud farming”, is generally done using a swamp dozer or amphirol (Cooling et al., 2002).
This paper provides an overview of testing with Ciba® RHEOMAXTM ETD technology at Alcoa World
Alumina Australia’s Western Australian refineries, and describes how this rheology modifier might be used
to enhance the current storage processes.
Arbuthnot, I.M. and Triglavacanin, R.A. (2005) Designing for paste thickening-testwork and sizing for paste thickeners. Paste 2005,
Jewell, R. and Barrera, S. (eds), Australian Centre for Geomechanics, Perth, pp. 99-116.
Bodley A.J., Cooling D.J. and Nikraz, H.N. (2003) Comparison of the physical properties of treated and untreated residue. Paper
prepared for Environmental Science and Technology, published by the American Chemical Society.
Cooling, D.J., Hay, P. and Guilfoyle, L. (2002) Carbonation of bauxite residue. The 6th International Alumina Quality Workshop,
Crozier, M., Jonhson, J. and Slottee, J.S. (2005) A systematic approach to designing paste thickener projects. Paste 2005, Jewell, R.
and Barrera, S. (eds), Australian Centre for Geomechanics, Perth, pp. 139-146.
Jewell, R.J., Fourie, A.B. and Lord, E.R. (2002) Paste and Thickened Tailings-A Guide, The Australian Centre for Geomechanics,
rheology And thicKening