Alcoa World Alumina currently utilises a dry stacking process for residue storage at their Western Australia operations. Dry stacking utilises super thickening to dewater the fine tailings. The thickened slurry produced by the super thickener is then spread in layers over the storage areas to dewater by a combination of drainage and evaporative drying, often expedited by mechanical ploughing of the drying layer. This process ensures a well consolidated, stable deposit is achieved.

Ciba Specialty Chemicals’ technology, Ciba® RHEOMAX™ ETD (Enhanced Tailings Disposal) has been investigated as a means of significantly improving the consolidation and drainage characteristics of dilute slurries, which in turn allows direct deposition of unthickened slurries onto the drying beds without detracting from the current drying processes.

This paper provides an overview of;

• Alcoa’s current bauxite residue disposal system
• How Ciba® RHEOMAX™ ETD technology might be integrated into this system
• Results from Ciba® RHEOMAX™ ETD trials on Alcoa residues
• An overall assessment of the potential benefits which might be gained from the use of Ciba® RHEOMAX™ ETD

Reprinted with Permission from www.ciba.com