Management of bauxite residue in a temperate climate using mud-farming techniques

摘要

The management of water within the mining waste industry is one of the most critical factors affecting operators today. Long-term sustainable management will both increase the volume of waste which can be stored in a given area and decrease the effect on sometimes fragile water supplies. One often overlooked technique, primarily used in the alumina refining industry, is the mechanical consolidation and densification of waste bauxite residue (also known as 'red mud' due to its colour) in a process known as mud-farming. This technique provides a simple, less technology-dependent solution as it is carried out by relatively inexpensive mechanical plant. Whilst a number of studies have examined the effectiveness of mud-farming, these studies have been carried out in the comparatively arid climate of South West Australia. Given that this technique may be of interest to the wider mine waste industry, a study into the observed benefits of mud-farming techniques within a temperate climate has been conducted. This study has focused on the mud-farming operations currently carried out at the Rusal Aughinish Alumina facility, near Limerick, Ireland. The study makes use of both historical site investigation data and the results from a site investigation carried out in 2014, using cone penetration testing as well as a complimentary laboratory testing programme. The results of this study demonstrate that the application of mud-farming techniques has led to increases in the both the undrained shear strength and the density of the bauxite residue which will ultimately enable increased capacity at the facility. Furthermore, this study identifies a number of issues arising for the use of standard geotechnical laboratory testing of bauxite residue, including the potential to miscalculate moisture content due to the presence of amorphous particle, and undrained shear strength.