Conference Agenda

Effective management of runoff water on a tailings storage facility is essential to prevent water infiltration into the ground and avoid any environmental impact. For nearly 130 years, the Gardanne alumina refinery operated a bauxite residue disposal area named Mange Garri, which is now a closed site. Initially designed to accommodate red mud, using the lagooning method, the site was subsequently converted into storage of dehydrated residue from 2006, following the commissioning of press-filter technology. Although a drainage system is present at the base of the storage facility allowing the collection of seepage, the change in the site's operating mode has made it possible to improve water management on the site, by significantly reducing the volume of water infiltrated. Extensive earthworks on the storage areas, combined with the construction of several spillways, enabled all run-off water to be channelled into a single collection pond. An ambitious and innovative project then made it possible to seal this pond, thus preventing water infiltration into the ground.

Aluminum oxide extraction from bauxite generates over 3000 tons of filtered bauxite residue daily at Rio Tinto’s Vaudreuil Plant. Managing these mine tailings includes addressing the risks of fugitive dust scattering from their surface while they are momentarily stored in the open without dust suppressant at the disposal site in Jonquière, Quebec. To mitigate the risks, continuous monitoring of the drying process is imperative. A real-time quantification of their surface moisture content (SMC) is necessary to predict and prevent fugitive dust scattering, thereby reducing managing and mitigating costs. Albedo measurements in the near infrared (λ = 1200–1550 nm) will be shown to be a precise, sensitive and selective optical method for characterizing the mine tailings’ SMC and monitoring their drying rate. A portable device has been designed for continuous SMC measurement, with high temporal and spatial resolution allowing their drying rate to be monitored in situ and in real time, under adverse environmental and operational conditions. This device also facilitates laboratory investigations into the dependencies of the mine tailings’ drying rates on ambient air temperature and relative humidity, revealing how atmospheric boundary conditions influence water transport mechanisms within their interconnected porous network, namely capillary pumping and gaseous diffusion. The drying rates accelerate with increasing temperatures and decreasing relative humidity, while surface drying is more rapid in frozen tailings because capillary pumping is significantly inhibited. A comprehensive and quantitative knowledge of the impact of these key parameters, along with that of meteorological conditions such as wind speed and solar irradiance, and their recent history, should improve our description of water transport mechanisms and kinetics within mine tailing. The quantification of their drying rates should also improve our prediction of the evolution of their SMC and promote the development and implementation of models and tools necessary for the forecasting and prevention of fugitive dust scattering events thereby contributing to the reduction of the environmental impact of the mine tailings disposal site.

In November 2019, Vaudreuil commissioned its bauxite residue filtration plant (BRFP), to treat thickened bauxite residue using four (4) filter presses. Each filter press is capable of holding 0.25 m3 of material per filtration chamber. These chambers are assembled by joining two plates covered with filter cloths and two pairs of distribution rings. The bauxite residue slurry enters the chambers with high velocity causing significant stresses on all filter components due to the combined high density and abrasive properties of the slurry. This leads to short- and long-term components failures. The main issue is the excessive wear and increased maintenance costs related to the frequent replacement of filter cloths and distribution rings. This paper provides an overview of the potential of modern numerical methods like computational fluid dynamics (CFD) in helping to determine fluid velocity and more importantly flow patterns inside the chambers. CFD coupled with finite element analysis (FEA) to assess the structural integrity of the distribution rings and plates, valuable insights can be gained for geometric adjustments to reduce filter cloths wear, extend their life cycle and improve the overall performance of the filter presses. As a result, reliability of the BRFP can be enhanced.

Red Mud is a waste product from the aluminum production process. Due to its high sodium and high iron oxide content, it is difficult to use unprocessed bauxite residue in the steel industry as a substitute for iron ore. Therefore, a common way until now is to deposit the untreated red mud in various places, although this represents a significant risk to the environment because of potential pollution of surrounding soil and groundwater (e.g. the sodium content). Due to a poor exploitation of this resource, the industry faces here more and more important market challenges, since the volume of red mud is constantly increasing and the places for landfilling or deposition are reaching their limits. Among other things, the players also suffer from the high landfill costs. To relieve the landfills (reduce volume) and enable dry stacking, the use of filters prior to deposition is more and more adopted. Therefore, to protect the process pumps and filter cloths against wear, the coarse sand particles might be separated by special hydrocyclones before filtration step. To receive valuable fractions from the red mud, the desanding and recovery technology from AKW Equipment + Process Design is used. For the challenging conditions of red mud desanding and classification, special designed hydrocyclones AKA-VORTEX, in wear and temperature resistant Polyurethane or cast steel lining, followed by a washing/dewatering screen unit or also combined with a teeter bed separator AKA-SIZER, would be the effective solution. An introduction of the installation and operation of such highly specialized desanding unit will be presented in this paper.

Building on previous discussions of mineral resources governance as it relates to bauxite residue disposal areas (BRDA’s) in Jamaica, re-examining the structure of environmental management in Jamaica is useful to map the ways in which risk assessments are being internalized into the process. Additionally, a review of the environmental indicators relating to environmental risk minimization is considered in the context of the national policies for development and the evolving metrics for environmental governance (for example, water quality impacts, closure planning oversight and community warning systems). The clear advantages of risk minimization through bauxite residue removal for reuse and recovery of constituents will be globally reviewed, however, environmental efficiency costs have to be considered, especially for closed and legacy sites in a small island developing state like Jamaica.