Large-scale alternative dewatered tailings applications are increasingly being considered in the mining industry in an era of water scarcity and focus on dam structural integrity. However, evaluating business cases for these applications is often ineffective when based on costs alone. Leveraging lessons from the authors’ multi-disciplinary team approach over several years, this paper makes the case for a new, more holistic approach to create effective business cases for evaluating large-scale alternative dewatered tailings applications. Effective business cases not only consider costs but also key drivers including physical and chemical stability, land and water usage, potential environmental impacts, and other sustainability drivers considered over the life of mine, while meeting regulatory requirements. This approach expands the battery limits traditionally used by siloed discipline engineers to examine a wider range of pathways through the tailings management system from dewatering plant to ultimate facility design. The key drivers and trade-offs that have the potential to significantly impact project economics are the focus. To optimise a case and potentially be more cost competitive, the authors propose that the tailings dewatering technology selection follows the filtered tailings storage facility (TSF) design, rather than lead the design. Rather than starting upstream at the dewatering plant and targeting a tailings solids mass concentration, it is more productive to consider the final TSF landform (and geotechnical and chemical stability requirements) and work back upstream to optimise material handling to achieve this constraint. The achievable filtered tailings moisture content or thickened tailings rheology are then determined to meet these downstream requirements. Often a hybrid system of filtered tailings with conventional wet slurry tailings provided the best technical and economic business case when considering proof of concept at scale of current filtration technologies. Benchmarking against large pilot-scale filtration studies and full-scale thin lift deposition operations was useful in identifying potential project risks and opportunities. One of the key drivers used in the proposed holistic approach is the potential water savings. Water recovery from tailings can occur at the tailings dewatering plant and/or at the TSF itself. In all cases, the balance between water recovered from one area versus another must be optimised to minimise capex, opex and operational risks. It is recommended that stakeholders collaborate to evaluate the risks and opportunities in the project planning and design stages using a systems risk-based and multi-criteria decision analysis (MCDA) approach. Using this method, considering identified key drivers, enables the making and documentation of design decisions and the identification of potential opportunities.
Authors
Colleen Crystal | SRK Canada
Roman Jansen | Paterson & Cooke, USA
