Grant: CCI Applied Research and Development Grants

The treatment and remediation of mine tailings waste to create geotechnically stable deposits are an area of global ecological concern, especially as increased demand for mined metals and minerals produces ever-increasing volumes of tailings. Observations by Suncor Energy into evaporative drying and freeze-thaw methods for fluid fine tailings (FFT) have demonstrated that seasonal freeze-thaw cycles can potentially be leveraged to remove water from and stabilize tailings. This technique is particularly promising in Alberta’s Athabasca region, which experiences sub-zero temperatures for 5-7 months each year. In oil sands FFT, microscopic clay particles remain in stable suspension in water, making separation without intervention impossible within reclamation timelines. As tailings freeze, ice pressure encourages the migration of water from the bulk medium into an ice network, which in turn forms a drainage pathway upon thaw and provides a cost-effective and environmentally sustainable method to remove water from tailings slurries. While the benefits from freeze-thaw dewatering have been observed in the field, the complex interaction between tailings type, chemical treatments applied to tailings, and deposit sequencing have made field-level observations difficult to reconcile into engineering guidance that could be used to more effectively derive benefit from this natural dewatering technology. NAIT has previously partnered with Suncor Energy in a Phase I study, which developed a method to replicate field-scale freezing effects at the bench scale. This proposed Phase II research builds upon the previous work to study how freeze-thaw effects can be incorporated into tailings planning. Objectives include determining how chemical treatment by coagulant and flocculant addition, and tailings type, can influence the flow of heat through tailings, their freezing behavior, and their dewatering and strength response. Coupled with numerical modeling, this will ultimately lead to recommendations for deposition strategies to optimize freeze-thaw dewatering. Research results will be directly relevant to tailings planning for Suncor and other Canadian oil sands operators utilizing atmospheric dewatering for tailings. By addressing gaps in understanding freeze-thaw effects, this research aims to provide guidance for cost-effective and energy-efficient tailings treatment methods that conform to environmental protection guidelines.