Cyclic Freeze-Thaw to Assist the Dewatering of Oil Sand Tailings

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The mining of bitumen in Canada's oil sands generates large volumes of fluid fine tailings, a waste materialwhich presents significant challenges to de-watering and consolidation. With over 1,250 million cubic metres of tailings inventory as of 2018, finding a holistic and environmentally responsible solution to tailingsmanagement is a top priority for the Canadian mining industry. The proposed study investigates the potential for utilizing the natural winter climate of northern Alberta to assist the separation of water from tailings solids. Under freezing conditions in the field, a one-dimensional temperature gradient moves slowly through theground, and collects moisture into a reticulated network known as an ice lens. Upon spring thaw, the ice lensesmelt and form channels by which water is released. The replication of field conditions at the laboratory bench scale have historically been expensive and time consuming, and generates data slowly.The present study aims to leverage the funds and findings of a preliminary freeze-thaw study into a more complete investigation into tailings de-watering potential using natural climate cycles, and to develop theprocedures to accurately and economically replicate field freezing conditions at the bench scale, with results obtainable in a timely manner. Through the proper emulation of natural winter conditions, the present researchaims to investigate the effect of flocculant and coagulant addition on the depth to, and speed at which,thickened tailings can freeze. Once the methodologies are established and confirmed to be successful, tailings placement strategies to maximize freeze-thaw de-watering benefits will be further investigated.Finally, this project presents an excellent opportunity for the cross-pollination of knowledge and experience between researchers and industry. The procedures developed in this study will benefit future studies inreplicating one-dimensional temperature gradients, and studies on climate-based methods of tailings sediment de-watering.