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Murray Zircon Pty Ltd operates the Mindarie Mineral Sands Project in South Australia comprising a mine and concentrator plant. The program for environmental protection and rehabilitation (PEPR) approved by the South Australia Department of Manufacturing, Innovation, Trade, Resources and Energy (DMITRE) requires diligent management of the tailings deposition and overall mine rehabilitation processes.
The mining licence was granted based on a maximum permitted operational footprint of the open area of the mine. Mining at Mindarie follows the ‘moving-hole’ concept whereby topsoil and overburden is removed, ore is mined, tailings are deposited in the mined-out space and are then capped by overburden. The moving hole must advance at approximately 10 m per day. Consequently, it is imperative that dewatering, consolidation and stabilisation of deposited tailings happens quickly.
Tailings are treated using a high molecular weight polymer which rapidly releases clean water for reuse in the concentrator plant. The polymer binds the coarse and fine particles together to create a
non-segregating deposit and accelerates the consolidation rate.
Polymer dosing regimes for the tailings have historically relied on a visual interpretation of the material entering the tailings cells to determine the optimum dose; however, it is the consolidation rate and associated strength gain that determines when overburden replacement can begin. To provide an improved assessment of the impacts of dosage on consolidation, geotechnical testing was undertaken on material treated with different polymer levels.
A recent development for the Mindarie mine is to adjust the natural acidic pH of tailings to a slightly alkaline level using lime. This was done in order to overcome a throughput bottleneck in the slimes thickener and reduce polymer dosing levels in the slimes thickener and tailings applications. The impact of lime addition on polymer dosing, together with the effect of lime on tailings consolidation properties is also investigated.
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Jeeravipoolvarn, S, Scott, JD & Chalaturnyk, RJ 2010, ‘Composite tailings made from in-line thickened oil sands tailings’, Proceedings of the 2nd International Oil Sands Conference, pp. 337-347.
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