Authors: Verdoorn, F; Owens, B; Gibbs, K

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Verdoorn, F, Owens, B & Gibbs, K 2018, 'Case study – SIMEC Mining Big Baron Pit successful tailings dewatering and management using WaterShed polymer', in RJ Jewell & AB Fourie (eds), Proceedings of the 21st International Seminar on Paste and Thickened Tailings, Australian Centre for Geomechanics, Perth, pp. 305-320.

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Abstract:
In 2012, SIMEC Mining commissioned a haematite ore beneficiation plant (OBP) at the Iron Baron mine site in the North Middleback Ranges of South Australia, to upgrade low and medium grade waste dumps. The tailings discharge strategy was to convert existing previously mined pits into in-pit tailings storage facilities (TSF). Geotechnical assessments of the Big Baron Pit identified cracking in the base and walls. However, it was predicted that these cracks would seal within the first three to six months. Hence it was recommended that the pit could be used for in-pit tailings storage. During the first six months of tailings deposition into the Big Baron Pit, there was no evidence of beach formation or solids/liquid separation and about 60% of the TSF volume was lost due to potential seepage and evaporation. The groundwater monitor bores surrounding the pit showed a steep increase in the rate of rise which was a concern. The potential environmental impacts of the rising groundwater levels on native vegetation was unacceptable and the inability to recover any water from the tailings for reuse in the plant became a serious threat to sustainability of the operations. This necessitated an option investigation study to identify a technology to assist in rapid solids/water separation and subsequent sealing of the base of the pit. A conceptual design for a polymer tailings dewatering application was developed in collaboration with Nalco Water; dosing commenced in March 2013. Within the first two days clear water was present at the decants and the dewatered solids started to form a well-defined beach. Water extraction from the decant started within the first week, indicating the cracks were sealing as the solids settled and compacted. Survey data also indicated that the volume of the solids in the TSF started to increase accordingly. The reclaimed water from the decant was initially used for dust suppression until quality monitoring determined it was suitable for chemical make-up and use in the plant. During the first year of application, an average of 63% of the water entrapped in the tailings was recovered back into the plant. This reclaimed water is a direct replacement for purchased South Australian government water, thus saving on fresh water, which cost approximately AUD 3.50/m3 at that stage. Due to the success of the Big Baron Pit application, the Nalco WaterShed program has been extended to other applications throughout SIMEC Mining Operations including our large above ground TSF at Iron Duke. All applications have provided excellent results with water recovery, solids consolidation and increased storage capacity. Knowledge gained from the use of this technology has greatly assisted SIMEC Mining with its onsite water and fine tailings management and process efficiency improvements. Nalco WaterShed technology has played an integral part in the conversion of the above-ground TSF at Iron Duke from dual point discharge to a perimeter discharged central decant (PDCD) design, thus allowing to resolve groundwater management and construction issues and ultimately ensure operational security. Keywords: WaterShed, polymer, tailings management, water recovery

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References:
Bennett, M 2011, Tailings Management – Tailings Thickener Underflow Dewatering, Nalco Water, Whyalla.
Johns, B, Travers, D, Butler, B & Hobart, C 2012, Nalco Internal Service Report – Tailings Dewatering, Nalco Water, Whyalla.
Owens, B 2013, Dewatering of Tailings, Iron Baron, final year project, Bachelor of Engineering (Metallurgy), University of South Australia, Adelaide.




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