Planning, operating, monitoring and closing a tailings storage facility (TSF) can present many challenges, especially in dynamic mining environments where site conditions vary spatially and with time. However, big impacts can be made at relatively small cost once the tailings management system, design and performance are well defined and understood. This paper presents various examples of initiatives aimed at achieving the design intent that have been adopted by Rio Tinto Iron Ore, which also reduce risks and improve tailings management performance. Examples presented include development and communication of short-term, long-term and life-of-facility deposition plans, implementation of simple deposition management tools, monitoring and managing slurry density, development and continual oversight of water balance models, and sound investment in water management infrastructure extending to safe performance in emergency situations. Regular governance was also implemented to provide assurance that these controls remain effective.
This bulletin describes various methods of tailings transport (slurries vs. dry tailings), tailings placement (cyclone, spigot, paddock, mechanical placement), and decant systems. The bulletin is intended to provide advice for design of these elements based on project-specific characteristics. The bulletin also provides guidance for assessing the water balance of a tailings impoundment.
?Luossavaara-Kiirunavaara AB (LKAB), an iron ore company with mines in northern Sweden is continuously considering new technologies for handling, transportation and disposal of waste rock and tailings. The mines and concentration facilities are located north of the Arctic Circle which in Scandinavia means an average temperature of about 0° C. Snow from mid-October to mid-May. In winter the temperature may reach -35 to -40° C during weeklong cold spells. At the Svappavaara mine early technical-economical feasibility considerations together with expected space limitations in the concentrator area favored location of two thickened tailings thickeners on a hill close to the disposal area about 1600 m away from the concentrating plant. In this way only short distance pumping of thickened slurry is required and warm process water is recovered directly by gravity from the thickener to the concentrating plant. A thickener of a high-density type with 18 m diameter was first installed. Four years later an additional thickener of paste type with diameter 24 m was put into operation. The design (maximum) capacities were 115 and 275 tph (tons per hour) for the 18 m and 24 m thickeners, respectively, with solids flux rates of 0.45 and 0.6 ton/m2h. Both are planned for common use for 390 tph within a few years. The tailings product is characterized by an average particle size of about 30 µm with a maximum of about 500 µm and about 40 % passing 20 µm. Solids density about 3000 kg/m3. A solids concentration by mass of 70 % was considered sufficient for deposition at a slope of up to 3 %. The objective is to present and discuss the performance of the thickening, transportation and deposition systems during the commission stages and first years of operation. The aim is also to describe how initial conditions related to changes in the tailings production rate together with climatic conditions called for robust by-pass arrangements. Furthermore, complicating factors related to the choice of auxiliary equipment and instrumentation for central functions are discussed.
In 2012, SIMEC Mining commenced a detailed investigation into changing the way the magnetite tailings storage facility (Mag TSF) operates at the South Middleback Ranges (SMR) to increase water recovery and provide a sustainable cost-base for tailings management. Changes were also necessary to support the Magnetite Expansion Project (MEP) that was destined to be commissioned in October 2013. A feasibility study was performed with Golder Associates to understand the technical and commercial influences and provide a capital estimate for several options. The selected option from the study was a redesign of the current dual discharge TSF to a perimeter discharge, central decant (PDCD) design. Application of Nalco WaterShed polymer at the Big Baron Pit (Verdoornet al. 2018) revealed the technology would greatly assist in the successful conversion of the TSF to a PDCD configuration. Expectation was high that WaterShed polymer treatment would allow greater beach angle control, improved water recovery, and a reduction in surface water pooling across the TSF with water pooling concentrated around the central decant allowing for efficient removal prior to loss via evaporation or seepage. A conceptual design for the polymer tailings dewatering application was developed in collaboration with Nalco Water and dosing commenced in October 2013. Due to unknown risks associated with dewatering magnetite tailings, the project was split into two stages, namely, phase 1: a proof of concept trial to establish the applicability of Watershed on the magnetite tailings prior to commissioning of MEP; and phase 2: fully operationalise the PDCD configuration. Golder was engaged to develop a life-of-mine plan for the TSF at SMR that could be safely operated to a planned final height of RL 199 m. Throughout 2013 and 2014, design and construction occurred to convert the Mag TSF to a PDCD facility. A master plan was developed to manage tailings storage for five years from March 2014, referred to as the First 5 Year Plan. This involved six wall raises that would eventually fill the three voids near the western embankment and bring the height of the TSF to RL 172 m. The civil concept selected was based on an alternatives assessment that presented three options. SIMEC Mining chose the lowest cost approach of filling the voids with WaterShed polymer treated tailings to provide a base for 3 m wall raises upstream. Strict deposition and water recovery models were followed to ensure sufficient dewatering and the subsequent drying of the tailings layers. There was also extensive test work completed prior to each of the individual embankment raises to ensure that the dewatered tailings had the appropriate density and strength properties to support the raises before commencing with the lifts. During the first five years of operation, water recovery was around 60% and the volume utilisation was in line with the deposition model. The high percentage of water recovered enabled the processing plant to reach its new design capability, reduce significant downtime due to water availability and provide the mining operations with sufficient water for dust suppression. The second five-year plan is currently being finalised and progress is consistent with the tailings deposition and the dewatering model.
?There has been an increasing move towards high-density thickened tailings systems over the last decade, mainly driven by the need to save water, meet environmental regulations and project specific demands. A typical tailings distribution system on a Tailings Storage Facility (TSF) consists of a main pipe with multiple discharges operating simultaneously, to distribute the slurry across an extended length over a specific area of the TSF at a time. A potential limitation of these systems is an uneven distribution of slurry flow rate and solids concentration between multiple spigot discharges, where an inadequate design can lead to laminar pipeline flow conditions resulting in particle segregation, and an increased risk of pipeline blockage. An operation with unbalanced flow rates could result in an uneven distribution of solids that could impact the formation of beach slopes and/or cause difficulties for the dam construction. Paterson & Cooke (P&C) has previously developed several thickened tailings distributed systems, where the discharge points are located on a distribution pipeline which branch off a main pipeline. This previous experience has allowed P&C to develop a methodology for the hydraulic modelling and implementation of these types of systems. This paper presents the methodology for distribution system deposition design review and its implementation of a TSF located in Southern Europe.
The Tronox KZN Sands Fairbreeze Mine is located in Zululand, south of Mtunzini on the east coast of South Africa. Mining activities commenced in 2015 and the declared life of the mine is 15 years. Fairbreeze Mine is beneficiating an orebody that is part of the Berea Red dune system and the fines content is known to approach 30% in some areas of the deposit. The definition of fines in the mineral sands industry is classified as any particle passing 75 µm and consists predominantly of clays and some traces of silica particles of silt size. Historically, the mining industry has made use of sub-aerial deposition to dewater fines that do not drain freely. The only tools available to the processing facilities using the sub-aerial deposition dewatering method, has been: In order to minimise the risk and to reduce the sterilisation of large tracts of land, mining companies are being forced to consider alternative dewatering techniques. The use of amphibious vehicles, or mud-crawlers, is a well-documented alternative in the alumina industry but little is known about the performance of amphibious scrollers on mineral sands fines residue. This paper investigates the effects of mechanical scrolling performed by mud-crawlers on the dewatering and the ultimate final dry density of Fairbreeze fines. The investigation looks at ways that mud-crawlers can be applied as a financially viable alternative to sub-aerial deposition.
The objective of this report is intended to be a technology deployment roadmap for "end to end" solutions for oil sands tailings. This technology deployment roadmap and action plan that will assist regulators and industry to create and implement technology solutions that will meet the goals of Alberta Environment (AEW) Directive 047. The report is broken into 4 components that includes a review of current technologies used in the oil sands industry, evaluation of these technologies, and highlights technologies to improve upon existing methods.
Results of Component 1 of the Oil Sands Tailings Technology Deployment Roadmap. This report gathered available information on oil sands tailings, summarized the current state of knowledge and practice, and identified and described tailings management technologies used in the oil sands and around the world. Component 1 identified 101 unique technologies, broken into 8 main tailings schemes and categorized as pre-commercial or in commercial use.
Component 3 of the Oil Sands Tailings Technology Deployment Roadmap. This report intended to develop a method to evaluate the identified tailings technologies to determine their strengths and weaknesses, in light of specific criteria provided by Component 2, and then to evaluate the technologies using the developed methodology. Eight categories of technologies (mining, extraction and bitumen recovery, tailings processing, deposition and capping, water treatment, reclamation, and technology suites) were sub-divided into three categories (commercial, development, and research).
Copmonent 4 of the Oild Sands Tailings Technology Deployment Roadmap. This report intends to identify technologies and/or suites of technologies which could improve the ability of tailings management practices to meet the previously defined goals, and the pathways by which they could be brought through the research and development process to commercial implementation.