The equipment selection for a fine coal tailings dewatering application is filled with numerous challenges and complications. There are known technologies operating in the Australian coal industry such as belt press filters and, recently, solid bowl centrifuges. This paper looks at three known technologies, namely belt press filters, plate and frame filters, and solid bowl centrifuges to dewater thickened fine coal tailings. A comparison of recovery, moisture, reagent addition, solids and volumetric throughput is presented. Some pros and cons of each application will also be provided. Specialised technical information on each application including the major factors that have the greatest dewatering impact on the technologies will be highlighted. Information from an installation from South Africa is shared. The paper assists with the selection process and explains important information that must be brought to light when considering a change from wet disposal to dry disposal. Elements of this paper were previously published in Meiring (2021).
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.
To better understand the inline flocculation technique for enhanced water recovery from fine-particle suspensions, this paper studied the impacts of two typical salts, NaCl and CaCl2 on the geotechnical, hydrological, hydromechanical, and chemical behaviour of polymertreated synthetic tailings slurry using a low-shear mixer for continuous flocculation under controlled conditions. The results are discussed in light of the contribution of the polymer treatment to improved rehabilitation outcomes and the role geotechnical, hydromechanical, hydrological and chemical properties play to achieve this goal.
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).
?Several large copper mines are evaluating improvements in the tailings dewatering circuits. Most prevalent alternatives being considered optimize their thickening technologies or the implementation of tailings filtration and stacking. This requirement to optimize water recovery is due to a variety of factors; the deficit and high cost of the water make-up, environmental restrictions, and community relationships. The recent failures in conventional tailing deposit structures and the potential change to reduce the footprint of tailings impounds may also drive the desire to consider alternate technologies. This paper presents technical and economic review of alternate technologies, considering capital investment and operational costs. The five (5) selected alternatives include thickening technologies, pressure filters and a combination with cyclones for classification and filtration of the coarser fraction and thickening of the finer fraction. The selected alternatives are developed and evaluated at trade off study level.
An underground paste fill system will inevitably experience a system flow-loss event during its operational life. In a flow-loss event, the underground reticulation design, flow-control hardware, instrumentation specification and system recovery methods can greatly impact the time taken to safely and effectively achieve a full system clearance and recommence backfilling activities. In addition, the learnings and methods discussed in this paper minimise the opportunity cost of using valuable underground work crew resources to rectify the blocked pipe work and the associated paste plant downtime. This deficit of paste filling will further impact the mining production schedule by increasing mining activity interaction and disrupting the extraction sequence. Direct costs of a blockage may include piping replacement and work crew labour as well as an increased risk of injury and equipment damage during a time-critical activity. The management of a flow-loss event must consider each of the following three flow-loss conditions experienced: A case study (Scenario 1) is presented to demonstrate the management of a flow-loss event, which includes system blockage and stalling due to insufficient available head pressure being overcome by system segmentation. Segmentation highlights the advantages of the ability to carry out safe and effective system isolation from underground in a time-critical situation. Reticulation failure response is also discussed in this paper, with an explanation of the recovery method and the requirement of an adaptive approach as the flow-loss condition can transition from one type to another during the recovery effort.