This bulletin provides a framework for classifying different types of tailings based on their geotechnical properties and provides typical geotechnical parameters for the different tailings types. It also presents technologies for dewatering tailings from thickening to filtration.
Explore the following case studies for examples of current and past projects undertaken through COSIA
Filtered tailings dry stack disposal often requires low cake residual moistures to meet the stacking specifications defined by geotechnical studies. Low residual moisture targets and increasing throughputs require careful definition of filter press process parameters in order to prevent unnecessary extra capital and operating costs. Because of this, alongside the testing phase, a comprehensive characterisation of the material, not limited to standard geotechnical tests, becomes important. Standard physical/chemical characterisation of mining slurries includes both basic (liquor, solid and slurry density, solid concentration, solid specific gravity) and thorough analysis (yield stress, particle size distribution, elements and mineral phase detection). Each of these requires different techniques. Phyllosilicates (i.e. clays) are one of the most common components of mine tailings, together with quartz, feldspar and other aluminosilicates. Clay type and relative content can have a drastic influence on the filtration process and furthermore on filter design. A detailed analysis of clayey phases can give useful information about the filterability of a slurry and, therefore, on the expected filter performance and its variability. A comprehensive study about clay detection and quantification and correlation with dewatering properties is presented here. It involves different analytical techniques (powder X-ray diffraction, Rietveld refinement, qualitative evaluation) and correlation studies based on the lab testing campaigns database. The results show how the filterability can be strongly affected by the phyllosilicate type and small variations in their content, to yield completely different cake properties, showing that smectite group clays have the greatest influence on filterability. The impact of these characteristics on filter sizing, especially for large equipment (like the GHT5000F filter press) and related ancillaries will be discussed.
One of the methods that has been studied for the disposal of tailings by the mining industry is dry stacking. Several studies have indicated that the use of filtered tailings is feasible under certain technical and operational conditions. The requirements for deposition, and characterisation of the tailings properties, must be obtained through a wide range of field and laboratory tests. These parameters are key to determining the behaviour of the material during the dewatering process, the optimum moisture content and the maximum density of the tailing cake, as well as the physical and environmental stability of the projected geotechnical structure. The operational aspects related to the handling of the material are also vital to determine the placement of the filtered tailings on the facility. In addition, the advantages with respect to water consumption, reduced and/or flexible stack footprints and geometries, seepage control requirements, closure/reclamation costs and public perception of risk can result in dry stacking being selected as an economically beneficial alternative, particularly if life-of-mine risks and costs are appropriately considered. As with any conventional tailings management approach, careful and diligent planning, engineering and operational controls, quality assurance/quality control (QA/QC), instrumentation and monitoring are required to manage risks and uncertainties. This paper presents the criteria that need to be evaluated in the evaluation of filtered tailings as a business case, based on the experience of the authors developing such projects within the minerals industry.
This document provides procedures and guidance for best practices concerning embankment dam flter design and construction and represents an effort to collect and disseminate current information and experience having a technical consensus. This document is intended for use by personnel familiar with embankment dams, such as designers, inspectors, construction oversight personnel, and dam safety engineers.
?This study aims to analyses the use of high-pressure filter presses in the dewatering of slurry resulting from mineral processing, especially iron ore mining tailings and slimes. The current practice problems of deposition of fines in tailing dams were analyzed, as well as the new challenges faced by the sector in relation to water scarcity and energy efficiency. Are listed technological differentials implemented in Matec filter presses and analyzed the benefits in application of this technology, such as higher water recovery, reduce of environmental impacts and reduce of operating costs for handling and disposal of waste. Lastly, we analyze the filtration tests performed on iron ore tailings and slimes and a case study.
The metallurgical testwork for a new gold project indicated acceptable settling rates and filtration rates. The equipment was sized, and the plant constructed. Subsequently, commissioning of the thickening and filtration for dry stacking of tailings indicated serious deficiencies with the design and a much lower achievable throughput. The throughput was some 30% of design and cash flow considerations were that the project throughput was restricted by poor performance of the thickeners and tailings filtration acting as a bottleneck. Mineral Engineering Technical Services Pty Ltd was commissioned with the task of increasing filtration throughput and removing the bottleneck. For the thickeners, new flocculants were evaluated, changes to the flocculant dilution were made, and thickener underflow pump speeds were increased. An additional filter feed storage tank was installed to allow for short-term filter shutdowns. With the two belt filters, various flocculants, guar and diatomaceous earth were evaluated. Also, more permeable filter cloths were evaluated in order to increase filtration rates. The single biggest improvement achieved was with the use of coagulants. This paper describes how the task was managed and what steps were taken to achieve design throughput.
High availability of filtration equipment is essential for reducing the capital cost on tailings filtration projects. At the same time, low operational costs are needed to maintain mine profitability. High availability, greater than 90%, and low operational costs can be achieved at the same time through good equipment design, good building layout, automation, and proper maintenance procedures.
The objective during TSF beach development is to still maintain a slurry that is pumpable and self-distributing at the tailings storage facility (TSF), rather than having to rely on trucks or on conveyors and stacking systems to manage a cake, but one that will deposit at a steeper beach slope than can be achieved by thickening alone. The use of ultra paste has the potential to broaden the range of topographic conditions that will suit thickened tailings discharge. This paper presents a case study for a large copper mine in which underflow from a series of paste thickeners with a nominal tonnage of 3,660 tph at 59% solids concentration would be mixed with 1,363 tph of filter cake at 80% solids concentration. The combined tailings (ultra paste) would be discharged equally into two open channels (flumes) at the combined solids concentration of 63.5%. The ultimate goal of adopting an ultra paste scheme is to produce homogenous consistency tailings, hence proper mixing of the paste and filter cake has to occur. In this study based on a series of tests, the mixing requirement has been assessed. The study also covers a conceptual investigation of natural turbulent mixing (NTM) of the filtered tailings with paste thickened tailings and issues associated with the deposition of the combined tailings, the ultra paste, into the existing TSF. In the conclusion, the study indicates that NTM can possibly occur only for the case in which the total tailings are discharged into one channel, which is not practical due to limitations with regards to tailings management. Hence, mechanical mixing has been recommended in this case.
Paste thickening represents a proven and effective method for the safe disposal of tailings and maximises water recovery. The optimum density for disposal is often at the limits of that achievable in commercially available thickeners. This paper looks at the options available to increase paste density to meet the disposal requirements and to stabilise paste properties through blending filtered tailings with thickened tailings, supported by experimental data and case studies.