?Mining using backfill methods has been utilized by many mines around the world. Tailings thickening, one of the ways to prepare backfill materials, has been studied worldwide and components of the process such as the thickening mechanism of the tailings tank and principles of selecting flocculants have already been worked out. The studies of hindered settling properties of tailings during this process have lagged which can restrict the precise control of tailings thickening and affect the backfill result. Using in-situ tailings from a mine, hindered and polydisperse settling experiments of tailing slurries with different concentrations and different particle size distributions have been launched to study and analyze the hindered settling features of tailing particles. The experimental results show that the R-square figure of the hindered settling rates of classified tailings between calculated values based on Richardson-Zaki model and experimental ones is over 0.87 proving the Richardson-Zaki model can be used to calculate and predict the hindered settling rates of classified tailings. Moreover, Selims theory can capture the main properties of the polydisperse settling process of the mix of sieved and silica tailings. The self-flocculation of fine particles in silica tailings has increased the hindering effect among particles, the experimental settling rates of silica tailings are less than those theoretical values calculated by Selim theory.
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.
?As is well known, the availability of water for mining processes in Chile is limited. In addition, it should be considered that the vast majority of mining plants are located in the northern part of the country, which is for the most part desert, and mainly at a high altitude. Given the low availability of water, various alternatives have emerged such as thickening tailings to high concentrations by weight (recovering more water in the thickeners) or using desalinated seawater. The present study aims to define the optimum thickening concentration for copper tailings, applied to a case study of representative Chilean mine tailings, from a rheological and energy point of view, as a function of recovered water in the thickeners and specific energy consumption (SEC), transporting one ton of Non-Newtonian thickened tailings. The specific energy consumption (SEC) should be related mostly to the solids transported than to the mixture, with thickening becoming a relevant parameter, since in slurry transport, the solids are usually the "payload", while the conveying fluid is simply the "vehicle". The result of this paper provides the industry with an additional variable to consider in the optimum grade of tailings thickening and rheological design parameters for projects, which could be considered in conceptual and pre-feasibility stages or in the optimization of existing systems.
Globally there is an upward trend by mining operations to opt for tailings dewatering technologies to reduce water consumption, minimise surface disturbance (footprint), increase the stability of tailings deposits and, overall, to operate sustainably. The properties of the mine tailings are largely dictated by the type of ore and the process necessary to liberate the metal values. In other words, it depends on the beneficiation process and the mineralogy of the gangue. Due to the importance of selecting the correct strategy for the management of mine tailings, designing a disposal strategy based solely on the requirements of ore processing may overlook opportunities to maximise the viability of the mining operation, especially when dewatering technologies are being considered. As an example, accepting a coarser grind may reduce overall metal recovery; however, the loss in revenue may be offset by improved dewatering performance and lower capital and operating cost to manage the tailings. Therefore, the design of the ore beneficiation process should consider the requirements for tailings disposal, specifically tailings dewatering and storage facility design, in order to obtain more efficient and sustainable mining operations. This paper will discuss the effects of mineralogical composition and particle size distribution of gold and copper tailings on rheological properties, which provides an indication of what can be achieved in thickener underflows. The present paper is based on laboratory tests performed by Golder Associates on mine projects around the globe.
Portions of this paper were originally published in A strategy for improving water recovery in kimberlitic diamond mines as it appeared in the February 2019 Edition of the SAIMM Journal, Volume 119 published by The Southern African Institute of Mining and Metallurgy. Mine site location and the sources from which raw water is drawn are fixed by geology, geography and climate. The colloidal behaviour of the tailings is therefore randomly determined by the tailings mineralogy and the chemical characteristics of the process water circuit. In some fortunate cases, the tailings slurries are non-dispersive and solid/liquid separation, either by gravity thickening or filtration, is easily achieved at low capital and operating cost. In less fortunate cases the tailings are highly dispersive and solid/liquid separation is achieved only at high capital and operating cost. This paper presents a strategy by which difficult-to-treat slurries can be modified by conditioning the process water circuit with a process water conditioner (ClariVie44®) so that gravity thickening and filtration can be enhanced.
A decade ago, paste and thickened tailings (P&TT) disposal was regarded as a potential technology for eliminating so-called wet tailings dams. Despite numerous very successful examples of both surface and backfill applications, by 2015, confidence in the technology had waned after the technical difficulties encountered at two high-profile, large tonnage copper tailings projects in South America. The recent spate of deadly tailings dam disasters has refocused public and private sector attention on conventional tailings disposal. The knee-jerk reaction from the mining industry has been to ignore P&TT and focus on dry stacking as the solution to the problem, which itself is still a relatively immature technology for large tonnages. This paper attempts to explain the apparent lack of recognition that P&TT as a legitimate and safe tailings disposal method has received. A chronological review of P&TT technology implementation and possible reasons for its loss of favour, particularly in large tonnage applications, is provided.
This paper presents a numerical and experimental investigation of an innovation in thickener feedwell technology. A feedwell plays a leading role in the robust operation of a thickener. Its multifunctional duties include slurry feed momentum dissipation, solids and liquor mass fraction preparation, flocculation, and symmetrical aggregate delivery to the tank. The testing of new concepts in the pursuit of developing a next generation feedwell presented an opportunity to create an improvement in process performance. An alternative method of using a feedwell trough, populated by a multitude of vertically directed nozzles, is adopted. These deliver slurry into a flocculation chamber before dispersing through an exit gap into the thickener tank. The trough most innovatively ensures flash mixing, and highly uniform solids dispersion inside the aggregate growth chamber. Initial examination adopted a multiphase Eulerian mathematical model to explore geometric configurations under various process scenarios. Numerical modelling indicated that when quantitatively compared to an equivalently sized diluting Vane Feedwell TM the design provides a large improvement in solids hold-up, mixing, exit distribution, and more. Modelling advanced to onsite testing of a non-diluting small 2 m diameter prototype in an industrial mineral processing plant. The retrofitted feed system improved thickener performance when compared to the preexisting feedwell and at a newly higher throughput duty. The first occurrence of a networked bed was observed, underflow densities improved by 6.5% w/w, flocculant consumption reduced by 5%, and overflow clarity largely improved. Underpinned by this positive result, modelling has shown even greater benefits may be found in application of the new technology to self-diluting feedwells.