Open pit surface mining generates process effluents known as tailings. With the continuous accumulation of material in tailings ponds, and to comply with reclamation and water-use regulations, the industry is constantly seeking new technologies that can accelerate the tailings consolidation and dewatering process. Preliminary tools and techniques to screen potential consolidation technologies are valuable to quickly understand the effectiveness of the technology on the bench-scale before larger-scale testing. At present, settling tests have been the ideal medium for bench-scale study, however, this process can be time-intensive. This study compares a potential tool for short-term testing of consolidation, a benchtop filter press, with a standard settling test. The benchtop filter press is commonly used for the generation of specific resistance to filtration (SRF) data, however, the application for use in understanding consolidation is not. In this study, a benchtop filter press was modified to remove the limitation on the dewatering time due to the filter cake cracking, thus allowing dewatering past the liquid limit of the material. Two types of synthetic tailings were developed using a kaolinite and bentonite mix in synthetic process water, with varying solids content, methylene blue indices (MBI) and water chemistries, to mimic the conditions in actual mining samples. The study shows that the modified benchtop filter press results produce similar trends to settling tests and perform as expected with and without polymer addition. The modified benchtop filter press provides data in a course of hours to days, as compared to the settling test data that can take weeks to months to generate. Additionally, work conducted with oil sands fluid fine tailings (FFT) after various treatments, demonstrates that SRF curves from actual mining samples show trends in dewatering time consistent with observed field performance.
The filtering of sandy tailings from the reverse cationic flotation processes and the subsequent stacking of these tailings has shown to be a very strong trend in Brazilian iron ore mining, especially after accidents involving geotechnical structures known as tailings dams, but also due to concern of mining companies to develop a disposal technique that is more complacent with the environment and the surrounding society. In order to develop the sandy tailings filtration project, a fundamental requirement was the correct choice of filtration technology among the many existing ones. For the material object of this study, the filter with vertical discs presented itself as the most productive due to factors such as granulometry, specific surface of the material and the humidity required in the filtration product. Several exploratory and material characterization tests were carried out for this purpose. Disc filters have the principle of operation linked to the difference in atmospheric pressure and the vacuum pressure induced by pumps. The vacuum must act on the filtering screens next to the filter heads and, in order not to drop the yield, the system must be sealed hydraulically. As previously mentioned, there are basically two ways to hydraulic seal the system. The first and most common in Brazilian iron ore filtration is carried out through barometric columns and the other is using filtrate pumps installed directly in the vacuum receiver of the filtration facilities. The decision of which method to use has major implications for the design of the filtering installation and the comparison between the two conditions mentioned is the objective of the present work.
Explore the following case studies for examples of current and past projects undertaken through COSIA
?FLSmidth and Goldcorp partnered to develop the EcoTails® process for mine waste management in 2015. A significant portion of this project was the development of a new, much larger capacity, filter press. A filter press that could filter more tailings at a lower cost and less manpower was needed to make tailings filtration viable for large tonnage open pit mines. The development of this filter press took many years and culminated in a proof of concept filter that operated successfully in the summer of 2019. This paper will examine the need for such a large filter, the drivers for features that are incorporated into the filter, and the results of the successful testing.
The mining industry is becoming more and more attracted to dry stacking as a method of mine tailings management. The development of bigger-sized plates now allows metal producers to utilize pressure filtration technology to process flow rates of up to 200,000 tonnes per day of dry solids, which was undreamed of just a few years ago. The advantages of this technology include very low cake moisture content, significant savings in water usage and the possibility to recover product (when required) without the need of CCD washers. The filter press technology combined with bigger-sized plates enables filters to be installed in remote sites with high average rainfalls, offering the mining company the possibility of a safer and more sustainable environmental impact, thanks to a stable stack of solid material that requires less room than traditional thickened residue dams. The aim of this presentation is to show the latest studies where this technology has been applied.
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.
The most commonly used dewatering technologies for the filtration of tailings from ore processing are pressure filters, filter presses, belt filters and rotary vacuum disc filters. The vacuum disc filter type in around 80% of all applications is the most economical of these technologies in terms of capital and operating cost, especially when modern high performance disc filters are used. The Boozer disc filter is a big diameter high performance vacuum disc filter that has set the pattern in a multitude of applications including the alumina industry and in dewatering coal slurries. In the past decade, this type of disc filter has established itself in applications of tailings dewatering, such as tailings from gold/copper, zinc and gold/silver mines. The reasons for its successful operation in tailings dewatering are: (a) high throughput and dewatering performance, (b) operational reliability even in the case of varying feed conditions, (c) simple and robust design, (d) ease of maintenance, (e) a small footprint. To achieve higher solids throughput rates, or to achieve the lowest possible filter cake moisture, HiBar filtration and HiBar steam pressure filtration offer new solutions in tailings dewatering. HiBar filtration and the HiBar steam pressure filtration are advanced continuous pressure filtration processes realised on rotary disc filters that are installed in a pressure vessel. The application of hyperbaric pressure of up to 6 bar (instead of a vacuum) ensures a high filtration rate and dewatering capability even with filter cakes of fine particles where high cake resistance and capillary forces in the cake must be overcome. With HiBar steam pressure filtration, the use of steam under special conditions improves demoisturing to the furthest extent, leading to the lowest values of moisture content. The drier HiBar filter cake improves the cake handling and disposal with steeper dumping slopes, resulting in reduced disposal area and improved safety of the disposal site.
?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.
Given the increasing scrutiny of the mining industry and its relatively poor record with regards to mine tailings management, increased requirements to minimise water usage (often accompanied by very high costs of water) and the need to demonstrate achievable long-term closure strategies, it is likely that the option of a filtered tailings system will need to be considered in many operations in future. (Australian Centre for Geomechanics 2018). Given such a statement as a conference introduction, it is only appropriate that a range of potential technologies are investigated and compared, to create awareness for even underrated but appropriate technologies. The advantages and disadvantages of all technologies need to be considered and analysed. Suppliers are swift to promote their technologies advantages, however aspects of sustainability are not always fully understood and comprehended. Perhaps a combination of two filtration technologies is appropriate. This paper delves into the technical details, good or bad, of four mechanical dewatering technologies in tailings dewatering and provides insight on an undervalued and, in the authors opinion, young technology the screw press.