Conventional Tailings Research Articles

Study on strength characteristics and thickening characteristics of classified-fine cemented backfill in gold mine

For some new mines, the utilization rate of tailings is not satisfactory when using unclassified tailings as backfill aggregate for cemented backfill. At the same time, with the progress of mineral processing technology, the tailings discharged by the concentrator gradually become finer. Therefore, cemented filling with fine-grained tailings as aggregate will become the development direction of filling technology in the future. In this paper, the feasibility of fine particle tailings backfill is studied by taking the particle tailings of-200 mesh as aggregate in Shaling gold mine. The calculation shows that the utilization rate of tailings is increased from 45.1% to 90.3% by using-200 mesh tailings as filling aggregate. The response surface central composite design method (RSM-CCD) was used to study the strength of backfill with alkali-activated cementitious material as binder by taking the mass concentration of backfill slurry and sand-binder ratio as input factors. The results show that the 28-day strength of the backfill with graded fine-grained tailings as filling aggregate can reach 5.41 MPa when the sand-binder ratio is 4, which can fully meet the needs of the mine for the strength of the backfill. The thickening test of-200 mesh fine particle tailings was carried out by static limit concentration test and dynamic thickening test. In the case of adding 35 g/t BASF 6920 non-ionic flocculant, the concentration of 64.74% tail mortar can reach 67.71% after 2 h of static thickening, and the concentration can reach 69.62% after 2 h of static thickening. The feeding speed of thickener should be controlled between 0.4 and 0.59 t/(m2 h). In this case, the underflow concentration of thickener is relatively high, which is 64.92–65.78%, and the solid content of overflow water is less than 164 ppm. The conventional full tailings thickening process was improved by using the design of high-efficiency deep cone thickener and vertical sand silo. The feasibility of fine-grained tailings as filling aggregate was demonstrated by combining the filling ratio test of fine-grained tailings, the data of thickening test and the improved thickening process. The research results can provide reference for other mines to use fine-grained tailings as filling aggregate to design filling system.

Comparative Life Cycle Assessment of Conventional and Dry Stack Tailings Disposal Schemes: A Case Study in Northern China

Alternative tailings disposal technologies can be effective solutions to mining waste safety and environmental problems. The current decision-making processes for tailings disposal schemes lack consideration of environmental impacts. Based on a case study of an open-pit iron mine in northern China, this study adopted the life cycle assessment (LCA) method to compare the environmental impacts of three tailings disposal schemes of conventional slurry disposal technology (CSDT), dry stack disposal technology (DSDT) by belt conveyance and DSDT by truck transport. The results indicated that (1) the environmental impacts of the CSDT scheme were lowest under the premise that water consumption was ignored; (2) the environmental impacts of the DSDT scheme by belt conveyance mainly originated from its transport process, indicating that the tailings storage facilities (TSFs) site planning could be crucial in design decision making; (3) the environmental impacts of the DSDT scheme by truck transport mainly originated from the energy consumption of dry stacking equipment; and (4) the DSDT scheme by truck transport was eventually found to be preferable and implemented in the case study, after comprehensively considering the LCA results, TSF safety and remaining capacity, and social and policy uncertainties. It is therefore recommended to conduct LCA of environmental impacts in the decision-making process for the sustainable design of TSFs.

Seismic Stability and Liquefaction Analysis of Tailings Slope

The potential for liquefaction and slope stability of a thickened tailings slope, within a storage facility located on the shore of a natural glacial lake in Tehran, is evaluated based on field and laboratory testing. The tailings slope has the particularities of being located in a high seismicity area and founded on conventional slurry tailings from the previous operation of the facility. The in-situ state of the thickened tailings was investigated through field tests, including Standard Penetration Tests (SPT) and Cone Penetration Tests with pore pressure measurement (CPTu). Samples collected during the field investigation were used in an extensive geotechnical laboratory program to determine index properties and strength parameters for the thickened tailings. Testing included a series of isotropically consolidated undrained and drained (CIU and CID) triaxial tests, as well as a simulation of the consolidation process within the tailings through oedometer tests. The liquefaction potential was evaluated using the data from the CPTu testing, while slope stability was assessed using the limit equilibrium approach for an infinite slope, considering the variation of shear strength with the degree of consolidation (void ratio) of the tailings from a critical state approach. Based on the results of the liquefaction potential and the slope stability assessment, a design approach is suggested for facilities under similar conditions.

Assessment of the Self-Compaction Effect in Filtered Tailings Disposal under Unsaturated Condition

Filtered tailing is a relatively-environmentally friendly technique due to the recovery of water during the process of dehydration. This technique was recently developed and therefore there are few studies available compared to research on conventional tailings. This work focuses on the behaviour of a filtered copper tailing under an unsaturated condition, studying the effect of self-compaction by self-weight which is triggered by the deposition process through 1D consolidation tests. In addition, the impact of confinement on the stiffness and shear strength was studied by means of unsaturated drained triaxial tests. The initial matric suction was determined based on soil-water characteristic curves for two initially loose dry densities and the water content at which the material leaves the dehydration process. The unsaturated consolidation tests showed that for vertical stresses above 100 kPa and with ratios between the applied matric suction and air entry value lower than twelve, the material approaches saturated condition, reaching up to 95% degree of saturation. On the other hand, for the unsaturated drained triaxial tests, the effect of the matric suction generates increases in the shear strength and the stiffness of the material up to 200% and 600%, respectively. However, the increase tends to disappear as confinement increases.

Long-term evolution of heap surface of paste tailings under erosion / Evolução a longo prazo de pilha da pasta de rejeitos sujeita a erosão

Many mines are moving from conventional tailings storage facilities to filtered tailings disposal systems. The benefits of these systems include increased water recovery, reduced size of containment landfills, improved facility safety, and reduced environmental impact. In geotechnical terms, the challenges are to find the correct way of waste disposal: whether in piles of dry sandy tailings or co-disposal waste rock. The long-term evolution of the surface of fine and sandy tailings stockpiles is a matter of concern. The goal of this study was to quantitatively evaluate the temporal evolution of a paste tailings pile, using a computational model of landscape evolution. For this, SIBERIA, a simulator of the evolution of landscapes under the action of runoff and erosion, was used. The effect of erosion on a trunk-pyramidal tailings pile with about 21% of slope after long periods of decommissioning (100 and 250 years) was studied. The SIBERIA modelling data considered the surface roughness and the average diameter of the sediment particles and the typical properties of iron ore tailings. The results indicate that for a lower Manning roughness coefficient and larger average apparent diameter of the sediment particles (or clods), the lower the sediment transport will be and, therefore, in the long term, the greater will be the integrity of the tailings pile.

Real-Time Electrical Conductivity Monitoring and Correlation with Sulfate Release and Acid Mine Drainage Potential from a Gold/Silver Paste Tailing Storage

Safe disposal of tailings as high-density thickened tailings or paste tailings can reduce the environmental risks of conventional tailings deposits, reduce water use, minimize tailings storage facility footprints, reduce the potential for acid mine drainage (AMD), and minimize risks of failure, among other advantages. In the dewatering process, the addition of flocculants is key to improving the sedimentation of the tailings and the formation of a compact paste. Despite the environmental and operational advantages of using paste tailings, it is not clear how the chemical nature of coagulants and flocculants could influence the discharge of toxic elements (salts and metals) from tailings after storage. In this study, we show the results of the real-time evaluation of the release of polluting runoffs from a paste tailings deposit. To do this, we analyzed paste tailing samples for AMD potential through static and kinetic tests and monitored the electrical conductivity and real-time pH, evaluating the correlation with the sulfate in the thickener and downstream from the tailings deposit. Tailing samples have low sulfur content (<2%) and low acid-generating potential. Moreover, there is no evidence of a significant positive correlation (Pearson’s coefficient r < 0.8) between the sulfate concentrations with the pH or EC. Thus, the chemical nature of the paste tailings prior to discharge has no direct impact on the release of sulfate-rich runoffs from the tailings after its storage. This indicates that the tailings paste at the evaluated site is chemically stable in the short term.

Rheology control of self-consolidating cement-tailings grout for the feasible use in coal gangue-filled backfill

Aiming at the utilization of regional mining wastes including iron tailings sand and coal gangue (CG), a novel coal gangue-filled backfill (CGFB) is proposed in this paper, which is achieved by casting the self-consolidating cement-tailings grout (CTG) into pre-placed CGs skeleton. The mixture proportions of self-consolidating CTGs were first designed based on the rheological properties by adding viscosity enhancing agents (i.e. hydroxypropyl methylcellulose and polyacrylamide) and polycarboxylate superplasticizer (PCE). As a consequence, the static stabilities and filling abilities of fresh CTGs were also strengthened. The filling ability of fresh CTGs is a flowability-related parameter and can be reflected by the surface bugholes of hardened CGFBs. The results indicate that the use of CTG with flow diameter > 25 cm and flow time < 15 s is suitable for filling voids in pre-placed CGs skeleton. With the use of optimized self-consolidating CTGs with high W/C ratios (i.e. 1.0 and 1.2) and mass fraction of 70%, CGFBs show advantages in strengths and strength efficiencies over the conventional cemented tailings backfills. Moreover, owing to the utilization of high-volume solid waste, CGFBs bring benefits of low costs and low environmental impacts.

Projects which push the limits of efficient performance concepts of high-pressure grinding rollers

The ore pretreatment process evolution is briefly addressed, with some milestones and pioneer projects described. Two advanced projects of concentration mills based on the technology of the pioneer-level high-pressure roll milling are discussed. The operating Canadian Copper Mountain Mill is interesting for using the technology which eliminates bottlenecks of the classical semi autogenous milling circuit, with the resultant increase in the mill capacity more than two times as against the initial project value. This result has been achieved for the first time in the world owing to total rejection of the ore pretreatment circuit and thanks to complete transition to press roller milling. Design and engineering of high-pressure roll mill HRC3000, as well as auxiliary milling and flotation equipment is in progress. The high-capacity Iron Bridge Magnetite Mill under construction in Australia can be assumed as the breakthrough project owing to the world&rsquo;s first time trial of Enduron high-pressure grinding rolls by Weir Minerals in milling of magnetite quartzite and in dry production of fine products suitable for further processing without ball milling. The power saving in dry milling using high-pressure rolls will make 30 % at the least as compared with the present-day ore pretreatment by wet milling. Ball mills are withdrawn from the processing circuit, water consumption drops, carbon emissions are decreased, and the tailing storage becomes simpler and safer. In dry tailing storage, the capital investment is cut down as the operation of thickening of wet tailings is rejected, dam construction for tailings ponds is eliminated, and the environmental impact related with contamination of surface and ground water bodies, which is intrinsic to operation of conventional tailings storage facilities, is mitigated.

An Overview of Conventional Tailings Dam Geotechnical Failure Mechanisms

An Overview of Conventional Tailings Dam Geotechnical Failure Mechanisms

Use of an Environmentally Friendly Polymer to Reduce the Water Content in Tailings Slurry

Conventional tailings slurry contains a significant amount of water, and water management is key to ensuring the stability of a tailings storage facility (TSF). Simply reducing the water content in the slurry before discharging it from the mill could be an effective way to improve TSF water management. This study investigated the potential for using an environmentally friendly polymer as a new drag reduction agent (DRA) to reduce frictional pressure loss and also conserve water. It entailed conducting pipe loop tests to assess the polymer’s effect on pressure loss in tailings flow and then applying the test results to validate a numerical model using computational fluid dynamics (CFD). The model was also used to determine the polymer’s optimal concentrations at given solid concentrations and flow rates, its effect on energy efficiency for tailings transportation, and its potential for saving water. A case study for a mid-sized, hard-rock mine with a throughput of 50,000 t/day found that the solid concentration could be increased from 30 to 45% with no pressure loss by applying 1996 m3 of the polymer per day. Adding the polymer also resulted in water savings of 57,552 m3/day. The results of this study demonstrated the potential for using the new DRA not only to improve TSF stability but also to save water.

Alkaline dissolution potential of aluminosilicate minerals for the geosynthesis of mine paste backfill

Geopolymers are aluminosilicate materials geosynthesized by alkaline activation of aluminosilicate minerals and/or industrial byproducts. This study seeks to understand the geopolymerization processes that could occur in Al/Si-rich mine tailings for producing geopolymer paste backfills (GPB). To do so, the alkaline dissolution of fifteen, commonly encountered pure aluminosilicate minerals was investigated. Different relationships of alkaline dissolution extents were investigated. This revealed that the dissolution extent of the involved mineral depends primarily on its crystallization conditions as well as its chemical composition. Preliminary geopolymerization tests were conducted on conventional mine tailings from the Abitibi region of Quebec, Canada. These tests suggested that GPBs could be obtained with appreciable compressive strengths (UCS) (from 79 to 318 kPa) at low alkalinities ([NaOH] ≤ 1 mol/L) in the long term (beyond 28 days). However, in the short term (≤ 7 days), the use of more soluble aluminosilicate materials is mandatory to ensuring the required target UCS for a GPB.

Water recovery improvement by shearing of gravity-thickened tailings for cemented paste backfill

Abstract In mines present in water-scarce areas, the high-water recovery from paste and thickened tailings results in significant cost savings as compared to recovery from conventional tailings. However, it is difficult to dewater tailings with fine particles. In this study, a pilot-scale thickening test was conducted to improve the underflow concentration by rake shearing. The tailing bed was analysed with computed tomography. The porosity and connectivity were determined using a pore network model (PNM) to explain the dewatering enhancement due to shearing. The results show that the underflow concentration increases from 62.3 wt% to 68.6 wt% when the shear rate of the rake is 2 rpm. The porosity decreases from 47.26% to 40.19% due to shearing, representing a decrease by 14.96%. The connectivity of the pores decreases by 8.9% due to shearing. The pore spaces can be divided into ‘balls’, representing the water storage, and ‘stick’ throats, representing the pore connection in the PNM. The numbers of balls and sticks after shearing decrease by 16.59% and 24.01%, respectively. The concept of the ball-to-stick ratio (BSR) was proposed for a pore structure characterisation. The BSR increases by 20.76% after shearing, which indicates that the drainage occurs in the stick spaces rather than the ball spaces. A case study was conducted in Jiashi Copper Mine in the Taklimakan Desert, which is one of China’s most arid areas. The underflow concentration reached 70–72 wt% by improving the picket quantity and height. Based on the thickened tailing system, 14 mio t of water can be saved per year and a water recovery of 57% can be obtained. Therefore, paste and thickened tailing technology can be used for the disposal of tailings in arid areas.

The effects of cement on some physical and chemical behavior for surface paste disposal method

Environmental impacts resulting from conventional tailings disposal such as tailings dam accidents are a common problem for base metal mines around the world. In this context, laboratory-scale studies have been carried out on the Surface Paste Disposal (SPD) method, which is one of the alternative surface storage methods. In this study, three different SPD designs were tested; and volumetric water content, oxygen consumption, and matric suction sensors in first, fifth and 10th paste layers plus pH- electric conductivity (EC) values were all measured. Specifically, it was determined that the amount of oxygen in the environment required for the oxidation of sulfur minerals is reduced in the cemented layers in Design 3. In addition, the cement additive keeps the pH values of the seepage in an alkaline environment (over 7) so that it minimizes the risks of Acid Mine Drainage (AMD) and heavy metals mobilization at low pH values. Also, the EC values started a downward trend and ion dissolution decreased in designs with cemented layers. As a result, it was understood from the sensor measurements that the cemented layers act like a barrier.

Numerical modeling of cracking pattern’s influence on the dynamic response of thickened tailings disposals: a periodic approach

Copper production is an essential component of the Chilean economy. During the extraction process of copper, large quantities of waste materials (tailings) are produced, which are typically stored in large tailing ponds. Thickened Tailings Disposal (TTD) is an alternative to conventional tailings ponds. In TTD, a considerable amount of water is extracted from the tailings before their deposition. Once a thickened tailings layer is deposited, it loses water and it shrinks, forming a relatively regular structure of tailings blocks with vertical cracks in between, which are then filled up with “fresh” tailings once the new upper layer is deposited. The dynamic response of a representative column of this complex structure made out of tailings blocks with softer material in between was analyzed using a periodic half-space finite element model. The tailings’ behavior was modeled using an elasto-plastic multi-yielding constitutive model, and Chilean earthquake records were used for the seismic analyses. Special attention was given to the liquefaction potential evaluation of TTD.

Superiority of Filtered Tailings Storage Facility to Conventional Tailings Impoundment in Southern Rainy Regions of China

In order to evaluate the superiority of a filtered tailings storage facility (FTSF) to conventional tailings impoundment in the southern rainy regions of China (SRRC), the tailings slurry leakage and pollution accident occurring at the wet tailings dam (WTD) of Yinshan were analyzed, the properties of the tailings were tested in a laboratory, and the possibility of tailings liquefaction was evaluated. Comparisons of the slope stabilities of the filtered tailings dam (FTD) and WTD in normal operation, flood, continuous rainfall, and earthquake situations were simulated using the Slide software. The results show that the FTD has less chance of seepage, lower failure probability, and limited potential destructiveness than the WTD with average slope safety factors of 2.120 for normal operation, 1.919 for flooding, 1.204 for continuous rainfall, and 1.724 for a magnitude-6.0 earthquake. The disaster chain model of the WTD of Yinshan belongs to the bursting and slippage chain. As the most safe and effective active prevention measure, the FTSF has the advantages of saving water, protecting the environment, improving its stability in flood and rainfall situations, and reducing the dam failure probability and potential losses, which is greatly applicable to the SRRC.

Feasibility Studies on Pipeline Disposal of Concentrated Copper Tailings Slurry for Waste Minimization

The conventional lean phase copper tailings slurry disposal systems create pollution all around the disposal area through seepage and flooding of waste slurry water. In order to reduce water consumption and minimize pollution, the pipeline disposal of these waste slurries at high solids concentrations may be considered as a viable option. The paper presents the rheological and pipeline flow characteristics of copper tailings samples in the solids concentration range of 65–72 % by weight. The tailings slurry indicated non-Newtonian behaviour at these solids concentrations and the rheological data were best fitted by Bingham plastic model. The influence of solids concentration on yield stress and plastic viscosity for the copper tailings samples were discussed. Using a high concentration test loop, pipeline experiments were conducted in a 50 mm nominal bore (NB) pipe by varying the pipe flow velocity from 1.5 to 3.5 m/s. A non-Newtonian Bingham plastic pressure drop model predicted the experimental data reasonably well for the concentrated tailings slurry. The pressure drop model was used for higher size pipes and the operating conditions for pipeline disposal of concentrated copper tailings slurry in a 200 mm NB pipe with respect to specific power consumption were discussed.

Influence of disposal configurations on hydrogeological behaviour of sulphidic paste tailings: A field experimental study

Surface paste disposal (SPD) is a new alternative employed by the mining industry for storage of mine tailings at the surface. In comparison with the conventional slurry tailings disposal, SPD could offer operational and environmental advantages, such as a better water management, no need for complex retaining dams, a reduced footprint of the tailings disposal area, and the possibility to use progressive reclamation. This paper describes a field investigation through a large-scale experimental cell to assess an SPD application for sulphidic mine tailings. The work addresses the effect of two disposal configurations (i.e., partially cemented and un-cemented) on their hydrogeological behaviour when submitted to actual climatic conditions, focusing mainly on the implementation challenges as well as on the first results obtained. Tailings were deposited in thin layers (10 layers of 10cm each one) into two experimental cells (D×L×H=8m×15m×2m). Cement was added locally (2wt.% of Portland cement) in the first layer of the cell (CC) to study its effect; the second cell (UC) is cement free. The evolution of volumetric water content Ѳ, suction ψ, oxygen consumption and cracks for each cell was monitored during and after deposition. Results show that the CC provides slightly higher Ѳ and smaller ψ values than the UC, most likely due to its geological properties dictated by the bottom cemented layer.

Pseudomonas putida Biofilm Facilitates Fine Solids, Water and Oil Separation from Oil Sands Tailings

Aims: The generation of the tailings, poor settling slurry contaminated with emulsified bitumen, significantly increases the negative impact of oil sands operations on the environment and human health (contamination of surface and ground water with hydrocarbons and naphthenic acids, methane emission), as well as operation cost. Poor effectiveness of conventional tailings settling and clean-up technologies contributes to the daily increase of the quantity of tailings deposited in ponds covering now more than 130 km. There is an urgent need for development of novel tailings settling technologies. The aim of the present study is a comparative analysis of the impact of Pseudomonas putida planktonic and biofilm populations on oil, solids and water separation in tailings, and the investigation of the mechanisms involved in bioseparation. Methodology: Mature fine tailings (MFT) were exposed to Pseudomonas putida planktonic populations and biofilms at agitation followed by static conditions for settling. Oil-solids-water separation was determined by water and oil release from MFT in comparison with untreated tailings. Interaction of tailings with microbial populations was Research Article Kostenko et al.; JSRR, Article no. JSRR.2014.004 111 investigated with scanning electron microscopy (SEM), confocal scanning laser microscopy (CSLM) and energy-dispersive X-ray (EDAX) spectroscopy. Results: The exposure of mature fine tailings to microbial cultures, and especially to biofilms, significantly increase tailings densification, dewatering and bitumen release. The separation efficiency is associated with fine clay aggregation due to the interaction with the microbial cells, biofilm colonies and extracellular polymeric substances (EPS). Conclusion: The mechanism driving the observed biodensification is the aggregation of fine solids via flocculation by biofilm-produced EPS and bacterial cells. Microorganisms were also observed to destabilize emulsions and enhanced residual bitumen release from tailings.

Characterization and dewatering of flotation technological tailings

The treatment of flotation tailings is today a subject of interest in mineral processing because of the potential of wasted materials as an actual mineral resource and because of environmental reasons. Decantation ponds are found at almost every mine in the world. They are large earth fill dams containing the residue of the milling process to extract metals from mined ores. Traditional wet tailings disposal has been problematic due to the risk of ground water contamination and the difficulty in rehabilitating storage sites. Tailings dams are at risk of failure due to leakage, instability, liquefaction, and poor design. In the last few years the use of paste technology in the disposal of mine tailings is increasingly studied as an option to conventional tailings dams. The Lucky Invest Concentrator is located in the Eastern Rhodopes Mountain of Bulgaria. Since 1959 lead-zinc ores are dressed. Finally, during the flotation cycle lead and zinc concentrates are produced. The final technological processing waste precipitates in tailing pond. Research and development program has started to established opportunities to obtain dry deposit of the ore processing residue and analyses the feature of new tailing disposal method. The tailings particle size distributions and chemical compositions were determined. The data from laboratory and pilot scale tests clearly illustrate that there are the possibilities to obtaine lead-zinc dewatered tailings. The experimental results show that new cyclone modifications have a potential in dewatering technology of flotation tailings. It appears that dewatering cyclones can be an approach on new tailings pond elimination technology.

Electrokinetic remediation of mine tailings by applying a pulsed variable electric field

Following the flotation step of copper sulphide mineral processing, a considerable amount of ground ore in the form of a pulp containing heavy metals and other polluting compounds is discarded as waste, known as “mine tailings”. This waste is deposited behind dams, and unless it is treated, it represents a danger to the environment because the natural oxidation of heavy metals makes the waste chemically unstable.Electrokinetic remediation (EKR) is a technology used to remove contaminants from soils. In recent years, the technology has been of research interest for stabilising mine tailings from the copper industry.Nine EKR experiments with pulses of sinusoidal electric fields (by applying simultaneously DC and AC voltages) and an AC voltage frequency of the order of kHz were performed to improve conventional EKR and stabilise synthetic tailings samples. The synthetic tailings were prepared based on representative data for tailings from a combined Cu–Mo concentrator plant.It was found that, in general, the use of a pulsed sinusoidal electric field favoured overall copper removal in the EKR cell, and particularly good results were observed when this type of electric field produced periodical polarity reversal in the electrodes.The best results in terms of overall cell removal and specific energy consumption were obtained under the following conditions: (i) effective voltage of 14.6V (VDC=10V and VAC=15V), (ii) AC voltage frequency 1000Hz, (iii) electrical field applied in pulses with a time ratio of 25.