Dense Medium Separation Research Articles

Transformations of Critical Lithium Ores to Battery-Grade Materials: From Mine to Precursors

The escalating demand for lithium has intensified the need to process critical lithium ores into battery-grade materials efficiently. This review paper overviews the transformation processes and cost of converting critical lithium ores, primarily spodumene and brine, into high-purity battery-grade precursors. We systematically examine the study findings on various approaches for lithium recovery from spodumene and brine. Dense media separation (DMS) and froth flotation are the most often used processes for spodumene beneficiation. Magnetic separation (MS) and ore gravity concentration techniques in spodumene processing have also been considered. To produce battery-grade lithium salts, the beneficiated-concentrated spodumene must be treated further, with or without heat, in the presence of acidic or alkaline media. As a result, various pyro and hydrometallurgical techniques have been explored. Moreover, the process of extracting lithium from brine through precipitation, liquid–liquid extraction, and polymer inclusion membrane separation employing different organic, inorganic, and composite polymer sorbents has also been reviewed.

A new approach for modelling of static stability of dense medium separator

A new approach for modelling of static stability of dense medium separator

Laboratory Comparison of Dense Medium Separation and Acid Leaching for Preconcentration of Coarse Rejects from Phosphate Washing Plant

Reverse flotation is a commonly used method for separating carbonate minerals from apatite, but its application to phosphate beneficiation coarse rejects, which are low in P2O5, is often costly due to the high collector dosages used. This study aimed to explore alternative techniques for preconcentration before flotation to improve recovery rates and reduce costs. Our investigation focused on dense medium separation and acid leaching. Dense medium separation, conducted at a cut-off density of 2.76, yielded a preconcentrate with 27% P2O5 and a recovery rate of 90%. The feed material had an initial P2O5 content of 20.52% and a particle size range of +40 µm to −4 mm. In contrast, acid leaching, employing an 8% acetic acid solution over 35 min, yielded a concentrate with 29.11% P2O5, an LOI of 8.99%, and a recovery rate of 100% from an ore fraction [400–200 µm] with an initial P2O5 content of 22.82% and an LOI of 15.78%. Furthermore, integrating flotation and leaching resulted in a concentrate with 32.27% P2O5 and a recovery rate of 98.38%. These findings suggest that combining acid leaching with flotation can enhance P2O5 recovery and reduce processing costs for low-grade phosphate ores.

Can preconcentration of cassiterite from its pegmatite ore reduce processing costs and improve operational sustainability?

Different concentration techniques were evaluated for preconcentration of a mineral ore at a coarser size to avoid energy and resource wastage. Specifically, the aim was to reduce milling costs and energy required in the beneficiation of tin. In this study, cassiterite (0.17% Sn) was the mineral of interest in a pegmatite ore body associated with quartz (SiO2 > 60%) and alumina (Al2O3 > 20%). Three concentration techniques, namely dense media, shaking table, and flotation, coupled with characterization analysis, were used to assess the concentration response. The results confirmed that particle size and mineral liberation impact the separation process. High recovery and grade were obtained with gravity concentration methods (dense media and shaking table) for coarser (+300 to +212 μm) and intermediate (+150 to +53 μm) particle sizes. Lower recovery and grade were identified for much finer sizes (-53 to -38 μm). Flotation produced a high-grade product at a relatively low recovery and appeared to be only applicable to finer grains. Separation efficiency based on Schulz's equation measured a segregation performance of 74.8% for dense medium separation and 60.7% for the shaking table for the coarse and intermediate particle sizes. Flotation only achieved a separation of 30%-40%. The results suggest that use of dense media separation as a rough preconcentration method prior to further grinding, and the utilization of a more advanced concentration technique for mineral recovery and upgrade, constitute a successful approach to improve process economics.

Approaches to Recycling of Engine Air Filters

AbstractIt is becoming increasingly important to be able to recycle mass‐produced products such as engine air filters. Different processes were tested to investigate whether it is possible to recycle the composite material. Thereby, comminution with cutting stress is particularly suitable for disintegration. Next on, the filter medium could be separated very well with the help of a zig‐zag separator. The sorting of polyurethan foam and polypropylene hard plastic could be achieved with a dense media separation. It became clear that the pretreatment, which is intended to liberate the material, has a significant influence on the sorting result and the purity of the products.

Multi-year in situ hydrogeochemical monitoring of hard rock lithium mine tailings in a large-scale experimental pile

Spodumene, a lithian mineral found in granitic pegmatites, is a major source of lithium. In situ, multi-year and large-scale (>10s of tons) predictive hydrogeochemical studies can be of great value for informing mine waste rock and tailings management, not least because the material is exposed to the actual climate where it is meant to be stored. However, such studies are rare given their cost and size, and previous ones have focused mainly on sulfide-bearing materials. An experimental field cell filled with spodumene beneficiation tailings was built at the Whabouchi lithium mine site in northern Québec (Canada) and monitored during four consecutive years. In parallel, column laboratory kinetic testing on the same material was conducted for water quality parameters to compare the effect of testing scales on the geochemical behavior. Geochemical results and release rates were overall similar between laboratory and field, and consistent with previously published laboratory results for materials from the same site. The leachates were neutral to slightly alkaline, with ions from feldspars (Ca > Na > K) and residual spodumene (Li) being notable solutes. Concentrations for most solutes surveyed remained higher in the field after four years than in columns at the end of the experiment. One major difference between laboratory and field was a brief (less than 2 years) increase in iron concentrations from the field cell, resulting in Fe-oxyhydroxides precipitation, that was not observed in laboratory. The source of this iron is arguably residual ferrosilicon (used for dense medium separation) and this difference is attributed to the different testing conditions and configurations in the laboratory versus in situ. Field hydrogeological results highlight strong seasonal patterns and the rapid response of this sand-like, sulfide-poor material to ambient temperature changes and wetting-drying events. The tailings both wet and drain rapidly and easily given their water retention curve and the range of matrix suctions recorded during frost-free months. Net infiltration through the tailings was estimated to represent 55% of total precipitation in summer (June–October) 2021. This study provides a comprehensive assessment of the environmental behavior of hard rock lithium mine tailings under real, sub-arctic climatic conditions and outlines similarities and differences between laboratory- and field-generated geochemical results.

Modelling, analysis and validation of a dynamic dense medium separation circuit model for detecting medium losses

Dense medium separation circuits use a dense medium to separate low density waste material from high density valuable minerals. Since the dense medium is an expensive consumable, it is recovered after separation of the valuable minerals from waste. A dynamic nonlinear model of a dense medium separation circuit of an iron ore plant in South Africa is developed to track the flow of medium in the circuit. An extended Kalman filter is designed for estimating observable but unmeasured states. The model is validated using online plant data. This paper serves as a precursor for further work to detect and mitigate expensive medium losses in the circuit.

Experimental validation of enhanced corrosion resistance of ferrosilicon in dense medium separation of refractory diamond-bearing materials

Experimental validation of enhanced corrosion resistance of ferrosilicon in dense medium separation of refractory diamond-bearing materials

Beneficiation Processing of Magnetite ore from Lampung as Dense Media for Dense Medium Separator in Coal Washing Plant

Until recently, coal washing plants in Indonesia are still using imported magnetite from Australia as dense media for dense medium separator units. To be effectively utilized as a dense media, magnetite ore needs to be concentrated to remove gangue minerals so that the final product will have more than 95% magnetic content, 95% weight passing 53 microns, and relative density ranging from 4.9 – 5.2 g/cm3. Experimental studies have been performed at the Department of Metallurgical Engineering ITB to concentrate fine magnetite ores from Lampung Province. Two process routes were chosen: grinding-magnetic separation and magnetic separation-grinding. Products from the two routes were sieve size analyzed, assayed and characterized. Magnetism characteristic was analyzed with VSM and relative density was measured with pycnometer. The first process route products have maximum magnetic content of 99.1% and particle weight passing 53 microns of 95.7%, while the second route have magnetic content of 95.2% and particle passing 53 microns of 97.1%. Concentrates from both routes have the same relative density of 4.5 g/cm3. Characterization by XRF and AAS gives Fe content of 46.6% and 48.8% for the first route product, and 52.1% and 52.9% for the second route. Lampung magnetite ore gives lower magnetism characteristic compare to Australian magnetite ore. Finer particle size gave lower magnetic saturation value, hence lower magnetism.

Технологическая эффективность методов модифицирования свойств ферросилиция и водных систем в процессах тяжелосредной сепарации труднообогатимого алмазосодержащего материала

Introduction. Taking into account the results of experimental bench studies previously carried out at ICEMR RAS on the effectiveness of the use of physical, physico-chemical and electrochemical influences to increase the corrosion resistance of ferrosilicon in the technology of DMS of diamond-containing raw materials of weakly altered kimberlites of the primary deposits of the Mirny ore field, at this stage, their pilot industrial testing was carried out under processing conditions intensively altered ores of deep horizons with the involvement of alluvial and technogenic deposits in the processing of diamond-containing raw materials. Research methods. In accordance with the testing methodology, the tests were carried out in two directions, the ultimate task of which was to create process conditions that ensure the protection of ferrosilicon granules from corrosion destruction caused by their oxidation upon contact with corrosive aqueous systems: 1. Modification of the properties of the liquid phase of the ferrosilicon suspension to values that reduce its corrosiveness towards the surface of ferrosilicon granules (variable factor – properties of the aqueous process medium). 2. Modification of the surface properties of ferrosilicon granules by creating a protective shell on it, preventing their oxidation during contact with corrosive aqueous systems (the variable factor is the surface of the ferrosilicon used: original and coated). Research results. The article presents the results of pilot industrial tests of technical solutions, the implementation of which made it possible to reduce the consumption of ferrosilicon in the dense medium separation cycle of diamondcontaining material using the above methods for modifying the properties of the aqueous medium and ferrosilicon used for the preparation of the ferrosilicon suspension, by increasing the corrosion resistance of the components of the ferrosilicon suspension. Discussion of research results. A comparative assessment of the technological efficiency of the applied methods for modifying the properties of the aqueous phase and ferrosilicon under experimental test conditions was carried out with the determination of ferrosilicon losses in the regeneration cycle of the ferrosilicon suspension and its content in the volume of the ferrosilicon suspension. The use of electrochemically treated water as a reagent for modifying the properties of the components of a ferrosilicon suspension provides a reduction in ferrosilicon consumption by 1.9 times, but is limited by the fairly high power consumption required for processing large volumes of water in the DMS process. The use of inert nitrogen gas as a bubbling agent instead of oxygen-containing air in the ferrosilicon suspension preparation cycle reduces ferrosilicon consumption by 2.5 times while increasing its service life by 1.5 times. However, the use of this method is limited to use only in part of the DMS process – the cycle for preparing a ferrosilicon suspension. The use of the method of nitriding ferrosilicon granules ensures a reduction in ferrosilicon losses by 2.7 times while increasing its service life by 2.2 times. At the same time, the entire volume of ferrosilicon in the process retains its anticorrosion properties in relation to the corrosive components of the surrounding water system. Conclusion on the article. A comparative analysis of the results obtained using mathematical processing methods has established the maximum technological efficiency of using the method of nitriding the surface of ferrosilicon, which causes the creation of a protective nitride layer on it, ensuring high corrosion resistance of ferrosilicon granules under the conditions of active processes of dense medium separation of diamond-containing raw materials of the material composition under consideration. Nitrided ferrosilicon has parameters that make it possible to increase its service life by no less than 2.2 times while reducing losses in the regeneration cycle by 2.7 times. Suggestions for practical applications and directions for future research. The experimentally established advantages of the technological efficiency of using nitrided ferrosilicon in DMS processes of diamond-containing raw materials are recommended for industrial implementation in the conditions of ALROSA’s processing plants and can be used in similar schemes for dense medium separation of mineral raw materials of various compositions. Tests are planned under industrial conditions at one of the processing plants of PJSC ALROSA.

Multi‐rate event‐triggered control with imperfect data for dense medium separation

AbstractThe stability control of suspension density is an important means to ensure the quality of fine coal in dense medium separation (DMS) process. This paper focuses on the tracking control issue of the dense medium suspension density in a non‐uniform sampling and networked control environment, and proposes a multi‐rate event trigger control design method. Firstly, lifting technique and multi‐rate identification method are adopted to establish the multi‐rate model. Secondly, a multi‐rate event‐triggered predictive control (MEPC) algorithm is proposed to reduce the waste of communication resources and ensure tracking performance. Furthermore, by using a Kalman filter to eliminate the effects of noise and developing a compensation mechanism to predict the lost data, a robust MEPC (RMEPC) algorithm is further proposed for imperfect data in the actual production process. Finally, the hardware‐in‐the‐loop simulation experiments with actual parameters of coal preparation plant have been carried out, showing the effectiveness of the proposed method.

Dense Medium Cyclone Separation of Fine Coal: A Discussion on the Separation Lower Limit

The separation of fine coal has been widely discussed in the coal preparation industry due to its high economic potential. Dense medium cyclone (DMC) is the most efficient equipment available for fine coal separation. However, the industrial application of DMC is far from satisfactory due to operational difficulties and maintenance. In this research, particle settling behavior in a dense medium cyclone was analyzed for improved separation. The calculation result about feed pressure and separation lower limit, which fits the experimental data well, might be a guidance for industrial DMC design and operation. According to the calculation result, it is highly recommended that the separation lower limit be set at 0.2 mm rather than 0.1 mm, because the feed pressure head required for the latter (50 D) is three times higher than the former (15 D).

Geochemistry and mineralogy of a spodumene-pegmatite lithium ore at various mineral beneficiation stages

Spodumene is currently the main source of lithium (Li), and Li release in mine waters stands out as a common feature of the otherwise scarcely studied spodumene mine tailings. In order to study how mineral beneficiation affects the geochemical behavior of a pegmatitic spodumene ore and the quality of its drainage, materials from the Whabouchi mine project (Québec, Canada) were submitted to advanced mineralogical characterization and kinetic testing in columns and weathering cells. Materials were sampled at various pilot processing steps, from raw ore to concentrator feed and tailings from dense medium separation and spodumene flotation. Processing did not modify markedly the chemical composition of the minerals and the mineralogical assemblage, except the spodumene content. Besides the major quartz, feldspars, spodumene, and muscovite, many accessory minerals were identified including Nb-Ta oxides and U-bearing minerals. Kinetic testing results indicate that all the studied materials produce neutral to slightly alkaline leachates (pH 7–8). Generally, elemental concentrations decrease rapidly over the first few flushes, are higher in columns than in weathering cells, and are higher for finer-grained processed materials. Elemental mobility is not necessarily proportional to bulk-rock abundance and liquid-to-solid ratio, overall following the order Ca (10 s of mg/L) > Na, K (10 s of mg/L to sub-mg/L) > Li, U (mg to sub-mg/L) > Mn, Fe, Al (sub-mg/L). Uranium mobility seems linked to scattered Ca-uranyl-(Si or P)-bearing voids and fracture-filling soluble minerals rather than primary uraninite, and Ca-uranyl-carbonate complexation is suggested as a promoting factor. Thermodynamic equilibrium calculations only identify clay minerals and metal (hydr)oxides as possible secondary minerals; formation of Al and Fe colloids is experimentally evidenced. Specific surface area and rinsing volume-normalized release rates, however, highlight effects of both processing and the testing protocol on the reactivity of the studied materials. The most processed material studied, flotation tailings, consistently produced the lowest normalized release rates for all the elements surveyed, while the most aggressive testing protocol (weathering cells, with frequent flushes at a high liquid-to-solid ratio) always yielded the highest normalized release rates. This laboratory-scale study outlines how mineralogy (both major and trace), processing, and testing protocol, affect the geochemical behavior of pegmatitic spodumene ore and tailings.

Review on the Beneficiation of Li, Be, Ta, Nb-Bearing Polymetallic Pegmatite Ores in China

Lithium-bearing polymetallic pegmatite ores are an important raw material for lithium extraction. They contain not only lithium but also other associated elements such as beryllium, tantalum, and niobium, with great recovery values. It is therefore often called lithium-bearing polymetallic pegmatite ore (LPPO). The recovery and utilization of Be-bearing minerals in LPPOs have yet to be further studied. This paper briefly expounds the geological aspects of LPPO deposits in China and Chinese experiences on the beneficiation of LPPOs, with special emphasis on the flotation separation of lithium-beryllium minerals. In LPPO, spodumene is the main target mineral for lithium, while beryl is the main Be-bearing mineral in a fine-grained embedded state. If the BeO grade of LPPO is greater than the industrial grade (BeO ≥ 0.04%), it will be processed for recovery. Tantalum and niobium minerals are mainly in the form of tantalite, columbite, or ferrotapiolite, which may be recovered by gravity separation or magnetic separation. Gangue minerals are mainly composed of albite and quartz. Currently, the most commonly used methods for separating the target minerals from gangue are dense medium separation and flotation. The manual sorting method has become obsolete and is expected to be replaced by machine sorting methods such as color sorters and X-ray transmission sorters. Flotation is the main method for the separation of fine-grained beryl and spodumene. The success of flotation depends on the selection of suitable pretreatment methods and appropriate flotation reagents for altering the surface properties of spodumene and beryl and for expanding the floatability differences between spodumene and beryl and between spodumene and gangue.

Product quality prediction in dense medium coal preparation process based on recurrent neural network

ABSTRACT Dense medium separation is one of the most widely used methods for coal beneficiation, and an accurate estimation of product coal ash is the prerequisites to maximize the resource value. In this work, data pre-cleaning and multi-layer feature learning process of deep learning are explored to predict the product quality more accurately. The research results show that, the deep learning model considering the time series characteristics of process variables can predict the change of product quality better, which could be attributed to the fact that the full considers time series relationship between process data and product quality. Specifically, the prediction value obtained by using a single-layer, multi-unit recurrent neural network model (GRU) is improved with Root Mean Square Error (RMSE) at 0.061, and the RMSE for multi-step prediction (10 min) is 0.262. What’s more, the prediction error gradually decreases and tends to be smooth with increasing time step. It is suggested that the time step used for data reconstruction should be the time of raw coal coming through to the clean coal belt. This work provides an innovative idea for improving online prediction of coal ash and is of significant importance for precise control of dense medium separation in application.

Application of lean Six Sigma to improve the dense medium separation performance at a diamond processing plant in Namibia

Lean Six Sigma (LSS) is a rigorous, data-driven, and results-oriented process improvement philosophy. To date, there is no evidence of a study of the application of LSS in a diamond plant. One of the most common recovery methods in the diamond industry has been dense medium separation (DMS), also known as heavy medium separation (HMS). The main purpose of the study is to investigate how to implement LSS to improve the dense medium separation performance at a diamond plant. Further, we investigate the factors impacting DMS by finding the most relevant factor/s and applying the principles of Lean and Six Sigma to improve the performance of dense medium separation (DMS) at a diamond plant in Namibia. The research found out that factors affecting DMS include cyclone pressure, medium density, viscosity, and worn cyclone parts and maintaining these parameters within narrow limits in relation to the correct set points is beneficial. Also, the study established that, operational conditions (cyclone pressures and medium densities) are the topmost factors affecting DMS followed by viscosity and lastly, equipment dimensions. The application of LSS reduced downtime delays and boosted the associated production, thus achieving cost-efficiency, improved DMS performance and reducing waste. Diamond mines are found in large numbers in Africa, and this study will help the mines to improve their efficiency. Further, using the lens of theory of swift and even flow, the LSS is applied in the diamond company to streamline the DMS performance. Further, it poses key implications for future LSS research.

Decontamination of neutron-activated radioactive concrete waste by separating Eu, Co, Fe, and Mn-containing sand particles using dense medium separation.

Neutron-activated concrete waste is one of the most challenging radioactive wastes to decontaminate because the radionuclides exist in a chemically stable binding state, and it is very difficult to break those bindings with the conventional acid decontamination method. Here, we suggest a new dense medium separation (DMS) of felsic and mafic minerals from simulated neutron-activated concrete waste using sodium-polytungstate (SPT) solution because most elements (Eu, Co, Fe, and Mn) that can be activated by neutrons are concentrated in mafic minerals. We also determined the optimal density of the SPT solution as ∼ 2.70g/cm3, and a high degree of decontamination was achieved for sand particles ranging from 75 to 500µm in size. Under these optimized conditions, DMS (80.02%) exhibits much higher radionuclide removal efficiency (RRE) than 5M acid decontaminations (23.27-31.29%) for Eu. Furthermore, DMS (59.38-63.36%) shows similar RRE to 5M acid decontaminations (41.67-73.94%) for Fe, Mn, and Co. We believe this DMS process could be useful and applicable to the decontamination of neutron-activated concrete wastes because it is possible to perform a large-scale process compared to conventional acid decontamination methods, which is also advantageous in reducing secondary waste generation and facile radionuclide recovery.

Valorization of South African Coal Wastes through Dense Medium Separation

Sustainable management of coal waste is one of the major environmental concerns for coal mining, whether active or legacy, worldwide. Coal dump deposits demand a large physical area or footprint for disposal of solid waste, change the topography, and generate both pyritic dust and acid rock drainage (ARD) where pyritic coal waste is deposited. The beneficiation of dump deposits or, preferably, of coal waste prior to its dumping can reduce or even eliminate the liabilities related to coal waste management. In this work, dense medium separation studies of coal discards, using heavy liquids, resulted in three pooled fractions from typical South African coal waste discards from the Mpumalanga region for future use: (a) a fraction of low density with increased calorific value; (b) a fraction of intermediate density, rich in ash and acid neutralizing minerals and lower in sulfur; and (c) a fraction of high density, rich in sulfidic minerals including pyrite. The fractions were characterized using particle size analysis, sink-float studies, static tests to predict ARD potential, proximateand ultimate analysis, and gross calorific value. The results showed that approximately 70% of this discard coal is composed of a material of sufficient quality for energy generation in conventional power stations. A pyrite-rich concentrate made up 2% of the total discard mass; comprising more than 45% of the sulfidic mineral present in the feed and displaying no acid neutralizing capacity (ANC). The remaining discard fraction, with intermediate density, presented potential to be used for several ends including soil fabrication, co-disposal or as aggregate material in civil engineering; additional testing to ensure applicability for the selected re-purposing option should be chosen based on proposed use.

Mineralogical Factors Affecting the Dense Medium Separation of Nickel Sulfide Ores

Dense medium separation (DMS) is often used to reject a large portion of gangue material upfront to create cost and energy savings during processing. As lower-grade ores with complex mineralogy are being increasingly exploited, the properties of the gangue minerals begin to play a more important role in the upgrading of the ore. It is therefore important to understand these mineralogical factors to be able to select suitable processing routes for specific ore types. Two nickel sulfide deposits in southern Africa were chosen as case studies to understand differences in DMS efficiency when applied to different ores: Ore A and Ore B. Both ores showed nickel upgrades using DMS and the products were then characterized using QEMSCAN, with the aid of X-ray diffraction and electron probe microanalysis. Overall, particle density remains the main control on the separation, followed by sulfide texture, with massive and net-textured sulfides having larger grain sizes and therefore better liberation than disseminated sulfides. In addition to the concentration of sulfides, primary and secondary silicate minerals are separated by their density differences, which can affect the recovery of finely disseminated sulfides associated with them. Particle size is also important in DMS, with material near the cut-point density separating on size rather than density. The understanding of the mineralogical properties affecting DMS can aid in the prediction of the suitability of DMS for different ore types.

Simulation and Performance Evaluation of Three Product Dense Medium Cyclone

ABSTRACT The conventional flowsheet of coal washing plants includes sequential units where different coal size fractions are washed. Generally, coal washeries include dense medium vessels/drums and cylones for coarse and intermediate sizes as well as spirals and flotation units for fine/ultrafine fractions. Three product-dense medium cyclones (TPDMC) may replace the traditional flowsheet, enabling coals of a wide size range to be treated at once. TPDMC is widely used in the world, particularly in China, and has many potential advantages, yet there is limited data about its performance and simulation. In this study, the performance of a 70 t/h feed capacity TPDMC used for hard coal washing was investigated and its separation behavior was simulated using two different dense medium separation models. Test results revealed that the separation performance of TPDMC was efficient, yet different geometric designs might be required for the treatment of various coal types.