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"The Circular Economy (CE) will play an important role in shaping a resource-efficient society. Enabling this transformation from a linear to a CE requires precise quantification of resource efficiency and thus the economic viability of the system. Based on the development of simulation tools of classical minerals processing and process metallurgy, the Outotec (2018) HSC simulation platform could be further developed (gleaning from many academically published works of the author listed below), permitting the simulation of the CE system and to subsequently calculate its resource efficiency. It enables the estimation of a simulation-based Recycling Index (RI) from a product’s Bill of Material (BoM) and Full Material Declaration (FMD). It is a unique methodology for Design for Recycling (DfR) based on minerals engineering linked to a deep understanding of minerals and metallurgical process engineering. A key to this simulation is a detailed understanding of the mineralogy (both geological and designed) of the CE system and its many products, materials and systems, both in a geological mineral and a product-designer-mineral sense. In addition, a detailed understanding and quantification of the thermodynamic properties of the system (both energy and exergy/entropy) is key to understanding its economics and its limitations. With this approach, the actual losses of the CE system are shown and thus highlights the limits of the CE as defined by minerals and metallurgical process engineering principles. INTRODUCTION From the dawn of the industrial era up to today, many of our products have been created according to the principles of a linear economy: we find resources, make a product, and then dispose of it when we are done using it. But in recent years, there has been a growing awareness of the need to move to a Circular Economy (CE), an approach that aims to maximize the usefulness of products, components and materials across the entire lifecycle. In terms of recycling, this means achieving maximum recovery of materials once products reach the end of their usable life while also maximizing resource efficiency. Of importance is therefore also not only the recovery of critical technology elements that make the CE system run, but also the criticality of the metallurgical infrastructure that must be present to recover these elements economically. Ellen Macarthur (2017) defines the CE as “Looking beyond the current ""take, make and dispose” extractive industrial model, the circular economy is restorative and regenerative by design. Relying on system-wide innovation, it aims to redefine products and services to design waste out, while minimising negative impacts. Underpinned by a transition to renewable energy sources, the circular model builds economic, natural and social capital.” However, when translating this significant message to images, it is striking that the key extractive industry is not depicted in the Ellen Macarthur as well as EU depiction of a CE (EU 2015). Other CE discussions are also wanting in their fundamental detail and description e.g. Accenture (2015) and Beaulieu et al. (2016)."

Jan 1, 2018

By Minna Päällysaho

For the first time, the idea of sustainable development was recognised at a high political level at the UN Conference on Environment and Development held in Rio de Janeiro in 1992 (UNEP, 1992). Then the governments of the world committed themselves to promote sustainable development in their national activities and international co-operation. In 2001, the European Council approved the EU Strategy for Sustainable Development (European commission, 2011). This complements and supports the EU?s so-called Lisbon Strategy (European council, 2000) on competitiveness. The revised Strategy for Sustainable Development was approved in June 2006. Recently sustainability has had an important role in policy and decision-making while the public awareness towards limits of the environment has been rising. However, the indicators of industrial sustainability satisfy primarily the needs of corporate management and global investors. The information is often broad and non-specific and might occasionally even give a false impression. Moreover, contradictions between environmental, economical and social aspects also point out the unreliability of existing sustainability indexes. Therefore, the current state of affairs serves the interests of neither the industry nor the policy makers. Current corporate sustainability indexes and indicator systems need to be assessed with scientific methods encompassing the identification of their strengths and weaknesses. This requires quantitative and qualitative assessment and synthesis of existing indexes and indicator systems, providing new data on the functionality of existing corporate sustainability indicators. Therefore, the assessment lays the foundation for the development of new, more balanced sustainability index. Our first aim in this multidisciplinary article is to analyse existing global sustainability indexes for process industry. Second, we will introduce a first version of a new sustainability index for process industry, which includes the environmental, social and economic impacts of the plant, as well as legislation aspects.

Sep 1, 2012

By M. Abdollahy

Solvent extraction of gallium from Bayer solution of Jajarm Alumina plant was investigated us-ing Kelex100 as extractant. Taguchi experimental design method was used in order to optimize the separation factor of Ga and Al. Optimum conditions were obtained as follows: Temperatuer: 65°C, volume ratio of aqueous phase to organic phase: 3.0:1.0, process time: 60min and organic phase containing 15vol.% Kelex100, 5vol.% isodecanol in kerosene. In this conditions, 74% gallium and 0.3% aluminum was extracted and separation factor was obtained 828.63.

Jan 1, 2014

By G. Önal

Recovery of nickel and chromite from the tailings has been studied on the samples with 0.214 % Ni and 5.10 % Cr2O3 content and taken from Orhaneli Chromite Concentration Plant. Mineralogical examinations of the samples showed the existence of chromite, olivine, pyroxene, chrysotile, anti-gorite, chlorite, idingite, tremolite and calcite together with trace amounts of millerite, pentlandite, pyrite, pyrrhotite, hematite and limonite type iron oxide minerals in partially serpantinized dunite type particles. In order to recover chromite from Chromite Concentration Plant tailings Mozley Table and Knelson Separator are used and concentrates containing approximately 42% and 46% Cr2O3 are produced respectively with 40% recovery. Most of the nickel remained in the tailings. Therefore, acidic leaching tests are performed in order to dissolve nickel from these tailings. Effects of particle size, acid concentration, temperature, leaching time and solid/liquid ratio on the nickel leaching efficiency are investigated. The optimum leaching conditions are found as 250 g/L acid concentration, 1/5 solid/liquid ratio, 2 hours of leaching time and 60°C temperature, almost all nickel is dissolved at the optimum conditions and acid consumption is about 841 kg/t. Repeated leaching tests are carried out in order to have enough Ni content in the leach liquor for the further treatment of solutions. After repeated leaching tests, leach liquor contains 3 kg/m3 Ni, 48 kg/m3 Fe, 2.2 kg/m3 Si, 23 g/m3 Cr and 590 kg/m3 H2SO4. Ni is recovered from that solution by precipitating with H2S followed by HNO3 dissolution and precipitating Ni as hydroxide with 63% Ni content. Leach cakes are subjected to the gravity separation (Mozley table) to recover the remained chromite and a chromite concentrate with 47% Cr2O 3 content is produced with 53% recovery. As a result of the abovementioned tests, a conceptual process flow sheet is proposed for the treatment of these chromite concentration plant tailings.

Jan 1, 2014

By G. N. Jadhav

In India, bauxite deposits are concentrated in Central India, Western Ghats and Eastern Ghats. Bauxites from various regions in Gujarat were identified during the present investigations of geochemical mapping. Different types of Bauxites samples were collected from Kachchh, Jamnagar, Porbunder, Junagarh, Bhavnagar and Amreli areas of Gujarat state and were studied in detail for their geochemical signatures to plot the data on Geochemical map. Raw bauxites were characterized by using powder XRD, XRF, ICP and optical microscopy techniques (with the help of Model microscope having both transmitted and reflected light setups) and were later examined to grade their quality. Most of the bauxites from Kachchh region were of high-grade (gibbsitic) type; while those of Sourashtra region were of low-grade (lateritic / calcitic) types. Most of these bauxites were either of ferruginous/lateritic or of calcareous/calcitic types. Based on the mineralogical composition, such as gibbsite, hematite and/or goethite, Kaolinite and calcite minerals present in particular bauxites, the deposits were graded. Finally, the Geochemical mapping of Bauxites for Gujarat region was prepared and discussed.

Sep 1, 2012

By X. Q. Cao

As the second largest phosphate resource in the world, Chinese phosphate ores generally grades with low of P2O5. The presentation of beneficiation test on the low grade of phosphate rock in this paper may be used for a reference for development and utilization of the similar reserves. The ore is a marine sedimentary phosphate rock containing low grade of P2O5 and high content of MgO and R2O3; The banded structure shows its suitability for heavy medium separation. The laboratory heavy liquid testing results indicate that as specific gravity of the heavy liquid is 2.85 g/cm3, a rougher concentrate assaying 28.71% P2O5 could be obtained while the rougher tailings contain only 4.47% P2O5. When the combined process with heavy liquid separation followed by direct & re-verse flotation is employed to treat the feed containing 21.15% P2O5, 3.79% MgO, 1.86% Fe2O3, 3.66% Al2O3, 23.75% A.I, and specific gravity of heavy liquid is 2.84 g/cm3, the optimum mesh of grind is 67.5% minus 200 mesh, a phosphate concentrate contained 32.51% P2O5, 0.48% MgO, 0.81% Fe2O3, 1.69% Al2O3 can be produced at a yield of 55.24%. The concentrate P2O5 recovery is 85% with which quality comply with the Class A specifications for production of phosphate fertilizer.

Jan 1, 2014

By D. Vega, P. R. Brito-Parada

"Small diameter (10 mm) hydrocyclones have been applied successfully for the separation of particle suspensions in the micron size range. These hydrocyclones are attractive because they show a bypass fraction larger that the water recovery, resulting in a high particle recovery to the underflow as well as low water recovery. However, this is a disadvantage when the purpose of the hydrocyclone is classification because of the large amount of fine particles that are misplaced in the underflow. The aim of this study is to explore, experimentally and computationally, the influence of design parameters on the classification process. In this work, a full factorial experimental design was defined to carry out comprehensive experimental tests using glass beads (0-20 µm) as the particulate system. We show that the dimensions of spigot and vortex finder diameter can be effectively manipulated to change the separation performance of the system and the energy consumption. A CFD model was developed that is able to predict particle size distribution. The numerical results for the partition curves showed very good agreement with the experimental data. INTRODUCTION Small diameter hydrocyclones are a very attractive separation technology for fine particle suspensions. Since the hydrocyclone diameter is directly proportional to the cutsize that can be achieved, 10mm hydrocyclones have been shown to be very effective in collecting particles in the micron-size range. In addition, while in large hydrocyclones the bypass, i.e. the fraction of particles that report to the underflow without classification, is similar to the water recovery, in 10mm hydrocyclones the bypass fraction is considerably larger than the water recovery. Its high particle recovery and low water recovery makes small hydrocyclones ideal for ultrafine particle classification and dewatering applications in mineral processing. The separation of mineral suspensions achieved using small hydrocyclones has been the focus of various studies. Pasquier and Cilliers (2000) derived a general classification model from experimental data of fine silica concentration in 10mm hydrocyclones; the model was able to describe the fish-hook partition curve. The effect of operating conditions has also received some attention in the literature. Cilliers et al. (2004) showed that an increase in temperature positively effects the recovery of fine silica particles in small hydrocyclones, by increasing the bypass and decreasing the cutsize. Neese et al. (2015) showed that the cutsize in 10mm hydrocyclones can be further decreased by operating at higher pressure, which also trebled the throughput."

Jan 1, 2018

By Gorki Davila, Irineu Brum

"Brazil has large reserves of coal (32 billion tons) located predominantly in the south of the country. Despite the relative ease of exploitation, these resources have been underestimated as a source of energy. Currently the country's strategic planning aims to minimize the gap between coal and resources traditionally used in the Brazilian energy matrix. In this scenario the processing of Brazilian coal by flotation appears as a promising alternative, having been successful in mineral systems containing fine particles This paper aims to study the overall process of flotation for a specific Brazilian coal. The material used in this study consists of fine coal that is usually discarded as waste and deposited in the tailings dam. The objective is to recover carbonaceous matter and reduce the ash and contaminants grade. The variables analyzed were the influence of size particle, solids concentration in the pulp, the concentration of surfactants and frothers to be used. The results showed that it is possible, from a feed with around 65% of ashes, to obtain products with approximately 35% ashes with mass recoveries about 40%. The types of collector reagent and foaming employees result in different concentrates. This study also presents a preliminary analysis of the effect of water recovery in concentration parameters."

Jan 1, 2014

By M. V. S. Cavalcante

The quality of iron ore pellets, represented in terms of parameters such as cold compressive strength (CCS) and Tumble Index (TI), has a strongly influence on the productivity and energy of reduction furnaces like the blast furnace and on the quality of hot metal or liquid iron. The main objective of pelletization operations is to produce iron ore pellets of desirable specifications and ensure high levels of plant productivity and energy efficiency. Advanced process control of an industrial iron ore pellet induration process using a soft sensor for pellet quality and fuzzy-logic based control algorithm is described in this paper. The pellet quality soft sensor consists of a rigorous mathematical model of the induration process and a statistical model for the pellet quality parameters. The mathematical model is based on the fundamental principles of heat and mass transfer between gases and pellets, kinetics of drying and condensation of moisture, combustion of coke, calcination of limestone, and melting and solidification of pellets. The predictions of wind-box temperature profiles are in close agreement with the measured profiles. The time-temperature profiles of the pellets during induration, along with raw material characteristics and induration process operating conditions, are used as inputs to the quality model to predict cold compressive strength and the Tumble Index. The predictions of the quality soft sensor along with the rules based on fuzzy-logic derived from simulation results and operator experience are then utilized to control the induration process to achieve precise control of the quality parameters and to optimize the induration process in terms of fuel efficiency and productivity. The mathematical model is also utilized as a soft sensor for temperature, moisture and composition profiles of pellets and gases. Results of implementation of this model-based control strategy on an industrial scale induration process will be presented. Keywords: iron ore, pelletization, simulation, process control, optimisation

Sep 1, 2012

By Z. G. Song, C. Y. Sun, X. R. Zhang, Y. Yu

In skarn type scheelite deposit, there are calcium minerals with floatability similar to scheelite, such as calcite, fluorite, etc., which are difficult to separate. Heating cleaning method developed by Petrov has been widely applied in processing rough concentrate of scheelite for nearly half a century, but there exists a general lack of full understanding of the interaction between floatation reagent and mineral particles surfaces. The mechanism on separation of scheelite and calcium minerals in heating cleaning process was investigated by mineral flotation experiments, XPS analysis, as well as solution chemistry and crystal chemistry calculations. The results showed that the sequence of minerals floatability using sodium oleate as collector and a large amount of sodium silicate as modifier in heating flotation test was scheelite > calcite > fluorite, which was the same as solution chemistry calculations based on Gibbs free energy vs. pH and also the same as Ca-X intensity order by crystal chemistry analysis. There are two sides about the mechanism of heating cleaning method: one is that the adsorbed collector on calcium minerals surface is desorbed more easily than scheelite, and the other is selective dissolution of calcium ions from the mineral surface because of Ca-X intensity difference in heating and stirring process.

Jan 1, 2014

By Brochot. Stephane, Manuel Gonzalez Fernandez

"HPGR (High-Pressure Grinding Rolls) is widely used today for grinding of various kinds of ores such as iron ore or base and precious metal ores. It can be used as first stage of grinding replacing tertiary crusher and SAG mill, but also as regrinding stage to enhance mineral liberation. In addition to better energy efficiency, the advantage of HPGR is to produce much more internal particle fractures allowing faster leaching as it has been demonstrated for some gold ores. This grinding mode of compression and fracture generation also promotes mineral liberation without overgrinding. Mineral processing modelling and simulation associated to detailed ore characterization constitute a powerful tool for plant design and optimization. The mathematical models of the units of operations (grinding and separation) have to reproduce the mineral deportment for which the mineral liberation plays a central role. The present paper is focused on the HPGR modelling with the objective of plant optimization or advanced design from pilot plant tests. The traditional approach of the population balance linked to the energy dissipation and the residence time distribution is generalized in association with a mineral liberation model. The effect of the specific HPGR breakage matrix and grinding function on the mineral liberation rate is discussed and compared to the tumbling mill. The implementation of this mathematical model into a plant simulation tool is illustrated by the example of the optimization of an iron ore concentrator."

Jan 1, 2014

By C. A. Perez

Estimation of rock composition in mineral plants is important to determine rock size and grindability which in turn may improve control of the grinding process. Variations in ore grindability and size distribution directly affects mills power consumption and throughput. Therefore, it is desirable to develop new tools to estimate rock lithological composition. In this paper, a new method for lithological classification based on machine vision is proposed. The method is based on a single video camera and employs information about texture using several different spatial scales. Texture information is extracted from rock images using Gabor filters that can be adjusted at different spatial scales and orientations. After feature extraction, rock images are classified using support-vector machine (SVM). The method was tested on a database containing sub-images of 64x43 pixels of five ore types as follows: massive sulphide (MS), disseminated sulphide (DS), net textured (NT), gabbro (G), and peridotite (P). These ore types were assigned to three grindability classes: soft (MS), medium (DS and NT) and hard (G and P). The database was divided in 2 subsets for training, cross validation, and for test. Classification accuracy is compared with previously published results on a dataset with three different classes of rocks according to their hardness. Results show that our proposed method reached significant improvements (between 13%-20%) in classification accuracy relative to previously published results. Keywords: rock classification, lithological classification, grindability estimation, Gabor feature extraction, texture features

Sep 1, 2012

By Silvia França, Hudson Couto

"In this paper, an alternative beneficiation process was developed to recover nickel minerals from low-grade weathered ores. The studied sample, 0.3% Ni grade, is essentially composed of nickel sulfides (pyrrhotite and pentlandite); magnetite and silicates (mostly talc and amphibolites) are the primary gangue minerals. The particle size distribution was controlled using a grinding operation to avoid producing an excess of fine particles by overgrinding. The sample underwent a grinding step for the fine degree of liberation. The slimes (-20 ?m) were removed via two desliming stages in hydrocyclones (diameters of 1.5" and 2"); the ground material, which was classified in a range of (-150+20) ?m, was processed by column flotation in three different stages: rougher flotation for magnesium silicates, rougher flotation for sulfides, and cleaner flotation for sulfides, using pilot flotation columns (2" and 6" in diameter and 20 ft high). The goal of using the preliminary magnesium silicate flotation step was to remove hydrophobic minerals (mostly talc) that would float naturally with the sulfides, which would decrease the Ni grade in the concentrate, as well as to reduce the MgO content because this compound is considered harmful in metallurgical processes when a grade greater than 9% is used. The final concentrate obtained in the cleaner flotation step reached up to 2% Ni and 7.0% MgO. The global and flotation recoveries in the process were approximately 30% and 60%, respectively, due to the losses of Ni during the desliming process. Despite this low global recovery, the adopted beneficiation process can be considered an interesting alternative to produce nickel concentrate from tailings or waste materials."

Jan 1, 2014

By X. M. Yu

A large amount of polluted sludge is produced by a nonferrous metal factory after treating waste water with lime/ferrous salt. The concentration of arsenic in the dried sludge is high to 5.84%, a toxicity test is taken on the sludge according to GB5085.3-2007 and the extraction content is 15.75mg/L, which surpasses the arsenic extraction standard [As]=5mg/L, the sludge is categorized as hazardous waste. If put outside without disposal, it would be very harmful to environments. Here we report an optimum protocol to extract arsenic; S2- alkaline liquor is utilized to treat the arsenic sludge. At 85?, 10L 7% S2- liquor is added into 1kg dried sludge and the resulting mixture is stirred for 120min at 250r/min, then separated by centrifugation and the compressed waste residue dried naturally. The average arsenic content is 1.40mg/L, lower than GB5085.3-2007 Standard and arsenic-free residue is consistent with GB18598-2001 Standard, which can be bury safely. The extracted arsenic is transferred into copper arsensite for use as addictive in copper electrolysis and the waste water can be recycle after calcium is removed.

Jan 1, 2014

By M. Saba

In cyanide leaching procedure, achieving an acceptable efficiency for silver and gold is very time-consuming, thus, enough studies have not been performed for optimization and modeling of this process. The kinetics of cyanide leaching includes two steps: first step comprises a sharp slope while the other has a slight increasing trend. In the present study, in order to reduce the time and cost, the cyanide leaching process of a sulfide silver/gold ore was optimized in the first period. The applied parameters and their ranges are: temperature 20-40 (°C); time 1-8 (hrs); cyanide concentration 1-2 (mole cyanide / mole Cu); the percentage of solid to liquid 1-2 (%) and pH 10-12. For design of experiments fractional factorial 2(5-1) was used. Also four center points were applied to increase the accuracy of the model. In addition, by analysis of variance (ANOVA) the most effective parameters were identified and the optimized condition was determined. A regression model was proposed to describe the effects of independent variables and their interacting role on silver recovery. Results showed that the model was linear for silver and nonlinear for gold. In the gold recovery process, the two important parameters are time and pH with the former being more effective. Due to the existence of cyanide ions in the medium, temperature and cyanide concentration have less influence in the gold recovery process. Solid to liquid ratio, in addition, comprises a slight negative impact on the procedure. This emphasizes the different kinetics of silver/ gold cyanide leaching. Finally, using the optimum condition the amount of silver and gold obtained were 61% and 67% in 8 hours, respectively. While in general conditions, the results were 37% and 54% in 24 hours, respectively. Keywords: cyanide leaching, refractory gold/silver ore, modeling, optimization

Sep 1, 2012

By G. Mucsi, F. Kristály, Á. Rácz, É. Gregus, K. Bohács

"Stirred media mills are widely used in the industry for fine grinding. Most of the applications work in wet mode, however dry grinding in stirred media mill comes forward more frequently nowadays. The present paper deals with the differences and similarities of the wet and dry grinding in stirred media mill from energetic and mechanochemical point of view as well. Grinding experiments in batch stirred media mill were carried out with different materials. During the experiments zeolite and kaolin were used as feed material. The grinding experiments were carried out at different stress energy and stress number values; the grinding work was measured during milling. After grinding X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), particles size analyzes by laser scattering were carried out on the ground materials. As a result of the systematic grinding and analytical measurements a comprehensive comparison was carried out on the wet and dry grinding and their usefulness for mechanical activation in stirred media mill. INTRODUCTION The natural zeolites are crystalline hydrated aluminosilicates of alkali and alkaline earth characterized by the structure that contains frameworks responsible for the high cation exchange capacity (CEC) and absorption capacity. The frameworks are interconnected by cavities and resided by cations variable in size, coordinated by water molecules. Since zeolite comprises SiO4 and AlO4 tetrahedra interlocked by oxygen atoms that are situated in the structural nodes, their characteristics differ due to the varieties in the structure-directing agents and Si/Al ratio (Colella and Wise, 2014; Malekian et al., 2011; Terzic et al., 2017). The most common natural zeolite occurring in high amount, of industrial importance and involved in milling and MA is the clinoptilolite, in the literature equivalent to “natural zeolite” designated for high clinoptilolite bearing volcanic tuffs. Its amount in the host rock must reach ~ 40 % by weight to obtain the CEC and adsorption desired in its applications. In the highest quality rock might reach 80-90 % by weight (Favvas et al., 2016), but most often is the 40-60 % by weight content, associated with smectites, improving the CEC and adsorption of the tuffaceous rock. The application of such natural zeolites is problematic in many cases due to high silica (quartz, cristobalite and volcanic glass) content and beneficiation (concentration and extraction of pure zeolite) are not feasible. Thus, mechanical activation is a possible way to alter the other than clinoptilolite minerals generating high specific surface area and functionalized particle surfaces to enhance adsorption, reaction or particle adhesion. The zeolites easy availability and the utilization cost-effectiveness have prompted the research on their physicochemical and structural properties (e.g. adsorptive and molecular-sieve activity, heat resistance, and microporous cage structure) and finding new options for their application (Kusuma et al., 2013; Musyoka et al., 2014; Rida et al., 2013; Terzic et al., 2015b). Apart from the presence of exchangeable framework cations which are crucial for the adsorption ability, and a certain degree of pozzolanic reactivity. The thermal stability of dehydrated phases is another important characteristic for use of the zeolite in composite materials that are exposed to high temperature. Thereby, the zeolites found a wide application possibility in the design of the construction composites (Albayrak et al., 2007; Najimi et al., 2012; Vejmelková et al., 2015), as well as for resolving of the environmental protection issues like wastewater refining or heavy metal elimination (Gómez-Hortigüela et al., 2014) even from contaminated groundwater using passive methods like permeable reactive barriers (Gombköto et al, 2016). The grinding treatment of zeolite is a common and frequently applied procedure, both on laboratory (Bohács et al. 2017, Faitli and Czél, 2014)"

Jan 1, 2018

By Kozlov Andrey, Matveeva Tamara

"The results of mineralogical and technological studies of platiniferous dunites from Svetloborsky zonal massif (Urals platinum belt) are presented and the basic typomorphic signs of productive mineral assemblages are substantiated. The characteristic features of platinum ore mineralization are revealed: a wide range of iron-platinum alloys, enrichment of ore-formed system by the elements Os, Ir, Rh and activity of the S and As in it, intrusion of Fe-Ni sulfides in platinum and its fusion with magnetite. More than 80% of PGM mineral grains has size less than 100 microns, that determines the possibility of significant losses of platinum in the process of gravity separation and the need for additional recovery processes for small and fine fractions of platinum tailings and sludge products. Summarized results of laboratory tests of small-volume sample processing of platiniferous dunites are presented and the processing flow sheet is developed and tested. The flow sheet incorporates several stages, including stage-wise grinding and gravity separation of ore using the centrifugal concentrator Knelson KS-MD for differently sized material and flotation treatment of tailing products using new classes of reagents for additional recovery of PGM fines."

Jan 1, 2014

By S. M. Bradshaw, R. Smith, J. H. van Vreden, C. A. Snyders

"The re-treatment of gold tailing heaps has shown to be a potentially significant revenue stream for both large and small scale gold companies. Limited access to capital and lack of skilled labour remain restrictive especially when dealing with a refractory ore and/or where limited amount of material are available. Alternative techniques such as low temperature pre-leaching options to unlock value are therefore in demand. Several low temperature pre-leaching experiments in acidic and alkaline solutions, followed by cyanidation were performed which ultimately led to the further investigation of a caustic pre-leaching step. It was found that the Au recovery from a refractory ore tailings heap could be significantly improved from ˜ 15 to 20% to greater than 60% with a simple atmospheric NaOH pre-leaching step. It was further considered, that since the NaOH pre-leach liberate the Au associated with refractory sulphide minerals, the overall process may benefit by the inclusion of a froth flotation step to separate refractory sulphides from the free milling ore. Froth flotation on weathered tailing heaps are, however, known to be difficult, ultimately resulting in poor recoveries. A process flow sheet, incorporating a caustic pre-leaching step and a process which includes flotation and caustic pre-leaching of the concentrate, are technically evaluated and ultimately compared to simple cyanide re-processing. INTRODUCTION South Africa consists of a large number of gold tailings dumps. Janse van Rensburg (2016) estimated that there was about 517 dumps in the Gauteng area, covering approximately 320 000 ha of surface area. Recovering value from the dumps has received a great deal of interest but can be problematic due to the dumps often being refractory, preg-robbing and weathered. High recovery of valuable metals (Au and Ag) are possible (Fleming and Brown, 2010) but would most likely require pressure oxidation and subsequent neutralisation which can be very capital intensive demanding a high skill set to operate and maintain. In addition, these flowsheets target high processing tonnages due to the economy of scales at the lower grade feed materials, further increasing the capital requirement."

Jan 1, 2018

By Ye Junjian

The feed ore is the concentrate of low intensity magnetic separation of pyrite tailings, containing TFe47.47%, S19.41% and SiOpyrrhotite. The exploratory tests showed that using a process of flotation followed by magnetic separation could respectively obtain a sulphur concentrate of S 31.08% with a recovery of 82.89%, and an iron concentrate of TFe 59.97% and S 9.52%with a recovery of 30.93%. The reason of iron concentrates with high sulphur grade was that the sulphur grade of flotation tailings was 7.03%. So enhanced flotation for pyrrhotite was investigated in this research. Results show that when the natural pH of ore pulp varied from 5.5 to 6.0, a reagent combination of FS, LH, and BJ displayed the optimum flotation performance for pyrrhotite. After comparisons made on different flotation processing, the previous flotation flow of ?one roughing, one cleaning, one scavenging system and middling reprocessing?, was found, among others, to have the best flotation effect, as the grade and recovery of sulphur concentrate were 31.08% and 82.89%, respectively, and sulphur content of the flotation tailings was 7.03%. The above results indicated it was difficult to raise further the effect of flotation desulphurization. The authors therefore suggested that oxidizing roast should be adopted following the magnetic process for the purpose of further desulphurization. Besides, flue gas containing SO2 8.25%. And the valuable minerals are magnetite and 2 generated from roasting could be reused for sulphuric acid production. Keywords: pyrrhotite, enhanced flotation, desulphurization

Sep 1, 2012

By H. Wotruba, L. Gronen, A. Hellmann, S. Sindern, J. Katzmarzyk

"This paper focuses on the beneficiation of the REE-Y-Nb-Zr complex ore from the ‘Khalzan Buregtei’ deposit, Mongolia. Pre-concentration based on mineralogical studies was investigated at the Unit of Mineral Processing (AMR) and the Institute of Applied Mineralogy and Economic Geology of RWTH Aachen University. In order to minimize the energy consumption in the most energy intensive grinding process a pre-concentration process using dry magnetic separation of particle sizes coarser than required for the liberation of the valuable ore minerals was designed. Dry magnetic separation in the particle size range of 63-250 µm is suitable as the pre-concentration method, due to the intergrowth of REE-Y-Nb-Zr bearing minerals with magnetic minerals determined by QEMSCAN© analysis. The results showed that a mass reduction of 45.3 wt.-% at high recoveries of REE, Y, Nb and Zr (90 wt.-% and higher) in the pre-concentration product was achieved at the beginning of the process chain. The improvement of process efficiency as shown in this study depends on the abundance and association of minerals affecting the magnetic properties (e.g. hematite) of the ores. Therefore, these mineralogical parameters are as important as grain size and ore grade for the geometallurgical evaluation of potential mining operations at ‘Khalzan Buregtei’.INTRODUCTION Polymetallic deposits containing other critical elements besides REE have the advantage of being robust to economic development and fluctuations of individual metal prices. (Gronen et al., 2016). These deposits can host economic grades of heavy and light REE, Y, Nb, Ta, Zr in complex mineralogical compositions. About 120 deposits of this type are known worldwide, including ‘Norra Kärr’ in Sweden, ‘Strange Lake’ in Canada and ‘Khalzan Buregtei’ in Mongolia which are not valued economically yet. (Salvi. & Williams-Jones, 2004.)"

Jan 1, 2018