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By D. B. Mazzinghy, D. C. Rocha, H. B. Miller

"The use of ball mills for fine grinding is an inefficient process and has contributed to the increasing popularity of vertical stirred grinding mills in the minerals industry. Over the last decade, the performance and energy efficiency of stirred milling technology has become a preferred alternative to ball mills for fine and regrinding operations. The difficulty encountered in fine grinding is the increased resistance to comminute small particles when compared to coarse particles. Therefore, increased energy inputs are then necessary to raise the number of stress events in a mill to contribute to the comminution of fine particles. This work discusses the effect of operating conditions on the amount of fines produced and torque readings in a screw type batch laboratory vertical stirred mill. A time-based population balance model (PBM) was used to empirically analyze the performance of a vertical mill and to calculate mill breakage parameters for the different operating conditions tested. The results indicate the possibility of applying population balance model to the vertical stirred mill to predict product size distribution with acceptable accuracy. The obtained breakage function shows that the main breakage mechanism in this vertical stirred mill is by attrition, and that the selection function changes with experimental conditions within the mill. Higher agitator velocities are also seen to promote an increase in the degree of attrition between grinding media hence particle selection and fines generation increase.INTRODUCTION Stirred milling technology has been firmly established in the last 20 years as superior to ball mills for fine and regrinding operations due to its superior energy efficiency (Jankovic, et al., 2006). Stirred mills are now commonly used in many sectors of the mining industry, though they have been used in other industries for many years (Stehr & Schwedes, 1983). This technology has proven to be more energy efficient with greater opportunities for future optimization in both fine and coarse grinding."

Jan 1, 2018

By V. V. Zakopaylo, M. V. Lukyantseva, V. A. Ignatkina, V. A. Bocharov, L. C. Khachatryan, D. M. Altynamanov, A. A. Kayumov, R. H. Sharipov

"This research was aimed to explain the reasons of low floatability of tennantite from refractory pyrite ores of non-ferrous metals and to create a reagent regime for selective increasing a recovery of copper sulfide minerals from arsenic-containing copper pyrite ore. ?opper-zinc ore of the Uzelga deposit has 89% of pyrite, some part as melnikovite; copper is assayed as 3.58% of tennantite and 0.25% of chalcopyrite; there is 2.19% sphalerite. Sulfide minerals are very finely disseminated. Tennantite is genetically related to primary copper sulfides. Graphene was identified on the surface of tennantite by a transmission electron microscopy (TEM) method. The recovery of tennantite was rose up by using the collector M-TF. M-TF is the mixture of diisobutylditiophosphate (DTF) and O-isopropyl-N-methyl (ethyl) (TC) in the certain ratio. M-TF change up a kinetic of copper sulfide flotation in a slightly alkaline medium, but pyrite has slowly floatability at this moment. A depressing effect of thiosulfate ions in a liquid phase of pulp flotation tennantite from pyrite ore has been established. A copper recovery up 14.2% (from 67.7 to 82.0%) into a copper concentrate level off copper grade of 18.65% (butkx) and 18.68% (M-TF) has been increased by the new technology with M-TF compared to a standard technology with butkx. A main copper recovery up to 50 % in an inter-cycle copper concentrate assaying 19-21% Cu in case of using M-TF was gotten. A zinc concentrate with recovery of 50% and a zinc assay of 41.76% by a standard flow sheet with butyl xanthate was obtained. A zinc recovery of 70.3% with a zinc grade of 44.17% by the M-TF technology was achieved.INTRODUCTION The pyrite copper-zinc ores of the Urals region are considered refractory. The distinctive features of these ores include a high content of pyrite (90-95%), the presence of arsenopyrite and arsenical pyrite, and the simultaneous presence of chalcopyrite, bornite, tennantite with the predominance of the latter (Andreasen et al.,2008;.Dobrotsvetov, 2009; Chanturiya et al. 2016). The flotation properties of tennantite differ from those of chalcopyrite (Xumeng Chen, Yongjun Peng, Dee Bradshaw. 2014), which is the reason why a comprehensive study was under taken of the flotation activity of tennantite and a process for its recovery was developed. The proposed agent treatment and flotation process make it possible to produce salable copper and zinc concentrates."

Jan 1, 2018

By I. L. Grigorova

As a result of the main processes of the limestone treatment ? sawing, buffing and polishing, a technological waste is usually obtained. These final tailings consist of a water suspension with highly variable solid phase content and granulometric composition. Since the waste is conducted to a tailing pool or another place, this leads to environment pollution. In this work the slurry waste generated during the limestone processing in a Bulgarian limestone manufacturing company was characterized. The chemical composition, particle size distribution, solid phase content, whiteness, yellowness, abrasion, specific surface and density were determined. The possibility of obtaining building/construction materials from limestone processing waste was studied in a laboratory scale. The technological tests included thickening, filtration and drying of waste products. Continuous operation laboratory thickener was used. Coagulant Accepta® 8302 (aluminum sulphate solution) and anionic flocculant Magnafloc® 155 were found to be the most effective in the sedimentation of the products. Filtration tests were performed using a laboratory pressure filter. Drying tests were carried out in laboratory facilities using the direct heating method. On the basis of the laboratory results a technology for limestone treatment waste was developed. A production line for building materials from limestone slurry was set up. As a result the manufacturing company has a possibility to use circulating water.

Jan 1, 2014

By N. Johnson, J. Quinteros

With the general trend across all commodities towards the treatment of lower grade ores, it is becoming increasingly important to develop efficient protocols for comprehensive mineralogical characterisation to allow the development of the most appropriate strategies for processing an ore. In the case of silver, there are more than 200 known silver bearing minerals which can make it challenging to identify them. Knowledge of the deportment of silver within an ore is one of the factors used to determine an appropriate processing strategy. Automated SEM-based tools are commonly used for mineralogical characterisation but the low-grade together with the large number of minerals that are potential hosts for silver means that often, complementary analytical tools must be used in order to properly account for the silver. The work presented in this paper is a demonstration of the approach that should be taken when identifying the deportment of silver in complex ores. Three complex, low-grade silver ores were characterised using the approach. The insights from the mineralogical characterisation were then used to inform the metallurgical testing that was undertaken. The results from the batch flotation testing clearly demonstrate the importance of understanding the mineralogy in order to select the most appropriate metallurgical processes.

Jan 1, 2014

By G. V. Sedelnikova

Biohydrometallurgical studies were performed on the sulfide gold-arsenic concentrate obtained in treatment of refractory ore from a deposit located in northern Russia. Gold is disseminated in sulfides-arsenopyrite, pyrite and antimonite (their content is 10.0%, 30.4% and 0.7%, respectively). Gold extraction is only 11.8% by cyanidation. Results are given for test bacterial oxidation of the concentrate in continuous mode at temp. = 28~32°C using mesophilic bacteria and at temp. = 32~38°C using the association including moderate thermophilic bacteria. The paper shows that the use of moderate thermophilic bacteria allows to speed up sulfide biooxidation and reduce its time to 96 hours compared to leaching at temp. = 28~32°C for 110~120 hours. The optimal range of pH = 1.5~2.0 of biooxidation process was determined where bacterial solutions are produced with the molar ratio Fe:As > 3 necessary for precipitation of hard-to-solve, environmentally safe arsenical precipitates. Electron microscopy showed that sulfide biooxidation results in liberation of disseminated gold with nanoparticle-level sizes. High sorptive activity of carbonaceous matter and other compounds of bacterial residues cause low gold extraction into cyanide solution ? 28.7%. 10% resin load makes it possible to extract 88.1% Au. Aeration of pulp in calcareous medium enhances extraction to 95.7% and decreases cyanide consumption from 17kg/t to 8 kg/t.

Jan 1, 2014

By Azin Zangooi, Cesar Gomez, James Finch

Frother concentration is a variable which significantly affects the flotation performance by decreasing bubble size and helping froth stabilization. Variations in frother concentration, which mostly go unnoticed in industrial operations, may affect these functions. Some factors that can cause variations include the fact that frothers are normally dosed based on feed tonnage and not solution concentration, unstable frother delivery, incomplete dissolution for low solubility frothers, addition of frother-free wash water, remnant frother in recycle waters and frother partitioning to the froth. A colorimetric technique developed for determining frother concentration on site makes it possible to detect the occurrence of these problems and to establish their magnitude, allowing conditions to be adjusted to reduce frother concentration variations. By sampling and analysis, frother distribution throughout a circuit can be established, referred to as ‘frother distribution mapping’. Experiences at several concentrators processing sulphide ores are used to illustrate time restrictions for sample analysis, and to demonstrate temporal and spatial frother concentration changes as a consequence of variations in the grinding stage, recycled waters containing frother, and frother partitioning.

Jan 1, 2014

By V. F. Petrov, E. P. Olberg, S. V. Petrov

"The study was carried out using process solutions produced during cyanidation of gold-bearing concentrates from a gold-processing plant. It was found that the water contained a significant portion of thiocyanate (7910.0 mg/L), cyanide was virtually not present. The metals occurred primarily as iron (355.0 mg/L) in the form of ferrocyanide. Cyanide recovery was conducted using an ozone treatment process with reactors developed by the Environmental Department of Irgiredmet. The process design ensured complete utilization (100%) of O3, thus equipment operation safety increased.The recovery of free cyanide from thiocyanate was 76.6%, which corresponded to 5.12 kg of NaCN (100%) per 1 m3 of solution. Recovered NaCN can be used for recycling in hydrometallurgical processes.The operating costs estimation showed that the production cost of a tonne of recovered cyanide was US$1288.7, considering the prices of energy and commercial sodium cyanide in Russia in 2017, i.e. recovered cyanide is cheaper than commercial cyanide by 55.8%.INTRODUCTION Depletion of oxidized gold-bearing ores readily amenable to cyanidation has shifted focus to large-scale processing of primary ores with high sulphide content. Primary ores processing flow sheets involve gravitational and/or flotation concentration with subsequent treatment of produced gold-bearing concentrates. Typically, concentrates reporting to cyanidation contain considerable amounts of sulphur that can interact with CN- and further formation of SCN-. The use of refractory gold liberation methods (bacterial liberation, ultra-fine grinding) provides activation of this side reaction up to complete consumption of free cyanide in a short period. This makes water recycling unviable and impractical.The interaction of the sulphur content in concentrates and cyanide contributes substantially to consumption of NaCN required for efficient gold recovery. Inappropriate consumption of the main reagent achieves dozens of kilogram per tonne of material to cyanidation, and reaches approximately 100% when gold is recovered from activated sulphide-containing products (e.g. by ultra-fine grinding)."

Jan 1, 2018

By J. W. Ahn

Calcined calcium oxide from limestone is hydrated to manufacture calcium hydroxide, and then precipitated calcium carbonate is synthesized from calcium hydroxide. Precipitated calcium carbonate of various morphologies is obtained by controlled conditions of each step and characteristics of limestone, calcium oxide and calcium hydroxide. Especially characteristics of calcium hydroxide have the most influence on morphology of precipitated calcium carbonate character. In this study, therefore, it is investigated the specific surface area of calcium hydroxide and morphology of precipitated calcium carbonate according to hydration temperature. Calcium hydroxide hydrated at high initial temperature has larger particle size than that hydrated at low initial temperature. And formation yield of aragonite precipitated calcium carbonate has improved by using calcium hydroxide had larger particle size (hydrated at high initial temperature).

Jan 1, 2014

By Wantae Kim, Hoon Lee, Kwanho Kim, Sangbae Kim

Mechanochemical activation of starting minerals and their effect on the solid-phase synthesis and properties of ceramics with lower thermal expansion coefficient was examined. The mineral mixture, pyrophyllite-gibbsite-lithium carbonate, was prepared for the synthesis of ?-eucryptite (Li2O•Al2O3•2SiO2). Dry grinding using a planetary ball mill promoted the amorphization of the starting mixtures. XRD and FT-IR results showed that the crystallization of the target materials occurred from the ground mixtures by calcination. The crystallization of them increased with increment of grinding time and calcination temperature. In the synthesis, the trace of undesired phases such as quartz and cristobalite once formed during calcination at the temperature range from 750 to 850 °C almost disappeared and monophase ?-eucryptite was formed in the ground mixture at 950 °C. The lowest liner thermal expansion coefficient (TEC) of ?-eucryptite prepared was -2.5x10-6•°C-1. The thermal expansion behavior characteristics of the calcined

Jan 1, 2014

By John A. Herbst

Professor A.M. Gaudin and his students at MIT were dedicated to understanding the fundamentals of mineral processing and as a consequence were constantly searching for better quantatative descriptions of size reduction, liberation and mineral separations. I have had the good fortune of meeting Professor Gaudin and working with many the modeling pioneers who followed him. I have observed first hand the refinement of mineral processing models as they increased in realisticness moving up the steps of the pyramid (see figure below) from pure empiricism to the current pinacle of physics based models. During this journey our industry benefited significanbtly as model prediction errors were reduced from ± 20% to ± 1%. Unit operation and plant simulations improved in accuracy and speed of calculations.

Sep 1, 2012

By Wang Xu, Tao Dongping, Zhang Jie, Tao Youjun

Based on the principle of fly ash triboelectrification, the mineral electrical index and testing method are introduced. The electric differences of various mineral components of fly ash are discussed in view of the results of chemical and mineral composition analysis of the fly ash sample acquired from the Xin-wen power plant. The dielectric constant and charge-mass ratio of carbon and ash in the fly ash are determined. The data were then used along with the rotary triboelectrostatic separator (RTS) testing results to investigate the charging characteristic of fly ash particles in different sizes. The results show that the dielectric constant of fly ash with different particle size decreased with the decrease in particle size, which led to a poor electrical conductivity. Thus particle size has an important effect on conductivity. The charges of carbon and ash particles increased with decreasing particle size. The charge-mass ratio of carbon and ash particles of the same size increased with decreasing particle size. This indicates that finer particle size is more favorable for triboelectrification separation from the charging efficiency point of view. The rotary triboelectrostatic fly ash separation tests show that the best decarbonization performance was achieved with particles in the size range of 0.038-0.074mm with which the decarbonization rate and efficiency index reached 38.93% and 120.83% spectively.

Jan 1, 2014

By Daniel Saramak

"Issues concerning effectiveness of the high-pressure comminution process in technological circuits of copper ore treatment were presented in the paper. Crushing processes taking place in high-pressure grinding rolls devices (HPGR) are currently one of the most efficient methods of hard ore size reduction in terms of the energy consumption. The HPGR products are characterized by a fine particle size and the micro-cracks formation in individual particles, which appear in downstream grinding processes, decreasing their energy consumption. The purpose of this paper was to analyse the effectiveness of a ball mill grinding process depending on the changeable conditions of run for the HPGR crushing process. The research programme carried out included crushing tests in the laboratory scale HPGR device at various settings of the operating pressure volume and selected qualitative properties of the feed material (i.e. particle size distribution). Particle size distribution analyses of all HPGR products were performed and in the next stage the material was a feed to the ball mill grinding process. Grinding process kinetics were investigated through the determination of mass recoveries of individual particle size fractions after defined grinding time intervals. The models, defining the grinding process effectiveness as a function of changeable conditions of HPGR process run, were determined on the basis of obtained results. Based on these models the optimal grinding time in a ball mill was specified which is, in turn, the basis for optimization of operation of the technological comminution circuits for a given material type. The obtained results proved that the application of HPGR devices in a given copper ore comminution circuit may improve the effectiveness of the downstream grinding process which leads to improvement of the entire circuit work efficiency through decreasing the process energy consumption and enhancing product size reduction."

Jan 1, 2014

The introduction and subsequent ascendancy of autogenous and semi-autogenous milling for comminution circuits has undoubtedly lead to many economic advantages. From a process viewpoint, however, at least one downside has been the sensitivity of these machines to process input variations. Foremost among these is ore competence, though feed size comes a close second. This sensitivity is due to the reliance of ag/sag mills on the feed ore for their grinding media competence and size. Autogenous (ag) mills are the most sensitive in this respect with semi-autogenous (sag) mills being increasingly less so as the ball charge is increased. Increasingly designers and operators are recognising the importance of feed size and the benefits of manipulating it to improve performance. This has been achieved by installing additional crushing/screening capacity ahead of the ag/sag, better operation of the primary crusher, better control of segregation cased by stockpiles and bins and by changing blast design/practices to modify the ROM size distribution. This paper describes the influence of feed size distribution on ag/sag mill performance with reference to a range of plant data. It particularly concentrates on how changing blasting practice to modify ag/sag feed size can have a considerable overall benefit.

Jan 1, 2003

By L. Y. Zhang

The metallic sulphides in Jinchuan Mine are relative friable and the gangue minerals suffer of wide secondary change, the overgrinding of metallic sulphides and sliming of gangue minerals are the main cause that makes the mineral separation indexes difficult to improve. So changing the process of grinding, and classification, and optimizing the particle size distribution of grinding product is the key improving the separation performance of Jinchuan nickel and copper ore.

Jan 1, 2014

By Georg Unland, Thomas Wegner

"Different types of impact crushers use the physical effect of impact to crush rocks. The rocks can vary from soft to hard and from ductile to brittle but they should never be abrasive. Since the principles of impact crushing of larger rocks are hardly investigated these crushers are still sized rather by empirical than by scientific approaches.In order to investigate the principles of comminution by impact of large rocks a test rotor was developed and rocks of different dimensions were tested. The integrated measuring devices of the rotor enable the recording of impact forces and of absorbed impact energy with high resolution during the contact time.Since impact crushers stress the rock particles with a defined velocity the main crushing properties are gained as a function of the applied velocity and the particle size of the rock: likelihood of breakage, contact time, maximum crushing force, mass specific crushing work, surface related crushing ratio and crushed fragment shape distribution."

Jan 1, 2003

By Bent Babel, Martin Rudolph

"The characterization of reagent-mineral interactions in flotation systems of finely intergrown ores holds difficult challenges for the applicability of standard techniques like Hallimond tube tests and contact angle experiments or renders them impossible due to a lack of sufficient samples in terms of quality and quantity. This disadvantage may not apply to more sophisticated techniques, but these often do not work in an aqueous environment. We present the utilization of an atomic force microscope with a hydrophobic colloidal probe to characterize the wettabilities of individual mineral domains of an ore sample, while additional spectral information is gathered by Raman spectroscopy. The exemplary ore sample investigated is mainly containing cassiterite and quartz, therefore the reference measurements like Hallimond tube tests and contact angle experiments were carried out with this binary system as a comparison. The focus of the study lies in the correlation of data gathered by the atomic force microscope and the Raman spectrometer with data from standard techniques. Finally, the applicability of the colloidal probe atomic force microcopy technique for reagent-mineral investigations is critically evaluated.INTRODUCTIONThe focus of this paper is the application of colloidal probe atomic force microscopy (CP-AFM) for theinvestigation of reagent-mineral interactions on a binary system of cassiterite and quartz. This and similar concepts using hydrophobic AFM probes have been applied by multiple authors (Rudolph and Peuker, 2014a; Rudolph and Peuker, 2014b; Wada et al., 2017; Xie et al., 2017). The hydrophobic interaction is the main interacting mechanism for the hydrophobic colloidal probe with hydrophobic sample surfaces and the long range attractive component has been accounted to nanobubbles on the interacting surfaces (Yakubov et al., 2000). More detailed information on nanobubbles are available in two reviews compiled by Attard and Hampton (Attard, 2003; Hampton and Nguyen, 2010). This paper is based on the work by Rudolph and Peuker comparing different AFM based measuring concepts, additionally gathering data with Raman spectroscopy and correlating results of microflotation and CPAFM measurements (Rudolph and Peuker, 2014a; Rudolph and Peuker, 2014b)."

Jan 1, 2018

By J. M. Ortiz, J. Haas, W. Kracht, G. Pamparana

This work explores the effect of ore hardness variability on the design of a solar photovoltaic system with battery storage and grid backup, to operate a semi-autogenous grinding mill (SAG). First, a case of two synthetic ore populations was studied, without any consideration of spatial distribution. The mean and variance of the ore hardness (measured in specific energy consumption, SEC) of both populations were subjected to a sensitivity analysis. The operation was evaluated with one and two stockpiles. The latter allows classifying according to ore hardness as a way to adapt the SAG energy consumption to the solar cycle. The results show that using two stockpiles allows achieving a larger autonomy (i.e. less energy imports) at lower total costs, especially when the difference of mean hardness between the two populations is large. The difference in variance (between the two populations) has a smaller impact on the design recommendations. Second, a case study was performed considering the spatial distribution of geometallurgical units. Two cases were considered: (a) brownfield, when there is historical information of the actual variability of the ore hardness; and (b) greenfield, when the system design relies mainly on geometallurgical modeling. Brownfield and greenfield planning result in similar sizing recommendations of the solar power plant, if precise drill cores are available. In this case, geometallurgical modeling is an effective tool for forecasting the energy demand necessary for designing the power plant.

Jan 1, 2018

By Urs Peuker, Thomas Mütze, Thomas Leißner, Inga Osbahr

"Mining in the Ore Mountains (Germany) has taken place for hundreds of years and in several stages. Each stage produced its typical tailing. According to the former state of the art of the processing much valuables could not be extracted. This was caused by complex interlocking of the minerals, low grades, or by upgrading processes not sensitive enough for small particle sizes. Thus the processing of these fractions was uneconomically. Modern technical possibilities and rising metal prices bring these tailings disposals into focus for the processing of strategic metals. Mining disposals can be classified in heaps with coarse, low grade rock, which did not undergo a processing, slags and fly ash from smelting, and tailing disposals from mineral processing. The latter is under investigation to integrate them into a geographic information system. The mineral processing of the material will be part of the database besides information about geographic location, structure, amount of valuables, and details of ownership of the heap. The tailings disposals are composed of coarse, low grade, interlocked particles from density separation processes, medium size particles, which are tailings from flotation, and fines with liberated valuables, which did not undergo flotation. Therefore mineral processing of these disposals comprises the separation of liberated gangue by classification, beneficiation of locked valuables with density separation, liberation of valuables by grinding, and beneficiation of liberated valuables with flotation. The presented work shows the results concerning the composition of one exemplary heap and results of the classification as well as of the preconcentration tests achieved with material from this heap."

Jan 1, 2014

By Gabriel Aguilera, Juan Arismendy

"As a separator machine, the hydrocyclone is one of the most commonly used equipment in different types of industries and particularly in mineral processing, hydrodynamic behavior allows efficient separation, but developing tests to optimize experimental equipment is expensive, therefore Computational Fluid dynamics (CFD) becomes a useful tool for optimizing the geometrical and operational parameters, and allows to analyze and understand the dynamics within the equipment. In the research was developed to simulate of 40 mm hydrocyclone where turbulence model was used Large Eddy Simulation (LES) for the continuous phase, for the generation of the air core and for the interaction of particles at low concentrations was implemented (mixture model), after the simulation was completed validation and comparation was done between simulation values and experimental."

Jan 1, 2014

By l. Bokányi, T. Varga

"The recycling of waste car tyres is a very important environmental task. The waste tyres usually are re-used or recycled by thermal processes like pyrolysis, gasification or incineration. The main problem associated with these processes is the sulphur content of waste tyres originated from the vulcanisation process, which pollutes the environment and the valuable products (i.e. pyrolysis oil) as well. In our research the desulphurisation of waste, mechanically prepared tyre sample was systematically investigated by the biosolubilisation with Acidithiobacillus thiooxidans, strain Karitas. Parallel, the experiments with sterile 9K nutrient medium were also carried out. It was found that the vulcanisation sulphur can be solubilised due to both the bio- and the chemical leaching, although the bioleaching is more effective. The solubilised vulcanisation sulphur then forms precipitates. The precipitates are forming in the bulk solution, as well as on the surface of rubber particles. The origin of the precipitates was investigated using XRD and scanning microscopy with micro probe. The origin of the precipitates is different: while in the process of the vulcanisation sulphur solubilisation with 9K medium the jarosite (KFe3+3(SO4)2(OH)6) forms, the course of the biosolubilisation with Acidithiobacillus ferrooxidans Karitas is accompanied by the formation of the jarosite and the halotrichite (FeAl2(SO4)4 · 22H2O) as well. The formation of the latter is the biomineralisation. The mechanisms of the bio- and chemical solubilisations are rather different as it was found and experimentally proved by several tests, and depends on the retention time of the solubilisation. Special efforts were done to elaborate the proper separation of the precipitates from rubber particles. Combination of intense dynamic stirring and recycling flotation process to remove the precipitates was applied for this purpose. The surface properties of synthetic jarosite were revealed using zeta-potential measurements at different pH and in presence of collectors. The parameters of the flotation were chosen based on the revealed surface properties of the precipitates. Finally, the sulphur recovery of the recycled rubber was achieved as low as <0.5%, sulphur content of it 0.17%, 12-times lower than that of the waste tyre sample after mechanical preparation."

Jan 1, 2018