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By D. Szyszka

During passing gas bubbles through mineral suspensions, some mechanical carryover of fine particles to the froth layer always takes place. The entrainment of mineral particles is influenced by many parameters, mostly by the particle size and the concentration of the frother. The paper deals with influence of selected frothers (methylisobutylcarbinol (MIBC), a-terpineol, and hexadecane tricosaethyleneglycol ether (C16E23)), common laboratory flotation frothers, on the mechanical car-ryover of quartz, a typical gangue mineral component of ores. Entrainment tests were carried out in a laboratory Mechanobr flotation machine with quartz particles suspended in aqueous frother solu-tions. The mechanical recovery of quartz in the presence frother was increasing with time and reached plateau after about 20 minutes of flotation. The plateau level of quartz recovery depended on the frother concentration. Initially an increase of the plateau with frother concentration was observed until the plateau reached the highest level called the maximum recovery emax. The emax can be used as a parameter to characterize the ability of frothers to entrainment. In the studied quartz-frother flotation system the maximum entrainment was 32%, 50% and 80% for methylisobu-tylcarbinol (MIBC), a-terpineol, and monohexadecane tricosaethylene glycol ether (C16E23), re-spectively. A comparison of the maximum entrainment factor emax with other, known from literature, indices such as bubble critical coalescence concentration (CCC), dynamic foamability index (DFI), Jw, e =25%revealed, except DFI, their similarity.

Jan 1, 2014

By Y. Y. Zhou

This paper introduces the application of CRIMM high-gradient magnetic separator in refinement of feldspar powders as well as the supporting technical outfits needed by the refining process with the high-gradient magnetic separator as main equipment. It could reduce the content of Fe2O3 to 0.03% with a deferrization rate of 85.88% from the feldspar raw ore containing 0.17% Fe2O3by using the above refining technology, producing an ultrapure feldspar product.

Jan 1, 2014

By Carlos Pereira, Fábio de São José, Francielle Nogueira

Votorantim Metals Corporation is one of the leader companies in the extraction of zinc in Brazil. One of its mines, located in the city of Vazante - MG, was composed by zinc silicate ores, but recent studies have indicated a change in mineralization type with arise of zinc sulphide’s ore bodies with disseminations of galena (PbS) and silver. The liberation size between sphalerite and galena in this ore occurs in very fine granulometry (approximately 18µm), fact that has negatively influenced into the flotation process. Aiming to reduce this problem, studies about the use of dispersing in the flotation process have started. Thus, this study investigated the action of different reagents dispersing on the stability of the suspensions. The tests were carried out with samples of mineral galena and sphalerite using four types of dispersing within two different dosages and two pH. The reagents tested were sodium hexametaphosphate, sodium silicate, carboxymethiylcellulose, and sodium polyacrylate. The results of the dispersion tests were analysed in relation to dispersion index. The tests with hexametaphosphate showed high dispersion for both galena and sphalerite. The sodium polyacrylate and arboxymethiylcellulose showed a high dispersion index for galena and a low index for sphalerite implying that reagent can be used in the concentration process of galena.

Jan 1, 2014

By F. Xie

Low gold and silver leaching kinetics has been commonly observed in traditional gold-silver cyanidation process, especially in those heap-leaching operations. The reactivity and availability of oxidant was believed to be the critical limitation for gold and silver dissolution. The occurrence of silver sulfide such as acanthite (Ag2S) in the ore may also result in low overall silver extraction. Leaching of gold and silver sulfide in the ferricyanide-cyanide solution has been investigated through rotating disc tests and the assistant effect of ferricyanide on increasing the dissolution rate of gold and silver was noticed. The potential use of ferricyanide as an auxiliary oxidant in gold/silver cyanidation process was proposed based on the results of leaching of gold-silver ores.

Jan 1, 2014

By M. Evertsson, E. Hulthén

"In aggregate production and mining the operators are responsible for controlling and monitoring the process to maintain high plant throughput and safe operation. Operators have to make different decisions to control the process due to changed demand on the operation from both management and conditions of the process. The quality of the response and the time it takes for an operator to respond to altered demand relies on what information is available and the experience of the operator. In this work a dynamic simulation platform has been developed to be used for operator training. Models for representing production units and process control for plant simulations have been developed and implemented in MATLAB/SIMULINK to simulate time-dependent plant behavior. Stochastic and scheduled events are included using the discrete events simulation toolbox SimEvents. The human-machine interface was developed using the human-machine interface software ICONICS. The operators’ cognitive process, in interpreting the plants semantic, has been studied by observations and with informal interviews with operators. This was done to get information about the daily operation and the problems that occur in the process. By interacting with operators that experience different physical interactions with the process; more qualitative e-learning software for supporting operator training in a dynamic operator environment could be developed. The quality of the operator training environment was evaluated with a usability study that was performed with operators and others within the production."

Jan 1, 2014

By J. Jávor

The response of the air/water interfaces to deformation in presence of surfactants is affected by the adsorption/desorption rate, re-orientation and exchange rate of surfactant. These surface properties can be observed using equilibrium and dynamic surface tension and surface elasticity measurements. However, the effect of these parameters on bubble size in dynamic conditions has not been studied due to the difficulty in capturing freshly formed bubbles in dynamic conditions. The paper presents a new experimental set-up designed and built at the Aalto University, called Shear Force Observation Chamber(SOC). The setupallows the monitoring and analysisof freshly formed air/liquid interfaces in dynamic conditions and facilitates the study of the effect of dynamic surface tension and surface elasticityon freshly formed air bubblesin presence of surfactants. The method helps to establish correlation between bubble size and dynamic interfacial properties and bubble-bubble interaction in turbulent flow. Dowfroth 200, Nasfroth 240 and Dowfroth 250 commercial flotation frothers were tested in this study. The results show a marked difference between results obtained in dynamic conditions compared to the static conditions. The results are presented and the reasons and implication to flotation modelling are discussed in the paper. Keywords: shear force observation chamber, flotation frothers, flotation bubbles, critical coalescence concentration

Sep 1, 2012

By Douglas Fuerstenau

"Comminution not only is the major energy cost in mineral processing but it also can limit the grade of ores that can economically be processed. Rittinger first postulated that the energy for comminution is proportional to the new surface produced. Because most of the strain energy needed to initiate and propagate cracks in particles cannot be recovered, researchers reported woefully low comminution efficiencies. Recognizing this, Schoenert proposed that the baseline for assessing comminution efficiency should be the mechanical energy needed to break single particles. After extensive single-particle studies, Schoenert turned to comminuting beds of particle in piston dies. Finding particle-bed comminution to be energy efficient, he had the brilliant conception of making the process continuous, namely his invention of the choke-fed high-pressure roll mill (HPGR). Practical comminution involves masses of particles, which can lead to energy efficiencies far less than that of single-particle breakage. A three-way classification of grinding modes in terms of the mobility of the particle mass provides the necessary insight into the low efficiency of different comminution machines: namely, single-particle breakage, confined particle-bed grinding (HPGR), and loose-bed grinding (ball mill). Examples are given for determining and comparing comminution efficiencies. The size distribution of comminuted products become self-similar, and a single parameter, the median size, can be used to quantify the extent of comminution. The reduction ratio, expressed in terms of the mean size of the feed and product, varies linearly with expended energy and the slope of such plots is a measure of the grindability of the mineral. This approach clearly gives the order of energy efficiency as single-particle > particle-bed > loose-bed comminution. HPGRs are more efficient at low reduction ratios but lose that advantage at higher reduction ratios. Extensive hybrid grinding experiments carried out with our instrumented ball mill and HPGR showed significant energy savings by first comminuting the material in the HPGR and followed by the ball mill. At Cerro Verde an industrial-scale hybrid HPGR/ball mill system is reported to have a 13 percent energy savings over a SAG mill/ball mill system."

Jan 1, 2014

By Luis Bergh, Francisco Díaz, Isabel Panire, Juan Yianatos, Luis Vinnett

"In this paper, industrial data of residence time distribution (RTD) in mechanical flotation cells is presented, which were measured in several plants using the radioactive tracer technique. Results include mechanical flotation cells of 100 - 300 m3, which were operated with effective residence times from 2 to 7 min. Tests were developed in forced air and self-aerated cells for liquid and solids (non-floatable) per size classes. Different RTD model structures including perfect mixer, Large and Small Tanks in Series (LSTS) and by-pass flow plus perfect mixer were evaluated and compared for single cells. The actual mixing regime was related to the effective residence times and cell designs based on the model fitting. By-pass flow percentages were typically lower than 10%, therefore the perfect mixer model plus a dead time was a suitable model structure in most cases. On the other hand, the arrangement of cells in series was effective in reducing the bypass flow observed in single cells (by-pass flow percentage greater than 5%). In addition, the N perfectly mixed reactor in series model was used to represent the mixing regime along flotation banks, which were operated with mean residence times in the range of 18 - 53 min. Results showed that N tanks in series plus dead time were closer to the actual values in most cases."

Jan 1, 2014

By Markus A. Reuter, Bernardete Castro, Antoinette van Schaik, Han Remmerswaal

"INTRODUCTIONThis paper describes the inseparable relation between product design, liberation, and metallurgical recovery in the optimisation of the recycling of passenger vehicles. This is illustrated by the use of an optimisation model that uses among others a material combination matrix based on metallurgical process data, which depicts the consequences of the quality of intermediate recycling products on the metallurgical material recovery and final alloy metal quality. Various simulations will illustrate the effect of changes in product design and hence liberation on the recycling of end-of-life vehicles. Although this paper focuses on cars, the discussion is equally valid for any end-of-life product. Calibration of the model will be discussed with reference to experiments carried out in order to study the optimal recovery of aluminium applications used in passenger vehicles.OPTIMISATION MODEL FOR LINKING DESIGN TO RECYCLINGImproving the efficiency of the material cycle of the car is essential to ensure a sustainable development of our society as well as e.g. to comply with the recycling targets imposed by EU legislation. In the design of the car various materials are combined and connected in many different ways, making up the complex 'mineralogy' of the car and its components, which is changing rapidly and continuously over time. The liberation of materials during shredding plays an important role in the composition (and quality) of the intermediate recycling streams. In order to include the influence of product design (mineralogy), liberation, and particle composition (quality of the intermediate recycling streams) in the optimisation of the recycling of end-of-life vehicles, a systems engineering tool for optimisation of the recycling of end-of-life vehicles was developed, including a liberation model. The optimisation model predicts the recovery rate as a function of product design (in this case a car), liberation, efficiency of the different process steps, economy and legislation based on a developed recycling flow sheet for end-of-life vehicles. Optimisation can only be achieved through the combination of the knowledge areas of product design, shredding, mechanical separation technology linked to pyro- and hydrometallurgy, composing a complex interconnected network of unit operations."

Jan 1, 2003

By Markus A. Reuter, Jacques J. Eksteen

"The modelling of bath type furnaces tends to be either fundamental in nature or total empirical ""black box models"". While models of the first kind are robust, they tend to lack accuracy, in cases where they are to be used for process control, and may take an overly long in development time. On the other hand, black box models tend to lack robustness of prediction for all circumstances and tend to be limited to interpolate based on historical data. While this may very often provide short-term accuracy, the models may have problems with stability in the long term. Moreover, the model structure may not reflect any of the fundamental properties of the system and remains opaque to fundamental analysis. The aim of the model development is in obtaining a model that have robustness, high accuracy, a short development time and which is adaptive to a changing environment. The models are specifically developed for on-line decision support or control of furnaces. The modelling approach is evaluated for a chromite bath smelting furnace. The role of systems analysis, mass balance smoothing, thermodynamic analysis are integrated into one generic algorithm for bath type furnaces. Not only are fundamental process relationships such the mass and energy balances satisfied through a scientific method of data reconciliation; the proposed modelling approach allows adaptive prediction, the first step towards predictive control or metallurgical decision support.It is shown that neither an ARMAX model only, nor a purely equilibrium model only, could predict the dynamics of the process very well. However, a combination of the two approaches more than doubled the accuracy as measured by the R2. It was noted for carbon dissolved in the alloy, that the improvement in R2 in using a hybrid modelling approach was more than the sum of the R2 of the individual traditional approaches. Similar improvements in modelling performance were noted for all other species.It shows further that process dynamics may totally overshadow the effect of thermochemical equilibrium (even when the thermochemical equilibrium prediction includes the recycled alloy and slag heels as additional feeds). The exclusion of process dynamics therefore leads to erroneous results."

Jan 1, 2003

By Arkady Senchenko

The application of centrifugal separation methods with the use of gravity concentrators has been assigned high priority while gold-containing minerals processing. The separation proceeds under centrifugal force resulted from the rotor spinning and wash water flow in the concentrators. The high specific gravity particles are retained at the trapping surface of the cone, and the low specific gravity particles are brought in the tailings. The centrifugal field in such concentrators (Knelson, Falcon) is generated by the rotating cone provoking the swirling of the free fed slurry flow. The author investigated the regularities of the separation process in the centrifugal gravity concentrator where a two-phase flow of the separated mineral media is under the pulsed pressure of the fluidization water and air. As a result of the study the possibility of the deeper penetration of the fine heavy fraction into the cone rings, providing the fluctuation of the fluidization water or air flow, was theoretically argued and experimentally proved. This allows the increase of the separation performance at low pulsation costs. The developed mathematical models are in close conformity with the actual process of interest and they enable the prediction of the heavy phase behavior at the isolated process stages in the concentrator. Keywords: gold, centrifugal gravity concentrator, containing, specific gravity, cone ring, pulsation, cost, fluidization water, Knelson centrifugal separator

Sep 1, 2012

By Ming’an Wei, Chuanyao Sun, Zhenguo Song, Zengwen Dou, Yangge Zhu

"The effects of pH value and dissolved oxygen(DO) in the pulp to the Eh and flotation recovery of pyrite were investigated using potential online detection system. The effects of DO on the Eh and flotation recovery were tested which DO changed from 0.5mg/L to 19.5mg/L in six different pH buffer flotation systems (pH: 4.00, 5.62, 6.86, 9.18, 10.01 and 10.96 respectively). Results of potential detected online demonstrated that the pyrite electrode has nearly the same response to potential as with platinum electrode for the FeS2-xanthate-H2O flotation system under the study conditions. Pulp potential and recovery of pyrite were remarkably influenced by pH, both of them decreased with the increasing of pH and, especially, sharp decreased after pH above 9. As the concentration of DO was increased, the Eh was also increased in all the six different buffer solution, while the flotation recovery was decreased. And the amplitude of variation for Eh was not obvious in acidic and neutral solutions, but on the contrary, the change for flotation recovery was remarkable in neutral and alkaline conditions. This may indicate that the flotation of pyrite will be deteriorated in alkaline and high DO concentration conditions."

Jan 1, 2014

By C. Suazo, O. Alruiz, A. Hofmann, I. Fernandez, W. Kracht, N. Mora

"Compañía Minera Dona Inés de Collahuasi, CMDIC, has developed a methodology that allows estimating economic benefit taking into account the variability of the ore characteristics (geometallurgical models). Currently, the grinding model allows predicting the treatment capacity, specific power and balls consumption for short, mid and long term planning. An alternative impact test to estimate SAG grinding parameters is presented in order to bring the geometallurgical model from mid and long term to short term planning. The impact test uses either the production bench or geological drill holes. This allows Geologists increasing the density of grinding parameters within the block model improving the geostatistical estimation of the rest of the blocks. The test requires a small amount of sample to obtain the requires grinding parameters for the grinding model in comparison to the well known grinding test and also, it can be performed easily and quickly by the geology team of a mining company. The alternative grinding test is presented in this article. The grinding model using this short grinding test has been successfully used in mining planning and the accuracy of the model is demonstrated using monthly average instantaneous throughput from January 2013 to March 2014, showing an average relative error of 5% and an R2 value of 0.9. Also, 111 individual variability samples were divided into two each, in order to compare the estimated grinding parameters based on this alternative test to the grinding parameters obtained from the conventional grinding test. The comparison shows an average relative error of 4% and an R2 value of 0.9."

Jan 1, 2014

By Michael. H. Moys, Clayton Bhondayi

An electro-resistive measuring technique developed by the authors was used to study the effects of superficial gas velocity and froth height on froth phase bubble sizes as a function of height above the pulp-froth interface. Flotation tests and the bubble size measurement were carried out in a laboratory mechanical flotation cell that was operated in a pseudo-steady state mode using primary rougher tailings slurry from Lonmin Platinum as feed. The values of intra-bubble impact distances (IIDs) which are the estimates for froth phase bubble sizes obtained from the measurements indicated that as superficial gas velocity was increased, the values of IIDs decreased for the two froth depths tested. Increasing froth height at fixed gas rate resulted in an increase in IID values especially close to the froth surface. Changing froth height and gas rate alters froth residence times; longer froth residence times mean more time for bubbles to coalesce hence larger values of IIDs and vice-versa.

Jan 1, 2014

By B. Z. Wu

The flotation of low-grade zinc oxide ore which from Guizhou has been researched by sulfuration- amine method. The experimental result indicated that when pH of pulp was 11, good flotation index can be achieved by using sodium silicate as dispersant, mixed amine as collector, and the do-sage of sulfur sodium was 6kg/t, and the recovery of zinc can be heightened by using copper sulfate as activator and Hydroxamicacid as collector. When the zinc feed grade was 4.84%, the zinc concentrates with grade of 39.23 % and recoveries of 75.17 % were obtained by adopting this technics.

Jan 1, 2014

By I. V. Makarskii, D. N. Nikitin, L. G. Tarasova

"The extent and nature of the damage to diamonds at processing plant is largely determined by the design features of the equipment, the characteristics of the feed ore and the parameters of the ore disintegration process (change in the rotational speed of the autogenous mills, variations of the water supply to comminution process, choice of the optimum charge, etc.). To monitor the intactness of diamonds, an instrumental method using the X-ray tomography system and colored synthetic indicator diamonds was developed for identifying the process-related damage. The X-ray tomography system consists of a CT-Portable X-ray tomographic scanner, a crystal positioning device and customized software (developed by the Fraunhofer Institute and Aliud GmbH, Germany). The developed method enables improvement of the accuracy of the results, exclusion of the subjectivity of the mineralogical assessment, acceleration of data processing and promptly planning of the activities aimed at reducing the process-related damage to diamonds. KEYWORDS Diamonds, colored indicator diamonds, process-related damage, loss of mass, instrumental method, X-ray tomography system. INTRODUCTION Industrial tests of ore processing technology at the enterprises of ALROSA PJSC are accompanied by assessment of the process-related damage to diamonds. The assessment of the process-related damage to crystals is carried out for prompt elimination of factors contributing to the increase of impact forces in the process flow sheet of ore treatment plant. For this purpose a specially selected parcel of -4.0 + 2.0 mm sized natural indicator diamonds is used. The diamonds are exposed to ionizing radiation in order to turn them green and thus to create a distinctive feature. Colored natural indicator diamonds are described, photographed in several views and introduced into the process flow sheet of the processing plant, then extracted from the process flow, described and photographed again. The comparison of diamonds before and after their passing through the process flow sheet of the plant allows to find evidence of process-related impact on the crystal and to calculate the factor of process-related damage (the number of crystals damaged during liberation and recovery), the loss of crystal weight and the degree of damage to the crystals. The method of colored indicator diamonds is used to select processing methods, equipment or regime which would be the safest for diamonds based on the analysis of the factors of process-related damage. There are limitations of the method, such as:"

Jan 1, 2018

By A. Collings, A. Farmer

"Power ultrasound may be used in the processing of mineral suspensions to clean the particle surfaces of oxidation products and fine coatings, mainly through the large, but very localised forces, produced by cavitation, which is the formation and sudden collapse of bubbles in a fluid. Cavitation occurs preferentially at solid surfaces in a liquid: at container walls, inserted objects or suspended particles. When the cavitational bubbles collapse near a solid they do so by forming a very high energy jet directed from the point on the bubble furthest from, and directed towards, the surface of the solid, in effect micro jet blasting.This paper highlights some of the major mineral processes where ultrasonics is beneficial namely: Surface cleaning of detrital mineral particles, where container quality glass sand was upgraded to tableware quality and up to 20% improvements in the sharpness of high tension separation of mineral sands was achieved"

Jan 1, 2003

By A. V. Bauman

"Important for thickening processes is the ability of slurries to form under certain conditions aggregation and sedimentation stable systems. Substantial part of difficult to sediment solid particles in such systems may be in colloidal state. The technique to study the sedimentation and aggregative stability of the slurry developed by the author with co-authors makes possible to define kinetics of changes in the aggregative stability of the system with solid phase varying concentration in it and produce data on sedimentation stability of the system in preliminary investigation of the thickening process. Research of aggregative and sedimentation stability of the slurry complement standard methods of laboratory studies to prevent errors in development of water-slime thickening balance and water circulation to design new and upgrade existing processing plants. Statistical analysis of process audits of more than one hundred upgraded and newly commissioned processing plants carried out in recent fifteen years showed that more than two-thirds of problems arising in commissioning the processing plants are associated with misdesign and errors in thickening and water circulation system. Among the main reasons of process design failures are: non-conformity of actual characteristics of the raw material to design characteristics, low quality of preliminary studies at the stage of sedimentation process simulation, design failures, wrongly selected equipment for the thickening and water circulations systems. As of today a number of problems associated with laboratory studies of sedimentation process, first of all, with interpretation of precipitation curves produced at the stage of laboratory refinement of the thickening process have been pinpointed. (Bauman A.V. Outstanding issues in design of thickening and water circulation diagrams in processing plants // Ore processing. 2016. ?3 P. 58-62) ?????? ?.?. ?????????? ??????? ?????????????? ???? ???????? ? ??????????? ?????????????? ??????. // ?????????? ???. 2016. ?3. ?. 58-62))"

Jan 1, 2018

By Derek Caizergues, Hurman Eric

The principle of carbothermic reduction has been around for many years. In principle it is a simple process, yet with a multitude of problems. The temperature required to affect reduction is in the region of 2200ºC and results in aluminium oxy-carbide formation rather than metallic aluminium. From a thermodynamic point of view, reducing the temperatures of reaction which would suppress oxy-carbide formation would only be possible by lowering the total pressure of the system. A decrease in thermodynamic activity of product aluminium by dissolving it in another phase would also help preventing the formation of oxy-carbides and would also increase the yield of the reduction reaction. Thus experiments have been conducted at around 1700ºC to determine the possibility of carbothermic reduction of alumina under the presence of a metallic solvent. Total pressure of the system was reduced to around 30kPa and metallic nickel, iron, copper and tin were selected as the solvent. The highest recovery of aluminium was achieved with the nickel solvent followed by iron, copper and tin. This ranking for the first three was also in accord with the extent of negative deviation form ideality in the respective binary solutions of these solvents with aluminium. The tin-aluminium system displays positive deviation form ideality. The rate and extent of reduction was found to be highly dependent on temperature and pressure. The pseudo first order reaction rate was found to be applicable to the process in all the solvents used. Rate constants were calculated and it is also suggested that the reduction was controlled primarily by the chemical reaction rate.

Jan 1, 2003

By Gustav Hawlitschek, Henrique Kahn, Carina Ulsen, Renato Contessotto

"The problems related to waste dumping increased with the growth and development of large cities. In the U.K., more than 50% of landfill waste comes from construction use and the U.S. alone produces around 200 to 300 million tons of CDW annually. The exhaustion of natural sand deposits close to large urban centres stimulates the recycling of construction and demolition waste for the production of recycled aggregates as a construction material. This paper presents a flowchart for the production of recycled sand with low porosity and regular shape by the selective removal of the cement paste attached to recycled aggregates. The products characterization was carried out by the determination of the particle size and shape distribution, chemical and mineralogical composition, heavy liquid mineral separation and quantification of all present phases using a scanning electron microscopy with automated image analysis (SEM-MLA). The comminution of CDW by vertical shaft impact crusher made possible the production of a lower porosity recycled sand. The heavy liquid mineral separation showed that the proportion of low porous phases (d>2.5 g/cm3) is very high, exceeding 70% of the weight, encouraging further mineral processing separation to obtain a fine recycled aggregate with less cement paste content. The mineralogical characterization by XRD and SEM indicates that the main phases are tectosilicates, phyllosilicates and calcite which one can be attributed to both calcareous aggregate and cement paste. The precise quantification of cement paste and calcite/dolomite alone is just possible by automated image analysis. The characterization results demonstrated that proportion of phases with no cement paste attached increases progressively in denser products. The results of heavy liquid separations and image analysis are comparable and automated image analysis can be used for the characterization of phase content and their main associations."

Jan 1, 2014