Search Documents

By Leopoldo Gutierrez

Eight oil sand ores with the bitumen content ranging between 3.6 and 15 wt.% and the fines content (-44 micrometers size fraction) between 9 and 69 vol.% were subjected to the standard alkali extraction test used to measure the degree of oxidation of metallurgical coals. The results showed that there is a strong correlation between the absorbance of extracted solutions at a wavelength of 520 nm and the ratio of the fines content to the bitumen content. The latter factor is directly relevant to assessing the extractability of bitumen from oil sand ores. Bitumen extraction tests showed that the bitumen recovery decreased from 90 % to 30 % when the absorbance at 520 nm increased from 0.23 to 0.64. A comparison of the UV/visible spectra of solutions obtained from the alkali extraction tests with solutions of Aldrich Humic Acids suggest that low bitumen/high fines oil sand ores release substantial amounts of organic matter very similar, if not identical, to humic acids. In contrast, high-bitumen and low-fines ores do not release as much of the organic matter, and UV spectra of these leached substances are quite different from those of humic acids. Overall, the results show that chemical composition of bitumen in the tested ores varies greatly with ore type and oxidation, and that the alkali extraction test is a promising technique to quickly assess the extractability of bitumen from a given ore type.

Sep 1, 2012

By J. A. Sweet

The issues facing graduate training in the mineral processing industry are not too different today from those that prompted the initiation of the Anglo American Platinum Graduate Development Programme (AGDP) in 2002. Graduate metallurgists in South Africa enter the industry from different undergraduate programmes at various tertiary institutions, and so the knowledge and skills of the young graduates varies. Further, the geographical expansion of the industry combined with the downsizing of business units means that there are fewer opportunities for young graduates to be mentored through their first few years on site. Anglo American Platinum chose to address these issues by implementing an intensive, structured graduate training programme for all their new metallurgical graduates, known as the AGDP. The first two years of experience of the AGDP, from the viewpoints of both graduates and lecturers, were presented to the mineral processing community at the IMPC in Turkey in 2006 (Sweet et al, 2006). From the beginning, the programme was structured in a modular fashion to include a basic technical ?toolbox? including statistics, the scientific method and sampling protocols, while the mineral processing content comprised advanced learning in comminution, classification and flotation (later extended to include hydrometallurgy). Technical communication ? both written and verbal ? was included from the start. The programme was focussed very strongly on site work (?learning by doing?), with a major integrated site campaign conducted and analysed by each cohort. In 2012 the AGDP will accept its ninth cohort into the programme. This paper describes how Anglo American Platinum and the University of Cape Town have developed and adapted the programme over the last few years, in response to the challenges of the global recession, skills retention, and the changing operational needs of the company. The programme, which was drawn up to accommodate around 15 concentrator-only graduates, now accommodates 35-40 concentrator, smelter and refinery graduates annually. The programme has also been modified to facilitate new graduates spending most of their first year on the operations. The benefits of the programme for Anglo American Platinum have been tangible, and will be discussed in the paper. Keywords: graduate training, technology transfer

Sep 1, 2012

By D. Saramak

The comminution technology based on High-Pressure Grinding Rolls presses (HPGR) application is currently one of the most efficient methods of hard ore comminution from the scope of the energy consumption and the development of industrial HPGR applications in ore preparation circuits is presently the world trend. However, even though the technology is already in use in many countries, which are the leaders in application of modern mining technology, there is still lack of base investigations over the HPGR performance. Throughput and energetic models of HPGR performance are quite well developed, but technological models predicting the comminution effects still needs an in-depth research. In the paper authors present the method of modeling of HPGR products? particle size distribution with using of suitable mathematical models. A basis of the HPGR performance assessment and HPGR-based crushing circuits design is a product?s particle size distribution. In order to precisely determine the particle size distribution of a HPGR product, parameters of product?s particle size distributions should be conditional on the main technical parameters of the roller press like operating pressure and the speed of rolls. The most accurate approximation of a distribution of size particle d appeared the Weibull?s truncated distribution and it is possible to obtain significant relationships between the approximation formula and the value of operating pressure, or feed characteristics. It makes possible a determination of mass recoveries of the product?s respective size fractions and the productivity planning. Instead of pressure (P), the other HPGR operating parameters can be applied, but the P value appears to produce the most relevant relationship. Keywords: HPGR, comminution, particle size distribution, ore processing

Sep 1, 2012

By H. X. Yan, J. X. Zhang, F. S. Niu

"The analysis on influencing factors of hydraulic conditions in fine hematite flocculation, such as stirring speed, stirring time and axial distance of particle size and fractal dimension of floc was investigated. Furthermore, response surface methodology(RSM) has been applied according to the Box-Benhnken center-united experimental design principle to optimize parameters of hydraulic conditions as a response index to indicate the fractal dimension of floc. The results show that when the agitation speed is 900r/min, the axial distance is 2.0cm, and the stirring time is 3.0min, the particle size reaches the maximum value of 35.44µm and the fractal dimension is 1.6594. The interaction between the axial distance and the stirring speed is highly significant, but the interaction with the stirring time is not obvious. The experimental data and model predications match well, which indicates that the established model has high accuracy and practicability. INTRODUCTION With the exhaustion of iron ore resources that are easy to be mined and the vigorous demand for iron and steel, the exploitation and utilization of fine-grained embedded iron ore resources have drawn attention from the industry and the government [1~2]. Flocculation flotation is one of the effective methods for separation and recovery of fine granular minerals. In 1975, the method was first applied and succeeded in Tilden Concentrator, USA. Flocculation and desliming became the key technology of the Tilden to raise its annual treatment capacity from 4 million tons to 8 million tons at that time [3 ~ 4]. In 2008, the selective flocculation and desliming-reverse flotation technology was successfully used to treat 2.8 million tons of Qidong iron ore. Under the conditions of 28.36% raw iron grade and 98% grinding fineness -0.038 mm, the ideal index of 62.5% iron concentrate grade and 68% recovery was obtained [5]. Dr Kitchenner of the Royal College of Mining and the Ore Processing Research Group of Wallenstein Laboratory first proposed the use of flocculation to separate minerals. After that, many scholars conducted a great deal of theoretical and practical researches, but mostly they focused on chemical theories, mathematical models and selectivity differences in the flocculation process, while the research on the influence of the pulp flow state on the separation effect in the flocculation process started later [6~9]. The results show that the motion of the agitated flow field has a significant influence on the formation of flocs. The fluid morphology will change with the change of hydraulic conditions. The change of fluid morphology will not only affect the movement behavior of particles, but also change the action of chemical agents on the surface of mineral particles[10~12]."

Jan 1, 2018

By Sanja Miskovic, Manjunath Basavarajappa

In this study, a coupled CFD-DEM (Computational Fluid Dynamics-Discrete Element Method) approach is used to simulate two-phase, solid-liquid flow within the flotation cell. Turbulence plays a key role in flotation cells and level of turbulence is affected locally by the presence of particles. Turbulence in the flow is modelled using Reynolds Averaged Navier-Stokes (RANS) based k-e model. Using particle transport and spatial distribution, mixing mechanism for differed sized particles are analysed. By including the effects of particle-particle collision, particle rotation, and particle translation, as well as the volume occupied by the particles in the fluid, CFD-DEM approach can be used to accurately predict the motion of particles in the turbulent solid-liquid flows with strong coupling. Electrical resistance tomography (ERT) is used to investigate the effect of impeller size, shape, off-bottom clearance and impeller speed on mixing and suspension behaviour inside flotation cell. The effect of flotation impeller design, impeller size, and off-bottom clearance on flow hydrodynamics is investigated. In the case of moderate and high solids loading (> 10 %w/w), energy is dissipated through inter-particle interactions and four-way coupling becomes important (Derksen 2003). The main goal of this study is to understand the effect of particle size and concentration on flow dynamics at high Re in highly turbulent systems using advanced modelling and measurement techniques. Experimental measurements obtained by ERT) system allowed detailed mapping of temporal hold-up profiles of the dispersed phase. Impeller size and off-bottom clearance are found have significant effect on the particle suspension characteristics.

Jan 1, 2014

By M. Ito

Cobalt-rich ferromanganese crust and nodule ores from seamount areas contain volcanic and sedimentary rocks as substrate or nuclei and these ores require mineral processing to remove the substrate/nuclei rock before smelting. This paper reviews the results of jig separation and air table treatment for the coarse fraction and flotation and hybrid jigging for the fine fraction. Using these techniques substrate/nuclei rock was removed from the cobalt-rich ferromanganese oxide components. The mineralogical properties and metallurgical treatment methods including hydrometallurgical treatment of low grade ore is also reviewed.

Sep 1, 2012

By Ghislain Bournival, Cagri Emer, Seher Ata

"It is well known among flotation practitioners that the contact angle can be correlated with the amount of material recovered from feed by flotation. The contact angle of solids can easily be modified by the addition of a collector. However, some collectors also have frothing properties thus altering the solid and bubble surface properties simultaneously. To avoid this problem, a technique has previously been used in which silanol groups are attached to the surfaces of the particles, but this method has its own problems. In this work, silica particles with various surface hydrophobicities were prepared using an esterification process. By using alcohols with different hydrocarbon chain lengths, from 4 to 12 carbon atoms, surfaces with a wide range of contact angles could be prepared. The technique was used in the modification of silica particles that were tested in a fluidized bed flotation column, and a laboratory mechanical flotation cell. In parallel experiments, dodecylamine (DDA) was used as a collector. It was found that irrespective of the type of flotation machine and surface preparation method, there was a close correspondence between flotation recovery and the contact angle of the particles. The silanation process has known drawbacks relating to the presence of moisture during the reaction, and the stability of the silane coating after it is been prepared. Esterification does not suffer from these disadvantages. This work has shown that the esterification technique is a robust alternative method for preparing hydrophobic quartz surfaces."

Jan 1, 2014

By Paolo Bevilacqua, Paolo Antonini, Lorenzo De Lorenzi

"Ceramic production requires large quantities of K-feldspar, which is commonly sourced from granites, alkali-granites, and feldspathic sands. These rocks contain other minerals, such as quartz and plagioclase, which are undesirable for ceramic production. Due to the coarse mineral grains that constitute these rocks, a reasonable liberation is achieved at a relatively coarse particle size.The feasibility of feldspar-quartz separation using a dynamic dense medium separation system has been investigated as an alternative to flotation techniques. The use of a two stages cylindrical vessel (Tri-Flo) was preferred to a conical vessel, due to the improved separation efficiency.In a full-scale processing plant, a dense medium separation process can be used as a K-feldspar preconcentration step. This reduces the amount of material to be treated in the more expensive processes, such as finer comminution, flotation or magnetic separation.A comparison between commercial raw materials for the ceramic industry and the “rich in feldspar” products of the Tri-Flo process is reported, and the validity of the process is demonstrated."

Jan 1, 2003

By Z. Y. Lan

Bioleaching of marmatite with various mixed cultures of microorganisms was investigated. The experiments were carried out in shaking flasks with iron-free nutrient and the pulp density of 10% wt/vol at the temperature of 30?. The results show that zinc is preferentially leached before iron. The leaching rate of zinc with the mixed culture of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans is 62% in 18 days. The leaching rate of zinc with the mixed culture of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans is nearly the same as that with the mixed culture of Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans (45% versus 50%). SEM and EDX analysis of the leaching residues indicate that a solid product layer composed of iron sulfide, elemental sulfur and jarosite accumulates in the mineral surface and becomes a barrier to the dissolution of marmatite. The bioleaching of marmatite follows the shrinking core product layer model. When the product layer increases and becomes insoluble, the leaching rate is controlled by the diffusion through the product layer and slows down. When the product layer decreases or becomes a porous layer, the leaching rate is controlled by chemical reaction and enhanced dramatically.

Jan 1, 2014

By B. Y. M. Bueno

Biosorption of heavy metals can be an effective process for the removal of heavy metals ions from aqueous solutions. In this study, the adsorption properties of Rhodococcus opacus biomass for Pb(II) and Cu(II) ions was investigated. The effects of initial pH, initial metal concentration and biomass concentration on biosorption efficiency were studied in a batch system. Results showed that the initial pH would play an important role in the Pb(II) and Cu(II) ions removal by R. opacus and affected the zeta potential of R. opacus. The equilibrium adsorption was reached with 60 min. The Langmuir and Freundlich models were used for describing of adsorption isotherm data. The maxi-mum adsorption capacities of biomass were determined as 94.3mgg-1 and 32.2 mgg-1 for the Pb(II) and Cu(II) ions, respectively. The experimental data fitted to pseudo second order kinetic model. Adsorption capacity of Pb(II) ions was found to be reduced by the presence of the other competing metal ions in the system. The FT-IR results of R. opacus biomass showed that biomass has different functional groups and these groups are able to react with metal ions in aqueous solution.

Jan 1, 2014

By M. Ghiani, R. Peretti, S. di Giovanni, G. Zonnedda, A. Serci, A. Zucca

"Beneficiation of the epithermal gold mineralizations associated with an extensive alteration zone in the Serrenti-Furtei region on the island of Sardinia, is proving a complex issue. Experimental investigations have in fact demonstrated that while the ores contained in the upper parts of the deposit are amenable to conventional cyanidation, the gold contained in the refractory ores in the lower portions needs to be recovered by means of flotation, combined with leaching where necessary.The results of commercial heap leaching, carbon-in-leach (CIL) processing and flotation, designed on the basis of the experimental findings and applied to the oxidized portions and transition zones of the deep sulphide mineralizations, confirmed the expectations emerging from the laboratory tests."

Jan 1, 2003

By Rogerio de Oliveira Baldoino

The sedimentary phosphate deposit of Bayovar is located in a very dry area of Peru (desert of Sechura) which is close to the Pacific coast. It consists of seven superposed layers (beds) which call for different strategy of concentration. The ore is composed predominantly by apatite (84% in weight basis) plus silicates (16%). In order to treat the ore from beds 1-5, a suitable standard mineral processing circuit (composed of scrubbing, screening, attrition and desliming) started its operation in 2010, yielding 3.9 Mt/y of concentrate assaying 30% of P2O5. To concentrate phosphate from beds 6-7, however, it is necessary to carry out further cationic reverse flotation of silicates, at neutral pH, to yield a concentrate, which meets market specification. The new process was developed in laboratory scale by a collaborative program conducted between Vale S.A. and the University of Sao Paulo-Brazil. A pilot plant has currently been running in order to confirm the very good results yielded in laboratory scale. The successful accomplishment of flotation in the current beneficiation flow sheet will enable a capacity expansion of 1.9 Mt/y of concentrate assaying 30% of P2O5. As water resources are very limited at Bayovar region, all the steps of concentration, including flotation, must be performed with seawater, which must be continuously recycled. This work addresses some relevant topics related to the use of seawater in the reverse cationic flotation of silicates: influence of temperature, water quality (ageing and chemical composition) and collector type (ether amine versus condensate). The results indicate that condensate amine works better than ether amine. If flotation is conducted with the former collector, the separation process is able to tolerate changes in temperature (25-40oC) and water quality caused by either evaporation or ageing. Keywords: phosphate, flotation, seawater, temperature, ageing, concentration, salt

Sep 1, 2012

By Heiko Schiemann, Christoph Beyer, Thomas Pretz

"Due to multiple experiences in the field of planning and engineering of processing plants for secondary materials the Chair for Processing and Recycling of Solid Waste Materials decided to develop a software tool that supports the engineering and the planning of the basic layout of processing plants for secondary material flows. The detailed description of the material flow and its characteristic parameters is one of the main tasks to be worked out and should be considered as the basis for representative simulation results.The description of the material flow and its characteristic parameters is based on a fraction vector containing 12 material fractions. This is a compromise between a detailed material flow description and a compact and therefore time-extensive calculation model. Each material fraction is characterized by 15 parameters, which can be edited with the help of an easily accessible user-interface. In addition to basic parameters like ignition loss, water content and calorific value more parameters like the material fraction-specific particle-size distribution are contained. Using the model library SimuRec, the processing success and the recovery of complex processing plants for secondary materials can be predicted."

Jan 1, 2003

By Yury V. Kulikov, Rakan Rahbani, Arkady Y. Senchenko

"The relevancy of complex minerals treatment is constantly increasing taking into account mineral resources depletion. Different refractory ores and concentrates, oxidized and polymetallic ores, as well as metallurgical products (slags) can be assigned to such mineral type. The treatment of such products via conventional flowsheets requires considerable capital and operational costs and does not always provide high recovery level of valuable components into a saleable product. Therefore, considerable amount of ores and metallurgical products are not treated, or treated inefficiently. One of the most promising approaches that allows economic treatment of refractory products is their ultrafine grinding down to 5-20 µm with subsequent processing or hydrometallurgy. Horizontal bead mills - the IsaMillTM, developed by Xstrata Technology, received their wide application in mining industry. Standard testing is performed under laboratory conditions in an M4 IsaMillTM (volume - 4 liters) to define the parameters of fine grinding. This mill completely simulates the operation of full scale industrial mills up to 50 m3 in volume (up to 8000 kW motor). The paper describes fine grinding technology performed in bead mills, and the importance of testing according to a certified method for industrial equipment selection. The paper contains description of promising directions of fine grinding technology application for several projects in Russia and Kazakhstan."

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 S. Gaydardzhiev

Initial experiments towards preparation of hollow ceramic microtubes by dip-coating of fibrous plants with water based alumina gel-casting slurries using hemp and coconut fibres as templates have been done. It has been found that the wettability of fibres and accordingly the stability of the developed ceramic layer on their surface during slurry gelation varied significantly within the different fibre types. Good correlation between the diameters of the template fibres and the resulting channels has been found at the level of solids loadings used, 31 %. Hemp fibres used as bundles have led to formation of multi channel patterns while the coconut fibres-templated process resulted in uniform monochannel materials. The micro tubes have show good mechanical handling.

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 Kang N. Zhong, Hui H. Luo, Yi H. Wei, Yu L. Wang

"More than 85% of phosphorous reserves in China occur as middle-low grade phosphate of sedimentary origin. The main gangues are dolomite, quartz, silicates, and clays. The characteristics of minerals are finely disseminated. Flotation results have shown that the floatability of apatite of this kind of ore is much worse than that of igneous and metasedimentary origin because of its high specific surface area. Although some effective depressants, such as naphthalene sulfonate and phenanthrene sulfonate, are used to decrease the MgO content in the P2O5 concentrate, its presence is still high (about 2%) in the Chinese concentrates. Meanwhile, the wastewater may cause some environmental problems. Batch flotation results and measurements of specific surface area and CO3 2- have revealed that there is a relationship between the floatability of apatite and the surface area.A two-stage flotation flowsheet, which includes a combination of direct and reverse flotation, was developed for beneficiating sedimentary phosphate ores. The direct flotation was conducted in an alkaline medium and most of the apatite and carbonate minerals floated leaving quartz and siliceous gangue in the sink. In the reverse flotation circuit, the floated product was further beneficiated in an acidic medium to eliminate the carbonate as a float product. Apart from the high quality of concentrate, the two-stage flotation also facilitated the treatment and the recycling of wastewater. A wastewater recycling procedure was developed and tested in a continuous flotation process. The key factor was the careful selection of effective and non-toxic reagents."

Jan 1, 2003

By Andrzej Luszczkiewicz, Tomasz Chmielewski, Jan Drzymala, Andrzej Konieczny, Rafal Kaleta

Properties of the sedimentary Polish copper ore mined from the Legnica-Glogow Copper Basin (SW Poland) by KGHM Polish Copper S.A. were presented and currently used beneficiation technologies were described. Due to a unique lithological layered structure of the polymetallic deposit and existing mining system, the ore currently processed in the three KGHM concentrators is very complex with variable content of the carbonate, sandstone and shale fractions. The mined copper ore contains from 0.8 to 1.8 % Cu and Ag, Pb, Zn, Ni, Co, V and Mo as accompanying metals. The paper presents difficulties in upgrading the LGOM ore and selected possible solutions and development concepts of its processing. The first one is a chemical treatment with controlled amount of sulfuric acid of special product of flotation such as for instance middlings. The acid treatment leads to increased liberation of copper minerals and better further processing. Another concept is atmospheric leaching in oxygenated sulfuric acid and ferric ions solution as the major unit operation applied to selected low grade final flotation concentrates or flotation by-products. The third approach, based on copper ore pre-flotation with a frother to partially remove Corg, is also considered.

Jan 1, 2014

By Matthew Thurley

Optimisation and control of comminution, pelletization, and agglomeration processes is a complex task with large potential for gains in productivity, energy efficiency, and particle size distribution quality. One factor in realising these gains is the requirement for fully-automated online particle size distribution measurement. Moreover, online particle size distribution measurement that is based on the particles on the visible surface and can avoid or mitigate substantial errors that result from under-sizing overlapped particles and over-sizing areas of fines particles. Literature review indicates a body of substantially 2D photographic based particle size measurement systems that suffer from a large number of significant errors except in the simplest case of a monolayer of particles under good illumination with limited color variation in the material. In order to measure the visible particles on a pile there are a number of requirements including; avoiding particle delineation errors due to variation in material color and shadows, detect overlapping versus non-overlapping particles, and identify areas of fine particles as fines and not large rocks. Results are presented using a fully-automated online measurement system of crushed rock on conveyor belt using a 3D surface laser profile. The system provides continuous online measurement and results are shown on over four hours of production after the primary crusher. Size distribution results are calculated using volumetric estimation of the particles on the surface of the pile. The results show a strong capability to discriminate size variation especially in the 10% and 20% passing values. Furthermore results show that if areas of fines are misclassified as large rocks, and overlapped particles misclassified as small rocks, then a near complete loss of discrimination occurs for the P10 and P20 values which become largely constant values.

Jan 1, 2014