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By S. Narra

Converting biomass into valuable fuel requires various preprocessing of the raw materials. Biomass densification is one of the conversion processes for its utilization. The aim of densification is to produce biomass pellets, which can withstand regular handling stresses and exhibit high densities with uniform size and shape. Physical properties, such as the particle size distribution after comminution is of highest importance for the binding mechanisms in the pelletisation process. Durability and strength of the pellets play an important role indicating the ability to withstand handling stresses. Particle size distributions of the cereal straws (Rye and Wheat) after specific comminution and liberation processes have been carried out with the help of three different image analysis (Microscope, Camsizer and Fibreshape). The durability of the pellets have been investigated as specified in the standards (ASAE standard S269.4) with a quadratic crate and the strength of the pellets with compression and tension testing machine (Zwick Roell type: ZMART.PRO). The particles size results showed differences in both length and width after different comminution processing. An exact comparison between the particle size analyses with the three different image analyses was not possible. The particle size distribution and the different comminution processes displayed influences on the durability and strength of the produced pellets. The particle size distribution displayed approximately 40 % of fines and 60 % of fibers. The particle size distribution displayed a direct relation to the durability of the pellets. Further durability and strength of the pellets displayed a good correlation.

Sep 1, 2012

By Thenepalli Thriveni, Seong-Young Nam, Nam-Il Um

New modern water treatment technologies required for arsenic removal from waste waters contaminated extensively by various background sources from mining, industrial waste, agricultural waste, painting industry and natural geological bed rock system etc. Arsenic is a widely dispersed element in the earth's crust and exists at an average concentration of approximately 5 mg/kg. Arsenic (As) and heavy metals may be released from the mine wastes to the ground and surface water systems, as well as the geological environment due to their solubility and mobility. This research focuses on the effect of accelerated carbonation process for successful removal of heavy metal arsenic anions from artificial waste water and mining waste waters. This accelerated carbonation process is a simple and novel method with 85 ~ 88% removal efficiency. Carbonation has been studied as a process to further improve immobilization of solidified/stabilized waste and granular waste. After successful removal of arsenic anions from solid mining waste and its potential benefits for producing construction materials. Besides, the industrial and urban management systems are generating bulk solid mining wastes, and most often dumping them in open fields. To prevent the landfilling with mining waste, many efforts are being made for the recycling of different types of mining solid wastes with a view to utilizing them in the production of various construction materials.

Jan 1, 2014

By Grant C. Lukey, Jannie S. J. van Deventer

"The environmental effects of the mining and mineral industry include destruction of natural habitats, changes in river regimes and water tables, and other serious ecological impacts. In this century, it is likely that water will become a critical resource, and in most countries the mining industry competes for a share of this resource. The Kyoto Protocol may at first seem only relevant to the coal mining and power industry, however, it should not be forgotten that the mining and mineral industry is a significant consumer of power. Therefore the ratification of the Kyoto Protocol by most developed countries and the introduction of a carbon credit trading scheme will impact on the industry by potentially increased costs in utilities and waste discharges. It is clear therefore that the mining industry faces many challenges in the coming years. The mining industry?s commitment to sustainable development needs to continue to evolve, in order to meet these challenges effectively. With the advent of globalisation of the industry, it is now an opportune time for the industry to gain international agreement on how they want the industry to achieve sustainability in future years; such a progressive approach is necessary, otherwise government will force the industry to change, which may not necessarily be the best outcome for the industry.INTRODUCTIONThe Earth Summit in Rio de Janeiro in 1992 was an opportunity for world leaders to assemble and discuss strategies and initiatives that provide for further industrial growth without adverse effects on the environment. The World Summit on Sustainable Development held last year in Johannesburg, South Africa, was an opportunity to evaluate those initiatives implemented over the past 10 years, and to set a new and sustainable direction for the future. It is clear that industrial and technology development will continue at a rapid pace in order to serve the needs of a growing world population, but it is essential that the course of this development is well planned, well executed, and that it is sustainable. In reality, while government officials and politicians continue to debate policy and international protocols, the environment continues to suffer and the effects of climate change and global-warming become more real each day."

Jan 1, 2003

By John A. Rumball, Martin R. Houchin

Data from autogenous and semi-autogenous tests in a 1.67m diameter mill have been analysed in terms of a new model for rock abrasion. This model defines specific rate as the rate of production of fines (material less than 13mm) per unit mass of rock, where the term “rock” is applied to all ore pieces of ore coarser than the grate size. In most cases, an allowance for preliminary rounding and cleavage was made. A method has been developed to analyse steady-state data, using piecewise fitting to the cumulative size distributions. The model was compared to the well-established models, which are based on the population balance method. The specific rate increased for all rock sizes as the volume of 100mm balls in the mill was increased. Tests using a coarser feed and smaller balls provided further evidence that once rocks are rounded, abrasion is due to localised surface damage, caused by impacts, rather than rotational shear. An allowance for rapid rounding of jagged rocks, followed by less rapid abrasion of rounded pebbles was also tested, but the analysis was not conclusive. The average specific rate is a useful measure of the capacity of a primary mill. The effect of power intensity (kW/t of ore) was also investigated as a means of extrapolating the pilot-plant data to large production mills.

Sep 29, 2003

By Vladimir Vigdergauz

"Electrochemical studies of metal sulfides in connection with their floatability are discussed. According Frumkin, sorption of electroneutral organic substances has a maximum near the potential of zero charge. This idea initiated attempts of application of electrochemical methods for the controlling of organic collector sorption and mineral flotation. The lecture reviews results of electrochemical studies of the processes taking place during sulfide flotation: redox-state of mineral surfaces and xanthate solutions, xanthate sorption and hydrophobic layer composition, surface wettability and flotation recovery of sulfide minerals. Redox-transitions of minerals, transport of ions and charging of mineral surfaces, electroreduction of dissolved oxygen and accompanying processes of oxidation of minerals and reagents-collectors, - all these matters became the subjects of detailed research. Cyclic voltammetry, rotating disk electrodes, spectro-electrochemical techniques and other modern experimental methods now routinely accompany studies of mineral processing. Relatively new electroanalytical techniques like the voltammetry of mineral particles immobilised on electrodes using polymeric binders have become extremely useful for studying weakly conductive minerals and dispersed flotation products. Full discussion of electrochemical studies of metal sulfides in relation to mineral processing must include bioelectrochemistry and electrocatalysis which open exceptional possibilities for selective leaching of gold and non-ferrous metals. At this time, the paper focuses on the sulfide flotation as a potential-dependent process; the problem of oxygen and its influence on the sulfide flotation; the electrochemical aspects of xanthate oxidation and sorption; theory of suspended electrodes as applied to the mineral slurries and experimental study of the effect of electrochemical pretreatment of flotation pulps."

Jan 1, 2014

By Brian Lindner, Lidia Auret, Niel Knoblauch

In this paper, a fault detection and identification framework based on feature extraction and topology extraction methods is proposed, and evaluated on a simulated base metals refinery high pressure leaching process. Feature extraction methods included linear and kernel principal component analysis, while process topology information was extracted with linear cross-correlation, partial cross-correlation and transfer entropy. Connectivity maps were constructed to identify possible fault propagation paths to aid root cause analysis. The results indicate that process topology can enhance the fault identification capability of data-based process monitoring methods. The study of the considered base metals refinery pressure leaching process is ongoing, with future work including the creation of a fault library which would lead to further critical evaluation of the proposed fault detection and identification framework.

Jan 1, 2014

By Lucy van de Ruit, Megan Becker, Aubrey Mainza, Jenny Wiese

"UG2 chromitite ore is a complex, highly disseminated platinum ore from the Bushveld Complex in South Africa, with typical platinum group mineral (PGM) grain sizes below 15µm. The introduction of stirred mills to the platinum industry has enabled grinding to finer product sizes, which has improved liberation and recovery of the finely grained PGMs. However, reduction in particle size leads to an increase in chromite entrainment in the flotation concentrate, which has a negative impact on the subsequent smelting process. Factors such as particle size, froth structure, solids concentration and water recovery have all been identified as impacting entrainment, but whether particle shape also has a significant effect is unclear. The purpose of this study was to determine whether the recovery of chromite particles by entrainment during the flotation of UG2 ore is affected by particle morphology. A laboratory vertical stirred mill with inert ceramic media was used for grinding UG2 ore which was then floated in a batch flotation cell. Flotation feed and concentrate samples were analyzed using QEMSCAN to quantify the angularity and aspect ratio distributions of the particles. The stirred mill product was found to have relatively broad aspect ratio and angularity distributions, with the major mineral components (chromite and silicates) having very similar shape characteristics. Analysis of flotation feed and concentrate samples suggested that particle shape does not have a significant effect on chromite entrainment."

Jan 1, 2014

By L. Gutierrez, R. Yepsen, F. Alarcón

Chile is the world's largest copper producer which is mostly in the form of sulfides for which froth flotation is the most efficient concentration process. As a result a concentrate that contains high concentrations of copper sulfides such as chalcopyrite, chalcocite and enargite is obtained. In the last decades processing of ores containing high concentrations of enargite (Cu3AsS4) has continuously increased in Chile, which is related to the fact that ore deposits nawadays are more heterogeneous and complex. Enargite is a mineral that contains arsenic and its presence in the copper concentrates implies severe penalties. In addition, the shortage of fresh water has driven the search for new alternative sources of water, among which seawater has proved to be one of the most attractive. The objective of this research is to study the behavior of the enargite in the process of flotation using seawater, and at the same time to compare its behavior with the results obtained using conventional water. The study was carried thorugh micro-flotation tests using pure samples of enargite, at pH values ranging from 4 to 11, both in fresh and seawater. PAX and MIBC were used as collector and frother respectively. Micro-flotation tests were also done at different redox potential conditions so that the effect of the surface oxidation of enargite was evaluated in seawater. The results indicate that the recovery of copper from enargite is reduced in seawater compared to fresh water, in particular at the pH values close to those of the formation of the first hydroxy complexes of Mg and Ca. In general, the experimental data indicate that the floatability of enargite is strongly affected when seawater is used, in particular at oxidizing conditions. These results suggest that Mg2+ and Ca2+ ions contained in seawater interact with the surface of enargite forming hydrophilic species.

Jan 1, 2018

By Luis Bergh, Juan Yianatos, Luis Vinnett

"Process automation as an engineering discipline is more than control systems since it includes industrial instrumentation, such as sensors, transmitters and actuators, as well as control and supervision systems, collection and transmission of data and real-time software applications to supervise and control the operation of plants or industrial processes. In the last several decades, accelerated technological development has provided a variety of software and hardware tools to aid development, maintenance and continuous improvement of automated systems. These developments however seldom reach their full potential in real plants. There are many factors to be considered, among them human capital specific training and the organization model. In this paper, a methodology for training engineers in advanced control and supervision of flotation plants is presented based on study of the application of these technologies in hybrid pilot plants. Since experimentation in real plants may present undesirable risks and costs, and simulation studies are usually limited to some unrealistic conditions, a laboratory where on-line measurements of the hydrodynamic behaviour of a pilot plant is mixed with phenomenological models has been created. In this form, an environment as close as possible to a real plant can be recreated. A flotation column and a circuit of three pneumatic cells are fully instrumented and connected to a PLC and PC network. In the control room, students learn applications of classical PID control in a DCS environment, advanced predictive control, on-line process operation diagnosis, fault analysis, virtual sensors and expert-fuzzy systems. Several undergraduate and graduate courses and theses are supported by this Process Control Laboratory infrastructure. Examples of these applications are discussed."

Jan 1, 2014

By L. A. Cisternas, R. I. Jeldres, C. Cruz, P. A. Robles

"Previous studies have shown that the floatability of chalcopyrite in seawater at highly alkaline conditions is significantly affected by the presence of clays. The reason is that the species of calcium and magnesium present in seawater under those conditions may act as a bridge between the surfaces of clay and chalcopyrite, generating massive aggregates that then depress. In this context, the objective of this work is to analyze the impact of pretreated seawater with low amount of calcium and magnesium ions on the recovery of a sulphide copper mineral with high kaolinite content as clay. The seawater pre-treatment is done by the addition of sodium hydroxide in a high carbon dioxide environment. The chemical reactions realized under these conditions lead to the formation and precipitation of calcium and magnesium species that are subsequently removed by vacuum filtration. The pre-treated seawater is then used in flotation tests at pH 11 for copper sulphide, where the mineral is synthetically prepared by mixtures of chalcopyrite, kaolinite, and quartz. When comparing the flotation results for different types of water, including seawater and pre-treated seawater, a significant effect is observed: as the seawater hardness decreases, which comprises the calcium and magnesium ions, the recovery of chalcopyrite is increased. However, the effect is markedly enhanced in the presence of kaolinite. Therefore, the results indicate that sodium hydroxide and carbon dioxide are able to remove different species of calcium and magnesium from seawater and could improve the chalcopyrite recovery with high kaolinite content. INTRODUCTIONIn many cases, mineral deposits are found in arid areas with little access to water resources. Water is a fundamental element to carry out the unit operations that achieved the separation of valuable minerals (especially in concentration operations). Seawater has acquired an interesting role in recent years (Cisternas and Moreno, 2014); in fact, it seems to be one of the few viable options to ensure the sustainability of the mining industry in arid zones. At present, there are numerous experiences of industries that use or have used this resource, either by submitting the seawater to a desalination treatment by reverse osmosis or by applying it directly, without desalting. The latter case may involve significant economic benefits (for example, by avoiding the investment of building a desalination plant) and in some cases some operational benefits. A positive aspect is that in general terms the foaming in the saline medium is much more efficient compared to fresh water (Quinn et al., 2014; Castro et al., 2010). Some reports show that the foaming doses required to achieve a certain quality of bubbles are remarkably reduced, reaching exceptional cases such as Xstrata's Raglan concentrator, where it did not even include foaming to carry out the operation. This fact is quite promising, considering that some researchers have stated that controlling the quality of bubbles and foam could float minerals through coarse particles. This would lead to multiple benefits, such as energy savings by avoiding excessive grinding and a lower presence of fine ore that causes major problems in water recovery operations by gravitation (such as thickening) and in tailings management. However, seawater also causes significant challenges in multiple operations (Jeldres et al., 2017, 2016; Castro et al., 2010), as for example in minerals with high clay content (Uribe et al., 2017). In fresh water, the presence of clays minerals in ores is already a major problem in the flotation stages since the operation becomes difficult to be controlled, and operators are commonly forced to increase the consumption of reagents because the collectors are deposited on the clays' surfaces reducing froth stability (Farrokhpay and Bradshaw, 2012). Sometimes the use of rheology-modifying reagents should also be incorporated since the pulps become more visc"

Jan 1, 2018

By P. Fawell, C. Castillo, C. Ihle

"The need to reduce fresh water consumption has pushed many Chilean mining companies to utilize seawater obtained from distant locations. At the same time, increasing amounts of fine particles in copper tailings raise new operational challenges, in particular, the thickening and transport of tailings featuring significant fine fractions, which are predominantly clays. In the present paper, we study the role of salinity – using seawater and NaCl – on the flocculation efficiency of copper sulphide tailings to which kaolinite was added. To mimic the water recovery stage in thickeners, flocculation has been induced in jar tests and the corresponding aggregate size distribution has been estimated from chord length distribution data obtained using a focused beam reflectance measurement (FBRM) probe, at various mean turbulence intensities. Results show that for constant flocculant dosing, a measurable influence of the salt on the resulting aggregation exists. For each case, resulting optimal turbulence levels are also reported, a particularly interesting feature when comparing flocculation efficiency of the coarse and fine fraction. INTRODUCTION The concentration of copper minerals through comminution and flotation is intensive in the use of fresh water. The need to reduce the consumption of fresh water and the environmental standards associated with increasingly demanding mining operations have driven improvements in the techniques of recovering water from tailings. The challenges are even greater when required to treat minerals with high clay contents. In Chile, kaolinite is one of the most important clays to consider due to its abundance in the tailings from many operations. The most common and highest throughput unit operation in the mining industry for the recovery of water from tailings is gravity thickening, with sedimentation of fine particles assisted by flocculation. Flocculation is the process of forming aggregates by contacting the suspended particles with a flocculant. The flocculant is typically a water-soluble synthetic long-chain polymer, where copolymers of acrylamide and sodium acrylate are the most common types used in the Chilean mining industry. The aggregation mechanism includes the following key steps: (1) flocculant distribution through the suspended particles, (2) flocculant adsorption onto particle surfaces, and (3) collisions between particles leading to polymer bridging to form aggregates, but concurrently (4) breakage of aggregates becomes a factor under prolonged shear (Gregory, 1988)."

Jan 1, 2018

By Lawrence Bbosa, Aubrey Mainza, Indresan Govender

"Positron Emission Particle Tracking (PEPT) and the Discrete Element Method (DEM) are used to develop a probability based model for the power draw of a tumbling mill. Experiments are conducted using dry spherical glass bead charge in a laboratory scale tumbling mill, which is mounted with a torque transducer and tachometer to measure mill power. Particle tracking information from PEPT is used to reconstruct the motion of glass beads and infer the overall charge behavior, while DEM is employed to simulate particle motion and interaction, with collision mechanics calculated using the Hertz-Mindlin contact model. For both sets of data, the product of torque and average angular velocities in discrete cells are accumulated to obtain mill power. This method is found to be within statistical agreement with measured power for all tests. The information from both techniques is then used to develop a model for the power draw as a function of particle size, mill speed and volumetric filling. Predictions of the model match well with measured and calculated values. The model is found to predict mill power within close agreement with measurement and follows trends consistent with existing work on tumbling mill modelling."

Jan 1, 2014

By Y. Y. Li, Q. Chen, Y. X. Cai, Q. Zhang, S. Mao

"Due to the influence of combustion conditions, the fly ash produced by some power plants has the problem of high-carbon content. The unburned carbon in fly ash can be removed by flotation, and the decarbon tailings should reach the national standard level I fly ash. The fineness of the requirement is one of the important indicators and is also an important factor affecting the tail ash activity. In this paper,adopting two methods investigate the effect of particle size on the flotation index: one is direct flotation of fly ash, and the other way is wet grinding + flotation of fly ash, comparing the two methods and selecting the appropriate process,which provides a way for the effective utilization of fly ash. INTRODUCTION Fly ash is a solid waste discharged from coal-fired power plants. The annual amount of emissions of fly ash are very large in China. The amount of fly ash were discharged from coal-fired power plants are increasing gradually, and the amount of fly ash stored has exceeded 2.5 billion tons, but the comprehensive utilization of fly ash is not high, which brings about a huge environmental problems( Lu et al.,2011). Carbon is a harmful component of fly ash in cement and concrete application (Zhang et al.,2008). Fly ash decarburization is an essential link to improve the utilization efficiency of fly ash and the reduce pollution ( Yang et al.,2012). Carbon is selected from fly ash to make full use of fly ash resources and improve utilization of fly ash (Li et al.,2008). In this paper, the flotation decarburization of high-carbon fly ash is studied, through comparing the grinding and not-grinding processes, optimizing the separation process of fly ash, which provides a way for the effective utilization of fly ash."

Jan 1, 2018

By Gus Van Weert, Samuel A. Bolorunduro, David B. Dreisinger

"Silver is currently lost as jarosite during the pressure oxidation of sulphides and cyanidation of the residues yields 5-10% of silver. Efforts to recover silver from complex sulphides, which contain economic fractions of silver require an understanding of the behaviour of acanthite during pressure oxidation. However, previous studies of acanthite (Ag2S) reaction have been complicated by the formation of argento-jarosite and uncertainties arise on the interpretation of the results.In this work, the acid pressure oxidation of high-grade natural silver sulphide mineral (acanthite) was carried out at 110-150°C and under the conditions similar to that of pressure oxidation of complex sulphide. The predominant product of reaction is elemental sulphur. The rate of reaction increases with increasing temperature and with the presence of ferric ions. The kinetics is controlled by chemical reaction with activation energy of 72.6 kJ/mol. The rate of reaction decreases with the presence of silver sulphate in the initial slurry. The proposed overall reaction is close to: []"

Jan 1, 2003

By Shuji Owada, Shinya Suzuki, Chiharu Tokoro, Daisuke Haraguchi, Sayaka Izawa

"Coprecipitation with ferrihydrite has been one of the major treatment method for As(V) removal from wastewater such as acid mine drainage. We already confirmed coprecipitation of As(V) with ferrihydrite consists of two kinds of mechanism; one is two dimensional As(V) uptake to the surface of ferrihydrite by surface complexation and another is three dimensional As(V) uptake into ferrihydrite by surface precipitation. We also already confirmed As(V) adsorption process by ferrihydrite could be quantitatively evaluated by original surface complexation model with parameter values reported by Dzombak and Morel. However, As(V) coprecipitation process couldn’t quantitatively be represented by only the original model. In this study, construction and calculation using surface precipitation model were attempted for As(V) coprecipitation treatment with ferrihydrite. In the surface precipitation model, precipitation was described by the formation of solid compound between ferrihydrite and ferric arsenate. Activity of these precipitates was determined by surface precipitation ratio of FeAsO4(s) obtained experimentally from XANES analyses. Solubility products of surface precipitation of FeAsO4(s) (Ksp_FeAsO4(suf.)) were determined by fitting to sorption densities and surface precipitation ratio in each condition. The values of Ksp_FeAsO4(suf.) were determined 10-7.7 at pH5 and 10-10.2 at pH7, respectively. Based on the obtained Ksp_FeAsO4(suf.) value, As(V) removal and isotherm were calculated for As(V) co-precipitation treatment using surface precipitation model. Good agreement between experimental and calculated values was observed. These results were suggested that the quantitative prediction of As(V) co-precipitation treatment was possible if Ksp_FeAsO4(suf.) value was estimated experimentally."

Jan 1, 2014

By Brian Hart, Rong Fan, Roger Smart, Andrea Gerson, Ning Xu

A complete strategy has been developed for identification of the reasons for losses in recovery and/or grade, due to changes or complications in mineralogy and in mineral surface conditioning, and their subsequent correction. The sequence of methods starts with comparison of mineral phases between QEMSCAN/MLA (compositional) and Rietveld XRD (crystalline diffraction) with bulk assay reconciliation. This methodology has recently led to identification of unrecognised amorphous content (12-40 wt.%), previously attributed to crystalline phases, in the fine fraction (<35 µm) of some problematic flotation feeds. Attached amorphous silica, talc- and chlorite-like fines have direct influence on the hydrophobic/ hydrophilic ratio on value mineral surfaces adversely affecting flotation. SEM/EDS is used in the backscattered imaging mode to determine possible problems with liberation (e.g. remnant local locking), not detected in standard liberation analysis, resulting in gangue flotation. EDTA extraction is used to assess bulk feed pre-oxidation and sequential oxidation product loading through the circuit. Changes in circuit solutions are assayed with speciation modelling of precipitates and potentially adsorbing species. ToF-SIMS with principal component analysis is then used to correlate surface species with specific minerals and can be used to assess the effectiveness of specific reagents particularly collectors. This approach identifies unwanted activating species and interference with value surfaces by adsorbed hydrophilic ions, precipitates and fine particles. When the interference or ineffective reagents are specifically identified, remedial action can be targeted. This method has identified residual talc-like layers (<10 nm thick) inducing gangue flotation of pyroxene and chromite in PGM flotation. Recent case studies of application of the full methodology to losses of molybdenite at KUCC and to sphalerite activation in the Cu/Pb circuit at Brunswick Mines with remedial action are discussed.

Jan 1, 2014

By R. V. Kononko, A. Yu. Chikin, R. N. Rakhmeev, Yu. O. Fedorov

"The focus of the study is finding a solution that can help to improve diamond recovery in diamond-bearing gravity concentrates upgrading flowsheets. The purpose of the study was to develop and prove scientifically a separation method of diamonds recovery from gravity concentrates regardless of their fluorescence ability induced by X-ray radiation. Two promising recovery methods applicable to diamonds of this type are proposed, i.e. an X-ray radiometric method based on an instantaneous analysis of a secondary X-ray spectrum of separated particles, and a triboelectric method that relies on noncontact measurements of particle charges obtained during its motion in a vibratory tray. As a part of the laboratory study, X-ray fluorescence spectra of the collection of diamond crystals and main associated minerals and rocks at a particle size of -6+3 mm were produced. The analysis of the produced secondary X-ray spectra showed a significant difference between crystals, minerals and rocks within the analytical area of Ca, Fe and Zr due to the absence of calcium, iron and zircon elements in diamonds. Additionally, the scattered X-radiation level of diamonds substantially increased under the influence of X-ray radiation. Such a difference is a physical base of a new method of diamonds recovery from mineral mixtures. The laboratory study on triboelectric characteristics showed that a significant portion of diamonds gained an electric charge of a magnitude that was much higher, compared to associated minerals and rocks. The laboratory and industrial tests and the separation indicators demonstrated a high efficiency. A proposed X-ray radiometric method provides recovery of all types of diamonds regardless of X-ray fluorescence levels, with high selectivity and recovery rate of at least 98%. This proposed separation method is protected by a patent of Russian Federation (No. 2551486, “A method of X-ray radiometric separation of diamond-bearing materials”). Triboelectric separation organized in two stages (main and control) ensures recovery of up to 98-100% of diamonds at a particle size -5+2 and -2+1 mm,. More than 10 triboelectric separators successfully operate in active diamond processing plants in the Russian Federation."

Jan 1, 2018

With significant increase in steel output in the world the price of iron ores has been soaring recently. Especially, there is a strong demand for iron ores in China, leading to more attentions paid to developing low grade iron ores. In this paper mineralogy of nm-of-mine hematite ore was deter-mined, and coal-based direct reduction-magnetic concentration was successfully developed to beneficiate low grade hematite ore. Mineralogy analysis indicates that this hematite ore is a super fine refractory ore, with the main valuable mineral hematite being closely associated with quartz and distributing uniformly and mostly occurring within the size of 3~5J.lITI,leading to being difficult to beneficiate due to super fine hematite and only grading 28.83% Fetotal. This hematite ore failed to be effectively upgraded by traditional processes in trial tests, such as reverse flotation, gravity concentration, and magnetic separation, or the integration of the above processes. In contrast with adoption of the coal-based direct reduction-magnetic separation process, concentrate was produced with high iron grade and metallization degree in the present work, which provides a theoretical basis for utilization of low grade iron ores. By optimization of direct reduction conditions, such as reduction temperatures, duration and mass ratio of reductant coal to iron ore, the reduced ore with 93.72% metallization degree was prepared, and then three-stage grinding-magnetic separation of the reduced ore were conducted, the final concentrate was manufactured, assaying 69.54% Fetotal and 98.01 % metallization degree, and with low content of impurities. This iron concentrate with high metallization degree produced by this process is a superior burden for converter instead of blast furnace. This process is enviromnent friendly by directly making iron using coal and iron ores instead of coke, resulting in less emissions and low production cost.

Jan 1, 2014

By Gaurav Soni, Roe-Hoan Yoon

A first principle flotation model has been derived from the basic mechanisms involved in flotation. The model consists of a series of analytical equations for bubble generation, bubble-particle collision, attachment, detachment, and froth phase recovery. The model can predict flotation from both hydrodynamic and surface chemistry parameters such as bubble size, particle size, energy dissipation rate, ?-potentials, contact angles (?), etc. The model predictions have been compared with the results of a series of laboratory flotation tests conducted using mono-sized glass beads of different particle sizes and contact angles under different operating conditions. Some of the experiments were conducted using a 1:9 mixtures if hydrophobic silica and hydrophilic magnetite, so that the product graded could be readily determined by simple magnetic separation. The model predictions are in good agreement with the experimental results both in recovery and grade. A computer simulator developed on the basis of the model is capable of designing a preliminary flotation circuit on the basis of feed characteristics, e.g., size-by-liberation data, and the hydrodynamic information on the flotation cells to be incorporated in the circuit.

Jan 1, 2014

Mineral flotation is effective over a relatively narrow particle size range of approximately 10 µm to 150 µm. If the upper particle size limit can be increased, however, a run-of-mine ore may be coarse ground, and only the middlings are ground further to achieve required grades. This will result in significant energy savings and increased throughput. In this communication, methods of increasing the upper particle size limit will be discussed on the basis of a flotation model that can predict flotation from both hydrodynamic and surface chemical parameters. An example of increasing flotation recovery by control of a chemistry parameter is given.

Jan 1, 2014