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By S. S. Yu

In this paper, the producing process of using V2O3 as raw material to obtain vanadium nitride was analyzed through the means of thermodynamic. The analysis shows that conversion follows the principle of reduction step by step in the conversion process of V2O3. The temperature of the reaction system has prominent influence on the nitrogen content of products, and the reaction is very sensitive to temperature. As raising temperature, the fine grain structure of the nitrides is more evident, and the grain size of nitrides increases. At 1703K, the nitrogen content of the products tended to be constant after soaking over 3 hours.

Jan 1, 2014

By Duong Huu Hoang, Nathalie Kupka, Urs A. Peuker, Martin Rudolph

"The froth ability, froth stability and the froth structure are strong influences in flotation process i.e. on water recovery, bubble size, entrainment of gangue particle, flotation rate constants, grade and recovery. The labscale flotation of rich apatite ore with a high mass pull leads to significant changes in pulp and froth properties over time. The froth stability decreases with increasing the flotation time. These changes can be related to different solid contents, reagent concentration, froth heights and bubble size distributions. This study presents the results from froth studies and discussions on the particle size of fully liberated silicates and degree of entrainment based on automated mineralogy size-by-size analysis. The change of entrainment in a rich apatite ore batch flotation with time will describe more precisely by measuring froth properties using a Dynamic Foam Analyzer. It is concluded that the degree of entrainment is not only dependent on particle size but also the pulp density due to its effect on particle settling and also froth properties in varying resistance to particle drainage. Furthermore, entrainment models are applied to predict the effect of size, flotation time on entrainmentINTRODUCTIONFroth flotation belongs to the group of heterocoagulation separation techniques. Froth flotation is classically divided into two active zones, the pulp zone (where particle collection occurs) and the froth zone. A schematics drawing of the interaction between both zones is plotted in Figure 18 (Yianatos and Contreras, 2010). In froth flotation, the collision probability in the collection zone is governed by the physics of the process or hydrodynamics (Wills and Finch, 2016). The true flotation event in the pulp occurs when the hydrophobic valuable mineral particles collide with bubbles and formation of a stable particle-bubble aggregates moving upwards against gravity to the froth phase (Yianatos et al., 2009)."

Jan 1, 2018

By P. N. Mohan Das, K. Harikrishna Bhat

"The major ilmenite reserves are located in India at Chavara (CH), Manavalakurichi ( MK) and Chatrapur, Orissa (OR). India stands first in terms of ilmenite reserves, which are estimated to be 278 million tonnes out of which, 142 million tonnes are processable. Mineralo-chemical analysis shows that Chavara ilmenite is the most weathered one with about 60% TiO2 while Chatrapur is the least weathered with about 50% TiO2. Co-existence of ilmenite with pseudorutile, rutile and haematite is observed in substantially varying amounts in the three deposits. It is observed that the tropical weathering rather than the source rock difference has apparently played an important role in imparting major compositional and structural dissimilarities among ilmenites in different places.In processing of ilmenite through the Becher process, aeration rusting of pre-reduced ilmenite is found to be the rate limiting step thus, affecting the productivity of the process. Investigations have proved that the addition of some organic compounds such as glyoxal, sucrose etc., to the system accelerates the reaction to such an extent that the rusting time has been reduced to less than half.A new route of processing ilmenite for synthetic rutile has also been developed in which, ilmenite is carbothermally reduced and then processed through plasma route. The slag thus obtained is processed further to get high-grade synthetic rutile, metallic iron and high purity iron oxide. The process has been scaled up in a continuous moving bed plasma reactor. It is technologically and economically more viable where, all the iron values are recovered as salable byproducts. This paper describes the salient features of the technologies developed for the beneficiation of ilmenite to synthetic rutile."

Jan 1, 2003

By Hamid-Reza Manouchehri

"The triboelectric charge attributes of feldspar, quartz and wollastonite minerals, after contacting different triboecharging medium made of different materials, were considered. Their charge acquisitions by different size fractions of minerals were monitored and accordingly their energetic work function values were estimated. Moreover the separation behaviours of these minerals through the electric field of a laboratory free falling separator were determined and the effects of some chemical reagents on separation their separation characteristics were studied.Finally an attempt was made to translate the findings from single mineral systems to a complex silicate ore, containing quartz, feldspars, wollastonite and some other silicates. The results show favourable prospect to apply the triboelectric separation technique for beneficiation such a complex raw material."

Jan 1, 2003

By V. A. Chanturiya

In Pt- and Au-keeping complex ores processing, about 10% ~ 15% of noble metals are lost with true tailings that are due to low floatability of Pt- and Au-keeping minerals by the conventional collectors. With the aim to achieve the effective recovery of noble metals at flotation of Pt-Cu-Ni and Au-keeping ores organic complex reagents keeping electron-donating atoms of nitrogen, oxygen, sulfur or phosphorus may be offered as selective collectors for the indicated minerals. These rea-gents tend to form complex compounds with PGM. Besides this, Cu-Ni-Pt and complex Pt and Au carbonated mica ores are characterized by finely disseminated (up to nanometer size) mineral forms of Pt in multivalent states. In this connection, the use of a combination of the strong ionic collectors with nonionic reactants that are capable to derivate complex compounds with multivalent PGM seems to be expedient for this type of ores. In the research new complex reactants were tested such as cyclic alkylene-trithiocarbonates, oxyalkyl butylxanthogen acid ethers, a combination of the collectors ? mercaptobenzothiazole (MBT) and dialkyldithiophosphates (DTP). Sorption and flotation tests were made with monomine-ralic samples of chalcopyrite, pentlandite, pyrrhotite, pyrite, and Pt-Cu-Ni sulfide ore samples. Sorption properties were examined by the extractive UV spectrophotometric method and potentiometric measurements. To indicate a structure of modified xanthate solutions the method of a thin-layer chromatography (TLC) was applied. The chromatographic behavior of the basic components of modified xanthate solution ? ButX, cyclic propylene-trithiocarbonate (PTTC), diethyl-dithiocarbamate (DEDC) and the product of its modification ? oxypropyl-S-ether of dithiocarbamatic acid was studied on plates ?Silufol UV ? 254?. The composition of organic solvents and its ratio in a mobile phase was deter-mined for simultaneous chromatography of the main components of a reaction mixture. It was found that operating selectivity of MBT, DTP and cyclic alkylene-trithiocarbonates incorporated in modified xanthate in relation to Pt-Cu-Ni and Au-containing sulfide minerals might be explained by an electoral sorption of this nonionic collector on a surface of the minerals studied. It was demonstrated that the application new reagent modes with the use of a combination of designed complex reactants helped to increase the extraction index of Pt- and Au-keeping minerals from complicated ores.

Jan 1, 2014

By Teja Reddy, Narasimha Mangadoddy, Mandakini Padhi

"In mineral comminution circuits, the feed to hydrocyclone consists of a heterogeneous mixture having varied degrees of liberation and sizes leading to the multi-component particle system. The presence of multicomponent particles exhibits a significant change in the classification performance parameters. In this work, a numerical study is conducted with an artificial mixture of magnetite and silica of different proportions having similar particle size distribution to understand the multicomponent interaction in a laboratory scale hydrocyclone. The heterogeneous feed is injected tangentially would attain different settling rates under the influence of centrifugal, drag and turbulent dispersion forces. In this work, Large Eddy Simulation (LES) is used to resolve the continuous phase turbulence. Modified Algebraic Slip Mixture (ASM) model using the corrected Newtonian rheology of fines to simulate multi-density and multi-size particles of the mixture in a hydrocyclone. The influence of the multi-component particles on classification performance is extracted from the simulation in terms of the performance curve, i.e. recovery to underflow, volume fraction distribution and the key forces acting on each particle in the mixture. An interaction was observed between different components during the classification process, featuring accumulation of heavier particle at wall-side pushing the lighter particles into the inner locus of zero vertical velocity (LZVV) zone. The comparison of separation factors of different size particles presented the higher probability of the magnetite of same size reporting to wall region and hence to underflow. Hence, an increased component cut-size with the increased magnetite proportion, particularly a profound effect on lighter density component’s cut-size was observed. INTRODUCTION The multicomponent existence is found in naturally occurring ores, affecting the pure metal extraction, nonetheless also affects the comminution and classification processes. Among many another classifier, hydrocyclone is a vital equipment used vastly in many industries. The main advantages over other classifiers are a static body, low operating cost and maintenance, high throughput, low floor space requirement etc. A typical hydrocyclone consists of a cylindrical section with a central tube connected to a conical section with a discharge tube. The fluid is injected tangentially into hydrocyclone causes swirling and thus generates centrifugal force within the device. The multiphase interaction inside the hydrocyclone is extremely complex and mostly explained by theories based on hypothesis. In past years, many theoretical models were proposed like a balanced orbital model (Criner, 1950), the residence time model (Reitema, 1961) etc. Though these models give an estimation of the cut-size and other performance parameters, it cannot predict the accurate performance of the actual state of operation. Among these models, the balanced orbital theory is the most adapted concept, based on the force balances of the particle in the dual vortex flow of hydrocyclone. The finer particle is subjected to the inward drag force, generated from the outer vortex flow to the air core, and drags the particle towards the overflow. The larger particle with the higher mass have enhanced centrifugal force and falls into primary vortex near wall reporting to the underflow. Generally, the forces acting on the particle include the drag force, centrifugal force, pressure gradient force, added mass force, Saffman lift force, Magnus force and basset force (Kraipech, 2005). The major forces like a drag, centrifugal, pressure gradient are the function of the particle properties like the size and the density. Hence, the existence of the multi-size and the multi-density particle will affect the separation phenomenon, with the varied forces acting on it. The understanding of the multicomponent classification effect using ores has been only explored in few studi"

Jan 1, 2018

By P. S. Dash

With implementation of stringent environmental regulations, ultra clean coal technology development programs have gained significant importance worldwide. As far as Indian scenario is concerned, most of the coals present in India are of drift origin and low grade, containing high mineral matter varying from 15% to greater than 50%. The inorganic or ash constituents of Indian coals are finely disseminated through the organic or carbonaceous constituents so, that commonly used physical beneficiation techniques are of only limited value in affecting separation. Chemical processes involve addition of chemicals, which react with the mineral matter and allow its easy removal. The present study envisages the effect of aqueous alkali leaching followed by acid washing on the removal of mineral matter from two different captive coals of Tata Steel at elevated temperature and pressure. The experiments are conducted at desired conditions using a bench scale pressure reactor set up having proper data acquisition and control system. The research study revealed, that it is possible to reduce the ash content up to 70% by this method. The alkali content of the product clean coal does not increase whereas the silica and alumina content reduces by nearly 58% and 62% respectively. Significant reduction in the phosphorus content is observed after the acid treatment. The crucible swelling number of the feed coal improves after the treatment. The mechanism of demineralisation was evaluated by analyzing the coal samples before and after the alkali and acid treatment using scanning electron microscope (SEM). Because of the acidic nature of the silicates and aluminates, they dissolve into the NaOH solution and form sodalite. Sodalite is partially soluble in the alkali solution. The hydrates formed during alkali treatment are partially removed due to acid wash. This study in overall provides an insight into possible alternative methods of beneficiation for removal of ash from high ash Indian coals.

Sep 1, 2012

By J. E. Gebhardt, D. McBride, T. N. Croft, M. Cross

"Heap leaching is well-established as a relatively low-cost and low-energy method of extracting metals from low grade ores. However, the design methodology, attention to the engineering details during heap construction and the long time scale in metal recovery makes the process susceptible to significant variation in the success of a heap leach operation. Often the laboratory predicted recovery rates are not achieved on site due to poor understanding of the complex physics of flow and coupled solid-liquid-thermal reactions within the multi-dimensional heterogeneous ore body. Given the large scale of commercial operations, small changes in metal recovery can substantially change the operating profitability. While there are a variety of approaches to heap leach modeling, computational fluid dynamics (CFD) modeling coupled with leach kinetic models offers a methodology to describe and understand the complexities of heap leaching. The CFD model uses leach kinetics specific for the mineralogy of the ore, including gangue chemistry, and provides an energy balance to calculate and predict temperature. Coupled with the CFD model’s inherent capability for modeling complex fluid flow, the physics and the chemistry of the heap can be simulated. This provides a tool for engineering design, as well as forecasting heap production under different scenarios. The calibrated model is used to simulate a three-dimensional test heap under fluctuating meteorological data, such as precipitation events, periodic solution application, and notably temperature. These simulations provide support for a methodology to design and engineer heap leaching of low grade copper sulfide ore. INTRODUCTION Worldwide copper ore reserves are faced with decreasing head grades with copper sulfides, particularly chalcopyrite being the predominant mineralogy (Nesse, 2000). Heap leaching offers an economical way to recover copper from low grade ore. The ore is stacked and a leach solution is applied and allowed to trickle though the porous bed of ore to extract target metals. The heap can be built with run of mine material or crushed ore and is constructed in order to achieve percolation of the leach solution to all regions. Bartlett (1998) provides an authoritative overview of the solution mining process where the leach solution interacts with the solid, the lixiviant dissolves the target minerals from the solid into the solution, and the dissolved species are transported out of the heap for subsequent recovery. Petersen (2016) provides a recent review of heap leach technology and emerging and potential future applications, and Ghorbani et al. (2016) summarizes the current state and challenges of the technology. Early applications of heap leaching offered a low cost technique to achieve high recoveries from oxide ores, typically greater than 70% depending upon the kinetics of reaction. As world copper resources transition to mainly copper sulfide mineralogy, such as chalcopyrite based ores, achieving high recovery from these copper sulfide deposits is proving more difficult due to the complexity of the leach kinetics, which leads to low leaching efficiency."

Jan 1, 2018

The effect of the acid anion on chalcopyrite (CuFeS2) leaching has been examined, under care-fully controlled conditions, in a range of acids in stirred reactors and columns at pH 1. Solution speciation calculations were performed to determine possible rate controlling species. The relative leach rates of Cu from chalcopyrite can be explained quantitatively entirely on the basis of solution speciation without the need to invoke any rational relating to surface structure/speciation. The rate of Cu release is first order with respect to Fe3+ activity. The stirred batch reactor experiments at fixed pH 1, Eh of 750 mV (SHE) and 75? showed that chalcopyrite leach rates were rapid in both HClO4 and H2SO4 with 100 % Cu recovery after 73h and 97 h respectively. However, the leach rate in H2SO4 was slower as compared to the HClO4 leach due to a slower increase in the activity of Fe3+ due to the formation of FeSO4-. The presence of Cl- in the leaches (HCl and H2SO4 with NaCl added) led to a low activity of Fe3+, due to the high activity of FeCl2+, resulting in very low leach rates. For the column leach experiments dissolution of Fe and Cu from the pH 1 HCl eluted chalcopy-rite column with quartz proceeded at several times the rate of any other column (chalcopyrite with and without quartz and/or pyrite leached with H2SO4, HClO4, HCl). Three observations indicate that galvanic interactions are not leach rate controlling role: a) The rate of leaching was not uniformly increased for the non-quartz containing columns where the two sulfide minerals, chalcopyrite and pyrite, are in physical contact as compared to the analogous quartz containing columns where they are not; b) there exists a reasonable correlation between the rate of Cu release and the effluent Fe3+ activity for all columns thus indicating that the leach rate is determined by solution speciation; and c) in all cases the proportion of Fe to Cu leached indicates preferential dissolution of Cu over Fe. However, the proportion of Fe to Cu is either the same or greater than expected on the basis of the single mineral columns. This indicates that chalcopyrite is not dissolving preferentially to pyrite.

Jan 1, 2014

By Pramila Misra, Jibardhan Meher, Debadutta Das

The concentrated coal-water slurry has been receiving considerable attention recently due its ability to replace fossil fuels. Attainment of stable and concentrated slurry has been succeeded so far through several physical and chemical techniques. The present article reports the formulation and stabilization of a highly concentrated coal-water slurry formed from five varieties of non-coking coals with variable ash contents obtained from Eastern part of India, employing three varieties of starch esters, such as starch benzoate, starch formate, and starch carbamate as dispersant. The apparent viscosity of the modified coal-water slurry has been measured by varying coal loading, dispersant percentage, pH, temperature, etc. The apparent viscosity of the slurry has been found to be decreased substantially on addition of 0.8% of adsorbate in the slurry. The particle-particle interaction has been considerably decreased and stable concentrated coal-water slurry containing high weight fraction of coal (61.5-63.5%) has been achieved in each case. The slurries stay in a non-settling form for about a month with viscosity in a permissible low range. The coal-water slurry has been found to behave as a non-Newtonian liquid. Comparison of the zeta potentials of the naked and modified coals evidences that adsorption of the dispersants at coal-water interface results in inhibition of the agglomeration of coal particles through mostly steric repulsions.

Jan 1, 2014

By Shobha Kumari

Coal is the prime source of energy in India. It now contributes to about 55% of the total power generation and will continue to have its major share in the energy mix of the country in the foreseeable future. Thermal coals of India, known for their wide variations in nature and categorized as difficult to wash due to their typical mineral matter association with the organic matrix, need suitable beneficiation technique for quality upgrade for improving the overall economics, efficiency and pollution free power generation. A non-coking high-ash coal, collected from Vasundhara open cast mine of the Ib Valley Coalfield, Orissa, has been characterized along with its different fractions obtained in the process of beneficiation for distribution of minerals using FTIR, XRD and ash analysis. The raw coal was fractionated by size as well as by density. It has been observed that ash yields and mineralogical composition (found to be mainly kaolinite and quartz) have no appreciable change in different size fractions, indicating homogeneous distribution of minerals in the coal matrix. However, for the different density fractions the mineral composition and ash yield have significant variations. The quartz content of the beneficiated coal visualized with 34% ash yield, as mandated by the Ministry of Environment and Forest (MOEF) for the use of coal in power plants is reduced to half of that of the raw coal. As quartz is the most abrasive mineral in coal, reduction of its proportion obviously signifies considerable reduction of wear of power plant machinery when beneficiated coal is fed to utility boiler for generation of power. The composition of the major minerals quartz and kaolinite as determined, also favors formation of ash of refractory nature during combustion. Keywords: IB valley coal, beneficiation characteristics,

Sep 1, 2012

By D. DePaoli, P. Zhang

"Phosphate ore is one of the most significant secondary resources for rare earth elements (REEs), and Florida phosphate is of particular interest due to its much higher ratio of heavy REEs, especially yttrium. Analyses of numerous samples from different phosphate processing streams in Florida showed that heavy REEs account for about 50% of the total REEs in Florida phosphate with yttrium accounting for approximately 30%. It was estimated that the amount of yttrium from US phosphate processing could meet the world demand for this critical element. This research aimed at recovering both REEs and phosphorus from a phosphate flotation tails. This tails is composed of mainly silica and phosphate with a small fraction of heavy minerals including monazite and xenotime. Since the specific gravity of silica is 2.6 versus 3.2 for phosphate and 4.5-5 for rare earth minerals, pre-concentration of the minerals of interest by gravity separation was investigated first. A pilot scale shaking table was used in this study. One pass gravity concentration achieved a shaking table concentrate analyzing over 600 ppm REEs at about 40% recovery. Flotation of the shaking table concentrate resulted in a product containing 1809 ppm REEs and 26.37% P2O5 with corresponding recoveries of 73% and 82%. Sulfuric acid leaching at 75oC could recover over 60% REE and nearly all the P2O5. Higher REEs (>90%) recovery was achieved by conducting leaching at higher temperature with concentrated sulfuric acid. The phosphoric acid from leaching of the flotation concentrate is of superior quality compared with that generated from regular phosphate rock.INTRODUCTION Rare earths are a group of 17 elements including those of the lanthanum series, as well as the non-lanthanides, yttrium and scandium. These elements have very specific critical uses in a multitude of markets. For example, lanthanum is used as a catalyst in breaking down crude oil to produce gasoline, diesel and jet fuel and neodymium is the core magnetic component in high-strength magnets for electric car batteries, wind turbines and hard disk drives. Rare earths are also essential for many military applications. Many of these applications have no substitute materials and the move to green technologies has dramatically increased their demand."

Jan 1, 2018

By P. Bevilacqua

In this paper the possibility to complete the copper recovery and to enrich in PVC a mixture of plastic granules obtained by grinding electrical cables are investigated. The recovery of a large part of the copper still present among the plastic granules was possible by means of a mechanical screening, the finer polymeric fraction was collected, at the same time. In order to complete the copper polymer separation the following techniques were employed. Counter current separation in water, static dense medium separation with zinc chloride solution and copper extraction with nitric acid and subsequent electrolytic deposition. A Tri-Flo® dynamic dense medium separator was employed in order to separate the lighter polymeric fraction, from the heavier polymeric fraction, mainly PVC. Water or a salt-water solution was employed to feed the separator device.

Jan 1, 2014

By Danfeng Xu

The majority of the world?s nickel (Ni) resources occur as laterite ores, which are exceptionally complex, lower grade (<1.5% Ni) and expensive to treat using conventional smelting and high temperature/pressure autoclave methods. Heap leaching is a promising, less costly, alternative technology for processing low grade nickel laterite ores. However, significant technical challenges remain with Nickel laterite heap leaching, preventing its general adoption. This paper presents some highlights of laboratory column leaching studies undertaken to characterise, evaluate and optimise sulphuric acid leaching behaviour of Nickel laterite agglomerates. They provide basic but valuable information regarding Nickel laterite agglomerate structure stability and leaching performance under industrially-relevant, continuous acid irrigation conditions. In particular, Nickel and other key metals? (e.g. Co, Fe, Al and Mn) extraction rates, free acid concentration, bed slump and structural changes were determined at a given acid percolation rate as a function of time. Potential implications of the findings, for devising strategies for improved Nickel laterite plant heap leach operations are discussed. Keywords: nickel laterite, column leaching, agglomerates, leaching kinetics, acid consumption

Sep 1, 2012

By Xiqing Wu, Tao Yue

"Magnetic seeding co-agglomeration, i.e. adding magnetic seeds, organic depressant (such as the starch), and pre-magnetization for co-agglomeration, was applied in the reverse flotation for hematite ore slimes. Samples of the hematite ore slimes and the pure hematite fines were investigated by the co-agglomeration, respectively. Flotation tests suggest that the depressing effect of starch in the flotation was further enhanced with the addition of magnetic seeds and the pre-magnetization. Following the laser size analysis and flotation tests, TOC adsorption analysis, VSM, surface charge measurement, AFM, FTIR study, and SEM imaging have been utilized to understand the depressing mechanism. Based on the results it was demonstrated that with the addition of magnetic seeds and the low field pre-magnetization, the adsorption of starch onto hematite minerals was strengthened through the magnetic seeding co-agglomeration. The co-agglomeration improved the flotation performance by introducing the magnetic interactions and acting the bridging adsorption of starch between fine hematite and magnetic seeds in a suspension, and then resulting in an intensified coverage of the starch onto hematite particles and positive action in the coagglomeration under the pre-magnetization.INTRODUCTIONFlotation is undoubtedly the most important and versatile mineral processing technique, and both its use and application are continually being expanded to treat greater tonnages and to cover new area. However, its influence was limited to a relatively narrow particle size range of 5–300 µm (Wills and Napier-Munn, 2006). The main reason behind this limitation lies in that fine particles have high specific surface area, so need relatively high dosage of reagents (collectors or depressants), and exhibit poor flotation performance while intermediate or properly-sized particles produce high flotation kinetics and need low consumption of reagents. In order to increase the recovery of fine particles, quite a few of flotation techniques have been investigated. Most of them are based on particle aggregation, namely, by enlarging the apparent particle size, such as carrier flotation (Valderrama and Rubio, 1998; Zhu et al., 2009), shear flocculation (Duzyola and Ozkan, 2010; Yin et al., 2011), selective polymer flocculation (Rubio et al., 2007; Song et al., 2012; Ng et al., 2015), oil agglomeration (Laskowski and Lopez- Vladivieso, 2004; Forbes, 2011), temperature responsive polymer flocculation flotation (Forbes et al, 2011), and etc. However, these techniques above-mentioned are mainly studied for the direct flotation of fine minerals, and most of these techniques have not found applications for iron ore slimes especially recovered by the reverse cationic or anionic flotation."

Jan 1, 2018

By Dmitriy Kim, Natalya Ibragimova, Galina Sedelnikova

Gold and copper are lost in flotation tailings in mineral processing of copper-zinc-pyrite ores. Large resources of precious and base metals have accumulated in tailing ponds of Russian plants. Object of the study is the sample obtained from Ural Mining and Metallurgical Company in Russia. The main constituents in flotation tailings are Au, Ag, Cu and Zn with content 1.4 g/t, 12 g/t, 0.66 and 0.5% respectively. The flotation tailings are a refractory material. Gold, as main metal, is fine encapsulated in sulfides, mainly in pyrite. Gold extraction from tailings is 34.0 and 42.7% at P42 and P90 of 0.074mm particle size respectively. In this work heap bioleaching of tailings was studied for oxidation sulfides (pyrite and chalcopyrite) with using mesofilic and moderately termofilic bacteria in acidic solutions. The tailings had low filtration property (< 0.3 m/day) and pelletization was used before bioleaching. Copper containing converter slags flotation tailings and calcium oxide were used as binding material for increasing filtration property of tailings. Copper was extracted in sulfate solution and was precipitated by cementation after cleaning of bacterial solution from iron. Copper recovery was 56.8% at content 61.4% in precipitate. The biooxidation of pyrite was 80%. Cyanidation, leaching with thiourea and heap leaching by cyanide were tested too. Gold extraction from solid bioresidues was 82, 75.3 and 77% respectively. The results of this investigation were recommended for pilot test.

Jan 1, 2014

By Sydney Mantsho, Toni Streczynski, Manuel Gonzalez

"In 2013, the commissioning of the MillStar Stabilisation and FloatStar Stabilisation and Optimisation controllers were completed at the Cerro Bayo Silver (Ag) mine in Patagonia, Chile. The MillStar control system has stabilised the feed to the SAG mill as well as the density at the discharge end of the SAG mill and ball mill. The FloatStar Stabilisation and Optimisation controllers have successfully stabilised and optimised the flotation circuit to ensure consistent product quality within desired specifications.The mill feed is controlled utilising the MillStar Solids Feed controller. Additionally, the solids to liquid ratio into the SAG mill was controlled utilising the Mill Inlet Ratio controller in conjunction with the Solids Feed controller. The discharge end of the milling process is a highly interactive and complex system. The use of a Robust Nonlinear Model Predicative Controller (RNMPC) was ideally suited to control this section of the process. On the Cerro Bayo milling circuit, the RNMPC was used to control the mill discharge sump level and the primary cyclone feed density to produce a more consistent feed to the flotation circuit.Three levels of the FloatStar control system were installed, for flotation stability, concentrate flow stability as well as grade optimisation. The Level Stabiliser was used to stabilise the level control on 6 flotation banks. The Flow Optimiser was commissioned on the Rougher, Scavenger and Cleaner concentrate sumps to stabilise concentrate flow from the flotation cells. The Grade Recovery Optimiser was commissioned on the Roughers section. A number of instrumentation challenges were identified which limited the overall benefit derived from the system. Once these were addressed, the performance was optimised. The overall benefit provided by the system was observed in terms of the improvements in Ag recovery."

Jan 1, 2014

By R. S. C. Smart

Surface chemical factors, including the balance of hydrophobic (e.g. collectors) and hydrophilic (e.g. oxidation products, precipitates) species, are major control determinants in flotation rates of specific minerals and therefore grade and recovery. There are a number of challenges involved with the surface analysis of different mineral phases from process streams in a flotation facility. The first is to collect samples that are representative of the process and retain their surface chemistry prior to introduction into the instrument. The second challenge in studying the surface chemistry of specific minerals is to find reliable methods of mineral phase recognition. In surface analysis of mineral particles, confident mineral selection can be difficult with many multi-metal minerals and with precipitated, adsorbed, reacted and contaminant species in the outermost molecular layers. The third challenge is to provide a statistical surface analysis of multiple grains of the same mineral. Methods to achieve these aims are described. Principal component analysis (PCA) of ToF-SIMS data provides improvement in phase recognition, particle selection and associated variations in surface species. Specific examples from both lab and plant operations, demonstrate that this technique can be utilized to differentiate surface chemical factors promoting (hydrophobic species) or inhibiting (hydrophilic species) flotation. A study of copper ion transfer (inadvertent activation) from chalcopyrite to pyrite and sphalerite clearly identified a statistical difference in copper intensities between the sphalerite and pyrite phases corresponding to their flotation response. The PCA analysis applied to concentrate and tails samples collected from the Inco Matte Concentrator demonstrated extensive CuOH and NiOH transfer between chalcocite and heazlewoodite minerals. The statistical analysis has been able to identify mechanisms controlling recovery and selectivity. High intensity conditioning (HIC) tests in which sphalerite was separated from a complex sulfide ore gave a 5% increase in the overall Zn recovery. The PCA/ToF-SIMS statistical analysis revealed the discriminating depressant action of adherent aluminosilicate (gangue) fine particles and adsorbed ions on the surface of sphalerite grains. HIC conditioning resulted in the removal of these gangue fines improving surface collector attachment efficiency.

Jan 1, 2014

By H. B. Zhou

The process of bioleaching marmatite using moderately thermophilic bacteria has been studied in this research by comparing marmatite leaching performance of mesophilic bacteria and moderately thermophilic bacteria and valuating the effect of venting capacity on marmatite leaching performance of moderately thermophilic bacteria and the effect of pulp densities on marmatite leaching performance of moderately thermophilic bacteria. The results show that moderately thermophilic bacteria have more advantages over mesophilic bacteria in bioleaching marmatite. Aeration agitation can improve the transfer of O2 and CO2 in solution and promote the growth of bacteria and therefore, enhance the leaching efficiency. With the increase of pulp density, the total leaching amount of valuable metals increased, however, the extraction efficiency decreased due to many rea-sons, like increasing shear force that results in poorly growth condition for bacteria, etc.

Jan 1, 2014

By T. Fraszczak, U. A. Peuker, T. Mütze, T. Leißner, A. Wikedzi

The present paper highlights on the comminution and liberation properties of two greisen-type lithium bearing-mica ore blends (L1, L2) subjected to different breakage devices; cone crusher (CC), roller crusher (RC), rotor beater mill (RBM) and a screen mill (SM). The particle size distribution (PSD) of the products from each device were evaluated to search for an appropriate PSD model using Gates-Gaudin-Schuhmann (GGS) and Rosin-Rammler (RR) functions. In order to determine an appropriate function that could better describe the PSDs from the devices used, the coefficient of determination (R2) was used as a criterion. In terms of mineral liberation studies, due to costs, only products from rotor beater mill (RBM) were examined through an automated scanning electron microscope (SEM) technique. It was found that RBM, RC and SM products were better described by the RR model than the GGS model with higher R2 values (0.97-1.0). However, cone crusher products for L1 were better described by GSS model, while that for L2 were better described by RR model. In terms of the spread of size distribution as indicated by RR model parameters, RC products were more uniformly distributed compared to products from other devices, for both ore blends. Also the RBM products were more scattered than products from other devices. The results indicate that the composition of individual ore blends affected the comminution products PSDs since different PSD model parameters were obtained for samples comminuted by same devices. The modal mineralogy of the two ore blends indicate both to be rich in quartz, topaz, zinnwaldite and muscovite. Further, the result indicate that, for both ore blends, zinnwaldite phase is more enriched in the fraction < 250 µm. Moreover, better liberation of zinnwaldite is observed for L1 compared to L2. This could be explained by differences of the two ore blends in three aspects; the nature of mineral association, reduction ratio of the fractions analysed and the nature of spread of the size distribution.

Jan 1, 2018