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By N. Jovanovic, A. Vazirizadeh

"The main objective of this study is to find a solution to design a mass flow observer system with the minimum required sensors and maximum observability for a mineral processing plant. The second objective is designing a mass flow observer configuration with high reliability to manage sensor failures. This configuration will provide a robust monitoring system that increases plant availability and process measurement fault detection. Furthermore, the monitoring system is expected to improve process efficiency. In this investigation, the procedure of designing an observer system is presented along with three models to design the sensor network. The advantages and disadvantages of each models are discussed and finally the models result for an industrial case are presented and analyzed. INTRODUCTION The concepts of observability and redundancy of mass flow are directly linked with the ability to solve and estimate the mass flow. There are hundreds of streams in a process plant flowsheet, and for technical and economic reasons it is not possible to measure all mass flows. It is thus important to know for a set of measured streams, which of the unmeasured streams can be estimated. The concept of observability deals with this issue. It is also valuable to know whether a measured mass flow of streams can be estimated even if a sensor fails for some reason. Redundancy deals with this failure question. A stream is said to be observable if it can be estimated by using the measurements and/ or mass conservation equations. Also, a stream is redundant if it is observable even when its measurement is removed. Observability and redundancy analysis can be exploited for adding new measuring instruments. It can also play a useful role in efficient decomposition and data reconciliation problem (Narasimhan and Jordache 1999). The value of an observer system cannot be justified without considering its benefits. This justification is done through evaluation of data reconciliation, gross error detection and improving process performance such as outlined below:"

Jan 1, 2018

By Christopher Robben, Alexander Mosser

"X-ray transmission (XRT) sorting has been introduced into the minerals industry in 2006 and has found various applications in diamonds, industrial minerals and metal ore processing since. The technology offers planar projections of the atomic density of single particles similar to the principle known from airport scanners, but being capable of treating up to 150tph per metre working width. In 2010, a pilot operation using a belt-type sensor-based sorter went into production at the Mittersill mine to treat the fraction 16-28mm. After an optimisation phase, the results were superseding expectations and therefore in 2012 a bigger production plant was set up. Two XRT-based sorters are parallel in operation since. One is treating the fine fraction 16-30mm while the other one is treating the coarser fraction 30-60mm after the secondary crushing stage. The XRT sorters are operated with the objective to reject barren waste before it enters the mill and flotation plant. 105,000tpa of waste material are rejected per year and can be sold as aggregate for road construction. This means that about 22% of the run-of-mine ore are rejected at an early stage with a waste reject grade lower than 0.03wt%WO3. The installation has not only led to lower specific operating costs but also led to reduced tailings disposal in an environmentally sensitive area. This allows the mine to reduce its headgrade which allows for a longer mine life. Alternatively it is possible to produce more tungsten concentrate, which is delivered to the smelter. This article will introduce the technological principle of XRT-based sorting and will discuss the flow-sheet of the Mittersill mine. Experiences that have led to the current plant design are described as well as the impact it has on the operation."

Jan 1, 2014

By G. Merazchiev

In the selection of copper ? molybdenum concentrates with the use of reagents containing sulfide ion ? sodium sulfide, sodium hydrosulfide etc for depression of copper minerals and pyrites, big part of depressor is oxidized by oxygen, which is dissolving in pulp during aeration with air in flotation machines and it is expended unproductively. This is the main reason for the big expenditures of depressor, reaching up 15~20 kg/t collective concentrate and the high exploitation expenditures for the copper ? molybdenum selection. Effective direction for lowering expenditure of depressor and increasing of the technical ? economical effectiveness of moly production is the conducting of the selection in nitrogen medium. In the paper are shown the results, obtained by applying of this direction in selection of collective copper ? molybdenum concentrate from the porphyry copper deposit ?Ellatzite? ? Bulgaria, in which the ratio Mo:Cu is over 1:120. In laboratory conditions, through comparative experiments in medium of air and nitrogen are defined: expenditure and initial concentration of NaHS in pulp for effective depression of copper minerals and pyrites; kinetics of flotation process of molybdenite; influence of pulp density; emf (negative milivolts) of pulp and the expenditure of nitrogen on tech-nological indexes of molybdenum flotation. When working in nitrogen medium decrease of NaHS in rougher molybdenum flotation from 40% to 45% is settled. When nitrogen is also fed in cleaner stages, the total expenditure of depressor is lowered by 64%. The quality of end molybdenum con-centrate is raised with over 5%. On the ground of the results of laboratory studies and of world practice data, an industrial installation for selection of copper ? molybdenum concentrate in nitrogen medium in Wemco inert ? gas machines.

Jan 1, 2014

By M. Saghaeian, R. Hejazi, A. Dehghani Ahmadabadi, M. Zare

"In the most iron ore beneficiation plants, reverse flotation is the best method for removing silicate gangues from final iron ore concentrate. Many previous studies show, if the major portion of impurities include quartz minerals, the flotation process is simple, but if iron silicates are dominant, reverse flotation is so complicated and mostly not very effective. In this study which was performed on the Sangan iron ore concentrate, the performance using of reverse flotation and magnetic flotation separator for elimination of silicate gangues from the magnetic iron concentrate was investigated. The operational parameters for reverse flotation are considered as: collector and frother types and dosages and also modifiers. But for magnetic flotation separator parameters were magnetic field intensity as well as overflow and underflow water rates. Results showed that reverse flotation has not a significant effect on the elimination of impurities. Because of the silicate gangues of Sangan concentrate including a mixture of quartz and iron silicates (amphibole, pyroxene and feldspar), so downgrading of the SiO2 content for the flotation concentrate was rather low and only average reduces of 20.60% were possible. But the findings of using magnetic separator was more satisfactory. Results of the weight recovery, iron grade and also SiO2 and S grades of final concentrate were better with magnetic flotation device. So at the best and optimum condition, we could reduce 51.01% of the total silicate (SiO2~ 2.19%) along with 74.66% of sulfur content (S~ 0.076%) and concentrate weight and Fe recoveries of 92.04% and 94.51% respectively, final Fe grade of 68.73%.INTRODUCTION Chemical/traditional flotation is one of the most effective methods for separating valuable particles from waste minerals, which is used in most mineral processing industries. In the iron ore processing industry, the major impurities present in iron ore concentrate include sulfur, silica and phosphorus (Bruckard et al, 2015), which are often carried out by reverse flotation methods for the removal of sulfide and oxide impurities (Donald, 1967: Araujo et al., 2005: Ma, 2012)"

Jan 1, 2018

By Bertil I. Pålsson, Sture V. Persson, Kent T. Tano

"Grinding is one of the most energy consuming unit operations and is also a very inefficient and costly process. Therefore, it is of great importance to run the grinding process as efficiently as possible. The most common way today to control grinding processes is by measuring the power draw of the mill and try to keep it at a maximum level. However, some studies (Kawatra, 1989, Koivistoinen, 1989, Moys, 1989) have shown that this measurement doesn.t reflect everything that takes place inside a mill. Among other parameters like slurry rheology, temperature and charge behaviour, the volumetric filling of a grinding mill seems to have a large influence on the grinding efficiency (Herbst, 1988, Koivistoinen, 1992, Vermeulen, 1988). A problem in attempting to measure those parameters has been to get a sensor that is both robust and sensitive enough for continuous on-line measurement.This paper presents a method for the measurement of the apparent filling level in a pilot ball mill equipped with the Metso Continuous Charge Measurement system (CCM). In this technique a strain gauge sensor is mounted on a flat steel spring which is fitted into a recess underneath a lifter bar. In addition, a conductivity probe, the Boliden Grinding Measurement System (GMS), is mounted in another lifter bar with the purpose of comparing the two measurements. To visualise the behaviour of the charge a DEM modelling technique is used.The results indicate that the system is capable of following the normal variation that occurs in the mill. The signal also very well reflect changes in operating variables such as ball charge level, pulp density and rotational speed. By studying the nature and different features of the signal one can get a better understanding of milling circuit dynamics. Another feature of the technique is the possibility for an operator to continuously follow the grinding process and thereby run the process under optimal conditions."

Jan 1, 2003

By U. S. Chattopadhyay

The estimated requirement of the nation by the year 2020 is approx. 80 Mt of steel and more than 0.2 million MW installed capacity of the electricity, thereby increasing the consumption of the coking and non-coking coal, which is expected to be in tune of about 75 Mt & 500 Mt respectively. One of the major deleterious factors in achieving the goal is the deteriorating quality of the feed coal used in both steel and power industries. Indian coking coals, in general, are typified by high ash, high inert (both organic and inorganic), low rank, low reactive macerals content, heterogeneous petrographic make-up, inferior coking properties and poor amenability to washing, thereby necessitating suitable washing measure. Coke-based steel industries in India require washed coking coal containing ash % varying between 17-19. The situation demands taking on immediate challenges to fill up the gap between the requirements and supply of coking coal. This paper reviews the R&D attempts in this laboratory and throws light on the key measures as long-term solution to the problem. Search for alternative source of coking coal, like LVC coal and their judicious preparation technology. The low volatile coking coal (LVCC) constitutes about 50% of the total coking coal reserves in India. These coals are characterized by high raw coal ash content (37 to 40%) and very difficult washability potential. If these coals are treated in the existing washeries, which are generally 2 or 3-product systems, the cost of clean coal is high as the byproduct sale value is low. It has been proposed to produce a new type of by product, which enjoys high demand and good coking properties.

Sep 1, 2012

By Alex Joseph

A tertiary amine containing polyamine in its back bone was grafted to exfoliated graphite oxide by means of a series of chemical reactions.The synthesized amine functionalized polyaniline grafted to exfoliated graphite oxide (EGAMPANI) was characterized using various techniques such as, FTIR, TGA, Raman, and X-Ray diffraction.The synthesized EGAMPANI was blended with carbon paste electrode, and used to study the response of Hg2+ in acetate buffer solution.Preliminary analysis showed that the anodic current intensity using the EGAMPANI modified electrode was higher during a potential sweep and 10-4 M concentration of mercury could be detected which could be improved to 10-6 M using anodic stripping voltammetric technique. Keywords: metal sensor, exfoliated graphite oxide, functionalization, polyaniline

Sep 1, 2012

By Arkady Senchenko

At present, there are different traditional and modern methods for ore grindability evaluation. The correct and rational approach to sampling, testing methods and mill sizing enables one to design a workable technology. This paper contains TOMS institute experience in different grinding indices determination over the last 7 years (SAG Design Test, BWi, CWi, RWi, and other). Mill sizing examples and circuits modeling for the projects in Russia and Kazakhstan are considered. Keywords: ore grindability, SAG Design Test

Sep 1, 2012

By H. R. Manouchehri

Large variations in flotation characteristics of minerals have been observed in winter and summer in plant practices as a result of changes in pulp temperature. Variations in temperature may affect the quality for pulp and related process water through changes in dissociation of different chemical species within the pulp, as well as changing in gas and metal hydroxide solubility, reagent adsorption and its stability on mineral surfaces, water/pulp viscosity, etc. All of these affect the flotation characteristics of specific mineral to some degree or another. It has been observed in Cu-Pb-Zn and/or Pb-Zn sulfides flotation that sphalerite (ZnS) flotation is strongly affected by changes in pulp temperature. Plant practices have shown that at the both low, e.g., T <10-12°C, and high, e.g., T > 60°C, the recovery for copper activated sphalerite is dramatically dropped. Within this paper the effect of pulp temperature on flotation characteristics of sphalerite is brought into considerations and laboratory flotation tests were conducted in conjunction with surface and solution chemistry analysis to understand the effect of temperature on sphalerite recovery. The effect of temperature seems to be complex since the temperature affects both the physical (hydrodynamics) and chemical phenomena in the flotation cell. In fact all sub-processes in flotation, i.e., collision, attachment and detachment, are affected by changing in temperature. Experimental results indicating that at alkaline pH values, e.g., 8.5 to 10.5, the recovery for copper-activated sphalerite is dramatically reduced when temperature is below 10-12°C, which is in agreement with plant practice at Boliden?s Garpenberg plant in Sweden. However, results from other studies indicated that the zinc recovery is also considerably decreased at high pulp temperatures, i.e., 62°C and above.

Sep 1, 2012

By Lj. D. Andric

By the micronization-milling of the material, the size and the structure of its particles are changed and it comes to the increasing of the potential energy of the system as well as to the chem-ical activity of the material what is the result of an increased free surface and of the concentration of the grate defects, that is of the internal energy of the system. All these changes that are reached, show that new characteristics of treated materials are got by micronization process. Controlling the process of the micronization and by purpose directing of the new characteristics of the activated materials, we can have the positive effects and use them in more technologies. Talc is important nonmetallic mineral raw material that is widely used as either the basic raw material, or as filler. This has stimulated its technological investigation, as well as the investigation of its physical-chemical characteristics. In this paper are shown experimentally reached results of the physical-chemical characteristics of the talc during the process of the micronization in high energetic mill. In this paper, the optimum conditions of miconization of talc in high-energy-speed rotary mill and its influence micronization on a degree of Fe2O3recovery by hydrometallurgical methodes, are presented. The X-ray analysis of the obtained products showed that high quality talc with low content of can be obtained by these physical-chemical processes In this paper, the principles and application or fine and ultra-fine grinding high-energy attriton mill with small balls, enabling fast, efficient grinding, low energy consumption, short grinding time and easy handling will be described.

Jan 1, 2014

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 Y. G. Seredkin, A. A. Vasiliev, A. Y. Senchenko, A. V. Aksenov

"The valuable materials resulting from the processing of gold-bearing ores are often refractory to direct gold recovery through cyanidation. There are multiple methods for chemical liberation of gold prior to cyanidation such as pressure and biological oxidation as well as atmospheric oxidation which is typically used in combination with physical activation of material by ultrafine grinding such as the Albion ProcessTM. This paper will examine the data from process testworks carried out to estimate the efficiency of the Albion Process™ for the oxidation of materials with a wide composition range prior to cyanidation. The data will be compared to that obtained by direct cyanidation of the feed (without oxidation) and from the testing of pressure oxidation on the feed prior to cyanidation. Albion Process™ tests were conducted in Institute TOMS with participation of Glencore Technology Pty Ltd (Australia). Refractory concentrates obtained from the ores of several Russian and CIS deposits were used as feed for the testing. These concentrates were also subjected to a material composition study and testing using conventional recovery methods. The resulted test data make it possible to perform an integrated assessment of process properties for materials with different compositions, compare performance of various process flowsheets for the materials under study, and conclude on efficiency of Albion Process™ application for gold recovery from refractory materials different in their composition.INTRODUCTION It is often the case that gold ore concentrates are refractory to gold recovery by direct cyanidation. This refractory nature is as a rule attributable to fine gold dissemination in minerals, most often in pyrite and other sulphides, as well as to the increased amount of components impeding cyanide leaching of gold due to cyanide consumption and reducing process conditions. The refractoriness of the concentrates results in low gold recovery values when conventional cyanidation technology is used. In this context, various additional processes are applied to breakdown such refractory sulphide concentrates, i.e. mechanical breakdown (fine and ultrafine grinding), chemical breakdown (atmospheric oxidation, e.g. Leachox, acid-oxygen oxidation, pressure oxidation – POX, bacterial oxidation – BIOX), and thermochemical breakdown (various roasting methods). Such breakdown processes allow for increase in recovery of finely disseminated gold during the downstream cyanidation, however, their application is cost-intensive and does not always ensure economic benefit."

Jan 1, 2018

Cyanide is reactive to copper minerals and is not suitable to extract the gold from the copper bearing ores. Ammoniacal thiosulfate is considered an excellent alternative lixiviant for leaching copper bearing gold ores. Unfortunately the results of high reagent consumption and poor gold ex-traction were found by thiosulfate leaching of synthetic gold ores containing chalcopyrite, chalcocite or bornite and a mild refractory copper-bearing sulfidic gold ore. In this investigation, several processes have been applied to reduce the impacts of these minerals on gold leaching. The process included: the pre-oxidation of copper sulphide minerals in water or ammonia solution, the reduction of dissolved oxygen in the lixiviant (0.3 ppm DO or 0.7% oxygen), adding phosphate anion in the leach or pre-leach stage, and the addition of a strong copper ligand (e.g., EDA and DETA). The results indicated that the gold extraction could be improved to 93% with the thiosulfate consumption being reduced to less than 8 kg/t. The dissolution of copper minerals was found to be the major reason for increased consumption of thiosulfate and the highly reductive leached surfaces are responsible for the reduced gold extractions.

Jan 1, 2014

By S. Narra, M. Nelles, I. Eickhoff, S. Teitge

"The aim of the research is to develop a holistic process flow for the recycling of glass fibres from glass reinforced plastics (GRP) and carbon fibres from carbon fibre reinforced plastics (CFRP), wherein the dissolution of the fibre epoxy resin matrix, separation of fibre fractions and their renewed material use is intended. In clear distinction to the previous research and development projects, the aim here is to recycle complex composite structures such as dismantled/disused wind turbine rotor blades and end-of-life composite wastes. In the course of the study, mechanical, hydrothermal and thermal processes and their combined procedures will be developed. As the fibre length is a decisive quality criterion in the recycling of composite materials, the further focus of the study will be the development of upstream and downstream material processing, in which the fibres are retained in their original form. The evaluation of the recycled fibres obtained is based on the elemental composition, measurement and morphological evaluation of individual filaments by scanning electron microscope (SEM), micro tensile tests on single fibres and their comparison to virgin fibres. The resulting process water is analysed by gas chromatography and mass spectroscopy (GC-MS) and a potential recirculation is determined. In cooperation with companies from the composite processing industry as well as recycling companies, a return of the recycled fibres to the known manufacturing process will be examined and an energetic and economic evaluation of the overall process will be carried out. Ambitious aim of the study is to achieve an actual recycling instead of the present downcycling or the energetic utilization. INTRODUCTION As global warming increases, so does the awareness of consumption and production of energy. To counteract the effects of global warming, renewable energy has been increasingly used during the last two decades, not only in Germany, but worldwide. Both, hydropower and wind energy, hereby play a fundamental role. After the end of their useful life of 20 to 30 years, the wind turbines (WTs) are being dismantled. Due to their foundations and tower segments, their recycling rate hereby exceeds 90% by mass. So far, the resulting rotor blade waste played a minor role accounting for only 2 - 3 weight-% of the total plant. Rotor blades of modern wind turbines are made of glass and carbon fibers, which are embedded in an epoxy or polyester resin matrix, balsa wood, PU or PET foams as fillers as well as various paints and coatings. These wastes currently end up in waste incineration or are sold to non-European countries."

Jan 1, 2018

By Junwei Han, Wenhua Li, Wenqing Qin, Fen Jiao, Wei Liu, Jiaqi Xu

"A novel technology was developed to study the process of recycling copper from waste printed circuit boards (WPCBs), which are the main source of metal production in the next decades. The chemical compositions of the WPCBs were investigated. The results indicated that the PCB powder was mainly composed of copper (38.5 wt.%), iron, aluminum, and non-metallic materials. Copper is mainly in the form of Cu and is the most valuable metal for the recycle of WPCBs. The concentrated WPCBs powder, obtained by the mechanical process, were pressed as the anode, which was directly electrolyzed to produce copper. The effects of H2SO4 concentration, Cu2+ concentration, current density, pole pitch, and liquid-to-solid ratio on the voltage, current efficiency, and copper extraction were investigated. The results indicated that the optimum conditions were liquid-to-solid ratio of 30 mL/g, current density of 571 A/m2, sulfuric acid concentration of 180 g/L, 50 g/L of copper ion, polar distance of 3 cm. Under the conditions, a desired current efficiency could be achieved. Meanwhile, about 95.62% Cu was recovered from the WPCBs. The experimental studies also revealed that the purity of copper obtained at the highest current efficiency was higher to 99.98%. Produced copper sheet were characterized by X-ray diffraction (XRD). XRD analysis indicated that the copper was the main phase. INTRODUCTION With the rapid development of electronic industry, more and more waste electronic and electrical equipments (WEEE) are generated every year (Fogarasi et al., 2012; Liang et al., 2013). The production of printed circuit boards (PCBs) is the base of electronic industry, because it is the essential part of all electrical and electronic equipments (Schlummer et al., 2007). As a result, a considerable amount of waste PCBs containing plenty of heavy metals have to be treated. In general, PCBs contain about 28% metals that are abundant non-ferrous metals such as Cu, Pb, and Sn. Printed circuit boards can be considered as a secondary resource for recycling rather than wasting. The contents of gold and silver respectively reach 80 g/t and 3300 g/t, which are much higher than that of primary ores. Copper is the main metal of PCB and its content is as high as 26.8% ( Zhang et al., 2009)."

Jan 1, 2018

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

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

Jan 1, 2018

By L. Semushkina

Next generation flotation agents of KSK series for the concentration of complex copper-lead ores and the new ferromagnetic nanosized depressor of galena are introduced in this work. The feature of the KSK flotation agents is that they exhibit both frother and collector properties. KSK-6 can successfully substitute the widely used in Kazakhstani industry reagent ?-80 at the reduced consumption of butyl xanthate by 30 %. The new ferromagnetic nanosized depressor of galena, besides a low consumption rate of 100 g/t, also makes possible to exclude sodium sulfite (3-4 kg/t) and ferrous sulfate (5-6 kg/t) from the separation process, and receive high metal grade concentrates. Keywords: complex copper-lead ore, flotation agent, concentration method, ferromagnetic nanosized depressor

Sep 1, 2012

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 A. Singh, M. Ntlhane, V. Ross, M. Dlame

"Fine valuable particles are often lost to flotation tailings streams due to inefficient collection by air bubbles as well as passivation of surfaces by oxidation and slimes. The application of high-shear hydrodynamic cavitation devices (HCDs) to overcome this problem has already proven to be a considerable success in the industry. This paper details the results of further investigations that were undertaken at Mintek to better understand the mechanisms involved when preconditioning feed slurries in an HCD. By promoting inter-particle attrition and conditions of high shear within the reactor, cleaning of particle surfaces is enhanced as well as the formation of superfine (nano) bubbles which are believed to aid their agglomeration and subsequent collection by normal sized bubbles. In order to broaden the envelope of understanding with regard to application of the technology, rather than tailings material as investigated earlier, a Platinum Group Mineral (PGM) UG2 ore from the Bushveld Complex in South Africa was used in this study. The results of a series of batch flotation tests in a 10L Denver cell are presented, being conducted after the feed has been subjected to different methods of preconditioning. It was demonstrated that the preconditioning significantly improved the flotation kinetics of the PGMs, the optimum being obtained after around 20 passes through the reactor. This was accompanied by a much enhanced recovery-mass pull relationship and a significant improvement in the grade-recovery response. Significantly, the selectivity between the PGM and the deleterious chromite (expressed as Cr2O3) gangue more than doubled under these conditions. Modelling of the PGM data by means of the modified Kelsall model indicated that both the fast and slow floating rate constants were improved.INTRODUCTIONIt is well known that the flotation recovery of fine and ultrafine particles, typically less than 10 micron in size, is a challenge (Yoon et al., 1989; Miettenin et al., 2010). Although these particles are typically well liberated, due to their very low mass and inertia, the collision efficiency with air bubbles is low as a result of the inability of particles to penetrate the liquid streamlines around bubbles. Hence the probability of contact is often regarded as the ratedetermining step in flotation of ultrafine particles. Introducing more power into conventional flotation machines is likely to solve only part of the problem, as conventional mechanisms are effective only to a point in terms of shear and micro-turbulence. Further challenges are posed by the treatment of low-grade or oxidised tailings dump material, where valuables are passivated due to prolonged exposure to the atmosphere or slimes. Over the years, various mitigating strategies have been investigated, including the use of dissolved air flotation (Martinez-Gomez et al., 2013; Calgaroto et al., 2015), shear flocculation (Subrahmanyam and Forssberg, 1990), seed or carrier flotation (Tabosa and Rubio, 2010), sonication to clean particle surfaces (Aldrich and Feng, 1999; Newell et al., 2006), high intensity conditioning (Bulatovic and Salter, 1989; Chen et al., 1999; Tabosa and Rubio, 2010), and various electrochemical approaches such as changing Eh in order to promote formation of dixanthogen, dissolution of oxidation products by lowering the pH, activation by sulphidisation (Newell et al., 2006; Becker et al., 2014), and the use of alternative collectors."

Jan 1, 2018

By O. N. Mohanty, S. Mohan Rao, N. D. Rao, T. Mukherjee, P. V. T. Rao

"Tata Steel has its captive chromite resources at Sukinda, Orissa. They contain two ore types, i.e. (i) Ferruginous and (ii) Siliceous. The generation of off-grade ores is an increasing trend and simultaneously customer quality requirements are becoming ever more stringent. The ferruginous type ore also contains a considerable quantity of in-situ fines (~20% particles below 0.5 mm) that compound the beneficiation problem.In this paper, new strategies are discussed for producing additional value.added products after evaluating the present beneficiation practice in terms of changing market scenario, processing capability of the plant and ore characteristic. They would entail use of MGS - an enhanced gravity separator, for recovering additional products from plant tailings; production of ferruginous coarse concentrates (-3+0.5 mm with ~46% Cr2O3) using jigs; production of marketable grade lumpy (-40+10 mm size) concentrates from low grade siliceous ore using jigs and >2.8 Cr/Fe ratio siliceous ore fines treated in the Chrome Ore Beneficiation plant gravity circuit units and low intensity magnetic separator. The studies indicate that it is possible to recover 79-80% of the chromite, against a theoretical maximum of 82% from both the ore types, in the form of several marketable grade concentrates that would also include refractory grade."

Jan 1, 2003