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By Venkata S. Buddhiraju

Pelletization of iron ores involves balling on a rotating disc to produce wet pellets and induration of wet pellets on a moving grate to produce fired pellets. The quality of pellets produced and the productivity of the pelletization process depend strongly on the characteristics of the feed to the pelletization disc, especially the particle size distribution and the moisture content. The upstream processes involved in the preparation of pelletization feed include grinding, thickening and filtration of the iron ore slurry. The focus of the present work is the closed circuit wet grinding of iron ores. The circuit consists of a primary ball mill, a regrind mill and a hydrocyclone. A population balance model was developed to predict the grinding kinetics and an empirical model was fitted for the separation of fine particles from the coarse particles in the hydrocyclone. Batch grinding kinetics experiments were performed on a laboratory scale ball mill to obtain the ore breakage parameters which were subsequently used for the simulation of the industrial mills. The models were customized for the industrial operations and the effects of different process variables like feed flow rate, water flow rate, etc., on the size distribution of product from the grinding circuit were studied. Additionally, different circuit configurations were simulated to determine operating conditions that could result in the desirable product particle size distribution. The results of simulation were in close agreement with plant observations and the new circuits explored through simulation have helped in identifying potential opportunities for process optimization and control

Sep 1, 2012

By Leon Lorenzen, Rodrick M. Lamya

"Leaching behaviour of nickel – copper matte in a CuSO4–H2SO4 solution during the repulping stage of a matte pressure leaching process has been studied. The base metal recovery process investigated in this study consists of a matte repulping stage prior to a series of pressure leach stages. The repulping stage is essentially an atmospheric leach stage in which the Ni-Cu matte, containing small amounts of cobalt and iron, is leached in copper spent electrolyte from the tankhouse, resulting in dissolution of the nickel with simultaneous precipitation of almost all the copper.Effects of various process parameters on the kinetics and extent of the leaching reactions, as well as on the cementation of copper from the solution have been quantified. The parameters investigated were temperature, particle size, pulp density, stirring speed, residence time, initial copper concentration and initial acid concentration.Leaching characteristics of the preleached matte during the subsequent pressure leach operation has also been studied. The effects of variations in the conditions in the repulping stage on the kinetics and degree of base metal dissolution during the pressure leach stage have been investigated. Any transformations that occur in the mineral phases of the matte during the leaching process have been studied, and a leaching mechanism proposed."

Jan 1, 2003

By L. J. Li, Q. Zhang, Z. H. Liu, Q. L. Chen

Phosphogypsum (PG) is an industrial waste from the production of phosphate fertilizer. The utilization of PG is restricted by its containing impurities, and the pretreatment is crucial to eliminating these impurities. The purpose of the research is to recycle pretreatment PG as raw material for preparation of a-calcium sulfate hemihydrate (a-HH) by salt solution method. The effect of pretreatment technologies of lime neutralization and washing on dehydration rate, phase composition and morphology evolution of a-HH were investigated by crystal water content analysis, XRD and SEM. Furthermore, the change of pH in the reaction process was also discussed in detail. The results show that the dehydration rate of conversion PG to a-HH increases and the corresponding induction period, crystal growth period and total time decrease with an increase in CaO dosage from 0.2% to 0.6%. In the presence of 0.4% CaO or 0.6% CaO, the a-HH presents a long hexagon-prism-shaped crystal with a purity of 94%, and the end face of a-HH presents polyhedron. The system pH sharply decreases with the reaction time under different CaO dosage, and the pH variation from the initial alkalinity to acidity. The main reason is that as the co-crystallized phosphorus dissolved and released HPO42-, and with the pH decreasing to 4-5, HPO42- transformed into H2PO4-. The dehydration rate of washing PG is lower than that of original PG. Compared with the original PG, a-HH with the larger width and smaller aspect ratio can be achieved from the pretreatment PG subjected to lime neutralization and washing, meanwhile the crystal surface is more smooth.

Jan 1, 2018

By Igor P. Solozhenkin, Peter M. Solozhenkin, Sanda Krausz

"In this work, authors will show the efficiency of computer technology and chemical programs at studying collectors for flotation of minerals of elements of platinum group (EPG). Clusters various minerals EPG (flotation reagents) are created, named us clusters minerals (reagents) as their structure corresponds to the chemical formula, and the distance between separate atoms corresponds to the known tabulated data. By molecular modeling are investigated clusters sperrylite PtAs2, stumpfilyte PtSb, sadberryte PdSb, sobolevskite PdBi, palladoarsenyte Pd2As, paolovyte Pd2Sn, rustenburgyte (Pt3Sn, Pt6Sn2) and their computer parameters (absolute rigidity, electronegativity, transfer factors of carry, charges of the atoms) are determined. Tellurides of palladium (IV, II) merenskyite PdTl2 and kotulskyte PdTe and platinum clusters are investigated: PtFe4, Pt3Fe, PtFe (Pt2Fe2), Pt2Fe (Cu) Ni. The technique of attachment of the collector (composites) to cluster atoms EPG is offered. For the first time, it is established that at linkage of flotation collectors on monodentate, bidentate and bridged to circuits with atoms clusters the minerals containing atoms As, Sb, Bi, Pb, Sn, reaction of connection with change of a degree of oxidation of these atoms and occurrence of a proton operates. It is executed virtual skirling organic compounds connections by the developed criteria from accessible libraries of a database. The principle of an estimation of interaction energy for flotation reagents with mineral clusters is offered. It is developed the prognosis of collector activity evaluation (P?AE) and his values for candidates in collectors for flotation of minerals EPG are calculated. For flotation of ores containing Pt and Pd minerals, a number of reagents, including compounds on basis P (III), for innovational technology of Pt, Pd mineral flotation are recommended. Key words: flotation, minerals, flotation reagents on the basis of phosphorus (III), molecular modelling, chemical programs, program ????? , electronic energy."

Jan 1, 2014

By Vladimir E. Vigdergauz

"Bubble-mineral complexes could be formatted by an attaching of hydrophobic particles to the surface of air bubbles or by an evolution of bubbles from solution onto hydrophobic surfaces. Measurements of contact angles, detachment forces (DF), induction times (IT), evolution pressures (EP) and flotation recoveries (FR) for the studying of minerals wettability at various pH and electrochemical potentials were used. An analysis of the obtained IT results show that a process of bubble attachment to a mineral surface is a rather slow one and it will scarcely be enough for bubble-mineral complex formation under the conditions of real flotation.The ranges of adhesion potentials obtained by DF measurements, Figure 1, correlate with the data of floatability-potential for pyrite. The ranges of adhesion potentials obtained by DF measurements for galena (-1 ÷0.2V) and chalcocite (-0.5÷1.2V) correlate with the potential ranges of floatability for galena (<0.2V) and chalcocite (>-0.4V). An increase of the DF and the cathodic limit of the adhesion potential with increasing length of the hydrocarbon chain were observed. EP-pH curves for sulfides are a mirror-like to the DF-pH curves, Figure 2. Structure of solid-liquid and liquid-gas borders has a determinative importance for formation of bubble-mineral complexes and subsequently flotation results. Under vacuum on the mineral surface there are produced micro bubbles and preferably they will be appeared on the hydrophobic sites. Water structure breaks near a hydrophobic surface facilitate water mass destruction and formation of gaseous phase embryos under decompression in the impeller zone. It simultaneously reduces a probability of produced micro bubbles dissolution as a result of pressure increasing owing to constant fluctuation of liquid densities into impeller zone. Comparison of Taggart’s evaluation of the suction behind blades of the impeller of an agitation-froth machine and ABEP data on galena, Figure, shows that gas evolution will be observed in the range of 1300-2700 revolutions of impeller per minute for hydrophobic and hydrophilic surfaces successively."

Jan 1, 2003

By S. N. Shahcheraghi

Grinding is one of the most important and expensive steps in mineral processing allocating about 70% of the total energy in the plants. Nowadays, for optimizing the energy consumption in these equipments, the rock behavior and its size distribution during the crushing have been normally predicted using selection and breakage functions to be able to optimally model and design grinding circuits. For this purpose, the case of Miduk copper mine in Kerman province, Iran was studied. The samples were taken from primary ball mills feed and were subject to screen analysis to achieve uniform sizes. Then, selection and breakage functions were determined at the different grinding times in laboratorial ball mill. Finally, ore size distribution in different grinding times was estimated using MATLAB software

Sep 1, 2012

By Heikki Häkkänen, Tommi Kauppinen, Navid Khajehzadeh

"There are a variety of methods suitable to analyse elemental and mineralogical contents of rock drill core samples. Current demands are on fast exploration and objective analysis of ore samples. This paper proposes a combination of Laser-Induced Fluorescence (LIF) and image processing, entitled LIF-imaging, as a potential method for automated mineral analysis of the drill core samples. It is shown that LIF-imaging can produce a mineral map of the fluorescent minerals existing on the surface of the drill core samples. The test cases are drill core samples from a Ni-Cu mine situated in Kevitsa, Finland. The main prerequisite of LIF-imaging technique is a reference data, linking colours to the minerals. This study describes the calibration of LIF-imaging technique using precise but slow Raman spectroscopy. Using regularized logistic regression, a model is obtained that classifies the minerals based on their emitted fluorescent colours in the digital images. The abundance of each mineral group is estimated by pixel counting. The results are compared with X-Ray Diffraction laboratory assays performed on the same samples. The results show that the interpretation of the fluorescent minerals through LIF images corresponds to the XRD results. Furthermore, the utilization of the logistic regression to interpret the existing fluorescent minerals greatly improves the technique."

Jan 1, 2014

By S. J. Neethling

"Liberation is a key driver in all mineral separation processes as it limits the maximum possible grade for a given recovery. In flotation, this is further complicated by the fact that it is surface exposure of the floatable minerals that determines the ultimate performance. Liberation, grade and surface exposure are commonly quantified using Scanning Electron Microscopy coupled to Energy Dispersive X-ray spectroscopy (SEM/EDX) analysis of polished sections. The intrinsically 2D nature of this technique can result in significant sampling errors and stereological effects that can affect the quantification of the ore’s textural characteristics. X-ray micro-Tomography (XMT) is an imaging method that can non-invasively and non-destructively delineate ore fragments in 3D, thus providing an alternative method that eliminates the need for stereological corrections and readily provides surface exposure. A methodology and automated algorithm were designed for extracting this information from images of closely packed particles, thus allowing samples containing a large number of particles to be assessed.The main drawback of XMT is that, unlike SEM/EDX, it cannot directly measure the mineralogy of the sample, instead producing a 3D X-ray attenuation map. We therefore also present an algorithm for calibrating the thresholding of the XMT images based on SEM/EDX images of sections through the same sample, thus allowing the liberation analysis to be carried out on a 3D mineral map in which the uncertainty in the mineral assignment is small and statistically quantified.The methodology was tested on low grade porphyry copper ore as this is both an industrially relevant and traditionally difficult system to quantify using XMT due to the similarity in the X-ray attenuation of the sulphide species, especially the pyrite and chalcopyrite. As each 3D volume imaged contain 100-1000s of grains, large data sets can be readily produced. By dividing these particles into classes based on both their surface exposure and grade, the extent to which there is preferential breakage of the particles can be assessed—an important consideration if sufficient surface liberation for good flotation performance is to be achieved at coarser particle sizes. It is also shown that erroneous conclusions can be drawn when basing the analysis on 2D sections through the particles."

Jan 1, 2018

By X. H. Zhou

Column flotation is being widely adopted for fine particle treatment by the mineral processing industry due to its simplicity of structure, high efficiency and good separation performance. Cyclonic static micro-bubble column flotation (FCSMC) is an innovative column separation technology that has been successfully applied in the coal preparation industry in China. Recently, the application of this equipment has been further expanded to the separation of several minerals such as fluorite, copper, iron, etc. The bottom of the FCSMC is a cone in which cyclonic field is generated when circulating pump is injected tangentially into the column. The unique cyclonic structure is believed to help enhance the column separation performance. Since the FCSMC is a new flotation device, little work has been done to understand the fundamentals of this technology. In this research, a computational fluid dynamics software, ANSYS/ FLOTRAN, was employed to simulate the flow field of a lab FCSMC system (F0.2 m, F3.0 m by length.) The distribution patterns for velocity field and flow field were investigated under single phase condition. It has been found that axial velocity of the slurry decreases and becomes stable along the height of the column from bottom to top, and the slurry performs as a descending flow pattern. Another observation is the velocity fluctuates vigorously near the wall due to wall effect. Compared to axial velocity, the radial velocity distribution is smaller and more complicated. The basic pattern is that on a given cross section of the column radial velocity increases from the wall to the center and it the velocity changes greatly around the center. Under the condition of column height less than 0.8 m, the axial velocity is negative and it directs from the wall to the column axis. When column height is higher than 0.8 m a reverse pattern is obtained, i.e., axial velocity is positive while directing from column axis to the wall. Special efforts were directed to investigate the tangential velocity pattern. Results indicate that the tangential velocity patterns of different cross sections are similar and showed a symmetrical distribution. Tangential velocity distribution concluded two zones: outer whirlpool and inner whirl-pool. And, interestingly, it has been found that on different cross sections the highest tangential velocity always occurs at the same position of the cross sections.

Jan 1, 2014

By Muammer Kaya, Sait Kursunoglu

"Energy is the major concern for society. It is expected that developing country economies and populations will grow and consume more energy. Interest in nuclear power is rising, while the world looks for non-depletable energy source that will not contribute to global warming. However, it still has concerns of nuclear proliferation, radioactive waste and safety. It is necessary to overcome these concerns if nuclear energy is expanded to developing countries. Thorium (Th) utilization as nuclear fuel will be an opening key of these difficulties because Th produces less Plutonium (Pu) and less radioactive waste with enhanced safety. Research into the use of Th as a nuclear fuel has been taking place over forty years, through with much less intensity than that for uranium (U) or U-Pu fuels. Nuclear industry is currently using only 0.7% of the available energy from mined U. With huge resources of Th and relatively little U, Turkey has made utilization of Th for large-scale energy production a major goal in its nuclear power programme. Thorium fuel is plentiful and inexpensive. Energy is major concern for developing Turkish society. Turkey, today exports more than 70% of its energy as fossil fuels. In the last 50 years, Turks are skeptical, anxious and indecisive about having nuclear energy for electricity production. In the last 10 years, Thorium is brought into Turkish government’s attention and national discussion as a new, safe, clean, affordable, CO2-free, alternative, strategic and domestic nuclear energy fuel. Turkey recently contacted four VVER-1200 type Russian Nuclear Power Reactors using U as a fuel in Akkuyu (Rosatom) and another four units will be established in Sinop in the next decade by Japan (Mitsubishi-Westinghouse). Turkish nuclear programme must envisage use of domestic Th as a fertile material. This paper briefly reviews the developments of Th-fuel cycle for nuclear energy from global and Turkish perspectives. Previous Th reserve development and recovery studies from Turkish bastnasite ore are summarized in this paper."

Jan 1, 2014

By H. U. R. Kattentidt, W. L. Dalmijn, T. P. R. de Jong

"Research at Delft University aims to develop systems for automatic inspection and sorting of bulk solids which can be applied in the mineral processing and recycling industry. A recent development includes an automatic sorter based on airport X-ray inspection technology. It is designed for continuous inspection and sorting of 5 – 150 mm solids and has as objective a cost effective and high capacity on-line inspection and sorting.Dual energy X-ray transmission imaging provides instantaneous data about particle dimensions and the atomic number distribution. The system provides particle thickness and average atomic number on a pixel level at scanning speeds between 250 and 500 lines / second. With existing X-ray components inspection speeds between 0.5 and 2 m/s at approximately 1-meter inspection width and between 1.5*1.5 and 5*5 mm2 sensor resolution can be achieved.Imaging algorithms that were developed by Delft University for applications in recycling, waste cleaning and other applications acquire shape, size distribution and composition data. Currently on-line processing of a product at a rate of around 200 particles per second is possible using a standard PC. Experiments with a demonstration X-ray unit indicated good potential for various applications in solids processing. They include continuous inspection of organic content, sulphur, chlorine, ash, and metal distribution. It is applicable for coal cleaning, ore sorting, industrial minerals, and various applications within waste cleaning and recycling. Dual energy X-ray transmission fundamentals and recent progress in system development and applications are presented."

Jan 1, 2003

By Y. Q. Qui

In the bauxite flotation process for desilication, the middling treatment mode is the important factor to raise the flotation recovery of the preparation concentrate. The middling treatment mode mainly depends on A/S and the size composition. However, similar ratio of A/S should not be the single factor of re-dressing, size composition plays an important role also. Re-dressing the middling mixed with the tailings of concentrated to the rough ground for desilication and the concentrate of scavenged to the fine ground for desilication to raise the recovery of 5.83%, when compared two flow sheet schemes.

Jan 1, 2014

By Benoit Clermont, Jan Lux

"Magotteaux and Anglo Platinum started a co-operation program with the main aim of establishing the optimum milling configuration measured in terms of throughput, fineness and energy consumption.For this purpose, a fully instrumented pilot milling plant, supplied by Magotteaux (Pty) Ltd, and equipped with a 0.9 x 1.0 m ball mill, was erected at Frank concentrator (Merensky Pt ore). The primary ball mills at Frank concentrator were surveyed in order to set the conditions for the base case. This data was then replicated in the pilot mill under the same configuration. Thereafter, a series of different parameters were varied in order to attempt to optimize the milling system.Only grate versus overflow discharge and open versus closed circuit will be discussed in this paper.It should be noted that this paper does not attempt to give a universal solution as to what milling configuration is optimum in all cases. The conclusions apply for this particular case and probably most others, but it would be advisable to consider each case on its own.CONCLUSION• Overflow versus grate dischargeAn overflow mill has a “pool” of slurry around the toe of the ball charge, which creates a counter lever to the ball charge. This will reduce the absorbed power in the range of 10-15% (depending on the case) and will consequently result in a coarser grind. The tests found a 4% gain in grinding efficiency (Wio) with an overflow mill but this is probably not significant.This lower absorbed power and coarser grind can be counteracted by increasing the ball charge (if below maximum) and/or by increasing the mill volume when removing the grate discharge (a typical grate takes up about 300mm of the mill length).• Open versus closed circuit"

Jan 1, 2003

By Xumeng Chen, Yongjun Peng, Dee Bradshaw

Regrinding rougher flotation concentrates has become a common practice when processing low grade and complex ores. It not only reduces the particle size and improves mineral liberation but also modifies particle surfaces and pulp chemistry due to the strong electrochemical reactions taking place during regrinding. Therefore, the floatability of minerals in the subsequent cleaner flotation is influenced by the regrinding conditions. This paper presents the effect of regrinding conditions on the mineral floatability from both industrial studies in the plant and fundamental studies in the laboratory. Different regrinding conditions were considered, including grinding media, the electrochemical properties of minerals, pulp chemistry (pH, Eh, DO), and breakage mechanisms in tumbling and stirred mills. Results indicate that the selection of regrinding conditions and mill types should not only depend on grinding energy efficiency and liberation but also depend on the surface properties and pulp chemistry produced for effective mineral flotation and separation at the cleaner stage.

Jan 1, 2014

By G. Önal

Recovery of nickel and chromite from the tailings has been studied on the samples with 0.214 % Ni and 5.10 % Cr2O3 content and taken from Orhaneli Chromite Concentration Plant. Mineralogical examinations of the samples showed the existence of chromite, olivine, pyroxene, chrysotile, anti-gorite, chlorite, idingite, tremolite and calcite together with trace amounts of millerite, pentlandite, pyrite, pyrrhotite, hematite and limonite type iron oxide minerals in partially serpantinized dunite type particles. In order to recover chromite from Chromite Concentration Plant tailings Mozley Table and Knelson Separator are used and concentrates containing approximately 42% and 46% Cr2O3 are produced respectively with 40% recovery. Most of the nickel remained in the tailings. Therefore, acidic leaching tests are performed in order to dissolve nickel from these tailings. Effects of particle size, acid concentration, temperature, leaching time and solid/liquid ratio on the nickel leaching efficiency are investigated. The optimum leaching conditions are found as 250 g/L acid concentration, 1/5 solid/liquid ratio, 2 hours of leaching time and 60°C temperature, almost all nickel is dissolved at the optimum conditions and acid consumption is about 841 kg/t. Repeated leaching tests are carried out in order to have enough Ni content in the leach liquor for the further treatment of solutions. After repeated leaching tests, leach liquor contains 3 kg/m3 Ni, 48 kg/m3 Fe, 2.2 kg/m3 Si, 23 g/m3 Cr and 590 kg/m3 H2SO4. Ni is recovered from that solution by precipitating with H2S followed by HNO3 dissolution and precipitating Ni as hydroxide with 63% Ni content. Leach cakes are subjected to the gravity separation (Mozley table) to recover the remained chromite and a chromite concentrate with 47% Cr2O 3 content is produced with 53% recovery. As a result of the abovementioned tests, a conceptual process flow sheet is proposed for the treatment of these chromite concentration plant tailings.

Jan 1, 2014

By André Mans, Frans B. Waanders

"Ferrosilicon (Fe-Si) is an important commercial material and it forms the basis of the powder used in dense medium separation (DMS) of various minerals in a minerals beneficiation process. Current losses of Ferrosilicon (Fe-Si), which is used in the dense medium separation (DMS) of iron ore at Kumba Resources, Sishen, South Africa occur due to adhesion to the separation products and also by being present in the effluent stream, due to abrasion. The losses contribute greatly to the running cost of the plant and the purpose of this project was to determine the characteristics of the unused Fe-Si and then to characterise the changes that occur during storage and the use thereof.A Scanning Electron Microscope (SEM) and Mössbauer Spectroscopy (MS) were used to investigate the characteristics of the fresh and used Fe-Si. The SEM analyses of the Fe-Si yielded a composition of 15 wt.% Si and 85 wt.% Fe with minor impurities of Mn and Cr (<1 wt. %), resulting in an ordered phase with a calculated composition of Fe2Si. The average density of the Fe-Si was found to be 7.177 g.cm-3 whilst the size distribution was determined with the d50 of the particles being approximately 30 µm. A slurry, containing 10% solids was prepared, which had a density of about 1.1 g.cm-3 and this slurry was used to conduct the various experiments under laboratory conditions at the university. Samples were taken at regular intervals from a storage container containing a lime solution as well as from a closed circulation circuit system, kept at a constant temperature of about 60°C. Mössbauer Spectroscopy yielded, for the new fresh Fe-Si-samples, a two-sextet spectrum with hyperfine magnetic field strengths of 19.9T and 30.7T respectively, and the yellow-brown froth was found to be akaganeite or ß-FeOOH.It was found that the biggest loss of Fe-Si was due to the abrasion of the particles during the DMS process. A possible change in magnetic properties was also observed, leading to further losses that could occur during prolonged use of the medium. No clear changes to the Fe-Si occurred during correct storage methods, as was initially thought."

Jan 1, 2003

By P. K. Sen, Mrinal K. Ghose

Tailing slurry is usually abrasive and possesses high viscosity. This paper examines the existing iron ore beneficiation process and focuses on some of the key environmental issues related to the disposal of tailings. It identifies that almost 32% of the iron ore extracted ends up as tailings and they are usually disposed in slurry form in tailing ponds. By the year 2000, 27 Mt of iron ore tailings were generated in India, which has become one of the biggest waste handling problems to the industry. Characteristics of the tailings vary widely. So the physical nature of tailings cannot be considered separately in isolation without considering the mill effluent from the beneficiation plant. In the present investigation, studies were carried out in three iron ore mines in India to evaluate the characteristics of tailings from the beneficiation plant. The tailing samples were collected from different locations during a time period of one year and analyzed. The results will be discussed and the characteristics of the tailings have been evaluated. The disposal system of tailings at the three mines was evaluated. The research on the settling characteristics of tailings indicates that the area provided in the existing tailing ponds in India is much more than that of the experimental results. This paper concludes that sedimentation tests are essential to design appropriate tailings pond with respect to size. In the proposed scheme it is suggested that an additional unit process, i.e. sedimentation tank be added to the process before the disposal of tailings to the tailing pond.

Jan 1, 2003

By I. A. Podkamennyi, O. E. Kovalchuk, G. P. Dvoychenkova

"Using the methods of electron microscopy and IR spectroscopy, mineral components in the run-of-mine kimberlites and on the surface of diamonds were identified. The mechanism and sequence of mineral formation on the surface of diamond crystals were established. Systematization and classification thereof were undertaken for the first time ever.INTRODUCTION The high content of diamonds sized -5 mm in the kimberlite ores of Western Yakutia determines their processing depth in the size class 0.5 mm and finer [1, 2]. These diamonds are recovered by grease and froth separation based on the natural hydrophobic properties of the crystals. When refractory altered kimberlite ores are fed into the industrial process, the performance of grease and froth separation of the diamond ore greatly deteriorates. [4, 10, 15, 17]. Altered kimberlites are known to contain up to 90% of secondary minerals. This reduces by up to 40% the recovery of diamonds by grease and froth separation. [6].Diamond crystals from the grease and froth separation tailings were investigated. On the surface of the examined diamonds, hydrophilic mineral formations were identified, responsible for reduced recovery by physicochemical separation methods [3, 12, 18]. The aim of this study was to identify and describe the relationship between the composition of kimberlite ores and mineral formations on the surface of diamond crystals in order to systematize, classify, and then develop methods of removal in grease and froth separation processes. MATERIALS Following materials were examined in this study: - kimberlites of various material composition, - resulting slimes, - diamond crystals from kimberlite ore processing products."

Jan 1, 2018

By Lokesh K. Thakur, Peter Radziszewski

"For the cases tested (11 mills with 15 operating conditions), the Bond abrasion test steel media wear rate prediction gives an overall error of 73% and a standard deviation of 192.5%. However, total steel media wear in a given mill (ball or SAG) grinding process is a product of three recognised wear mechanisms -- impact, abrasion, and corrosion. A total media wear model can be defined on the assumption that the effect of each wear mechanism can be independently determined which allows for a total media wear model to be defined as the summation of the wear result of each mechanism (eqn. 1). It is assumed that impact and abrasive media wear is a function of the energy dissipated in impact and abrasion as estimated by a DEM charge motion simulation. Corrosive media wear is assumed to be a function of the media surface area present in a mill.The 3 initial tests developed (steel abrasion wheel, corrosion batch mill, impact chamber) coupled with the impact and abrasion energy spectra from a DEM charge motion simulation produced total steel wear rate results for the same cases as the Bond abrasion test giving an overall error of 0% and a standard deviation of 66.1%. However, if one were to consider the general observation that wear is proportional to energy and maintain the assumption that corrosion is proportional to media surface area then one would realize that the total media wear eqn. (1) can be reduced to eqn. (2). As this is a linear equation and one has, for the same mill, media wear and operating data for three different operating cases, one obtains three equations with three unknowns. This defines a simple matrix manipulation to determine the constants k1, k2 and k3. From the previous data set, we had 6 identical mills grinding the same ore but having different worn liner profiles and charge volume which provided the opportunity to average out the ki values over 20 combinations of 3 cases. With the determined ki values, it was possible to determine a second estimate of the contributions of impact, abrasion and corrosion to total media wear giving an overall error of 0% and a standard deviation of 56%."

Jan 1, 2003

By Jochen Petersen, Harro von Blottnitz

"The landfill disposal of slags is common practice in the metallurgical industry. Chromium may be a minor constituent in many cases. It is present mostly in the form of chromites, which are considered environmentally benign and hence safe for disposal. Wastewaters from metal finishing operations are most commonly treated by reduction and precipitation of dissolved metals, including chromium, by lime addition, and subsequent landfill disposal of the resulting sludge. The metals contained in such sludges are mostly in the form of hydroxides, and as such considered environmentally stable.Thermodynamically, trivalent chromium, which is the predominant form in these waste materials, can be oxidised to the hexavalent form by atmospheric oxygen. Detailed research work on both slags and sludges has shown that a gradual emergence of hexavalent chromium can indeed be observed. The mechanism is governed by close physical contact between chromium oxide (or hydroxide) phases on the one side and calcium oxide (or hydroxide), which is present as flux in slags and residual lime in sludges, on the other. If oxygen can migrate to the points of contact, gradual formation of calcium chromate ensues.Hexavalent chromium is associated with high environmental toxicity, and hence undesirable in landfilled materials. Moisture migrating through landfill deposits can mobilise the highly soluble chromates and thus potentially transport them into natural waterways. Such gradual release from stainless steel and ferrochromium slag deposits has been demonstrated in a column experiment."

Jan 1, 2003