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By H. Palza, C. Ihle, S. Contreras

"Processing of minerals, particularly treatment of tailings, has been increasingly challenged by the presence of clays in the feed of thickeners. This occurrence is expected to become increasingly important given the nature of ore deposits currently being exploited and those that have been recently discovered. In sedimentation operations (solid-liquid separation), industrial flocculants often fail to coagulate clay-containing fines, generating supernatants with high levels of turbidity, thus implying operational problems. Recently, it has been reported that graphene oxide (GO), a graphite derivative with high oxygen-containing groups, could enhance the flocculation of clay systems, due to the interaction between clays and GO functional groups. In the present work, we investigated the effect of doping industrial flocculants (commercial polyacrylamide) with GO on the floculation of kaolinite suspensions in a solid-liquid separation stage. Separation performance was evaluated by studying flocculation kinetics using a focused beam reflectance measurement (FBRM) instrument, in a set of batch tests. A statistical analysis of the flocculation kinetics and floc population distribution was further carried out. Our results suggest the existence of a synergistic effect between the studied flocculants and GO. This effect is observed as a decrease of clay fine contents in the supernatant, thus improving solid-liquid separation eficiency for high clay containing tailings. INTRODUCTION Copper, given its mechanical, physical and chemical characteristics, is a critical material for the progress of society and so has been from early stages of mankind. Demand for this metal has increased due to the growth of cities and the technological explosion, leading to increase current mining production and reinforce the efforts in exploration for new deposits (Elshkaki et al. 2016). As copper-rich deposits are being depleted, it has been necessary to develop proper technology to mine deposits of lower grades and more complex mineralogies, keeping in mind that the economic window that allows the exploitation of them is reduced by the increase on operating costs (Crowson 2012 and Northey et al. 2014). High clay bearing minerals are found in many of those low-grade copper deposits, and they induce problems in all stages of the mineral processing route (Taner and Onen 2016). Particularly, in the solid-liquid separation stage, the flocculation process fails to remove the clay fraction from suspension and it leads to operational issues such as filter damage, overconsumption of reagents and the need to add an extra clarifying step for the recovered process water. Those problematics pose an interesting challenge."

Jan 1, 2018

By Ghislain Bournival, Cagri Emer, Seher Ata

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

Jan 1, 2014

By D. B. Sundar Ramam

In the recent past, a paradigm shift in terms of resource utilization and beneficiation practices is experienced by the Indian mining and mineral sector. Depleting iron ore reserves coupled with increasing demand for low-alumina iron ore fines to improve blast furnace performance in terms of productivity and reduced slag rate necessitate intensive beneficiation of iron ore. The task is even difficult for Indian iron ores, which are generally high in iron content and at the same time characterized by aluminous gangue. In 2006, M/s Tata Steel commissioned a state-of-the-art Jigging Plant (Batac Jig) at Noamundi Iron Mine (NIM), mainly to reduce alumina in iron ore fines. The jigging plant is incorporated in the existing beneficiation circuit to treat ?10+0.5mm size fraction of classifier fines. Over the course of plant stabilization while the plant could deliver desired ore upgradation and average product alumina, variability in terms of alumina content has been a concern. This paper discusses a case study of process parameters optimization in jigging operation to achieve consistent product quality while improving the effectiveness of gravity concentration for the beneficiation of Noamundi iron ore also to take care of inferior plant feed (input) grade year on year. The operating variables used to optimize jigging operations include bed height, pulsion and suction time, particle size, strokes, and plant throughput rate.

Sep 1, 2012

By C. Tokoro

Co-precipitation of dilute toxic anions with ferrihydrite is an important removal mechanism in wastewater treatment system. Although, numerous qualitative studies have been published on removal characteristic from wastewater of dilute anions by co-precipitation treatment, detail mechanism or quantitative characteristic is not well understood. This paper discussed the co-precipitation mechanism of As(V) and Cr(VI) with ferrihydrite by comparative experiments between co-precipitation and simple adsorption. In this study, co-precipitation experiments and simple adsorption ones were distinguished closely. In the former, precipitation of hydroxides and adsorption of anions develop simultaneously, but in the latter, anions adsorb onto prepared hydroxides. Although high affinity anions for hydroxides (e.g. As(V) for ferrihydrite) showed quantitative difference of removal ratio between co-precipitation experiments and simple adsorption ones, low affinity anions (e.g. Cr(VI) for ferrihydrite) showed quantitative agreement in spite of deferent forms of ferrihydrites between them, that is, amorphous ferrihydrite was formed in co-precipitation experiments, but goethite was formed in simple adsorption ones. In order to discuss the mechanism of co-precipitation phenomena, three experimental studies have been carried out: (i) adsorption isotherm measurement in the co-precipitation experiments of As(V) or Cr(VI) with ferrihydrite, (ii) zeta potential measurement of co-precipitated or simple ad-sorbed ferrihydrite with As(V) or Cr(VI), and (iii) XRD analysis of co-precipitated As(V) for ferrihydrite. All experimental results suggested the main mechanism in co-precipitation phenomena of As(V) was not only a surface complexation (simple adsorption) but also a surface precipitation.

Jan 1, 2014

By M. Ito

Cobalt-rich ferromanganese crust and nodule ores from seamount areas contain volcanic and sedimentary rocks as substrate or nuclei. These ores require mineral processing to remove the sub-strate/nuclei rock before smelting. This paper reviews experimental results of previous investigations. Observations and analysis of 10 samples from different localities were carried out and it was found that the liberation ratio of crushed product was high even at coarse size fraction, 0.5mm to 4mm. Experimental and calculated results in the smelting stage confirmed that the separation product satisfies the standards of the subsequent smelting process if the substrate/nuclei rock is removed from the 0.5mm to 4mm fraction with high separation efficiency. There was a density difference between the substrate/nuclei rock and the ferromanganese component. Thus the coarse sized sample was treated with gravity separation; air table separation was used as a dry method and jig separation as a wet method and high grade values with high recoveries were obtained by both kinds of gravity separation.

Jan 1, 2014

Sedimentary deposits such as sandstone are formed by the aggregation of cemented sand grains. Phosphates and laterite present similar aggregation of mineral grains. Grains and cement have different mineralogy and chemical characteristics. During size reduction through crushing or coarse grinding, the rocks are crumbled. Mineral grains and cement are then liberated, and the produced size distribution reflects their ?natural size distribution?. Mathematical modelling of these concomitant effects of crumbling and mineral liberation necessitates a specific material description and the adaptation of the commonly used theories of breakage kinetics and population balance. The coarse particles are mainly agglomerates made of mineral grains and cement particles whereas the fine particles are grains and cement with a natural grain size distribution. The population balance between the different particle size and particle types during size reduction takes into account the breakage rate and the progeny size distribution. The breakage rate can be described by a simple probability function or by a first order kinetics whereas the progeny size distribution is described by a breakage matrix. The model proposed here considers that the agglomerates will produce other agglomerated particles, liberated grains and cement particles; the two latter having their natural size distribution. The liberated grains and cement particles are subject to size reduction and follow the most commonly used theory of breakage. The present paper describes the theoretical approach of the concomitant crumbling and liberation effects. The application to a mathematical model for the cone crusher is presented. The advantage of such approach is then demonstrated through a simulation study for the optimisation of a crushing plant. Keywords: mineral liberation, modelling, crushing, sedimentary ore

Sep 1, 2012

By Tomasz Niedoba

Coals occurring in nature are characterized by various properties. According to Polish norms, the classification of coals taking into consideration their calorific value contains coals from type 31 (flaming coal) until type 43 (meta-anthracite). The samples of coal of type 31 were taken for investigation. To this purpose, the approximations of ash contents and density distribution functions were done for this coal type (determination of marginal distribution functions). They were the basis for application of so-called Morgenstern distribution functions to approximate the function Z=L (?), where Z is ash contents and ? - coal density. Then, the comparison between obtained results was performed and the results were statistically evaluated. They are the basis for the further research of other types of coals.

Sep 1, 2012

By Michael Young, Rodrigo Araya, Cesar Gomez, Le Huynh, James Finch

The performance of flotation machines is closely related to the gas dispersion characteristics achieved in their operation. It is known that frothers play a major role not only in the size distribution of the generated bubble population, but also on the swarm rise velocity. A program to characterize frother effects on two-phase hydrodynamics (air-water) of Jameson cells was undertaken in a fully instrumented pilot unit installed at McGill University. Gas dispersion parameters (gas velocity, gas holdup and bubble size distributions) of the gas-liquid mixture generated in the downcomer were measured after its release into the separation chamber. The unit was operated under different conditions including gas velocity, liquid jet velocity and frother concentration (MIBC). Bubble size distributions for concentrations above the critical coalescence concentration (CCC) were narrow with Sauter mean diameter between 0.6 to 1.3 mm. The bubble size followed the general trend as encountered in other types of flotation machines, i.e., rapid decrease with increasing frother concentrations below 10 µL/L, and almost no change in size for concentrations above 30 µL/L. The CCC was between 10 and 15 µL/L. Strong correlations were found between bubble size and air-to-liquid flow ratio (APR), and between the bulk density of the aerated solution in the separation tank and the vacuum inside the downcomer. An equation is proposed to estimate gas holdup in the separation tank from vacuum and bulk density readings.

Jan 1, 2014

By Kyle P. Flynn, Frank J. Hrach, James D. Bittner

ST Equipment & Technology, LLC (STET) has developed a processing system based on tribo-electrostatic belt separation that provides the mineral processing industry a means to beneficiate fine materials with an entirely dry technology. In contrast to other electrostatic separation processes that are typically limited to particles greater than 75µm in size, the triboelectric belt separator is ideally suited for separation of very fine (<1µm) to moderately coarse (300µm) particles with very high throughput. The high efficiency multi-stage separation through internal charging/recharging and recycle results in far superior separations that can be achieved with a conventional single-stage free-fall tribo-electrostatic separator. The triboelectric belt separator technology has been used to separate a wide range of materials including mixtures of glassy aluminosilicates/carbon, calcite/quartz, talc/magnesite, and barite/quartz. An economic comparison of using the tribo-electrostatic belt separation versus conventional flotation for barite / quartz separation illustrates the advantages of dry processing for minerals.

Jan 1, 2014

By J. Kwon, D. Lee, H. Cho

"The use of the combined grinding and liberation model to predict liberation characteristics of iron ore comminuted by a ball mill was studied. Comminution characteristics were obtained using the one-size fraction method. The iron ore samples were crushed and separated into a number of narrow size fractions by screening. The size fractions were further divided by magnetic separation into three classes: concentrate, middling, and tailings. Subsequently, various size-grade classes were subjected to ball milling, and the results were analyzed in terms of the kinetic grinding model. The mineralogical textures of the grinding products were analyzed using mineral liberation analysis. The distribution of iron content within the size fractions was characterized by the beta distribution combined with the Andrew–Mica diagram. It was found that the grinding characteristics of the iron ore samples varied slightly with the iron content. However, the liberation characteristics were well described by the same set of liberation model parameters, regardless of composition. The variation in grinding kinetics with composition and the liberation model parameters was used in the combined comminution–liberation model to predict the evolution of the size-composition matrix as grinding proceeded. The predicted results agreed well with the experimental results. The developed model can be used to construct the yield–recovery graph and to calculate the liberation efficiency to determine the size reduction threshold for efficient separation. INTRODUCTION In mineral processing, comminution is usually the first step that ores undergo to liberate valuable minerals from gangue minerals. Generally, as the particle size decreases, higher liberation can be achieved. However, excessively small particles are unfavorable to subsequent processes, such as separation. Moreover, comminution is a highly energy-consuming process itself that accounts for approximately 60% of all energy used for processing. Therefore, there is a definite need to increase energy efficiency by applying adequate stress so that a high degree of liberation can be acquired at the coarsest size without overgrinding. To this end, it is essential to develop a model to predict the liberation of minerals as a function of size reduction."

Jan 1, 2018

By Narasimha Mangadoddy

The complex nature of multi-phase flow in dense medium cyclones has restricted plant operators and designers to rely on empirical equations for predicting the performance. A number of empirical cyclone models have been developed in the past (Wood, 1990; Dunglison, 2002). In recent years, this subject has been broached with computational fluid dynamics (CFD). Most of the CFD models have not considered the correct rheological behavior of magnetite medium while simulating the medium segregation inside the cyclone. These models mostly predict excessive underflow volumetric flow rates. In this paper simulations of magnetite medium in a dense medium cyclone, were conducted in FLUENT where the particle phases were simulated using the modified Mixture model. The turbulence was resolved using Large Eddy Simulation (LES) model. The rheological behavior of medium was considered in the form of Granular viscosity, Newtonian and Non-Newtonian models corrected with particle loadings and fraction of ultrafines. Multi-phase simulations using granular viscosity option although predict the overall split product medium densities reasonably close to experiments, the mixture viscosity values are restricted to substantially lower values, similar to water viscosity. Simulations using Newtonian viscosity model corrected with particle loading, and fine fraction below 53µm size is predicting overall mixture viscosity levels well over water viscosity levels, but under predicting the under flow the underflow medium density. Multi-phase simulations using Non-Newtonian Herschel-Buckley model, calibrated for superfine magnetite medium measured viscosities, is closely predicting the medium segregation with gamma ray tomography data. Overall predicted product medium densities, underflow volume split are close to the experimental data. This model is can be further used to simulate coal portioning and hence in developing new designs.

Sep 1, 2012

By M. Canbazoglu

In this study, optimum sulphuric acid leaching parameters of zinc and other valuable metals from two different waelz clinker samples were researched. Origins of the samples are electric arc furnace dust and original non-sulphite zinc ore waelz clinkers. The main zinc mineral determined as zincite in these samples. Collective dissolution of zinc and other valuable metals in waelz clinkers can easily achieved by sulphuric acid leaching of them. 96% of zinc can be dissolved at 80 ºC, 60 g/L sulphuric acid concentration, 60 min. leaching time and 1/5 solid/liquid ratio. Almost 90% of Cd, Cu and Co in clinker dissolved at these conditions while dissolution of Fe was almost 20%. The consumed acid amount for dissolved per ton of zinc is approximately 1.7 tons at these conditions.

Jan 1, 2014

By Heribert F. Broicher, Arne Volland

The application of remote sensing techniques combined with fluorescence spectroscopy is realised in analytical devices called LIF Analysers. The analysis of laser-induced fluorescence facilitates non-destructive, non-contact, on-line and real-time rock identification and quality control of bulk solids in transport. LKAB of Sweden was the first company to test LIF Analysers in the Kiruna Mine for bulk sorting of run-of-mine ores depending on the phosphorus content. Other applications tested in Germany so far are quality control of limestone (iron and/or dolomite content) and rock identification in lignite mining. Of special interest also is rock identification in diamond mines for dilution control. The paper summarises the present state of the application of LIF Analysers.

Jan 1, 2003

By A. Morrison, P. Brito-Parada

"The separation of valuable and gangue minerals according to their surface hydrophobicity in a froth flotation tank occurs in both its pulp and froth phases. In the pulp phase, hydrophobic particles must be brought into contact with rising bubbles introduced at or near the bottom of the tank. In a mechanical froth flotation tank, this is primarily achieved through the agitation of the pulp by an impeller or by a rotor-stator system. However, the turbulent and mixing effects of such an impeller or rotor-stator system, necessary to promote bubble-particle interactions in the pulp, are not confined to the pulp zone, but are transmitted into the froth zone at the pulp-froth interface. This impeller-induced turbulence at the pulp-froth interface is compounded by the impulse of buoyant bubbles entering the base of the froth phase, reducing the stability, and thus separation performance, of the resulting froth. Hence, turbulence improves separation performance if it occurs deep in the pulp phase, but diminishes it if it occurs close to the pulp-froth interface. For this work, a performance-enhancing pulp phase insert was designed to isolate the impeller-induced turbulence from the pulp-froth interface in a laboratory-scale, continuously-operated froth flotation tank. The result was a shifted grade-recovery curve that allows the insert to be designed to maximize the recovery from the system without sacrificing the grade of the concentrate, or vice versa, along a spectrum of improved performance. This paper will present the insert design and development process that resulted in this improved grade-recovery curve, as well as a set of heuristics that could be used to design a similar insert for pilotand industrial-scale validation and deployment.INTRODUCTIONAn almost ubiquitous design feature of commercial flotation tanks is the enclosure of the impeller to create a concentrated turbulent zone (Mavros, 1992). These turbulent zone enclosures are varied-- from the rotor-stator design of, for instance, Outotec cells, to the air disperser design of Wemco cells-- but all share the same rationale: that turbulence is desirable to promote bubble-particle interactions (Ralston, 1999), and to produce smaller bubbles (Wills, 2006), but also undesirable because it promotes the detachment of valuable mineral particles from bubbles, and exacerbates entrainment-inducing mixing at the pulp-froth interface (Jameson, 2010)."

Jan 1, 2018

By Peter Ay, Elena Geldt, Satyanarayana Narra, Claudia Glaser

"As part of an extensive research and development project, the technical and technological implementation of the patents DE 10 358 245 B4 and WO/2006/056172 was developed with the goal to present a system for the innovative roll- agglomeration method exhibiting a) a modular setup, b) high productivity and c) suitability for the use of fibres of different applications and product qualities (high technical availability). The processability of the rarely adapted raw fibre materials into high-value intermediates brings forward their application in various processing industries dealing with the production of fibre reinforced plastic composites, heat and sound insulation materials as well as with the gas and liquid cleaning systems. The innovative fibre agglomeration presented in this work is performed by a combination of rolling and pressing the fibres inside a geometrically pre-defined roller table, in which the fibres are forced to bound through entanglement / interlocking and develop into agglomerate. The agglomeration process is carried out in a circular roller path with a rectangular cross-section. For improving the adhesive properties, and thus the quality of the agglomerates, the boundary surfaces can be covered / patterned / lined / coated with various materials. The resulting roll-agglomerates are characterized by different quality parameters such as mass, shape, porosity and stability. The properties of the agglomerates can be modified based on the end-product requirements by slightly modifying the process parameters such as filling ratio, residence time, roll-geometry, procurement of the boundary surfaces, etc. as well as the input material properties such as fibre type, fibre fineness, fibre length, etc. This work carries extensive work on the roll-agglomeration system to assess the effectiveness and the variability based on the product specifications. Agglomerates were produced with wide variations of system parameters with varying roller table liners and based on evaluation of the produced agglomerates with respect to their mass, the geometrical dimensions, their porosity and stability."

Jan 1, 2014

By D. Pienaar, B. McFadzean, T. Jordaan

"Dithiophosphate (DTP) collectors have the lowest affinity for sulfide mineral surfaces compared to other common sulfide mineral collectors, such as xanthates and dithiocarbamates. In some cases it has been found that DTP does not adsorb onto the mineral surface at all and yet increases in recoveries and grades are noticed with the addition of DTP. Many studies have investigated the interactive effects of collector mixtures. However, there have been relatively few studies on the interactive effects between frother molecules and collectors. This study investigates the interactions between different types of frothers and sodium diethyl dithiophosphate.The study found that there were large increases in pyrite and galena microflotation recoveries at both pH4 and pH9 when DTP was mixed with small amounts of frother at a constant bubble size, showing that these increases were neither mineral-specific nor pH-specific. The same effect was not present when xanthate was used as a collector. The increases in recovery when using the DTP-frother mixture were similar irrespective of the type of alcohol or polypropylene glycol frother that was used. In an attempt to distinguish the mechanism of enhanced flotation recovery, various supplementary experiments were performed. It was found through adsorption experiments that no DTP was adsorbing on to the mineral surface. Therefore, interactions at the air-water interface were performed. Surface tension and critical coalescence concentration tests showed that, while DTP is a weak surfactant at the air-water interface, it does not have a synergistic effect in the presence of frother. DTP-frother mixtures do, however, show interactions in the froth phase, indicating an interaction in the thin films. It is proposed that there is a DTP-frother interaction on the bubble surface that enhances the rate of film thinning at the 3-phase bubble-particle contact."

Jan 1, 2018

By David De Klerk, Maximilian Richter, Thirunavukkarasu Pathmathas, Indresan Govender

We consider the average power dissipation distribution for dense granular flows of an idealised mono-sized charge (5 mm glass beads) in a 300 mm diameter tumbling mill operated in the cascading-to-cataracting Froude regime. By combining the inherent frictional nature of particles within a dense flow regime and noting that tumbling mills are typically characterised by collisional and turbulent stresses, we derive the power dissipation distribution for athermal boundary conditions. The input data to the model (velocity, solids concentration, pressure and flow depth) are obtained directly from non-invasive measurement using a nuclear imaging technique: Positron Emission Particle tracking (PEPT). The power dissipation due shear stresses is shown to be the dominant mode of dissipation in the tumbling mill with up to two orders of magnitude difference between pressure induced dissipation and shear.

Jan 1, 2014

By Stephen Gay, Dewetia Latti

"When improving a plant a mineral processing engineer would like to know the mineral composition distribution. In order to assess this distribution in particles, as compared to the corresponding distribution in particle sections, a procedure needs to be applied to the observed particle sections. Such a procedure is called a stereological correction. There exists many stereological correction procedures, but one group of such procedures is based on using those stereological equations that do not require making assumptions regarding particle shape or texture.In particular Davy derived an equation to estimate the covariance of mineral composition distributions for particles from both particle sections and linear intercepts. Furthermore, this covariance can also be used to measure the variance of the composition distribution of each mineral.This paper shall present results verifying this equation. The experimental method was based on obtaining particle information from serially-sectioned particles. Particle samples selected for serial sectioning displayed a range of natural textures including liberated, binary and composite particles. The exposed surface of the polished sections were analysed using QEM*SEM. This procedure was repeated until all of the grains have been polished away. The covariance of mineral distributions were calculated from the serial sections and compared with that calculated using Davy’s equation."

Jan 1, 2003

By Gregory Harbort, Sarah K. DeBono, Alan J. Monaghan, Emmanual V. Manlapig

"The Jameson Cell is a type of flotation machine in which air and pulp are brought together in a vertical tube called a downcomer. Within the downcomer the air and pulp are dispersed into a dense foam of fine bubbles, which creates a favourable environment for bubble-particle collision and subsequent collection of hydrophobic particles. The intense collection zone within the downcomer can be considered similar to the zone between the rotor and stator in mechanical flotation cells.Research into the bubble-particle collision and fluid dynamics of mechanical cells rotor-stator zone has been limited by the difficulty of achieving accurate measurements in production sized machines. With the Jameson Cell the downcomer is largely external and separated from the flotation tank, allowing ready access to the primary contacting zone for measurement and analysis.An investigation has been undertaken into the operating characteristics of the downcomer relating to bubble-particle collision. An effective mapping of the downcomer has been made through measurements of void fraction and bubble size taken across cross sections of the downcomer. Analysis of these measurements has provided an interpretation of the variations in the air and fluid dynamics, bubble size and distribution throughout the downcomer chamber.Existing models of bubble-particle collision efficiency are reviewed in respect to the collected information and refinements conducted. The area of maximum bubble-particle collision efficiency is defined. Findings are related to operation within the rotor-stator zone of mechanical flotation cells."

Jan 1, 2003

By J. B. Rubinstein

"The paper gives an overview of the history of flotation machine development. The laws of their evolution are stated and the place and role of column flotation are demonstrated.The major parameters of column cell diameter and height are discussed. Options are proposed for optimization of the hydrodynamic characteristics of large-capacity column cells. The high efficiency of columns with cell height of 4-6 m is demonstrated. The optimum parameters of multisectional column machines are determined. Their advantages compared to monocells are shown. A scaling-up procedure for column machines was developed based on flotation macro- and microhydrodynamics simulation."

Jan 1, 2003