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By S. Tu, Y. Yuan, H. Wei, Z. Chen, M. Jia

"To reduce production costs and increase efficiency in ageing coal mines, a system that utilizes two shearers in a fully mechanized longwall working face is proposed. Using theoretical and engineering experience, three issues pertaining to the system were determined: (a) the two-shearer mining technique; (b) matching and modifying the equipment; (c) and coal-cutting task allocation for each shearer. Two mining processes are proposed, with the two shearers travelling in either the same or opposing directions. To avoid breakage of chains and pan extrusion of the armoured face conveyor (AFC), the length of the AFC ‘snake’ was controlled. To ensure continuous cutting and transporting of coal, the cross-sectional dimensions of the AFC were checked and the shearer closer to the head drive was modified. Based on the assumption of equal cutting times for each shearer, the meeting position of the two shearers was obtained by using a theoretical model of mining task allocation. Application of this technique at No. 2 Jining Mine, China, has shown remarkable benefits: daily production capacity was increased by 54% and personnel efficiency was improved by 33 t/d per person. IntroductionAll coal mines aim to increase the unit output of the working face to reduce mining costs and improve the economic efficiency of the operation. To achieve this goal, a production model known as one mining face of the mining area has been adopted by most Chinese coal mines (Hu, Meng, and Zhu, 2008; Zhang, Zhang, and Wang, 2000). Under these conditions, the main technical approaches to maximize the output are increasing the width of the working face (Qu, Xu, and Xue, 2009) and accelerating the advancing speed (Robbins, 2000). In coalfields with shallow seams, the width of a fully mechanized face exceeds 300 m (Ju and Zhu, 2015; Fu, Song, and Xing, 2010); in coalfields with deep seams, the width of the face is usually greater than 240 m (Liu et al., 2016; Li et al., 2013). The term ‘super-long working face’ was proposed to describe working faces with a width of over 240 m (Zhao and Song, 2016; Xu et al, 2007) in China. To support these long working faces with rapid advancing speeds, high-powered mining equipment is required (Kulshreshtha and Parikh, 2001, 2002; Tu et al., 2009; Mishra, Sugla,and Singha, 2013). This is easily achieved in newly built mines, but is not a good choice for ageing mines because of the low return on a high investment on account of the limited remaining resources. It is therefore difficult for ageing mines to significantly increase their unit output with the existing mining equipment. This study focused on this problem: two shearers were applied to a longwall fully mechanized working face (LFMWF) to achieve increased unit output."

Oct 1, 2018

By P. N. Erasmus

This paper considers the fundamental concepts of support design for underground openings in highly stressed ground. It concludes that the conventional deformed reinforcing bar, woven mesh and cable lacing support methods that have been widely used in deep gold mines are quite in appropriate for the support of highly stressed tunnels. The following is suggested as the criterion for adequate dynamic support under rockburst conditions: the energy absorbed by a support unit (yielding through some acceptable limited displacement) should exceed the kinetic energy generated by the mass of rock that is intended to be retained by that unit. Duraset in conjunction with SRK Consulting has developed a yieldable steel tendon called the Durabar®. It is unique in the sense that it cleverly utilizes the property of the ductility of ordinary low-carbon steel from which it is made to accommodate the excessive displacement it is subjected to in the case of rockbursts or swelling ground.

Jan 1, 2009

By J. Güntner

Most copper/cobalt ores from the Central African Copperbelt contain sulphidic compounds, which are not extractable in direct leaching. Roasting provides the possibility to transfer the valuable components into leachable compounds. In an operation window defined by temperature and off-gas composition it is possible to selectively oxidize iron sulphides to haematite and copper/cobalt sulphides to sulphates. Selective sulphating of the valuable minerals is an important condition for the subsequent leaching stage. The dissolved copper and cobalt are recovered by solvent extraction and electrowinning. This technology has been part of an established process for many decades. The concentrates from recent projects on the Copperbelt have lower sulphur contents, and frequently higher copper contents, than those from older projects. The paper shows the consequences of this trend for plant operation and explains useful counter actions by means of case studies. Autothermal combustion is ensured even at very low sulphur contents. Off-gas treatment has so far been based on SO2 removal through sulphuric acid production. The generated acid is used to make up acid losses in the hydrometallurgical plant section. This well-proven process combination is still the preferred route if the feed sulphur content is high enough; however, some cases may require different off-gas cleaning concepts without compromising on clean air quality. Roasting in a fluid-bed furnace remains the core of the technology. Fluid-bed roasters are easy to operate and provide an excellent control of the calcine quality. Different feeding and heat-recovery systems are used to provide a tailor-made solution for each project. Outotec built it first sulphatizing roaster in Zambia about 30 years ago. At that time, the roasting of metal sulphides was already one of the main technologies in the company. Outotec has developed roasting solutions for copper, gold, zinc, lead, molybdenum, and pyrite ores. The continuously expanded and upgraded research facilities provide an excellent basis for developing sustainable, energy-efficient, and economic solutions for copper and cobalt production in Africa.

Jan 1, 2012

By J. Güntner

Most copper/cobalt ores from the Central African Copperbelt contain sulphidic compounds, which are not extractable in direct leaching. Roasting provides the possibility to transfer the valuable components into leachable compounds. In an operation window defined by temperature and off-gas composition it is possible to selectively oxidize iron sulphides to haematite and copper/cobalt sulphides to sulphates. Selective sulphating of the valuable minerals is an important condition for the subsequent leaching stage. The dissolved copper and cobalt are recovered by solvent extraction and electrowinning. This technology has been part of an established process for many decades. The concentrates from recent projects on the Copperbelt have lower sulphur contents, and frequently higher copper contents, than those from older projects. The paper shows the consequences of this trend for plant operation and explains useful counter actions by means of case studies. Autothermal combustion is ensured even at very low sulphur contents. Off-gas treatment has so far been based on SO2 removal through sulphuric acid production. The generated acid is used to make up acid losses in the hydrometallurgical plant section. This well-proven process combination is still the preferred route if the feed sulphur content is high enough; however, some cases may require different off-gas cleaning concepts without compromising on clean air quality. Roasting in a fluid-bed furnace remains the core of the technology. Fluid-bed roasters are easy to operate and provide an excellent control of the calcine quality. Different feeding and heat-recovery systems are used to provide a tailor-made solution for each project. Outotec built it first sulphatizing roaster in Zambia about 30 years ago. At that time, the roasting of metal sulphides was already one of the main technologies in the company. Outotec has developed roasting solutions for copper, gold, zinc, lead, molybdenum, and pyrite ores. The continuously expanded and upgraded research facilities provide an excellent basis for developing sustainable, energy-efficient, and economic solutions for copper and cobalt production in Africa.

Jan 1, 2012

The key functions of project evaluation are to assess potential profitability and to develop an effective operational design. For mining projects, design aspects include mining methodology, ore treatment methodology and production rates. All of these characteristics impact on project economics and overall value. Resource models, which form the ultimate basis of project evaluation, typically consist of tonnes above cut-off, grade above cut-off and the spatial distribution (connectivity) of tonnes/grade above cut-off, for one or more variables. Dilution, ore loss and metallurgical recovery are all modifying factors applied to the resource model during evaluation and determination of profitability. A key issue is: how is the value determined? In addition to traditional combination of in situ tonnes/grade, the following merit serious consideration: the concentration of deleterious elements, throughput rates, mining/processing costs and - importantly - metallurgical recovery. Geometallurgy is an emerging field targeted at integrating these issues by identifying either direct measures or proxies for throughput (hardness, grindability), recovery (liberation, mineral shape/texture, etc) and concentrate quality from easily collected macro-, meso- and microscopic data. These 'geometallurgical variables' drive project costs and revenues in a fundamental way. For geometallurgical characterisation to have a real impact on business design, it must enable improved mine planning. When creating spatial estimates for such variables, it is preferable to find proxies that can be measured as close to the intact rock mass as possible. However, spatial estimation of proxies for geometallurgical properties and responses is complex and requires special consideration. Unlike grades, both proxies and absolute measures of geometallurgical variables are not necessarily linear or additive and therefore require very careful geostatistical consideration. In some cases, models must predict extreme values of geometallurgical attributes rather than averages. Incorrect characterisation of metallurgical recovery/throughput can (and has) led to misspecification of the scale of projects, and thus can be seriously value destructive. Aspects of geometallurgy have long been important in iron, bauxite, manganese and coal deposits and are increasingly on the radar for base and precious metal miners. However, as more metallurgically complex deposits are developed and mining of large-scale, low-grade deposits becomes more commonplace, the importance of characterising the metallurgical response in order to generate properly optimised projects will rapidly increase. It is possible that in many `traditional' (ie grades and tonnes) reserve models, the variables that drive the project are missing!

Jan 1, 2007

By T. Feroze, B. Genc

"Blind headings in room and pillar coal mines are a major source of methane and coal dust. Most methane and coal dust explosions therefore occur in the blind headings. The primary cause of these explosions is the disruption of the local ventilation system. Line brattice (LB) ventilation systems are used to ventilate blind headings by directing air from the last through road (LTR) into the heading. The amount of air available to ventilate the face of the empty heading depends on the heading dimension, settings of the LB, and velocity of air in the LTR. LBs are commonly installed by underground supervisory staff based on work experience, which may result in ineffective ventilation. The correct installationof LBs remains a challenge. In this study, a validated computational fluid dynamics (CFD) model has been used to analyse the effect of the LB ventilation system variables on the air flow rates close to the face of the empty heading. Full-scale three-dimensional models with various heading heights, heading depths, LB settings, and LTR velocities were simulated. The air flow rates and patterns at various locations inside the heading were analysed. A comparative study was carried out to quantify the effect of each of these system variables on the flow rates close to the face of the heading. Based on the findings, a user-friendly numerical model was formulated that can be used to estimate the flow rate close to the face of an empty heading for different practical settings of the system variables. This model can help the supervisory staff to swiftly implement the ventilation plan according to the regulations and the mine standards. The model can also serve as part of the curriculum for educating future mining engineers."

Jan 1, 2017

By T. Feroze, B. Genc

"Blind headings in room and pillar coal mines are a major source of methane and coal dust. Most methane and coal dust explosions therefore occur in the blind headings. The primary cause of these explosions is the disruption of the local ventilation system. Line brattice (LB) ventilation systems are used to ventilate blind headings by directing air from the last through road (LTR) into the heading. The amount of air available to ventilate the face of the empty heading depends on the heading dimension, settings of the LB, and velocity of air in the LTR. LBs are commonly installed by underground supervisory staff based on work experience, which may result in ineffective ventilation. The correct installation of LBs remains a challenge.In this study, a validated computational fluid dynamics (CFD) model has been used to analyse the effect of the LB ventilation system variables on the air flow rates close to the face of the empty heading. Full-scale three-dimensional models with various heading heights, heading depths, LB settings, and LTR velocities were simulated. The air flow rates and patterns at various locations inside the heading were analysed. A comparative study was carried out to quantify the effect of each of these system variables on the flow rates close to the face of the heading. Based on the findings, a user-friendly numerical model was formulated that can be used to estimate the flow rate close to the face of an empty heading for different practical settings of the system variables. This model can help the supervisory staff to swiftly implement the ventilation plan according to the regulations and the mine standards. The model can also serve as part of the curriculum for educating future mining engineers."

Jan 1, 2017

By C. A. Young, J. L. Bowden

"Cyclic voltammetry experiments were conducted on copper and chalcopyrite (CuFeS2) in the absence and presence of ethyl xanthate, and compared to mass-balanced EH–pH diagrams. The results for copper duplicate those found in the literature and confirm xanthate chemisorption. However, the, results indicate that chalcopyrite oxidizes to chalcocite (Cu2S) and only afterwards is chemisorption observed due to small currents appearing with xanthate. This phenomenon suggests that the mineral's hydrophobicity is induced by more than dixanthogen and copper xanthate. Hydrophobicity was found to be pH-dependent over a range of alkaline conditions (pH 7–11) at narrow potentials (0 to –200 mV). An EH–pH diagram for chalcopyrite with xanthate is presented to illustrate the conditions under which chalcopyrite would be hydrophobic and thereby more thoroughly explain the results in the literature. IntroductionSulphide minerals are generally concentrated from ores by froth flotation, a physiochemical process that induces separation based on differences in hydrophobicity. In this process, a gas is bubbled into a slurry and the minerals that are hydrophobic (water-repelling) adhere to the bubbles and float to the surface while the hydrophilic (water-loving) minerals remain in the slurry. With sulphide minerals, the hydrophobicity is generally established in two ways. The first is by the addition of a collector, which is a heteropolar molecule with a reactive inorganic head group and an inert organic tail. Typically, the head group bonds with the sulphide mineral surface by adsorbtion either chemically (chemisorption) or physically (physisorption) or by complexing with atoms that solubilize somewhat at the surface (surface precipitation). These interactions leave the organic tail protruding from the mineral surface, thereby inducing hydrophobicity. The second method is by oxidation of the mineral surface to form a layer that is metal-deficient/sulphide-rich or comprised of elemental sulphur. Because the layer mimics naturally hydrophobic sulphur, this enables ‘collectorless’ flotation. Furthermore, this oxidation phenomenon adds an electrochemical dimension to the understanding of sulphide mineral flotation."

Jan 1, 2016

By M. Lange

The postulation that primary platinum group metal (PGM) matte will chemically react with magnesia-chrome bricks when temperatures exceed 1500°C was tested. Magnesia-chrome brick samples were heated in contact with matte at 1300°C to 1750°C for 30 minutes, after which the refractory samples were analysed using reflected light microscopy and scanning electron microscopy. The samples were all completely penetrated by matte. As the temperature increased the matte also penetrated the fused aggregate grains and disintegrated them. The chromium concentration of the matte inside the refractory samples was found to be slightly higher than that of the bulk matte. At temperatures of 1500°C and higher, MgO, FeO, and magnesium-rich silicate crystals could be identified in the matte directly adjacent to the refractorymatte interface. Phase relations clearly indicated that chemical reactions take place between primary PGM matte and the magnesiachrome refractory material at temperatures above 1500°C, but that these reactions are more complex than expected from FactSAGE® calculations.

Jan 1, 2014

By J. Björkvall, L. Bååth, D. Malmberg, J. Malm

Microwave technology has for decades been a tool for astronomers to map and understand the complexities of the universe its composition and extent. It is also used on a laboratory scale by spectroscopists to examine properties of atomic and molecular compounds. In this novel work we will introduce microwave technology to be used for the investigation of liquid slag structures. The preliminary results indicate that the alteration of the slag composition could be correlated to the measured microwave refractive index. Investigations have been performed in the Al2O3-CaO-SiO2slag system. Keywords: Microwave technology, slag, structure, liquid, Al2O3-CaO-SiO2

Jan 1, 2004

By A. Becker, R. Tait, S. L. George, A. Carlisle

Surface treatments like laser shock peening (LSP) induce residual stresses penetrating up to 1 mm deep, surpassing traditional methods, thus significantly increasing the potential impact on materials prevalent in the automotive and aerospace sectors. Through extensive fatigue testing and fractography investigations, it was determined that LSP resulted in a fatigue life increase of over five times for aluminium alloy AA7075-T6 and titanium Ti-6Al-4V. Increased fatigue life was also noted in AISI316 stainless steel, which showed increases in fatigue life of 1.7x. While fatigue life in all cases improved, the efficacy of LSP was shown to be material dependent.

Jul 23, 2025

By T. Feroze, B. Genc

"The ventilation of underground coal mines plays an important role in minimizing the risk of methane and coal dust explosions. The ability of ventilation, with the use of line brattices (LBs), to remove methane and coal dust in empty headings is dependent on the amount of air leaving the LB and entering the heading. The quantity of this air depends on the associated system variables, namely heading dimensions, settings of the LB, and velocity of air in the last through road (LTR). However, the exact effect of these system variables on the flow rate at the exit of the LB in an empty heading is not known. The installation of LBs in South African coal mines is generally carried out based on experience. This can result in overor under-ventilation and may increase the cost of providing ventilation or cause accidents, respectively. In this paper, using computational fluid dynamics (CFD), the air flow rate at the exit of the LB in an empty heading was estimated using full-scale three-dimensional models. The CFD model used was validated using experimental results Firstly, the settings of these three system variables were varied, the flow rates at the exit of the LB were measured, and finally the results were used to calculate the effect of each system variable. The outcome is a mathematical formula that can be used to estimate air flow rate at the exit of the LB in empty headings for any practical scenario.This paper will help the coal mining sector in South Africa by providing estimation models based on scientific reasoning for the installation of LBs, and will also serve academia as part of the curriculum towards educating future mining engineers."

Jan 1, 2016

By B. Orgilbayar, B. Unursaikhan, S. Sukhbat, Ts. Zagarzusem, D. Baasanjav, L. Jargalsaikhan, E. Otgonjargal, N. Sugir-Erdene, Ts. Soyolmaa

This study has investigated the efficacy of the gravity beneficiation method based on gravitation and centrifugal forces for manganese ore. Powdered samples of manganese ores from the Unagad deposit in Mongolia were analysed for their element and mineralogical composition using ICP-MS and X-ray powder diffraction (XRD). The analysis presented the mineralogical compositions of the ores as hydro goethite, manganese minerals and magnetite, gangue minerals as quartz, albite, orthoclase and microcline of manganese ore. Manganese minerals are white in colour and have micro-veinlet, fine grained-aggregates associated with gangue minerals. The most important manganese minerals are hausmannite, pyrolusite, rhodochrosite, and manganosite. The composite of feed containing 17.31 % Mn and 36.3 % SiO2 was processed in a shaking table. In the experiment, a concentrate assaying 41.37% Mn was obtained from this composite with 65% recovery. In another experiment, f80=0.074 mm particle size ore was used in the MGS concentration test. A concentrate containing 38.34 % Mn with 75.2% recovery was produced in this experiment. The results showed that it is possible to obtain concentrate through gravity processing of manganese ore, which is an economically beneficial process for producing a product of a standard requirement. Keywords: Manganese ore, gravity separator, centrifuge, shaking table 1. Introduction

Jan 1, 2020

By E. J. Magri, A. Couble

Kriging estimates of geological resources are sometimes conditionally biased because the kriging plan contains too few samples. This may be done purposely in order to match the variance of the estimates to the true block dispersion variance. This work aims at evaluating the influence of conditional bias over the ultimate optimum pit design in relation to its shape, size and NPV (Net Present Value of profits). It has been restricted to two real case studies: a ‘carrot shaped’ gold porphyry in northern Greece and a manto-typeexotic copper deposit located in northern Chile. The methodology applied to each deposit consisted of generating a ‘real block model’ and four resource estimates by the use of conditional simulation and the application of four different kriging plans to the drillhole databases respectively. The estimation models vary in smoothness and conditional bias. Ultimate optimum pits were determined for the ‘real’ and the four different kriging models. Pit comparisons lead to the following conclusions: •In the worst case, conditional bias overestimated the project's NPV by 32% and 5% for the gold and copper deposits respectively. •The overestimation of high grades is more relevant than the underestimation of low grades. This resulted in a tonnage over-extraction of 148% and 1% for the gold and copper deposit respectively. This difference was attributable to the vastly different geometry of the deposits. •The smoothing effect of kriging, without or very little conditional bias, produced open pits that were different to the ‘true’ (ideal) ones and furthermore, underestimated the project's NPV by 10% and 6% for the gold and the copper deposits respectively. •Other factors that influence the optimum open pit design and to some extent control the effect of conditional bias are: the cut-off grade, the orebody geometry and distribution of grades within it and the amount of over-burden. Keywords: conditional bias, ultimate pit design

Jan 1, 2003

By K. C. Corin, M. Tadie, N. Ndamase

Fresh water conservation efforts and strict environmental regulations have forced the mining industry to reduce freshwater consumption and effluent discharge. This is achieved by recycling process water back to mining processes. The performance of flotation circuits depends on the pulp chemistry. When process water is recycled to flotation cells, organic and inorganic species that have accumulated over time alter the pulp chemistry. The presence of accumulating ionic species such as SO4 2- and S2O3 2- has been found to hinder the adsorption of collector ions onto mineral surfaces. Sulphide minerals are semi-conductors; electrochemical reactions take place on their surfaces. The adsorption of collectors onto mineral surfaces takes place via electrochemical reactions. This study, therefore, aims to investigate how the presence of accumulating ionic species at varying ionic strengths affects the adsorption of sodium ethyl xanthate onto chalcopyrite from an electrochemical perspective. Synthetic plant water comprised of single salts with varying ionic strengths was used. Rest potential measurements were conducted to investigate collector-mineral interactions in the presence of these ionic species. Microflotation tests were performed to determine whether the presence of these ionic species affects mineral floatability. Higher chalcopyrite recoveries were achieved in the presence of SO4 2- than in the presence of S2O3 2-. Rest potential measurements were found to successfully predict microflotation performance in the presence of the ions of interest. Keywords: Flotation water quality, electrochemical adsorption; xanthate collectors

Jan 1, 2020

By S. V. Mkhatshwa

The purpose of the study was to investigate the factors which affect the performance of the loading and hauling fleet and also find possible solutions to eliminate these factors, so that the daily tonnages required could be produced .This is due to the high demand of manganese required by clients. The investigation strongly focuses on the performances of the three 777D Caterpillar trucks and the R984 C Liebherr Litronic Hydraulic Excavator. In the content of the study, these machines are used to remove and move the low grade manganese (also known as the top cut overburden) in order to expose the high grade manganese from north pit to dump 4. The objectives of the project were to determine the actual performance of the loading and hauling fleet per shift, compare the actual and the theoretical performance and identify areas that need to be improved. To achieve the goals set for the project, a number of activities were carried out. ?Perform a time study to compare the performance of the loading and hauling fleet with the manufacturer specifications ?Match the equipments analysis for Loading and hauling ?Road conditions analysis ?Rolling resistance and Road Gradients analysis ?Operating cost analysis.

Jan 1, 2009

By B. Rezai, Z. Pourkarimi, M. Noaparast, S. Chehreh Chelgani

Nanobubbles (NBs) flotation separation can be an indicator for improving the efficiency of fine particles through the conventional process. Since flotation reagents such as frothers can reduce bubble size, they can potentially be used for the generation of NBs and develop a selective NB flotation separation. This study explored the flotation separation of fine phosphate particles from their associated minerals in the presence of NBs, which were generated by using a phosphate flotation reagent (Flo-YS: collector-frother). The results of flotation tests showed that in the presence of NBs, the flotation efficiency was significantly improved. However, in the presence of NBs, surface chemistry analyses (Fourier Transform Infrared Spectroscopy and High-Performance Liquid Chromatography) illustrated that the collector adsorption on the surface of phosphate particles decreased. A comparison between outcomes of various phosphate flotation conditions indicated that increasing the flotation efficiency in the presence of NBs may be due to the aggregation of fine particles by the generated NBs, and also selective adsorption of NBs (hydrophobisation) on the surface of particles. In other words, generating NBs by selective collectors may increase efficiency and decrease the collector consumption of a flotation process. Keywords: Phosphate, selective separation, fine particles, collector-frother, efficiency, mechanical flotation cell

Jan 1, 2020

By C. G. Carey, M. P. Mullins

BHPBilliton is a large (US$32bn market capitalization) diversified mining group. Significant organic growth is planned through the development of a number of mining, processing and oil and gas projects, totalling some US$5.2bn over the next three years. The investment standards underpin the capital approval process, and incorporate the requirements for range and risk analysis of key input variables, including mineral resources. Public reporting codes for mineral resources and ore reserves (such as JORC) stipulate deterministic reporting of estimates, but are generally silent on any requirement for range or risk assessment, although they acknowledge the risk and uncertainty in the production of resource estimates. In contrast, public reporting of petroleum reserves allow for the use of either deterministic or probabilistic estimation, and for the latter, mandate the level of confidence required for proven versus probable reserves. Conditional simulation techniques, popular in the petroleum industry, provide an ideal tool forrange and risk assessment of the range of outcomes of key resource parameters, such as tonnagesand grades. Examples of a diamond deposit and of a porphyry copper deposit are presented. The understanding and quantification of mineral resource risk through a technique such as conditional simulation provides quantified information on the potential upside or downside. These techniques should be more widely utilized in the high-risk minerals extraction industry. Keywords: mineral resources, conditional simulation, risk, capital investment standards, BHPBilliton.

Jan 1, 2003

By K. Kabezya

A study on slag dispersion in a model of bottom-blown bath smelting converter was undertaken at room temperature. The aim was to investigate the behaviour of the dispersed slag phase at various operating conditions with very high gas flow rates in low slag volume (10%) systems. For simulation purposes water, paraffin-oil, and air were used to represent the bulk steel, molten slag, and gases respectively in a one-fifth cold model of the commercial 100 t Creusot-Loire-Uddeholm (CLU) converter used in the manufacture of stainless steel in South Africa. Dimensional analysis was done to correlate mathematically the dispersed phase holdup with the operating conditions and the modified Froude number. The overall expression of the holdup revealed that the dispersed slag phase decreased with the vertical distance from the original interface between the liquid phases. The dispersed phase also decreased with the radial distance in the water plume zone toward the sidewall. The holdup was apparently much higher on the side of the reactor where there were no tuyeres. The modified Froude number ensured the correlation between the model and the prototype.

Jan 1, 2014

By H. Moslemi

Metal sulphides are usually semiconductor and their electrical conductivity is low; therefore they are sources of electrons and promote electrochemical reactions. This phenomenon is of significant importance in sulphide flotation. The formation of a hydrophobic surface on the sulphide minerals is the result of various electrochemical reactions. Potential difference in the mineral-liquid interface plays an important role in the kinetics of the reactions, and consequently, on the flotation behaviour of sulphides. The value of the potential difference is influenced by different oxidation-reduction reactions at the interface area, and is measured by a two-electrode system in which an electrode is applied as reference electrode. In this study, we attempted to measure open-circuit potentials of pyrite, pyrrhotite, and steel electrodes with respect to the reference electrode. To verify the results, two reference electrodes, saturated calomel and gold, were used. Time-potential relations with respect to both reference electrodes show that the potential of both pyrite and pyrrhotite increases with time; however, this trend decreases for steel except when at pH 12. The results show a potential drop by an increase in pH value, except for steel, for which the opposite holds. This paper discusses galvanic interactions between minerals and grinding media in the grinding circuits, as well as among other minerals in the flotation processes.

Jan 1, 2012