Search Documents

By H. Ogasawara

Information on rock stress is important for safe mining in seismically active ground. On a major gold mine, a few tens of crews are continuously conducting geological drilling with small pneumatic machines. However, stress measurements are not often carried out in South African deep-level gold mines. One of the reasons is the drilling diameter that overcoring requires, which is much larger than the diameters used in regular geological drilling, e.g. Boart Longyear Metre Eater, which drills AQ or BQ holes. Larger diameter holes result in slower drilling advance, more load in transportation and handling at sites, and higher cost. In order to enable overcoring in BX size (60 mm diameter), we modified the compact conical-ended borehole overcoring (CCBO) technique that has been suggested by International Society for Rock Mechanics (ISRM) and was originally designed for NX drilling (76 mm diameter). With a single overcoring, the 3-D stress tensor can be determined. We tested this modified method at a depth of about 3 km at Moab Khotsong mine in South Africa. We worked with drilling crew who usually work at geological drilling with the Metre Eater. In January 2011, we tried using regular geological drilling tools (a sequence of a normal BX bit, reamer, and rod) without success. In August and September 2011, introducing stabilizers and thin BX bits, we succeeded. We could complete a cycle of procedures necessary for an overcoring, including shaping the borehole-end conically, glueing a 16-element strain cell, and overcoring, within 2.5 hours. Only 10 cm overcoring is needed, which increases the chance of successful overcoring in heavily fractured conditions. This modified method is suitable for up-dip holes to depths of 10-15 m from tunnels, and has the potential to be widely used at the initial stage of geological exploration drilling at many localities.

Jan 1, 2012

By G. Mucsi, F. Kristály, R. Szabó

Kaolin is one of the most important ingredients in porcelain manufacturing. Its main phase is clay mineral containing aluminum hydrosilicate, namely kaolinite. Beside kaolinite it also contains quartz, illite and feldspars, which impair its applicability. Kaolin is a non-reactive material, but metakaolin can be produced by heat treatment (calcination) of kaolin, which is also used by the cement and concrete industry due to its latent hydraulic (pozzolanic) properties. Beside thermal activation, reactive materials can also be produced by mechanochemical activation in general. This paper deals with the mechanochemical activation of kaolin. The raw material was classified into various size fractions, then ground in a batch stirred media mill under varying circumstances (residence time, circumferential velocity). After grinding, the structural changes of the products were investigated by X-ray diffractometry (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). In addition, the particle size distribution of the ground material was determined by laser scattering. As a result of the grinding experiments and analytical measurements of the products, it can be clearly seen that reactivity of kaolin can be improved significantly by mechanical activation in a stirred media mill, but due to its high energy density the circumstances were optimised carefully to avoid aggregation. Keywords: Kaolin, grinding, stirred media mill, mechanical activation, material structure

Jan 1, 2020

By C. Birch

"Mineral reserve statements as well as optimizing mine planning require a block model with grades for each mining block. A cut-off grade is determined by considering the mining costs as well as the expected revenue for each block. These grades are estimated using various techniques, but in reality there is uncertainty in the grade values. These uncertainties result in two types of error. A type I error is where material is classified as ore and mined, but the true value is below the cut-off grade and the material is therefore waste. This material constitutes dilution. The type II error is where material is estimated to be below the cut-off grade and is classified as waste, whereas the true grade is actually above the cut-off grade. This material is not mined and the value is lost.This research considers the value of the lost ore and the costs of dilution under various degrees of uncertainty. Simulation using @Risk and mixed integer linear programing (Excel Solver) is used in a financial optimizer model to maximize either profit or net present value. This is applied to four Witwatersrand tabular gold deposits to investigate the impact of block grade uncertainty on cut-off grades.When optimizing for profit, value may be added by adjusting the cutoff grade slightly downwards. When optimizing for NPV, value may be added by lowering the cut-off grade significantly for the lower discounting rates. At higher discount rates, the lowering of the cut-off grades should be reduced, and in some cases an increase in cut-off grade may be required. Each mine reacted differently to the optimization and thus there is no single rule that can be applied across all tabular Witwatersrand gold deposits."

Jan 1, 2017

By M. Weir, J. R. Cutland, L A. J. Pronk van Hoogeveen

"A computer system for the design of open pits to mine stratiform orebodies has been developed for use at Nchanga Consolidated Copper Mines, Ltd. The particular requirements of such a system, for example, the accuracy of representation of geological detail and the ability to follow footwalls, arc described in this paper, together with the methods that have been adopted to satisfy them.A modified version of the Open Pit Design Program of Rio Tinto Zinc Consultants, Ltd. is incorporated in the system and the geological data are converted into a form usable by the computer by means of a pencil follower. Some of the uses which have been made of the system are described, with reference to the long- and medium-term planning of the Nchanga Open Pit, the major producing pit at Chingola Division."

Jan 1, 2014

By I. Ashmole

The dimension stone industry is not widely known or appreciated within the mainstream mining industry. This is in spite of the fact that the industry has grown at an average of over 7% per annum since 1980, and is estimated to now have a global turnover in excess of US$ 60 Billion per annum. Production technologies, particularly in the developed world where labour costs are high, have developed rapidly over the past two decades. Aligned with this, there has been a significant trend in adoption of a more professional mining approach in the exploration for and operation of dimension stone quarries. In fact, in the experience of the authors, mining a dimension stone deposit successfully if often more challenging from a mining engineering point of view than many conventional surface mines. This paper gives an overview of the industry and then proceeds to discuss best practice in exploration for dimension stone and to outline the latest technologies applied in mining of dimension stone. These technologies are varied and the specific combination of technologies applied in any given quarry is determined by both the physical properties of the material as well as the influence of geology which significantly impacts on the recovery of saleable material and hence the economics of the quarry.

Jan 1, 2008

By N. Sacks, N. B. S. Magagula, I. Botef

"Low-pressure cold gas dynamic spraying was used to deposit WC-4wt%Ni and WC-4wt%Ni-1wt%Mo coatings onto mild steel. Dense coatings with very low porosities were produced. No decarburization occurred during deposition and no deleterious phases were formed. The coatings were subjected to standardized material characterization tests, as well as slurry abrasion testing to assess their wear behaviour. The wear tests were conducted in synthetic minewater-silica slurries, while distilled watersilica slurries were used as a control. The hardness of the coatings, 512HV0.3 and 458HV0.3 for WC-4wt%Ni and WC-4wt%Ni-1wt%Mo respectively, are comparable to those achieved using high-temperature coating processes. The abrasion wear rates for both coatings were less than 5 mg/min and 10 mg/min in the distilled water-silica and synthetic mine water-silica slurries respectively. The approximately 50% increase in wear rate in the synthetic minewater slurry is attributed to a synergistic corrosive wear mechanism. The predominant wear mechanisms were identified as binder smearing and delamination, with carbide grain fracture and pull-out. IntroductionSlurry abrasion is a common phenomenon in mining operations, particularly in pipelines transporting, for example, sand-water slurries. This type of wear can cause pipeline fracture, shortened operational lifetimes, and impede pipeline efficiency. To reduce or limit abrasion, thermally sprayed tungsten-carbide-based coatings are often used as pipe linings (Kanchan et al., 2010). This is due to their attractive mechanical properties, which include high wear resistance, stiffness, hardness, compressive strength, and tensile strength. These properties are provided by the coating microstructure and composition, which is a blend of hard, wear-resistant tungsten carbide (WC) particles embedded in a fracture-tough metallic binder phase (Brookes, 1997). Cobalt (Co) is the most commonly used binder due to its excellent wetting of the WC phase and moderate mechanical properties; however, its application is limited to non-corrosive environments as it has a low corrosion and oxidation resistance (Andren, 2001). Nickel (Ni) may also be used as a binder, and has been shown to have superior oxidation and corrosion resistance, but in some applications may not have the required mechanical properties (Kim et al., 2006)."

Jan 1, 2016

By O. T. Konina, V. A. Masloboev, A. V. Svetlov, E. A. Krasavtseva, D. V. Makarov, A. A. Goryachev

Dusting phenomena have been examined at the tailings storage facility of Apatit JSC Kirovsk, a mining operation located in the far north of the Russian Federation. The material composition of the tailings was identified. Existing dust suppression methods were examined. Field observations were undertaken and official data was obtained from the Murmansk Administration for Hydrometeorology and Environmental Monitoring, and analysed. A database was built for forecasting dusting according to critical scenarios in order to estimate the peak MPCs of suspended solids in the atmospheric air. Mitigation measures were formulated and recommended to the mining operation. Keywords: Mineral dust particles, apatite-nepheline ore concentration tailings, suspended solids MPC, climate change

Jan 1, 2020

By R. R. M. Cousens, W. S. Garrett

SYNOPSIS The paper gives a background to the water hazards of the so-called West Wits Line and refers to some geological aspects of the Wonderfontein Valley in which the West Driefontein mine property lies. It describes the precautions taken against flooding during shaft sinking, development and stoping; these include cover hole drilling with cementation, provision for water storage in worked-out areas, installation of water tight bulkhead doors and pumping capacity well in excess of the mine's normal requirements. The plan of campaign adopted after the inrush took place is explained and the reorganization and expansion of pumping arrangements are discussed. When it became clear that the only means of saving the mine was to construct plugs to isolate the inrush while still maintaining all emergency pumping measures, the work was put in hand with the utmost dispatch. In considering the design of the plugs a number of major factors had to be taken into account. The most vital was the need for speed which was complicated by difficulty of access to the plug sites because of the huge volumes of water flowing in the drives. How this and other factors affecting plug design and construction, leakage problems, sequence of operations and final closure of the valves, were overcome is detailed in the paper. INTRODUCTION The inrush of water into the West Driefontein mine, the biggest gold producer in the world, which began on 26th October, 1968 and continued unabated for 23 days before the flood was stemmed, was unprecedented in the history of mining. Also unprecedented were the tremendous efforts and organization which made it possible to bring the situation under control and so save the mine from being lost for a matter of years. BACKGROUND Before going into details of how the situation was brought under control it is appropriate to consider the background to the event. The water problem on the so-called West Wits Line has been recognized for many years. As far back as 1912 the Pullinger Shaft, situated in the centre of what is now the Venterspost mine property, had to be abandoned because there were no means then available of coping with the large quantity of water encountered. To appreciate what vast quantities of water were involved, it helps to refer to some geological aspects of the Wonderfontein valley in which the West Driefontein property lies. The narrow tabular Witwatersrand gold-bearing beds, which dip at about 25 degrees towards the south, are overlain by a surface layer of dolomite which reaches a maximum thickness of some 4,000 ft at West Driefontein. A number of vertical syenitic dykes intersect the valley more or less at right angles to its course (Fig. 1). These dykes are about 150 ft thick on average and are spaced at about eight-mile intervals in the West Driefontein area. They penetrate both the dolomite and the Witwatersrand beds and as they are impervious to water they divide the valley into a series of large underground water compartments.

Jan 5, 1969

By J. Moema, L. Mampuru, M. Phasha, D. Mkhonto

The global liquified natural gas (LNG) storage market size is projected to reach USD17.5 billion by 2025. Currently, owed to its high toughness, tensile strength, and excellent weldability, the 9% nickel steel is the most used in building infrastructure for cryogenic applications such as the construction of tanks and pipes for storage and transportation of LNG. However, this alloy is not readily available because of its complex production process and high cost. This provides an opportunity for suitable alternative materials to build infrastructure for cryogenic applications. Among strong contenders is the Fe-Mn based alloys, which have sparked global interest due to their desirable properties such as relatively lower density, low cost, high toughness and strength, due to a high manganese (Mn) content. These attractive properties render Fe-Mn based alloys preferred candidates to replace traditional steels in engineering applications in which strengthweight ratio is critical. In response, as a build-up to designing and developing austenitic Fe- Mn alloys, the present study employed density functional theory (DFT) based first-principles computational materials modelling technique to investigate the structural, thermodynamic, and magnetic properties of binary Fe-Mn alloy composition in competing FCC, HCP, and BCC crystal structures. Using this approach, it was possible to unravel the key underlying elastic properties that are directly correlated to experimental tensile strength and high toughness in binary Fe-Mn alloys. Besides successfully validating the existing experimental data, the current predicted properties and the deployed approach will serve as a benchmark from which further alloying required to improve other properties will be conducted.

Mar 4, 2025

By M. Rudolph, A. D. Renno, H. Wu

In this study, synthetic pure cassiterite and cassiterite doped with Fe were successfully produced by sintering. Their crystal structure and chemical compositions are characterised by optical microscopy, X-ray powder diffraction (XRD) as well as scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) based chemical composition analysis. The electrostatic behaviour of synthetic and natural cassiterite was studied by electrophoretic measurements. Their floatability was studied by microflotation with two types of anionic collectors. Results show that the cassiterite floatability with these collectors behaves differently and lead to two opposite results: Natural cassiterite (enriched with Fe) > undoped pure SnO2 by using sulfosuccinamate (Aerosol® 22) Undoped pure SnO2 > Fe3+ doped > natural cassiterite (enriched with Fe) by using styrene phosphonic acid (SPA). Keywords: Synthetic cassiterite, lattice impurities, flotation, zeta potential, Aerosol® 22, styrene phosphonic acid

Jan 1, 2020

By C. Chingwaru, W. Chingwaru, J. Vidmar

"Zimbabwe is endowed with rich deposits of minerals such as diamonds, platinum, coal, uranium, lithium, gold, antimony, iron, and chrome. Bioleaching has been implemented as an efficient and low-cost method to extract metals such as copper, cobalt, and gold from sulphide and/or ironcontaining ores and mineral concentrates in a number of countries around the globe. Zimbabwe, despite being a world leader in mineral wealth, has gone through years of economic stagnation which have brought with them energy shortages. Bioleaching is an innovative way to recover minerals from ores using relatively low-capital-cost and non-polluting technology. Principally, iron- and sulphur-oxidizing bacteria can be used to oxidize iron and sulphide to ferric iron and sulphuric acid, respectively, and the ferric iron oxidizes the insoluble metal sulphides to soluble metal sulphates that can be readily recovered from solution. Although some minerals such as gold are inert to biological reactions, they can be liberated using bacteria that act on certain types of ores and other minerals that co-occur with these minerals. The geology of the mineralized areas in Zimbabwe, rich in chalcopyrite / pyrite, allows a number of microorganisms to be used for the extraction of minerals by bio-oxidation. This paper reviews the potential of bioleaching in the country. IntroductionZimbabwe has rich deposits of minerals including diamonds, platinum, coal, uranium, lithium, gold, antimony, iron, and chrome. Bioleaching is defined as the use of microorganisms to facilitate the extraction of metals from sulphide or iron-containing ores or concentrates (Rawlings, 2004, 1997). Bioleaching has been shown to be an efficient (Blowes, Ptacek, and Jurjovec, 2003; Nordstrom and Southam, 1997; Schippers, 2004) and low-cost (Schippers et al., 2010) method to extract minerals in many countries around the globe. For example, aerobic Fe(II)- and sulphur-oxidizing bacteria have been shown to be up to two orders of magnitude more efficient in the oxidation of pyrite than the chemical processes (Blowes, Ptacek, and Jurjovec, 2003; Nordstrom and Southam, 1997; Schippers, 2004). Additionally, bioleaching can be used to extract minerals from low-grade ores, sulphidic waste rock dumps, and tailings efficiently (Schippers et al., 2010)."

Jan 1, 2017

By D. Saramak, T. Gawenda, A. Stempkowska, Z. Naziemiec

The aim of the paper is to discuss the possibility of producing aggregates with an increased content of regular particles, as well as to present a method of aggregate production which has not previously been used in the industry. Traditional aggregate production circuits require the application of three or four grinding stages (depending on the particle size of the feed), but for fine particle fractions of aggregates, irregular grains occur on average with a content of 10%. The innovative technological circuit can produce the aggregates with the content below 3%, even in a single- or two-stage crushing circuit. Downstream jig beneficiation of such prepared material results in higher separation sharpness, lower probable error index (Ep) and imperfection (I). Keywords: Aggregate production, jig beneficiation, mineral processing, raw materials

Jan 1, 2020

By L. Gutierrez, R. Yepsena

Enargite in porphyry copper deposits is an important mineral as it displays good floatability under the presence of the collectors usually used in the flotation of copper sulfides. As a result, copper concentrates grades are reduced. As scarcity of water resources is a problem relevant to Chilean mining, the use of seawater is a feasible solution. The behaviour of copper sulfides and molybdenite in the process of flotation in seawater was previously studied but not for enargite. The objective of this research is to study the behaviour of the enargite in different conditions of electrochemical potential during the process of flotation using seawater. The study was carried through micro-flotation tests using pure samples of enargite, at Eh values ranging from -300 to 500 mV(SHE), both in seawater and aqueous solutions containing calcium and magnesium. The results show that at pH 10.5 in seawater, the enargite and chalcopyrite recoveries are reduced throughout the whole range of Eh studied. At pH 9 in seawater, enargite and chalcopyrite are depressed under reducing and slightly oxidising conditions. The recovery of both minerals drastically decreases at Eh values lower than -100 mV and greater than 400 mV. The behaviour of enargite in seawater flotation differs from that observed in conventional water, since in the latter case the recovery of enargite decreases at higher potentials close to 500 mV. Keywords: Enargite, flotation, seawater, redox potential

Jan 1, 2020

By T. H. Yang, Q. K. Wang, T. Song, J. W. Zhou

The grinding circuit can be one of the most important mineral processing circuits in plants. Along with the application of large-scale milling machines, the design and optimisation of the operation strategy for grinding circuits is more complicated. An in-house grinding process simulation tool was developed to mass balance, model fit and simulate crushing, grinding and classification circuits. An industrial grinding and classification circuit in a copper mine was modelled, and the modelling parameters were verified by a particular group of plant survey data. To justify the prediction ability of the fitted models, the model predictions under different operation conditions were compared with another group of plant survey data. Then the model predicted the effects on the circuit of changing operating conditions. Circuit analysis of the comminution process for water feed to a SAG mill, water feed to sump, the rolling speed of a SAG mill and the percentage of ball filling in a SAG mill was put into practise, based on the simulation results. The simulation results can be used to help plant operators understand the features of the comminution process and may help to build a knowledge library for process control. Keywords: Process modelling, grinding, comminution, circuit analysis

Jan 1, 2020

By C. Hartford, T. Holmes

Bulk-solids handling systems are often the most over-looked component and thereby weakest links in a processing plant’s value chain. Since their performance can dictate that of the entire operation, they actually deserve special attention. When designing a liquid handling plant, density and viscosity are well known and commonly used as design parameters. Bulk solids however, differ. While the design process is similar, the relevant parameters in handling bulk solids are instead friction, cohesive strength, compressibility, and permeability. These then vary depending on the mineralogy, particle size distribution and shape, moisture content, storage time-at-rest, temperature, and consolidation pressure. With so many variables, it becomes important to characterize each individual bulk solid across the full range of representative process conditions within the handling system, plant wide – or if you are not very lucky, suffer the consequences of poor material flow. Measuring flow properties and applying them correctly in bulk solid handling system design reduces project risk, saves significant capital, and drastically increases throughput, especially when done in the early stages of a project. Keywords: Flow Properties, Bulk Solids, Process Conditions, System Design

Jan 1, 2020

Your Council has pleasure in submitting its report for the year ended 30th June, 1970. COUNCIL The following served as Office Bearers during the year under review: Messrs J. K. E. Douglas (President), V. C. Robinson and Prof D. D. Howat (Vice-Presidents), R. C. J. Goode (Immediate Past President) and D. G. Maxwell (Honorary Treasurer). Members of Council: Mr. R. J. Adamson, Dr. M. G. Atmore, Mr M. Barcza, Dr J. M. Bereza, Messrs H. Britten, H. E. Cross, A. R. C. Fowler, G. W. Holl, Dr J. P. Hugo, Messrs N. A. Honnet, P. Lambooy, Prof J. de V. Lambrechts, Mr C. E. Mavrocordatos, Dr J. T. McIntyre, Messrs J. Meintjies, T. C. A. Meyer, J. A. Nixon, Prof R. P. Plewman, Dr R. E. Robinson, Messrs J. F. Reid, H. Simon and P. W. J. van Rensburg. Ten Council meetings were held during the year with an average attendance of seventeen and the standing committees held 45 meetings. FINANCE The annual accounts, which are attached to this report, show an excess of expenditure over income of R4,608 compared with R2,124 last year. This deterioration can be attributed largely to two important factors, namely an increase in secretarial fees of RI, 789 and an increase in the loss on the Journal from R2,343 to R3,508. In addition, our contribution to the expenses of the Federation of Societies of Professional Engineers increased by R607 from R549 to R1,156. The increase in secretarial fees is partly due to our increased demand for services and partly to increased salaries. In order to maintain its essential services it has been necessary for the A.S. & T.S. to increase salaries in order to keep pace with commerce and industry. With regard to the Journal, we did not expect immediate dramatic results from the changes that were effected as from the beginning of last year in the arrangements for publication. However, the improvement has been even slower in materialising than we expected. This situation is being watched carefully and we will not hesitate to make further changes if necessary. It became clear early in the year that the financial position was deteriorating and your Council decided that it was essential to meet the situation by raising subscriptions and entrance fees. At the same time it was decided that there are no grounds for a distinction between Town and Country members and that in future the scale for the compounding of subscriptions should be based on anticipated future membership, rather than past membership. These changes have had only a minor effect on the accounts under consideration. The MacArthur Forrest Memorial Fund shows an excess of income over expenditure of R132 and the total fund was, therefore, increased by this amount to R4,338. The balance sheet shows that the market value of quoted shares and debentures decreased during the year from R13,059 to R6,567, while accumulated funds now amount to R17,959 compared with R22,567 last year. It will also be noted that we are holding R25,844 on behalf of the Symposium on Opencast Mining. MEMBERSHIP Twenty-eight Fellows, twenty-four Members, seventeen Graduates, twenty-five Associates and twenty-seven Students were elected during the year. Four Members were admitted to Life Membership; Five Members were transferred to the grade of Fellow; one Student was transferred to the grade of Member; two Graduates and one Student were transferred to the grade of Member; six Students were transferred to the grade of Graduate; One Associate was transferred to the grade of Fellow; One Associate was transferred to the grade of Graduate. One Fellow, one Member, six Graduates, four Affiliates and ten Students were removed from the Membership Roll in terms of by-law 7.7.1. Your Council records with deep regret the death during the year, of the following: R. A. H. Flugge-de-Smidt, C. S. McLean, Dr H. J. van Eck, (Honorary Life Fellows), J. C. Humphreys, O. Lazar (Life Fellows), D. G. Beadle, J. G. Craig, P. U. Fisher, R. G. McConnell, J. H. Moore, S. Sterling, L. R. Ulyate (Fellows), H. H. Burger, E. A C. Dickson, R. Jack, S. Ring (Members), M. J. Worrall (Graduate). A comparative statement of the membership as at 30th June, 1970, and the end of the previous year is shown in the following tabulation: 30th June 30th June Honorary Life Fellows 10 8 Honorary Fellows 6 6 Life Fellows 189 191 Fellows 514 530 Members 448 465 Graduates 68 80 Associates 155 172 Students 162 161 1,552 1,613 RECLASSIFICATION OF MEMBERSHIP The designations of grades of membership were altered to accord with the practice in professional institutes both here and overseas and members were advised of the new classifications. MEMBERSHIP DRIVE A committee was established to organise a drive for membership as it was felt that there are numbers of persons in our mining and metallurgical industries who are not yet members but who qualify for membership. Members of the committee were allocated responsibility for campaigning in sections of industry and for publicising the aims, objectives and advantages of belonging to the Institute.

By L. Zhang, Y. Zhou, H. Wang, C. Mo

Fluorination of magnetite (Fe₃O₄) by NH₄HF₂ was investigated using simultaneous thermogravimetry and differential thermal analysis (TG-DTA), and observing the morphology and phase changes using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffractometry (XRD). The results indicate that fluorination with the involvement of oxygen begins at room temperature, peaks at 178.40C, and is completed at 2000C with the formation of only (NH₄)₃FeF₆. On heating, (NH₄)₃FeF₆ gradually releases NH₄F by the formation of NH₄FeF₄ at 2590C, then (NH₄)0.18FeF₃ at 3270C, and finally FeF₃ with minor FeF₂ at 4000C due to the partial reduction of Fe (III) to Fe (II). At 5500C, FeF₃ is oxidized to FeOF/Fe₂O₃.

Dec 13, 2022

By P. J. Petit

"The complex planning required to achieve any planned production yields multiple and dissociated responses over the life of project (LOP). The customary decision-making process negates the possibilities of developing optimized and integral solutions from operating levels up to business and strategic levels. This results in an inefficient project or overall underperformance of the operation.In the project setting, disconnected trade-offs and improved performance studies become inadequate, because they are site-specific and use only a few comparative parameters. They are often based on a small data-set.Decisions taken to achieve overall objectives require the correct determination and dissemination of key performance indicators (KPIs). The KPIs indicate efficiency in operation, whereby the marginal rate of technical substitution corresponds to the rate of production. It is the necessary condition for optimization. Performance realization for sustainability follows optimization modelling, the latter often being presented with financial results such as business net present value (NPV). It considers techno-financial constraints and provides a strategic and aligned outlook of KPI decisions for an enhanced and integrated outcome.This paper explains a mining case study that is rendered efficient, and through business optimization (BO) short-term and sustainable targets are reached. Business optimization increases the NPV by 14.7%. This is achieved by challenging conventional decision-making associated with maximizing business value by including environmental externalities within the LOP."

Jan 1, 2016

By A. Doroudgar, H. Noferesti

Unstable rock failure or rock bursting is one of the most dangerous problems in deep hard rock mines. This type of failure, that occurs uncontrollably, is associated with a significant release of strain energy from the surrounding rock. In this study, the numerical simulation of unstable rock failure was carried out using the three-dimensional explicit Lagranian finite-volume finite difference method to identify the onset and location of unstable failure events in the model. On this basis, a numerical simulation of mine pillars with width-to-height ratios of 0.5, 2 and 3 was performed. A criterion was developed, based on the calculation of the elastic strain energy, to determine the prone areas for the initiation of rockburst in the models. The results of this study showed that, in softer loading systems, due to large amounts of stored elastic strain energy, an unstable equilibrium is established, which leads to the rapid transfer of strain energy to the rock in the form of violent failure. It was also found that the unstable failure starts at the corners and free surface of the model. The new criterion developed in this study may help predict the occurrence of rockbursts in slender pillars and the design of pillars to control human and financial losses caused by this phenomenon.

Nov 27, 2024

By J. D. Zhou, F. Yang, X. G. Bi

"In this investigation, the phosphorus distribution ratios in the CaF2 system and B2O3 system dephosphorization slags for high-phosphorus hot metal pretreatment were measured by an indirect method under laboratory conditions. Firstly, the phosphorus distribution ratio between liquid slag and solid iron was measured, and then the phosphorus distribution ratio between liquid slag and hot metal was calculated. Phosphorus capacity was calculated in terms of the composition and optical basicity of the slag. Dephosphorization slag was also studied by scanning electron microscopy, energy dispersive analysis, and X-ray diffraction analysis. The experimental results show that the phosphorus capacity of the B2O3 slag system is much greater than that of the CaF2 system. It is demonstrated thatB2O3 can completely replace CaF2 as fluxing agent for high-phosphorus hot metal pretreatment. With CaF2 as fluxing agent, the phosphorus capacity increases with increasing CaO content in the slag, but the phosphorus distribution ratio decreases. B2O3, when used as fluxing agent, can react with high melting point phases such as 2CaO·SiO2 and 3CaO·P2O5 in the slag to form new phases with low melting points such as 11CaO·B2O3.4SiO2, 2CaO·B2O3.SiO2, and Ca9.93(P5.84B0.16O24) (B0.67O1.79), thereby acting as a fluxing agent. When the ratio of w(B2O3)/w(CaO) is 0.16, the phosphorus distribution ratio reaches its maximum value, that is, the dephosphorization ability of the slag is at its maximum. IntroductionAs international iron ore prices continue to rise, the development of China's steel industry is facing a lot of pressure. Against this background, development and utilization of domestic high-phosphorus iron ore resources is particularly important. When highphosphorus iron ore is used in ironmaking, the phosphorus content in the hot metal can reach 0.35% or more, and the hot metal must be pretreated. For hot metal with 0.08–0.10% dissolved phosphorus, the traditional hot metal dephosphorization pretreatment technologies are relatively mature. However, when using these methods to dephosphorize hot metal containing 0.35% P or more, the amount of dephosphorization slag can reach 100–150 kg per ton of hot metal. Furthermore, the traditional dephosphorization methods require the addition of large amounts of CaF2 as fluxing agent, and this results in high fluoride levels in the dephosphorization slag. The fluorine in the slag can partially dissolve in water and thereby causes high fluoride concentration in the water and soil. Once the fluoride is absorbed by humans or animals, it can result in toxic effects on the central nervous system and myocardium. In addition, fluoride can accumulate in the environment, and thereby pose a health risk to animals and humans through the food chain (Li, 2007; Liu, Wang, and Dong, 2011, Diao, 2013). The objective of this research is to replace CaF2 with B2O3 as fluxing agent while achieving the expected goals of hot metal pretreatment."

Jan 1, 2016