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[Ferro Alloys Producers Association The South Africa Institute of Mining and Metallurgy www.saimm.co.za Mintek www.mintek.co.za Eskom www.eskom.co.za ]

Jan 1, 2004

By Dolly Chakraborty, S. Ranganathan, S. N. Sinha

Experiments were conducted to study the influence of temperature, particle size and ore/coke ratio on the kinetics of reduction. The rate of reduction increased with temperature. The reduction of iron was completed at shorter time intervals at temperature above 1000ºC. Usually the reduction of chromium commenced after the reduction of iron was almost complete. Reduction was controlled by diffusion at low temperatures and by chemical reaction at higher temperatures. The nature of the reducing agent had a very significant influence on the rate of reduction. The study showed that chromium was converted into the carbide during reduction. Increasing the size of the reducing agent increased the rate of reduction initially. After a critical size, the rate of reduction decreased. However, increasing the size of the ore particle decreased the rate of reduction, initially. Beyond a critical size, it increased. An optimum particle size of the chromite ore and that of coke must be chosen, particularly in the production of agglomerates to achieve maximum degree of reduction.

Jan 1, 2007

By T. Saito, S. Murata

An original concept of JRC-diagram that can evaluate JRC and its size-effect by using a fractal model was proposed. In order to confirm the applicability of the JRC-diagram, first, JRC of the tensile fracture surfaces of a granite and a sandstone were evaluated by both the JRC-diagram and Barton's JRC-profiles, and then, it was compared with the JRC inversely calculated from the peak shear strength that is obtained from the shear test for each fracture using Barton's empirical equation. As a result, JRC evaluated by the JRC-profiles was much smaller than the inversely calculated JRC. On the other hand, it became clear that JRC evaluated by the JRC-diagram is almost the same with the inversely calculated JRC, if the size of interlocking is evaluated correctly. Therefore, for the JRC evaluation, it is thought that the JRC-diagram is more applicable than the JRC-profiles. Als ein neues Verfahren zur Bewertung des Rauheitsindexes JRC für die Bruchfläche von Felsenschichten anhand eines fraktalen Modells, wobei auch der Maßeffekt berücksichtigt wird, wird ein JRC-Diagramm vorgeschlagen. Um die Angemessenheit der Bewertung vom JRC mit diesem JRC-Diagramm festzustellen, wurden die JRC-Werte an einer Bruchfläche zwischen Granit und Sandstein sowohl mit dem JRC-Diagramm als auch mit dem herkömmlichen JRC-Profilverfahren bewertet. Anschließend wurden die durch die beiden Verfahren ermittelten Werten mit den JRC-Werten verglichen, die von den Schertestergebnissen mit Hilfe von Bartonschen Erfahrungsformel zurückgerechnet werden können. Daraus ergab sich, daß das JRC-Profilverfahren ziemlich kleinere JRC-Werte gibt als bei der Zurückrechnung, während die JRC-Werte durch das JRC-Diagramm unter entsprechender Bewertung des Ineinandergreifungsmaßes an der Bruchfläche beinahe gleich sind wie die zurückgerechneten Werte. Diese Tatsache weist darauf hin, daß das JRC-Diagramm eine bessere JRC-Bewertungsmethode als das JRC-Profilverfahren darstellt. Nous avons proposé le diagramme JRC, nouvelle méthode d'évaluer JRC qui est un indice de rugosité superficielle d'une fracture de roche à l'aide du modèle de fracturation, compte tenu de son effet d'échelle. Pour vérifier la validité de JRC évalué au moyen de ce diagramme, nous avons évalué JRC d'une fracture de roche, granite et grès, par le diagramme JRC et le profil JRC, méthode conventionnelle, et les résultats ainsi obtenus ont été comparés avec la valeur de JRC calculée en sens inverse à l'aide de la formule empirique Barton sur la base des résultats de l'essai de cisaillement des fractures. Il en résulte que la valeur de JRC obtenue par le profil JRC était assez faible en comparaison avec la valeur calculée en sens inverse alors que celle de JRC obtenue par le diagramme JRC correspondait approximativement à la valeur calculée en sens inverse à condition d'évaluer l'échelle d'endentement d'une fracture. Par conséquent, nous considérons que le diagramme JRC est une meilleure méthode d'évaluation de JRC par rapport au profil JRC.

Jan 1, 2003

By D. Mkhwanazi

The purpose of the project was to optimize load haul dump (LHD) machinery use as they were spending too much time doing what they should not be doing. During the investigation, the author found that the machine's actual availability was 86% and the utilization ranged between 30% and 42%. This shows that the availability of the machine has met its target. Therefore the main problem was with the LHD utilization and that is what the project focuses on. To satisfy the objectives, the author firstly studied the existing mining data like the key performance indicators (KPIs) in order to analyse the machine's availability and utilization; this is what gave direction to the problem. Secondly the author did a literature review on mines with similar problems. This gave the author ideas on what to look at in approaching such a situation. Thirdly, the author gathered information on what the LHDs are doing on a daily basis by doing a time study. This gave the author an idea of how long it took the LHDs to complete a specific task. The author also interviewed operators and their supervisors in order to find the best practice work. This helped in identifying the problem areas when comparing the best practice work with what the LHDs are actually doing. According to the project results, it was found that the LHDs are underutilized due to shortage of drivers and the long distances the LHDs have to travel for material loading and refuelling. The author recommended that the machine utilization should be improved by training more operators in order to eliminate the 'no operator' downtime; the cost arrangement of this recommendation is included in the report. The author also recommended that the travelling time should be reduced by using tractors instead of LHDs when long distances need to be travelled for material loading. Another recommendation for reducing travelling time was to bring the mobile fuel tank closer to a section; the cost arrangement for this recommendation is also included in the report. Keywords Optimizing, LHD utilization, LHD availability, key performance indicators (KPI), shortage of drivers, long distances, mobile fuel tanks.

Jan 1, 2011

By C. Haberfield, J. Szymakowski

Recent studies by the authors into the behaviour of jointed rock masses using direct shear testing have confirmed that joint spacing has a significant effect on rock mass strength. The rock mass failure envelopes assessed from these tests have been compared to failure envelopes obtained using the Hoek-Brown GSI criterion. Good agreement between measured and estimated GSI strength envelopes where obtained when joint spacing was considered in the assessment of GSI. Les études récentes conduites par les auteurs sur le comportement des joints rocheux employant l'essai direct de cisaillement ont confirmé que l'espacement a un effet significatif sur la force de la masse rocheuse. Les enveloppes de ruptures obtenues pour ces essais ont été comparées à l'enveloppe de rupture obtenue en utilisant le critère GSI Hoek-Brown. Une bonne corrélation a été constatée entre les enveloppes obtenues expérimentalement et les enveloppes calculées par la méthode GSI quand l'espacement des joints a été pris en considération dans l'évaluation de GSI. Kuerzliche Untersuchungen der Autoren betreffs Reaktionen von gebrochenen Felsmassen zu direkter Scherkraft, bestaetigen, dass die Abstaende von Rissen einen deutlichen Einfluss auf den Widerstand der Felsmassen hat. Die Bruchbereiche der Felsmassen die von diesen Untersuchungen entwickelt wurden, wurden verglichen mit den Bruchbereichen, die man mit der Anwendund der Hoek-Brown GSI Formulierung erhaelt. Eine gute Uebereinstimmung zwischen gemessenen und errechneten GSI Festigkeitsbereichen wurde erzielt, wenn der Abstand der Risse in der Berechnung der GSI in Betracht gezogen wurde.

Jan 1, 2003

By J. A. Beukes, M. Marais

TICOR South Africa is a new titanium feed stock producer. In the Ticor South Africa plant the ilmenite feed to the smelter plant is roasted to enhance its magnetic properties. This allows for the magnetic separation of chromite from the ilmenite. The magnetization reaction relies on partial oxidation with both under- and over-oxidation causing insufficient magnetization. To subject the roaster plant feed material to the required physical conditions a circulating fluid bed (CFB) roaster is used. This paper describes the development of a laboratory model that will aid in the control of the CFB roaster.

Jan 1, 2003

By R. Peroni, J. Kopp

Mine planning and scheduling is based on using a geological model for the deposit. Blocks are used to discretize the deposit into mineable volumes where grade values are assigned. Traditional estimation techniques such as kriging or inverse distance weighting are frequently used for this task where an interpolated value is calculated within a discrete volume. This group of block grades is the input for sequence optimizers, which base their decision on the economical value of a given block. Ultimately, the economical value of a block depends on its grade, making mine sequencing sensitive to all estimated values. If one looks to a block not as a single grade but as a set of equally possible grades, its economical value will change as different grades can be assigned to it. Stochastic simulation is known to provide the tools to assess grade variability, which makes it possible to generate equally probable values in a block. Different grade block models can thus be built and multiple sequencing alternatives are observed by running the optimizer for these distinct inputs. The results demonstrate that the methodology is adequate for risk assessment and proves to be useful for mining project sensitivity analyses. Differences in the project net present value showed that there is little difference between the two simulation methodologies (sequential Gaussian simulation and sequential indicator simulation) applied. The process is demonstrated using a Brazilian kaolin deposit. Keywords: geostatistical simulation, mine planning, sequencing, risk assessment, open pit optimization.

Jan 1, 2003

By K. Aoki, Y. Mito, S. Shirasagi

The authors developed the TBM Excavation Control System (the TBM Navigator), in order to realize the advanced observational construction. During the excavation using this system, the rock strength value is immediately calculated from the TBM driving data as an index of rock properties, and the drill energy coefficient is also calculated from the drill logging data that is carried out using the probe hole ahead of the tunnel face. In this study, a new, geostatistical simulation-based method is proposed for the automatic prediction of the rock properties ahead of the tunnel face with good precision, using both the drill logging data and the TBM driving data. The applicability of this method is validated through the prediction at the actual tunnel excavation that passes through the faults. Les auteurs ont mis au point un Système de Contrôle de forage avec la machine à pleine section (Navigateur de la machine à pleine section), en vue de réaliser un système de surveillance plus efficace. Avec ce système, la résistance de la roche est immédiatement calculée, au cours du forage, à partir des données de conduite de la machine, comme indice des propriétés de la roche, et le coefficient d'énergie de la foreuse est également calculé à partir des données de log de forage collectées dans un trou de sonde foré dans le front de taille. Dans cette étude, on propose une nouvelle méthode basée sur la simulation géostatistique qui permet de prévoir d’une manière automatique, des propriétés de roches se trouvant derrière le front de taille avec une précision satisfaisante, à l’aide des données de log de forage et celles de conduite de la machine à pleine section. Cette méthode s’est avérée suffisamment précise au cours du forage d’un tunnel réel qui traversait une zone de failles. Die Autoren entwickelten das TBM Ausschachtungssteuerungssystem (den TBM Navigator), um noch besser überwachte Bauarbeiten zu ermöglichen. Unter Einsatz dieses Systems wird die Gesteinsfestigkeit während der Ausschachtungsarbeiten unmittelbar aus den TBM Antriebsdaten als ein Index für die Gesteinseigenschaften berechnet. Gleichzeitig wird auch der Bohrenergiekoeffizient aus den Bohrlogdaten berechnet, die an Hand der Probebohrung am Stirnende des Tunnels erhalten wurden. In der vorliegenden Studie wurde ein neuartiges, auf geostatistischen Methoden basierendes Verfahren für die automatische und angemessen genaue Vorhersage der Gesteinseigenschaften am Stirnende des Tunnels vorgeschlagen, für das sowohl die Bohrlogdaten als auch die TBM Antriebsdaten verwendet werden. Die Anwendbarkeit dieser Methode wird durch die Vorhersage bei einer tatsächlichen, durch Verwerfungen verlaufenden Tunnelausschachtung bewiesen.

Jan 1, 2003

By F. Ntengwe

The Konkola Mine, a subsidiary of the Konkola Copper Mines Plc (KCM) which is owned by the Vedanta group of companies of India and Zambia Consolidated Copper Mines Holding limited, is located at Chililabombwe in the northern extension of Zambia's Copperbelt province. In its operations, the mine has been experiencing problems in ascertaining the optimum degree of fineness and the operating density of the hydrocyclone overflow in order to achieve high flotation performance. It was believed that recovery of sulphide copper minerals from Konkola ore is a function of the fineness of the grind so that it might be an economical justification to modify the grinding plant in order to run at lower cyclone overflow densities than the case is now. In an effort to improve these operations, it was decided to carry out test work on various hydrocyclones of sizes 0.381 m, 0.4575 m and on 0.508 m. The later was found to give satisfactory results and was installed on the plant. Despite giving satisfactory results there was need to investigate further to establish the working densities and size. Increasing the density of cyclone overflow decreases the per cent passing 75 pm at least in the range 1080-1 150 g/l. Furthermore, hydrocyclones give better separation at low densities of feed and hence the efficiency is high at low feed densities. Circulating load increases with an increase in feed densities and an decrease in the grind. The flotation performance in both sulphide and oxide copper minerals rougher stages is enhanced with an increase in the degree of fineness of the grind, with an optimum being obtained at a density of 1 150 g/l and 81.4% passing 75 µm. Keywords Konkola mine, hydrocylone, optimum degree of fineness, sulphide copper minerals.

Jan 1, 2011

By W. Barthel, B. A. Dippenaar, J. Malan

In its most basic form, the process of sintering is very simple, and has been in use since the turn of the previous century. However, while the basic process is simple, control of the process relies on a number of extremely complex interdependent process parameters and requires a thorough understanding of the effect of these parameters on production capacity and product quality. Further, as with many other processes, the process parameters and hence design details of visually similar installations are highly dependant on the specific feed materials. While the industry trend has been towards an increase of capacity in order to lower unit production cost, typically in Iron ore sintering plants, this approach is not always possible for other commodities because of the scale of operation. This paper seeks firstly to describe some design considerations of sinter plants; secondly, to report on results from testwork performed with a specific series Manganese ore blends; and last, to relate these results to the design of new small-scale Manganese ore sinter plants.

Jan 1, 2004

By A. Aitio

Sustainable development is one of the central themes of the work of the World Health Organization; chemical safety is one of its important components. For more than 25 years, WHO has had specialized units for assisting member countries in dealing with their problems in chemical safety. For one of the units involved, International Programme on Chemical Safety, a reorientation is in progress to make best use of existing resources, and to prioritise the work to optimally correspond to the needs of the member countries. The risk assessment work of IPCS, and specifically, the work on chromium and chromium compounds, are discussed.

Jan 1, 2004

By Deon van Tonder, Bert Van Hege

Comparison of various technologies for uranium recovery from sulphuric acid leach solutions shows that Resin-in-Pulp (RIP) and/or Solvent extraction (SX) based processing routes are usually cost effective (11). A combined RIP-SX recovery-purification route and a CCD-SX recovery-purification route were investigated and optimised. The design basis used for the investigation was a production rate of 200 kg/h U3O8 over a solution concentration range of 40 to 1500 mg/L U3O8. The OPEX for the RIP-SX processing route was found to be sensitive to the variation in uranium concentration in the leach liquor. One of the main drivers for this trend is the leach acid concentration. Conversely, the CAPEX of the CCD-SX processing route was sensitive to the uranium concentration in the leach liquor. The leach acid concentration only affected the OPEX of the CCD-SX processing route modestly, as the bulk of the acid is recovered in a pre-leach circuit. Contrary to expectation, the effect of extractant loss assumptions on the overall processing route economics was found to be modest to insignificant. It should be noted that the CCD-SX processing route OPEX was more sensitive to extractant loss assumptions than the RIP-SX processing route OPEX. Economic optimum wash ratios were determined for the CCD-SX processing route and increased with leach concentration ? the increase in wash ratio was less than proportional. A 5-stage CCD configuration was found optimal over the concentration range investigated.

Jan 1, 2007

By J. L. van Niekerk, J. Gunaselvam

This study investigates the use of appropriate seating systems for the control of whole-body vibration exposure in vehicles used in the SA mining industry. Six suspension seats were tested with six test subjects to determine the most suitable seat for an articulated dump truck based on the EM1 requirement in ISO 7096 (2000) standards. Transmissibility functions were measured in the laboratory using the newly commissioned Dynamic Seat Testing Facility with two excitation levels of 1m/s2 and 2 m/s2 r.m.s. in the 0.5 - 30 Hz frequency range. SEAT values were calculated for two input spectrums, the EM1 input spectrum specified as in ISO 7096:2000 and measured road vibration data measured on a typical articulated dump truck. The averaged SEAT value calculations indicated that not one of the seats will qualify as an ISO 7096 (2000) suspension seat but that it is possible to select a seat that will significantly reduce the vibration the driver will be exposed to.

Jan 1, 2003

By S. Erçayhan, B. Derin, O. Yücel

In the present study, the production of low carbon ferrochromium (LC-FeCr) from chromite concentrates containing 55.09% Cr2O3 and 13.06% Fe via metallothermic process was investigated. For this aim, in the experiments, the aluminothermic reduction method was applied in an open crucible. 10% CrO3 + 10% NaClO3, 15% CrO3 + 5% NaClO3 and 20% CrO3 by weight of concentrate were added to the charge, respectively and the charge was reduced with aluminium. The experiments were done with the additions of 90, 100, 110, 120 and 130% of stoichiometric requirement of aluminium. The highest Cr content in alloys was found as 71.7% at 120% of stoichiometric Al whereas the highest Cr recovery in alloys was found as 71.8% at 130% of stoichiometric Al when the both charge contained 15% CrO3 + 5% NaClO3 by weight of chromite concentrate.

Jan 1, 2004

By R. Zivojinovic, S. Vujic

The structural age of the capital mining machinery, representing a part of the system of the Electric Power Industry of Serbia, has been dictated by the initiation and development of open pit coal mines. For example, the oldest bucket wheel excavators were installed some thirty-four years ago, and the average life of the relevant machinery exceeds twenty-two years. Operation of both capital equipment and machinery has direct effects on economic and business activities of open pit mines, and consequently forced us to make a decision and study thoroughly the problem of establishing the optimum exploitation life of capital mining equipment at the open pit coal mines of the Electric Power Industry of Serbia. The aim of this paper is to define and discuss the relative problems as well as to find out the possible solutions and establish the methodology for estimating the optimum exploitation life of machinery. The study was successfully carried out by a team of scientists engaged from and coordinated by the Department of Computer Science of the Faculty of Mining and Geology, University of Belgrade. This paper presents the key observations covering the subject problem. Keywords: Mining, Opencast exploitation, Coal, Optimization, Exploitation life, Capital machinery, Electric power industry, Dynamic programming.

Jan 1, 2003

By I T. Tshabalala

In typical conventional narrow vein stoping operations, the use of temporary support components to offer some support to workers, whilst the permanent and generally more elaborate support system gets installed or constructed, still results in injuries to people. The authors wishes to explore the probability and practicality of making use of new generation support products to make the support operations safer as well as enhance productivity in the stope face. This paper will examine the use of Autorock Drills as a means to drill roof support holes and install appropriate support components into these holes, as well as the application of ?Thin Spray Liners?, commonly called TSL?s as an additional means of creating a safer operating environment. The installation of netting as a means of roof protection and other support aspects such as cemented roof-bolts will also be explored. These proposed items are envisaged to improve the safety of our people and reduce production down time and increase production and productivity.

Jan 1, 2008

By D. Boldini, R. Lackner, H. A. Mang

ABSTRACT: In this paper, the strong interaction between the hardening shotcrete lining and the surrounding ground in NATM tunneling is investigated by means of axisymmetric analyses, accounting for the three-dimensional nature of the excavation process. The effect of the hydration of shotcrete on strength, stiffness, chemical shrinkage as well as microcracking and creep are accounted for. For the description of the mechanical behavior of the ground, a multi-surface plasticity model is employed. The performed analyses of the excavation process provide insight into the influence of each phenomenon accounted for in the material model for shotcrete on the response of the ground-shotcrete compound structure. ZUSAMMENFASSUNG: In diesem Beitrag soll die Interaktion zwischen dem erhärtenden Spritzbeton und dem Boden auf der Basis axisymmetrischer Berechnungen untersucht werden. Derartige Berechnungen ermöglichen die Berücksichtigung des drei-dimensionalen Charakters des Vortriebprozesses. Die Auswirkung der Hydratation auf die Entwicklung der Festigkeit, Steifigkeit und der chemischen Schwindverzerrungen, sowie das Reißen und das Kriechen des Spritzbetons wurde berücksichtigt. Das mechanische Verhalten des Bodens wurde mittels eines Mehrflächenplastizitätsmodells simuliert. Die durchgeführten Berechnungen des Vortriebprozesses geben Einblicke in die Auswirkungen der Spritzbetoneigenschaften auf das Tragverhalten des Boden-Spritzbeton-Komposits. RÉSUMÉ: La stricte interaction entre le soutènement en béton projeté durcissant et le terrain dans un tunnel creusé avec la NATM est étudiée par des analyses axisymétriques, compte tenu de la nature tridimensionnelle des processus de creusement. Les effets de l’hydratation du béton sur la résistance, la rigidité et la contraction chimique, ainsi que sur la micro-fissuration et le fluage, sont mis en compte. Pour la description du comportement mécanique du terrain on emploie un modèle de plasticité multi-surface. Les analyses conduites mettent en évidence l’influence de chaque phénomène considéré dans le modèle constitutif du béton projeté sur la réponse de la structure composite terrain-béton projeté.

Jan 1, 2003

By W. Kint

More than 10 years ago, one of MECS?s current partners KVT developed the so called SULFOX process for cleaning waste gases containing sulfuric compounds. In this Wet Acid Process (WAP) compounds such as SO2 and H2S, CS2, COS are oxidized over catalyst bed(s) to SO3 and finally sulfuric acid is formed. The individual plants are designed according the feed gas concentrations and customers requirements to keep the investment and operating costs as low as possible. MECS strongly believes the technology we propose will meet all your expectations. Thanks to our vast experience in the construction of sulfuric acid plants (MECS built over 800 sulfuric acid plants worldwide) we were able to design you a very reliable installation. MECS is offering the metallurgical industry, besides our conventional acid plant technology (for strong SO2) and our DynaWave? scrubbing technology (for very low SO2), a SULFOX wet acid plant (for the mid range SO2 concentrations) including an optional upstream DynaWave gas cleaning plant if required. See the figure below. Besides providing advanced technology, MECS is the only company who designs and manufactures its own key critical equipment. We manufacture our own catalyst, mist eliminators, acid distributors and coolers. Because of our in-depth technology knowledge, we understand the critical aspects necessary for making optimum equipment designs. With this combined supply of technology and key critical equipment, we can make a single overall guarantee second to none other in the world.

Jan 1, 2009

By F. Crundwell, A. J. Lathwood

A number of base-metal operations would like to increase production to take advantage of the higher metals prices. In general, this higher production should not be achieved with major operating changes. In hydrometallurgical facilities, leaching and pressure leaching represents one area where upfront limitations may be a bottleneck to the capacity of the entire plant. An assessment of the capacity of the leaching tanks and autoclaves was performed using a predictive model within the AweSym flowsheet simulator. The model is described, and the results of the application of the model to a number of different leaching reactors are presented. It is argued that the leaching number, which relates the residence time, particle size and the leaching rate, is of prime importance. Finally it is shown that there are some unexpected catastrophic events in increasing production capacity without a thorough understanding of the leaching operation.

Jan 1, 2007

The Gordonsville Operation of Pasminco US Inc. along with the Center for Advanced Mineral and Metallurgical Processing (CAMP) at Montana Tech studied, developed and implemented a pilot scale hydrometallurgical facility for the industrial recovery of germanium and gallium. This paper describes the joint testing and engineering program that culminated in this successful process. 1. Introduction The Pasminco US Inc. (PAS), Gordonsville Operation, has been producing zinc concentrate continuously since 1975. Within the zinc concentrate, several byproduct elements were found to be significantly concentrated including gallium and germanium. The gallium and germanium replace zinc and other metals within the crystal lattice structure of the zinc mineral (sphalerite) and are concentrated in the same manner as the zinc mineral. This concentrate is then sent to the Pasminco Clarksville Zinc Refinery for further processing. Within the hydrometallurgical zinc-processing plant at Clarksville, a residue is formed that contains a majority of the impurities that would otherwise contaminate or hinder the zinc process. Approximately 5,000 tons of residue is formed annually containing approximately 0.80% gallium and 0.60% germanium along with significant quantities of iron, zinc, silica, and lead. Pasminco currently sells this residue for the germanium value. Until recently, no revenue for the gallium was obtained from the sale of the residue.

Jan 1, 2008