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COALTECH 2020 initiated a research project to provide the coal mining industry with a modelling tool to determine the expected types of subsidence, risks and the investment required in post-closure funds to cater for subsidence associated with bord and pillar mines. A detailed literature review was conducted to determine the most important parameters in calculating the cost associated with surface subsidence. A subsidence prediction model was developed to determine the likelihood of different types of subsidence. The study made use of current knowledge of failure mechanisms and its aim is to assist the industry and government in arriving at the most suitable arrangements when authorities require financial instruments to assure compliance with environmental regulations.

Jan 1, 2003

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 S. T. Johansen, B. T. Løvfall, T. Rodriguez Duran

In this paper we develop a physics-based model for lining erosion in steel ladles. The model predicts the temperature evolution in the liquid slag, steel, refractory bricks, and outer steel shell of the ladle. The flow of slag and steel is due to forced convection induced by inert gas injection, vacuum treatment (extreme bubble expansion), natural convection, and waves caused by the gas stirring. The lining erosion takes place by dissolution of refractory elements into the steel or slag. The mass and heat transfer coefficients inside the ladle during gas stirring are modelled based on wall functions which take the distribution of wall shear velocities as a critical input. The wall shear velocities are obtained from computational fluid dynamics (CFD) simulations for a sample of scenarios, spanning out the operational space, and a model is developed using curve fitting. The model is capable of reproducing both thermal and erosion evolution well. Deviations between model predictions and industrial data are discussed. The model is fast and has been tested successfully in a ‘semi-online’ application. The model source code is available to the public at [https://github.com/SINTEF/refractorywear].

Apr 16, 2024

By Ian MacKenzie

Over the past twelve years, professionals such as architects, engineers, accountants, and attorneys have not had to pay a great deal of attention to GST. The fees charged to clients (outputs) have not been subject to GST, but they have had to pay GST on al purchases of materials and taxable services relating to their activities.

Jan 1, 1990

By N. J. Wagner, D. G. Modiba

There is currently limited knowledge concerning South African coal deposits as hosts for rare earth elements (REE). This project aims to determine the concentration of REE, including yttrium and scandium (REY+Sc) in various coal seams and adjacent sediments in borehole cores from the Ermelo, Witbank, and Waterberg coalfields in South Africa. Coal petrography (maceral count and vitrinite reflectance), XRD, XRF, sequential chemical extraction procedure (SCEP) before ICPMS, and mineral liberation analysis (MLA) were conducted on the coal and associated sediment samples. The coals were inertinite-rich, medium-rank bituminous coal, with moderate to high ash content. The two dominant minerals in all the coalfields are kaolinite and quartz, except for sample ZBS2M, where dolomite was dominant. The dominant major oxides are Al2O3, SiO2, Fe2O3, and CaO, which concur with the XRD results. The ICP-MS results following SCEP indicated that both coal and the associated sediments were light REY+Sc dominant. There was also an elevation of medium REY+Sc in the Witbank coal’s associated sediment samples. Notably, the samples with the highest REY+Sc results were the sediment samples. The Waterberg samples had the lowest REY+Sc from both the coal (less than 2 μg/g to 7 μg/g) and associated sediments (2 μg/g to 15 μg/g). While the highest REY+Sc was yielded from the Witbank-associated sediments (500 μg/g to 2,500 μg/g). The carbonate fraction step proved to be the most successful leaching step, as most REY+Sc was recovered in that step for all coalfields. In addition to the carbonate fraction, the silicates and sulfide fraction in the Witbank samples, and the ion-exchangeable fraction for the Waterbergassociated sediments samples proved successful in leaching out the REY+Sc. MLA determined that monazite and xenotime in all the coal samples were the REY+Sc-bearing minerals.

Nov 6, 2024

By T. Tamura

It is known that the CaO-FetO-P2O5slag system has a wide liquid miscibility gap at steelmaking temperatures and this two-liquid slag phase has many advantages such as high activities of both FetO and CaO and high amount of P2O5. The phosphorus distribution ratio between the two-liquid slag and molten steel was confirmed to be higher than that between CaOsat.-FetO-P2O5slag and molten steel. The two-liquid slag may be useful for dephosphorization of molten steel and reduction of slag volume. Furthermore, the phase equilibrium of two-liquid CaO-FetO-P2O5slagsaturated with MgO was measured to determine the applicability of the two-liquid slag to dephosphorization in steelmaking process. Keywords: slag, refractories, solid solution, two-liquid phase, dephosphorization, steelmaking, phase equilibrium.

Jan 1, 2004

By S. Subramanian, L. Mweene

A siliceous low-grade copper ore from Mpanda Mineral Field (MMF), located in south west Tanzania consisting of SiO2 (58.3%), Fe (10.4 %) and Cu (0.9 %) was initially subjected to selective dispersion-flocculation using sodium trisilicate (STS) as a dispersant and xanthan gum (XG) as a flocculant. Subsequently, the selectively flocculated fraction was floated using a collector combination of potassium ethyl and amyl xanthate (1:1) in the presence of poly-ethylene oxide (PEO) as a silica depressant, to get a copper concentrate. The mineralogical investigations confirmed that the MMF ore was mainly composed of quartz, chalcopyrite and pyrite. Adsorption studies indicated that the adsorption density of XG on MMF ore decreased with an increase in pH, while that of PEO was independent of pH. The adsorption isotherms of XG and PEO on MMF ore exhibited Langmuirian behaviour. The zeta potential studies of MMF ore indicated that the iso-electric point (IEP) was located at pH 2.6, presumably due to its high silica content. In the combined presence of XG and STS, the zeta potential of MMF ore became more negative, with an increase in the concentration of STS. However, in the presence of PEO, the zeta potential of MMF ore became less negative with an increase in the concentration of PEO beyond the IEP, without shifting the IEP. Selective dispersion-flocculation of MMF ore improved the flocculated chalcopyrite grade to 19.8 %, yielding a degree of flocculation and a maximum separation efficiency of 12.1 % and 85.7 % respectively, after three desliming stages in the presence of 30 ppm of STS and 30 ppm of XG. A copper concentrate of 29 % grade and 90 % recovery containing silica of 0.9 % grade and 1.7 % recovery was achieved by flotation of the selectively flocculated component, using PEO as a depressant for quartz. Keywords: Flotation kinetics, flotation machines, flotation bubbles, particle size

Jan 1, 2020

By M. Hermanus

1. INTRODUCTION It gives me great pleasure to extend my warmest greetings to everyone attending the 30th International Conference of Safety in Mines Research Institutes. I would also like to bid a special welcome to all of the international delegates who have travelled to Johannesburg to take part in what surely be a most rewarding session of deliberations. As you come together over next four days, you will have a wonderful opportunity to exchange ideas and information on strategies and practices for the implementation of sustainable patterns of development. The objectives of this meeting are both timely and far-reaching, as countries around the globe work towards the sustainable use of the world resources. Each of you brings a high level of expertise to these deliberations. I know that you will make the most of this opportunity to address the challenges and opportunities to highlight the most innovative and technologically efficient methods of social protection in order to ensure an increase in the quality of life, health, safety and living environment for the peoples of the Africa. Our country, although endowed with an immense and diverse array of mineral deposits, is perhaps best known in the mining industry for the fact that it is the world’s biggest producer of gold. Although South African gold production has declined over the past years and the industry faces serious problems, it is a myth that the South African industry is moribund. There is a new energy coursing through the South African producers which will ensure their powerful presence for many years to come, based not only on their domestic production but also and probably increasingly on their external operations. Africa features prominently in the latter category.

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 S. Chatterjee, F. Suparno, A. Paithankar

Estimating reserves and quantifying resources stand as pivotal and intricate endeavours within the realm of coal mining operations. Intricate geological formations compound the challenges in resource estimation, thereby complicating reserve calculations. The uncertainties tied to geological attributes of coal, encompassing parameters like tonnage and coal quality, wield significant sway over resource and reserve computations within coal mines. This research delves into the domain of geological uncertainties, with a specific focus on calorific value, aiming to numerically characterise resources and reserves within an open-pit coal mine situated in Indonesia. To quantify resources, the coal seam geometry underwent simulation via a multipoint geostatistical technique known as single normal equation simulation. A geologically established coal seam served as the training image for generating 20 equiprobable coal models. To simulate CV, 50 realisations were generated for each simulated coal seam, utilising sequential Gaussian simulation. Deviations of the simulated coal seams ranged from -0.07% to 5.48% in comparison to the training image. The CV simulation yielded an average value of 5,920.29 kcal/kg, accompanied by a standard deviation of 586.54 kcal/kg. However, the average CV spanned from 5,305.26 kcal/kg to 6,526.55 kcal/kg across diverse simulations. For reserve calculation within the context of geological uncertainties, an algorithm rooted in maximum flow graph theory was employed to construct the ultimate pit for the coal mine. Within this final pit, the average stripping ratio was 1.62, coupled with a CV value of 6,019.66 kcal/kg. When juxtaposed with the deterministic model, the findings underscore that the stochastic ultimate pit delineates a more expansive excavation, accompanied by a heightened undiscounted cash flow.

Oct 2, 2025

By A. F. Lee

A pick-up apparatus capable of yielding quantitative results has been described. Studies of some collector-mineral systems have been presented to illustrate the versatility of the apparatus and prove the validity of results.

By M. Grozdanovic, D. Marjanovic, M. Ilic

We present a framework for solving the problem of functional compatibility between process control equipment in control centres at underground mines and operator capabilities. The equipment incorporates displays of current ventilation, gas, and fire hazard data, status of alarm and early warning systems, a voice communication subsystem, and facilities for recording and printing ofdata and reports. The layout of the existing control panel is compared with a recommended design. The basic principles of ergonomic design and arrangement of the controls and indicators, as well as ease of use, type of operations carried out with these controls, and operators’ viewing angles are discussed. The objective is to improve the usability of control panels, display boards, and graphic screens so as to enhance the functioning of control centres and optimize control of technological processes in coal mines.

Jun 10, 2024

By M. Suzuki, T. Shiomi, M. Nakada, K. Tsutsumi

Mold powder plays an important role in the continuous casting process for high quality steel production. It is well known that mold powder entrapment causes surface defects in steel sheet and the high viscosity of mold powder prevents the entrapment of mold powder in molten steel in ultra low carbon steel. This paper deals with the entrapment of mold powder caused by suction by Karman?s vortex in a laboratory experiment. At first the effect of the viscosity of oil and interfacial tension between water and oil was investigated in a water model experiment. Then hot model experiments were carried out by mold powder and molten steel. The amount of mold powder entrapment was affected by the viscosity and the interfacial tension between molten steel and mold powder. As a result, the following equation of the mold powder entrapment was obtained. m=1.06*107?-0.255?m-s-2.18 The amount of mold powder entrapment decreased when the viscosity and interfacial tension increased. But the effect of viscosity was larger than that of interfacial tension in the case of the industrial mold powder when the viscosity was under 0.5 Pa.s, interfacial tension was from 1200to 1300 mN/m.

Jan 1, 2004

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

This publication is provided on an "as is" basis without warranties of any kind, either expressed or implied including, but not limited to warranties of title or implied warranties of merchantability of fitness for a particular purpose. The information contained in this publication is for general information purposes only. It does not constitute professional, technical, financial or other advice to the user of this publication and must not be relied upon as such by any person whatsoever. The use of this publication is at the users own risk. The authors/creators of the information contained in this publication have tried to ensure that the information contained herein is correct, but errors or inaccuracies may exist or the information may be incomplete, unreliable or no longer up to date. Therefore, no warranties of any nature whatsoever are given and any liability to any person in respect of anything and in respect of the consequences of anything done or omitted to be done, wholly or partly in reliance upon the whole or any part hereof, are disclaimed, including and without limitation any contractual, dialectal, direct, consequential or financial damages or losses. On no account will Organisers and/or any of the contributors or any person or entity involved in creating, producing or distributing the information and or software available in this publication be liable for any such damages arising out of the use of or inability to use this publication. Copyright Reserved The South African Institute of Mining and Metallurgy P O Box 61127, Marshalltown 2107, South Africa www.saimm.co.za All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical photocopying, recording or otherwise without the written permission of the copyright owner. Although the greatest care has been taken in the compilation of the entire contents, the editors and publishers do not accept responsibility for errors or omissions. First Edition Copyright February 2004 Proceedings ISBN: 0-9584663-5-1 (1 volume and CD-ROM)

Jan 1, 2004

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 Helge Rosenberg

Up to now, Topsøe WSA (Wet gas Sulphuric Acid) plants have been in operation for almost 30 years, and close to 80 plants have been sold. In spite of its unique features and ability to treat gases without any prior drying, the WSA technology has had certain restrictions with regards to SO2 concentration in the feed gas, and the overall conversion of SO2 by catalytic means has been limited to approx. 99.7%. In commercial scale sulphuric acid production on the basis of elemental sulphur and metallurgical off-gases, there is a demand for higher SO2 conversion and treatment of gases with a higher content of SO2. Therefore Topsoe has further developed its WSA technology to cope with these demands. This paper will explain more about the principles of such new development and leave the delegate with a better understanding of the potentials of the new generation of the WSA technology from Topsoe.

Jan 1, 2009

By Helge Rosenberg

Up to now, Topsøe WSA (Wet gas Sulphuric Acid) plants have been in operation for almost 30 years, and close to 80 plants have been sold. In spite of its unique features and ability to treat gases without any prior drying, the WSA technology has had certain restrictions with regards to SO2 concentration in the feed gas, and the overall conversion of SO2 by catalytic means has been limited to approx. 99.7%. In commercial scale sulphuric acid production on the basis of elemental sulphur and metallurgical off-gases, there is a demand for higher SO2 conversion and treatment of gases with a higher content of SO2. Therefore Topsoe has further developed its WSA technology to cope with these demands. This paper will explain more about the principles of such new development and leave the delegate with a better understanding of the potentials of the new generation of the WSA technology from Topsoe.

Jan 1, 2009

By V. Labiouse, P. K. Kaiser, F. Descoeudres, F. Rojat

In this paper some failure phenomena observed in the crossing of brittle rock formations at the Lötschberg base tunnel are presented. A brittle failure criteria, recently developed by Canadian researchers, is applied through finite element calculations together with a semi-empirical failure criterion, to explain these behaviours. Good agreement is found between predicted and observed failures at the tunnel walls. This study also shows some of the limitations of this approach. Dans cet article sont présentés certains phénomènes de rupture observés durant la traversée de zones de roches fragiles lors de l’excavation du tunnel du Lötschberg. Un critère de rupture développé récemment par la recherche canadienne est utilisé à travers des calculs par éléments finis. En parallèle, les résultats sont comparés avec ceux d’un critère semi-empirique. Au niveau des parements, l’ampleur des ruptures observées est assez proche des résultats de calcul. Cette étude a également permis de mettre en avant certaines limites de l’approche choisie. In diesem Artikel werden verschiedene Brucharten dargestellt, die bei der Durchfahrung von sprödem Gestein im Rahmen des Ausbaus des Lötschberg-Basistunnels beobachtet wurden. Zur Erklärung des vorliegenden Verhaltens wurden die erst kürzlich in Kanada entwickelten Theorien zur Beschreibung von Sprödbrüchen herangezogen und bei der Berechnung mittels der Finite-Elemente-Methode und eines semi-empirischen Kriteriums angewendet. Die so vorhergesagten Versagenszonen an den Tunnelwänden stimmen mit den Beobachtungen gut überein. Die Studie hat auch dazu beigetragen, die bei der Anwendung des Lösungsansatzes angetroffenen Schwierigkeiten aufzuzeigen.

Jan 1, 2003

By V. Sheikhzadeh, S. M. H. Haddad, M. Saghaeian, N. Esmaeili, R. Hejazi

One of the most significant features of iron ore concentrate (pelletising feed) is the specific surface area (SSA) that affects the achievement of desirable pellet properties. There are various methods to determine this parameters and currently, the most common is the Blaine air permeability method. However, due to the simplified assumptions including spherical and identical particles and 50% bed porosity, the Blain test does not provide accurate results. In fact, these two suppositions are far from reality. In this research, comparison of SSA measurement ways are investigated, containing laser diffraction testing and Blaine air permeability, on samples with different SSA, obtained from Ball mill and high pressure grinding rolls (HPGR). The output data showed that the calculated amounts of SSA by means of laser analysis were far greater than any other one. Furthermore, in the same results of Blaine air permeability tests on samples comminuted by different grinding methods, it was observed that the SSA figures from the laser diffraction method for HPGR products were almost 800 units greater than Ball mill ones. Keywords: Pelletising feed, specific surface area, Blaine air permeability, laser diffraction testing

Jan 1, 2020