Search Documents

By P. K. Hofmeyr

Base Metal (Cu, Ni, Mo, Zn, Co etc.) analysis traditionally has been very slow in conventional analytical laboratories which can lead to additional costs being incurred in waiting time of drill rigs or mining excessively off-reef. Recent developments in the automation of analytical laboratories now allow for very rapid turn-around times for base metal analytical data which can help reduce such costs as well as reduce the unit costs of the analyses themselves. 2.0 CONVENTIONAL ANALYTICAL LABORATORY PRACTICE Conventional analytical laboratories are necessarily are very manual. Sample preparation is slow and laborious, samples are moved from stage to stage manually and, typically, all samples are processed in batches so a sample which is the first to be, say, milled has to wait for the complete milling of the batch before it advances to the next stage eg. mixed with wax prior to pelletising for XRF analysis. Inevitably this results in long sample data turn-around times for laboratories handling large numbers of samples. Manual sample preparation can only be accelerated by increasing staff which increases costs and can lead to additional errors being introduced. Cleaning of sample preparation equipment, eg. crushers and mills, between samples is essential to avoid cross-contamination between samples and this is slow and labour-intensive. In manual sample preparation the correct sample numbers staying with the samples is totally dependent on the efficiency of laboratory operators. It is extremely difficult to detect when errors have occurred due to the switching of sample numbers during the sample preparation stages. Running duplicates and QC samples at best is only partially successful in detecting when sample number switching errors have occurred. Errors of this nature and cross-contamination problems due to incomplete cleaning of sample preparation equipment tend to occur when laboratories are working at pressure due to high sample numbers and when supervisors are not present during 24/7 laboratory operations which is often required on plant process control laboratories. These problems are common to all conventional analytical laboratories and their magnitude is dependent on the level of control and efficiency of QC systems practised by individual laboratories. The disadvantages of conventional manual analytical laboratories can be summarized as follows:- 1. Labour-intensive which is costly especially when multiple shifts have to be used during 24/7 operations.

Jan 1, 2005

By R. Falcon, P. den Hoed, A. Luckos, R. Erasmus, V. du Cann, D. Comins

Carbon as a reductant, additive or filler is an essential element in the processing of metallic ores and the manufacture of iron and steel in the metallurgical industry. In most cases, the element carbon is derived from coal and its carbon derivatives. The properties of carbon required for the different processes in each metallurgical sector vary significantly and, for this reason, matching the correct carbon product for each specific process has become an important if not vital function in all sectors of this industry. This selection process, however, has become increasingly difficult. In many cases, the substitution of new products, despite being similar in all relevant chemical specification characteristics to previous products, has resulted in different performance properties relative to that expected. Under these circumstances, the prediction of performance of unknown carbon products has become fraught with difficulties unprecedented in the past. In order to initiate an investigation into addressing these issues, a test case was selected for indepth study the results of which are reported in this paper. The case concerned the use of a specific carbon feed in a conventional submerged arc furnace which gave rise to an unprecedented amount of unreacted or only partially consumed residue trapped in the frozen slag on the refractory walls of the furnace. During the course of these investigations, different advanced analytical technologies were employed including, inter alia, Raman spectroscopy, surface dimensional tests, organic petrology and various thermal reactivity factors. All results have been integrated into a multidisciplinary assessment presented in summary in this paper. Based on the above, and previous experience, the concept of an all-embracing 3-D coal-carbon ?framework? is briefly introduced. This approach has succeeded in obtaining greater depth of knowledge and a better understanding of the issues at stake with specific reference to the organic composition, structure, texture, internal surface area and consequent reactivity of the carbon materials concerned. In consequence, it would now appear that various properties of relevance to the metallurgical industry may be predicted with greater precision than has hitherto fore been possible.

Jan 1, 2004

By A. Kapito

The formation of bainite in steel is dependent on the size of the casting, the heat treatment, and the alloying elements. It is difficult to obtain a fully bainitic microstructure in steels during heat treatment because of its close proximity to the martensite (a?) reaction. The ferrite (a) and pearlite reactions in steels are also rapid and shield the bainite reaction. Alloying elements therefore need to be added to separate the bainite reaction. Boron (B) and molybdenum (Mo) are key elements added to bainitic steels because of their ability to retard the a reaction. Other elements used in the production of bainitic steels are silicon (Si), chromium (Cr), manganese (Mn), and titanium (Ti). In this paper we investigate the effect of alloying elements on the bainite reaction through the use of dilatometry. Dilatometry is a technique that determines phase transformations in the steel and through which continuous cooling transformation (CCT) curves can then be developed. Some initial results are presented of an ongoing study on the development of bainitic steels for railway wheel applications.

Jan 1, 2013

By Gaspard Devos

1. A NEW CONTEXT FOR METAL INDUSTRY Producers and owners of industrial extractive sites are living hard times due to Environmental pressure and liabilities. This is valid whatever the region in the world, it is just a question of time. On one hand, the normative environmental pressure is increasing through more severe regulations and controls on all pollution sources and production materials. [ ] Furthermore, more impurities are extracted and captured, more the volume of the related wastes is increasing. But disposal costs are increasing, disposal areas for wastes are restricted, markets for wastes are limited and technologies for waste treatment are, most of the time, not available. On the other hand, for most of the extractive industries, the costs required to get access to refine primary raw material are killing the profitability of the industry. Definitively, a technological and economical breakthrough is ongoing: extractive industries have to increase their feed from secondary material and to be involved more and more with the recycling business.

Jan 1, 2005

This paper presents an initial investigation into the viability of co-kriging the grades of multiple mining cuts in a two dimensional, thin reef scenario. Deposits with gradational mineralized zones, in the perpendicular sense, are not as well served by the use of reef accumulation and thickness as deposits characterized by a sharp distinction between ore and waste rock. South African Bushveld Complex platinum deposits and Witwatersrand gold deposits are examples of this distinction. The calculation of an optimal mining cut is of paramount importance in the mining of Bushveld platinum. Two-dimensional kriging of a constant stoping width mining cut is an effective method for resource calculations once a cut is decided, but this begs the question of how to decide on the cut. Comparison of multiple cuts is used as a way of achieving this decision on many of Anglo Platinum’s operations. Although the kriging of each cut is valid in isolation, occasional negative values occur when incremental grades between overlapping cuts are calculated. Negative incremental grades cannot reflect reality. They are thought to be related to the inability of the method to include the strong continuity in the perpendicular direction demonstrated by the relevant variograms. Co-kriging of related variables has been investigated as a potential means tore impose this inherent order relationship. Various co-kriging options have been investigated. The method has been tested on a real data set from an established platinum operation. One of three types of anomaly has been investigated so far. The results show that co-kriging the mining cut grade as the primary variable, with just one secondary variable, the reef thickness, eliminates most occurrences. Severe anomalies remaining are arguably indicative of population mixing and might be more effectively treated by rezoning the data. Aim—To investigate the viability of co-kriging the grades of multiple mining cuts as a method for resolving anomalies in the estimation of such cuts on Bushveld platinum deposits, with applicability to other thin reef type deposits with a gradational not sharp cut-off between ore and waste in the direction perpendicular to the reef. Keywords: co-kriging, cross variograms, ordinary kriging, platinum, two-dimensional, grade profile

Jan 1, 2003

By J. M. Galera, M. D. Rodriguez, V. Pozo, S. Cooper

"Cobre Las Cruces mine extracts copper minerals from a VMS deposit located in the well-known Iberian Pyrite Belt (IPB). As an open pit, it is distinguished geologically from other IPB mines by the presence of around 150 m of Tertiary soft marls, known locally as the Guadalquivir Blue Marls, followed by a regionally important aquifer. Below the marls and aquifer the mineralization is hosted by rocks typical of the Palaeozoic within the IPB, comprising gossan, tuffs, slates, and sulphides.This combination of a substantially soft rock and more competent, older (but still occasionally problematic) Palaeozoic lithologies constitutes a unique geological framework and presents substantial challenges in maintenance of slope stability, and therefore operational safety, at the mine site. This paper describes the fundamental design, excavation, and monitoring measures implemented at the mine to maintain safe production, and the lessons learnt during the mine development. IntroductionAs a modern Spanish mine, Las Cruces is committed to the use of best available technology and practices with the aim of guaranteeing the production of ore in a safe environment. From a practical perspective, this implies the realization of a high quality pit design, ongoing geotechnical mapping of exposed slopes to ensure conformity with design, and use of leading geotechnical surveillance technology to complement visual observations. The focus of this article is to illustrate how, at a mine site with potentially problematic soil/rock conditions, multiple advanced techniques employed from design stage analysis through to final pit configuration and vigilance, were combined to achieve an overall control of the ground conditions. In Figure 1 the layout of the pit is shown, illustrating development at the beginning of 2015."

Jul 1, 2019

This paper reviews the history of refractory materials, highlights the development of refractory technology over the years, draws attention to the technology behind these materials, and comments on future developments in this field. By walking the path with refractory materials, from their initial uses in BC times, to the composite materials that are used nowadays, and the nanotechnology developments that are currently taking place in this field, the reader will come to agree that refractory materials are indeed very ?cool?! Keywords: refractory materials; bricks; monolithic materials.

Jan 1, 2008

By J. W. Joubert, R. C. W. Webber-Youngman, M. D. Budeba

"SynopsisCost estimation for surface coal mines is a critical practice that affects both profitability and competitiveness. New mines require these costs to be estimated using available information before a project begins. The competitive advantage of a new mine depends on it being both efficient and cost-effective. Low-cost producing mines have a higher chance of survival in a low-price environment than do high-cost producers. The competitiveness and profitability of a coal mine is based on the costs of production and the supply position on the cost curve. There is no single method of cost estimation, and the available methods consider only one or a few variables, leaving out multiple variables that could significantly affect the estimation of mine costs. Mining companies are thus searching extensively for a method that will increase accuracy in the estimation and evaluation of mining projectsThis paper highlights the shortcomings of the available approaches and proposes a data envelopment analysis method to develop a frontier for effective surface coal mines, and the use of a parametric method for modelling the costs and productivity of new mines to ensure effective competitiveness. The models will extend the capability of estimation and the accuracy of estimates using the efficient decision-making units, by considering the optimal mine-specific and external variables affecting costs.IntroductionCoal contributes 25% of the world’s primary energy needs, after fuel oil, which contributes 35%. The world energy demand, estimated over the period 1990 to 2030, is expanding at a cumulative annual growth rate (CAGR) of 1.7% (Schernikau, 2010, p. 14). This emphasizes the need for enhancing the production of existing mines, as well as opening new mines in order to increase the supply of coal."

Jan 1, 2015

By I. Gil, J. -C. Roegiers

Abstract Hydraulic fracturing is a technology that has been utilized for more than 50 years in the oil industry. It was originally used for stimulating hard, brittle formations which typically exhibit low permeabilities and roughly linear elastic behavior. Nonetheless, an increasingly important segment of the industry is currently stimulating very soft and poorly consolidated formations; where the assumptions of ideal elasticity and relatively small fluid leakoff fail to hold (e.g. Gulf of Mexico, West Africa, Alaska, East China). In these rocks, hydraulic fracturing stimulation has been used for several years to control and solve critical production problems such as sanding and formation damage (caused during completion and drilling operations). Although successful1, the application of this method has not been accompanied by robust fracturing modeling techniques. In addition, long term production increases were often not materialized. In other words, engineers have been able, via trial-and-error, to avoid major ‘operational’ problems but with no optimization of such treatments. Thus, most hydraulic fracturing projects carried out in poorly consolidated rocks render unexpected results. A recent worldwide survey on net pressures by the Delft Fracturing Consortium (Papanastasiou, 1997) indicated that net pressures encountered in the field are 50% to 100% higher than the net pressures predicted by conventional fracturing simulators. The difference is yet higher for the case of poorly consolidated formations (Pak, 1997). The theory for the construction of a fully coupled elastoplastic three-dimensional hydrofrac simulator, specifically conceived for unconsolidated rocks, is presented in this paper. This novel model calculates the dimensions and changes in shape of the fracture(s) being created during hydraulic fracturing operations. No assumptions are made regarding either shape or geometry of the crack(s). Three main failure criteria are used simultaneously in this model: tensile and shear stresses, and volumetric strain. Incremental forms of the governing equations of equilibrium and fluid flow are presented. The scheme chosen for solving this problem is the finite elements method, which allows both equations to be solved simultaneously at any instant in time. Résumé La fracturation hydraulique est une technologie qu’a été utilisé pour plus que 50 ans dans l'industrie pétrolière. Elle a été utilisée au début pour stimuler les formations dure et fragile que typiquement ont des perméabilités basses et un comportement élastique à peu près linéaire. Néanmoins, un segment plus important de l'industrie stimule actuellement des formations mal consolidées; où les suppositions d'élasticité idéale et de relativement petite fuite de fluide ne se tiennent pas raison (par exemple le Golfe de Mexique, l'Afrique d'ouest, Alaska, la Chine de l'est). Dans ces roches, la stimulation avec fracturation hydraulique a été utilisée pour plusieurs années pour contrôler et résoudre les problèmes critiques de production comme les dommages de formation et d’ensablement (causé pendant les opérations de l'accomplissement et forage). Bien que prospère, l'application de cette méthode n'a pas été accompagnée de techniques robustes pour le modelage de fractures. En outre, les augmentations à long terme de production n'ont pas été souvent concrétisées. En d'autre termes, les ingénieurs ont pu, via le procès et l’erreur, éviter les majeur problèmes ‘opérationnel’ mais avec aucune optimisation de tels traitements. Ainsi, la plupart des projets de fracturation hydraulique ont été exécuté dans des roches mal consolidées et ont rendu résultat totalement inattendu. Une récente étude mondiale sur les pressions nettes par le Consortium Delft pour Fracturer (Papanastasiou, 1997) a indiqué que les pressions nettes qu’ont été rencontré dans le champ sont environ 50% à 100% plus hautes que les pressions nettes prédites par les simulateurs fracturant conventionnels. La différence est pourtant plus importante pour le cas de formations mal consolidées (Pak, 1997). La théorie de construction d'un simulateur elastoplastic d’hydrofrac à trois dimensions entièrement couplé, en particulier conçu pour les roches non consolidés, est présentée dans ce papier. Ce nouveau modèle calcule les dimensions et les changements dans la forme de(s) fracture(s) étant créé pendant les opérations de fracturation hydraulique. Aucune supposition n’a été faites en ce que concernant la forme ou la géométrie

Jan 1, 2003

By J. Böhlke, B. Friedrich, E. Hecker

The legislation for the disposal of heavy metals contaminated substances is still going to be tightened up in the future. The main criteria for the utilization or deposition of these residues are the content and the water solubility of these metals. Through this, the use of slags from the lead-and zinc-industry in road building may become limited or even not possible at all. From an economic point of view this would lead to Pb/Zn losses and costs for safe dumping. This paper investigates the feeding of the reducing agent via hollow electrode DC smelting and the yield of metal reduction. After carrying out thermodynamic calculations, the process window conditions for electric-arc furnace tests were determined. Doing this, the zinc could be reduced, evaporated and recovered as an oxidic intermediate product flue dust, while the lead was present either in flue dust or in metallic form. The zinc content in the final slag could be reduced by up to 90%. The slag product has undergone an eluation test which allows it to be used as building materials. Keywords: zinc reduction, lead reduction, hollow electrode, slag treatment, electric arc furnace

By A. V. Roschin, N. V. Malkov, V. N. Karnoukhov, V. E. Roschin

Reduction interactions in solid phases are widespread and occur in most complex metallurgical processes. Among these processes, reactions between oxides and carbon have a special importance. The authors conducted experiments for comparison of reduction by different reducing agents of impregnated chromite ores, in which grains of the reducible chromite spinel are isolated from direct contact with the reducing agent by layers of non-ore material. The results of the experiments have revealed that the beginning of reduction is preceded by thermal and impurity order-disorder transformation of the oxide lattice whilst the transformation of the oxide lattice into the metal lattice takes place as a result of removal of oxygen anions from the zone of metal germ nucleation. Since anions are charge carriers, increase of their mobility can be monitored by changes in electrical conductivity of oxides. Respective measurements of electrical resistance of ores of different metals and a number of pure refractory oxides under heating have indicated that the beginning of reduction coincides with the time of drastic (tens of thousands times) increase of conductivity of the oxides. Besides, the temperature of the beginning of carbon-thermal reduction is in line with the Tammann temperature, i.e. the temperature of transition from the predominantly surface diffusion to volume diffusion. Segregation of metals from the oxide lattice occurs as a result of merging of anion vacancies with defect electrons on defects of the oxide lattice. The transformation of the oxide lattice into the metal lattice requires a certain concentration of anion vacancies and inflow of electrons from the reducing agent to the site of metal segregation. Such inflow has no difficulties due to the mixed anion-electron nature of high-temperature conductivity of oxides. Thus, the reduction is not determined by oxygen diffusion, it is determined by oxygen vacancies diffusion whose speed exceeds the speed of oxygen diffusion by orders of magnitude. This determines that the kinetics of reduction considerably exceeds the kinetics of oxidation at similar temperatures since oxidation proceeds by means of mass transfer of oxygen through the layer of the generated oxide.

Jan 1, 2004

By D. C. Panigrahi

Extensive field studies have been carried out to investigate the pillar fire problems in one coal mine in India. A Thermal IR gun and a Thermovision camera have been employed for thermal scanning to assess the state of heating in selected pillars. Special sampling set-ups have been designed to collect gas samples from the holes drilled into the selected pillars and the multigas detector is used to analyse the composition of samples in situ. In order to predict the spontaneous heating in coal pillars, different gas ratios have been calculated and it has been observed that some of the established gas ratios, viz. Graham?s ratio, Young?s ratio etc. have resulted in negative values in samples containing high amounts of methane. The modified gas ratios have been proposed which will be useful for predicting the pillar fires. These ratios may also be used for assessing the condition of fires in sealed-off areas.

Jan 1, 2004

By J. Drzewiecki, J. Kabiesz

Coal mining using longwall methods of mining can lead to intense disturbances of undermined roof strata. The disturbances may extend beyond the extraction area and the resulted rock mass deformations will appear differentiated. In the case of stiff and undermined roof strata, the energy stored in these rock masses may be frequently dissipated in the form of high-energy seismic tremors. Such events can occur if these strata should fail or „free themselves” either from the constrainment of rock environment or from adjacent strata. It has also been found that the amount of the stored energy closely depends on the size and/or slenderness of these strata. Thus, it would be possible to apply specific preventive measures to reduce the energy of mining – induced seismic tremors. The methods are based on artificial disintegration of the structure of energy – storing strata. One of the most efficient methods is a method of directional hydraulic fracturing, which is regarded as an alternative solution from the traditional blasting and hydraulic methods.

Jan 1, 2003

By Y. van der Grijp

The applicability of a stochastic approach to the simulation of gold distribution to assess the uncertainty of the associated mineralization is examined. A practical workflow for similar problems is proposed. Two different techniques are explored in this research: a Direct Sampling multi-point simulation algorithm is used for generating realizations of lithologies hosting the gold mineralization, and sequential Gaussian simulation is applied to generate multiple realizations of gold distributions within the host lithologies. A range of parameters in the Direct Sampling algorithm is investigated to arrive at good reproducibility of the patterns found in the training image. These findings are aimed at assisting in the choice of appropriate parameters when undertaking the simulation step. The resulting realizations are analysed in order to assess the combined uncertainty associated with the lithology and gold mineralization.

Jan 1, 2015

By H. P. Kritzinger, T. C. Kingsle

"Rotary kilns are used for a variety of mineral processing operations. Hatch makes use of a kiln model developed from first principles to evaluate designs for its clients. This tool has been applied to a variety of pyrometallurgical applications, including ferrovanadium, nickel carbonate, nickel laterite, iron ore reduction, and spodumene (lithium) production.This paper illustrates the application of numerical optimization techniques in combination with the kiln model in the interrogation of a generic iron ore reduction process. The fundamental modelling concepts are explained, followed by a description of the optimization approach. The results show how the combination of the two methods, with modern computing power, can generate a large number of viable design and operating candidates."

Jan 1, 2015

By M. du Plessis, D. F. Malan

"The aim of any mine design is to ensure that the excavations remain stable for the period they will be in use. Various pillar systems are used to ensure that underground stopes remain stable and that mining activities do not affect the surface infrastructure through either surface subsidence or seismicity. Intermediate-depth platinum mines make use of in-stope pillars designed to fail while the pillars are being cut at the mining face. The pillar stress exceeds the loading capacity and the pillars crush as a result. The aim of the paper is to provide an overview of in-stope crush pillars. This will include the application, behaviour, function, mechanism, impact, and design of a crush pillar system."

Jan 1, 2015

The paper examines the design issues associated with the integration of mineral processing within underground mining systems. It demonstrates conceptual integrated system design options appropriate to a range of geological scenarios. Particular reference is then given to a case study of stoping in narrow base metal veins. The performance of such integrated systems in terms of productivity, economic and environmental criteria is demonstrated by means of simulation. Particular attention is given to the potential benefits to mine waste management. Processing technologies appear to offer genuine potential benefit, whilst underground mining methods may need to evolve further to facilitate full integration. This paper is based on industry supported research aimed at developing selective and clean underground mining systems.

Jan 1, 2003

By S. Uludag

Spontaneous combustion of coal has been studied by laboratory techniques using an apparatus in a small-scale laboratory testing. Coal?s inherent characteristics can be measured using Differential Thermal Analysis (DTA) and Crossing Point Temperature (CPT) methods. The DTA curve obtained after testing is compared with actual inherent moisture and its effect on spontaneous combustion has been investigated. It has been found that the Wits-Ehac Index increases as the inherent moisture of the sample increases. Therefore it can be deduced that liability to spontaneous combustion increases with increased inherent moisture. In addition, volatiles have a catalytic affect on self heating immediately after the inherent moisture is reduced. This is identified as stage two in the thermogram. The inherent moisture has a cooling effect during the initial stages of testing and is visible in the DTA thermogram. In addition, while an increase in carbon content means an increase in Wits-Ehac Index value, an ash content decreases the likelihood of on spontaneous combustion. Keywords: Spontaneous Combustion, Differential Thermal Analysis, Crossing Point Temperature, Moisture, Coal, Laboratory Testing.

Jan 1, 2007

By C. D. K. Gauert

High-pressure waterjet technology is proposed as an alternative tool for selective underground mining of high-grade ore sections in stratiform orebodies showing a preferred ?bottom? or ?top? enrichment such as the Witwatersrand reefs and the Bushveld Complex platiniferous reefs. This technique, utilizing known mining technology together with more advanced machinery and additives as used in industrial and cleaning applications, may lead to an increased life-of-mine (LOM) for mining operations. A series of experiments was successfully carried out in a laboratory on Witwatersrand quartzite material, indicating acceptable cutting performance. Mining volumes by selectively cutting of reef portions are considered to be comparable to traditional drilling and blasting. Economic advantages of waterjet mining include energy savings due to the lower quantity of gangue rock to be hoisted to surface, as well as savings by a decrease in the usage of blasting materials. Capital expenditure of waterjet cutting, if applied on a broad scale, could be lower in the long term than that of conventional drilling and blasting methods. Mining by the application of high-pressure waterjet technology could become a competitive ?green technology? improving the economics and safety of labour-intensive mining operations. This paper suggests that waterjet cutting at an industrial scale can become a routine hard-rock mining technique in the future. Keywords waterjet cutting, high pressure, mechanized narrow reef mining, abrasive agents, costs, selective mining.

Jan 1, 2013

By I. Ewart, E. Roux

Skorpion Zinc operates a solvent extraction/electrowinning zinc plant producing over 150 000 t/a of special high grade (SHG) zinc (>99.995% Zn). In the current flow sheet copper and cadmium are cemented from the neutral leach solution using zinc powder, to prevent galvanic corrosion of plant equipment and build-up of copper in plant solutions. This process is effective but unfortunately consumes expensive zinc dust and produces a low value copper product. The EMEW® (Electrometals electrowinning) technology of Electrometals Technologies Ltd. uses a rapid flow of electrolyte through a cylindrical cell to deposit copper or other metals from dilute solution (less than 1 g/L) [1]. The copper can be deposited as powder or may be harvested as a tubular cathode product. The advantage of the use of EMEW® technology at Skorpion Zinc will be to eliminate the use of expensive zinc dust and to produce a high value copper product for sale. Following extensive bench test work, a piloting campaign was carried out at Skorpion Zinc. The tests demonstrated the ability of the EMEW® cell to effectively remove copper from solution through direct electrowinning at lower operating cost than cementation. Keywords: Skorpion Zinc, copper, cementation, direct electrowinning, EMEW®

Jan 1, 2007