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By I. Cerny, M. Vanek, J. Hubácek

"SWOT analyses and the closely related TOWS matrix are frequent starting points for an organization to develop its strategy. The paper deals with the evaluation of the TOWS matrix and presents three novel approaches to evaluate the different factors of the TOWS matrix, namely (1) approach to evaluate the factors with identical weights; (2) approach to evaluate factors with their weights determined within the different quadrants of the TOWS matrix; and (3) approach to evaluate factors with weights determined within the whole TOWS matrix. The third approach has two variants. The proposed approaches to evaluate the TOWS matrix were tested on a SWOT analysis of a significant mining company in the Czech Republic. The results imply that the strategy W-T (weaknesses-threats) is recommended in three cases, while the strategy S-T (strengths-threats) is recommended once. The paper may be valuable for managers responsible for strategic planning.IntroductionThe process of human needs gratification has been closely connected with raw material resources of the planet. In the contemporary socio-economic conditions, the task of the mining company managers, apart from extracting mineral resources, is to meet the owners' intents.The managerial work itself becomes very complex. In mining companies in particular, the complexity is augmented by the characteristics of the business. Undoubtedly, the key factor is that mineral resources cannot be renewed or relocated. Stojanovi (2013) characterizes mining projects as involving great investments in finance and time, as well as consecutive decisions and a 'complex mosaic of numerous unknown factors that affect the value of the project'. He adds that mining projects are typified by a 'number of geological, technological, technical, economic, environmental, social, and financial risks' (Stojanovi , 2013).Inter alia, the managerial work may also be intese due to the dynamic internal and external conditions for the existence of any company (Vane? k, 2014). This tallies with Peter Drucker’s prediction in 1969; that the times at the turn of the millennium could be expected to be turbulent (Drucker, 1969)."

Dec 1, 2018

By K. Ding

The thermodynamic activity of MnO was measured in MnO-CaO-MgO-SiO2 slags that are typically encountered in the production of manganese-containing stainless steels. A gas equilibration-quenching technique was employed in measuring the activities. Activities of Mn in Pt-Mn alloys were redetermined at 1600ºC, which reconfirmed earlier results of strong negative deviations. MnO activities were then measured by equilibrating slags of various compositions based on a statistical experimental design procedure with Pt-Mn alloys under controlled partial pressure of oxygen in MnO saturated platinum crucibles at 1600ºC. Activities of MnO were found to increase with increasing concentration of MnO, basicity and CaO to MgO ratio. Two multi-coefficient regression models were developed to predict the activities and activity coefficients of MnO in slags at 1600ºC. Keywords: activity, MnO, slag

Jan 1, 2005

By A. H. Swart

Unplanned stope panel collapses occur on most near-surface and shallow mines in South Africa. Although these incidents often occur during blasting, they pose a major threat to the safety of underground workers and the economic extraction of orebodies. Most stope panel collapses occur due to excessive panel lengths (resulting in excessive stope spans) that are not designed according to a systematic design procedure or methodology. Instead, panel lengths are often dictated by the equipment in use and by previous experience under similar conditions. Hence, a rock engineering design methodology for the design of stable stope panels between pillars is of vital importance for optimum safety and production in shallow mining operations. Using the proposed design methodology described in this paper, rock mechanics practitioners and mine planners should be able to identify and quantify the critical factors influencing the stability of stope panels. The critical factors should then be used as input to the design of stable stope panels that will provide the necessary safe environment for underground personnel working in stopes. The proposed design methodology is an iterative process, which includes aspects such as rock mass characterization, estimation of rock mass properties, identification of potential failure modes, consideration of appropriate stability analyses and other elements of the rock engineering design process. This process continues after implementation. During monitoring, new data should be included in the database and the design process repeated on a regular basis. Design approaches included in the proposed design methodology include empirical methods such as different rock mass classification methods, analytical methods such as elastic and Voussoir beam analyses, kinematic analyses, probabilistic analyses, and numerical analyses. Keywords: stability, stope panels, design methodology, hardrock mines, shallow mining operations

Jan 1, 2005

The safety of mining operations is significantly influenced by the in situ stress fields in which the mining excavations are created. From the point of view of planning of mining operations, the in situ stress field is a most important input parameter for valid modelling of excavations. Many in situ stress measurements have been carried out for mining and civil engineering projects in southern Africa over the past 30 to 40 years. A database of in situ stress measurement results and observations has been compiled. This paper presents results extracted from the database which are considered to be of particular interest to mining areas in South Africa. The database will permit the estimation of likely stress conditions in new areas of mining, provide a basis for evaluation of results from future in situ stress measurement programmes, provide a basis for comparison of observed behaviour with expected behaviour, and provide a source of data on which realistic design and layout analyses can be based. The information contained in the database indicates that horizontal to vertical stress ratios in the Carletonville, Klerksdorp and Rustenburg areas are significantly higher than the value of 0,5which is commonly used in mine layout planning.

Jan 1, 1998

By A. Kostin

GIS and multivariate geometric distribution have been used to predict the association of high-level intrusives with hydrothermal alteration related to iron oxide Cu-Au (IOCG) mineralizing systems. Several examples in the Russian northeast are presented in this paper. IOCG ore deposits can have enormous geological resources containing significant reserves of base, precious, and strategic metals, and hence are economically attractive targets for mineral exploration. To date, examples of this type of mineralization have not been reported from the northeastern area of Russia. The Tarinskiy ore cluster, located in Eastern Yakutia, shows brecciated altered rocks with sulphide and iron oxide cement, which is typical for IOCG mineralization of the iron oxide Cu-Au±U type. This cluster was formed near surface and is linked with the Rep- Yuruinskiy pluton. It has potential to host new world-class precious metal deposits in northeastern Russia

Jan 1, 2014

By D. L. H. Bulbring

The removal of a cylindrical core from thick-wall sections for creep analysis by the relatively new Weldcore® process represents a very exciting methodology for obtaining more representative creep damage data from large engineering structures. The cylindrical core that is removed, representing about 60% of the wall thickness, leaves a substantial removal site that needs to be repaired. This paper presents data pertaining to taper Friction Hydro Pillar Processing as an alternative repair technique for filling the core removal site. Process parameters were evaluated with special attention being paid to the effect of downward force on process response variables, weld defects, and mechanical properties of 10CrMo910 steel. Process temperature and torque response as well as total process energy input were also considered. This paper also assesses the static and dynamic performance of this repair technique. The influence of a varying downward force and the occurrence and position of discontinuities were quantified. Downward force was shown to have the most notable effect on weld joint dynamic performance and was found to be related to the process temperatures achieved in close proximity to the weld interface.

Jan 1, 2013

By J. J. Bezuidenhout

The waste-heat boiler is used within the Sulphide flash smelting process as the main dust and energy recovery unit. The large volume of off-gas discharged from the flash smelter is at a very high temperature (1350°C) and contains a significant dust load that subjects the downstream waste-heat boiler to tough and demanding conditions. The boiler cavity is especially prone to dust accretions, fouling, and corrosion caused by accumulation of molten particles and precipitation of sulphuric acid. Computational fluid dynamics (CFD) is applied within a qualitative study to model the flow and heat transfer distribution throughout the waste-heat boiler. The commercial CFD package, Fluent 6.2.16, was applied to a modified waste-heat boiler (23 m ×11 m ×5.4 m) within the Outokumpu flash smelting process. This investigation focuses on the geometric modifications to the typical boiler design, which includes elevation of the ceiling, placement of flow-obstructing baffles and radiation plates parallel within the flow path. Also investigated were various boiler operating conditions such as the circulation of process off-gas, air leakage from the dust discharging hoppers and variation in inlet gas composition. The geometric modifications had the desired effect of increasing the volumetric utilization and therefore enhancing heat transfer between the boiler surface and the gas stream and dust segregation. Introducing circulated off-gas at a rate of 20 m/s and at a 45° angle to the front of the waste boiler further enhanced cooling while reducing the high impact of the furnace-uptake gas-stream on the boiler ceiling. The placement of radiation plates was found to be very effective in enhancing the heat transfer surface and distributing gas flow within the boiler. These results present recommendations towards an improved waste-heat boiler design. Keywords: flash smelting, waste-heat boiler, CFD simulation, off-gas cooling.

Jan 1, 2008

By W. Stumpf

Mill log analyses and complementary hot deformation studies were carried out on the as-cast structure and on a hot rolled structure of the same low carbon steel (SAE 1006) that had been processed according to the direct or hot charge route in a compact strip plant. The main softening mechanisms during hot rolling were found to be complete dynamic recrystallization during each pass above about 1000°C for the as-cast structure with an austenite grain size of 277µm and, secondly, incomplete static recrystallization after each pass with a finer austenite grain size of about 26 µm and tested below 1000°C. A two-stage hot working mechanism has also been found by others on a similar steel also processed by the hot charge route and this may appear to be a characteristic of this type of material. Constitutive constants determined from hot working studies were combined with other constants from the literature and incorporated into a grain size development model that correctly predicts the final ferrite grain size in the hot rolled strip steel. The predicted incomplete static recrystallization during the last three finishing passes in the plant appears to result in some retained strain in the hot rolled austenite as it transforms to ferrite on the run-out table. Analyses with the model predict relatively little sensitivity of the final ferrite grain size to process and product variables such as temperature and strain per pass for the last three passes and also the starting austenite grain size in the slab. Keywords: Low carbon steel, hot rolling of strip steel, rolling mill log analyses, austenite grain size, ferrite grain size, grain size modelling.

Jan 1, 2003

By M. L. Bakker

The ISASMELT? top submerged lance (TSL) bath smelting process was developed in Mount Isa, Australia by Mount Isa Mines Limited (now a subsidiary of Xstrata plc) during the 1980s. By the end of 2011, the total installed capacity of the ISASMELT? technology will exceed 8 000 000 metric tons per year of feed materials in copper and lead smelters around the world. Commercial plants, operating in Belgium and Germany, are also batch converting copper materials in ISASMELT? furnaces. This TSL technology is equally effective for continuous converting processes, in which role it is called ISACONVERT?. This paper presents the recently patented ISACONVERT? process for the continuous converting of nickel and platinum group metal (PGM) containing mattes using the calcium ferrite slag system. The paper focuses on the potential application of the ISACONVERT? technology to existing nickel and PGM smelting complexes.

Jan 1, 2011

By P. Mbele

Iron ore concentrate is not easily transported to, or processed in, ironmaking plants, therefore it is necessary to agglomerate. This paper will determine the possibility of agglomerating Sishen concentrate into suitable ironmaking feedstock. Pelletizing is one of the conventional and preferred agglomeration processes for iron ore concentrate investigated at Kumba Value-In-Use Laboratories. Sishen concentrate was mixed with binder, and then pelletized using a laboratory pelletizing disc; afterwards the green pellets were indurated at high temperatures to give strength high enough to survive handling and lessen disintegration in the shaft during ironmaking. Sishen pellets have satisfactory physical and metallurgical properties which make them suitable feedstock for the direct reduction processes. These were tested under Midrex shaft operational conditions and performed well, with a metallization of 94.47% being attained.

Jan 1, 2012

By M. J. Lukhele

Paper written on project work carried out in partial fulfilment of B. Tech (Mining Engineering) degree A number of high wall mining methods were developed over the years to mine coal reserves exposed on the high walls created during surface mining. The auger mining system was initially developed in the early 1940s in the United States of America. High wall mining is a method of recovering coal from seam exposed either by mechanical excavation methods or natural erosions. This is usually associated with strip-mining (opencast) where the stripping ratio is high and uneconomical to mine using the opencast mining method. This paper discusses the surface auger mining as deployed at Rietspruit Mine Services Proprietary Limited.

Jan 1, 2002

By H. J. Glass

Collection, preparation, and analysis of blasthole chippings is expensive. Frequently, interpolation of grades at unsampled locations is considered using techniques like kriging. A pre-requisite for kriging is that an experimental variogram is established. In order to assess the quality of the experimental variogram, a measure is developed in this paper. The measure is derived from analysis of the time-honoured expression relating the variance, semivariance, and covariance. It reflects the weighted average deviation of the summed semivariance and covariance from the biased variance. The proposed measure allows assessment of the influence of key variables on the quality of the variogram. Using simulated data, it follows that the quality improves with an increasing number of samples, increasing density of the sampled locations, increasing regularity of the sampling pattern, and increasing uniformity of grades in the absence of correlation. Application to real data shows that the minimum number of samples could coincide with a marked decrease in the value of the measure. Establishing a threshold value is subject to further research. Keywords: variogram, variance, covariance, semivariance, minimization, sampling.

Jan 1, 2003

By B. P. Watson

Several large falls of ground occur annually in the narrow, tabular stopes mined in the Bushveld Complex. These falls comprise safety risks and cause substantial production losses and compromise efforts to increase productivity. Underground observations in conjunction with instrumentation sites were used to establish the strategic parameters required to describe the rock mass behaviour of shallow-dipping stopes on the Bushveld platinum mines. Existing rock mass rating systems were evaluated using the observations and instrumentation results. None of the current systems adequately described all the relevant geotechnical conditions. Thus a hybrid of several current systems was developed, and the proposed system is discussed in the paper. The new rock mass rating system is termed the ?New Modified Stability Graph? system and follows the method originally described by Mathews et al.1and revised by Hutchinson and Diederichs2.Changes have been made to some of the tables provided by Barton3and to the stress analysis suggested by Hutchinson and Diederichs2. In addition, the logistical regression analysis has been applied to databases, formed using the suggested analyses, for three support resistances and risk levels established.

Jan 1, 2004

By C. Balci

Specific energy is defined as the amount of work required to break a unit volume of rock and is used to predict the performance of mechanical miners. It is obtained from full-scale rock cutting experiments, which require large block samples, experienced personnel and expensive equipment found in only a few research centres in the world. Estimation of the optimum specific energy, at which a given geological formation is excavated at optimum cutting geometry in the most energy efficient manner, from mechanical rock properties to predict the performance/efficiency of roadheaders is the basic aim of this study. The mechanical rock property tests require only core samples, which are easier to obtain and to test. In this context, full-scale rock cutting tests are performed on 23 different rock, mineral and ore samples including sandstone, claystone, tuffite, chromite, trona and copper collected from some operating mines in Turkey. The optimum specific energy values are obtained for each sample. Physical and mechanical property tests are performed on the core samples obtained from the same samples to determine uniaxial compressive strength, indirect (Brazilian) tensile strength, static and dynamic elasticity moduli, Schmidt hammer rebound values, density, and Cerchar abrasivity index. The relationships between the optimum specific energy and the mechanical rock properties are analysed using statistical methods. The results indicate strong relationships between the optimum specific energy and the mechanical rock properties. The strongest relationships are found by using uniaxial compressive strength and tensile strength. The performance models developed in this study are in good agreement with the empirical models previously developed for roadheaders and can be used reliably for prediction purposes. Keywords: Mechanical excavation, roadheader, performance prediction, rock cutting, optimum specific energy, mechanical properties of rocks.

Jan 1, 2004

By C. Siyasiya

One of the problems that is occasionally encountered during the continuous casting of DIN 1.4003 stainless steel (hereafter referred to as 1.4003) is the side bulging effect, a problem that is generally prevalent in ferritic stainless steels. This occurs because the unconstrained narrow sides of the solidification shell are not able to withstand the ferrostatic pressure once the strand has emerged from the mould. Coupled with side bulging, there is strand width variation at high temperatures, i.e. when the steel is in the ferrite-austenite dual phase region. Both of these dimensional changes to the slab profile create some processing problems in subsequent hot rolling operations when unacceptable width variations are encountered. The strength of the solidification shell and its ability to withstand the ferrostatic pressure during continuous casting is dependent on its thickness and phase composition when exiting from the mould up to a few metres downstream. From the study of the high temperature metallurgical behaviour of this steel, it was observed that a thicker solidification shell when exiting from the mould and a higher austenite volume fraction in the steel would be favourable for the reduction of the side bulging effect during continuous casting. It was also found that as long as the d-ferrite to austenite phase ratio keeps fluctuating due to variations in chemical composition and process control in the dual phase region from cast to cast, the strand width variation problem would probably persist. The remedy to this effect lies in more strict chemical composition and process control during continuous casting of this steel. The hot ductility experiments revealed that 1.4003 exhibits good hot ductility in the strand straightening temperature range with a minimum of 75 per cent reduction in area and this was attributed to the high volume fraction of ferrite (0.2 to 0.4) in the steel. This would provide a remedy to side bulging by increasing the secondary cooling rate of the strand in order to form a thicker solidification shell without necessarily risking transverse cracking and other surface defects during unbending. Keywords: side wall bulging, resistance bending moment, applied bending moment, ferrostatic pressure.

Jan 1, 2005

By P. K. Sahoo, C. R. Ray, S. S. Rao

Good operation of Soderberg electrodes is dependent upon high quality electrode paste coupled with better electrode management procedures. Without having a good electrode operation, it is not possible to obtain the best outcome from the furnace. In other words that is a good way to say how important the proper electrode operation is. Good electrode performance depends on the slipping rate and current levels, which decides the shape of the baking curve at the level of just below the contact clamps. Negative curvature of baking zone in the central part is considered dangerous because shrinkage takes place outwardly creating abnormal stresses in the electrode. Soft breakages occur when the baking zone comes below the clamps and the casing cannot take the current. This paper deals with various factors affecting baking characteristics leading to soft breakages and also presents case studies in a closed 48MVA furnace with smelting for charge chrome. In case studies in a closed furnace, it has happened that the energy for baking at the low current operation before breakage has been lower than the actual slipping has demanded. At low current there should not be problem, but a problem can occur when the current for some period is raised above the current carrying capacity of the casing. So data for electrode operation in actual period was studied and presented in this paper.

Jan 1, 2007

By H. Kotzé

Ticor SA began with a detailed feasibility study in 1995. The Hillendale mine (situated between Richards Bay and Empangeni) and mineral separation plant were approved in 2000. The smelter, just outside Empangeni, consists of two 36 MW DC arc furnaces that were commissioned in 2003. Experiences gained during the initial commissioning of the furnaces proved valuable in later commissioning work, as shown by the increase in ramp-up rates. The capacity of the plant is 250 kt/a TiO2slag and 145 kt/a of pig iron.

Jan 1, 2006

By A. A. Angelov

This paper presents a unique method of monitoring the effectiveness of the planning process as well as the execution of mine plans. The method primarily determines the degree of deviation from the original mine plans by comparing actual mined areas to initially planned mining areas. The performance of mining operations is also measured by comparing actual and planned tonnages for a particular period. Once the degree of deviation from mine plans has been established the cause/s of the deviation can be determined through a simple fault tree analysis. Accurate identification of the reasons of deviation can aid the mine in selecting possible methods to correct the deviation. It is, however, beyond the scope of this paper to discuss the methods employed in correcting such deviations, as each mining operation will have unique causes of plan deviation and methods of remedying them. Deviations from the plan greatly affect the yields obtainable, which in turn affects the life of mine, thus having negative economic and financial implications. Accordingly, this paper presents a project management method which aims to reduce risk by improving planning systems to ensure optimum overall extraction of coal reserves.

Jan 1, 2010

In ilmenite smelting, the FeO content of the feed material (nominally FeO.TiO2) is decreased by reduction with carbon. In a parallel reaction, a significant amount of the TiO2 is reduced toTi2O3. One of the striking features of these reactions is a consistent relationship between the extents of FeO and TiO2 reduction; this relationship is independent of furnace size. It was recently proposed that this relationship follows from the solidification behaviour of the slag, where the final slag composition corresponds to the minimum melting point (?eutectic groove?) in the FeO-TiO2-Ti2O3 phase system; the hypothesis is that solidification equilibrium with the freeze lining stabilizes the slag composition. If this is the case, the system of slag and freeze lining must be capable of correcting two types of disturbances: thermal and compositional. Thermal disturbances result from incorrect power input, for the feed rates of ilmenite and reductant. For example, excessive power input will tend to overheat the slag, causing the freeze lining to melt partially, establishing a new steady-state heat loss from the furnace. Compositional disturbances result from an incorrect reductant input for the given power and ilmenite input. In this work, the dynamic response of the slag and freeze lining to different inputs (flow rates of ilmenite and reductant, and power input) is modelled. The model is based on solidification equilibria, and quantified heat loss through the freeze lining. The conclusion is that the solidification equilibrium cannot constrain the composition to the eutectic groove for typical operating conditions. Keywords: ilmenite smelting, freeze lining, solidification, high-titanium slag

Jan 1, 2004

By B. Das

he flotation studies on hematite were carried out using di (2-ethylhexyl) Phosphoric acid (D2EHPA) as the collector. The possible mineral reagent interaction was studied through electrokinetic and dissolution studies. The shift in zeta potential (PZC) and decrease in dissolution of iron in the presence of D2EHPA indicated that D2EHPA was specifically adsorbed on hematite surface. The adsorption imparted necessary hydrophobicity for flotation of hematite. Hematite could be floated selectively from hematite and quartz synthetic mixture. Key words: Hematite, D2EHPA, flotation, electrokinetics, dissolution.

Jan 1, 2003