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This paper provides a review of the chemical reactions occurring in the submerged arc processing of chromite ores. The excavations of industrial furnaces have shown that the charge, as it descends through the furnace, passes through a number of distinct reaction zones. Each zone is characterised by differing process conditions and reaction products. The phase equilibria, reaction steps and mechanisms occurring as the charge progresses through the furnace are examined, and the potential influences of these factors on the process outcomes are discussed.

Jan 1, 2004

By M. A. van Nierop

Load behaviour in an industrial mill has been measured directly by inserting probes through liner bolts. The data from conductivity probes have indicated the presence of premature centrifuging during manipulation of the load mass. Overloading conditions were also encountered. Overloading and premature centrifuging both reduce the power drawn by the mill. These effects have been successfully modelled.

Jan 1, 1997

By G. I. McPhail

The authors have conducted several investigations into the prediction of the beach profile of high-density tailings and have found that there are a number of important considerations that need to be taken into account over and above the reliability of the beach profile prediction methodology. These considerations relate to the chemistry of the slurry and specifically the influence of pH and flocculation, both of which have a significant influence on the rheology of the slurry at the discharge point. A number of examples are discussed and a potential testing protocol that will assist in assessing the influence of chemistry ahead of the beach profile predictions is presented. A methodology for assimilating the results of the testing into the likely field situation is discussed, and suggestions are made on application of the results in beach profile prediction. The suspected influence of residual flocculation on the stratification

Jan 1, 2012

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 M. Stachowiak, M. Nowicki, K. Walas, A. Skoczylas, P. Stefaniak

In this paper the authors present a walking robot dedicated to the inspection of a belt conveyor’s transportation system in an underground mine. The developed robot can independently diagnose all of the key rotating elements of the belt conveyor (pulleys, bearings, drums, gears, engines) based on vibration and acoustic signals as well as typical RGB (red, green, blue) and thermal images. The article presents key diagnostic procedures applied to real industrial data obtained during robot testing.The work was developed as part of the ‘THING–subTerranean Haptic INvestiGator’ project. The authors presented the main assumptions of the research methodology developed for the needs of technical diagnostics of conveyor elements typical of inspection work performed by mining staff. Based on industrial data, the use of algorithms for elements such as rollers, drive stations, and the conveyor belt were shown. The main assumption of the research is to develop a robot adapted to the conditions of a deep mine, capable of carrying out an autonomous inspection of mining infrastructure. The conducted tests and the developed fault detection algorithms were aimed at preparing the robot for underground tests in the operating conditions of the mine.

Sep 1, 2021

By B. Erdem

This article introduces a computer model, which emphasizes panel design for draglines deployed in direct side-casting mode. The study covers flat and inclined coal-seam conditions with the dragline operating along the strike-line. Two casting methods are embedded in the model: material is placed in the open set adjacent to the one on which the dragline is located (the DNS method) and material is placed in the open set adjacent to the one the dragline excavates (the DND method). While in the first method the unproductive walking time is reduced as the set is enlarged, in the second method the cycle time is lessened as the dragline swings along an acute angle. The side-casting model is shaped so as to provide several panel configurations instead of a single one to conform to the characteristics for an opencast mine. This is achieved by assigning the pit width an interval of values ranging from a minimum to a maximum. The model includes solutions to other critical design parameters such as: set length, swing angles at key cut and main cut positions, and required dragline reach at key cut and main cut positions. The model outcomes reveal the following: the stripping operation is largely affected when the coal-seam is inclined. The downhill spoiling mode should be applied wherever possible. The DNS pattern allows wider pit width intervals as well as longer sets and longer reaches.

Jan 1, 2004

By F. J. Plaul

The dominating technologies for steelmaking are the basic oxygen furnace (BOF or LD process, Linz-Donawitz) and the electric-arc furnace (EAF). The main iron input materials for both are liquid iron as hot metal, or solid iron as pig iron, DRI (direct reduced iron), HBI (hot briquetted iron) and scrap. Hot metal, pig iron (i.e., solidified hot metal) and DRI/HBI are virgin iron materials, which have to be produced from iron ore by so-called ironmaking technologies. The family of ironmaking technologies includes three process routes: blast furnace, smelting reduction and direct reduction. Driven by steadily increasing costs of raw materials in the last two decades, the sector has seen a number of new developments in ironmaking technologies, developments based on fluidized-bed technology. The main advantage of a fluidized-bed technology is that fine iron ore can be directly charged to the process without prior treatment; it does away with agglomeration and its concomitant cost, a step practised in blast-furnace, COREX® and MIDREX® processes. With Posco of South Korea, Siemens VAI Metals Technologies has successfully developed the FINEX® process, a smelting reduction based on the direct use of iron ore fines to produce hot metal. The key technology is the four-stage, bubbling fluidized-bed-reactor system, in which fine iron ore is reduced to DRI fines in a countercurrent flow with a reducing gas generated by coal gasification. Beside surveying the current state of the art, this paper discusses the technological principles of smelting-reduction and direct-reduction processes. The status of FINEX® and the outlook for further developments are described. Crucial to the successful development of the new ironmaking technologies for the direct use of fine ore was the scaling up of the fluidized-bed reactor system, which demonstrated new design features.

Jan 1, 2009

By Wynand Erasmus, Terry A. Jones

The Kelsey Centrifugal Jig (KCJ) utilizes the application of centrifugal force (and the resultant enhanced gravitational field) to conventional jigging technology principles to successfully process materials where the valuable constituent particulates are very fine and/or where there is a small specific gravity differential between these and the gangue minerals. The KCJ has been successfully employed in mineral sands applications in Australia for approximately 12 years. More recently, the KCJ has been tested and installed on zircon tailings dump retreatment projects in Australia and the USA, while being considered for similar projects in RSA, and is about to be installed in zircon tailings processing duties in India and Africa and in a tin removal duty in a rutile circuit in Australia. Extensive test work has been carried out on these applications and some typical performance data is presented in this paper. Information is also provided on the principles of operation of the KCJ and on the keys to a successful KCJ installation.

By H. Yilmaz

Tensile strength testing has been one of the most common physical property testing methods of thin spray-on liner (TSL) products worldwide. However, the variety of products tested has been insufficient for comparison purposes. Specimen preparation procedures and test parameters such as curing time and loading rate are not reported well. Comprehensive tensile strength testing on 20TSL products and one plain shotcrete brand was performed over 28days of curing period. Detailed information on the test procedures with particular attention on the important aspects during sample preparation and test execution are provided. As expected, the tensile strength increases with increasing curing period. The test results make the categorization and comparison of liner products possible.

Jan 1, 2010

By R. V. Peche

Since 1952, Bond’s equation has been used as a standard to predict the specific energy of grinding for a given duty. The Bond’s equation considers that the exponent is constant for all conditions. Hukki, in 1961, pointed out that the exponent is a function of the particle size, and concluded that the Bond’s equation applies successfully for an intermediate range of sizes; out of this range the Bond’s equation leads to high error as demonstrated in this paper. More recently, in 2004, S. Morrell presented a new formula in which the exponents vary with the feed and product size. This paper is based on Hukki’s approach and presents a new general formula, in which the exponent varies only with the feed particle size. This new equation has been proven in 82 observable cases in Peru and other countries around the world, involving ball mills and vertimills in different configurations over a wide range of feed and product sizes, work indices and mill diameters; in most cases, the predicted value has an error less than 10% with regards to the observed value and no need for any correction factor. Keywords: Grinding, specific energy, particle size, work index, variable exponent

Jan 1, 2020

By E. Tabosa, S. Vianna, K. Duffy, W. Valery, B. Andrade, L. Pyle, P. Holtham

Pneumatic flotation cells are high-intensity flotation machines with rapid kinetics, resulting in short residence times. Examples include the Jameson, PneuFlot and ImhoFlot cells. These cells do not use impeller-like mechanical cells. Rather, the air and pulp are mixed in a continuous stream of high fluid velocity through a downcomer or venturi to disperse the air into fine (approximately 0.5 mm) bubbles and maintain particle suspension. Froth wash water is often used to enhance concentrate grade, minimising recovery by entrainment. With the growing application of these types of cells, not only in cleaner stages (their traditional use) but also in pre-flotation and scalping duties, there is a need to predict their performance more accurately for circuit design and optimisation. No widely accepted model for pneumatic flotation cells is available and their metallurgical performance is often scaled up from laboratory and/or pilot plant testing by assuming fixed values for metal recovery, concentrate grade and concentrate percent solids. This paper describes a new approach to simulate pneumatic flotation cell performance and presents case studies demonstrating its applicability. Keywords: Pneumatic flotation, flotation modelling, flotation circuit design, flotation circuit optimisation, Jameson cell

Jan 1, 2020

By J. Daavittila, P. Jokinen, M. Honkaniemi

In the latter part of the 1980?s Outokumpu Chrome in Tornio, Finland, was in a situation when its twenty-year-old ferrochrome plant was becoming inefficient to sustain economically sound production. The company made extensive studies on the then available processing methods to find out the best possible processing route. As a result the whole plant was practically rebuilt and expanded. When equipment was proven in practical operation an application for FeMn production was developed. Now when Tornio FeCr-plant is considering the expansion the same type of exercise is to be performed with today?s challenges, which will be discussed in the paper. These challenges include increasing costs or decreasing quality of raw materials, increasing energy costs, stricter environmental regulations and demand of better working conditions. The possibilities to respond to these challenges will be discussed in the paper. The future and continuing development with FeCr includes the better utilization of process dusts and a lower consumption of energy. By adapting the latest automation tools to better control of the process even higher efficiencies can be achieved with present technology. New processes are considered for development in the future and some possible technologies will be described.

Jan 1, 2004

By W. de Beer

We present aspects of one of several ongoing case studies used in the development of prediction techniques for major seismic instabilities. The current investigation centres on accelerated coseismic deformation described by the kinematics of failure and on softening, as well as the characterization of areas of interest by measures of the seismic response at such sites.

Jan 1, 1998

By I. Mc Dougall

Finite element models were generated of two submerged arc furnaces of different geometries. A 48MW circular furnace and a 68MW 6-in-line rectangular furnace were studied. The electrodes, raw material, slag and molten metal were included in the model. ANSYS/Multiphysics was used to predict the current density distribution in the electrodes, raw material, slag and molten metal as a result of the three phase AC current. The effect of the electrode immersion on the current path was studied. The ?proximity effect? caused a pronounced asymmetry in the electrode currents in the circular furnace, whilst the electrode currents in the rectangular furnace exhibited radial symmetry. The current distribution in the melt in both furnaces indicated that the bulk of the current flows between phases. The current density is greatest between electrodes. Results were compared to qualitatively similar published work, operating experience and results of furnace dig-outs.

Jan 1, 2007

By W. Mbhalati

"Conzal Mine was not meeting production targets in 2013, and it was established that this was caused by the inability of the load haul dump machines (LHDs) to tram the required tonnages. An investigation of the LHD productivity was therefore conducted to identify the inhibiting factors. This was accomplished by carrying out a literature review on LHD operations to gain in-depth knowledge and conducting observations in the working environment. The relevant information and data on the LHD type used at Conzal was also acquired.The major inhibitor was found to be excessively long tramming distances in all the sections of the mine. The one-way tramming distances were all significantly greater than the 90 m set in the mine’s code of practice (COP), with the Main Shafts section having the longest average one-way tramming distance of 260 m. The other inhibitor was LHD utilization, which in 2013 was only 47% against a target of 70%. Simulation of the LHD operation, taking these two factors into account, showed that production could be increased by more than 100%. As a result, it was recommended that conveyor belts should be extended regularly in order to keep tramming distances within the recommended one-way distance of 90 m. In addition, utilization can be improved by minimizing employee absenteeism as well as by modifying the travelling routes such that LHDs do not encounter unnecessary delays.Paper written on project work carried out in partial fulfilment of BSc. (Mining Engineering)"

Jan 1, 2015

By J. N. Van der Merwe

The research described in the paper was aimed at providing standardized information of cases of failed and intact coal pillars in the form of databases to researchers. It also offered the opportunity to take stock of the pillar stability situation in coalmining and to review the impact of the application of the safety factor formula for pillar design. It was found that the physical parameters of coalmining have not changed substantially over the last four decades. However, changes in the controllable parameters like pillar width, pillar width-to-height ratio and percentage extraction have all moved toward the more conservative side. Scrutiny of the database indicates that of all the failures recorded, only 23 occurred in panels that were mined after 1969, when one can assume that the safety factor formula was fully applied. If the pre-1969 practices had been continued, at least 144 collapses would have been expected. There has thus been a substantial reduction of pillar collapse cases, justifying the cost paid for the formula, which has shown to be in the region of 600 million tons of coal. It is evident that that are distinct differences in the natures of the failures among different coalfields. This justifies the attempts to derive seam or coal field specific strength formulae and is a topic that should be pursued.

Jan 1, 2006

By T. J. Otto, G. C. Lindeque

Productivity is improved by increasing the ratio of output to input. In an operating open-pit mine, improving the productivity of heavy mining equipment (HME) enables the unit cost of production to be reduced. To optimize HME productivity, the Kolomela open-pit iron ore mine transitioned to an enhanced short-term mine planning (STMP) process that supports the application of a manufacturing-type operating model. At the core of the enhanced STMP process is a focus on integration across the open-pit mining value chain. The interdependencies between mining activities are highlighted and emphasized, thus ensuring that mining activities are synchronized. The improvements related to HME productivity were monitored from 2019 to 2020. The utilization of mining area in the Leeuwfontein pit improved from 71% to 90%, and the blasting frequency reduced by 14% while the average blast size increased by 17%. The distance travelled during shovel relocations between mining phases reduced by 16%, and the lost time associated with drills relocating reduced by 53%. These productivity improvements resulted in an 11% increase in the loading rate of the main waste shovel at Kolomela from 0.9 Mt/month in 2019 to 1.0 Mt/month in 2020. The enhanced STMP process can be adapted to other open-pit mining operations.

Nov 1, 2021

By M. H. Solomon

After the global financial crisis of 2008, African mining is entering anew phase of development. The rapid withdrawal of emerging market funding from the critical exploration and development industries provided a hiatus in funding, a gap which was quickly filled by Chinese and other Asian investors. While the continent is still economically dependent on its extractive industries, the prevalence of Dutch Disease has undermined Africa?s ability to benefit fully from its mining, oil, and gas industries. While the extractive industries are closely related to many of the more fragile and failed states in Africa, it is equally true that the strongest states in Africa have mining-based economies. This paper explores the possible linkages between mining, strong and weak political economies, and poverty in Africa. It draws the conclusion that neither Dutch Disease nor Resource Course is a given in resource-endowed countries, and that it can be avoided if the mining economies in these countries are actively integrated into their respective broader economies and used to foster economic diversification. The author asserts that given the capacity constraints of many African governments, it is contingent on mining companies to become integrally involved in catalysing diversification around their infrastructure and supply chains.

Jan 1, 2011

By F. T. Cawood

The distinction between real estate ownership and that of interests in the property is fundamental to the appraisal of mineral properties. This distinction affects the nature and understanding of security of tenure and, consequently, the perception of what constitutes fair value. Legal matters are a particular concern because of their influence on security of tenure, ownership definition and use restrictions. The dynamics of the market and the complex interrelationships between the factors of production define value at a specific point in time for the bundle of rights, interests and assets that constitute a mineral property. Because each mineral property is unique, physically immobile and of a wasting nature, its usefulness to its owner and society must be optimized. The US Appraisal Institute (2001) classified the forces that affect land use as the cultural, political and economic attitudes of society. These forces culminate in laws that often dictate the purposes for doing appraisals. Once the legal definition of the asset is understood, valuers can decide on the valuation process that will support the final valuation approach.

Jan 1, 2004

By D Reddy

Rosh Pinah Zinc Corporation is a zinc-lead mine located in southern of Namibia. It is currently considering the development of a low grade ore body containing about 2.8% zinc. This ore can be utilised by the concentrator if it could be upgraded prior to the ball mill. Preliminary work indicated that the ore may be upgraded in a pre-beneficiating stage by using dense medium separation, X-ray sorting or a combination thereof to a feed grade of minimum 9% zinc. This paper describes the process followed in evaluating the technologies for pre-beneficiation. The results from test work indicated that the low grade ore is amenable to pre-beneficiation by both dense medium separation and X-ray sorting. A comparison between the two technologies showed that dense medium separation marginally outperformed X-ray sorting on grade and recovery. The results for the X-ray sorting were achieved by tuning the calibration curve specifically for the samples tested.

Jan 1, 2008