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By J. Kirsch

Keywords: Pyrometallurgy, pneumatic transport, pneumatic transport Dense-phase pneumatic injection has begun to replace more traditional furnace-feeding systems. The paper describes the technology as it is applied to processes where the back pressure at the point of injection is greater than 50 kPaG. It reviews earlier systems of injection and more recent developments that address concerns for instantaneous control in modern smelters. The new technologies fall into two groups, (1) modified pressure-difference control (sub-divided into simple and complex) and (2) mechanical-feeder-based control. Features of current injection systems include feed splitting in two forms, passive and active, and co-current injection.

Jan 1, 2006

By David Colloby, Darelle T. Janse van Rensburg

Premature coating failures of new and refurbished structural steelwork of clarifiers have been a common occurrence at power generation plant in recent years. Several of these failures have ended in disputes regarding which party was actually to blame for the early degradation of the coating system, i.e. quality of the power station?s water, poor application, substandard materials, outdated corrosion protection specifications, etc. Having investigated several of these premature failures, it is clear that the corrosion protection of clarifier steelwork is a highly complicated process and that the painting work needs to be closely monitored in order to ensure long-term protection by whichever product that is applied. The need for quality control inspections during the painting of the plant is often underrated during the project planning stage, also the importance of detailed corrosion protection specifications that consider not only the practical application of the materials, but also the quality control responsibilities of the Contractor, End User and Third Party Inspectorates that may be involved. This paper considers the application constraints of coatings to clarifier structural steelwork and importance of stringent quality control procedures in order to ensure the long-term performance of the corrosion protection systems.

Jan 1, 2006

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 M. Hopf, E. Rossouw

Keywords: Pyrometallurgy, furnace, copper coolers, freeze lining, monitoring, Saveway The use of water-cooled copper components as sidewall elements of submerged arc furnaces and other pyrometallurgical applications has become increasingly common. The high cooling efficiency of copper has made it possible to increase the service life of furnace refractories when compared to conventional refractory linings. However even the self-healing effect of ?freezing? worn areas of the lining does not necessarily protect the copper coolers against wear or corrosion completely. In order to avoid furnace explosions, various methods have been used to monitor the wear of coolers. Unfortunately, these have not been able to consistently identify localized wear. Thos Begbie (South African) and SAVEWAY (German) jointly developed technology to embed a line sensor into the copper cooler during the casting process. This system allows an exhaustive monitoring of the copper cooler. A SAVELINE sensor is placed inside the copper-cooling panel between the water-cooling passage and the hot face of the panel. The sensor follows the meandering shape of the cooling water channels. In the first instance, the sensor provides analogue information as the thickness of the copper reduces. Secondly, this wear signal will be confirmed by a signal of interruption if the sensor is washed away. Because of the structure of the sensor, a self-diagnosis is possible and indications can be confirmed (double proofed). Subsequent to the manufacture of some test pieces, coolers for a large submerged arc furnace were manufactured. The sensorized coolers have been installed at the intermittent surface (slag line) where the largest amount of corrosion has been encountered. The system has been operating since December 2005 in what is considered one of the largest submerged arc furnaces in South Africa.

Jan 1, 2006

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 Wayne Burmeister, Danie Benade, Louis Meyer, Hugo Joubert

What is not measured cannot be managed. This is true of most things, including a furnace lining. This paper describes a Lining Management System used for this purpose. It provides the operations staff with a management tool to predict long term lining life and acts as a process optimisation tool. It alarms and records upset furnace conditions. Outputs from the system are described as presented through a specially developed software package and interface. It includes vertical and horizontal furnace sections showing estimated isotherms through the lining as well as the furnace bath. It also shows calculated heat flux values, estimated lining wear and the freeze layer profile. A novel three-dimensional display is described which provides the operator with a big picture view of the furnace crucible profile under real time operating conditions. The powerful trending facility for analysing both measured and calculated values is discussed. The required instrumentation hardware as well as the installation thereof is described, with special reference to an electrically insulating thermocouple socket design. Finally feedback is provided on the first year?s performance of the system installed on an open ferrochrome furnace at Assmang Chrome, Machadodorp, South Africa.

Jan 1, 2007

By J. A. Bakken, M. Tangstad, P. A. Eidem

In the submerged arc production of ferromanganese, sillicomanganese and ferrochromium, the coke bed characteristics play an important role. The basic mechanisms of electric current conduction in the coke be dare not yet fully understood, but important parameters are the material resistivity of coke and the contact resistance between the coke particles. Preliminary tests indicate that the contact resistance is of great importance to the bulk resistance of the coke bed. An apparatus measuring the material resistivity and contact resistance of carbon materials has been developed. Both graphite and industrial coke have been tested. The material resistivity tests were performed on single particles to ensure that the effects of pores and cracks were included and the contact resistances were excluded. Two geometries were tested to obtain the contribution of the contact resistance to the total resistance of two connecting particles. The tests were performed in an inert atmosphere at temperatures and current levels found in industrial submerged arc furnaces. The results show that the method has a satisfactory reproducibility. It was found that the contact resistance is about 10 times higher than the resistance of the material when two particles are in perfect contact and that the resistivity of SSAB coke is more than 10 times higher than that of the graphite at room temperature, but with increasing temperature the difference decreases. For SSAB coke the general trend is that both the resistivity and the contact resistance decrease with increasing temperature.

Jan 1, 2007

By F. X. Prins, L. R. Nelson

Tight control of electrode paste additions, hard and soft paste levels, baked zone position and electrode temperatures are integral to superior Söderberg electrode management practices. Paste addition is typically effected through briquettes, cylinders or large blocks. Each electrode paste form has its advantages and disadvantages, but probably a more crucial element from an electrode control perspective is the frequency and amount of electrode paste addition into a Söderberg electrode column. The detrimental effects of excessive soft paste levels leading to Stokes? Law segregation of paste in the electrode column are well documented, while several operators have effectively implemented the use of electrode thermocouples to monitor paste temperatures and automated slipping algorithms to control baking conditions within electrodes. Somewhat less well appreciated are the negative influences of inadequate soft paste levels, especially when coupled with excessive paste cylinder or block additions and resulting high hard paste levels. The alternative of insufficient hard paste levels and associated overheated electrode paste must also be considered, and can contribute to paste segregation directly. This condition also has the potential to generate gas mixtures in the electrode column that are concurrently a potential health hazard, while being prone to spontaneous combustion. Results of industrial trials on electric furnaces using Söderberg electrodes in a variety of applications from ferrochromium, to ferromanganese and even platinum-bearing base metal sulphides smelting are presented to illustrate the influence of paste loading practices on the dynamics of hard and soft paste levels. Possible electrode failure mechanisms attributable to inadequate paste level control will be discussed through some industrial examples. Suitable paste loading practices to mitigate the risks of inappropriate paste levels and associated electrode incidents are presented.

Jan 1, 2004

By H. B. Arntzen, P. O. Grøntvedt, T. Lindstad, R. J. Ishak, M. Syvertsen

Better utilisation of electric power and coke is vital in reducing production costs and CO2-emissions in production of ferromanganese. All FeMn smelting operations consume 10 to 30 % more carbon than the carbon needed to reduce MnO and FeO to metal and the carbon contained in the alloy. Potassium which re-circulates and builds up in the furnace has been shown to be the main culprit causing both excessive carbon consumption, by catalysing the Boudouard reaction, and increased electric power consumption. The reaction between CO2 and ordinary metallurgical coke or coke impregnated with potassium has been studied at temperatures from 800 to 1100°C in a thermobalance apparatus. Ordinary coke did not react to any great extent at temperatures up to 1000°C, whereas the addition of potassium (2-10 %) resulted in a huge increase in reaction rates. The ultimate goal is to fit the results into a reaction rate model containing the equilibrium constant for the solid-gas heterogeneous reaction between CO2 and a free active site on the carbon reactant producing CO and adsorbed oxygen (an occupied site). The model includes the partial pressures of CO and CO2, a reaction rate constant that is a function of both the total number of reaction sites of carbon, and the potassium content. The potassium dependency is taken care of by introducing activity coefficients for the carbon sites. As the first step towards such a model, a regression line for the Boudouard reaction rate has been established.

Jan 1, 2004

By T. Struminski

The paper is aimed to assess the possibilities of usage of pyrometers and thermal cameras to study ventilation and environmental conditions in underground mines. Surface and underground thermovision tests were carried out in the Rudna mine and included channels and diffusers of some selected fan stations, shaft crest closures, engines of central fans and their instrumentation. The thermovision underground tests in the Rudna mine consisted of ventilation barriers, underground fans, temperature of rocks, ventilation machines, parts of belt-conveyors and electric machinery.

Jan 1, 2003

By S. Thorley

In engineering design of operator?s compartments, in underground mining equipment, ergonomics principles are often neglected or not given the full recognition they deserve. This paper defines ergonomics, applies it to machinery in an underground mining environment and describes the ergonomics analysis undertaken during the design phase of an EJC extra-low-profile mining loader. Encompassing the design of the operator?s compartment of this new loader, this paper illustrates the importance of ergonomics principles within the collective design process, ensuring that it is fully integrated into the design approach. An ultimate aim of this study is to ensure that all future designs follow this route to guarantee not only the outcome of a highly efficient, cost-effective and productive machine but that it is also takes the human factor into account, not only in maintenance but also in operation. Maximizing comfort will have the ultimate outcome of actually increasing productivity.

Jan 1, 2006

A wide range of drill holes and process streams are sampled for resource estimation, grade control, and contractual purposes in the minerals industry. However, despite the availability of training courses, conferences and both national and international standards on correct sampling practices, it is still surprising how often little attention is given to ensuring that representative samples are collected for analysis. The reason for this is that the responsibility for sampling is often entrusted to personnel who do not appreciate the significance and importance of sampling, with cost being the main driving force rather than whether the sample is representative of the material from which it was extracted. This seriously undermines the precision and accuracy of the analyses subsequently generated and can render the analysis process a total waste of time and money and expose mining companies to serious, potential, financial losses. Company management needs to reverse this situation and ensure that sampling is given the attention it deserves to generate representative samples for analysis.

Jan 1, 2010

By S. Z. Pethö, H. Yilmaz

South Deep Mine is currently undertaking numerous voidfilling projects using low strength aerated cement products. Representative samples from one such site, were taken and tested for the load deformation behaviour under uniaxial loading conditions. The process of sample collection, laboratory preparation and testing are explained in detail. The results of testing were analyzed and the critical aspects pointed out as a design consideration to be implemented as part of the quality control and assurance program. Design aspects and underground application of the aerated cement product are discussed for the particular site on 58 level SV1. A simple instrumentation has been designed and installed to enable monitoring of any future movements in this area. A quality control and assurance process has been formulated enabling all aspects of the support installation in this excavation to be signed off.

Jan 1, 2003

By D. O’Connor, A. Pytlik, D. J. Corbett

The resistance of yielding rockbolts to multiple impact loads was tested by means of a drop hammer. The methodology was based on the ASTM D7401-08 standard as well as the requirements specified for rockbolts by Luossavaara-Kiirunavaara Aktiebolag (LKAB – a Swedish mining company) and the Safety In Mines Research Advisory Committee of South Africa (project number GAP 423). During the tests, the loading force and bolt elongation were measured with a sampling frequency of fs = 19.2 kHz. In order to analyse the phenomena involved, the tests were recorded using two independent high-speed video cameras (600 and 1000 frames per second) and one thermal camera (128 frames per second). The tests demonstrated that all the samples transferred double the gravitational potential energy of Ep = 50.85 kJ from the impact load of mass m = 2825 kg and impact velocity of v = 6.0 m/s without failure. Damage to the bolt-resin contact in the upper anchoring zone of the bolt in the steel tube occurred after subsequent impacts. As a result, the macro-deformed bolt exhibits additional yield, and its operation following the shearing of the resin bond is similar to that of a ‘cone bolt’. Only one test resulted in damage to the threaded bolt rod-nut coupling, during the fourth impact; however, no damage to the bolt-resin contact zone was observed.

Nov 6, 2023

By P. R. Segopolo

"The purpose of the project is to convert current shuttle car utilization on an underground coal mine to best practice by focusing on change-out points and tramming routes, which have a major influence on shuttle car away times. Time studies were an integral part of the project as these enabled the determination of shuttle car away times. An indirect proportional relationship between shuttle car away times and productivity is established. Through the time studies, it is deduced that a third shuttle car will make an insignificant contribution to production when there is only one split open. During this time, maintenance on the third car can be optimized. In order to satisfy the mine’s key performance indicator of keeping shuttle car away times less than 75 seconds, a belt extension must be scheduled after the third split is open. It is established that at any given time, a minimum of two shuttle cars should be used. When cutting on the left-hand-side of the belt road with only two shuttle cars available, the centre and left (left of the feeder breaker) shuttle cars should be used for coal hauling. When cutting on the right-hand-side, the centre and the right-hand-side cars should be used. If only one shuttle car is available, the centre car is the most efficient to use. Alternative anchoring configurations can be employed so as to enable cars (left or right, especially) to reach the opposite extremities of the panel and hence minimize cable length restrictions. Paper written on project work carried out in partial fulfilment of BSc. Eng. (MiningEngineering)"

Jan 1, 2015

By Q. Cheng

This paper introduces the multi fractal interpolation method (MIM)developed for handling singularities in data analysis and for data interpolation. The MIM is a new moving average model for spatial mapping and interpolation. The model decomposes the raw data into two components: singular and nonsingular components. The former can be characterized by a localized singularity index that quantifies the scaling invariance property of measures from a multifractal point of view. The latter is a smooth component that can be estimated using ordinary kriging or other moving average models. The local singularity index characterizes the concave/convex properties of the neighbourhood values. The paper utilizes a binomial multiplicative cascade model todemonstrate the generation of one- and two-dimensional data with multi-scale singularities which can be modelled by asymmetrical multifractal distribution. It then introduces a generalized moving average mathematical model for analysing and interpolating data with singularities. Finally, it is demonstrated by a one-dimensional case study of de Wijs’ data from a profile in a zinc mine, that incorporation of spatial association and singularity can improve the interpolation result, especially for observed values with significant singularities.

Jan 1, 2015

By K D. Wilkes

The WEMCO Heavy Media Drum Separator was first introduced by WEMCO in California in the 1940`s, initially from their base in San Francisco and later when the company moved to Sacramento. The WEMCO Company became a part of EIMCO Process Equipment in 1985, and in 2002 EIMCO became a part of the GL&V Group when Dorr-Oliver EIMCO was created. Throughout this period of time the WEMCO Drum has been installed on a variety of different applications and is now operating at the heart of many of the world?s largest Minerals and Coal Processing Plants, as well as being used by many smaller producers and metal re-cycling operations. This paper looks at the practical aspects of using WEMCO Drums in a representative range of processing applications.

Jan 1, 2006

By Q. G. Reynolds

Keywords: Pyrometallurgy, furnace, DC, reverse polarity, dual-electrode The dual-electrode direct current (DC) arc furnace uses two graphite electrodes, one connected as cathode, and one as anode. Such an arrangement avoids some of the design difficulties associated with the anode hearth traditionally used in single electrode and twin-cathode DC furnaces, but can introduce other design and operational difficulties including deflection of the arcs toward the furnace walls. Counter-intuitively, both arc jets in a dual-electrode furnace travel from the electrode down to the bath surface, despite carrying electric current in opposite directions ? this is suggested in the theory of the governing equations of arc formation, and confirmed by experiments using high-speed photography. The dual-electrode arc system at small pilot-plant scale is studied using a transient magneto-hydrodynamic model capable of predicting arc deflection and interaction from first principles, and the results are compared to the behaviour of twin-cathode systems at similar power. Finally, a simple arrangement of the furnace busbars, M configuration, is shown to provide some passive protection against arc deflection.

Jan 1, 2011

By M. L. Bakker

Keywords: Pyrometallurgy, top submerged lance (TSL), nickel, PGM, calcium ferrite, lime ferrite 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 9 000 000 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, whereupon 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 E. S. Schubert

Keywords: co-generation, furnace CO-gas cleaning, disintegrator scrubber, Theisen In a closed, electric, reduction furnace, no oxygen enters the furnace from the surrounding environment. The off-gases are thus not ?burnt? and therefore contain a considerable amount of CO and H2. Traditionally these gases have been captured and burnt in a flare stack. Recent developments have led operators of such furnaces to revise this strategy and to consider utilising these gases as a fuel for gas-fired generator sets to produce electricity, thus becoming more energy efficient. On 31 March 2010 the new emission standards, in accordance with the Air Quality Act, Act 39 of 2004, were promulgated. The minimum emission standards according to the act require that the particulate matter emissions from the primary fume-capture systems on closed furnaces for ?new plants? in ferroalloy and calcium carbide production not exceed 50 mg/Nm³ and 25 mg/Nm³, respectively. By implementing co-generation, the producer automatically complies with the new environmental emission standards for an off-gas. As much as 30% of the electrical power cost, which is set to double in the near future, can be saved by partly generating one?s own electrical power. In December 2010, the National Treasury published a discussion paper for public comment, one entitled ?Reducing greenhouse gas emissions: The carbon tax option?. Irrespective of how the tax is finally implemented, it will result in an increase of production costs in affected industries. This paper focuses on the characteristics of a furnace-off-gas cleaning system for closed ferroalloy smelters, characteristics that meet the requirements of both reducing solid-matter emissions and operating a safe and reliable gas plant.

Jan 1, 2011