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By S. Sun

The equilibrium distribution of Cu, Fe and Ni between Cu-Ni-Fe mattes and Pt alloy was measured as functions of the sulphur partial pressure (pS2), oxygen partial pressure (pO2),temperature and Fe content of the matte. The distribution ratios of Cu, Fe and Ni between matte and alloy were independent of oxygen pressure when the pS2was fixed at 2.5x10-5atm and pO2was varied between 10-15and 10-12atm. The distribution ratio of Cu, Fe and Ni increased as the sulphur partial pressure increased. The Cu and Ni distribution ratios decreased with increasing temperature and the Fe distribution ratio increased slightly over the temperature range of1350?1500°C. For mattes where the proportions of Cu and Ni were kept constant, the distribution ratio of Cu increased as the Fe content in the matte increased. The Fe and Ni distribution appeared to be independent of the iron content in the matte and had a value of 1.2 and 1.6 respectively. The activity of Cu, Fe, Ni in the matte was calculated using a regular solution model for solid Pt-Fe-Ni-Cu alloy. The activity coefficient of Cu, Fe and Ni decreased as pO2and pS2increased.The activity coefficients also appeared to be independent of the Fe content and temperature over the range of 36 to 54 wt% iron and 1350 to 1500°C respectively. Keywords: activity, alloy, matte, thermodynamics

Jan 1, 2004

By M. Tangstad, H. Brun, P. Calvert, A. G. Lindseth

In 1999, Eramet bought the ferromanganese plants in Porsgrunn and Sauda (Norway) and Marietta (USA). With an ownership in the Comilog mine, the plants will operate with a high amount of Comilog ore. The properties of Comilog ore are reviewed and compared to a number of industrial operations. Important ore properties are chemical and mineralogical analyses, CO reactivity and mechanical strength. The advantage of Comilog ore is its contribution to lower energy and coke consumption. However, special precautions must be taken regarding the amount of fines and water introduced in the furnace, as Comilog ore is more porous compared to other Mn ores.

Jan 1, 2004

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 TiO2is reduced to Ti2O3.One of the striking features of these reactions is a consistent relationship between the extents of FeO and TiO2reduction; 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-Ti2O3phase 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 R. T. Jones

Slags have been produced as by-products from pyrometallurgical processes for thousands of years, and have generally been regarded as waste. Many of these slags are no longer seen as residues merely to be discarded, but as potential economic sources of metals, or as useful by-products in their own right. Slag cleaning can enhance the recovery of valuable metals in existing pyrometallurgical processes, or can produce economic value from recycling old slag dumps. For example, a process has been developed and implemented industrially for recovering cobalt from copper smelting slag in a DC arc furnace. The relatively non-leachable behaviour of glassy slags allows them to be used as a very safe means of disposal of metallurgical waste streams, including many that are classified as hazardous. The high temperatures, reducing conditions, and good mixing that can be achieved in a DC arc furnace enable the effective functioning of this environmentally beneficial means of disposal. Lead blast furnace slag can be rendered safe for disposal by treating it using the Enviroplas process, which strips most of the hazardous lead from the slag (and traps the rest in an insoluble glassy slag) and recovers economic quantities of zinc by absorbing (in a lead splash condenser)the zinc vapour that is fumed off in the furnace. Another example can be seen in the recovery of a chromium- and nickel-containing alloy from stainless steel plant dust, while producing a disposable residual slag. The examples presented here illustrate that it is possible to develop processes that are both economic and environmentally beneficial. Keywords: DC arc furnace, plasma, slag cleaning, cobalt recovery, zinc fuming, Enviroplas, jigging, re-melting fines, environmental, economic

Jan 1, 2004

By A. Mainza

It is common practice in the mineral processing industry to use hydrocyclones for particle classification. However, classification in the UG2 platinum circuits using the hydrocyclone poses major challenges due to the differences in density between silica and chromite, the two major components of this ore. Silica, the PGM carrying component, has an average density of 2.7 and the barren chromite component has an average density of 4.5. When conventional and flat bottom cyclones are used there is a misplacement of particles due to differences in density leading to inefficiencies in the classification by size. As a result of the density effect, coarse silica reports to the overflow, resulting in loss of recovery, and fine chromite reports to the underflow, resulting in loss of milling capacity and unnecessary production of fine chromite. A classifier based on a different concept was required in the classification of UG2 platinum ore. The three-product cyclone, which is a hydrocyclone with two concentric vortex finders to produce three distinct products, has been tested in the UG2 ore application and indications are that misplacement of particles due to differences in the component densities can be minimized through the use of this unit. Industrial and pilot plant trials were conducted and indications are that the three-product cyclone can be installed to selectively produce a middlings stream that can be screened using Pansep screens to provide a screen oversize, which is predominantly coarse silica that can be preferentially reground to recover the PGM values contained in the coarse silica.

Jan 1, 2005

By C. E. Doran

Since the early 1990s the underground mining industry has embarked on a vigorous program of improving process and eliminating costs. A leading development in this program has been the implementation of leaky feeder radio systems as an enabling infrastructure for future automation. El-Equip Inc. has led this development with more than 175 mines implementing mine-wide radio infrastructures for voice and data. In this paper, we describe the implementation of a digital radio network which supports existing installations through to an automation infrastructure employing full digital cellular communications with mobile video roaming capabilities. We outline the evolutionary path from existing low speed data communications links through to 155 Mbps and beyond.

Sep 1, 2001

Scenario reduction is designed for selecting a representative subset of geostatistical simulations out of a much larger set. Three steps are involved: measuring the dissimilarity between two simulations; finding a metric to measure the distance between any subset of k simulations and the full set of N simulations; and finding an efficient algorithm for selecting the subset that minimizes the metric. This paper focuses on the third question. We show that genetic algorithms are an efficient way of approaching the minimum when the population of subsets to be sampled is large. Two case studies based on the Walker Lake data-set are presented: firstly choosing k=4 simulations out of a total of 100, and secondly choosing 20 out of the same 100 simulations. In the first case it was possible to compute all possible combinations exhaustively and hence to demonstrate that the algorithm converges to the true minimum. This was not possible in the second case. Instead we demonstrate that it outperforms the random draw algorithm used in earlier work. A procedure for tracking individual selections during the iterative procedure was developed. This allows us to measure the evolution in the percentage of progeny resulting from crossing-over and from mutation that survived in the next generation. It gives valuable insight into how to choose the parameter values in the algorithm. Another key finding is that there is a trade-off between the number of individuals per generation and the number of generations required for the algorithm to converge.

Jan 1, 2014

By K. M. Li, Y. D. Zhang

The selection of stripping dragline is a complicated problem. Several factors, such as the deposit buried conditions, the demand of mine production rate, cast blasting result, the mining/stripping operation method and parameters, etc. may comprehensively influence the optimal selection of technical specifications of the dragline. Under these circumstances, the basic thinking and procedures for dragline selection are put forward as follows. •Step 1—Initially estimate the dragline annual stripping rate and stripping bench height according to the annual coal production rate and advancing speed of mining front. Then the feasible alternatives of dragline sizes can be calculated and selected from the existing dragline series. •Step 2—A computer simulation model is developed to simulate the dragline stripping operation, to obtain a series of working face parameters, then to select the best dragline alternative. This step can be interactively iterated until the satisfactory results are obtained. •Step 3— Sensitivity analysis can be done with the systems simulation model by changing the stripping bench parameters, e.g. stripping bench height and cut width, etc. to verify and modify the selection results if necessary. The mathematical model for dragline stripping simulation has been set up. The flowchart of the model is shown. A case study for a large surface coal mine with annual production rate of 16 Mt/a is followed. The dragline bucket capacity and operation radius, stripping bench height and cut width as well as other parameters are comprehensively optimized and selected. Keywords: Open cast, dragline, specification, selection, cast blasting

Jan 1, 2003

By M J. Van Der Merwe

The mining industry is facing a serious skills resource shortage, growing commodity demand and cyclical prices. This makes focus and allocation of resources in the early stages of project development very important. To assist with these six key elements in the project prioritization process is proposed, namely: 1) Define the project vision, objectives and business case, 2) Determine the potential show stoppers, 3) Determine the key value drivers, 4) Track changes and provide regular feedback, 5) Evaluate the alternatives and, 6) Ensure proper gate management governance at the decision point. Incorporating these elements in the project development process will assist in resource allocation and focus on the high value aspects of projects and alternatives during the early stages of the project development lifecycle. Keywords: Resource allocation and focus, vision, show stoppers, value drivers, project prioritization, linear programming, business case modelling, management decision.

Jan 1, 2008

By S. Erçayhan, B. Derin, O. Yücel

In the present study, the production of low carbon ferrochromium (LC-FeCr) from chromite concentrates containing 55.09% Cr2O3 and 13.06% Fe via metallothermic process was investigated. For this aim, in the experiments, the aluminothermic reduction method was applied in an open crucible. 10% CrO3 + 10% NaClO3, 15% CrO3 + 5% NaClO3 and 20% CrO3 by weight of concentrate were added to the charge, respectively and the charge was reduced with aluminium. The experiments were done with the additions of 90, 100, 110, 120 and 130% of stoichiometric requirement of aluminium. The highest Cr content in alloys was found as 71.7% at 120% of stoichiometric Al whereas the highest Cr recovery in alloys was found as 71.8% at 130% of stoichiometric Al when the both charge contained 15% CrO3 + 5% NaClO3 by weight of chromite concentrate.

Jan 1, 2004

By R. C. D. Phillis

Conventional stoping in hard rock mining is largely considered an operational environment. This paper suggests that stoping falls within the realm of a project management environment typified by uncertainty, variation, and large numbers of interdependencies. Stoping was then equated to a micro-project with many simultaneous activities that had to be executed accurately using finite resources within limited shift durations in order to reach specific goals. Critical chain project management (CCPM) principles were applied to the stoping activities, and the results showed that the number of blasts per panel can be significantly increased by successfully moving the distribution of work as close as possible to the start of shift. Critical chain principles also assisted in facilitating re-focusing and teamwork among stoping crews as well as between day- and night-shift crews. The main recorded success was in managing inherent protective capacities/local contingencies/fat/buffers that are found in all projects. The impact on mine health and safety (MHS) was significant as individual operators and crews became convinced that they could perform all stoping tasks (activities) without compromising accuracy or speed.

Jan 1, 2011

By J. C. van Dyk

The objectives of this study were firstly to characterize and quantify the inorganic material in the Secunda gasification feedstock. Secondly, the effect of washing on coal properties and sulphur content was investigated. Coal from a single source and a coal blend from 6 different mines were tested. Composite samples were visually sorted by a geologist in the groups containing roof, floor, C-shale, pyrite, carbonates and siltstone material. Inorganic mineral types from the single source and coal blends were characterized separately. Characterization results indicate that the average mineral matter distribution (mass %) of the coal tested was as follows: carbonates (6%), carbon-shale (19%), pyrite (12%), roof (18%), floor (46%) and siltstone (22%). The roof, floor, pyrite, carbon-shale, carbonates and siltstone in the single source and coal blend have similar chemical properties and characteristics, except for the ash melting temperatures of pyrite and kaolinite in the siltstone. By implementing selective mining and increasing mining management practices, the percentage discard in the run of mine coal can be significantly reduced, by up to 45%, if the mining of roof and floor material can be avoided. No significant impact of mining practices on sulphur content is expected in this case due to the low concentrations of sulphur in the roof and floor material. In summary, selective mining practices will probably result in almost45% decrease in the discard content in the run of mine to gasification, an increase in the carbon content from 55.0% to 58% (air dry basis) and a decrease in sulphur content from 1.1% to 0.9% (air dry basis). It is clear from this study that the main source of sulphur is not in the high ash-content mineral types (e.g. floor and roof), but in situ in the coal structure. Keywords: inorganic material, effect of washing, roof, floor, pyrite, C-shale, carbonates and siltstone

Jan 1, 2005

The functional design of a pavement relates to the selection of appropriate wearing course materials which optimise the trafficability of a pavement. Trafficability is dictated to a large degree by the choice, application and maintenance of locally available wearing course materials. Poor functional performance results in decreased safety and operational efficiency and increasing road and vehicle maintenance requirements. An optimal functional design will include a certain amount and frequency of maintenance (watering, grading etc.) and thus maintenance itself can be planned, scheduled and optimized within the limits of required road performance and minimum vehicle operating and road maintenance costs. Since no wearing course material selection guidelines, tailored to the specific needs of surface mines, were available, there was the need to identify appropriate selection guidelines for the range of materials commonly encountered for road building on South African mines. The aim of this paper is to present an overview of the functional design method for mine haul roads and, through an analysis and quantification of existing wearing course material performance, to recommend appropriate wearing course material selection guidelines. The functional design technique has been applied at a number of mines and is illustrated by an application case study which demonstrates the potential reduction in total transportation operating costs associated with the optimal functional design.

Jan 1, 2000

By J. P. D. Strydom

The transmission of excessive vibration to the human body can cause physical stress that may result in crippling pain or permanent disability. Rock drills are known to transmit high levels of vibration that are difficult to attenuate through conventional approaches to vibration isolation. However, it can be shown that once the ISO frequency weighting has been applied, most of the vibratory effect of the rock drill?s motion is concentrated at the drill?s operating frequency. This observation opens the way for utilizing a concept known as vibration absorption, aimed at attenuating the rock drill?s vibration. In essence this entails using the inertia of a secondary vibratory system to counteract the motion of the handle. This article documents an investigation into the use of such an absorber for attenuating rock drill vibration and demonstrates the feasibility of such an approach. A mathematical model of such an absorbing handle was developed and used for design studies. Based on these investigations an experimental prototype model was manufactured and tested. A significant reduction in vibration levels could be achieved.

Jan 1, 2002

By J. N. Van der Merwe

The principal goal of the research described in the paper was to determine, by measurement of pillar scaling on pillars that have not failed, whether the pillar life prediction method developed by van der Merwe (2003) was valid as it stood or whether adjustments were necessary to the rates indirectly derived from observation of failed pillars. To this end, measurements were taken on over 350 pillars at 13sites on 6 mines. The project was done as a collaborative effort between the University of Pretoria, the Nancy School of Mines and CSIR Miningtek. During the course of the investigation, it was found that the majority of pillars display maximum scaling at mid height, that there was no clear preferential direction of pillar scaling, and that pillar corners do not scale significantly more than the mid pillar areas. The most important conclusion was that the scaling rates found by measurement agreed with the inferred rates found in the previous work. The previously developed procedure for the prediction of pillar life spans consequently requires no adjustment, although the error span is in the region of 20%. It is recommended to do further research into the effect of sealing of panels and, possible chemical changes taking place in the pillars as they age on the scaling rate.

Jan 1, 2004

By A. Andrews

Paper written on project work carried out in partial fulfilment of MSc (Eng) degree Solid state sintered silicon carbide ceramics are used in aggressive environments as sealings. There exist data concerning corrosion, but there are only few data concerning their electrocorrosion behaviour. Therefore the electrochemical corrosion of solid state sintered silicon carbide (SSiC) ceramics has been studied at room temperature in acidic and alkaline environments by using potentiodynamic polarization measurements. The investigation showed a pronounced electrochemical corrosion in bases and acids. In HCl andHNO3pseudo-passivity features due to the formation of a thin layer of SiO2on the surface were observed, whereas in NaOH soluble silicate ions were observed, resulting in more pronounced corrosion. The microstructural observations of initial and corroded samples reveal that the residual carbon found in the microstructure do not dissolve preferentially. Keywords: Corrosion; SEM; SSiC; polarization test.

Jan 1, 2006

By S. S. Makgato

In this study, coke oven tar additions over a range of 0?8 wt.% were evaluated as a possible substitute for imported coal fractions. The coke oven tar used was collected from tar decanters in the byproducts section of the coking plant. The moisture content in the tar varied depending on the residence time and water carryover from the coke oven tar separators to the storage tanks. Moisture contents of 1 wt.%, 3 wt.%, and 6 wt.% were investigated in order to evaluate the effect on coal blend, carbonization, and coke properties. At 6 wt.% moisture content with 6 wt.% coke oven tar, although the coke quality improved the yield showed a 4% decrease. On the other hand, 1 wt.% moisture content with coke oven tar of 6 wt.%, increased the yield by 1% and the coke quality improved. However, the latter process was characterized by an excessive increase in wall pressure and pushing energy, both of which are detrimental to the oven walls. The optimum moisture content in coke oven tar was found to be 3 wt.% with a coke oven tar addition of 6 wt.% in the coal blend. With these conditions, the coke properties improved and wall pressure and pushing energy were acceptable. However, a decrease in coke yield of up to 2% was observed. Despite this, coke oven tar addition is considered to be a viable option based upon economic factors of a reduction in the quantity and cost of imported coking coals that is required to achieve the same optimum final coke product. Keywords coal substitution, coke oven tar, tar moisture, coal blend, coke, coke quality.

Nov 1, 2013

By F. Dehghani

The influence of different grinding methods on the shape characteristics of magnetite particles was investigated. Also, the effect of particle shape on the flotation of the magnetite, both alone and in the presence of quartz particles, was investigated. The shape characteristics of the magnetite particles were measured and calculated from images obtained by scanning electron microscopy via an image analysis system. The flotation tests were performed using a laboratory flotation cell. Results showed that in the -250+212 µm and -106+75 µm size fractions, ball mill products have a higher elongation value than rod mill products, while in the -150+125 µm size fraction, rod mill products have a higher elongation value. Particles with higher elongation values and lower roundness values have a higher flotation kinetic constant. Furthermore, the influence of magnetite particle shape on flotation is greater, and the flotation kinetic constant is higher, in the presence of quartz particles than in the flotation of magnetite alone Keywords shape, elongation value, flotation kinetics, magnetite.

Dec 1, 2013

By M. Jele

? Sulphuric acid plant in umbogintwini. ? Double absorption plant, capacity of 550MTPD. ? Build by simon curve during the year 1973. ? Side stream plants such as: ? Liquid SO2 Plant, ? Liquid SO3 and ? Oleum plant

Jan 1, 2009

By T. A. Muhlare

The use of electrolyte additives to smoothen cathode deposits during copper deposition is practised worldwide. These additives absorb on the cathode surface and take part in the electrochemical crystallization process. However, these additives also affect the quality of the cathodes when they are inadequately controlled. Electrolyte additives used by Palabora are glue, thiourea, Avitone and chloride. Their effects were determined on cathode quality, the size of the current density region that gives the desired compact morphology, and current efficiency. This was done in a small-scale cell. Small cells have different hydrodynamics from industrial-scale cells, which makes it difficult to simulate the operation of industrial cells in a laboratory. The approach used here was to use a rotating cylinder cathode to attain controlled hydrodynamics. The rotation speed was chosen to give a diffusion layer thickness that is similar to that of an industrial-scale cell. It was shown that even fairly small changes in the additive levels can significantly affect the cathode morphology, and the current density range over which this morphology can be obtained. Keywords Copper, electrorefining, glue, thiourea, avitone and chloride.

Jan 1, 2011