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By K. M. Godiwalla, S. Ranganathan

The thermal state in submerged-arc furnaces (S.A.F.) producing ferro alloys is important for the conditions of both the grade of alloy produced as well as specific energy consumption. The temperature profile in the S.A.F. is affected by the endothermic chemical reactions and the rate of gas evolution. The gas evolution commences at about 900 C due to the reduction of iron in the ore. A first-principle-based 2-D model has been developed to predict the temperature profile in the furnace. In this study, four ores of different grades have been considered in order to simulate the thermal profile in the S.A.F. The influence of the composition of the ore on the thermal profile and its significance in rationalisation of charge distribution to optimise the process are discussed.

Jan 1, 2007

By P. Rosario

The application of high pressure grinding rolls (HPGR) has been growing in the mining industry for the last 10 to 15 years. The major benefits supporting this trend are better energy efficiency, improved grinding capacity, and higher metal recovery in downstream processes such as heap leaching and flotation. In general there is limited quantitative knowledge on the true benefits of HPGRs relative to SAG mills in comminution, and about which situations one deals with better than the other. This paper will present a structure for comparison of the energy requirements for HPGR versus SAG mill considering complete circuits for comminution of precious and base metals hard ores. The work presented is from the design of four complete circuits based on ore data from two sites.

Jan 1, 2010

By F. Ntuli, T. V. Nyangadzayi

Chromium green is an essential metal with various applications in the paints, construction, electronics, and aerospace industries. The main source of chromium green is the carbo-thermic reduction of chromite ores, however, chromite ores are being heavily depleted on a global scale, hence the need to find alternative or secondary sources for the chromium. In order to meet the global demand for chromium there is a need to implement principles of the sustainable circular economy to keep chromium within the material loop. Ferrochrome slag and stainless steel slags are secondary resources that are potential sources of chromium. In this work, recovery of chromium from ferrochrome slag was investigated. The ferrochrome slag was alkaline leached using sodium hydroxide- sodium hypochlorite solution to reduce the use of potent reagents that have a potential negative environmental impact. The leachate produced by oxidative alkaline leaching of ferrochrome slag contained hexavalent chromium, which was used to recover the extracted chromium through a two-stage process involving reduction and precipitation. Reduction of hexavalent Cr to trivalent Cr was investigated using anhydrous FeSO4 at concentrations of 5 g/L, 10 g/L, and 15 g/L. Precipitation was conducted by dosing the reduced leach solution with 1 M sodium hydroxide at dosages of 5 ml/L, 10 ml/L, and 15 ml/L. The experiments were designed using the Taguchi (L9) orthogonal array and analysed according to the ANOVA, general linear model. The optimized conditions for the reduction step were ferrous sulfate dosage of 5 g/L with a pH of 12, and for the precipitation step, 1 M sodium hydroxide at a dosage of 15 ml/L with a setting time of 90 minutes and pH of 7. Physical changes were observed during the two-step chromium recovery, with solution changing from a yellowish colour to dark green colour indicating completion of the reaction. The chromium recovery was found to be 93.3%.

Dec 11, 2024

By S. E. Olsen, T. Færden, G. Tranell, T. Lindstad, J. Lubetsky

The authors are lead authors for chapter 4.3 ?Emissions from Ferroalloy Production? in ?2006 IPCC Guide-lines for National Greenhouse Gas Inventories, Volume 3?. The paper discusses the methods to calculate and report emissions from the production of ferrosilicon, silicon-metal, ferromanganese, silicomanganese and ferrochromium alloys, as well as the basis for the methods and choice of emission factors. CO2 is the main greenhouse gas emission from ferroalloy production, accounting for about 95 % of the total CO2-equivalents. The most accurate method of determining emissions is to base the calculations on reported amounts and analyses of reducing agents and carbonate ores used in the process. If analyses are not available, typical CO2 emission factors for the different reducing agents are recommended. If neither reliable amounts nor analyses of all reducing agents are known, default generic CO2 emission factors for the type of ferroalloy multiplied with amount produced, can be used. The CO2 produced from bio-carbon (charcoal and wood chips) should be reported but will not be accounted for in national emissions. If any bio-carbon is used, the default generic CO2 emission factors cannot be applied. CH4 accounts for less than 1 % of the total emission of CO2-equivalents. Default emissions factors for CH4 are given for the production in open or semi-closed furnaces of silicon-metal and ferrosilicon. In the production of FeMn, SiMn and FeCr in closed furnaces the gas containing CO,CO2 and volatiles can be combusted in boilers and N2O may be formed. While reporting is not required, IPCC Guidelines recommend that the N2O-content in the off-gas is measured.

Jan 1, 2007

By T. C. Alex, K. M. Godiwalla, R. K. Jana

Manganese nodule, available in ocean beds, is a potential resource of the future for copper, nickel and cobalt. Recovering only these metals, containing less than 3% by weight, will result in the generation of large amount of residue. In addition to the material losses, several environmental and ecological problems arise out of this. The present study has been aimed at reducing the environmental and ecological problems associated with massive generation of this residue together with utilization of the resources. Presence of ~ 20% manganese and ~16% silicon in the residue has prompted us to check its suitability as a raw material for silicomanganese production. Lower manganese content and lower Mn/Fe ratio of the residue than that required for silicomanganese production has been corrected in this study by suitable blending. The efficacy of blending and its thermodynamic aspects using FACTSAGE software are discussed. The studies conducted indicate viability of bulk utilisation of the residue through silicomanganese production and thereby reducing the burden on environment to a great extent.

Jan 1, 2007

By A. M. Ghodgaonkar, P. J. Bhonde, R. D. Angal

Primarily ferrochrome is used to introduce chromium into steels and alloys. Chromium enhances hardness, hardenability, corrosion, abrasion and wear resistance of the steel. High carbon ferrochrome is one the cheapest sources of chromium, which finds large consumption in foundries and steel plants. However, carbon leads to problems viz. weld decay and sensitization of steels at elevated temperature causing catastrophic failure. Thus high carbon ferrochrome which otherwise enjoys financial edge over its low carbon grade is not suitable for final alloying or adjustment of chromium content. Subsequently, its addition burdens a steel maker. Hence, metallurgists around the globe have researched on finding out suitable technique for refining of ferrochrome. Traditional production methods of low carbon ferrochrome have drawbacks i.e. high refractory consumption, losses of chromium in slag and fumes etc-. Later these were overcome by adopting relatively new methods namely, metallothermic reduction, triplex process, vacuum technique to directly produce extra low carbon ferrochrome. Authors have carried SWOT analysis of the aforementioned techniques in the literature. Key Words: Ferrochrome, carbon content, low carbon grade, chromite, sensitization

Jan 1, 2007

By Dolly Chakraborty, S. Ranganathan, S. N. Sinha

Experiments were conducted to study the influence of temperature, particle size and ore/coke ratio on the kinetics of reduction. The rate of reduction increased with temperature. The reduction of iron was completed at shorter time intervals at temperature above 1000ºC. Usually the reduction of chromium commenced after the reduction of iron was almost complete. Reduction was controlled by diffusion at low temperatures and by chemical reaction at higher temperatures. The nature of the reducing agent had a very significant influence on the rate of reduction. The study showed that chromium was converted into the carbide during reduction. Increasing the size of the reducing agent increased the rate of reduction initially. After a critical size, the rate of reduction decreased. However, increasing the size of the ore particle decreased the rate of reduction, initially. Beyond a critical size, it increased. An optimum particle size of the chromite ore and that of coke must be chosen, particularly in the production of agglomerates to achieve maximum degree of reduction.

Jan 1, 2007

By M. Kuchta, A. Newman

LKAB’s Kiruna Mine, located above the Arctic Circle in northern Sweden, is the second-largest underground mine in the world today. The orebody is a world-class high-grade magnetite deposit, from which three raw ore products are extracted. We use mixed integer programming to determine a production schedule, i.e., which production blocks to mine, and when to start mining them, so as to minimize deviation from planned production quantities while adhering to the operational constraints of the mine. The resulting model contains thousands of binary variables and a commensurate number of constraints, precluding us from obtaining a schedule in a reasonable amount of time. We describe a method that builds on prior, related work, to expedite solution time. Keywords: underground mining, production planning, optimization, integer programming

Jan 1, 2003

By Rajib K. Mohapatra, K. Vizaya Kumar

In any manufacturing organization internal logistics plays a vital role in improving and maintaining the productivity. In Ferro Alloys manufacturing organization where there is huge input of raw material in terms of ore, reductants and variety of fluxes amounting to about four times of the mass of alloy produced need to be handled from yard to furnaces , internal logistics requires utmost attention. Any deviation or mismatch between stock and requirement will affect furnace operation. Though the activities are being outsourced by most of the organization, these require close monitoring. This communication presents an optimization model which can work as a ready reference for the manager to decide upon the material quantity and the furnace to be fed with an objective of minimizing the cost of handling and zero production loss.

Jan 1, 2007

By K. Sugawara, H. -S. Jeong, Y. Ishiguro, J. Otani, Y. Obara, A. Hirata

A series of measurements of induced stress by the Compact Conical-ended Borehole Overcoring (CCBO) technique was performed within rock mass around a tunnel excavated in a region that an underground powerhouse is constructed under high initial rock stress. In the measurements, a phenomenon of core disking was observed during overcoring. The selecting method of strain data uninfluenced by the core disking was proposed, using X-ray CT scanner. Then, the state of induced stress determined from the selected strain data was discussed, comparing with the state of initial stress. Eine Serie von Messungen von induzierter Belastung mit kompaktem konisch-beendetem Überbohrverfahren (CCBO) wurde in Felsmassen um einen Tunnel ausgeführt, der in einer Region gebohrt wurde wo ein unterirdisches Kraftwert unter hoher anfänglicher Felsbelastung gebaut wird. Bei den Messungen wurde beim Überbohrverfahren ein Phänomen des Core Disking beobachtet. Die gewählte Methode der Belastungsdaten, unbeeinflusst durch Core Disking wurde vorgeschlagen, unter Verwendung von Röntgen-CT-Scanner. Dann wurde der Zustand der induzierten Belastung aus den gewählten Belastungsdaten diskutiert, unter Vergleich mit der ursprünglichen Belastung. Une série de mesures de contrainte induite effectuée avec la technique de forage de sur-carottage compacte à embout conique a été exécutée dans la masse rocheuse autour d'un tunnel excavé dans une région de construction d'une centrale électrique souterraine sous haute contrainte de roche initiale. Au cours des mesures, un phénomène de discage de carotte a été observé pendant le sur-carottage. La méthode de sélection des données de contrainte non influencée par le discage de carotte a été proposée, en utilisant un scanneur de tomographie calculée aux rayons X. Il s'ensuit que l'état de contrainte induite provoquée et déterminé à partir des données de la contrainte sélectionnées a été traitée, en effectuant une comparaison avec l'état de contrainte initiale.

Jan 1, 2003

By T. J. Goff, G. M. Denton

Mintek has developed the EnviroplasTM process for the treatment of solid wastes from the metallurgical industry, especially steel plant dusts, without requiring agglomeration to produce inert slag and at the same time recover metal values such as nickel, chromium and zinc. The products that are generated in the plasma-arc process are usually a metal and a non-toxic slag, which are tapped from the furnace in liquid form. The metal is mainly composed of chromium, nickel and manganese. During the production of stainless steel between 30 and 70 kg of dust and fine waste is generated per ton of steel. Mintek has successfully processed around 1000t of AOD/EAF dust on a toll treatment basis in order to recover the contained Cr and Ni. The metal produced contained 18.5 per cent Cr, and 5.5 per cent Ni. All slag samples tested conformed to US EPA regulations for disposal. The chromium and nickel recovery to metal was 90 and 98 per cent respectively, on a once through basis i.e. no baghouse dust recycle. Slag tapping temperatures varied between 1650°C and 1750°C. The average actual energy requirement excluding furnace heatlosses of smelting steel plant dust with anthracite as reductant was 1.36MWh/ ton of dust. The total mass of feed reporting to the off-gas stream was 10 per cent. The average ZnO content of the fume was 35.5 per cent.

Jan 1, 2004

By M. du Plessis

This paper describes the evaluation of a limit equilibrium model to simulate the behaviour of crush pillars in platinum mines. An analytical model was derived to calculate the residual average pillar stress (APS) values of the crush pillars. The values predicted by this model were compared to the numerical values obtained from TEXAN simulations. In general, the limit equilibrium model appears to be very attractive for simulating pillar failure as the gradual crushing of the outside of the pillar and the transfer of stress to the intact core can be replicated. The value of the TEXAN crush pillar model was further demonstrated by simulating an idealized layout with crush pillars between two adjacent panels. The simulations illustrated that oversized pillars will not crush close to the face and this may lead to seismic failure in the back area. An important finding of the study is that closure measurements may prove to be a very valuable diagnostic measure in crush pillars layouts. Distinct differences in magnitudes of closure were simulated for a scenario where the pillars crush as expected, compared to the scenario where an oversized pillar is left. Experimental closure data collected in a crush pillar stope provided further evidence regarding the value of closure measurements in these layouts.

Jan 1, 2011

By G. S. Maré

Tin plating operations are of a complex nature due to the many operational variables that need to be controlled in order to create a product of required quality. The work in this report lays the basics for the control of a halogen plating operation based on the DuPont tinplating set-up with regard to the chemical make-up of the plating solution, as well as operational variables such as temperature and current density. To evaluate these aspects of the process, a rotating cathode Hull-cell set-up was used. This allowed for a laboratory scale plating arrangement that simulates industry closely with regard to chemical and hydro-dynamic considerations. Typical industry accepted standards were obtained for the values of operational variables and a ?baseline? test was conducted employing these standards. All subsequent tests conducted were benchmarked against this baseline result. A large suite of results was obtained in which it was found that changes could be made to the industry accepted norm which would improve on the stability of the operation and therefore the quality of the final tin-plated product. Examples of these results are: an increase in stannous tin concentration, an increase in sodium chloride concentration and a slightly elevated plating temperature. In addition, conditions were found that must be avoided to prevent instability and poor product quality.

Jan 1, 2010

Current mine production planning, scheduling, and allocation of resources are based on mathematical programming models. In practice, the optimized solution cannot be attained without examining all possible combinations and permutations of the extraction sequence. Operations research methods have limited applications in large-scale surface mining operations because the number of variables becomes too large. The primary objective of this study is to develop and implement a hybrid simulation framework for the open pit scheduling problem. The paper investigates the dynamics of open pit geometry and the subsequent material movement as a continuous system described by time-dependent differential equations. The continuous open pit simulator (COPS) implemented in MATLAB, based on modified elliptical frustum is used to model the evolution of open pit geometry in time and space. Discrete open pit simulator (DOPS) mimics the periodic expansion of the open pit layouts. Function approximation of the discrete simulated push-backs provides the means to convert the set of partial differential equations (PDEs), capturing the dynamics of open pit layouts, to a system of ordinary differential equations (ODEs). Numerical integration with the Runge-Kutta scheme yields the trajectory of the pit geometry over time with the respective volume of materials and the net present value (NPV) of the mining operation. A case study of an iron ore mine with 114 000 blocks was carried out to verify and validate the model. The optimized pit limit was designed using Lerchs-Grossman?s algorithm. The best-case annual schedule, generated by the shells node in Whittle Four-X yielded an NPV of $449 million over a 21-year mine life at a discount rate of 10% per annum. DOPS best scenario out of 2 500 simulation iterations resulted in an NPV of $443 million and COPS yielded an NPV of $440 million over the same time span. The hybrid simulation model is the basis for future research using reinforcement learning based on goal-directed intelligent agents.

Jan 1, 2008

By J. Kempken, R. Degel, J. Kunze, R. König

The FeNi technology is currently dominated by high-power submerged arc furnaces, often designed as smelter as "two-inline-solution". To achieve the intended high efficiency, state-of-the-art design in good correlation with ores and reductants and an integrated layout of the whole plant is of great importance. An introduction will be given to general aspects in the production FeNi, plus a detailed overview of design principles for large FeNi smelters and finally some examples of innovations and research projects concerning Fe-Ni.

Jan 1, 2007

By M. du Toit

Cromanite?is a new high-strength austenitic stainless steel developed by Columbus Stainless. It contains approximately 19 percent chromium, 10 per cent manganese and 0,5 per cent nitrogen. Cromanite can be welded successfully, but due to the high nitrogen content of the base metal, certain precautions have to be taken to ensure sound welds with the desired combination of properties. Although no matching filler metals are currently available, Cromanite can be welded using a range of commercially available stainless steel welding consumables. Welds produced using E309L, E307, E307Si and E312 filler wires are resistant to hot cracking and the formation of nitrogen-induced porosity, but the hardness, strength, ductility and toughness of the welds are generally inferior to those of the base metal. In applications where full use is made of Cromanite?s high strength, welds with matching strength levels would be required. In wear applications, where Cromanite is used primarily for its work-hardening properties and corrosion resistance, lower strength welds would probably be acceptable. Welds produced using E307 filler metal demonstrate the best combination of properties for use in wear applications. The welds display high rates of work-hardening that would result in increases in hardness and strength when subjected to abrasive or high impact environments.

Jan 1, 1999

By L. Robles-Stefoni

"Multiple-point simulation (MPS) methods have been developed over the last decade as a means of reproducing complex geological patterns while generating stochastic simulations. Some geological spatial configurations are complex, such as the spatial geometries and patterns of diamondbearing kimberlite pipes and their internal facies controlling diamond quality and distribution.Two MPS methods were tested for modelling the geology of a diamond pipe located at the Ekati mine, NT, Canada. These are the single normal equation simulation algorithm SNESIM, which captures different patterns from a training image (TI), and the filter simulation algorithm FILTERSIM, which classifies the patterns founded on the TI. Both methods were tested in the stochastic simulation of a four-category geology model: crater, diatreme, xenoliths, and host rock. Soft information about the location of host rock was also used. The validation of the simulation results shows a reasonable reproduction of the geometry and data proportions for all geological units considered; the validation of spatial statistics, however, shows that although simulated realizations from both methods reasonably reproduce the fourth-order spatial statistics of the TI, they do not reproduce well the same spatial statistics of the available data (when this differs from the TI). An interesting observation is that SNESIM better imitated the shape of the pipe, while FILTERSIM yielded a better reproduction of the xenolith bodies. IntroductionThe simulation of geological units poses several technical problems that challenge the capabilities of available geostatistical simulation approaches and their ability to deal with spatial complexity of categorical variables. The spatial geometry of diamondbearing pipes and their internal facies controlling diamond distributions are a specific and well-known difficult modelling problem. The geometry of a kimberlite pipe is typically like an inverted cone (Figure 1); the wider part is known as the crater and is located near the surface, and the narrower, deeper part is known as the diatreme. Xenolith bodies can also be found inside the pipe. A very important contribution to the geological modelling of the contours of the pipe is the measure of uncertainty about the location of the contact between the kimberlite pipe and the host rock."

Jan 1, 2016

By Stafford McKnight, Larissa Koroznikova, Steve Hall, Cameron Klutke

This paper outlines a simple methodology for mineral characterisation, developed as part of the Australian Mineral Industry Research Association (AMIRA) managed research project P777 ?The Development of Heavy Suspension Techniques for High Density Separations (Replacement of Clerici?s Solution)?. The project was sponsored by De Beers, Rio Tinto and Iluka Resources. Heavy mineral characterisation of samples arising from exploration, mining or metallurgical processes is frequently conducted using laboratory heavy liquid analysis. Unfortunately, there are only a limited number of high density (?heavy?) liquids and these tend to be more toxic as their density increases. Low-toxicity inorganic solutions, based on tungsten compounds, have been developed that can be utilised at relative densities (RD) up to 3.0. Beyond this value organic liquids can be used, however this presents significant health and safety hazards. Diiodomethane (methylene iodide) having a relative density of 3.31 is commonly used. Mixtures of thallium formate and thallium malonate were found in the early 1900?s by Clerici to provide liquids having specific gravities between 4.0 and 5.0. For the characterisation of the heavy components of mineral sand deposits (e.g. anatase RD 3.9, rutile RD 4.2, ilmenite RD 4.4 ? 4.7 and zircon RD 4.6 ? 4.8) there is currently no heavy liquid alternative to Clerici?s solution. Clerici?s solution is highly toxic and testing is now conducted by few laboratories worldwide with costs reflecting the chemical costs, infrastructure costs and health and safety regimes (e.g. blood testing of exposed staff). A simple laboratory technique of density fractionation has been developed, employing suspensions of fine tungsten carbide particles in lithium heteropolytungstates solutions, that can replace Clerici?s solution in the evaluation of fine mineral sands samples (e.g. -250 +150 microns). The developing methodology that can achieve low-cost, low toxic separations at relative densities above 4.0 is outlined and the comparison of results with Clerici?s solution presented. In addition, preliminary work on density fractionation of zircon samples is presented. Zircon fractionation relates to their inclusion, radionuclide content and metamictization.

Jan 1, 2007

By E. Kapilashrami, S. Seetharaman

Refractory/metal interactions and associated reactions are significant during casting as they can lead to inclusion formation. High-temperature interactions between aluminosilicate refractories and molten steel were studied in the present investigation using the sessile drop method. The changes in the contact angles between molten iron with well-defined oxygen levels and substrates of silica, mullite (3Al2O3?2SiO2) as well as commercial refractories were measured in the dynamic mode. In all cases, the reaction led to slag formation. The experiments were performed under isothermal conditions at 1823 and 1873 K. A known and constant oxygen partial pressure was imposed above the iron drop, through appropriate CO-CO2-Ar mixtures. For all substrates, the contact angles started decreasing due to the lowering of the surface tension of iron, as oxygen was imposed on to the system. When a critical level of oxygen was reached, slag started forming at the drop/substrate interface and at this stage, the contact angle dropped suddenly. Subsequent behaviour of silica and mullite was observed to be different, with SiO2showing a non-wetting behaviour. In the case of SiO2substrate, there were also deep erosions along the periphery of the drops and there was slag accumulation at the sides of the metal drop, probably due to Marangoni flow and/or SiO(g) formation. SEM and EDS analysis of the substrates revealed that the formed slag was fayalite. The thermodynamic criteria for slag formation and possible mechanisms of the reaction are discussed in the light of the experiments. Key words: silica, mullite, fayalite, corundum, slag formation, sessile drop.

Jan 1, 2004

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