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By J. C. Carrasco, M. Sánchez, R. Jara, F. Marquez, F. Parada, R. Parra, J. Palacios

In past years, Chile has been the largest copper producer in the world and for 2002 mining represented country average of 10 % of the GDP, accounting for 47 % of the total exportation. As copper sulphides are the main mining resources in the country, the metal is produced using the classical processes of flotation and pyrometallurgical extraction. Seven copper smelter plants, which extends from the northern Atacama desert to the central part of the country produced1,522,000 metric tons of fine copper in 2002, approximately one half of total copper concentrate production, with a notorious environmental impact due to the great amount of slag produced during these extraction steps. In this work, a global characterization of copper pyrometallurgical slags produced and disposed of in Chile and worldwide is done, and the concept of total project development is considered to explain the scopes of the study, recovering different compounds and generating new activities around mining. The presentation is completed with the proposal of various methods and techniques being developed today in a joint project between smelter plants and the University of Concepción, with the support of the Chilean government and mining companies, addressed to generate new materials from copper slag. Recovery of copper, molybdenum, precious metals, silica and iron, that is the most abundant component of the slag, are the goals for this research. Metals, commercial compounds, alloys and different forms of iron oxides for steel industry are proposed products.

Jan 1, 2004

By Manoj Kumar, S. Ranganathan, S. N. Sinha

The reducibility of three different manganese ores with coke was studied. The three ores were reduced to different extents under the same experimental conditions. The investigations showed that in the temperature range of 900-1000 ×C, Fe2O3 in the ore was reduced to metallic iron. MnO2 was reduced to Mn3O4 in all cases except one in which it was reduced to Mn2O3. The kinetics of reduction was controlled by different mechanisms in the different ores. Temperature had a significant influence on the reducibility of the ores.

Jan 1, 2007

A physical modelling study has been carried out to simulate the slag-metal dispersion induced by a high-strength bottom gas injection. Water and kerosene were utilized to simulate metal and slag respectively. A water model of CLU (Creusot-Loire Uddeholm) vessel was used with three different nozzle orientations, namely, off-centre, triangular off-centre and centre. The gas flow rates changed from 0.00599m3/sec to 0.01081m3/sec. Height of heavy and light phases was kept fixed at 0.23 m and 0.02 m respectively. The dispersed phase holdup was determined at various axial and radial distances, gas flow rates, and tuyere configurations. The observations revealed that at a fixed gas injection rate, as the vertical distance increased in the centerline, straight off-centre orientation resulted in greater dispersed phase hold up values than those of the centre configuration and the triangular off-centre orientation. The dispersed phase holdup was found to increase with gas injection rate and decreased with axial distance. The variation of the dispersed phase hold up with the dimensionless axial distance and the gas injection rate was correlated by using the Modified Froude Number. The experimental values of the dispersed phase holdup were found to be in good agreement with the correlated values obtained from the modelling equations. The findings of the present study may be utilized in the ferroalloy refining vessels in terms of designing tuyere locations for optimum processing conditions.

Jan 1, 2004

By Swapan Ghosh, Amitava Sengupta, Proloy Das

Ferro-alloys are very important ingredients used for making of quality steel with desired composition. In view of high demand in various types of ferro-alloys, it has become necessary to produce the same efficiently, safely and cost-effectively with consistent quality maintaining the anti-pollution norms. To achieve this goal, it is necessary to adopt latest process/equipment with the state-of-the-art instrumentation and automation system. A Programmable Logic Controller (PLC) based automation system with suitable Human Machine Interface(HMI) terminals along with intelligent field mounted sensing/control devices allows to monitor and control the complete plant effectively with optimum deployment of man-power. In association with this, use of process optimization controllers enables to achieve specialised functionalities of the submerged arc furnaces like material management, lining management, electrode management, power management, overall production management etc.

Jan 1, 2007

By G. B. Dukes

Scaling of rockpasses was problematic at Tau Lekoa Mine prior to production commencing in 1991. High horizontal stress levels relative to the host rock mass strength have been instrumental in causing the observed scaling. Scaling has been more pronounced in the deeper rockpasses and these are monitored regularly. Rehabilitation of one of the reef passes and one of the waste passes was required in the period 1999 to 2001. This paper describes the extent of the problems experienced to date as well as the rehabilitation completed.

Jan 1, 2006

By X. Xiang, W. Xia, J. Yin

"TiCl4 slurry containing valuable metals is an unavoidable by-product of the titanium ore chlorination process. The recovery of these valuable metals, which include titanium, niobium, tantalum, and aluminum, is an urgent issue to tackle in the titanium industry. The results of this investigation show that the valuable metallic elements can be recovered from the slurry by evaporation in a sealed container and leaching with dilute hydrochloric acid. After evaporation at 200°C for 60 minutes, nearly 99% of the titanium was recovered in the form of TiCl4, which was formed by the reaction of the TiO2 in the slurry with AlCl3. After evaporation, metals like niobium, aluminum, and tantalum remained in the residue. By leaching with 2.1 mol/L HCl at a L/S ratio of 6:1 mL/g at 80°C for 60 minutes, the soluble metals, such as aluminum, iron, and copper were all removed from the residue, and the niobium and tantalum were further enriched in the leach residue. A concentrate containing 53.40 wt% Nb and 5.57 wt% Ta was obtained by washing the leach residue with dilute aqueous ammonia under stirring. A potential waste water purifying agent containing 263.75 g/L AlCl3 was produced by purifying the leaching solution with Al(OH)3 and modified polyacrylamide. IntrodutionTitanium tetrachloride (TiCl4) is an important intermediate in titanium metallurgy that is widely used in the production of titania and titanium sponge (Akhtar, Xiong, and Pratsinis, 1991). In conventional titanium metallurgical processes, high-titanium materials such as synthetic rutile and high-titanium slag are reacted with chlorine to produce TiCl4 in a fluidized-bed furnace. Accompanying elements, such as Al, Nb, and Fe also react with chlorine to form chlorides, which are mixed with gaseous TiCl4 (Anderson, 1917). In the condensation process, gaseous TiCl4 is refrigerated and high-boiling-point chlorides are precipitated in the liquid TiCl4 to form a slurry containing 50~60 wt% TiCl4 (Wang, Xiang, and Wang, 2012).Various methods have been proposed to recover TiCl4 from the slurry, including microwave heating and spray drying (Wang, Xiang, and Wang, 2012, Wang et al., 2010a). To date, the only way to recover the TiCl4 is to return the slurry to the fluidized-bed furnace. However, this causes fluctuations in the temperature in the furnace, resulting in incomplete reaction between titanium-rich materials and chlorine. Therefore, the slurry is often rinsed with water and neutralized by adding lime, which caused serious environmental pollution and wastes a valuable resource (Roy, Bhatt, and Rajagopal, 2003)."

May 1, 2019

By M. K. Elmouttie, G. V. Poropat

The analysis of structure using joint set statistics is well known. Other data such as the position of discontinuities and the contacts between rock mass units cannot be easily incorporated in simple statistical analysis based on orientation alone. Algorithms to model the structure of rock slopes using measurements of the orientation and position of discontinuities are being developed by CSIRO Exploration and Mining. These algorithms provide a capability to model the structure of a rock slope and estimate the likelihood of the formation of hazardous blocks in existing or proposed rock slopes and identification of the location and size of these blocks. The algorithms provide the basis of structural modelling to identify potential failure mechanisms in rock slopes.

Jan 1, 2006

By Alan Bye, Megan Little

Geology, and the detailed understanding of its properties, are fundamental to the optimal design and successful operation of any mine. To that end extensive fieldwork has been conducted at Anglo Platinum?s PPRust operation to collect geotechnical information both from exploration boreholes and in-pit mining faces. Since 1998, geotechnical data has been collected from over 337 km of exploration core, 7 km of exposed mining faces and more than 15 600 field and laboratory tests, in order to define the complete set of geotechnical properties for each rock type in the mining area. The geotechnical information collected is stored in two databases, SABLE Warehouse and MineMapper3D before it is imported into the Datamine mining software package. The geotechnical parameters, mining rock mass rating system (MRMR), uniaxial compressive strength (UCS), fracture frequency per metre (FF) and rock quality designation (RQD), are modelled using geostatistics to generate a 3D geotechnical block model. Data is interpolated between exploration boreholes and exposed mining faces and modelling is constrained, using wireframes, by rock type and structural features. By having detailed geotechnical information available in a 3D model that can be readily accessed and interpreted, significant production optimisations, feasibility studies and planning initiatives can be implemented. From a slope design perspective the model is used to target data deficient zones and highlight potentially weak rock mass areas. As this can be viewed in 3D, the open pit slopes can then be designed to accommodate the poor quality area before it is excavated. It also follows that geotechnical zones can be readily identified and the slopes optimised accordingly. Rather than viewing the drill and blast department as an isolated cost centre and focussing on minimising drill and blast costs, the fragmentation requirements of the comminution and load and haul business areas are studied. It is well understood that chemical energy is the cheapest form of comminution and that major downstream benefits can be derived by increasing drill and blast expenditure. 238 blasts were assessed to determine the optimum fragmentation requirements for ore and waste. Based on the study a mean fragmentation target of 150 mm was set for delivery to the crushing circuit and a mean fragmentation of 230 mm was set for waste loading from the pit. Substantial benefits have been realised in the drill and blast department by developing empirical correlations that relate the MRMR values in the geotechnical model to a blastability index, fragmentation, required powder factor and costs. As the geotechnical model can predict changes in geotechnical conditions, the blasting

Jan 1, 2007

By J. M. Lottering

Paper written on project work carried out in partial fulfilment of B Eng (Chem) degree Operational factors influencing the electrostatic separation of mineral sands were investigated in a laboratory separator. Measurements were collected online by means of an optical sensor using diffused reflectance spectroscopy to determine the mineralogical composition. The results have shown that the roll speed and potential were the dominant operating variables, collectively explaining more than 83% and 68% of the product grade and yield, respectively. In contrast, the feed rate, temperature and position of the plate did not affect separation. The effect of the ambient relative humidity, ranging from 10% to 45%, could not be assessed conclusively and at best appeared to have a weakly beneficial effect on the product grade. Keywords: process modelling, high tension roll separator, mineral sands

Jan 1, 2006

By J. Ekengård, H. Srinath, M. Andersson, P. Jönsson, D. S. Sarma

The present paper deals with mixing between the metal and slag phase during the ladle refining process, including vacuum degassing. Dispersion of metal drops in ladle slags has been studied. The results show a larger quantity of metal droplets in ladle slag during the alloying and stirring phase than during the subsequent vacuum degassing phase. The thermodynamic and kinetic aspects of the interaction between metal drops and the slag matrix have been considered and probable reasons for the observed distribution discussed.

Jan 1, 2004

By I. A. Minaev

The conditions of a stability of metallurgical films on a surface of solid on the basis of classical regularities of a thermodynamics are considered. For specific conditions of metallurgical processes the basic equations relevant to non-metallic inclusions (product of steel killing) migration and transfer through the interface boundary of metal-slag are obtained. The basic criteria equations of conditions of stability of metallurgical dispersed systems are developed in view of films formation. The probable thermodynamics reason of wetting due to formation of stable films are discussed. The experimental measurement of thin and thick films elastic resistance for metallurgical systems are carried out and the results are discussed. The presence of a wetting thick film increases stability of dispersed systems (facilitates an inverse implication of non-metallic inclusion in a melt) due to a barrier effect of wetting films. The quantitative evaluations of non-metal inclusion stability for steel in contact with any metallurgical slag are carried out. The results are in accordance with technological experience. Keywords: Inclusion removal, Film thermodynamic, Slag-metal dispers system

Jan 1, 2004

By C. Maree

Paper written on project work carried out in partial fulfilment of B. Eng (Chem. Eng.) This paper describes the development and use of a process simulator to optimize gypsum recovery at Afmine, a small plant near Yzerfontein on the South African West Coast. The simulator consisted of models of the major plant equipment, viz. hydrocyclones, surge bins, settling tanks, a primary sieve and a dewatering screen. Experimental data suggested that the equipment could be modelled satisfactorily from data published in the open literature. Simulation studies have indicated that gypsum losses on the plant could be reduced substantially by means of some relatively minor modifications to the plant layout. Moreover, sensitivity analyses of the plant have indicated that optimization of the settling tanks should receive priority over the other process units.

Jan 1, 2005

By G. Kleyn

"Sub-standard practices and their adverse impact on safety performance remain a challenge in the South African gold mining industry. The purpose of this study was to investigate the root causes of sub-standard practices and the effect on safety performance in South African gold mines. The focus of the study was on the underground production operations at a gold mine in the Free State. The study consisted of three parts: a personal investigation into the causes of sub-standard practices at the mine, a comparison with the results of a cultural study performed at the West Wits mines, and a behavioural survey.The studies described in this article yielded similar results in terms of the key drivers behind sub-standard practices. It was found that substandard practices had a number of causes, and the origin lies within the habits, attitude, and behaviour of employees. Current methods of addressing sub-standard practices and improving safety performance were found to discourage employees from performing work safely and according to procedure. It was concluded that the lack of critical behavioural habits for the given work environment and job title could possibly be the primary reason for the occurrence of sub-standard practices. IntroductionSince the implementation of the Mine Health and Safety Act, 1996 (Act 29 of 1996) and the Mine Health and Safety Regulations, the South African mining industry has been striving to improve health and safety performance and has placed great emphasis on adherence to mine standards.The Act requires employers in the mining industry to report accidents, incidents, and dangerous situations to the Regional Principal Inspector of Mines in their area. The data provided by employers is captured and analysed by the South African Mines Reportable Accident Statistical System (SAMRASS) and made available for public viewing (Department of Mineral Resources, 2011).A review of the national mine-related accident statistics shows clearly that the South African gold mining industry has improved its safety performance markedly over the past decade, but is still facing major challenges (Figure 1). These include meeting the Mine Health and Safety Milestones (Department of Mineral Resources, 2011)."

Jan 1, 2016

By J. L. Havenga, L. J. van der Walt, J. T. Nel, H. Bissett

"SynopsisNew technologies used to manufacture high-quality components, such as direct laser sintering, require spherical powders of a narrow particle size distribution as this affects the packing density and sintering mechanism. The powder also has to be chemically pure as impurities such as H, O, C, N, and S causes brittleness, influence metal properties such as tensile strength, hardness, and ductility, and also increase surface tension during processing.Two new metal powder processes have been developed over the past few years. Necsa produces zirconium powders via a plasma process for use in the nuclear industry, and the CSIR produces titanium particles for use in the aerospace industry.Spheroidization and densification of these metal powders require remelting of irregular shaped particles at high temperature and solidifying the resulting droplets by rapid quenching. Spherical metal powders can be obtained by various energy-intensive methods such as atomization of molten metal at high temperatures or rotating electrode methods. Rapid heating and cooling, which prevents contamination of the powder by impurities, is, however, difficult when using these methods for highmelting- point metals. For this reason plasma methods should be considered.Thermal plasmas, characterized by their extremely high temperatures (3000–10 000 K) and rapid heating and cooling rates (approx. 106 K/s) under oxidizing, reducing, or inert conditions, are suitable for spheroidization of metal powders with relatively high melting points. Thermal plasmas for this purpose can be produced by direct current (DC) plasma arc torches or radio frequency (RF) inductively coupled discharges. In order to obtain chemically pure spheroidized powder, plasma gases such as N2, H2, O2, and CH4 cannot be considered, while Ar, Ne, and He are suitable. Neon is, however, expensive, while helium ionizes easily and it is therefore difficult to obtain a thermal helium plasma at temperatures higher than 3000 K. Therefore argon should be used as plasma gas. Residence times of particles in the plasma region range from 5–20 ms, but this is usually sufficient as 7–8 ms is required for heating and melting of titanium or zirconium metal particles in the 30 µm size range at 3500 K. In this study the melting and spheriodization of titanium powders was investigated by DC non-transferred arc and RF induction plasma methods. The powders were characterized before and after plasma treatment by optical microscopy and scanning electron microscopy (SEM) to observe if any melting or spheroidization had occurred."

Jan 1, 2015

Using the philosophy that 'change cannot be introduced through memos-you have to get people emotionallyinvolved', SRK's Environmental Group in South Africa is helping clients communicate their environmental management objectives more effectively through the powerful medium of interactive industrial theatre. Existing and pending environmental legislation, international pressures, and growing awareness of the environment have led South African industry to the point where responsible care, for both the environment and the health and safety of those affected by the activities of an industry, is now a focus of management policies.

Jan 1, 1995

By X. H. Zhang, J. G. Cai

This paper discusses the behaviour of large-span tunnels and caverns in hard rock in a major underground storage project. In-situ stresses were measured using hydraulic fracturing during site investigation and 3-D overcoring during construction, with both showing a horizontal stress ratio of 2-3 times the vertical stress. Rock reinforcement design was based on the Q-system combined with numerical modelling for special design cases. Tunnel design and performance were checked and monitored by in-situ instrumentation during rock excavation, including measurements of deformation, convergence, and load on rock bolts. Deformation measurements using borehole extensometers included one borehole drilled into the virgin rock before rock excavation, which provided a direct and very insightful comparison with the various deformation measurements made during rock excavation. These measurements coupled with numerical calculations have proven that the high horizontal stresses to be very favourable to the stability of the large openings.

Jan 1, 2003

By J. Björkvall, S. Ångström, L. Kallin

In this paper results from industrial trials of CaC2 injection during stainless steel production in an electric arc furnace at Sandvik Steel is presented. The main purpose of the investigation was to analyse the effect of the injection on slag foaming and final chromium oxide concentration in slag. The results show that both an increase in slag foaming and a decrease of the final chromium oxide could be obtained during the charges with CaC2injection. On the basis of the results, the economical requirements are also discussed. Both the technical and economical requirements could be achieved for steels alloyed with Mo. In order to secure the economical requirements for all steel grades of interest, the injection technology must be further developed. It would also be important to utilize the positive effect of the slag foaming on the electric energy consumption. The work has been performed as a part of MEFOS frame research programme with participants from Sandvik Steel, AKZO Nobel and Avesta Polarit. Keywords: stainless steel, EAF, slag foaming, injection, CaC2

Jan 1, 2004

By H. Krogerus, P. Jokinen, T. Lintumaa

The energy consumption and recovery of chromium are important economic factors in ferrochrome production. Outokumpu has a lot of experience of the reduction behavior of the sintered pellets in industrial-scale furnaces and also on the grounds of numerous laboratory and pilot-scale investigations. Sintered pellets have shown a superiority over lumpy ore and briquettes made of the same chromite grade. The good performance of the pellets has also resulted in investigations on the reasons for such a performance. In this study, the factors affecting pellet behavior in smelting furnace were investigated. This study is divided into two sections, i.e. the investigations were on the factors affecting solid state reduction and on the factors affecting reduction under melting. These tests were performed by means of thermo gravimetry and by smelting tests. The correlation between the pellet characteristics and reduction behavior was shown and its influence on industrial-scale furnaces was discussed. Factors worth of consideration are for instance, the extent of oxidation during sintering, slag formation and chemistry in respect of molten state reduction, and the grain size of the chromite mineral in the raw material in respect of kinetic reasons (retention time in smelting).

Jan 1, 2007

By S. Fazluddin, K. C. Sole, M. R. Serwale, T. Coetsee

The CSIR-Ti process employs lithiothermic reduction of titanium tetrachloride feedstock to produce titanium sponge. The product is therefore contaminated by a range of lithium and chloride species. In this study we examine the effects of particle size, temperature, and HCl concentration as input leaching variables on the removal of chlorides from the crude titanium sponge. A review of the aqueous chloride chemistry of Li and Ti provided initial conditions for leaching of impurity species from the sponge. Experimental results confirm that the effectiveness of leaching and removal of dissolved impurities from the sponge are dependent on leaching kinetics, which are influenced by temperature, particle size, and morphology. Of the variables tested, reaction temperature had the strongest influence on the oxygen content of the leached product. The HCl lixiviant concentration had a negligible effect under the conditions tested. Leaching of crude titanium sponge (−10 mm size fraction after crushing) at 14°C in either 1 M or 0.032 M HCl yielded a titanium sponge product that met the ASTM standard specification for commercially pure Grade 1 titanium, i.e., oxygen content < 0.18 mass% and chloride content < 0.15 mass%.

Dec 13, 2022

By R. J. Fruehan

Slags have many useful functions in iron and steel making. In particular, slags are used to remove impurities such as sulphur, phosphorus and inclusions from the metal, and a large amount of research has been done in this area. Slags also insulate the metal thermally and form reactions with the atmosphere such as reoxidation and nitrogen pick-up. However, slags serve other more unique functions, several of which are reviewed in this paper. The role of slags in new iron smelting processes with regards to reduction of ore and gaseous desulphurization are discussed. In iron smelting processes, much of the reduction occurs by the reaction of carbon in the char and the metal suspended in the slag with iron oxide dissolved in slags. The slags also react with the gas resulting in sulphur removal from the process. The mechanisms of these reactions and pilot plant data for these processes are given in this paper. Slag formation within ferrous burden materials affects the cohesive zone and the performance of the blast furnace. Recent theoretical and experimental findings on this topic are presented. In the electric arc furnace, foamed slags are used to allow for higher power operation and productivity. Of particular interest, foaming in stainless steel production is more difficult than for normal steels. The foam index, or the ability of the slag to foam, for stainless steelmaking is similar to that for carbon steelmaking slags. The poor foaming is due to the lack of gas generation for the foam. Methods to increase foaming in stainless steelmaking are discussed.

Jan 1, 2004