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By M. A. Jensen, J. J. Bettencourt

SYNOPSIS An analysis was made of records of accidents involving Bantu mineworkers and which resulted in either minor injuries or hospitalizations to determine patterns in underground accidents from which to formulate priorities in accident prevention in gold mines. The results showed that: (i) specific labour categories, such as inexperienced men, are exposed to certain types of hazards the extent of which warrant the separate design of safety programmes to meet their specific needs; (ii) the systematic study of minor accidents provides a dependable source of. information of which safety departments could make greater use in their efforts to control and prevent mining accidents.

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

The Gordonsville Operation of Pasminco US Inc. along with the Center for Advanced Mineral and Metallurgical Processing (CAMP) at Montana Tech studied, developed and implemented a pilot scale hydrometallurgical facility for the industrial recovery of germanium and gallium. This paper describes the joint testing and engineering program that culminated in this successful process. 1. Introduction The Pasminco US Inc. (PAS), Gordonsville Operation, has been producing zinc concentrate continuously since 1975. Within the zinc concentrate, several byproduct elements were found to be significantly concentrated including gallium and germanium. The gallium and germanium replace zinc and other metals within the crystal lattice structure of the zinc mineral (sphalerite) and are concentrated in the same manner as the zinc mineral. This concentrate is then sent to the Pasminco Clarksville Zinc Refinery for further processing. Within the hydrometallurgical zinc-processing plant at Clarksville, a residue is formed that contains a majority of the impurities that would otherwise contaminate or hinder the zinc process. Approximately 5,000 tons of residue is formed annually containing approximately 0.80% gallium and 0.60% germanium along with significant quantities of iron, zinc, silica, and lead. Pasminco currently sells this residue for the germanium value. Until recently, no revenue for the gallium was obtained from the sale of the residue.

Jan 1, 2008

By K. Ding

The thermodynamic activity of MnO was measured in MnO-CaO-MgO-SiO2slags that are typically encountered in the production of manganese containing stainless steels. Gas equilibration-quenching technique was employed in measuring the activities. Activity of Mn in Pt-Mn alloys were redetermined at 1600°C which reconfirmed earlier results of strong negative deviations. MnO activities were then measured by equilibrating slags of various compositions based on a statistical experimental design procedure with Pt-Mn alloys under controlled partial pressure of oxygen in MnO saturated platinum crucibles at 1600°C. Activities of MnO were found to increase with increasing concentration of MnO, basicity and CaO to MgO ratio. Two multi-coefficient repression models were developed to predict the activities and activity coefficients of MnO in slags at 1600°C. Keywords: activity, MnO, slag.

Jan 1, 2004

By J. Szlazak, A. Tor, M. Borowski, N. Szlazak, D. Obracaj

This article presents the analysis of ventilation systems used in dead-end headings, while being drilled, in coal mines. Special emphasis is put on methane and dust hazard. Mathematical model for distribution of methane concentration in a heading is given as well. This model takes into consideration sources of methane emission and change in air flow rate due to leaks in a duct line. Solving equations presented in this article enabled giving dependencies describing distribution of concentration along the heading. On the basis of these dependencies there is a possibility of determining places with higher methane concentration and ways of combating this hazard. Determining the distribution of methane concentration in dead-end headings ventilated by a separate ventilation system is of great importance as far as work safety conditions are concerned. The information obtained may be of use when finding proper places for installing methane sensors. Three kinds of separate ventilation systems were distinguished: forcing, exhaust and overlap. The development in construction of fans and spare parts of a duct line enables using both forcing and exhaust ventilation systems in headings developed by continuous miners, with length above 1000 m, in the conditions of methane, temperature and health-detriment dust hazards.

Jan 1, 2003

By S. Witzke, J. Lehmann, H. Gaye

The modelling work presented here concerns Ni-bearing steels produced by Imphy Ugine Précision. In such grades, the contents of elements such as silicon or titanium must be precisely controlled by slag/metal treatments. The slag phase is described by IRSID slag model that has been slightly revised in order to better fit recent SiO2activity measurements in the low SiO2content domain of the CaO-Al2O3-CaO system. The metallic alloys are described by the unified interaction parameter model (UIPM). In this formalism, the interaction coefficients, giving the effect of nickel on Al, Si, Mn and Ti activities, have been determined by electrochemical measurements and/or extracted from industrial data on slag/metal treatments concerning a wide range of alloy compositions: [ ] Keywords: slag, Ni alloyed steels, activities, interaction coefficient

Jan 1, 2004

By T. Phiri, Antoine Floribert Mulaba-Bafubiandi

Microwave energy has been recently used in minerals processing to speed up the leaching process or to improve the liberation of targeted minerals (Al-Harahshed and Kingman, (2003); Bradshaw et al., (2001)). Applied to the roasting of sulphide minerals, microwaves allow the ?tunning? of calcine types and products quality in addition to the energy savings as opposed to the conventional roasting (Mulaba, 2006). As more than 85% of world zinc is produced through the ?roast-leach-electrowin? route, an attempt was made to optimize cost, energy and product quality for metal extraction process route. The use of microwaves was the alternative process route selected for the optimisation. Pyrite concentrate (0.17% Zn, 0.09% Cu, 35.71% Fe, 43.76% S) and sphalerite concentrate containing 43.81% Zn, 0.37% Cu, 3.86% Fe and 44.39% S were microwave roasted in a multimode cavity of 2.45 GHz with varying power levels and for different durations. The produced calcines were characterized using AAS, XRF, XRD and Mossbauer spectroscopy while the determination of residual Sulphur was used as products quality control tool to ascertain the degree of roasting achieved on the feed. The leachability of the produced calcines in HCl, HNO3, H2SO4 and HNO3 + HCl has been studied in terms of the best leaching yield, process kinetics economics and environmental aspect. With 800 W power for 30 minutes, ZnO and Fe2O3 were formed corresponding to a 70% sulfur removed from sphalerite and 80% from pyrite concentrates respectively. While the roasting of the above concentrates appeared to be a first degree processes, it was noticed that the microwave assisted roasting of sphalerite and pyrite concentrates yielded lower sample surface temperature for a shorter time (i.e.less than 30 minutes) microwave exposition. Longer time (more than 30 minutes) microwave exposure showed a linear increase in temperature in function of power level used. While optimum roasting conditions were found at 800W, 30 minutes, a 10% increase of sulfur removal was noticed while pyrite concentrate was microwave roasted. Sulfuric acid was seen to give higher leaching yield than nitric acid. Zinc dissolution was hindered by the presence of franklinite.

Jan 1, 2007

By A. Beitz, P. Smartt, G. Einicke, G. Rowan, P. Glynn

Coal is Australia’s highest export earner and Australia is the world’s largest exporter of coal. With coal now being extracted from deeper reserves under increased risk profile, and in the interest of aiding the stability of coal supplies, Japan is funding a number of safety projects in Australia and China. The CSIRO, Australia’s premiere research organisation with the country’s largest exploration and mining research group, are currently undertaking a jointly funded Japan-Australia safety project at Anglo Coal’s new Grasstree Colliery in central Queensland. The project, entitled Mine Communication and Information for Real-time Risk Analysis, will deliver step-change capabilities in data integration, decision support, gas monitoring, geo-technical monitoring, emergency response and personnel safety to the Grasstree Colliery. Some key activities include: developing and installing underground coal mine Ethernet LAN components, real-time monitoring of gas and geo-technical sensors, MODBUS serial to TCP/IP converters, e-reporting of underground conditions, emergency guidance systems and underground trials of Internet Protocol telephone and video. The project seeks to integrate (in real time) key data sets from the comprehensive and diversified range of propriety system currently in use at mines (ventilation, strata, operations e.g. haulage, pumps, conveyors etc) into a single integrated risk management interface. This interface will filter the data through a rules-based inference engine that will cross reference the various data streams, compare with past events and outcomes associated with the similar historical data and present this “intelligence” to

Jan 1, 2003

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 S. J. Frank

The development of feedforward semi-empirical control models for furnaces and the evaluation of mass balances are based on plant data. The models can only be as good as the data and it is therefore required to know the inherent uncertainty associated with the plant data. This uncertainty stems mainly from the fact that the slag, alloy or dust, have a distributed nature that depends on the degree of mixedness. It is commonly accepted that melts from open bath furnaces are well-mixed, and submerged arc furnaces less so. The impact of this assumption is significant, as a reasonably homogeneous melt could be represented by one sample only. As so much of metallurgical control depends on the assay information of the alloy and slag melts from furnaces, it was decided to characterise the possible variation in melt chemistry and temperature. Sampling campaigns and continuous temperature measurement of the melts were performed for different alloy and slag taps at a major ferrochrome producer. Both a submerged arc furnace and open arc furnace are evaluated in this way, by way of comparison. The slags of both open arc and submerged arc furnaces were found to be of similar degrees of homogeneity, with much spatial variance in the reducible iron and chromium oxides. However, it was found that the alloy melts deriving from open arc furnaces were significantly less homogeneous than the alloy derived from submerged arc furnace alloy production. The compositional variance could be related to the furnace operating conditions and it affects both metallurgical accounting and process control. In all cases it was found that the variance in melt solute components are larger than can be ascribed to analysis instrument error. It will be shown how this predetermined variance in melt composition could be included in process modelling and control.

Jan 1, 2004

By U. Kumar

Product designed characteristics like reliability and maintainability affect maintenance cost, service performance, and therefore product support strategy must be defined during design stage in terms of these two dimensions. Furthermore product support and service delivery strategy has considerable influence on the total life cycle cost and the economic viability of industrial systems/products. he paper presents a concept for the development of service delivery strategy for industrial products with a special reference to mining systems. In this paper we emphasize that the strategy for product support should not be centred only on ‘product’ but it should also take into account the service delivery capability of the manufacturers/suppliers and users service organization, users competence and capability, product use location, logistics and infrastructures, etc., to arrive at the best performance and economic results. Such strategy should invariably include services supporting the client apart from considering services supporting the product. The discussion in the paper is based on the experiences from the manufacturing industry engaged in manufacturing of mining systems and the observed trends in technology and management of operation and maintenance of mining systems. Keywords: Maintenance and product support, Service supporting client, Service delivery strategy, Products reliability and maintainability, Product use location, Operating environment, etc.

Jan 1, 2003

By J. P. Piguet, Y. Wileveau

ABSTRACT : An experimental programme for damage assessment was performed in the vicinity of the main shaft of Andra’s Underground Research Laboratory, currently under construction in the East of France, when the shaft is crossing the Kimmeridgian marls between 80 and 100 m depth. The mechanical behaviour was analysed by mean of convergence and displacement measurements. The disturbance into the wall was assessed using numerous methods such as measurement of sonic velocities, permeability measurement and VSP measurement in radial boreholes. The intensity of the damaged zone is low, and its extension does not exceed 0.5 time the radius of the shaft. It does not seem to depend on blasting patterns. ZUSAMMENFASSUNG : Ein Forschungs- und Versuchsprogramm wurde aufgestellt, um die beschädigte Zone im Bereich der Kimmeridgemergel zwischen 80 und 100 Meter Tiefe beim Zugangsschacht des im Bau befindlichen Andralabors im Osten Frankreichs zu berechnen. Das mechanische Verhalten der Formationen wird auf der Grundlage von Konvergenz- und Verschiebungsmessungen ermittelt. Verschiedene Messmethoden, wie z.B. mikroseismische Geschwindigkeite Messungen, Permeabilitäs- und Beschleunigungsbestimmungen in strahlenförmigen Bohranordnungen, erlaubten die Ermittlung des Beschädigungscharakters der Schachtwand. Die Intensität der beschädigten Zone ist niedrig, ihre Ausdehnung übersteigt nicht die Hälfte des Radius des Zugangsstollens und scheint unabhängig vom Schema der Sprengstoffanordnungen zu sein. RESUME : Un programme expérimental visant à évaluer la zone endommagée autour du puits d’accès du Laboratoire de Recherche Souterrain de l’Andra actuellement en construction dans l’Est de la France a été mis en œuvre lors de la traversée des marnes du Kimméridgien entre 80 et 100 m de profondeur. Le comportement mécanique des formations est évalué à partir de mesures de convergence et de déplacements. La mise en œuvre de nombreuses méthodes, telles que des mesures microsismiques, des mesures de perméabilité et d’accélérométrie en forages radiaux, a permis de caractériser l’endommagement en paroi du puits. L’intensité de la zone endommagée est faible et son extension ne dépasse pas 0,5 fois le rayon du puits. L’endommagement semble indépendant des schémas de tirs testés.

Jan 1, 2003

By GA Harrison

The introduction of Extra Low Profile (XLP) mechanised equipment within Anglo Platinum is aligned with the overall New Mining Technologies strategy to focus on continuing modernization of our mining operations to achieve injury free sustainable production and cost effective mining technologies. The method allows for the introduction of a suite of XLP and Low Profile (LP) equipment in a narrow reef (1,2m) mining environment. For the first time it is now possible to achieve total trackless mechanisation at these stoping widths and XLP Breast mining has the potential to add more value when benchmarked with conventional mining and other mechanised methods. Various types of XLP equipment were tested at different sites within Anglo Platinum and this paper describes the XLP equipment evolution to-date. It concludes with recommendations on our future strategy regarding implementation and roll out of the XLP technology within Anglo Platinum.

Jan 1, 2008

By W. P. Nel

The introduction of the Higher Education Qualifications Framework (HEQF) and the updated Higher Education Qualifications Sub-Framework (HEQSF) has caused many South African university departments to rethink their programme qualification mixes (PQMs). In addition to the requirements stated in the HEQSF, a number of other factors have to be taken into consideration by a university department. These factors include, for example, the standards generated by the Engineering Standards Generating Body (ESGB) and subsequently approved by the Engineering Council of SA (ECSA) and the need to prepare students for various categories of professional registration with ECSA. This means that a university department has to choose the correct mix of Learning Programmes (LPs) from the HEQSF menu (which consists of 13 types of LPs). Preparing students for ECSA registration is aligned with the mission of universities, which is to teach and undertake research. However, research and the LPs associated with research go beyond the requirements for current ECSA registration. Assuming that universities offering engineering LPs would elect to prepare students for both ECSA registration and teach them to produce research outputs, which is mostly done at Master and Doctorate levels (NQF Levels 9 and 10), then it follows that academics are more interested in NQF Level 5 to 10 pathways (abbreviated as ?L5-10?) rather than the shorter pathways required towards professional registration. (For example, ECSA requires an NQF L5-L7 pathway for registration as a candidate professional technologist. This specific pathway may consist, for example, of two LPs, namely the 360-credit Diploma and the Advanced Diploma.) A L5-L10 pathway is a combination of LPs that will prepare the learner with a NSC (or equivalent qualification at level 4) to Doctoral level (level 10). Universities may choose at least four major pathways from the HEQSF menu in order to educate and develop students from NQF Level 5 to 10. However, various pathways towards registration in the category of candidate with ECSA are also embedded into these four NQF L5-L10 pathways, where each consist of a unique combination of LPs. Each of these pathways has an opportunity cost, and economic reality means that smaller departments may have to choose between the four pathways. Of all the many factors involved in PQM decision-making, the focus of this paper is on the HEQSF requirements, ECSA standards, and ECSA registration and how these, together with the various qualifications and educational LPs provided for by the HEQSF may impact on the PQM decision taken by engineering departments and schools at South African universities. The proposed four NQF L5-L10 ?pathway tool? for PQM decision-making may be useful for pointing out the advantages, disadvantages, and applications of the various pathways and combinations of pathways. Rather than deciding from a menu of thirteen qualifications and associated LPs, this article proposes that decision-making be undertaken on the basis of a menu of four main articulated ?NQF L5-L10? pathways (which also include one or more of the ECSA?s pathways for professional registration). The proposed ?NQF L5-L10 pathway? tool is an attempt to move one step closer to the aim of achieving a structured decision-making approach for designing a PQM at departmental level.

Jan 1, 2014

By V. I. Zhuchkov, L. A. Smirnov, E. I. Arzamastsev, A. A. Babenko

A brief analysis is given for state-of-the-art of manganese and chromium ferroalloy production in Russia and their consumption by metallurgy plants. The main causes of low output of manganese and chromium ferroalloys, and ways to resolve the issue of ferroalloy production development are considered.

Jan 1, 2004

By Y. -J. Park, K. -H. You, Y. -T. Choi, Lee. H. -W.

Many large caverns are being constructed in great depths in Korea mainly for the storage of oil and LPG. These caverns are mostly located near the port where rock conditions are reasonably good. In some instances, the horizontal stress is very high and endangers the stability of the cavern. The purpose of this study is to assess the stability of large caverns excavated in a rock mass with high horizontal stress where Ko value is close to 3. Result shows that stress exerted in the shotcrete at crown exceeds allowable value when the 3rd bench is excavated. Also found is the tensile failure of shotcrete near the boundaries between benches. In Korea werden viele grosse Kaverne fuer Aufbewahrung vom Oel und Fluessiggas in grosser Tiefe gebaut. Am Meisten befinden sich diese Kaverne in der Naehe von Haefen, wo der Fels gute Verhaeltnisse zum Bauen einer Kaverne besitzt. In einigen Faellen ist die Horizontalspannung sehr gross und dadurch wird die Stabilitaet vom Kaverne gefaerdet. Der Zweck dieser Arbeit ist die Stabilitaet des im Fels gebauten grossen Kavernes mit hoher Horiaontalspannung zu schuetzen, wo Ko-Wert sich auf 3 naehrt. Die Ergebnisse zeigen, dass die Spannung im Spritzbeton an der Krone den zulaessigen Wert ueberschreitet, wenn das dritte Bank ausgegraben wird. Im Bereich des Spritzbetons zwischen Baenke wurde das Zugversagen festgestellt. Des larges cavités nombreuses sont en train d’être construites en grand profondeur en Corée prin-cipalement pour le stocage du pétrole et LPG. Ces cavités sont pour la plupart situées près de la porte oú les conditions des roches sont résonablement bons. En quelques cas, la contrainte hori-zontale est trés haute et met en danger la stabilité de la cavité. L’objet de cet étude est d’estimer la stabilité des large cavités excavées dans une masse de roche ayant une haute contrainte horizontale oú la valeur de Ko est proche à 3. Le résultat montre que la contrainte exercée dans le shotcrete à la couronne dépasse la valeur admissible quand le troisième banc est excavé. En plus une faillite en tension du shotcrete près de la frontière entre des bancs est trouvée.

Jan 1, 2003

By Q. Lui, J. Oxenford

The occurrence of heavy minerals in the oil sands of Alberta has long been known and has been well documented in the literature. Unfortunately most of the researchers working on this resource have been unable to produce products that meet acceptable market specifications. This has resulted in many misconceptions about this resource. Recent efforts have shown that with some innovative approaches, marketable material can be produced and as a result it might finally be possible to realize the potential of this immense resource that, some have estimated, could contain in excess of 20% of the world demand by 2010. This paper highlights the uniqueness of this mineral assemblage and the mineral processing challenges it presents. It shows the most recent work that has resulted in the production of marketable titanium and zircon products. This paper also focuses on some of the special problems resulting from the variability in the heavy mineral suite. Of special interest is the occurrence and removal of bitumen and pyrite without adding to the sulphur dioxide loading in the regional airshed. The trend by the mining industry to develop various positions on ‘sustainable mining’ has some significance for the heavy mineral industry. Although the industry generally has an excellent track record of eventually rehabilitating disturbed ground in an acceptable manner, heavy mineral mining operations tend to have a relatively large footprint of disturbance and the industry is under considerable pressure to develop options that are more environmentally acceptable. In addition, as operators move to exploit deposits that are lower grade and/or are further from a port site, the emissions per unit of sold product will also rise and the industry will be under pressure to address this issue as well. Because heavy minerals from oil sands are by-products of existing operations, there are virtually no incremental disturbances or emissions that would be associated with heavy mineral production. All mining and tailings remediation issues are accounted for by the oil sand operation. The only incremental emissions would be those associated with the mineral processing operations and transport of finished products to a port site. This paper discusses the environmental and cost implications of this situation.

Jan 1, 2003

By RT White

For many years the concept of life cycle costing (LCC) was promoted for decision making in corrosion protection systems. Nevertheless, the application of LCC was limited. Input data was often sourced from suppliers and met with scepticism. As a result final analysis was often insufficiently rigorous to meet the needs of Project Managers in sound decision making. The need for expediency often resulted in non-optimal corrosion protection system specifications. With improved communications and the global reach of industries, case history data, based upon actual performance has been able to provide input to substantiate decision making. However, today?s focus upon sustainability whereby environmental, economic and even social aspects enter into decision making has extended LCC into Life Cost Analysis (LCA). In an LCA analysis energy and environmental inputs into systems are compared as part of an overall assessment. The development of Agenda 21 at the Rio summit of 1992 has challenged the countries of the world to look at sustainable development in every economic activity. This ranges from construction to mining to electricity production to automotive production, use and disposal. The protection of buildings, infrastructure and transport systems is part of the needs of sustainable development. Zinc based corrosion protection has been an important part of the arsenal of the corrosion protection industry. This paper will highlight the use of LCC and the development of LCA with reference to the use of zinc based protection systems in a number of important industries.

Jan 1, 2006

By E. Yan

Electrostatic separation has been a mainstay of minerals sands flowsheets for over 50 years. Recent electrostatic developments have shown better conductor/non-conductor separation than technology previously available. Results to date show significantly increased separation efficiency over prior-art high-tension roll electrostatic separator (HTR). These improvements allow greater simplification of MSP circuits by minimizing re-circulating loads. The distinct features of the eForce include: 1) A provision that minimizes the affects of particle size to improve separator performance, 2) an enhancement of the design and arrangement of the static electrode providing a greater attraction force for separating fine conductive particles, and 3) inner roll and outer plate electrode configuration to improve separation efficiency and throughput capacity. Key Words: eForce, Electrostatic, Ion bombardment, HTR, Separation Efficiency, Electrostatic Classifier

Jan 1, 2003

By Jacolien P. Wyethe

Zincor uses a Roast-Leach-Electrowinning circuit to process zinc sulphide concentrates. It also processes zinc oxide fume, originating from a slag smelting operation in the Democratic Republic of the Congo (DRC). Zincor achieved an average zinc recovery of 90.3% during the period January 2006 to May 2007. The bulk of the losses occurred in the iron and lead silver residues, both as soluble and un-dissolved losses. The un-dissolved losses in the iron residue constituted around 33% of the total zinc lost from the circuit, and were largely attributed to the presence of zinc-ferrite in the calcine used for neutralization during iron removal. As part of Zincor?s continuous improvement programme, the un-dissolved zinc losses in the iron residue were targeted by: the partial replacement of calcine with zinc oxide fume (from the DRC); and the preferential use of ?low-ferrite content calcine? as neutralizing agents in the iron removal circuit. These initiatives, coupled with other operational factors, resulted in a marked improvement in recovery to 92.6% during June to December 2007. The zinc oxide fume, directly fed to the circuit, required investigation of the halide rejection capacity of the Zincor circuit. Rejection of chloride via the magnesium bleed operation was considered adequate. Fluoride was mainly rejected via the iron (~70%) and lead silver (~27%) residues. Fluoride rejection via the lead silver residue varied significantly, probably as a result of variations in the sparingly soluble CaF2 content in the feed. The mechanism for fluoride rejection in the iron residues is uncertain. The fluoride rejection capacity of the Zincor iron residue (comprising of mainly jarosites, schwertmannite and ferrihydrite) at 2 ? 4 mg/L F in solution, was estimated at 0.14 ? 0.19 kgF/tFe residue.

Jan 1, 2008