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By R. S. Francis

There are no manuals or handbooks for budding mill superintendents or process plant managers. Most who obtain this level of responsibility have gained their training from watching the good and bad of their predecessors and the successful ones have themselves graduated from the school of hard knocks. This paper attempts to provide some helpful guidelines and direction for those who aspire to better manage a mineral processing facility. The authors have 20 years combined experience in senior management roles at nine different mineral processing operations in Australia and overseas, covering gold, base metals and mineral sands. This summary of tips and pitfalls will hopefully benefit future leaders in mineral processing and metallurgy.

Jan 1, 2007

By Karl-Heinz Obst, Juergen Stradtman

The importance of the chemical and physical properties of lime has been overlooked for years although the quality of lime plays an important role in the production of steel. With the introduction of the oxygen injection process these properties have been re-evaluated. The CaO, MgO, S, and P2O5 contents of lime are important, but so are the physical properties such as granulation, reactivity with respect to slag formation, and the degree of burning. Soft burnt lime enhances de-phosphorisation and de-sulphurisation, and facilitates the smelting process in general, mainly due to its large specific surface. Special lime, prepared as briquettes from quicklime and fluxes or as pellets from limestone and various fluxes with or without binding agents, clearly accelerates lime dissolution during the slag formation process, lowers the melting point, and enhances de-phosphorisation, de-sulphurisatlon, and de-carburisation even more than soft burnt lime. The introduction of special limes in the oxygen injection process for steel production has opened up new fields for commercial exploitation of slags as well as improved operational techniques.

By A. Santana, J. Jankolovits, G. S. Reyes

The flotation of sulfide ores that contain carbonaceous gangue requires significant operational and chemical intervention to achieve suitable metallurgical outcomes. Carbonaceous gangue dilutes concentrate grades, alters the froth behaviour, reduces operational stability, adsorbs reagents, and reduces value recovery. Carbon management processing strategies like preflotation and depression are often presented as point solutions. Moreover, oversimplified mechanisms of carbon depressants belie their complex and nuanced impact on flotation behaviour. Optimising the flotation of carbonaceous sulfide ores requires a holistic consideration of interactions between the carbon management reagents and the processing strategy, ore mineralogy, flotation behaviour, flowsheet, and all other aspects of the flotation system. Examples are shown where conventional, simplistic mechanisms of carbon depressants fail to explain the observed flotation behaviour. The multifaceted impacts of carbon depressants on froth behaviour, collector performance, and value recovery highlight the need for a holistic approach to carbon management. Keywords: Carbon management, carbonaceous ores, sulfide flotation, carbon depressant

Jan 1, 2020

By I. M. Morsi

The present study investigates the feasibility of using some materials as start-up slags for the extraction of magnesium metal from Egyptian dolomite ores by the Magnethermic technique. The reduction of roasted dolomite (dolime) takes place in a closed evacuated electric arc furnace (small Magnetherm reactor) using ferrosilicon as a reducing agent and liquid start-up slag as a reduction bath under an inert atmosphere. The operational parameters affecting the stabilization of the start-up slag composition and the extraction of magnesium such as reducing agent stoichiometry, reduction temperature, and time were investigated. The dolomitic charge was in the form of sintered briquettes. The charge was reduced under an argon atmosphere in the Magnetherm reactor for constant period and constant temperature. The results showed that the clinker can be used as a start-up slag for the magnethermic process. Also, the optimum conditions for the extraction process were found at 2XSi stoichiometry to give maximum reduction of 80% after 15 minutes reduction time at a temperature of 1550°C. XRD and XRF measurements were used to determine the phases present and the extent of reduction of magnesium, respectively. Keywords magnesium, dolomite ore, magnetherm, magnetherm reactor, silicothermic reduction.

Jun 1, 2013

By P. G. H. Pistorius, D. S. Konadu, G. Lubbe

The aim of this investigation was to determine whether the composition of a shielded-metal arc-welding electrode coating affected the low-temperature impact toughness of austenitic stainless-steel weld metal. It is generally accepted that increases in the δ-ferrite and nitrogen contents result in a decrease in toughness at low temperatures. Weld metal from electrodes with a basic coating also generally exhibit better toughness than those from rutile (acidic) electrodes. An increase in basicity was expected to decrease the number and size of inclusions, which in turn provides a tougher weld metal. Three commonly available potassium–rutile E308L electrodes were used, complying with the E308L-16 and E308L-17 specifications. Analysis of the electrode coatings showed very similar chemistry and basicity. Significant differences in the inclusion contents of the weld metals were observed: the E308L-17 weld metal had a lower inclusion content (1.4% by volume) than the E308L-16 weld metal (3.7%). The former had higher impact toughness at all temperatures, despite a slightly higher nitrogen content. Regression analysis confirmed that the inclusion content had a significant effect on the impact toughness at all temperatures.

Jul 2, 2022

By A. Adeli, A. V. Metcalfe, E. Addo, E. Sepulveda

"The accurate modelling of geometallurgical data can significantly improve decision-making and help optimize mining operations. This case study compares models for predicting copper recovery from three indirect test measurements that are typically available, to avoid the cost of direct measurement of recovery. Geometallurgical data from 930 drill core samples, with an average length of 19 m, from an orebody in South America have been analysed. The data includes copper recovery and the results of three other tests: Bond mill index test; resistance to abrasion and breakage index; and semi-autogenous grinding power index test. A genetic algorithm is used to impute missing data at some locations so as to make use of all 930 samples. The distribution of the variables is modelled with D-vine copula and predictions of copper recovery are compared with those from regressions fitted by ordinary least squares and generalized least squares. The D-vine copula model had the least mean absolute error. IntroductionIn this paper we compare the use of D-vine copula, generalized least squares (GLS), and ordinary least squares (OLS) for modelling geometallurgical data from an orebody in South America. The first objective is to construct models for predicting copper recovery (Rec) from the Bond mill index test (BWi); resistance to abrasion and breakage index (A*b); and semi-autogenous grinding (SAG) power index test (Spi). This involves fitting a D-vine copula and regression models fitted by OLS and GLS. The second objective is to investigate the performance of the fitted models for predicting Rec (Willmott and Matsuura 2005).Traditional resource model approaches either ignore the mineral processing characteristics of extracted tonnages or treat processing as an independent component of a mining operation. The net present value (or any other objective) can be truly optimized only by considering the mining operation as an integrated system in which net value is defined as the end-product that the company sells. This approach requires the resource model to be extended to include all relevant rock properties and processing responses."

Mar 1, 2019

By D. Hanekom

Over the past couple of years, Anglo Platinum has made extensive use of technology within the core disciplines (geology, evaluation, survey, and planning) that collectively form part of mineral resource management (MRM). While these technologies were primarily developed to enable geology, evaluation, survey, and planning to carry out their daily tasks, with the main objective of supporting the mine?s production effort, they have also enhanced the disciplines? ability to produce the required outputs within the annual business planning cycle. Anglo Platinum has developed a very comprehensive business planning process, and these technologies play a vital role in enabling both the quality and quantity of inputs into the process, and also the value-add of the final product. This prompted a question regarding the practical application of the CADSMine software. If we changed our thinking in how we applied the software, would it be possible to further improve on the time taken to deliver a business plan? In changing the current planning approach, would we be able to further simplify the process? Is there a way to reduce the data generated in order to enhance the time taken to do reporting, as the CADSMine software is totally network dependent? Less data should equal faster reporting. This paper focuses on the practical application of the CADSMine software, and demonstrates the value-add to the business planning process that can be gained if the mine design methodology is changed from individual panels to bigger blocks representing a raise line.

Jan 1, 2012

By P. van der Westhuyzen

Gone are the days of stock-standard diamond beneficiation and final recovery circuits that could, with minor modifications, be adapted to treat any diamond-bearing ore source. A new era has dawned, offering the opportunity to streamline existing diamond processing operations or develop simpler, more efficient, and economical diamond processing plants, with the focus on more efficient comminution, beneficiation, and final recovery. This change in scene has been brought about by: ? The introduction, rapid development, and maturation of multiple comminution, sorting, and recovery technologies ? The need to adapt to a new standard of project approach post the commodity super-cycle phase, where optimizing existing operations and developing scalable, ?fit for purpose? new mines are fast becoming the norm in diamond processing plants in both primary and alluvial operations ? The quest for energy efficiency and lower labour costs ? More remote and inaccessible reserves (under lakes, tops of mountains etc.). This paper serves to identify some technology advances and demonstrates how these could be considered as replacements for or in combination with conventional technologies to arrive at an optimum techno-economic solution. To name a few applications/technologies: ? Comminution: conventional cone crusher, modified/specialized cone crusher, and the high-pressure grinding roll (HPGR). Although significant advances have been made in recent years, this paper only briefly covers comminution within the beneficiation circuit design ? Waste sorting: NIR (near-infrared) sorting, optical (colour) sorting, XRF (X-ray fluorescence) ? Primary concentration by combining dense media separation (DMS) with either XRT (X-ray transmissive), pulsed X-ray, jigs, or pan plants depending on the application, scale, and economics ? Final recovery of diamonds with either conventional X-ray technology, pulsed X-ray technology, or XRT. From recent studies, it can be concluded that there is no longer a standard solution, but rather the ?right? or appropriate solution. Through combining a sound knowledge of the ore source (ore dressing studies or onmine data gathering) and leveraging off the advances in technologies, one is able, through trade-off studies, to arrive at the ultimate techno-economic configuration, the ?right? solution. Emphasis is placed on maximizing diamond recoveries through appropriate technology selection and minimizing the associated costs in an effort to de-bottleneck or improve efficiencies of existing diamond processing plants, or to arrive at the ideal new diamond process plant design..

Jan 1, 2014

Notices Competition for Student Members of the South African Institute of Mining and Metallurgy Each year the Institute offers a prize (or prizes should the entries warrant it) of up to Rl00 for the best paper or dissertation on a topic appropriate to the interests of the Institute. The competition is open to all Student Members of the Institute. NEW PUPLICATION Bougainville-the establishment of a copper mine. St. Kilda (Australia), 'Foundations', 1973. The editors of Foundations, Australia's journal of architecture, engineering, and construction, are preparing the above book for publication late in 1973. The story of Bougainville is told and illustrated NIM REPORTS Report No. 1503 Fast-neutron-activation analysis for the determination of oxygen m rock sam ples. Report No. 1514 The determination by X-ray-fluorescence spectrometry of minor amounts of niobium and tantalum in geological materials. Report No. 1530 AUREOL - an X-ray-absorption analyser for the determination of the uranium on loaded resin in ionexchange plants. Report No. 1534 The determination, by atomicabsorption spectrophotometry, of noble metals in the presence of sodium, barium, or sulphate ions. A comparison of uranium and lanthanum as 'releasing agents.

Jan 10, 1973

By H. M. Friede

A short survey is given of the Iron Age smelting sites and smelting furnaces that have been found in South Africa. An attempt is made to classify South African smelting furnaces by the inclusion of functional characteristics such as the numbers and positions of tuyeres. An affinity is suggested between the Venda (eastern Transvaal) type of furnace and an East African type. The principles of the smelting process in South African Iron Age furnaces and the characteristics of the smelting products are discussed. Results of metallographic and chemical analyses of 19 iron specimens found at South African sites are given and compared with those from sites in Zimbabwe-Rhodesia, Mocambique, and Nigeria. The carburization and steeling of iron during primitive smelting and forging are discussed.

Jan 1, 1979

By B. Genc, C. Gous

Spontaneous combustion during coal mining operations is a major problem that affects the health and safety of workers and causes environmental problems. The phenomenon is associated with the presence of coal, coal shale, and pyrite. In 2020, a premature detonation incident occurred at an iron ore mine where the waste material contains black carbonaceous shale units known to be associated with pyrite. The spontaneous combustion propensity and properties of samples of the black carbonaceous shales from the mine were examined and compared with samples from the Witbank Coalfield. The spontaneous combustion liability indexes of these samples were correlated with X-ray fluorescence (XRF) and proximate and ultimate analyses using linear regression. The Wits-Ehac Index classification results show that the samples were between medium and high risk. The linear regression analysis showed very poor correlations between the Wits-Ehac Index results and the XRF and proximate and ultimate results. The most valuable relationship found is between the presence of relatively high sulphur (greater than 3%) and ground reactivity with nitrate-bearing explosive emulsion.

Jun 5, 2023

By S. Swanepoel, A. V. Cherkaev, Q. G. Reynolds, M. Erwee

Ferrochrome (FeCr) is a vital ingredient in stainless steel production and is commonly produced by smelting chromite ores in submerged arc furnaces. Silicon (Si) is a componrnt of the FeCr alloy from the smelting process. Being both a contaminant and an indicator of the state of the process, its content needs to be kept within a narrow range. The complex chemistry of the smelting process and interactions between various factors make Si prediction by fundamental models infeasible. A data-driven approach offers an alternative by formulating the model based on historical data. This paper presents a systematic development of a data-driven model for predicting Si content. The model includes dimensionality reduction, regularized linear regression, and a boosting method to reduce the variability of the linear model residuals. It shows a good performance on testing data (R2 = 0.63). The most significant predictors, as determined by linear model analysis and permutation testing, are previous Si content, carbon and titanium in the alloy, calcium oxide in the slag, resistance between electrodes, and electrode slips. Further analysis using thermodynamic data and models, links these predictors to electrode control and slag chemistry. This analysis lays the foundation for implementing Si content control on a ferrochrome smelter.

Mar 14, 2024

By M. A. Mahboob, T. Celik, B. Genc, I. Atif, S. Ali

"Mapping of hydrothermally altered areas, which are usually associated with mineralization, is essential in mineral exploration. In this research, open source reflectance spectroscopy data from the multispectral moderate-resolution Landsat 8 satellite was used to map altered rocks in the Gauteng and Mpumalanga provinces of South Africa. The unique spectral reflectance and absorption characteristics of remotely sensed Landsat data in the visible, near-infrared (NIR), shortwave-infrared (SWIR) and thermal infrared (TIR) regions of the electromagnetic spectrum were used in different digital image processing techniques. The band ratios (red/blue, SWIR 2/NIR, SWIR 1/NIR), spectral band combinations (Kaufmann ratio, Sabins ratio) and principal component analysis (Crosta technique) were applied to efficiently and successfully map hydrothermal alteration minerals. The results showed that the combination of spectral bands and the principal component analysis method is effective in delineating mineral alteration through remotely sensed satellite data. The validation of results by using the published mineral maps of the Council for Geoscience South Africa showed a good relationship with the identified zones of mineralization. The methodology developed in this study is cost-effective and time-saving, and can be applied to inaccessible and/or new areas with limited ground-based knowledge to obtain reliable and up-to-date mineral information.IntroductionMany developing nations depend on exploration and exploitation of mineral resources to sustain their economic growth. Usually, the traditional mineral exploration techniques require enormous finances, prolonged time, and tremendous manpower, particularly in areas that are not easily reachable (Maduaka, 2014). Furthermore, mineral exploration required state-of-the-art techniques and expertise along with geological, geochemical, and geophysical datasets, which may not be easily available or may be lacking where access is problematic (Kaiser et al., 2002; Bemis et al., 2014). Modern remote sensing technology has proved to be one of the highly efficient and robust techniques used for mineral exploration. The use of remote sensing satellite images for geological mapping and mineral exploration usually involves studying the physicochemical properties of rocks and weathering soils, such as mineralogy, landforms, geochemical signatures, and the spatiall distribution of lineaments (Bhattacharya et al., 2012)."

Mar 1, 2019

By C. H. Wyndham, N. B. Strydom

INTRODUCTION Acclimatization of the labour force to heat is an integral aspect of gold mining in South Africa. A recent survey revealed that about 250,000 Bantu mine workers require to be acclimatized to heat each year. Until 1965 men were acclimatized by means of one of the Chamber of Mines methods (introduced by the Human Sciences Laboratory in 1953). This type of acclimatization was carried out underground where men shovelled rock in hot stopes under careful supervision. However, it has become increasingly difficult in the last few years for mines to provide underground the conditions of work and environmental heat required for adequate acclimatization to heat. In examining an alternative to acclimatization in underground hot stopes, the Human Sciences Laboratory carried out a trial in 1965 of acclimatization in an air-conditioned climatic room on the surface of a mine. The new procedures developed from this trial have been so successful that there are today 26 climatic rooms on different mines. These rooms have been built following a design proposed by Mr Hodgson of the National Mechanical Engineering Research Institute1. Approximately 85 per cent of the total number of men being acclimatized each year are put through the new procedures in these climatic rooms. This paper gives an account of the problems which arose and how they were solved, the inter-relationship between physical conditioning and climatic room acclimatization, the prodecures developed for elimination of labourers with low maximum oxygen intakes, and the advantages of climatic room acclimatization. CLIMATIC ROOMS The majority of the climatic rooms (twenty) have been built on the surface, but a number (six) of mines preferred to establish their acclimatization centres underground in order to decrease the initial costs involved in the construction of such facilities. These underground climatic rooms are usually located near shaft stations in redundant haulages and they can accommodate from 200 to 400 labourers, thus eliminating the need for multiple acclimatization shifts. Figs. 1-4 illustrate various aspects of a surface climatic room. PROBLEMS WHICH AROSE IN INTRODUCING CLIMATIC ROOM ACCLIMATISATION There were four main problems which arose in connection with the introduction of the new method. These were: (i) The type and rate of work to be used. (ii) The air conditions required to obtain optimum acclimatization. (iii) The duration of exposure to heat each day and the total number of days of acclimatization. (iv) The methods of cooling labourers with high body temperatures. Shovelling rock would have been the desirable type of physical work to employ, but the air-conditioned space required to accommodate large numbers of men and the difficulty in standardizing the work rate in shovelling led to the decision to employ instead the work procedure used by the Human Sciences Laboratory in acclimatizing men in the Laboratory. This is the lifting of the body weight against gravity when men step on and off a bench. It has the advantage that large numbers of men can work physically at the required rate in a relatively small space (120 men can be accommodated in an area of 70 ft by 21 ft) and the cost of construction and ventilation of the climatic rooms is thereby reduced. Also the work rate can be standardized by varying the height of the stepping benches in relation to the individuals' body weights. The next problem was the air condition to be used in the climatic rooms. The Laboratory's research experience in acclimatization led it to choose an air temperature of 89°F (with the air almost saturated with water vapour) and an average velocity of air movement of 100 fpm. This air condition was combined with a work rate of 1,560 ft lb/min (oxygen consumption 1.0 litre/min) on day 1, and the work rate was increased gradually over the period of acclimatization to reach a work rate of 3,120 ft lb/min (oxygen consumption 1.6 litres/min) on day 9.

By A. Chiappone, M. Barla, U. Rabagliati, L. Repetto

ABSTRACT: The paper describes the application of both continuum and discontinuum modelling to the study of the stability conditions of the Alpetto mine, a high rock cut located in Cesana Brianza (Italy). The main objective is to provide valuable information for future mine planning and for the assessment of the stability conditions of the abandoned high rock cuts. Continuum modelling involved the applications of the finite difference method, whereas the distinct element method was used for discontinuum modelling. RESUME: L'article décrit l'application des méthodes de modélisation continue/discontinue pour l'étude des conditions de stabilité de la mine d' Alpetto, située à Cesana Brianza (Italie). Le but du travail consiste à determiner des paramètres utiles vis-à-vis du projet et d'estimer les conditions de stabilité de l'amas rocheux au terme de l'exploitation de la mine susmentionnée. La modélisation continue a impliqué l'application de la méthode des différences finis alors que la méthode des éléments distincts a été utilisée pour la modélisation discontinue. KURZFASSUNG: Der Artikel beschreibt die Verwendung der Modellierung von continuum und discontinuum zur Untersuchung/Studium der Stabilitätsbedingungen von der Alpetto Mine, hohe Aushubsfront in einer Felsmasse die sich in der Gemeinde von Cesana Brianza befindet. Das Hauptziel dieser Arbeit ist die Festlegung von Parametern die zur Planung nützlich/behilflich sein können sowie auch die Möglichkeit zur Analyse/Auswertung der Stabilität der Felsmasse-Front nach Aufhebung der Nutzung derselben. Die continuum Methode/Analyse wurde verwendet durch Unterstützung der Finite Differenz Methode da man für die Analyse der discontinuum (Fels als discontinuum beschrieben) der Distinct Elemente Methode verwendet hat.

Jan 1, 2003

1. Book reviews Physiochemical properties of molten slags and glasses, by E.T. Turkdogan. London, Metals Society, 1983.516 pp. £35. Reviewer: A.F .S. Scboukens Microstructural characterisation of metals and alloys, by P.E.J. Flewitt and R.K. Wild. London, Institute of Metals, 1984. £14. Reviewer: M.P. Sbaw Metallurgical applications of magnetohydrodynamics, edited by H.K. Moffatt and M.R.E. Proctor. London, Metals Society, 1984.346 pp. U.K. £35, U.S. $70. Reviewer: N.A. Barcza Extractive metallurgy symposium. Proceedings of a meeting on 12-14 November, 1984, organised by the Melbourne Branch. Parkville (Victoria), Australasian Institute of Mining and Metallurgy, 1985. Reviewer: B.K. Loveday Conference on gold mining, metallurgy and geology. Proceedings of a meeting on 9-11 October, 1984, organisedby the Perth and Kalgoorlie Branch. Parkville (Victoria), Australasian Institute of Mining and Metallurgy, 1985. Reviewer: B.K. Loveday Corporate policies for the 1980's in the steel industry, by Patrick Genevaz in collaboration with B.A. Bloom. La Chambre des Cartes, 26 rue de Piepus, 75012 Paris (France). U.S.$7oo, additional copies $140. Reviewer: D.C. Maree Mineral processing technology, by B.A. Wills. Oxford, Pergamon Press, 1984 (3rd edition). 629 pp. Hard cover £31.50, soft cover £9.75. Reviewer: B.K. Loveday Ma1lllgement information-ma1lllging for improYement, volume 2: symposium proceedings and additional papers. edited by M. Hammond. Doncaster (England), The Institution of Mining Engineers, 1984. 86 pp. £60 for vols. 1 and 2 (124 pp.). Reviewer: M.J .R. Meyer 2. Recent publications Tins and its and its uses no. 144, 1985. This issue by the International Tin Research Institute (Fraser Road, Greenford, Middlesex, UB6 7AQ, Canadian minerals yearbook 1983-84. Department of Energy, Mines and Resources Canada, Mineral Report 33. Ottawa, Canadian Government Publishing Centre, 1985. $35.40. 82 Year 1984, edited by 1.0. Jones and RM. Louthean. Kalgoorlie (Australia), Western Australian School of Mines, 1985. 100 pp. Johnson Matthey Chemicals 1984-85, issued by Matthey Catalogue Sales (Orchard Road, Royston, Hertfordshire SG8 SHE, England). 416 pp. South Africa's mineral industry 1984. Johannesburg, Minerals Bureau, 1985. 190 pp. Coal 1985. Operating and developing coal mines in the Republic of South Africa. Johannesburg, Minerals Bureau, Directory 2/8S. 1985. 72 pp. Gold 1985. Operating gold mines and gold recovery plants in the Republic of South Africa. Johannesburg, Minerals Bureau, Directory 3/8S. 98 pp. 3. New journal Pergamon Press, New York, have announced the publication of a new quarterly known as the International Journal of Plasticity. 4. Mintek reports Report M93D Hydrochloric acid leaching and low-temperature roasting of tin-tungsten concentrates from Van Roois Vley. (First issued April 1983.) Report M99D The upgrading of coarse kyanite crystals. (First issued Report M105D The development and installation of a microcomputer based data logger, and the analysis and evaluation of data. (First issued July 1983.) Report M109D The remelting ofsi/iconfines. (First issued July 1983.) Report M180 An assessment of available corrosion inhibitors for the reticulation systems of South African gold mines. Report MW1 Quantitative assessments of abrasive and impactive wear from ball-size distributions in rotary mills.

Jan 1, 1985

By S. Stuurman

Inorganic acids such as sulphuric acid have found use together with certain reducing agents in leaching of copper-cobalt oxide ores. These reagents are not ideal due to the adverse effect the inorganic acids generally have on the environment and the high costs of the reducing agents. In this study a copper-cobalt oxide ore from the Central African Copperbelt was leached in two different environments; sulphuric acid in conjunction with hydrogen peroxide as a reducing agent and tartaric acid. The effects of acid concentration, reducing agent concentration, and temperature were independently determined for both leaching environments. The sulphuric acid concentration was varied between 0.4 M and 1.2 M and the concentration of hydrogen peroxide between 4.0 M and 6.5 M, while the tartaric acid concentration was varied between 0.15 M and 0.35 M. The temperature was varied between 20°C and 50°C. The results showed that the extraction of both copper and cobalt increased with sulphuric acid concentration, reaching a peak at approximately 0.8 M and then decreasing at higher acid concentrations. A similar increase and decrease in metal extraction was observed when the reducing agent was increased. In leaching with tartaric acid, the extraction of cobalt was much higher than that of copper, although extraction of both metals increased with acid concentration. Additions of small amounts of hydrogen peroxide were found to increase cobalt extraction in tartaric acid but had a minimal effect on copper. An increase in the solution temperature had a significant effect in the organic acid environment, with the effect on cobalt extraction being much more pronounced than on copper.

Jan 1, 2014

By K. N. Karparov

The stress state on two slope profiles overlying an inclined surface with layer inclination of 50 and 150 are investigated. It is demonstrated that the induced stress state in an imbedded weak layer, exposed at the base of the slope, forms a zone of induced tensile vertical and horizontal stresses, which can lead to failure. The zone length depends on the slope angle and the angle of the inclined layers. L’état des contraintes sur deux profils en pente en superposition sur une surface inclinée avec une inclinaison de couche de 5o et 15o est étudié. L’étude présente démontre que l’état induit des contraintes dans une couche faible insérée, exposée au bas de la pente, forme une zone de contraintes de traction induites horizontales et verticales, qui peut amener à la rupture. La longueur de la zone dépend de l’angle de la pente et l’angle des couches inclinées. Die Druckvorkommnisse zweier Hangprofile auf einer schrägen Fläche mit einer Schichtneigung von 5º und 15º wurden untersucht. Es zeigte sich, dass die induzierten Druckvorkommnisse in einer eingebetteten schwachen Schicht, die am Hangfuße offen liegt, einen Gürtel induzierter vertikaler und horizontaler Zugkräfte bildet, die zum Zusammenbruch führen können. Die Gürtellänge ist von der Neigung des Hanges und der Neigung der schrägen Schichten abhängig.

Jan 1, 2003

By M. F. Dawson, S. B. Davis

SYNOPSIS This paper describes the size reduction of limestone smaller than 1 mm by attrition grinding, using quartz (1 to 3 mm) as the grinding medium in a laboratory rig. The ore and grinding medium were closely sized fractions, and the particle size of the grinding medium was at least three sizes larger than that of the ore. Batch tests showed that the size reduction of the feed followed two first-order rate processes: one for an apparently fast-breaking ore fraction, and a slower one for most of the ore (86 per cent). The production of fines (material smaller than 10 µm) followed a zero-order rate equation. Continuous runs showed that the process could be modelled as a perfectly mixed system provided that the discharge screen did not selectively retain coarser particles of ore. The ratio of medium to ore (both by mass and by volume) was found to have a significant effect, the most energy¬efficient grinding occurring at ratios between 1 and 2. The solids content of the slurry also had a significant effect, the greatest efficiency being obtained at 50 to 65 per cent solids (by mass). Within these energy-efficient ranges of medium-to-ore and solids content, the lower values resulted in maximum feed breakage and the higher values in maximum fines production. The most important factor in the breakage of feed was the difference in the particle size of the grinding medium and the ore; the amount of ore broken out of the feed size for a given energy input was found to increase linearly with the difference between the size of the grinding medium and that of the ore up to 2 mm. The production of fines increased similarly, but only up to a difference of about 1,2 mm, when it levelled off at about 5 kg/kW ? h. The mechanism proposed for attritioning is mainly the abrasion of 1 µm planes of limestone along the crystal axes, with some fracturing along existing lines of weakness. The energy consumption of nearly 200 kW ? h per ton of product smaller than 10 µm appears to be higher than that in other types of milling. It is concluded that the value of attrition milling lies in its selectivity; in this work, only the softer limestone and virtually none of the hard quartz grinding medium was comminuted.

Jan 1, 1989

By S. T. L. Harrison, M. A. Fagan-Endres, M. D. Odidi

This paper investigated the ability of eight common hydrodynamic models – tanks in series (TIS); three compartmental model configurations (Comp-1, Comp-2 and Comp-3); advection dispersion (AD); piston exchange (PE); piston exchange-diffusion variant (PE-D) and piston dispersion exchange (PDE) – to simulate residence time distribution (RTD) data generated from tracer tests conducted on a packed bed composed of different size fractions of malachite ore. The chosen materials were packed into 0.1 m internal diameter columns to a depth of 0.155 m and drip irrigated at 5.11 L/ m2.h. The four size fractions tested were: 1 – 2 mm, 2 – 2.8 mm, 4.75 – 5.6 mm and 13.6 – 16 mm. Step-up tracer tests were conducted using potassium chloride. The results showed that an increase in the particle size of the malachite ore had little effect on overall bed porosity but resulted in significantly lower values of liquid holdup. Two of the monoporosity models tested, TIS and Comp-2, were the most affected by the changes in bed size fraction due to their inherent inability to cope with high degrees of non-ideal flow present in the larger particle systems. The dual porosity models performed relatively better with the dominant trend being a reduction in dynamic to total liquid holdup as particle size increased. Of all the models tested, the PDE and TIS models were the best and worst performers respectively, with R2 values averaging at 0.997 and 0.679 across all experiments respectively. Though the Comp-1, Comp-3 and PE-D models also performed well, the addition of the dispersion coefficient to take the axial spread of fluid molecules into account added a layer of complexity that allowed the PDE model to perform relatively better than the other dual porosity models. Keywords: Heap leaching, packing material, hydrodynamics, malachite, PSD, modelling

Jan 1, 2020