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By B. Ndlovu

The world mineral industry has over the years experienced growth in the production of nickel (Ni) due to its use not only in the catalytic industry but mainly also to its demand in the stainless steel production industry. Hence there is a need to produce more pure and marketable grades of Ni through the use of efficient purification routes such as solvent extraction. The V10-LIX®84-IC system resulted in nickel (Ni) extraction isotherm shifting to lower pH levels. The pH window of opportunity for the extraction of Ni subsequently increased in solution containing magnesium (Mg) and calcium (Ca) even though the system also resulted in slight shifts to less positive pH values for Mg and Ca curves. Results showed a synergistic effect of LIX®84-IC when added to V10 for all elements, Ni, Mg and Ca. The pH50 values for elements Ni, Mg and Ca in the V10-LIX®84-IC system were 2.95, 8.10 and 7.70 respectively. Comparing results obtained when using V10 alone produced ?pH50 for Ni, Mg and Ca being 3.35, 0.15 and 0.70 respectively, which was a confirmation of the synergistic shifts for all the elements. The ?pH50 (Mg-Ni)value was 1.95 with no synergism and 5.15 with synergism and that for ?pH50 (Ca-Ni)was 2.10 with no synergism and 4.75 with synergism. This showed that the Ni-Mg separation factor was relatively larger than the Ni-Ca. Improved loading and stripping kinetics were also observed. Keywords: Nickel solvent extraction separation, magnesium, calcium, versatic 10 acid and LIX®84-IC.

Jan 1, 2008

By F. T. Cawood

Inauguration of the new political dispensation in South Africa in 1994 initiated a dynamic shift in the ownership, management and development of the country’s affluent mineral heritage. The process of substituting the old South African regime with a new equitable system, started soon after the 1994 election of the African National Congress (ANC) to parliament. The Congress’ Freedom Charter revealed the intent of the new dispensation when it called for radical transformation of mineral development. However, since 1955 there have been important changes affecting the rules of mineral development. These are: •Firstly, a drastic change in politics ushered in by negotiation, a spirit of reconciliation and a desire to settle disputes peacefully •Secondly, the globalization of the South African mining industry in tandem with the opening of domestic mineral resources to foreign capitalists; and •Thirdly, the introduction of sustainable development as a holistic approach to mineral development in order to replace traditional narrow-minded environmental management. Each of these significantly shaped the new mineral investment environment of South Africa. This paper represents a summary of the historical developments leading to the current Mineral and Petroleum Resources Development Act No. 28 of 2002, its Regulations, the much-publicised Broad-Based Socio-Economic Empowerment Charter and its associated Scorecard.

Jan 1, 2003

By J. M. Richards

For most of the 20th century optical petrography has been the primary petrological and mineralogical tool used to characterize coal. The development of quantitative SEM-based techniques, e.g. QEMSCAN®, for coal began only about a decade ago. The application of these techniques for coal lagged behind other commodities, but they are currently being developed with the aim to provide ?one complete analysis? for coal. Quantitative SEM-based techniques are supplemented by quantitative X-ray diffraction (XRD). Recent indications are that these more modern techniques cannot replace the ?standard? petrographic and chemical evaluations, but rather complement them where and when required. The great advantage of quantitative SEM-based techniques is that they are very rapid, with the result that large volumes of samples can be processed on a routine basis. This is ideal for coal type identification, since the results can be used in the creation of ?intelligent? composites. This can lead to the more speedy evaluation of coal deposits by reducing the number of samples on which detailed metallurgical and characterization test work is required, without an increase in the overall statistical error of the resource model. Coal petrography, however, remains important for the prediction of the coking characteristics of certain coals and coal products. As a consequence it is therefore important that any coal laboratory be able to produce data with confidence. This requires strict quality control and assurance protocols that adhere to international standards. Keywords coal petrography, coking strength, scanning electron microscopy, QEMSCAN®.

Nov 1, 2013

By J. Golamnejad

This paper attempts to model long-term production scheduling problems by chance constrained binary integer programming in a stochastic environment. This stochastic model is set up to account for ore block grade uncertainty. The probability distribution function of grade in each block is used as a stochastic input to the optimization model. This distribution function in each block should be determined using a Geostatistical Simulation approach. The deterministic equivalents of these chance constraints are then achieved, which are in the form of nonlinear in binary variables. A confidence level at which it is desired that the uncertain constraints holds, is specified in each scheduling period. Rather than the previous risk-based model, this formulation will yield schedules with a high chance of achieving planned production targets while maximizes the expectation of net present value and minimizing the variance function simultaneously. Using this method, the grade uncertainty is integrated explicitly into the optimization process.

Jan 1, 2006

By H. Hurkchand

Background: A cross-sectional study was conducted in November2001 to establish the prevalence rates of Human Immunodeficiency Virus (HIV) and sexually transmitted infections (STIs) (Chlamydia trachomatis and Neisseria gonorrhoea) in a coalmining town in Mpumalanga. Methods: 155 adults were recruited (79 males and 76 females), by holding community meetings, and by door-to-door recruitment. Saliva and urine specimens were collected for the analysis of HIV and STI prevalence, respectively. Results: The mean age for males was 31.35 years (min = 19 yrs and max = 50 yrs) and the mean age of the female participants was31.90 years (min = 17 yrs, max = 49 yrs). The prevalence of HIV was found to be 22.78% [95% CI (14.09?33.59)] in the males vs. 47.37%[95% CI (35.79?55.16)] in the females, [p = 0.001, OR = 3.05, 95%CI(1.49?6.26)]. The prevalence of C. trachomatis was 7.90% [95% CI(2.95?16.39)] in the males vs. 12.86% [95% CI (6.05?23.00)] in the females, p = 0.324. The prevalence of N. gonorrhoea was 3.79%[95% CI (0.79?1.08)] in the males vs. 9.86% [95% CI (4.06?19.26)]in the females, p = 0.137. HIV was significantly associated with C. trachomatis, [p = 0.032, OR = 3.18, 95% CI (1.04?9.72)], but was not significant when stratified by gender. HIV was not significantly associated with N. gonorrhoea (p = 0.072) but it was significantly associated when stratified by gender, p = 0.001 for females. There were no significant associations between HIV and age (p = 0.408), even upon stratification by gender. Conclusions: HIV prevalence in this community is high, and corresponds to national figures. However, the prevalence of STIs is surprisingly low as it would be expected to be high in a migrant population. Although communities are exposed to expanding peer-education activities that encourage behaviour change, the prevalence of HIV in this group. There is an urgent need for interventions designed to treat or prevent HIV infection in women generally and in women at high risk. Keywords: HIV prevalence, STI prevalence, antenatal, mining

Jan 1, 2005

By J. A. Caldwell, G. E. Blight

The metropolitan area of the Witwatersrand has grown up around the Witwatersrand gold mines. Most of the mines have now been abandoned, but deposits of waste material remain and have been surrounded, and in some instances covered, by urban and industrial sprawl. This paper describes the development of geotechnical measures for the abatement of air and water pollution from abandoned gold-residue dams in the Witwatersrand area. The measures include the stabilization of the surfaces of the dams to prevent wind and water erosion, the terracing of slopes to minimize erosion, and the construction of catchment walls and dams. The measures were developed in terms of the set of guidelines for environmental protection adopted by the Chamber of Mines of South Africa in 1979.

Jan 1, 1983

By M. Moys

The use of temperature measurements for unusual applications in the analysis and control of column flotation and milling is discussed. This is followed by a review of some of the authors current research in the application of the discrete element method to the modelling of particulate processes, specifically milling, fluidized beds and chute flow.

Jan 1, 2005

By G. Westcott

Impala Platinum, the second largest platinum producer in the world, is embarking on a major expansion strategy to increase its platinum output from 1.95 moz to 2.8 moz by the year 2008. The smelter complex, situated in Rustenburg, will undergo substantial modifications, and will require a solution to the capture and treatment of the smelter off-gases and dust produced during smelting and converting operations. One of the solutions explored was an integrated approach, where all the off-gases from both the primary smelting electric furnaces and the converter operations are routed to a large central gas cleaning and double catalysis, double absorption acid plant. In-line sulphur burning, utilizing a highly flexible LURO1spin cup burner with a turn down ratio of 50%, ensures that the acid plant operates independently of operating conditions at the smelter complex.

Jan 1, 2007

By R. Zivojinovic, S. Vujic, T. Tanaskovic

The problem of determining the optimum exploitation life of machinery, namely the optimum time for machinery and equipment replacement, represents a complex and highly responsible engineering task. Taking into consideration the situation prevailing at coal pit mines in Yugoslavia, the tasks of this class are very complex and difficult. To make a decision on replacement of capital equipment and machinery, such as bucket wheel excavators within the mentioned systems, understands a management task of utmost responsibility. It requires high professional and analytical knowledge as well as the reliable arguments, based on multidisciplinary professional approach. In this paper, the authors present their views on the problem of establishing the optimum exploitation life of bucket wheel excavators, offering an algorithm, based on dynamic programming, as a solution. Keywords: Bucket wheel excavators, exploitation life of machinery, optimization, operations research, theory of replacement, dynamic programming

Jan 1, 2003

By Didier Kasongo NYEMBWE

The paper circumscribes the base metal casting industry in Southern Africa. It essentially consists in the founding of copper and zinc alloys. The challenge related to the scarcity and the unaffordable quality patterns and dies faced by the industry is discussed. New manufacturing technologies for foundry tooling called Rapid Prototyping that can possibly be used to alleviate the above mentioned challenge are then presented and their benefits assessed.

Jan 1, 2007

By B. D. Paphane

Since the commissioning of the Tati Hydrometallurgical Demonstration Plant (HDP), which produces Ni and Cu cathodes as well as Co salt from sulphide concentrate employing Activox® technology for leaching, no kinetic data has been generated from the plant under normal operating conditions, from start-up to steady state. Therefore, this study seeks to determine the rate of reactions in the leaching circuit with a view to obtaining kinetic data for the system under the current operating conditions. Within the five-compartment autoclave operating at temperatures of 105°C to 110°C and 1100 kPa pressure, the extraction of Ni, Cu, and Co ions into solution is achieved through the oxidation of the sulphide concentrate using approximately 50 kg H2SO4 per ton, 10 kg NaCl per ton, and 1.21 kg O2 per kilogram of S2-. The autoclave reactions showed complex kinetics, with the reactions proceeding via some intermediate(s) before the formation of products. The results suggest that the reactions were dependent on the size of the metal ion of interest and the concentrations of the metal ions in the Tati concentrate as well as in chloride leaching. The order of the leaching rate constants was Fe2+ > Cu2+ > Ni2+ > Co2+ in all the compartments studied. The rates of leaching were also found to decrease as the concentrate moves from compartment 1 to compartment 4. For compartments 1 to 3, leaching was observed to be preceded by dilution of the repulp liquor (copper raffinate). The leaching rate for compartment 5 was slightly lower than that of compartment 1 but higher than the rates of compartments 2, 3, and 4 for all the metals studied. Keywords kinetics, hydrometallurgical plant, Activox

Jun 1, 2013

By C. F. Vos, J. D. Miller, J. C. Davidtz

Small replacements of C12-trithiocarbonate (C12-TTC) for dithiocarbonate (DTC)/dithiophosphate(DTP) in a reagent suite for the flotation of platinum group metals (PGM) have significantly improved the rejection of gangue. Coupled to this is an improvement in kinetics, grade and recovery of PGMs. In a pilot-plant trial, after a 5 mole per cent replacement of the current DTC/DTP collector combination by C12-TTC, large opaque bubbles were replaced by small clear ones. In addition, a similar flotation response was realized with one-third of the current depressant dosage. During a preliminary plant trial on underground UG2 ore, the initial rougher concentrates were characterized by higher PGM concentrate grades and this was in part due to improved chromite rejection. The concentrate produced from the TTC trial also exhibited a much finer particle size distribution. The overall circuit performance, which included secondary regrind and flotation, showed an increase in concentrate grade of approximately 44% while the tailings grade remained unchanged

Jan 1, 2006

By Elizma Ford, Vincent Sithole

"Two shortened test procedures for estimating the Bond ball work index are compared for suitability of use on Zambian/DRC-type copper–cobalt ores. The first procedure is based on a batch milling test while the second procedure is based on a limited locked-cycle test. Both procedures were conducted using a standard Bond test mill. INTRODUCTION The Bond ball work index is widely used in the field of minerals processing as an indicator of ore grindability. The work index is determined by means of a locked-cycle test procedure that typically requires seven to eight cycles to stabilise at a re-circulating load of 250%. A typical test requires between three to four kilogram of ore sample and around eight hours of operator time. For geometallurgical test work applications, where a large number of variability samples are to be tested, it would be highly beneficial to use a test procedure that requires less sample mass and operator time. Certain test work laboratories, for example SGS and JK Tech, are already offering various types of shortened test procedures for estimating the Bond ball work index. This paper discusses a comparison of two shortened test procedures that were evaluated for suitability of use on Zambian/DRC-type copper–cobalt ores. EXPERIMENTAL Test Procedure 1 – Batch Milling The first test procedure is derived from a batch milling approach proposed by the University of Hacettepe (Aksani, 2000). Some modifications were, however, made to the data analysis method from that originally proposed. During this test procedure, a 700 mL volume of sample is milled in a standard Bond test mill for a pre-determined number of revolutions. The feed and product particle size distributions are measured for each test. These results are then used to back-calculate a cumulative breakage rate parameter (k) for each particle size, according to the following formula:"

Jan 1, 2015

By T. H. Yang, K. K. Lee, Z. Z. Liang, C. A. Tang, L. C. Li, Y. Tsui, L. G. Tham

Abstract: A series of numerical tests of hydraulic fracturing in heterogeneous rocks were performed to investigate the influence of pore pressure magnitude and gradient on initiation and propagation of tensile fractures. The numerical tests were run with a Rock Failure Process Analysis code, F-RFPA2D, incorporated with a Flow-Stress-Damage coupling model (FSD). To investigate the influence of pore pressure magnitude on fracture behaviour, “pinch-off” breaking tests, originally employed by Bridgeman to investigate the effective stress law for tensile fracture in a uniform pore pressure field, were numerically modelled. In another numerical test, a double-notched sample, with fluid pressure in one notch while keeping the other one open to the atmosphere, is numerically extended to investigate how the fluid flow direction or the pore pressure gradient will influence the fracture behaviour. The simulation results show that fracture is strongly influenced by both pore pressure magnitude and pore pressure gradient. Keywords: seepage mechanics; heterogeneous; pore pressure; numerical simulation; failure process ZUSAMMENFASSUNG: Um den Einfluss der Wasserdruckgroesse der Oeffnung und der Porisitaet auf den Bruchentstanden und Verbreiten der Tension von Gebirgen zu beurteilen, wurde viele nummerische Pruefungen auf den hydraulischen Bruch in dem Gebirgen aufgenommen. Diese Pruefungen wurden mittels der Analyse- Software F-RFPA2D und Flow-stress-Damage Coupling model ( FSD) durchgefuehrt. Um den Einfluess der Wasserdruckgroesse der Oeffnung auf den Bruch zu beurteilen, wurden auch Bruchpruefung und nummerische Analogexperimenten gemacht, und dadurch wurde die ganze Phase der Bruchentstanden und Verbreiten wiedergezeigt, und die Ergebnissen ergeben sich, dass die Wasserdruckgroesse der Oeffnung und der Porisitaet sehr viel auf den Bruchentstanden und Verbreiten der Tension von Gebirgen beeinfluessen. Schluesselwoerter: Durchlaessigkeit , ungeleichmaessig, Wasserdruck der Oeffnung, nummerische Analog, Zerstoerungspahse Résumé : Une série de simulations numériques a été ménée pour analyser l’influence de la grandeur de la pression de pore et du gradient sur la naissance et la propagation des fractures de tensions par le biais de la simulation numérique des fractures hydroliques dans des rochers hétérogènes . Le logiciel F-RFPA (Rock Failure Process Analysis code ) intégrant FSD ( Flow-Stress-Damage coupling model ) y a été employé. Les résultats des simultations montrent tout le processus de la naissance et de la propagation des fractures sous la pression de pore. Ces résultats nous ont permis de constater que la grandeur de la pression de pore et le gradient exercent une influence importante sur la naissance des fractures dans les rochers et sur leur mode de propagation . Mots de clé : le mécanisme de transfusion ; l’hétéogénéité ; la pression de pore ; la simultation numérique ; le processus destructif

Jan 1, 2003

By J. Galloway, P. K. Hofmeyr

Obviously all mining operations require much analytical work to be carried out. This starts with exploration, becomes more stringent with the evaluation of a mineralised area and finally becomes on-going when mining operations are under way. All these phases are carried out by geologists, metallurgists and mining engineers. They require analyses to carry out their functions but usually have no involvement in the analyses themselves. Analyses are carried out at commercial laboratories or in-house analytical laboratories. In the past in South Africa the tendency was for the larger mining houses to have their own centralised laboratories for exploration samples with each mine having it?s own laboratory to meet only that mine?s requirements. The centralised laboratory maintains QC functions at the subsidiary laboratories. In other mining areas of the world there has been a strong tendency for all geological analytical requirements, especially for exploration and mining, to be carried out at commercial analytical laboratories. In recent years there has been a tendency for mines in South Africa to move in the same direction. This paper discusses the factors that need to be taken into consideration when a new laboratory is being planned and automation is an option. The planning of the laboratory at the new Langer Heinrich Uranium mine in Namibia is discussed considering these factors. 2.0 REQUIREMENTS OF A MINING ANALYTICAL LABORATORY The purpose and requirements of a mining analytical laboratory are fairly obvious and can be summarised as follows :- 1. All mining operations must have access to analytical facilities, either in-house or commercial 2. The laboratory must be able to handle all the sample types submitted by the mining operation These can be mining, exploration and/or plant samples. They can comprise solids (rocks, bore-cores), slurries and/or liquids.

Jan 1, 2007

By S. Montes

Mineral floatability is strongly connected with mineral structure and composition. The complexity of mineral surfaces has meant that few attempts have been made to understand the effect of impurities (trace elements) on the flotation process. Zeta potential technique has been extensively used to evaluate the surface charge of mineral particles. Nevertheless, those measurements consider only an average of mineral particles surface charge. The presence of fine particles and inclusions covering a mineral may influence the local reagent adsorption process, which will ultimately be reflected in the subsequent global response of the mineral froth flotation efficiency. The current work assesses the iron oxide mineral, haematite (Fe2O3). Zeta potential and streaming potential techniques were used to determine the surface charge of fine and coarser particles of haematite. Further analysis was performed to determine the point of zero charge (PZC) of the mineral. In addition, adsorption isotherms of alkyl ammonium chloride reagents with different lengths of carbon chains were carried out. It was found haematite floatability depends strongly on the isoelectric point (IEP) value, which is affected by other mineral species present at the mineral surface. Haematite floatability became significant only at relatively high tetradecyl ammonium chloride collector concentrations (concentration greater than 4 10-4M), which does not happen with other oxides such as quartz. Unlike quartz, haematite develops a low surface charge over a wide range of pH, disabling all long-range attractive interactions between the mineral and the collector. Therefore, hydrophobic chain interaction is probably the most likely mechanism acting to promote collector adsorption and enhance further floatability. Diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to suggest a possible mechanism to understand the sequence of collector adsorption and the effect of trace species on it. Keywords: floatability, haematite, adsorption, electrochemistry, zeta potential.

Jan 1, 2007

A single aggregate mix design was developed based on a slag/Portland binder blend and crusher sand. The primary design criterion, after performance, was the fluidity of the shotcrete and concrete product to ensure compatibility with existing manufacturing and shotcrete equipment as well as the pipeline transport system Cullinan Diamond Mine was investigating. Initial work had determined an optimum slag/Portland to aggregate ratio while retaining a water to slag/Portland binder ratio of approximately 0.4 to maintain the flowability of the product. A super-plasticizer was used to further increase the flowability of the product as opposed to increasing the water content. Finally a polypropylene reinforcement fibre was included in the wet shotcrete product to improve the energy absorption characteristics of the shotcrete. Previous work on the strength development of the slag/Portland based shotcretes and concretes suggests that strength class based on the EN 206 specification is C40/50 while the toughness classification based on the EFNARC plate test is c, or greater than 1000 joules1. Typically, Cullinan Diamond Mine wanted a shotcrete with a uniaxial compressive cube strength of 45 MPa and an energy absorption, based on the EFNARC plate test, in excess of 700 joules. This is an EN 206 strength class of C36/45 requiring a uniaxial compressive core strength of 30.5 MPa and a toughness classification of b1. In addition to the shotcrete development, Cullinan Diamond Mine required concrete products with a compressive strength range of between 25 and 60 Mpa for differing construction operations underground to be manufactured from the same mix design and raw materials as for the shotcrete. Finally, Cullinan Diamond Mine carries out extensive dry shotcrete operations and an investigation into the possibility of using the single aggregate mix design for dry shotcreting was also entered into. This paper presents data that indicates that, under the terms of reference, a wet and dry shotcrete and concrete product appears to be possible from a single aggregate less than 6.7 mm in size, and that a slag/Portland binder is suitable for use as the hydraulic binder in all the products, and that the necessary performance parameters of strength and energy absorption can be achieved.

Jan 1, 2006

By B. Amadei, F. Tonon

Rock stress measurement is cast in the more general context of the determination of boundary conditions for rock engineering. A study on the effect of elastic anisotropy on underground excavations reveals that this effect is actually controlled by the imposed boundary conditions. Applications to tunneling and to the Underground Research Laboratory (URL), Canada, exemplify a procedure for boundary condition estimation formerly developed by the authors. The procedure displayed fast convergence despite the complex geometry, and the high degree of non-linearity of the models. In the URL application, the 3-D model was able to completely reproduce the complex measured stress pattern, and the 90° rotation of the principal in situ stresses with depth. In order to reliably estimate the boundary conditions reproducing the current in situ state of stress, response measurements of the rock mass to current disturbances are necessary as input data. La mesure des contraintes in situ tombe dans le domaine général de la détermination des conditions aux limites pour les problèmes de mécanique des roches. Une étude sur le rôle de l’anisotropie élastique sur les excavations souterraines montre que ce rôle est contrôlé par les conditions aux limites qui sont imposées. L’application aux tunnels et au Laboratoire Souterrain de Recherche (URL) au Canada, nous permet de présenter une méthode de détermination des conditions aux limites. La méthode converge rapidement bien que le géométrie soit complexe et que le problème soit non-linéaire. Pour le URL, le modèle 3D est capable de reproduire la distribution des contraintes qui ont été mesurées ainsi que la rotation de 90 degrés des contraintes in situ avec la profondeur. Afin de déterminer avec précision les conditions aux limites responsables pour la distribution actuelle des contraintes, la réponse du massif rocheux doit être connue et mesurée. In der Felsentechnik sind die Spannungsmessungen in Gestein an die Bestimmung der Randbedingungen gebunden. Eine Studie legt dar, dass der Effekt elastischer Anisotropie in unterirdischen Aushoehlungen von den Randbedingungen kontrolliert ist. Eine von den Authoren entwickelte Methode zur Bestimmung der Randbedingungen wird an Beispielen im Tunnelbau und im Underground Research Laboratory (URL) in Kanada illustriert. Auch bei komplexer Geometrie und einem hohen Grad an Nicht-Linearitaet zeigt diese Methode ein schnelles Konvergenzverhalten. Ein 3D-Model und dessen 90° Drehung der lokalen Hauptspannungen mit der Tiefe, kann bei einer URL Anwendung vollstaendig reproduziert werden. Um mit dieser Methode die Randbedingungen zuverlaessig abschaetzen zu koennen, werden der gegenwaertige lokale Spannungszustand sowie die Antwort des Gesteins und die resultierenden Stoerungen als Eingabedaten benoetigt.

Jan 1, 2003

By D. deV. van der Spuy

A procedure for optimizing the secondary cooling zone of continuous casters is proposed and illustrated by a billet caster example. The procedure consists of quantifying deviations from the required conditions of the secondary cooling zone?as far as temperatures, metallurgical length and reheating are concerned?by means of a ?cost function?. The optimal spray settings are then found by minimizing the total ?cost?. The billet caster examples serve to emphasize the importance of specifying the required conditions in a consistent manner. Some envisaged practical limitations of this approach are discussed.

Jan 1, 1999

By R. Minango

Solvent extraction of Cu from acidic leach, using an oxime extractant, e.g. LIX 984 or Acorga is a well-known and establishedprocess. As the process advances, Cu is extracted to the solvent and is replaced by H+in the aqueous phase. At high acidity the distribution coefficient of Cu between the solvent and the aqueous phase decreases, and eventually a relatively high concentration of Cu remains in the raffinate, regardless of the number of equilibrium stages. In many processes this phenomenon is immaterial, as the raffinate returns to the leaching and no copper is lost. But when the copper raffinate is used for processing of additional metals, minimal concentration of Cu in the raffinate is essential for an effective process. The recommended process includes three steps: SX-1?standard extraction of Cu with oxime. The resulting raffinate contains about 6?8 g/lCu and 50 g/lH2SO4. SX-N?Extraction of most of the acid into an amine-based solvent, and stripping it with a base, e.g. aqueous ammonia, caustic, Na2CO3etc. The extraction removes no metals, but decreases the concentration of acid from 50 to10 g/l. SX-2?Extraction of the neutralized solution once more with oxime, to remove the residual copper. Such a process enables one to get down to 100?150 ppm Cu in the final raffinate. This process was developed and tested in the R&D facility at Chambishi Metals plc, by a joint team of Chambishi & Bateman, using Cognis LIX 984N and real solutions from the plant. In the laboratory the equilibrium isotherms for SX-1, SX-2 and the neutralization were developed. Computer simulation of the results showed that the optimal configuration is two stages for both extraction and stripping for SX-1. For SX2, 2?3 stages of extraction and two stages of stripping are needed. The stripping stages may be common to both SX-1 and SX-2. The neutralization of SX1 raffinate was tested both by conventional precipitation with lime and by extraction with alamine-based solvent extraction and stripping with a solution of 10% NaOH. For the SX-N only one stage was needed for both the extraction and stripping. The bench scale pilot plant was run for both SX-1 and SX-2. The results were very similar to the simulated ones, and the configuration of 2E2S for SX-1 and 3E2S for SX 2 delivered the required raffinate with less than 150 ppm Cu.

Jan 1, 2005