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By L. Bircumshaw

Paper written on project work carried out in partial fulfilment of BSc (Eng) (Chemical) degree This paper details the formulation of a mathematical model for the simulation of a primary bioleach reactor, with specific reference to the leaching of pyrite. The model is based on the direct reaction mechanism, where the leaching of pyrite is said to occur via a two-step process. The process involves the formation of ferrous?iron through the chemical leaching of pyrite and subsequent bacterial oxidation of ferrous-iron back into ferric-iron. At steady state the rate of chemical leaching and bacterial oxidation are linked by the ratio of ferrous-iron to ferric-iron in solution. The extent of conversion of pyrite in the reactor system is described using the segregated flow model, with the exit age distribution of the solid phase being described by the Tanks-in-Series model. The final phase in model formulation involves the inclusion of steady state material balances on the bacteria and fluid phase components. The model is compared to pilot plant data and laboratory data for two different types of pyrite concentrates, with simulation results showing that the model is in good agreement with the data. Author key words: Bioleaching; pyrite; primary reactor; modeling; segregated-flow model; tanks-in series model.

Jan 1, 2006

By R. H. Walton

"In recent years the recovery of copper from low grade oxide ores has received widespread attention. The cost of treating such ores using conventional technology, such as milling and flotation, is frequently prohibitively high and copper recovery is generally low. The introduction of heap leaching, solvent extraction (SX) and electrowinning (EW) has resulted in high recoveries, good copper cathode quality and low production costs. This technology has now been successfully applied on a worldwide basis.This paper reviews the various process and design options and gives approximate capital and operating costs for a 1.0% copper ore.INTRODUCTIONAs a result of the low copper prices that prevailed for much of the last two decades, aggressive attempts were made by the industry to cut operating costs. Under such circumstances heap leaching, solvent extraction and electrowinning, to recover low cost copper from oxide ores, has received particular attention and ultimately widespread acceptance.Low grade copper ore (typically containing less than 1.0% Cu), which could not be economically treated by other methods, is placed on heaps and leached with dilute solutions of sulphuric acid. The copper rich, pregnant solution, drains from the heap into a collecting pond and is pumped to a solvent extraction plant where it is purified and upgraded. The resulting solution, termed the pregnant electrolyte, passes to the electrowinning section where the copper is recovered as high grade cathodes and sulphuric acid is regenerated, (Figure 1).This paper specifically describes the processing of copper oxides. Other copper minerals such as chalcocite and chrysocolla are also leached by dilute solutions of sulphuric acid. In practice the oxide minerals are frequently associated to varying degrees with less easily leached sulphides, such as chalcopyrite. In some cases, once the oxidized capping of the ore body is removed, the oxides are totally replaced by more refractory sulphides. Under these circumstances the leaching recovery is significantly reduced. However the principles described here for solvent extraction and electrowinning are also applicable to solutions received from heaps containing sulphide minerals, which are leached more slowly and involve bacterially induced reactions."

Jan 1, 1990

By Alexandra Kozak, Rodrigo Costa, Bob Fukuhara

"The Jacobina project in Bahia, Brazil commenced operations in 2004 with a design capacity of 4,200 tpd. A project development plan to increase plant capacity to 6,500 tpd will be discussed. The project included an evaluation of the existing circuit and addressed bottlenecks in the crushing, milling, sedimentation, leaching and tailings transport. These circuits and the methodology used to provide higher capacity will be presented.INTRODUCTIONThe Jacobina mine is located in the state of Bahia in northeastern Brazil approximately 330 km northwest of the state capital city of Salvador and 9 km from the town of Jacobina. The Jacobina Mine (Figure 1) is owned by Jacobina Mineração e Comércio, a wholly owned subsidiary of Yamana Gold Inc.The gold mineralization of the Jacobina mine is hosted within quartz pebble conglomerate reefs of the Serra do Córrego Formation which together with the Rio do Ouro Formation forms the Serra do Jacobina mountain chain.The Serra do Jacobina mountains have been mined for gold since the late 17th century. Since the 1970’s, the Jacobina mine has been operated by Anglo American, Williams Resources Inc., Desert Sun Mining Inc. The mine is currently owned by Yamana Gold Inc.In December of 1998, operations at Jacobina were suspended and the property was placed under care and maintenance. Desert Sun Mining Inc. began exploring the property in 2002 and eventually purchased the Jacobina mine in 2003. In 2003, a feasibility study was completed that evaluated the economics of re-developing the mining operations and expanding gold production. In 2004, refurbishment and re-development of the mining operations began and the milling facility throughput capacity was expanded from 1.08 to 1.512 Mtpy (3,000 to 4,200 tpd). The milling operations were commissioned in the 1st quarter of 2005 and commercial production was declared 1 July 2005. In April 2006, Yamana Gold Inc. acquired the Jacobina mine through its acquisition of Desert Sun Mining Inc."

Jan 1, 2008

By L. S. Jeffrey

Estimates for South Africa?s coal recoverable reserves made in 1999range from nine to 59 billion tons; latest estimates by the Minerals Bureau suggest that 33 billion tons is a more likely figure. As much as 70% of that coal is located in the Waterberg, Witbank, and Highveld coalfields, as well as lesser amounts in the Ermelo, Free State and Springbok Flats coalfields. However, the Witbank and Highveld coalfields are approaching exhaustion (estimated 9 billion tons of recoverable coal remaining in each), while the coal quality or mining conditions in the Waterberg, Free State and Springbok Flats coalfields are significant barriers to immediate, conventional exploitation. New extraction technologies, technologies exploiting the energy content of the coal in situ, as well as suitable uses and markets for low-grade, high-ash coal are required before the country can utilize its admittedly vast coal resources. Major challenges for exploiting some Limpopo province coalfields are severe water shortages, insufficiently developed infrastructure, fragile environments and poor roof conditions due to the depth and complex geology. In the Central Basin (Witbank, Highveld and Ermelo coalfields) technical innovations for thin seam extraction, economic mining of both pillar coal and intrusion-fragmented resource blocks and the utilization of lower-grade coals are required. The success of the fluidized bed combustion technology is necessary to utilize the low-grade coals of the Free State and Molteno coalfields, while environmental exemption for past problems, together with strategies for mining small, disjointed thin-seam resource blocks, is required in KwaZulu-Natal. Clean coal technologies, coal cost and quality, environmental considerations, sustainable development, the growth of the South African economy and Government?s regulation of the electricity industry are the main challenges to the continued use of coal as South Africa?s primary energy source.

Jan 1, 2005

In this study, the effects of slag compositions, slag amount, temperature, and carbon content of steel on the manganese and phosphorus distribution ratios during converter steelmaking were analysed using the classical regular solution theory, and industrial tests were performed using two 80 t top-and-bottom combined blown converters (duplex melting process). The results indicate that the slag amount, temperature, and carbon content in steel are the main factors affecting the manganese yield when converter slag compositions remain constant. The FeO content of the slag has a strong impact on the manganese distribution ratio, while the slag basicity and MgO content have no obvious effect. The calculations and experimental results show that the phosphorus distribution ratio increases sharply with increasing slag basicity R, but then decreases with the increase of MgO and MnO contents in the slag. The final slag in converter steelmaking should have the following characteristics: 3.5 < R < 4.5, 15% < (FeO) < 20%, and 6% < (MgO) < 8%. The slag amount should be controlled appropriately at the same time. The results of this investigation would be useful in deciding on the application of manganese ore in alloying and identifying the slagging regime in converter steelmaking.

Jan 1, 2014

By Hiroyuki Matsuura

The effects of P20S or Na20 addition on the reaction rate of CO2 dissociation on the surface of FexO-base molten oxides was investigated at 1773K by isotope exchange methodl-6_ The rate constant decreased with increasing P20S content of molten oxides and the residual rate constant was observed at high P20S content On the other hand, the rate constant increased with increasing Na2O content for FexO-SiO2 melts. The rate constant was evaluated by the composition of oxides and the rate controlling step of CO2 dissociation was discussed.

Jan 1, 2003

By Stig Eriksson

In Switzerland two major railway systems as shown below in Figure 1 has recently been completed or is under construction: ¦Lötschberg, south of Bern which was commissioned in 2007 ¦Gotthard, south of Zurich which is scheduled to be commissioned in 2016The aim is to increase the transport capacity of the railway system and to transfer more transport of goods to the railway by offering transport of trailers and lorries on the new railway systems. It will have a positive environmental impact but also improve the congested traffic situation of the highways in north-south directionThe Gotthard tunnel is totally 57 km (35 mile) long and the Lötschberg tunnel is 35 km (22 mile) long. Both tunnel systems consist of two parallel single track tunnels connected with cross tunnels at every 333 m (1 093 ft). Additionally there are cross-over tunnels and caverns for installations and operation. In the Lötschberg tunnel, the majority of the excavation has been by Drill & Blast and in Gotthard tunnel the major part is being excavated by TBM.

It is well known that the electrochemical precipitation of metals from aqueous solutions is conducted by the electrochemical standard potential scale. This scale indicates the order of nobility of different metals. Consequently, the standard potential scale shows the nocivity of metals when they are present as impurities in aqueous solutions containing metals. In the hydrometallurgy of cobalt, nickel and zinc are co-deposited during cobalt electrodeposition. Nickel has almost the same chemical, physical and electro-chemical properties as cobalt. Furthermore, the electrochemical potential of nickel is relatively higher than that of cobalt. For this reason nickel is preferentially reduced at the cathode in the presence of cobalt. The presence of small amounts of zinc in solution leads to contamination of cobalt electrowon. In spite of its lower electrochemical potential in comparison to cobalt, zinc is reduced on the cathode because of its higher hydrogen-overvoltage. But, in the hydrometallurgy of zinc, small amounts of cobalt present solution will contaminate the zinc reduced at the cathode. This is easily explained by the fact that cobalt is more electropositive than zinc. The co-deposition mechanism of sulphur at the cathode is not yet well understood. Great attention has to be paid to the mechanism of co-deposition of sulphur during cobalt electrolysis. This work aimed to investigate the influence of some parameters on the co-deposition of nickel, zinc and sulphur during cobalt electrowinning. The following parameters have been investigated: Co2+concentration in the electrolyte, current density and ammonium sulphate (NH4)2SO4additions. It has been established that important nickel, zinc and sulphur co-deposition takes place at relatively low Co2+ concentration in solution. The behaviour of these elements with regard to the cathodic phenomena has been established.

Jan 1, 2005

By L. R. C. Cairncross

In this study, the general case of semi-batch precipitation of nickel hydroxide, Ni(OH)2, is modelled. In practical terms, this precipitation may occur at high ionic strengths, and therefore the model for solution chemistry requires a thermodynamic model that is applicable for these non-ideal systems. The activity coefficient model used is the ELEC-NRTL. The simulation of the solution chemistry is performed using AspenPlusTM, which is a steady-state process simulation program. This allows for rigorous evaluation of the solution speciation, and hence the degree of supersaturation which dictates the precipitation kinetics. The solution chemistry provides the basis for predicting the formation of solids. The model consists of a solution chemistry part and a solids formation part. The inputs to the model include the initial concentrations of the streams entering the reactor, kinetic parameters for the precipitation processes, and a particle size distribution obtained from experiments. The solids formation part of the model employs the method of moments for the evaluation of the population balance. The population balance accounts for total particle number, and the formation and increase in size of particles across the entire particle size range. This balance requires kinetic parameters for the processes of nucleation, growth and agglomeration. Using optimization routines inherent in AspenPlusTM, parameters for the rate of nucleation, growth and agglomeration may be extracted from experimental particle size distributions. These are then used in the model to extrapolate to other conditions. Once an understanding of the kinetics of the precipitation processes is gained, the model provides a predictive tool for optimization of these kinetics, in order to increase the overall particle size and therefore improve solid-liquid separation. The work is deemed to be significant as it sheds some light on solids formation processes involved in precipitation?including nucleation, growth and aggregation?and develops a predictive modelling tool applicable to solutions of high ionic strength. We argue that this dewatering of suspensions is affected significantly by particle size distribution and surface properties of the solids formed by precipitation. This modelling tool should facilitate the design of solids formation processes where downstream dewatering is enhanced.

Jan 1, 1997

By C. Lumley

The management of the Anglo Platinum (AP) mining technical systems (MTS) embarked upon a process of defining the strategy for the MTS department. The newly established department forms part of the greater Group Information Technology (IT). The strategic process took place within an environment that had witnessed a dramatic proliferation of IT implementations across the group within the last three years. The IT department has been structured in terms of the classical plan, build and run functions with the applications and integration streams running perpendicular across these three functions. The application stream is divided into commercial and mining technical systems with business systems integration the third stream. The mining technical systems department supports mine management to effectively gather, analyse and disseminate data relating to the ore reserve by integrating a number of strategically selected IT applications to ensure that the safety, legal and operational requirements are met. This service to business is rendered by management of a strategic outsource partner via tightly controlled service level agreements (SLAs). The framework used for creating a mining technical systems department that is empowered to add value to business was formulated using the AP value chain as both the starting point and guiding process to ensure alignment to the greater internal strategy of the business. Keywords: Platinum, Mine planning, Mining technical systems, Value chain.

Jan 1, 2003

By C. Musingwini

The South African mining industry continues to be a major source of employment at a time when at least 25 per cent of the working age population is unemployed. At the same time the industry faces a skills shortage in many of the disciplines necessary for its future health. The University of the Witwatersrand, University of Pretoria, University of Johannesburg, and University of South Africa have historically produced mining graduates for the South African mining industry with any shortfall being met by the recruitment of overseas graduates. More recently, the global shortage of engineers and other mining industry professionals has seen a reversal of this trend and a very significant emigration of well-educated and highly skilled personnel. The traditional career path for mining graduates is in production and mine management. However, there is the parallel (and possibly more pressing) need for specialized skills in such fields as ventilation, rock engineering, mine planning, mineral resource evaluation, and mineral asset valuation. Chronic shortages in these essential areas continue to hamper the development of the industry and may well frustrate its ambitions to be safe, healthy, and profitable into the future. The permeability of skills across sectorial boundaries within the mining industry requires that skills shortages in the platinum sector are not looked at in isolation, but within the context of the entire industry. This paper reviews the efforts being made by the universities, at both undergraduate and postgraduate levels, to meet the needs of the South African mining industry in terms of the required numbers and the range of specialized skills.

Jan 1, 2013

CSA mine, which is a deep level copper operation, located 12 km north of Cobar, NSW, currently uses a top down stoping method, utilising cemented hydraulic backfill (CHF) to fill and stabilise the stoping void thus assisting the extraction sequence. The stope sequence then requires development back through the CHF stope so that the necessary infrastructure for the subsequent stoping, such as raise bore pads can be sited. The primary and secondary support installed in the CHF consisted of 100 mm thick fibrecrete from floor to floor with 7 + 2.4 m long resin support tendons installed at 1.5 m ring spacing. This support system relied on the resin achieving a quality bond with the CHF, and also the fibrecrete developing early structural strength due to the use of an accelerator. In addition to the delays in the excavation turn around time, it was felt that a superior support system could be designed. Such a system was designed; risk assessed, tested underground, and trialled in selective CHF digouts, and eventually signed off as the chosen support method in CHF digouts. This paper discusses the change from a passive support system used in CHF digouts to an active support system using Swellex bolts and weld mesh, which has provided an active support system, that is superior, faster to install, reduced the excavation turn around time and is overall a cheaper support system.

Nov 25, 2010

By J. Piper

Markets and Production Beryllium (Be), an extremely light metal, is used in many specialty applications. It the lightest element in Group 2A of the periodic table, with a specific gravity of 1.85 gm/cc, and a high melting point of 12850C (Calvert, 2004). The functional properties of beryllium are stiffness, strength, dimensional stability, resistance to corrosion from acids, and electrical and thermal conductivity. The ability to reflect neutrons and transmit x-rays, makes beryllium irreplaceable in uses such as precision optical components, inertial guidance systems, and in nuclear reactors (Anon, 1993). Beryllium is used in Cu alloys to strengthen and reduce corrosion in copper wire, and in lightweight oxide ceramics that are used as heat sinks, and as electrical insulators. The market revenue of beryllium can be broken down into the seven major groups below, and are plotted on the pie chart in Figure 1 (Anon, 2005). 1.) Telecommunications & Computer 2.) Magnetic & Optical Data Storage 3.) Aerospace and Defense 4.) Automotive Electronics 5.) Industrial Components 6.) Appliance, and 7.) Other.

Jan 1, 2007

In constructing a financial model of a project significant effort is expended on capital and operating cost estimation, commodity price forecasts, and choice of discount rates while uncertainty in the primary input, the reserve, is often completely overlooked. The aim of this paper is to highlight the impact of uncertainty in the resource/reserve estimation process on the assessment of the financial performance of a project. Four qualitative processes have an impact on resource/reserve uncertainty. These stages are: 1.Ore definition 2.Geological interpretation 3.Resource estimation 4.Ore reserve estimation and mine planning. Each stage contains a number of tasks that may be considered as key performance activities (KPAs). Optimizing the manner in which these KPAs are completed can remove a great deal of uncertainty and error from the resource/reserve process. Examination of these KPAs within a company can also provide an insight to the quality of the information underlying the project. This will allow the company to identify any shortcomings in the data and to assess the resulting risks (Gilfillan, 1998). A hypothetical financial model based on a gold operation has been used to estimate the potential effect of resource/reserve uncertainty on revenue. Monte Carlo simulation has been employed to simulate a number of hypothetical scenarios: 1.a base case scenario which assumes no major errors or biases, but contains realistic margins for uncertainty that would exist in any project where work is being completed to the limit of best endeavours 2.a poor sampling scenario which assumes poor sampling practice and lack of understanding of sample preparation 3.a poor resource estimation scenario which assumes poor modelling and inappropriate choice of interpolation technique, and 4. a ?typical? scenario which represents a project where the majority of KPAs are not performed as best as they could be. The results show that realistic uncertainty ranges can generate changes in the estimate of potential revenue of plus or minus 30%.Therefore, it is important to allow for errors in these processes in any financial analysis or feasibility study. It is recommended that, when building a financial model, are view of relevant resource/reserve KPAs be carried out and appropriate ranges for uncertainty be applied to provide a range of potential outcomes. These outcomes can then be factored into the detailed cash flow analysis in order to ensure that technical uncertainty is built into financial decisions.

Jan 1, 1999

By L. B. Hales

Image analysis for feed belts and flotation has been used for over 20 years. It has been shown to aid in the modelling and optimization of Sag Mill circuits, and any improvements in the image analysis result in improvements in the model for control. Using a laser to measure the height-profile of rocks on the conveyor has been shown to increase the accuracy of the size classification. We have developed a system using two cameras in a stereoscopic configuration to provide height-profile measurement without the added expense and safety concerns of using a laser. Additionally, we have developed a novel technique for calibration of the system, using artificial intelligence techniques to optimize the model fit by adjusting the image analysis tuning parameters to values resulting in the best classification.

Feb 27, 2013

By E. C. Westman

Three-dimensional velocity tomograms were generated on a daily basis to image mining-induced changes to the overburden above a longwall mine. The hypothesis was that a coherent redistribution of seismic velocity, due to the development of high-stress zones, could be imaged at the mine scale. Seam depth was 360 m and source location depth varied from 100 to 1000 m. Sixteen geophones were distributed over a 600 by 600 m square area on the surface above the mine. More than 12,500 events were recorded over an 18 day period. The recorded seismicity provided input for the local-earthquake tomography code, SIMULPS. Eighteen tomograms were generated and high-velocity regions correlated well with high abutment stresses. Additionally, the high-velocity regions were observed to redistribute as the longwall face retreated. These results indicate that velocity tomography can be used to provide a better understanding of temporal changes within a rock mass, and can potentially be used to produce a better understanding of the mechanisms that lead to unanticipated ground failures.

Jan 1, 2008

By J. Frostiak

"This paper describes some energy reduction measures Implemented at the Griffith Mine. Before proceeding, I will give you a brief overview of the operation.The Griffith Mine is an iron ore mining, concentrating and Pelletizing complex located in the red lake area of northwestern Ontario. The operation is owned by Stelco Inc. And is managed By Pickands Mather & Co. of Cleveland, Ohio. Operation of the concentrator commenced in 1968 and it has been producing at a nominal capacity of 1,500 ,000 tons annually.The plant flow sheet is illustrated in this slide. Run of the mine ore is crushed in a single stage 54"" gyratory crusher. Reclaim ore feeders draw from an open stockpile to feed two 32' diameter by 12' long autogenous mills, each driven by 6800 hp. Two s·rages of wet magnetic separation, roughers and cleaners, and primary cyclones complete the primary circuit. Cleaner concentrate is then ground in four 14' diameter by 28' long pebble mills rated at 2000 hp. The secondary grinding circuit is closed by cyclones and fine screens. Secondary cyclone overflow is further upgraded through hydro-separators, finisher magnetic separators and flotation.The magnetic concentrate produced is then thickened, filtered, balled and fired in three vertical shaft furnaces to produce a high quality hematite pellet."

Jan 1, 1983

By Geysen. Daneel

Better slag valorization is part of improving the sustainability of steel, stainless steel and non- ferrous metal production processes. Besides, it can improve the sustainability of other products and production processes as well. A sound and well established slag valorization is beneficial for the overall economics, marketing and appreciation of the metallurgical process and its products. On 6-7 April 2009, the First International Slag Valorisation Symposium was held in Leuven, Belgium. This paper gives a brief summary of the symposium, providing an overview of slag valorization opportunities. The authors believe that high temperature process slags can have interesting applications and that within the next 10 to 20 years slags will need such valorization options in order to compete with other materials and get general support for further production. On the other hand, the authors also expect a higher demand for slags for the production of various materials. High temperature processes should anticipate on the growing opportunities for valorization of slags and increase the resilience of their process by better understanding slag processing, slag quality and material requirements. More interdisciplinary research efforts are required to reach this level of knowledge for the different high temperature processes. Such an interdisciplinary research platform was recently established at KULeuven, Belgium, named SMART-PRO2 (Sustainable Materialization of Residues from Thermal Processes into Products).

Jan 1, 2010

By R. Raghavaraju

Estimation of the dynamic stress field in terms of its amplitude and decay around a blast hole is a key input parameter in all numerical modeling and blast prediction exercises. However, there is very limited information available in literature on these critical parameters, which would be considered essential in any blast modeling exercise. A laboratory-scale experimental study has been carried out in two different rock types to study at very close range the stress wave decay from a blast hole at distances ranging from 3 to 10 borehole radii. The single–hole blasting experiments employed a centrally located detonating cord (5.3 g/m) in 6 mm(1/4 inch) and 10 mm (3/8 inch) boreholes. The coupling medium employed was air and water, in addition to using a thin-walled copper tube in intimate contact with borehole wall to prevent of penetration of explosion gases into the emerging cracks. The paper describes the nature (amplitude and decay) of the transmitted shock pressure and their evolution in the two rock types for these various experimental conditions, which are present to varying degrees in all blasting operations.

Jan 1, 2014

By Ed Cope

The newly discovered South Arturo deposit is a Carlin-type, breccia-hosted, oxide gold deposit located on the Dee Mine property at the north end of the Carlin Trend in Nevada. The Dee Gold Mine was discovered in 1981 by Dee Delamar, a Cordex geologist. The property was put into production by Rayrock Mines in 1984. During its 16-year mine life, the Dee Mine produced about 18.6 t (600,000 oz) of gold from oxide ore at an average production rate of about 1.24 to 1.55 t/a (40,000 to 50,000 oz/year). In October 1997, Bar-rick Gold Exploration acquired the right to earn a 60-percent interest in the Dee property from Dee Gold Mines through an exploration farm-out agreement. Barrick Gold Exploration began exploration activities on the property in 1998 and vested in its 60 percent operating interest in 2004. However, the discovery hole at South Arturo was not drilled until July 2005 from atop the historic mine dumps located 300 m (985 ft) south of the Dee openpit. The discovery hole (BD-72) encountered a cumulative 75.6 m (248 ft) of oxide mineralization grading 1.9 g/t (0.055 oz/st) gold beneath 260 m (855 ft) of dump material and post mineral Tertiary Carlin Formation volcanic and sedimentary rocks. Oxidation within the deposit extends to depths greater than 610 m (2,000 ft). The deposit has passed the prefeasibility test and is presently in the feasibility stage. Exploration is on-going to enhance or enlarge the known deposit. The current resource for the deposit stands at 40.4 t (1.3 million oz) of gold. The South Arturo discovery is an example of an historic mining property yielding a new discovery through the diligent application of area selection criteria of the model type and persevering when early results were generally negative. Barrick?s original exploration pro-grams on the property were focused on the discovery of deep, high-grade sulfide deposits that would likely be mined by underground methods. As it turns out, South Arturo is mostly oxidized and will be amenable to mining by openpit methods

Jan 1, 2008