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For resources projects with healthy net present value (NPV) and low cash flow volatility, conventional discounted cash flow (DCF) analysis will continue to provide the dominant investment decision-making criteria. However, DCF analysis can be biased because it often applies a single risk-adjusted discount rate (RADR) to compare the value of projects with different risk characteristics. Many of the difficulties with DCF modelling arise from analysts' inability to determine appropriate risk discounts and to estimate expected spot prices inputs for the commodities produced over the life of the project. Modern asset pricing (MAP) is a very valuable complement to DCF analysis in addressing some of these issues. Most papers dealing with MAP, however, while academically rigorous, tend not to be explicit in terms of practical application of this methodology in routine project evaluation. This paper has the objective of reviewing the MAP methodology and of demystifying its complexity, by providing a simple but realistic step-by-step evaluation of a mining project, comparing its DCF and MAP NPV values. The paper concludes that MAP provides a minimum, risk-adjusted `floor' value, thus representing a valuable complement to any DCF valuation.

Jan 1, 2007

By A. Refahi

For predicting the energy consumption during the size-reduction process, the Bond approach is often used. In this work, the PFC3D discrete element method (DEM) software was employed to model the crushing behaviour of some rocks with different mechanical properties in a laboratory jaw crusher. FLAC3D software was adopted to analyze the stress distribution in the rocks. The rocks studied were modelled as granular assemblies in the shape of a sphere and/or a cube located between two jaws, and the work done by the jaws in the crusher was determined. Nine different types of rocks were studied and the energies consumed by the crusher were compared to those of the Bond comminution energy estimated from the Bond index. There is considerable difference between Bond crushing energy and work done by the jaw crusher for rocks. It appears that the Bond approach is not a suitable method for predicting single particle fracture energy done by the crusher. To verify the results obtained from DEM models, the fracture behaviour of the crushed rocks was examined and was compared to the PFC3D results. The tensile mode of fracturing is favourably modelled by the PFC3D software while the delamination mode cannot be well modelled by PFC3D software. Keywords: jaw crusher; discrete element method; crushing energy; Bond index

Jan 1, 2009

By B. Gamble

Solid Energy's project evaluation process utilises a standard staged gate approach, with five levels leading ultimately to project execution (level 6). For a project to progress through each level, specific financial criteria need to be satisfied. Solid Energy primarily use value based (discounted cash flow) metrics to support investment decisions. Within this approach Solid Energy utilise a number risk-based techniques to quantify project uncertainty. This includes the use of risk-based probabilistic analysis using Monte Carlo simulation and probability-based scenario analysis. Figure 1 shows the net present value (NPV) cumulative probability. Project risks are identified through comprehensive risk workshops. The output of these workshops (list of key risks, ranges of uncertainty and probability of occurrence), is quantified within the financial models. Incorporating this risk information on a probabilistic basis allows an investment decision to be made with a robust knowledge of the range of possible project outcomes along with the likelihood (probability) of those outcomes occurring, for example 80 per cent confidence that the project value will be greater than NZ$10 M, 50 per cent confident it will be greater than NZ$50 M and ten per cent confident it will be greater than NZ$70 M. Incorporating risk implicitly into the financial analysis allows the business to easily evaluate/measure projects with different risk profiles. The detailed risk analysis does away with the complexity of arbitrary risk-based hurdle (discount) rates, as projects can be evaluated based on their specific risk characteristics. Whether a project will progress to the next level of investment and ultimately into implementation depends firstly on the value assessment in comparison with the associated risk/uncertainty, and secondly matching this with the businesses appetite for risk. At Solid Energy standard criteria are used for specific project evaluations, but in addition projects are considered on a portfolio or strategic basis also. Solid Energy attempts to maintain a mix of low risk (low value) projects with some high risk (high value) opportunities. The mix of projects must remain in line with the shareholders' risk appetite. One of the keys to a successful investment decision is ensuring that the appropriate information is available to decision-makers so that they may proceed with a comprehensive understanding of the risks and impacts associated with the decision.

Jan 1, 2007

By K. Premlall, R. M. Dire, H. Bissett, D. Delport

Tungsten carbide is a fine grey powder. It can be formed into shapes by compacting with the addition of a binder. Spherical particles are generally preferred in additive manufacturing as they pack together more efficiently than non-spherical particles, promoting a uniform powder bed density, better flowability, and elimination of internal cavities and fractures, resulting in a better quality of final product. The particle shape of powders can be transformed into spherical through the process of spheroidization. However, due to its high melting point, tungsten carbide could be difficult to spheroidize. Tungsten carbide was spheroidized using an inductively coupled radio frequency plasma at various plate powers between 9 and 15 kW. The influence of additional H2 in the sheath gas on the chemical composition of the tungsten carbide product was also investigated by means of XRD, which indicated that WC is converted to W2C at higher H2 concentrations. Optical analysis of SEM micrographs indicated that the spheroidization ratio increased with increased plasma energy.

Apr 1, 2021

By C. M. Suhr

n order to validate the borehole analysis valuation procedure commonly used in the South African gold mining industry, a simulated orebody was used to create borehole values which would serve as data for the procedure. After confirming the distribution, calculating the variance size of area relationship, estimating the block variance, and calculating a profit measurement for each set, comparisons were made to the known population parameters. Results show only one overall bias (in the estimation of the lognormal third parameter), which is carried throughout the analysis. The remainder of the analysis is unbiased, validating the procedure.

Jan 1, 1987

By D. J. Mourant

Day-to-day operations on the Broken Hill mine of the Black Mountain Mineral Development (BMMD) Company require a detailed knowledge of the distribution of the ore minerals within the orebody. The data are acquired by systematic underground diamond drilling of the orebody and subsequent geological and analytical borehole logging. These data are then captured onto a database, available for further analysis. Before mining commences in a mining block, copper, lead, zinc, silver and bismuth assay values, and the specific gravity of each sample, are extracted from the database. 3-dimensional variogram and kriging calculations are performed for each geological zone; for all the metals of interest. A computer representation of the mining block in the form of an ore model is then built using these kriged data. From these ore models information is extracted as required by the Geology Department on the mine, and used in numerous operations. These include: daily grade control to supply optimum feed grades to the treatment plant; the compilation of short, medium and long term production schedules; orebody outline definitions for the detailed planning of mining operations; ore resource calculations. The system has been modified and updated since its inception and provides timely information in a production environment.

Jan 1, 1987

By J. Trcková

This paper describes the method of modelling rock mechanical problems on experimental models. Based on an actual experiment used as an example, assessment of the surface deformation due to undermining, the extensive possibilities of using a 3-D physical model and application results in practice are demonstrated. A special method of modelling the underground mine progress by using paraffin melting is presented. Keywords: undermining, subsidence of surface, 3-D experimental model

Jan 1, 2009

By R. Morris, W. D. Clough

SYNOPSIS The design of an opencast coal mine over areas previously mined by underground mining methods presents several potential methods of mining the coal. The paper describes some basic methods of mining for the No. 2 seam of the Witbank Coalfield, which had previously been mined by the bord-and-pillar method.

Jan 1, 1985

By M. C. Mulligan

Counter current decantation (CCD) thickener circuits are used to recover soluble metal as pregnant liquor solution from ore leach residue. The basis of CCD operation is to concentrate suspended solids thereby minimizing liquor content in underflow slurry that flow in one direction. Then the underflow slurry liquor is diluted with wash liquor that flows in the opposite direction and the suspended solids are concentrated again and again. The amount of liquor in the thickener underflow contributes to determining the number of CCD stages required to recover the desired amount of soluble metal. Furthermore, similar results could be achieved at a lower wash quantity, reducing the size of downstream equipment. High density thickeners (HDT) are designed to use gravity and compression, and minimize the amount of liquor in the underflow thus minimizing the number of CCD stages. This paper reviews the process used to select HDTs rather than high rate thickeners (HRT) for the Ruashi II copper-cobalt hydrometallurgical process in the Democratic Republic of Congo (DRC), using laboratory HDT simulations, to CCD simulations and thickener design details.

Jan 1, 2009

By Ernst-Ulrich Reuther, Alexander Donmen

Mine ventilation in the German coal mining industry is concerned mainly with problems of thermal environment arising from greater depths and with increasing emission of methane gas. The development of computer techniques over the past ten years for solving these and ancillary problems is reviewed. The emphasis from a planning and control point of view falls mainly on ventilation network calculations, temperature predictions and advance estimates of methane emission.

Jan 1, 2014

By E. Bakhtavar, R. Mikaeil, D. Khademi

"Fuzzy-weighted integer goal programming has been developed and used to select the most suitable site to construct a central processing plant for several adjacent small-scale dimension stone quarries, based on the most effective criteria. In the first step of mathematical modelling, the most important goals and decision variables were defined. Accordingly, an objective function was used in the model for minimizing the sum of undesired fuzzy-weighted deviations. Fuzzy weights were determined by a matrix of pairwise comparisons of various expert judgments in this field and the fuzzy geometric mean. The goal and systemic constraints were also modelled. The most suitable site for the construction of the plant was selected after solving the mathematical model in the ExcelR Solver add-in. The selected site had various advantages over the other sites, such as the shortest average distance to the quarries, the shortest distance to power access and workforce, and the lowest land price. IntroductionSelection of the most suitable site of a plant is one of the most important considerations when constructing an industrial project. A suitable site has a significant effect on a company's competitiveness in the market. Selecting a desirable location for constructing plants such as mineral processing facilities is an essential part of the economic planning that will enable a company to meet the needs of related upstream and downstream operations. These units are considered to be best built near the relevant mining sites because of technical difficulties, the cost of transporting minerals, and the traffic hazard caused by the movement of trucks transporting materials. Two main types of research using multiattribute decision-making models have been reported for selection of a processing plant site (Safari et al. 2010, 2012). In that research, the analytic hierarchy process (AHP) and fuzzy technique for order preference by similarity to ideal solution (TOPSIS) approach were applied to select the suitable locations for the mineral processing plants for phases 1 and 2 of Sangan iron ore mine."

Jan 1, 2017

By F. Hees, A. H. Bracken, L. I. Boshoff

"Biological cementation of the Mandena heavy mineral sand deposit in Madagascar was causing difficulty in dredge mining and hence in planning and control of production rates. An investigation was initiated to better evaluate the geotechnical properties of the orebody by defining the distribution and geotechnical properties of the cemented strata, in order to generate a site-specific geotechnical model for the deposit. The geotechnical characterization was developed by an integrated approach using several ground investigation techniques such as piezocone (CPTu) testing, geotechnical drilling, standard penetration testing (SPT), as well as laboratory testing. The final outcomes of the investigation included a 3D geotechnical model showing the distribution and extent of the cemented areas, as well as the typical geotechnical parameter ranges associated with each of the defined geotechnical units. The interpretations developed were incorporated into the mine and production planning to ultimately optimize operational planning and control.IntroductionQIT Madagascar Minerals (QMM) is a heavy mineral sand mining operation at Mandena, near Fort Dauphin in Madagascar. During the final planning and commissioning stages of the project, the need to fully characterize the unusual geotechnical conditions was identified and a geotechnical investigation became necessary.Nature of the problemDuring the commissioning phase it was found that mining production was being hampered by biologically cemented/indurated layers encountered within the sands. Closer inspection of the indurated horizons in the dredging face revealed that these layers contain a high loading of bacteria and fungi. It appears that the bacteria produce an extracellular (outside the cell) polysaccharide (i.e. sugar and carbon salts), which form a gelling biofilm to trap nutrients. There are a number of different bacteria. The fungi, on the other hand, produce a network of fibrous strands that bind the sand grains together. Thus both bacteria and fungi probably contribute to the ‘apparent cohesive’ strength or binding of the indurated sand (Lynn, 2008)."

Jan 1, 2017

By A. S. Nhleko, P. R. Lobe, H. Mtegha

"Government’s equity role in the minerals sector is one of the nationalist measures implemented in order to ensure greater control and management of a country’s mineral resources. This paper evaluates the Tanzanian government’s equity participation in the minerals sector from 1996 to 2015. The research methodology included determination of the number of mineral rights, minimum allowable exploration expenditures in prospecting licences (PLs), and forms of equity role of the government. Data was collected and analysed for PLs, mining licences (MLs), and special mining licences (SMLs).The study revealed a number of challenges faced by the Tanzanian government as regards its equity strategy in the mineral sector. One of the major challenges was the secrecy surrounding agreements and contracts entered into between the government and private sector investors, which were concluded via various business ownership and mineral development projects. This secrecy resulted in non-transparency and lack ofaccountability in the mining industry.The financial benefits accruing to the government were inadequately realized, evident through inconsistent payments of corporate income tax and mining royalties by the mining companies. Furthermore, the government does not have solid mechanisms and frameworks for assessing non-financial benefits, thus it is difficult to measure the impact of these factors.It is recommended that the Tanzanian government review the Mining Act and Regulations of 2010 to include the provision of solid mechanisms and frameworks for all forms of government equity role.This paper is based on an MSc research study undertaken at the University of the Witwatersrand.IntroductionGovernments can grant private companies mining rights to extract mineral resources, or take a stake in the companies as well as establish state companies to oversee their interests in the minerals sector. The establishment of a state company to oversee government interests in the mining sector implies the direct participation of government by way of equity participation. Equity participation or role is defined as the holding of shares in an enterprise, company, or asset by individuals or a body corporate (Otto, n.d.; Brown, 2013; Natural Resource Governance Institute, 2015)."

Mar 1, 2019

By J. Petersen, H. Naderi, H. Zare, M. H. Nikzad, M. Karimi

In the copper electrorefining process, the dissolution of anodes is significantly reduced or even stopped when the passivation phenomenon occurs. The results of this phenomenon are increasing energy consumption, residual formatting, and voltage levels in the cell. In this study, the electrochemical behaviour of blister copper in the presence of sodium persulfate (PDS) was studied. The electrochemical methods of LPR, Tafel, and Electrochemical Impedance Spectroscopy (EIS) were used. The results showed that the addition of sodium persulfate activates the electrode surface and increases the open circuit potential. In the presence of PDS, the polarisation resistance of the electrode shows an increasing or decreasing tendency, based on the PDS concentration. This tendency is probably due to the formation of surface layers (such as slime layer or copper sulfate) and dissolution of this layer at various concentrations of PDS. The lowest polarisation resistance of 1.8 ohms and the highest corrosion current of 60.6×10-3 and 36.6×10-3 A/cm2 from LPR and Tafel techniques respectively were obtained at the concentration of 40 g/l PDS. Based on the results of potentiodynamic and electrochemical impedance spectroscopy tests, the addition of sodium persulfate to the solution reduces the corrosion resistance, therefore the passivation time of the blister copper anode increases. Keywords: Blister copper, electrorefining, sodium persulfate, anodic passivation

Jan 1, 2020

By Pieter de Waal

The beneficiation equipment under the control of plant metallurgists exploits the differences in the physical properties between valuable and waste mineral components. In many cases, laboratory results are too late for process control and can only serve the purpose of "post" reports, the calculation of a mass balance and the issue of a quality certificate. As a result, experienced operators regularly adjust separation equipment based on the colour and texture of the various product streams in the beneficiation plant. Metallurgists quickly learn to recognise the different minerals in their ore body. The stereo microscope has been a valuable tool used by operators to quantify known mineral species. For many years it was the only practical method available for the purpose of process control and even for quality contro1. The modem spectroscope is far superior to the human eye and can rapidly detect a change in mineral composition. New generation optical scanners and digital signal processors can provide useful signals, related to mineral composition that can readily be applied for the purpose of process control. Successful case studies, covering dry in-line and slurry applications as well as in-plant fast spot analysers are presented.

Jan 1, 2014

By E. E. Almási, G. Mucsi, G. Rákhely, Á. Rácz, B. Csőke, Zs. Pap, K. Bohács, N. Halyag

Wet stirred media milling is a widely applied grinding process in the field of mineral processing to produce <10 μm ground materials. In this paper, the results of wet stirred media milling of different Ti, Fe and Cu-oxide and phosphate minerals are presented. During the experimental work, grinding of ilmenite, vivianite, hematite and cuprite was carried out in a continuous operation wet stirred media mill. During the experiments, the particle size distribution and specific surface area of the ground materials were determined after a certain grinding time, as well as measuring the specific grinding energy, thereby determining the grinding kinetics of the different minerals. The measurement results showed the differences and similarities in the grindability of the individual minerals. Nano particulate vivianite, hematite and ilmenite was successfully manufactured in a stirred media mill; however cuprite was characterised as the coarsest final product for the same grinding circumstances. Keywords: Wet stirred media mill, cuprite, vivianite, ilmenite, hematite

Jan 1, 2020

By S. Northey, N. Haque, S. Stoddart, W. Bruckard

Development of new technologies and procedures for managing mineral residues and wastes may benefit from a clear understanding of existing tailing management practices. There is a considerable variability in tailing management techniques used in the Australian copper and gold operations, with associated differences and flow-on effects for the mine site water balance. A database was created, capturing a total of 41 copper and gold processing operations in Australia. The database provides information on tailing generation rates, tailing properties (solids contents and particle size distributions) and tailing storage facility (TSF) types and configurations (e.g. total TSF surface area and wetted surface area). Significant variability was found for the above-mentioned parameters. The solid tailing generation rates ranged from 0.5-37 Mt per annum in 2015. Furthermore, both the solids contents and particle size ranges of the tailing were highly site-specific, and largely dependent on the processing flowsheets. Solids contents of tailings ranged from 45-74% by weight whilst P80 sizes of the concentrator (flotation) feed varied from 75-185 μm. The estimated pumping distance was up to 15 km. The presented data can potentially be used to better tailing management strategies by estimating the potential recoverable water and recycling it, thereby thus reducing tailing footprints. Keywords: Tailing management, tailing storage facility, water balance, mine site, flowsheeting

Jan 1, 2020

[COUNCIL FOR 1992/93 President J.P. Hoffman President Elect Dr H. Scott-Russell Vice Presidents Senior J.A. Cruise Immediate Past President R.D. Beck Junior D.A.J. Ross-Watt Honorary Treasurer J.A. Cruise Members of Council Dr N.A. Barcza B.R. Broekman G.A. Brown P.M. Craven Prof. R.J. Dippenaar J.R. Dixon* A.A.B. Douglas B.R. Fleetwood Dr R.V.R. Handfield-Jones P.R. Janisch * co-opted P.J. Knottenbelt R.P. Mohring J.L. Nel* K.C. Owen P.D.K. Robinson K.A. van Gessel D.J. van Niekerk C.J.C.J. van Vuuren* P.M.T. White]

Jan 1, 1993

By T. Tholana, P. N. Neingo

"A mineral resource constitutes the principal underlying asset of a mining company, and must be exploited and managed in such a way that maximum value is derived from it. Various asset management frameworks applicable to physical assets are available. This paper focuses on the extension of an asset management approach, particularly the Publicly Available Specifications (PAS) 55 asset management framework and the International Organization for Standardization (ISO) 55000 series of standards, to mineral assets. It is concluded that PAS 55 and the ISO 55000 series of standards can be extended to manage mineral assets, resulting in an integrated approach to sustainably optimize value from the company’s mineral assets. The benefits include improved returns on mineral assets, maximum mineral asset utilization, creation of an organizational culture focused on quality and continuous improvement, and assurance to stakeholders that the mineral assets are being efficiently managed over their entire life-cycle. In the context of this paper, a ‘mineral resource’ refers to both Resources and/or Reserves as classified by the SAMREC Code. IntroductionMining involves the extraction of valuable mineral resources from the Earth’s crust. A mineral resource is unique among natural resources in the sense that it is a wasting asset, which means that its value depreciates continuously with extraction. In addition, it is often impaired from time to time as commodity price changes (Macfarlane, 2011a). Since a mineral resource is a wasting asset there is a single opportunity available to optimize value from its extraction. Mine planning involves identifying a strategy to exploit the mineral resource in a way that maximizes value at an acceptable risk level throughout the life of mine (LOM). This optimum extraction strategy changes as economic conditions change, particularly commodity prices, as well as with improvements in orebody knowledge as mining progresses. It is the mineral deposit that competitively distinguishes two different mines and dictates the location of a mine; hence the adage ‘the orebody dictates’. Therefore, a mineral resource is the primary tangible asset possessed by mining companies and must be managed in such a manner that maximizes its value at an acceptable risk level (Macfarlane, 2011a)."

Jan 1, 2016

Mining is a business involving extraction of commodities of value to society from non-renewable resources. Consequently there is only one opportunity to extract ore from the ore body in order to unlock the value potential encompassed in the asset. It is therefore imperative that the maximum value is unlocked during the extraction programme, considering the relative wealth generated for shareholders and society, the sustainability of society, the environment and the operation. The bulk of the value that is unlocked is usually embedded in the initial design process. How do you measure sucess The most common measure of success is the return on investment, which is unlocked during the extraction process. This is usually only determined and locked-in during the study process. Another measure of success is the profitability that is achieved on a monthly basis. A further measure would be the enhancement the asset affords to the share price of the operation. Increasing focus on sustainable development requires that the impact on the society and environment received high priority as well. All these measures are largely encompassed in the cash flow and the discounted cash flows. This paper focuses on the dynamics of the cash flow and the most significant elements influencing return in investment. These include the mine design, production volume, sustainability, risk and valuation techniques. When do you add the most value? There are many different phases and definitions noted by different authors to demonstrate and standardise the study process for new projects. This paper is based on a process with 3 major components namely a conceptual study, a prefeasibility study and a feasibility study.

Jan 1, 2007