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By A. Holder

A major mud push occurred on the 870 m production level, scraper drift block cave at Dutoitspan diamond mine in November 2011, during which it is estimated that more than 4 400 m3 of mud engulfed the west cave. The production level was successfully evacuated during the mud push with no loss of life or injury to personnel, thanks largely to mine employees being well trained in and adhering to on-mine mud rush evacuation procedures. All access to the west cave was lost as a result of the mud push. Clean-up operations are currently under way to regain access to the production level, to establish the extent of damage to scraper drifts and equipment, and to evaluate what remedial works may be required to resume production. The magnitude of the Dutoitspan mud push necessitated a detailed investigation into the key contributing factors leading up to the incident, which are discussed in this paper. Mud rush mitigation measures in place on scraper drift block caving operations at Dutoitspan, Bultfontein, and Wesselton diamond mines in the Kimberley area are critically reviewed. Recommendations are furthermore made for enhanced mitigation based on mud rush risk profiles derived for different production areas in these old scraper drift block caves. Keywords mud push, mud rush, scraper drift, block cave, mitigation factors, risk profiles, risk management structure.

Jul 1, 2013

By O. Dahl, B. Musuku, N. Schreithofer

Recovery of fine pentlandite is proving to be a challenging task in the Kevitsa sequential flotation operations, with over 60% of the nickel losses reporting into the -25μm size fraction. Since commissioning, the Kevitsa process has undergone major changes to address throughput and flotation performance. Major changes were implemented in the configuration of the milling and flotation circuits as well as in the operating conditions and reagent regime. Some of these changes improved nickel flotation while others deteriorated flotation performance. Most of the changes have had a direct impact on nickel flotation. This paper reviews the systematic analysis, laboratory testing and salient changes done to the process with special focus on the impact on the fine pentlandite flotation. Keywords: Blending, Flotation, Chalcopyrite, Pentlandite, Fines

Jan 1, 2020

By T. Chikande

"Falls of ground pose costly hazards to personnel and equipment and thus measures should be taken to prevent them. This study endeavours to improve the support systems used in geotechnically poor ground at a Zimbabwean platinum mine by analysing the status quo and recommending an effective support system. Various techniques were used to determine the quality of ground conditions, predict the rock mass behaviour, and to identify the appropriate rockbolt type. An analysis of the current ground control methods and their limitations was also undertaken.The results showed that the current support system and mining practices in poor ground need to be modified to improve safety and productivity. Stoping overbreak is influenced by poor ground conditions and the explosives currently used. The use of emulsion is recommended to replace ANFO. Redesigning of pillars is also recommended in poor ground conditions. An evaluation of the current roofbolt system indicated an opportunity for improvement. With new insight on the performance of the shorter length roofbolts currently in use, a new support system was recommended taking into consideration cost-benefit analysis. Barring down using pinch bars in poor ground was seen as a risky and time-consuming exercise, hence the use of mechanical scalers is recommended to achieve zero harm and to meet production targets. Smoothwall blasting is recommended in poor ground to minimize excavation damage. Other recommendations include the use of hydrological surveys to determine groundwater levels and implement corrective measures. Both empirical and numerical modelling approaches need to be utilized in determining the optimum support. IntroductionThe presence of geological discontinuities such as faults and joints weakens the rock mass. Adequate support is critical in achieving zero harm in underground mines. This paper reviews the current support systems used in poor ground conditions at a Zimbabwean platinum mine. The area of research is located on the Great Dyke of Zimbabwe. The mine exploits platinum group elements (PGEs) and base metals. It is shallow, having a maximum depth of less than 300 m. The Great Dyke is the second largest reserve of PGEs, following the South African Bushveld Complex (Oberthur et al., 2012). It is a linear layered intrusion that extends for about 550 km with a maximum width of 11 km (Prendergast, 1989). The generalized section of the Great Dyke is almost like a trumpet, comprising layers that dip towards the centre. The reef exploited at the mine, the Mineralised Sulphide Zone (MSZ), is located in the pyroxenite layer, which is hosted in the ultramafic sequence. The MSZ is a uniform layer about 2– 3.5 m thick, dipping at around 10–14° from surface outcrop towards the axis of the basin, and located between bronzite and websterite horizons. The visible disseminated sulphide mineralization shows a typical and consistent vertical distribution of platinum group metal (PGM) and base metal values. The research was undertaken to review the current support systems used in geotechnically poor ground conditions in a bid to improve both safety and productivity."

Jan 1, 2016

By M. Abdellatif

The Mintek Thermal Magnesium Process (MTMP) process is based on DC open arc metallothermic smelting of calcined dolomite at normal pressure and temperatures of 1650?1750°C. The process was demonstrated at the pilot scale in the period 2000?2004. Major changes to the MTMP pilot plant were made throughout the development period, which lasted for about five years. The changes included design and installation of new equipment, modification of existing equipment, changes in the metallurgical approach in terms of feed rates, feed recipes, furnace operating temperatures, cold and hot dolime feeding, and steady and systematic changes in the operating procedures and maintenance of the plant. As a result, the performance of the pilot plant gradually improved from one campaign to the next, in terms of availability and in particular the condensation efficiency. In Run 10, the process was successfully demonstrated over an 8-day campaign. Keywords Magnesium, condensation efficiency, DC arc furnace, silicothermic reduction.

Jan 1, 2011

By M. Gericke

Over the past few decades the commercial application of heap bioleaching technology for the extraction of base metals has become increasingly important, due mainly to the depletion of high-grade ore reserves. Heap bioleaching is widely used for the extraction of copper from secondary copper sulphide ores. The design and engineering aspects of the process have received considerable attention, but issues related to the microbiology of the process have been subjected to less rigorous scrutiny. The major role of micro-organisms in bioleaching processes is to catalyse the regeneration of ferric iron and protons, from ferrous iron and by sulphur oxidation respectively. It is accepted that even the most carefully engineered heaps are heterogeneous in terms of temperature, pH, the presence of anaerobic pockets, irrigation efficiency, and dissolved solutes. Since interactions between solution chemistry, mineralogy, and microbial populations exist in heaps, a better understanding of the correlation between microbial numbers and types with changes in these chemical and physical profiles with time would be beneficial during process design and operation of heaps, and could result in faster start-up times and higher metal recoveries. This paper reviews the role of microbiology in heap bioleaching processes. Aspects such as microbial diversity, identification and monitoring of cultures, inoculation strategies, colonization behaviour, and tolerance to metals and salts are discussed, and the potential contribution of the knowledge to the improvement of the operation and design of heap bioleach processes assessed. Conclusions are drawn with respect to the role of genetic engineering, heap inoculation practises, and remaining areas for future heap bioleaching research and development.

Jan 1, 2012

By J. D. de V. Louw

Introduction Zircon is a natural occurring mineral and may exhibit natural low level radioactivity. It contains trace levels (90 to120 pCi/g and 110 to 115 pCi/g respectively or 3.3 to 4.4Bq/g and 4.1 to 4.3 Bq/g) of naturally occurring radioactive uranium and thorium. This mineral is often found in a suiteof minerals (rutile, ilmenite and monazite) Due to the overlap in physical properties of monazite (containing 4–7% thorium) with some of the zircon (slight magnetic susceptibility) it often contaminates the zircon, adding to the levels of thorium in the product. Hazards associated with the products from zircon and its processing is inhalation of respirable dust (generated by milling) containing radioactive uranium and thorium which may cause cancer of the lungs. Legislature regulates the transport, use, workplace environment exposure and storage of radioactive material. In America the general regulation for the unlicensed use of low levels of radioactive materials limits the concentration to 500 ppm (U plus Th). Europe (IAEA) specifies a limit of10 Bg/g (Bequerels per gram) on the parents for transport only which is a higher level of U+Th. Companies selling into these markets need to comply with these regulations and certification is therefore required, not only of the major constituents determining the price, but of the U and Th levels as well. Exceeding the limits for U and Th may result in material being returned to the country of origin. However, for the analyst the requirement is to analyse for these elements throughout the production process as well as the analysis of the ‘tails’ that is returned to the mine area. This requires a wide range of concentration to be analysed. Methods of analysis A wide variety of methods exist for the analysis of U and Th in a range of matrices. (Table I) All these methods have been used with varying degrees of success in terms of accuracy. Overall precision for the different techniques varies from 5 to 25% relative. Time to produce results from these methods vary from a few minutes to several days. The Production Chemist is expected to produce between5 and 10 analyses per hour for process control purposes. A suitable technique that fits this requirement is X-Ray Fluorescence. Both Wavelength Dispersive (WDXRF) and Energy Dispersive X-Ray (EDX) instruments are suitable. X-Ray analysis in general has a few major advantages over competitive techniques. •It is fairly simple to set up and interferences are known and easy to correct •It has multi-element analysis capabilities •Clean spectral lines for U and Th (in zircon specifically) •Uncomplicated and easy to measure background •Low detection limits (3 to 5 ppm) •A very high degree of precision •Sample preparation is uncomplicated and fast (pressed powders and fused beads). In Zircon (ZrSiO4) processed sands the matrix is constant(>99% ZrSiO4) and the background is thus essentially constant. A typical set up for the analysis of U and Th by WDXRFis given below: X-Ray Tube Tungsten (W) Target, 2.5 to 3kW operated at 50mA/50kV Crystal LiF200 (or LIF220 for higher resolution) Analytical Lines (2?)U La1,226.14Th La1,227.47 Detector Scintillation Counter Analysis time, depending on the concentration can vary from as little as 20 seconds up to 5 minutes. Standards As with any other comparative technique XRF analysis relies heavily on the quality of the standards used. Assuming proper set-up and operation of the instrumentation as well as consistent sample preparation, accuracy is determined by the quality of the initial calibration standards. A search for the available zircon certified reference materials (CRMs) shows that there are only a few CRMs

Jan 1, 2003

By C. Chongo, F. X. Paquot, C. Ngulube

"Over the last six years, the Kansanshi copper/gold mine has continued to process significant quantities of complex transitional mixed ores. The effect of the complex mineralogy on the flotation performance is depicted. Initially, ore treated came predominantly from accumulated stockpiles. In the ensuing years, ore treated shifted to primarily freshly mined ore that generally showed less tarnish with better float kinetics but with the downside of producing lower concentrate grades. A number of changes were made to improve the efficiency of the roughing circuit and quality of concentrate produced. These changes were as a result of initial mineralogical studies and laboratory float test work done and discussed at length in a previous paper. Salient among the adopted recommendations from previous work were increasing circuit capacity and modifying configuration to increase the residence time and the number of sulphidisation stages. These modifications were completed and commissioned in 2011. This, however, resulted in significantly low rougher concentrate grades and subsequently below-specification final concentrate product. This was primarily due to higher mass pulls resulting from the extended rougher bank with multiple concentrate discharge streams. This necessitated the need for an enlarged cleaning capability to offset this. The extra cleaning capacity came on-stream in 2014. Of note was the development of a recovery model, based on the strong correlation between the total copper and acid-soluble copper ratio, as a tool for monitoring plant performance. INTRODUCTION The Kansanshi mine, the largest copper mine in Africa, is 80% owned by Kansanshi Mining PLC, a First Quantum subsidiary. The remaining 20% is owned by the state through the parastatal ZCCM. The mine is located approximately 10 km north of the town of Solwezi and 180 km to the northwest of the Copperbelt town of Chingola. The mine has been in commercial operation since 2005. Prior to June 2009, Kansanshi mine treated only two ore types: oxide and sulphide. All transitional ores mined during the period leading up to 2009 were stockpiled. The treatment of the minerologically complex, transitional ores through a third train commenced in June 2009 but with numerous metallurgical challenges. This transitional ore (called mixed ores) could not be previously treated economically due to high gangue acid consumption (GAC) minerals association (making it unsuitable for the oxide float–leach circuit) and poor flotation response ruling out the conventional sulphide float circuit. The new novel circuit involved a conventional sulphide pre-float followed by flotation involving staged controlled potential sulphidisation (CPS)."

Jan 1, 2015

By C. Chongo, F. X. Paquot, C. Ngulube

"Over the last six years, the Kansanshi copper-gold mine has continued to process significant quantities of complex transitional mixed ores. Initially, the ore treated came predominantly from accumulated stockpiles. Subsequently, the feed source shifted primarily to freshly mined ore that generally showed less tarnish with better flotation kinetics, but with the downside of lower concentrate grades. A number of changes were made to improve the efficiency of the rougher circuit and quality of concentrate produced. These changes were as a result of initial mineralogical studies and laboratory flotation test work that were discussed at length in a previous paper1. Salient among the recommendations adopted as a result of previous work were increased circuit capacity and a modified configuration to increase the residence time and the number of sulphidization stages. These modifications were completed and commissioned in 2011. This, however, resulted in significantly low rougher concentrate grades and a below-specification final concentrate product. This was due primarily to higher mass pulls from the extended rougher bank with multiple concentrate discharge streams, and which necessitated an enlarged cleaning capability. The extra cleaning capacity came on stream in 2014. Of note was the development of a recovery model, based on the strong correlation between the total copper and acid-soluble copper ratio, as a tool for monitoring plant performance. IntroductionThe Kansanshi mine, the largest copper mine in Africa, is 80% owned by Kansanshi Mining plc, a subsidiary of First Quantum Minerals. The remaining 20% is owned by the state through the parastatal Zambia Consolidated Copper Mines Ltd (ZCCM). The mine is located approximately 10 km north of the town of Solwezi and 180 km to the northwest of the Copperbelt town of Chingola. The mine has been in commercial operation since 2005."

Jan 1, 2016

By J. N. Van der Merwe

The South African coal-mining industry uses a uniform safety-factor formula for non-squat pillars, incorporating a coal-strength constant that was derived empirically by Salamon and Munro in the 1960s. The constant is 7,2 MPa. Since that time, collapses of pillars at relatively high safety factors have occurred in the Vaal Basin. Analysis of the post-1960s' collapses indicated that the strength constant for the Vaal Basin is 4,5 MPa. A crude method for the prediction of the minimum life span of pillars in the Vaal Basin is presented.

Jan 1, 1993

By P. van der Steen

This paper examines the historical developments in diamond beneficiation technology and the impacts on the industry. The art of diamond beneficiation has given way to the application of scientific process, but at considerable capital expenditure. The shift in beneficiation methodologies has been disruptive to the traditional skills set of the industry, but evolutionary change continues and has been beneficial to the quality of the final product.

Jan 1, 2010

By J. M. Benson

Titanium is an exciting structural material that can offer significant strength-to-weight advantages over currently used alloys. However, its Achilles? heel is its costly, energy-intensive production process that effectively eliminates it from competing with aluminium and high-strength steels, apart from critical applications where titanium forms only a small component of the total cost. Current attempts are being made to reduce the cost of titanium products and these recognize the importance of minimizing the costs over the total production chain. Powder metallurgy (PM) technologies play a crucial role within this, as the output of the existing and potential primary metal production methods is in the form of sponge or powder. By using PM, costly remelting and forming operations can then be avoided, except in the manufacture of large components. Metal injection moulding (MIM) is an effective process for producing complex net-shape components in large volumes from metal powders. Nevertheless, the commercial use of titanium powders in this process is still in its infancy. The only major supplier of feedstock utilizes a polyacetal-based binder. This gives good green strength but requires a catalytic nitric acid process to remove most of the binder prior to thermal treatment. As this involves additional and expensive equipment and is a potentially hazardous process, there is interest in finding an alternative binder system that can be debound either purely thermally or that involves a less hazardous, more environmentally friendly solvent. This paper describes the use of capillary rheometry to characterize the influence of temperature and shear rates on the flow behaviour of potential binder systems for titanium MIM feedstock. Keywords Titanium, metal injection moulding, capillary rheology, feedstocks, powder loading.

Jan 1, 2011

By P. T. Slatter

The efficient and accurate design of pipe and pumping plant for non-Newtonian mineral slurries remains a problem. The objective of this paper is to present the development of the Balanced Beam Tube Viscometer (BBTV), an instrument which could facilitate more accurate design for these slurries. The background of rotational and tube viscometry is reviewed and the fundamental principles and inherent advantages of the BBTV are given. The design, data acquisition and processing techniques are introduced and results showing the reliability of the new instrument are presented and discussed. It is concluded that the BBTV is a reliable and versatile instrument for both routine analyses and research work, and has the potential to provide data for the refinement of the design procedure for mineral slurry pipe and plant design.

Jan 1, 1998

By G. S. Hansford, J. W. de Kock, C. D. Levy

Rheological measurements on pulps from South African gold mines by G. s. HANSFORD, Ph.D. (Pennsylvania), M.Sc. (Cape Town), C. D. LEVY, B.Sc. (Eng.), and J. W. DE KOCK, Ph.D. (Cantab.), B.Sc. (A.I.C.) (Visitors) A method is described for the determination of the rheological parameters of a fast-settling slurry with conventional viscometric measuring equipment. The effect of concentration, temperature, and pH on these parameters is investigated. The results agree with those obtained by previous workers using different viscometers, but this method allows a more detailed characterization of all the properties. From a literature survey, two semi-empirical equations were found that allow the effect of concentration, temperature, or pH on the rheological parameters to be correlated.

Jan 3, 1976

By N. Mangadoddy, M. Padhi

The simulation of multi-component classification with modified viscosity model is the key focus in the current study. The classification of the ores using hydrocyclone is a renowned process and has a convoluted flow separation phenomenon. The highly turbulent flow inside hydrocyclone depends on the operating and design parameters apart from the feed mixture. Slurry viscosity also plays a dominant role in the classification of solid particles under the centrifugal settling action. A heterogeneous mixture with different components would result in different settling and rheological behaviour of particles’ suspension in the water medium. The newly proposed multi-component viscosity model (Mandakini et al. 2020) is implemented as a user-defined function to define the material property during the CFD study of the mixture rheology inside hydrocyclone classifier. The multiphase and turbulence model is solved using the modified Algebraic Slip Model and Large Eddy Simulation model. A comparison of the predicted component performance curves is evaluated with and without the corrected viscosity model. The density and size effect on the particle phase distribution inside the classifier are compared, where the misplacements of the finer particles are carefully assessed. Validation of the component classification in hydrocyclone with the laboratory experiments found a close agreement with the rheology based CFD data. Keywords: Dual-component, multi-component viscosity model, double-gap rheometer, computational fluid dynamics, high solids concentration

Jan 1, 2020

By J. C. Taylor

The Rhodax inertial cone grinder, designed by France?s FCB Group Fives, is the result of three years, theoretical and mechanical research in the field of compression grinding by the research staff of FCB?s CRM minerals research centre. A number of potential uses have been assessed and will be discussed in the paper. The crusher is an inertial grinder that works on the pressurized bed fragmentation principle. The fragmentation force is caused by the rotation of unbalanced masses rather than by an eccentric mass, as is the case in a conventional crusher. This makes it possible to achieve very high reduction ratios. By controlling the speed of rotation of the unbalanced masses, the grinding force can be modified, thus changing the product size distribution. The paper describes the machine layout, operating principles, control parameters and will briefly describe the results obtained on reef, waste and ROM reject pebbles. Some comparisons are made with conventional crushing.

Jan 1, 1998

By J. Portal

One of the key products produced by the mineral sands industry is the titanium dioxide slag, a process that requires grinding of a coarse product down to a valuable saleable product. Traditional methods have included the vertical roller mill in tandem with dynamic air classifiers and, alternatively, two-stage grinding and crushing through an AG mill in closed circuit with a dynamic classifier and secondary gyradisc crushers. The products produced, commonly known as chloride and sulphate slag, are differentiated by the particle size distribution of the final product. The more valuable chloride slag must, by specification, be a product sized in the range between 850 and 100 microns?the more fines generated in the grinding process, the less higher valuable final chloride slag is produced. This paper will explore a technology that is new to both the mineral sands and to other mineral processing industries. Inter particle communition, or IPC as it is known, has been applied in the cement industry to improve the performance of clinker grinding mills. The principle is to create a process of material on material comminution under high pressure that fractures the material along the grain boundaries rather than breaking it smaller than a gap setting in the crusher. The process is now looked at for the TiO2slag producers because of the potential benefits of energy savings and with a minimal generation of minus 100-micron fines. Discussions will revolve around the design and functionality of the Rhodax® both from a process and maintenance perspective, a typical test regime and results on slag grinding. The development of the flowsheet necessary for the process will be examined, the ancillary equipment required and finally the scale-up from the test to an industrial plant will be investigated. Full-scale results of an operating plant will also be given showing the benefits that can be realized. A promising new flowsheet with fines reintroduction to the Rhodax® crusher will be presented.

Jan 1, 2007

By J. J. S. de Beer, F. Hunter, A. F. Neethling

SYNOPSIS The paper describes the rib-pillar extraction method now used at Sigma Colliery in the Orange Free State. In this method, access roadways (with a high safety factor) are developed into a block of coal suitable for total extraction; pillars that have a low safety factor are then formed and extracted immediately. The method, together with the current practices of labour management, has resulted in better utilization of the coal resources and capital, increased production and labour productivity, and improved safety.

Jan 1, 1991

By M. B. Dunn

Terminals form part of the transportation chain from producer to consumer in the world-wide conveyance of bulk commodities. As such, they are a vital link in providing a buffer between widely differing transporation modes. It is essential in the conceptual design of such terminals that an overall view of the entire system of which they form a part is taken. Only in this way can it be ensured that the system will operate smoothly and without disruption, for in the end such disruptions can have dramatic repercussions, both on the cost of the commodity in the market place and on production. In this respect, computer simulation is a useful tool in arriving at the optimum design for the system. The Richards Bay Coal Terminal provides a good example of such an approach. Commissioned in 1976 to handle 12 Mt per annum, it is now handling 24 Mt per annum, with plans for further expansion to 44 Mt per annum in the future.

Jan 1, 1980

By P. J. Bartlett, H. A. D. Kirsten

A two-dimensional numerical scheme for the simulation of the plastic stress-strain properties of rock, and the various components of rock reinforcement and shotcrete, was used to rigorously determine the characteristics of tunnel support under squeezing conditions. D-shaped tunnels varying in size from 2,8 to 6,5 m in height and width were considered. The four main mining stages in the BAS block cave on Premier Mine were simulated as alternative sets of field stresses. The rock reinforcement comprised 1,8 m long fully grouted rockbolts and 6,0 m long fully grouted cable anchors at various spacings, and of various tensile and bond strengths. Various thicknesses of shotcrete and footwall support configurations were also considered. It was found that shotcrete and rock reinforcement, owing to inherent differences in stiffness, do not function in unison. As monolithic application, shotcrete has an overriding avidity for the imposed loading and destructs itself unless of extraordinary thickness. Under squeezing conditions, it accordingly supports the excavation surface while the rock reinforcement contains on-going convergence. The loads in the various support components can be determined only by simulation of the shotcrete as a stress-relieved medium to represent its broken condition in the field. The loads in the rock reinforcement vary around a tunnel and are the largest in the sidewalls. The loads increase with an increase in tunnel dimensions, the increase in load in the sidewall due to an increase in height being larger than that in the hanging- and footwalls due to an increase in width. Depending on the strength of the rock, the loads in the rock reinforcement become prohibitively large beyond a certain size of tunnel. The reinforcement of footwall rock can be omitted without adversely affecting that in other walls, provided the tensile and bond strengths of the reinforcement are not limited. The resulting footwall heave may, however, result in undermining of the reinforcement in the adjoining walls. A relative depth of anchor of 1,37 provides adequate bond strength in the larger sizes of tunnel, whereas, in smaller tunnels, anchor length is determined by the allowable convergence. The lack of fun column grouting adversely affects the efficiency of rock reinforcement to a major extent. The loads in rock reinforcement are very sensitive to the strength of the rock. Owing to a lack in refinement and calculational rigour, empirical classification systems are an inappropriate means for the design of tunnel support in squeezing conditions and, as a result, grossly unclear-estimate the support requirements.

Jan 1, 1992

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