Search Documents

The optimal design of production phases and ultimate pit limit for an open pit mining operation may be generated using conventional or stochastic approaches. Unlike the conventional approach, the stochastic framework accounts for expected variability and uncertainty in metal content by considering a set of equally probable realizations (models) of the orebody. This paper evaluates the performance of a new stochastic network flow approach for the development of optimal phase design and ultimate pit limit using a gold deposit as the case study. The stochastic and conventional frameworks as considered here utilize the maximum flow and Lerchs-Grossman (LG) algorithms, respectively. The LG algorithm is restricted to considering an estimated (average-type) orebody model, while the stochastic maximum flow algorithm is developed to simultaneously use a set of simulated orebody realizations as an input. The case study demonstrates that, when compared to the conventional LG algorithm as used in the industry, the stochastic approach generates a 30 per cent increase in discounted cash flow, a 21 per cent larger ultimate pit limit, and about 7 per cent more metal, while it maintains a consistency in phase size.

Jan 1, 2012

By J. P. Beukes

South Africa holds approximately three-quarters of the world?s viable chromite ore resources and dominates the global production of ferrochrome. Albeit completely unintended, small amounts of Cr(VI) are formed during ferrochrome production. Certain Cr(VI)species are regarded as carcinogenic, hence making the treatment of some ferrochrome waste materials necessary. In this paper, the Cr(VI) treatment strategies currently employed by the South African ferrochrome producers are investigated by means of a literature review and a questionnaire survey. From the discussion, it is evident that various treatment strategies are available to deal with Cr(VI)-containing waste in the ferrochrome industry. However, by far the most commonly applied treatment strategy remains the aqueous reduction of Cr(VI) with ferrous iron. The advantages and the correct application of this strategy, together with the disadvantages and pitfalls, are argued. Innovative improvements on historic practices are also discussed

Jan 1, 2012

By Timo Niitti, Antti Rinne, Janne Turunen, Klaus Schommarz, Sami Grönstrand

This paper captures the essential steps employed in developing Outotec?s new FloatForceTM mechanism. The development of a flotation mechanism essentially revolves around the efficient transfer of installed power, or capital cost, to optimum flotation performance. Optimum flotation performance will be achieved if a balance between metallurgical results, operating and capital costs is maintained. The development of the FloatForceTM mechanism was done by careful evaluation of each of these three areas. This paper focuses on how experience, CFD and laboratory equipment, pilot and plant tests are used to test and evaluate a new flotation mechanism. Validated variables include mixing profile, power draw and local air hold-up. Metallurgical and mechanical design considerations are not covered in this paper. Besides using the FloatForceTM mechanism in new flotation equipment, the FloatForceTM mechanism can be used in existing flotation cell installations, thus enabling improvements in the mixing profiles, solids suspension and metallurgical performance of operating flotation circuits. Results of several tests carried out in existing plant operations are presented.

Jan 1, 2007

Outotec?s direct leaching process is an atmospheric leaching process for sulphidic zinc concentrates. The direct leaching process, based on special leaching reactors developed by Outokumpu, is the most economical way to produce electrolytic zinc. The production scale applications of the process realized so far are in use at Boliden?s Kokkola and Odda zinc plants. A new full-scale application of Outotec?s direct leaching process will be started in 2008 in China. The process is integrated into the existing production plant, replacing part of the old production facilities by modern technology. Besides high zinc extraction the plant expansion and modernization offers also indium recovery, iron precipitation and solution purification processes. The process equipment includes tailor-made reactors designed on the basis of the work and experience of Outotec research centre. Keywords: zinc, concentrate, atmospheric leaching, technology, indium, iron precipitation, solution purification, Outotec.

Jan 1, 2008

By D. P. Power

The development of an accounting code for the metallurgical industry has been debated for many years. Following the series of tumultuous economic events in the nineties and earlier this century that have affected business, there was much need for legislation to be passed to minimize potential risk. One of the consequences to affect the mining industry was the enhancement of existing geological codes for reporting. In parallel the sponsors of AMIRA have taken the brave step to develop a generic code for metal accounting that embraces the full gamut of industry. In this paper the code will be reviewed in the context of metallurgical accounting as it applies to coal preparation. This paper provides the background for this development and an insight into the mechanism for the debate for the generation of this code. The key elements of the code as it applies to the coal industry are explained but most importantly the key opportunities are highlighted.

Jan 1, 2010

By N. J. Roodt

Mine dumps created in terms of the pre-MPRDA regime (old order mine dumps) are currently not regulated by the MPRDA, and the common law owners of such dumps are free to process them without the need to obtain the relevant rights. The MPRDA Amendment Act purports to change this position. However, the wording of the Amendment Act raises a number of problems which render the post-amendment position at best unclear and at worst absurd and unworkable. The primary concern with the Amendment Act is that, on one interpretation, material placed on the same dump at different times may be treated differently at law. Thus, parts of a dump may be subject to one person?s right while others may be subject to another?s right. Moreover, case law has generally regarded mine dumps as movable property and, by extending the MPRDA to apply to all mine dumps, the Legislature is extending the ambit of the Act to cover movable property, a scenario not contemplated by the wording of the Act (even after its amendment) in relation to applications for rights. The better interpretation of the amendments, which are not yet in force, is that they will not apply retrospectively to old order mine dumps.

Jan 1, 2010

By B. Kruger

After the milling and flotation of the platinum bearing ore, the flotation concentrate is electrically smelted in 6-in-line electric arc furnaces and the resulting furnace matte treated in Peirce Smith converters to remove the iron. The iron-free (less than 1% Fe) converter matte is granulated and sent to the base metals and precious metals refineries for further processing. During the smelting and converting processes two distinct gas-strength gas streams are produced: ?The Peirce Smith converter off-gas contains 4%?9% SO2which is treated in a conventional sulphuric acid plant to produce 94% H2SO4. ?The electric furnace off-gas contains 0.9% SO2which was (until September 2002) vented through a 91- metre high stack to atmosphere. In October 2002 Impala Platinum commissioned a SULFACID® plant at its smelter in Rustenburg, which recovers the SO2from the electric furnace off-gasses into a weak sulphuric acid solution. The SULFACID® technology utilizes wet activated carbon to oxidize the SO2toSO3. The SO3reacts with the water on the catalyst and is washed off the catalyst bed as a sulphuric acid solution with up to 13 wt. H2SO4. The plant operates at 60ºC and at atmospheric pressure. The SULFACID® technology is widely used in the pigment industry. This is, however, the first application of the technology on electric furnace off-gas. Keywords: SO2, sulphuric acid, electric furnace, off-gas, SULFACID®

Jan 1, 2004

By R. Ciccu

This paper examine the optimization of a beneficiation plant for recovering marketable barites from crude ores of different characteristics. The plant, part of a mining complex in Sardinia, consists of a jig section integrated with a flotation line. The problem has been studied using a suitable model of the process, based upon experimental and field data pertaining to both the characteristics of the feed material and the performance of machinery. Data have been automatically processed with the aid of a computer to find the optimum setting of each section, in order to maximize profit for each kind of ore separately fed to the plant. Moreover, the advantages of blending the various concentrates - not all of them individually marketable - are also demonstrated. The overall economic result can be improved provided suitable proportions of each kind of ore are fed to the plant. Such information is fundamental for the long-term planning of exploitation of available reserves, and provides guidelines for further prospecting. The paper illustrates the washability characteristics of the ore's and describes in detail the model adopted. The results of data processing are then presented in the form of computer graphs and discussed. Finally, conclusions are drawn regarding the advantages of resorting to Operations Research as an aid to management.

Jan 1, 1987

By M. Rudman, L. Pullum, L. J. W. Graham

Centrifugal pumps are the workhorse of hydraulic conveying systems but their performance is derated when viscous non-Newtonian fluids, such as pastes and/or coarse solids are present. The reduced performance for purely viscous Newtonian fluids may be calculated using techniques such as the Hydraulic Institute method, but similar deration for non-Newtonian fluids is not so easy to apply. As part of the AMIRA P599 project investigating high concentration suspension pumping, centrifugal pump tests were systematically conducted on a wide range of non-Newtonian coarse particle suspensions. Suspension sup to 38% v/v of coarse particles with mean diameters in the range of 1.1 < d50< 3.4 mm suspended in carrier fluids with dynamic yield stresses of 0 < t?< 17.2 Pa and shear thinning indices in the range 0.35 < n< 0.79 were examined. Techniques such as the Hydraulic Institute de-ration method require a characteristic shear rate to be assigned before application with a non-Newtonian fluid, and a method based on pump geometry, fluid rheology and flow rate is proposed. This method predicts the dramatic characteristic reduction in head at low flow rates that is often observed and explains why larger pumps are relatively insensitive to this form of head deration. Head deration due to the presence of coarse particles in non-Newtonian carrier fluids is seen to follow similar trends to that of Newtonian suspensions and often dominates the total deration procedure.

Jan 1, 2007

By Phil Morriss

During the last 12 months, Sandvik?s Technical Service Group has carried out nine Scoping and Pre-feasibility studies for the application of In-pit crushing and conveying (IPCC) for large mining companies; the majority in conjunction with the Snowden Consulting Group. During these studies several key and recurring drivers have been identified: 1. Mining schedule issues ? there are several issues which crop up repeatedly, including: ?the unnecessary curvature of pit walls, ?very high rates of vertical advance which are (created by schedule optimisers to minimise stripping at all times) which are at the limit of what can be realistically achieved (and which of course make it harder for IPCC to achieve any impact), and ?The allocation of material to semi-mobile systems to maximise the ability for IPCC to be an effective alternative. 2. IPCC productivity issues ? the key issues are the IPCC system operating hours achievable, and the system throughput (both instantaneous and the average). 3. IPCC Risk issues ? there are perceptions about the risks associated with the use of IPCC which are a mix of reality and fiction, but which nonetheless create negativity towards the use of IPCC. In this paper, the authors wish to address specifically the factors affecting the IPCC productivity.

Jan 1, 2008

By A. P. I. Popoola

Aluminium AA1200 was laser alloyed with a combination of nickel and titanium diboride using different weight ratios. Chemical reactions took place with the formation of different phases. The characterization of the alloyed surfaces was carried out by x-ray diffraction (XRD), optical and scanning electron microscopes. The alloyed surfaces are composed of the initial phase of Al-Ni dendrites and eutectics of TiB2/Al and TiB2/Ni distributed on the initial phase. Experimental results obtained showed that Al-Ni intermetallics brought about a significant increase in the hardness property of Al; however, these intermetallics are highly brittle and prone to fail by brittle fracture or stress corrosion cracking when put in service. The addition of TiB2 brought about a reduction in the formation of the seintermetallic phases. A microhardness increase of over 10 times the hardness of the substrate was achieved. Keywords Dendrites, intermetallics, metal composite, Nd: YAG laser.

Jan 1, 2011

By R. Hummel

In the quest to reduce overall costs and improve operating efficiency, the application of GPS based technology in open pit mining has evolved significantly in recent times. Venetia Mine has been leading the way in the De Beers group in the implementation of these systems and the realization of significant benefits from them. Following on from the successful results and the notable benefits obtained from the Wenco Truck Dispatching system and the Caterpillar CAES system on the loading and dozing equipment, Venetia has implemented the first fully functional and integrated GPS based drill monitoring system in southern Africa to its drilling operations. This paper elaborates on the concept of drill monitoring and how the vision for the application of the system at Venetia has developed and been implemented. The paper further describes the workflow involved, beginning with the initial test work done with SSI Kaltex and the Australian Drill Advisor system through to the final details of the integration of the Aquila system with the CATERPILLAR Computer Aided Earthmoving System (CAES) and the alliance with SandvikRock Tools. Most importantly, the paper details the benefits that are derived from drill monitoring and the use of the information generated by such a system. Venetia has pioneered the move towards smart partnerships and alliances with strategic suppliers within the De Beers group. The area of drilling, as the important start of the entire mining process, has been no exception and the final part of the paper covers how drill monitoring provides vitally important information that enables a supply partnership, to function cost-effectively and profitably for both parties involved. By having the type of accuracy, detail, validity and timeousness in the information being received as a result of the implementation of such a system, better management decisions can betaken, creating a more focused and efficient mining environment. In these times of increasing costs and reduced commodity prices, the mining industry will be required to continue pushing the boundaries on these technology applications in order to remain competitive.

Sep 1, 2001

By J. Abdollahisharif

Optimal cut-off grade is one of the most critical parameters in open-pit mine design because it defines the ore and waste and thus determines the maximum net present value possible from the mining operation. Although the algorithm presented by Lane (Choosing the optimum cut-off grade. Colorado school of Mines Quarterly, vol. 59, no. 4, 1964. pp. 811-829) is the most common one in the literature, it does assume constant capacities of the mine, processing, and refinery. In this paper, Lane&apos;s original algorithm has been modified to consider variable processing capacities in order to determine the optimal cut-off grade in open-pit mines. The new algorithm proposed here is compared to both Lane&apos;s original algorithm and to a previous modification that incorporated rehabilitation costs into the cut-off grade estimation. The algorithm proposed here that permits variable processing capacities is shown to be superior for the determination of optimal cut-off grade to both these previous versions. In addition, a computer-based program was developed in Microsoft Office Excel© to calculate the optimal cut-off grade as proposed here.

Jan 1, 2012

By E. -U. Reuther

To improve the climatic environment underground the German coal mining industry has installed refrigerators with a capacity of 300 MW cooling power. One third of this total is accounted for by central refrigeration plants with more than 5 MW capacity. The central refrigeration comprises three stages: mechanical cooling, transport and distribution of chilled water via pipelines and exchange of heat in the air coolers. Of these three stages only the mechanical generation of chilled water has been resolved satisfactorily. Transport (including distribution) and exchange require further technical research. The Mining Institute of the Aachen University of Technology has done extensive studies on this subject, concentrating on controlling the flow of chilled water according to demand in the mine. Additionally, the favourable exchange in the air coolers is taken into account. The studies are based on a model mine which simulates the conditions in deep coal mines in Germany. The simulation program represents firstly the condition of the mine air at the location of the air being cooled, then the heat exchange in the air cooler itself, and finally the transport of the chilled water from the central refrigerator to the consumer. The program also reproduces the seasonal and operational changes in conditions of mine air as well as different air cooler designs. A regulated distribution of chilled water is also suggested. Finally, estimations of costs can be made as an aid for further planning.

Jan 1, 1987

By R. L. Robinson

An analytical framework is formulated to assist mining companies in assessing the relative merits of mineral exploration and acquisition strategies. The anticipated costs, risks, and returns of each strategy are conceptualised using decision trees. Economic criteria - expected net present value, expected return per unit of investment, and the probability of success - for each strategy are derived(from the appropriate decision tree network. Application of the analytical framework is illustrated using the example of a medium-size company in the Canadian base metal sector.

Jan 1, 1987

To the members of The South African Institute of Mining and Metallurgy I have audited the annual financial statements of The South African Institute of Mining and Metallurgy set out on pages 641 to 644 for the year ended 30 June 2006. These annual financial statements are the responsibility of the Institute?s Council members. My responsibility is to express an opinion on these annual financial statements based on my audit. Scope I conducted my audit in accordance with International Standards on Auditing. Those standards require that I plan and perform the audit to obtain reasonable assurance about whether the annual financial statements are free of material misstatement. An audit includes: ?examining, on a test basis, evidence supporting the amounts and disclosures in the annual financial statements, ?assessing the accounting policies used and significant estimates made by management, and ?evaluating the overall financial statement presentation. I believe that my audit provides a reasonable basis for my opinion. Audit opinion In my opinion, the annual financial statements present fairly, in all material respects, the financial position of the Institute at 30 June 2006 and the results of its operations and cash flows for the year then ended in accordance with generally accepted accounting practice appropriate to the Institute. Supplementary information The supplementary schedule does not form part of the annual financial statements and is presented as additional information. I have not audited this schedule and accordingly do not express an opinion on it.

Jan 1, 2006

By G. R. Sawyer

Although backfilling has been in operation for many years, the methods for selecting appropriate slurry dewatering aids have, in some cases, been rather unsophisticated. This has led to many misconceptions regarding the role of the dewatering aid and its various means of application. Testing procedures employed in the correct selection of any practically applied dewatering aid must mirror the actual working processes in which they are to be used. This constraint necessitates the development of complex testing methods when applied to backfilling. The current testing procedures were scrutinized and their various merits noted. From this study a series of testing methods was evolved which incorporate the best aspects of these testing procedures with novel ideas which would eventually result in the correct selection of the dewatering aid. A major consideration in the application of any of these methods is the modus operandi of the backfilling process, and the relevance of the tests to the process. This work attempts to consolidate the testwork performed in the past and suggest new approaches in the correct selection of acceptable dewatering aids for backfilling.

Jan 1, 1988

By A. M. Engelbrecht

Paper written on project work carried out in partial fulfilment of B Eng. (Chemical) Membrane processes are vital to a diverse range of technical and biological systems, which also feature in mineral processing applications such as the treatment of mine effluent and extraction of metals. In this study, the use of cellular automata to model a semi-permeable membrane that separates two compartments is considered. Cellular automata are simple models that enable the analyst to represent well-understood local effects, such as the chemical or steric interaction between molecules themselves and between molecules or particles and their environment, which can lead to very complex behaviour on a macroscopic scale. Various physical phenomena, including reverse osmosis, were simulated. Initial results for the effect of temperature, membrane structure and chemical properties of the solutes on the performance of the membrane appear promising. Keywords: cellular automata, dynamic modelling, filtration, membrane fouling, osmosis.

Jan 1, 2007

By P. J. Kinver

This paper deals with the development of backfilling methods and systems at the Broken Hill orebody of Black Mountain Mineral Development Company (Pty) Limited, at Aggeneys in the north-western Cape Province. Production started in 1979, being confined to large diameter blasthole stoping methods in the upper, steeply dipping areas of the orebody. This blasthole reserve is now depleted and the production tonnage, 100000 tons per month, is produced from eight cut and fill stopes in the flatter dipping areas of the orebody. The fill methods of the blasthole stoping area evolved prior to the pillar extraction are briefly discussed together with the resulting experiences gained that enabled virtually 100% extraction to be achieved. The original cut and fill mining used costly hydraulic cemented fill; this was replaced partly by unconsolidated river sand and later by dune sand which occurs in abundance. The paper describes the planning, research work and commissioning of a cycloning plant that now enables dune sand to be used successfully as an unconsolidated hydraulic fill. The development of drainage, placement and control methods are also reviewed.

Jan 1, 1988

By W. K. Osae

A value assessment model which uses deal objectives, financial and non-financial indicators as a guide to assess value creation in mergers and acquisitions. The extent to which post- merger deal objectives are achieved and the potential benefits derived from mining deals that may not necessarily be financial of nature, but which are necessary to sustain and enhance future performance, were considered. The pre-merger and post-merger performances based on some financial indicators that reflect profitability for shareholders were also used. This value assessment model was used to assess four major deals that have occurred in the South African mining industry since 2003 as part of a postgraduate dissertation. In this paper, the Harmony and ARMgold merger is used as an example of how the model can be applied. The model?s relevance and applicability can also serve as a guideline in developing a framework or holistic guideline in assessing whether mining BEE deals in South Africa create value.

Jan 1, 2011