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By T. C. Alex, K. M. Godiwalla, R. K. Jana

Manganese nodule, available in ocean beds, is a potential resource of the future for copper, nickel and cobalt. Recovering only these metals, containing less than 3% by weight, will result in the generation of large amount of residue. In addition to the material losses, several environmental and ecological problems arise out of this. The present study has been aimed at reducing the environmental and ecological problems associated with massive generation of this residue together with utilization of the resources. Presence of ~ 20% manganese and ~16% silicon in the residue has prompted us to check its suitability as a raw material for silicomanganese production. Lower manganese content and lower Mn/Fe ratio of the residue than that required for silicomanganese production has been corrected in this study by suitable blending. The efficacy of blending and its thermodynamic aspects using FACTSAGE software are discussed. The studies conducted indicate viability of bulk utilisation of the residue through silicomanganese production and thereby reducing the burden on environment to a great extent.

Jan 1, 2007

The heap leaching of base metal ores can be applied within a number of different scenarios, each requiring its own set of parameters to be determined during the metallurgical testwork programme. The occurrence of acid-gangue reactions and its concomitant precipitation reactions is a factor common to all cases, and requires that the optimal irrigation acid strength be found that optimises the combination of extraction kinetics, acid consumption and possible premature blinding of the heap due to precipitation reactions. For the heap bioleaching of base metal sulphide ores the oxygen requirement needs to be determined for the design of the aeration system, and the operating conditions employed need to also facilitate bacterial growth over and above the acid strength optimisation mentioned above. For the heap bioleaching of chalcopyrite, the need to preserve heat in the heap becomes yet a further parameter of critical importance. For the heap leaching of uranium ore a choice is required between either chemical or bacterial oxidation, based on economic and processing factors. Frequently the operating parameters need to be determined for a circuit in which heap leaching is combined with tank leaching and/or pressure leaching. The processing implications and metallurgical testwork approach for each case is discussed.

Jan 1, 2007

By A. Bascetin

One very important aspect of mining is deciding what material in a deposit is worth mining and processing, versus what material should be considered waste. This decision is summarized by the cut-off grade policy. The cut-off grade strategy for an open pit mine influences the annual cash flows and affects the net present value of a project. The optimization of cut-off grade strategy requires the knowledge of detailed operational costs, mining sequence, mining operation, processing, and product constraints, as well as the grade distribution of a given deposit defined by pit, phase, and different material types. Cut-off grade optimization algorithms have been developed in the past. The most common criteria used in cut-off grade optimization is to maximize the net present value (NPV). This paper describes the determination of a cut-off grade strategy based on Lane?s algorithm adding an optimization factor based on the generalized reduced gradient (GRG) algorithm to maximize the project?s NPV. The introduced algorithm is a windows based program developed at Virginia Tech that is based on a series of Visual Basic routines within a spreadsheet environment (Excel).The benefits of the methodology are demonstrated using a hypothetical case study. Keywords: Cut-off grade optimization, net present value maximization, generalized reduced gradient algorithm method.

Jan 1, 2007

By M. Yavuz

Two different methods of fuzzy multiple criteria decision making have been proposed to solve the problem of mining method selection in the paper titled ?Mining method selection by multiple criteria decision making tool, by Bitarafan and Ataei. This problem is really important and also difficult to solve because of the need of handling many criteria simultaneously in the process of decision making. Bitarafan and Ataei have selected 15 criteria for the case study in their paper and those criteria have not been clustered/grouped yet. The number of selected criteria is only 15, although there are more criteria that should be handled in a real case, because they have used Saaty?s method in the section ?Fuzzy multiple attribute decision making? in their paper. Saaty?s method considers the pair wise comparison of criteria and uses random indexed which have already been derived and published. Available random indexes, however, have been derived for maximum 15 criteria so far.

Jan 1, 2007

By C. Kelley

For years urethane screen surfaces have been used in a wide range of wet screening applications where openings as fine as 75 microns and coarser have been used. In dry screening operations these same urethane screen surfaces have been relegated to only the coarser separation ranging from 1.0 mm and larger. The purpose of this paper is to expose the reader to new developments in both screen surface and screening equipment technologies, which allow an end user to consider urethane screen surfaces for dry screening operations where separations as fine as 75 microns are required. These technologies allow an end user to realize the inherent advantages of urethane in wear resistance while also realizing the benefits that a high open area urethane screen surface can bring. These benefits include non-blinding characteristics and feed capacities, which rival that of traditional stainless-steel woven wire mesh screen surfaces. The paper will highlight the features of this patented urethane screen surface technology and the screening machines in conjunction with which they are used. There will also be a presentation of several case studies of commercial installations where these technologies are utilized. These case studies are from the mineral sands industry; therefore relevance to the conference is direct and not inferred. Included in the paper will also be constraints, which must be taken into account when considering urethane screen surfaces such as temperature and chemical attack. This paper will expose potential end users to a possibility of using screens to achieve extremely accurate size separations in applications where screens were previously not considered. The paper will explain and demonstrate that prior concerns of screen surface blinding, high screen surface consumption rates and large screen surface area requirements can be eliminated by proper utilization of high open area urethane screen surfaces.

Jan 1, 2007

By M. Tangstad, B. Monsen, H. Midtgaard, R. Ishak, M. Syvertsen, I. Solheim

Charcoal is an interesting reducing agent because it is produced from growing wood which is renewable and does not contribute to global warming, provided that there is a balance between the felling of timber and growth of trees. In the biocarbon project the possibilities for using charcoal is investigated as well as other biological based and renewable reductants for ferroalloy production. The background for the project is that the Norwegian ferroalloy producers wish to contribute to reduction of CO2- emissions. This paper focuses on the use of charcoal instead of coke for the production of manganese alloys, and the consequences of doing so. Results from practical SiMn smelting experiments on a pilot scale have previously been reported, where only 12-14 % Si in the metal was obtained when charcoal was used. Recently we have attained satisfactory 18 %Si also for charcoal, but good results are indeed dependant on good furnace performance. There is no tradition for using charcoal for manganese production in Norway. A change from using mainly coke to the use of some charcoal will demand new routines for furnace operation, raw material and off-gas handling. Hence, characteristic properties of charcoal, which may cause change of furnace operation, have been measured and are compared to coke. The following results are presented: ?Thermal abrasion strength together with CO2- reactivity; important parameters for the performance of the upper part of the furnace. ?Coke-bed resistance; it will increase with the use of charcoal (a review of new results). ?Slag reactivity; a relevant method for testing slag reactivity of industrial reductants is of interest. The suggested method can serve for comparing slag reactivities towards graphite.

Jan 1, 2007

By H Zimba, S Sondashi, M Chitambo

By the time a reagent is finally accepted by a mine for use on its plant it could have gone through several screening and evaluation stages. These stages may include laboratory and plant evaluation testwork. This paper outlines the steps that were followed to select, design and implement a frother for KONKOLA COPPER MINES PLC Nchanga Copper Concentrator in Zambia. It discusses initial frother screening work conducted at the Betachem metallurgical laboratory and the subsequent laboratory screening testwork conducted at Nchanga Concentrator. A modified Bikerman test method is discussed which was used to design a frother for the Nchanga flotation plant. The paper also gives an account of several plant scale trials conducted on Nchanga flotation plant and discusses the plant results, frother consumption patterns and some commercial concerns, before the product was finally accepted by the mine.

Jan 1, 2007

By A. Morley

It is difficult to evaluate exploration properties in a manner that is transparent, repeatable and easily re-calculated to cater for different geological interpretations, but the risk-based assessment methodology, the Geological Risk Method, developed and described by Lord et al (2001) attempts to satisfy all these criteria. This paper examines a case study example based on valuations of exploration projects conducted by SRK Consulting using this methodology, and describes some of the advantages and limitations of the method.

Jan 1, 2007

Two column flotation cells have been installed as single-stage rougher cleaners at Batu Hijau. The objective was to provide additional residence time in the cleaner circuit to maintain maximum recovery during high mill throughput and high feed grade periods. Installation of the columns has allowed the relatively coarse, well-liberated rougher concentrate and the relatively fine, low-grade scavenger concentrate to be treated separately, improving metallurgical performance in the cleaner circuit. Plant results show that the columns produce a high-grade concentrate at an average stage copper recovery of approximately 80 per cent. There is also indication of increases in both overall plant copper recovery and final concentrate copper grade. In addition, the operability and stability of the cleaner circuit has greatly improved.

Jan 1, 2007

By J. de Villiers

Through the application of the Rietveld method, X-ray diffraction analysis has developed into a fully quantitative method for phase analysis. The Rietveld method itself has progressed from an unstable method that required constant operator intervention to a stable and robust method suited even for routine analysis. The method, however, requires a good initial calibration and periodic checks on its precision and accuracy. Several examples from minerals processing, pyrometallurgy, and materials science show the strengths and applicability of the method. The limitations and sources of error are also discussed.

Jan 1, 2007

By A Weber, L MacNamara, H Schreiber

Design and development of the world?s largest flotation cell was completed in 2002. This was the first 257 m3 flotation cell installed in the mineral industry and represents a major development in the design of larger flotation cells. This cell has a 50% increase in volume over the widely installed 160 m3 WEMCO® Smartcell? flotation machine. In the next few years it is anticipated that 257 m3 flotation cells will be incorporated into rougher-scavenger flotation circuits in many more world class copper sulphide concentrators. The prototype 257 m3 cell, No.250 Smartcell? flotation machine was installed at Minera Los Pelambres in the front of Row 1 in the existing rougher flotation circuit. This cell is followed by nine No. 130 Smartcell? flotation cells. After the successful development phase, this unit has been incorporated as part of a row of No. 250 Smartcell? flotation machines at Minera Los Pelambres. A key to the successful development of the equipment has been the emphasis placed on fundamental hydrodynamic scale-up criteria. Hydrodynamic factors include superficial gas velocity, water (pulp) circulation through the draft tube, and pulp mixing (distribution) characteristics. This paper will review the scale-up criteria of the No. 250 flotation cell, and present a case study of the in-plant equipment testing. The case study will document the metallurgical and hydrodynamic performance of the machine. It will also illustrate the economic benefits derived by incorporating larger flotation cells in a modern copper sulphide concentrator.

Jan 1, 2007

By B. M. Munyungano

Rössing Uranium Mine operates a recovery circuit with continuous ion exchange followed by solvent extraction. Serious organic degradation problems were encountered during 1985/6, 2000 and 2005 in the solvent extraction plant. The preferential loss of the tertiary amine extractant was observed during the above-mentioned period. Previous investigations revealed that the tertiary amine was breaking down to nitrosamine, which cannot take part in the exchange reaction with U3O8. A reduction in the redox potential of the solvent extraction plant feed to below 500 mV halted this preferential loss. A lot of effort has been made to try and understand the actual mechanism for nitrosamine formation. Current understanding for the degradation is that formation is due to high nitrates on the strip side of the circuit emanating from nitrates from the precipitation process using ammonia. It is the current belief that pH lower than 3.7 on the strip side results in loading of nitrates onto the solvent. If oxidizing conditions prevail on the extraction side of the solvent extraction circuit, the tertiary alamine will then degrade into nitrosamine. This phenomenon is yet to be established and verified. It has, however, been established that the above process is brought about the following conditions ?High redox potential greater than 550 mV predominately caused by a high Fe3+/Fe2+ratio (4:1) ?Perception that if Fe2+<0.5 g/lit will contribute to high redox ?High concentrations of NO-3 in the conc eluate (feed to SX)/ammonium sulphate (NO-3> 4 g/l based on historic values) ?Presence of Mo as a catalyst ?Tests also have proved that the presence of nitrous acid in a concentration of 1 g/lat 550 mV leads to formation of nitrosamines from alamine.

Jan 1, 2007

By P. Vlasak, Z. Chara

Since the flow behaviour of slurry containing both coarse and very fine particles has not been sufficiently clarified, the paper focuses on the experimental study of the particle size distribution, time and intensity of shearing and the effect of chemical agents on the hydraulic gradient versus the average velocity relationship of fluidic ash slurries in the laminar and turbulent regimes. The recirculation pipe loop with smooth stainless steel pipes of inner diameters 26.8 and 36 mm was used for measuring the ash-water mixtures flow parameters. The dense fluidic ash-water mixtures behave as time dependent non-Newtonian slurries. Shearing, the addition of bottom ash or chemical agents, favourably affects the flow behaviour of dense fluidic ash-water slurries. The hydraulic gradient in the laminar region significantly decreases; also the laminar/turbulent transition region is reached for lower flow velocity.

Jan 1, 2007

By Z. Weisheng

The lift system is the main part in manganese nodule mining on the ocean bed. It connects the nodule collection system (miner) with the surface platform (mining vessel) and transports the nodules from the ocean bed to the surface. China started the research on lift technology in deep ocean mining in 1991, and a slurry pump hydraulic lift method has been developed for the nodule mining system. The detailed slurry pump hydraulic lift experiments have been undertaken with crushed nodules in the vertical pipe. The lift parameters to lift coarse particles in the lift pipeline have been discussed, including the pressure drop, the solid concentration, and the mixture velocity. The author of this paper not only took part in all these studies on the lifting technology, but was also responsible for some of this research. This paper will present the component parts of the lift system and the research results of coarse particle mixture flow in the vertical lift pipeline. Keywords: deep sea mining, slurry pump lift, lifting parameters.

Jan 1, 2007

By K. Ford, R. Urquhart, D. Hobbs

CIS countries are home to some of the world&apos;s largest producers of chrome, manganese and silicon ferro alloys and leading suppliers to world export markets. The region&apos;s ferro alloys production is rising faster than demand from its domestic steel industry - unit alloy consumption in domestic steelmaking is in fact falling as process efficiencies improve - and there is significant spare capacity available to increase production. CIS producers enjoy certain strategic advantages in the production of ferro alloys - for example, captive ore sup-plies, low power and labour costs - but must also meet certain challenges - such as lower labour productivity and greater distance to market than some of their competitors. CIS producers are ambitious but new investment is needed to upgrade some aging plants and overhaul outdated process technologies if they are to be more competitive with the world&apos;s leading producers and address the environmental issues that are now moving up the agenda. This paper describes the structure of the region&apos;s ferro alloys industry and discusses its advantages and disadvantages by alloy and by country. It considers how the ongoing process of restructuring and new investment in the industry might move forwards, based on its strengths and weaknesses, technical and environmental factors and the strategies of the main players. It asks how the industry might maximise its substantial potential - in particular, for the production of chrome and manganese ferro alloys - and examines the implications this holds for all global ferro alloys players.

Jan 1, 2007

By A. K. Anyimadu

Ongoing development work on ultra-fine grinding for various applications at the Group?s concentrators has been conducted by Anglo Platinum over the last few years. Current potential applications for mainstream grinding and concentrate grinding are the subject of a group-wide research and development programme. The first 10 000-litre 2.6 MW IsaMill was jointly developed by Anglo Platinum, Xstrata Technology and Netszch for installation at the Western Limb Tailings Re-treatment project in Rustenburg, South Africa. The unit was commissioned in late 2003/early 2004,and has operated in an intermediate concentrate regrind application successfully since. This paper describes the operational performance to date, as compared with the original duty specifications and objectives. The first mainstream M10 000 IsaMill with a 3 MW drive will be operational in November 2006 at the Potgietersrus Platinum (PPL) ?Platreef? Sandsloot Concentrator in South Africa?s Limpopo Province. Keywords: Western Limb Tailings Re-treatment Plant, IsaMilling, Platreef, platinum, palladium, PGMs, tailings.

Jan 1, 2007

By B. Gamble

Solid Energy&apos;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&apos; 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

Mineral Resource Throughput Management is based on the extraction of the maximum potential value from an ore reserve with the emphasis to generate maximum ROI and ROR (return on reserve). A steel producing company in India implemented MRTM to significantly improve their ROI and ROR. The value chain of this company consists of their own iron ore and coal mines, ore washing plants, sinter plants, steel plants, and sales and marketing division. The target for the mines was to produce at a stable and predictable rate and at specific quality requirements. These requirements were set to improve productivity and ROI of the steel plant. The implementation constituted the alignment of the reserve potential, total production chain, human resources and management culture at the mines with the requirements of the steel plant. Many typical mining practices were challenged and changed. Production targets regarding lump vs. fines ratio, consistent product tons, quality targets such as Fe, Al content and moist, and standard deviation on the quality targets were not achieved. A reverse distribution model with release mechanisms to satisfy the demand were developed and implemented at the mines. A stable and predictable flow of mine product with quality standards well within the required standard deviation targets were achieved. The contribution from the mines to significantly improve the Net Profit, ROI and ROR of the company were reached.

Jan 1, 2007

By Deon van Tonder, Bert Van Hege

Comparison of various technologies for uranium recovery from sulphuric acid leach solutions shows that Resin-in-Pulp (RIP) and/or Solvent extraction (SX) based processing routes are usually cost effective (11). A combined RIP-SX recovery-purification route and a CCD-SX recovery-purification route were investigated and optimised. The design basis used for the investigation was a production rate of 200 kg/h U3O8 over a solution concentration range of 40 to 1500 mg/L U3O8. The OPEX for the RIP-SX processing route was found to be sensitive to the variation in uranium concentration in the leach liquor. One of the main drivers for this trend is the leach acid concentration. Conversely, the CAPEX of the CCD-SX processing route was sensitive to the uranium concentration in the leach liquor. The leach acid concentration only affected the OPEX of the CCD-SX processing route modestly, as the bulk of the acid is recovered in a pre-leach circuit. Contrary to expectation, the effect of extractant loss assumptions on the overall processing route economics was found to be modest to insignificant. It should be noted that the CCD-SX processing route OPEX was more sensitive to extractant loss assumptions than the RIP-SX processing route OPEX. Economic optimum wash ratios were determined for the CCD-SX processing route and increased with leach concentration ? the increase in wash ratio was less than proportional. A 5-stage CCD configuration was found optimal over the concentration range investigated.

Jan 1, 2007

By J. A. Bakken, M. Tangstad, P. A. Eidem

In the submerged arc production of ferromanganese, sillicomanganese and ferrochromium, the coke bed characteristics play an important role. The basic mechanisms of electric current conduction in the coke be dare not yet fully understood, but important parameters are the material resistivity of coke and the contact resistance between the coke particles. Preliminary tests indicate that the contact resistance is of great importance to the bulk resistance of the coke bed. An apparatus measuring the material resistivity and contact resistance of carbon materials has been developed. Both graphite and industrial coke have been tested. The material resistivity tests were performed on single particles to ensure that the effects of pores and cracks were included and the contact resistances were excluded. Two geometries were tested to obtain the contribution of the contact resistance to the total resistance of two connecting particles. The tests were performed in an inert atmosphere at temperatures and current levels found in industrial submerged arc furnaces. The results show that the method has a satisfactory reproducibility. It was found that the contact resistance is about 10 times higher than the resistance of the material when two particles are in perfect contact and that the resistivity of SSAB coke is more than 10 times higher than that of the graphite at room temperature, but with increasing temperature the difference decreases. For SSAB coke the general trend is that both the resistivity and the contact resistance decrease with increasing temperature.

Jan 1, 2007