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By M. Eraydin

Dewatering fine particles (e.g., flotation concentrates) is inefficient, energy intensive and often requires large capital and operating costs. To address these issues, a series of advanced dewatering technologies have been developed at Virginia Tech. These include novel dewatering aids and a hyperbaric centrifuge. Typically, the moistures obtained using these methods are 30% to 50% lower than those obtained using conventional methods, as demonstrated in laboratory and pilot-scale test programs. With another novel dewatering technology that has been tested in bench-scale tests, the moistures can be reduced to levels once believed to be attainable only through the use of thermal dryers. In this communication, test results obtained with these advanced dewatering technologies are presented and compared.

Jan 1, 2014

By Homero Delboni, Mauricio Guimarães Bergerman

"At the regrind or secondary grinding stages of metal ores, usually the concern about the energy efficiency is extremely important. In general, the specific energy consumption at this stage is higher than in the primary stages of grinding. In addition, it has been observed a tendency of finer grinding in the new projects of metallic ores, due to the finer mineral liberation, which leads to an increasing capital and operational costs. In Brazil, during the last 10 years, regrind P80 sizes of approximately 40 to 20 ?m have been necessary in all new iron and copper plants. The use of conventional ball mills, adequate for primary grinding, can result in low energy efficiency with products below a P80 of 50 ?m. This paper presents an overview of the regrind circuits in Brazil that operate with vertical mills and the results of industrial surveys at selected vertical mill circuits. Where possible, comparison is made between the plant results and the design criteria and laboratory regrind tests used for the mill sizing."

Jan 1, 2014

By N. Mphathiwa

When slope angles are designed during open pit optimization, there is a risk factor applied in steepening the slopes. The steepening of slope angles has implications for the safety and economics of the mining operation. The steeper the slope angles, the greater the probability of slope failure. Although a slope failure will result in added costs, the challenge is to compile an accurate cost-benefit exercise optimizing the economic benefits of the project without exposing mine workers and equipment to unacceptable risk of rockfalls. A balance between the safety of the operation and the economics of the investment is therefore required. The ideal situation is to have a slope monitoring system that will predict slope failure by detecting any ground movement before the actual failure occurs. This early warning will allow the risk factor to be applied with a high degree of confidence, knowing that the risk will be adequately mitigated. The objective of this paper is to provide guidelines on how to design an optimal survey slope monitoring system. It is the authors? view that for a survey monitoring system to yield desirable results, it should adhere to survey principles such as working from the whole to part and consistently cross-checking. The case study used is Jwaneng Mine, and the design strategy outlined can be used as a guideline for developing a new slope monitoring system or to optimize an existing one.

Jan 1, 2014

By Bianca Foggiatto, Marko Hilden, Malcolm Powell

"Since the introduction of the concept of flexible circuits (Powell and Bye, 2009), it has been further developed and refined to the definition of ‚FlexiCircuits leverage ore variability to maximise resource utilisation?. The focus of flexible circuits is to investigate processing options that provide extra capacity through sophistication rather than scale. This requires a combination of smart ore characterisation, economic modelling and innovative processing plant design. Flexible circuit design can reduce energy requirements through gangue rejection or progressive ore upgrade; and increased robustness and controllability by leveraging off ore variation. Each rock type, as characterised through Geometallurgical ore modelling, may be processed more efficiently by individually optimising processing paths. The objective of FlexiCircuits is to transform the processing capability of comminution and concentrator plants - targeting step change in performance through integrating a range of interrelated improvement opportunities. Considerable effort has been applied to developing the modelling and simulations tools required to develop and demonstrate the potential of this concept. This paper presents a practical application as a test case. A realistic application of flexible circuits is provided through a conceptual circuit design of an iron ore processing plant. It is simulated as a multi-component feed with a range of new models in the researcher’s Model Developers’ Kit (MDK) to trial the ability of different circuit designs to respond to variable ore and quantifying the potential of these circuits to transform processing capability of variable ore feed. The outcomes of the simulations are presented and discussed, providing a practical demonstration of the level of modelling and simulation required and the potential of flexible circuit design."

Jan 1, 2014

By R. Hejazi, Saghaeian. M., H. Abedini

Continuous vacuum belt filters mainly carry out an important duty in the solid-liquid separation processes such as iron ore concentrate dewatering. However as the particles become finer, the resistance to filtration and dewatering would increase and as the result cake moisture content tends to increase. So in recent decades, using additives in order to improve the filtration performance has been considered by many researchers. In the present study, the effect of several surfactants on the filtration rate and cake moisture content of Chadormalu iron ore concentrate (80% =40 micron) was investigated using a laboratory scale vacuum filter. The results of several tests indicated that a non-ionic surfactant (Lauryl Alcohol Ethoxylated, LAE) has the best performance on reducing the moisture content of the cake and reducing the cake formation time. The optimum dose of LAE was found to be 300 g/ton which reduced the concentrate cake moisture content from 13.76 to 11.28% (wet weight base). Some industrial filtration tests were performed in Chadormalu iron ore concentrate plant to prove the effectiveness of this surfactant. The surfactant is mixed with water and added to the concentrate slurry before distributing on the vacuum belt filter. The industrial and experimental results were almost similar, so that adding about 300 g/ton of LAE would reduce the final cake moisture content from 12.87 to 10.76%.

Jan 1, 2014

By Suping Yao, Chuanyu Jiang

In the last decade, the copper industry in China has witnessed a significant change. The capacity and production of refined copper has grown remarkably from 1.5 million tons in 2002 up to 5.88 million tons in 2012. And now, China has become the biggest copper producer in the world, counting about 30% of the global refined copper production. This paper summarized modern copper smelting and converting technologies employed in China copper industry, such as OT flash technology, TSL (ISA/Ausmelt), SKS bottom blowing, Jinfeng side blowing, etc…This paper also presents some key development and improvement of these technologies up to date from their practical application in China, what will contribute as great value to any new / or renovation copper smelting projects down the road. As an engineering company in China, NERIN has been involved in many of these projects in the past decade, played an important role in the engineering works and accumulated intensive experiences. NERIN is one of the best choices for the world clients in the copper industry, providing quick engineering service, delivering cost effective projects.

Jan 1, 2014

By B. Currie

Maintenance of quality electrowon copper requires an electrolyte which has suitable chemical and physical characteristics. The proper design and operation of the solvent extraction plant is essential to the quality of the electrolyte sent to electrowinning. An aspect that is not well appreciated is that the return electrolyte can have negative effects on the operation of the solvent extraction plant. Poor SX plant operation creates below optimum electrolyte conditions. High Eh in the return spent electrolyte can degrade the SX reagent with large decreases in copper transfer capacity and increases in internal entrainment. The synergistic interaction of the SX and EW plants needs a single-source design approach to address the interactions. The design elements in the SX and EW plants required to manage the electrolyte conditions are discussed.

Jan 1, 2014

By Z X. Zhang

If the iron ore loss is 15% in the process of mining, the total iron ore loss in the world will be about 461 million tons, this is equal to the total production of 230 iron ore mines each of which produces 2 million-tons of iron ore per year. Based on a series of blast tests in the Malmberget mine, this paper shows that ore recovery can be markedly increased by improving blasting technology such as choosing a correct primer position and making use of shock wave collision. The paper further suggests that a high ore recovery can not only reduce natural resource loss and mining cost but also prolong the life of a mine. In addition, the paper shows an example of reducing blast-caused rock damage in the roofs and walls of underground drifts (tunnels) by using new blasting methods in the Malmberget mine. Finally, the paper shows how the Malmberget mine has successfully reduced the ground vibrations, without adversely affecting fragmentation and ore recovery in sublevel caving mining.

Jan 1, 2014

By B. Peszko

There are many measuring methods of grain sizes. Taking into consideration the fine grained materials, one of the existing techniques is measurement of grain size by the Coulter Counter method. This method is based on the measuring the changes of electrolyte resistance during grains flow through the calibrated diaphragm. This method is relatively simple to apply, significantly precise and the results are given quickly. However, the problem is that the measurements are limited by the size of diaphragm. Because of this situation, measurement of grain sizes by this instrument is possible in range from 10% to 60% of diaphragm diameter. This limitation causes the necessity of re-placing diaphragm in case when the measured grain size distribution concerns the material of large size range. In purpose of determining the total grain size distribution, the synthesis of some partial distributions, given for individual grain fractions (with different diaphragm applied), is required. This is possible to do by calculating the mixture of distribution functions, created from the partial distribution functions. Two materials were selected to research: quartzite and glass, which were comminuted in cylindrical crusher, additionally grinded, screened and then analyzed by Coulter Counter for five grain fractions: 0~125 µm, 0~80 µm, 0~56 µm, 0~40 µm and 0~25 µm. For each fraction, five different partial distributions were given (in case of glass ? four), which are the basis for the creating the joined grain composition. To assure the adequacy of the given distribution function, it is necessary to obtain the possibly best approximation of partial distributions. In the work, both the parametric and non-parametric methods of density approximations of investigated random variable. For each grain fraction the approximations were done by three traditional distribution functions: RRB, GSA and log-norm distribution functions and three methods of non-parametric approximation: Gauss kernel, Epanechnikov kernel and orthogonal Fourier series method. As the criterion of the certain distribution function acceptance, the value of the residual deviation was assumed, given by the formulae:

Jan 1, 2014

By William Hissem

The topics in the title line of this article are desirable and applicable to entire industries that exist outside the realm of the ISEE’s readership. But the issues I will discuss herein are specific to those who drill, blast, and excavate rock as part of their business. Civil and site construction projects, mines, and quarries specifically comprise the group who will benefit from this discussion.

Jan 1, 2014

By Megan Becker, Cyril O’Connor, Jenny Wiese, Gaynor Yorath

The effect of particle shape on true flotation has been widely reported. The present paper presents results obtained in investigating the effect of particle shape on the entrainment of particles during the flotation process. Different hydrophilic minerals with particles of varying aspect ratios were used and their shape determined using rheological tests and QEMSCAN. Their entrainment properties showed a close relationship to their shape with the recovery due to entrainment increasing as the aspect ratio of the particles increased. The effect of surface charge, by changing pH, and size of particles showed that the effect of shape was sustained at different pHs and particle sizes. Proposals are made to explain these observations in terms of the known relationships between drag coefficients and terminal velocities and shape. Since it has been previously reported that different milling procedures can affect particle shape, these results indicate that it is possible that such different procedures may result in increased entrainment of hydrophilic minerals.

Jan 1, 2014

By W. P. Roux

Owing to decreasing high-grade ore reserves, there is a need for better understanding of the jigging process to improve the recovery efficiency of finer, lower grade material. The use of positron emission particle tracking (PEPT) was examined as a technique to study the motion of iron ore particles inside a laboratory batch jig. PEPT is a non-invasive method that can provide three-dimensional kinetic data on a particle in laboratory-scale processing units and has been successfully used to study mills, hydrocyclones, and flotation. Experiments were conducted to determine whether PEPT would be a viable technique to study iron ore jigging and what valuable information could be obtained. The results indicated that detailed information on the stratification rate of a particle could be obtained, with adequate resolution to track the particle?s movement through an individual jig pulse.

Jan 1, 2014

By R. G. Coyle

"In an earlier paper the author explored the consequences of price-stabilizing effects, on an industry-wide basis, of various production strategies. These ideas have now been applied to an illustrative case of an individual mine. It is shown that the turning of production and financial policies can affect financial performance over a five-year period by as much as 22 per cent.No generality is claimed for the results and they would differ from mine to mine. It is, however, asserted that the results show that the proper turning of production, reserves and financial policies are more critical determinants of mine performance than has been realised. It is also asserted that the methods of dynamic analysis are the most appropriate means for studying this policy-design problem."

Jan 1, 2014

By John A. Wells, Leticia Conca, Kenneth G. Thomas

"Since about 2002 there has been significant capital cost escalation, not inflation, in the mining industry causing turmoil for successful project completion. Project capital costs have more than doubled and some cases tripled in this time period. This has rendered many projects to be economically challenged and in some cases not viable. In addition higher than expected operating costs have further adversely affected project metrics such as NPV and IRR. Capital cost increases for projects have been widely reported globally. This current paper reviews three items. Firstly, why such capital increases and the various components that make up capital estimates. Secondly, it looks at reasons why preliminary estimates, for example at scoping and pre-feasibility level, have been lower than the ultimate constructed costs. Such increases and differences in estimates have caused major problems for mine builders and have led to a general nervousness on the part of those providing project finance. Thirdly, what discipline is needed in project execution in an attempt to mitigate such capital increases. The paper will hopefully give a better understanding of the various issues and factors involved for those in the mining industry.INTRODUCTION The years 2012 and 2013 were a turbulent time for the mining industry. The European economic crisis, politics, metal price volatility and a wave of changes of CEO´s in some of the major mining companies all contributed to a challenging couple of years. Two issues stood out. First, the huge increases reported in the capital costs of projects, where increases of 100% - 300% were not uncommon and in some cases exceeded that during the first decade of the 21st century. Second, company write downs related to takeovers during the boom and the stabilization/correction in commodity prices. These have led to great uncertainty, made it difficult (or impossible) to raise project financing costs, contributed to the changes at CEO level and placed many projects either on hold or cancelled altogether. It is commonplace now to read of companies talking of reduced capital expenditure and making a complete review of their projects and operations to contain costs."

Jan 1, 2014

By Aidan Giblett, Karen McCaffery, Robert Dunne

"A worldwide decline in competency levels of practicing metallurgists over recent decades has become clearly evident and is a common topic of discussion among senior practitioners and professional associations. The associated impacts on the industry are material and include operational inefficiencies, missed optimisation opportunities and suboptimal new plant designs. There are many contributing factors to this condition. Decrease in competency is particularly evident both in regions where imbalance between supply and demand has led to a general reduction in experience levels for comparable roles over time and in emerging regions where a rapid rise in demand for practitioners has occurred in conjunction with rapid economic development and industrialization. The context, depth and breadth of education curricula and levels vary with location such that solutions to the technical competency dilemma may need to be developed specifically for each region with these influences in mind. Delivering, demonstrating and maintaining competencies are a critical requirement of undergraduate training and ongoing professional development. Other factors such as generational and cultural characteristics and expectations, political influences, role requirements and employment reward and recognition systems all play a critical role in determining if core competencies can be effectively developed, applied and subsequently maintained. This paper reviews factors impacting and some common approaches to competency development. The authors’ experiences in the management of professional development efforts within the global industry are reviewed and a blueprint proposed to address industry requirements in this area."

Jan 1, 2014

"Chairman: Professor H. S. SICHEL Rapporteur: Miss M. I. WATSONPapers:Unrolling of Copperbelt orebodies by J. H. E. Perry and V. H. WiikAn exploration model for tabular orebodies by G. S. Koch and R. F. LinkHarmonic analysis of copper and gold occurrences in the Arbitibi area of the Canadian Shield by F. P. Agterberg and A. G. FabbriMathematical models of orebodies by M. J. Newton and A. G. Royle Estimation of lateritic-type orebodies by A. JournelIn his presentation Mr Wiik said that unrolling could be regarded as a reversal of the natural process of folding, so that the aim of an unrolling procedure would be the reconstruction of original pre-tectonic conditions. While simply formulated, this aim might not always be achieved. The geometrical relationship between points on the deformed surface and corresponding points on the original surface is process-dependent, and a true reconstruction could be achieved only if the deformation history were known in detail.In this computer unrolling procedure all these complexities were ignored. Referring to one particular marker horizon, Mr Wiik said that it was assumed in the procedure that this marker was deposited as a horizontal stratum and that it had subsequently been deformed by simple flexure-type folding.The procedure allowed the geologist to incorporate his knowledge and conception of the deposit through repeated re-contouring with dummy points. This 'manumatic' aspect of the procedure had proved invaluable, not only in resolving specific unrolling problems but also in making the system more acceptable to the geologists in general.Unrolling served towards removing what might be termed `tectonic noise' superimposed on the primary distribution patterns for regionalized variables such as metal content and orebody thickness. From this point of view, variograms derived on the basis of unrolled-plan co-ordinates should be more meaningful in terms of depositional environment than are variograms calculated from a normal map projection.Mr M. M. Oosterveld remarked that it appeared from the paper that there were problems in applying the unrolling technique to ore reserve calculation, and asked whether there were not other methods that might be used for that purpose.Mr Wiik replied that at present unrolling played only a minor role in practical ore reserve estimation within Roan Consolidated Mines, Limited. The techniques currently in use differed from one orebody to another, but in general they involved projection onto a vertical longitudinal section or a horizontal plan, with subsequent grid interpolation by means of a standard computer contouring package."

Jan 1, 2014

By Dee Bradshaw

"Process mineralogy’ is a form of applied mineralogy which focuses on addressing problems associated with the processing of ores. ‘Mineralogy’ is the scientific study of minerals and ‘mineral processing’ is the production of concentrates from ores. ‘Process mineralogy,’ however can be defined as the practical study of minerals associated with the processing of ores, concentrates and smelter products for the development and optimisation of metallurgical flowsheets, including the waste and environmental management considerations. This hybrid discipline consists of teams that include geologists, mineralogists, samplers, mineral processors and often others, working together. The degree of cross-training, communication and trust dictates the potential capacity of the team and where an appropriate work dynamic is fostered, in which relationships flourish as much as does the ethic of technical excellence, it is possible to develop technical capabilities that surpass those of conventional teams. The world’s demand for metals is ever increasing and ore deposits available for extraction and processing are lower grade and more complex, often containing deleterious elements that require tailored treatment. Generally, in the past, the technical challenges only needed to be overcome and assessed economically to make an ore deposit viable; increasingly and in the future, a more sustainable approach including environmental and societal considerations is needed. Process mineralogical assessment is increasingly providing the critical information that stands between failure or collapse and survival or success of some mining operations. In this paper, selected case studies are used to demonstrate the valuable role of the process mineralogy tools being used to provide the platform for innovative technology development. Their common attributes are discussed and distilled, thus providing some insights and potential guidance for addressing some of the likely future challenges of the mining industry."

Jan 1, 2014

By Thomas V. Fame, William E. Porter

"As geological and mining conditions become more complex, and as overall mining economics become more marginal, short- and long-range decision-making regarding multiple-seam surface mining becomes more difficult. The decision-making problem involves a study of economics, cut-off grades and ratios, equipment capabilities, sequencing and selective mining practices.This paper is concerned primarily with multiple-seam mining of bituminous coal. The research has led to the development of an economic decision-making model for use as a day-to-day tool to aid mine operators and pit geologists to decide what and how to mine.The model is designed as an aid for feasibility decision-making in multiple-scam situations and for situations where selective mining is needed or desired. In effect, a simulation of the feasibility and preliminary mine planning phases has been developed. The model is divided into four separate segments: decision-making, simulated mining, cost calculations and the determination of the discounted cash flow return on investment."

Jan 1, 2014

By Moris Fresko, Julia Sun, Charles C. Golembewski, Vytas Svalbonas

"A history of mill strain gaging at Metso is presented. The output of these strain-gaging programs is compared with calculated stress ranges from different finite element solutions. These comparisons expose the amount of approximation that exists in the analytical solutions, starting from geometry, and material properties, and ending with different forms of internal load models. The influence of strain gaging results on mill design and analysis practices is also discussed. While these instrumentation programs are valuable in identifying areas of high stress in mills, and locations of stress concentration factors, they are by no means extensive or comprehensive enough to verify general internal load models. The vast majority of the programs were aimed at getting additional data about potential failure points, rather than describing overall mill stress behavior. This is especially true since the more recent gaging programs have not included the difficult task of gaging the mill rotating structure interior. This paper tries to avoid the novice path of leaping to general conclusions on the basis of insufficient data."

Jan 1, 2014

By G. Belardi

This paper presents the preliminary results of a research programme conducted to assess the feasibility of a flotation technique in the remediation of soils severely affected by heavy metal contamination. The use of flotation in soil remediation is a recent practice. The main difficulties are given by the variety and peculiarity of the heavy metal containing species, and also by the grain size. Most of the studies reported in the literature concern the use of conventional collectors, such as xanthates, after a preliminary chemical modification of the metal bearing species through sulphidization. On the basis of the minera-petrographic characterization and of speciation, some classes of reagents have been selected, capable of acting both on metal-bearing species and all metallic cations to be separated. The design of the synthetic molecules has been based on the coordinative properties of the metallic centres and functionalized in order to act as collectors for a wide range of metals independently on their surrounding atoms. In laboratory experiments a sample of stream sediment has been utilized, whose contamination is caused by the runoff from Sardinia mine waste dumps and overflow from the settling ponds. The material showed contamination mainly from Zn, Pb and Cu and to a lesser extent from Cr, Ni, Cd, and Sb associated in mixed particles of Fe and Mn. Flotation tests on a laboratory scale have been performed on grain sizes less than 355 µm in laboratory cell Minerais & Metaux. The effects of the structure of collectors (functional group, chain configuration) as well as of the principal flotation parameters (such as pH, concentration of reagent) on the grade and recovery of heavy metals in the concentrate and in the tailings (remediated soil) have been investigated. The results of the laboratory tests substantially confirm the theoretical premises, and the most effecive reagents found belong to the classes ATP, MBT, MBO, fat acids and phosphates.

Jan 1, 2014