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By E. T. Tuzcu

Microscale information about single particle fracture can be incorporated into the macroscale model of the whole size reduction process in the mill. The ultrafast load cell (UFLC) device provides a substantial amount of information about fracture characteristics of a particle under impact loading. UFLC captures high-resolution compressive force signals during particle breakage. The measurement of the compressive force at the instant of fracture of the particle allows computation of a number of comminution-related particle properties, as well as the energy absorbed during fracture. In the current study, limestone particles 50 mm in size were fractured to obtain specific fracture energies. Then, based on the experimental data, two models were proposed to quantify the fracture process. The specific fracture energy distribution of the particles in the range of 6 to 50 mm was defined by the well-known Weibull distribution. The other model is a probabilistic fracture model. This model is a link between energy events occurring in a grinding mill and the breakage rates of particles. The impact energy spectra or energy events occurring in a grinding mill can be obtained with a discrete element method (DEM) simulation. One can model the breakage rates of the mill material by combining the energy spectra with the probabilistic fracture model. This novel approach for the modeling of breakage rates via DEM and UFLC is shown here.

Jan 1, 2011

By M. Mai Manga, M. Renaud, A. Faucher, C. Bazin

ABSTRACT Grinding circuits are operated in the presence of disturbances resulting from ore changes and equipment malfunctions, such as hydrocyclone overloading, worn or partly plugged apexes, surging, and internal liner detachment that may cause a loss of classification performance. Metal recovery losses in downstream leaching or flotation circuits justify the development of methods for rapid detection of hydrocyclone malfunction. Two methods are presented in this paper. The first method uses measurements from sensors available in a grinding circuit and the second uses vibration sensors installed on the individual hydrocyclones of a nest.

Jan 1, 2011

By G. Balletto, C. Furcas

"The mineral raw materials industry is a key-component of the Gross Domestic Product of industrialised economies, closely related to both the building and the industrial sectors. Despite this, at local level mining and quarrying are associated with both irreversible environmental damage and several visual alterations affecting the natural landscape. In this sense, SIA (Social Impact Assessment) has become a strategic tool that can not only improve the prediction but also the assessment of the social impact by involving the local communities in a participatory process. Taking into account the SIA experience, together with the examination of some relevant international case studies, it is possible to draw up a list of good practices for mining project management, from exploration through to closure and beyond, with quarry restoration. Such good practices will complement the existing studies, focusing on environmental issues, with the social issues arisen considered in SIA application."

Jan 1, 2011

By F. Díaz-Fierros, D. Rubinos, M. T. Barral

The present work explores the reutilization of red mud, an industrial waste arising from the production of alumina, as a component of isolation technologies for hazardous substances. The work involved the study and optimisation of the geotechnical properties of red mud in conjunction with adsorption experiments of As(V) and Hg(II). The results from both types of experiments were integrated in a dispersion-diffusion model to calculate migration curves and minimum thickness of the red mud compacted layer. The geotechnical studies showed that compaction increased the stability and decreased the hydraulic conductivity of red mud barrier. Red mud sorbed high amounts of As (up to 44 mmmol kg-1) and Hg (up to 9.2 mmmol kg-1). The calculated minimum thickness of the red mud barrier was 1-10 cm for As and 2-19 cm for Hg, for an operation period of 35 years. The results obtained let to conclude that the reuse of red mud as a component of isolation systems of hazardous substances represents a viable alternative use of this residue.

Jan 1, 2011

By I. Nimmo

Since the beginning of Aluminum mining and refining the industry has lived with distributed control rooms and suffered from many behavioral problems common with this design. When Human Factor/Ergonomic design is introduced to a Western Australian installation a common centralized control room realized many improvements including economic payback. Communications issues were resolved, better coordination of materials, improved situation awareness during startups, abnormal operations and an opportunity to make improvements during normal operations characterize the changes at the Worsley Refinery. This presentation will review the reasons for the change. Since the beginning of Aluminum mining and refining the industry has lived with distributed control rooms and suffered from many behavioral problems common with this design. When Human Factor/Ergonomic design is introduced to a Western Australian installation a common centralized control room realized many improvements including economic payback. This presentation will review the reasons for the change, what changed and the process of changing the culture from reactive to predictive and what difference that has made.

Jan 1, 2011

By A. S. H. Kabir

Due to the high specific strength and excellent corrosion resistance, Ti-6A1-4V has been widely applied in aerospace industries. In this study, the welding performance of 3.2-mm and 5.1-mm thick Ti¬6A1-4V sheets was studied using a 4 kW continuous wave Nd: YAG laser. It is found that the use of filler wire, matching the parent metal composition, can bridge the joint gap and produce full penetrated welds up to a width of 0.6 mm without cracking. The laser welds were characterized in terms of the bead geometry, defects, microstructures, and hardness. With increasing joint gap, the percent porosity area increased, reaching just over 1% of the fusion zone area at a gap width of 0.6 mm for the 3.2 mm and 5.1 mm thick sheets. The maximum underfill depth in the Ti-6A1-4V laser welds was about 5% or 7% of the sheet thickness for the 3.2-mm and 5.2-mm thick materials, respectively, meeting the AWS D17-1 specification. The microindentation hardness was maximum in the fusion zone and sharply decreased through the heat affected zone until reaching the base metal value.

Jan 1, 2011

By W. G. Miller, J. D. Scott, D. C. Sego

ABSTRACT: As part of an overall study of properties and processes influencing consolidation of oil sands fine tailings resulting from different extraction processes, self-weight consolidation tests were per-formed. Fourteen 2 m and 1 m high standpipe tests were instrumented to monitor the rate and magnitude of consolidation of seven fine tailings materials. Tests provided valuable information about the variation of consolidation related to differences in fine tailings material properties that result from a change in bitu-men extraction process (caustic versus non-caustic). In addition, the effect of adding a coagulant to caustic fine tailings was measured. Test results are presented and discussed in terms of consolidation rate long-term volume decrease, compressibility, and downward drainage. Non-caustic fine tailings had fasterinitial consolidation, which is important in tailings ponds for reducing storage capacity and returning decant water at a faster rate to the extraction plant. Similar results were obtained for caustic fine tailings with a coagulant addition. However, long-term settlement of the different fine tailings appears to con-verge to a similar value over time because it is then governed by effective stress.

Jan 1, 2011

By J. E. Dutrizac, Alba Sunyer

The factors affecting the precipitation of arsenic-free alunite (KAl3(SO4)2(OH)6) were investigated in a series of laboratory experiments. Although the amount of alunite precipitated increased with increasing retention time, temperature, solution pH and the concentrations of Al(SO4)1.5 or K2SO4, the composition of the products remained nearly constant. The preferred conditions identified for the precipitation of arsenic-free alunite were then used to assess the behaviour As(III) and As(V) during alunite precipitation at 98°C. Increasing additions of As(III), as NaAsO2 or As2O3, resulted in a slight increase in the amount of precipitate formed at pH 2.80. However, X-ray diffraction analysis showed all the precipitates to be alunite, and <0.2% As(III) was detected in the products. In contrast, increasing additions of As(V), as KH2AsO4 or As2O5, resulted in significant increases in the amount of precipitate formed at pH 2.80 or 3.00. Furthermore, the arsenate (AsO43-) contents of the precipitates increased up to 15%, and the sulphate contents decreased, as the As(V) concentration of the synthesis solution increased from 0 to 9 g/L. X-ray diffraction analysis of the products detected only alunite, but there was a progressive expansion of the alunite cell with increasing arsenate content. The implication is that arsenate substitutes for sulphate in the alunite structure. Preliminary observations on the environmental stability of the arsenate-bearing alunite using the TCLP protocol gave solubilities <0.4 mg/L from a precipitate containing 8.5% AsO4 and 7.8 mg/L from a product containing 19.5% AsO4. Thus, it appears that alunites containing less than -10% AsO4 would be an acceptable vehicle for the disposal of arsenic from hydrometallurgical processing solutions.

Jan 1, 2011

By Shenghui Guo, Ying Lei, Hao Niu, Huilong Luo, Jinhui Peng, Libo Zhang, Yu Li

"In this work, the combination of microwave drying (MWD) and heat pump drying (HPD) drying experiments were designed by response surface methodology (RSM) based on central composite design (CCD) using design expert software (Version 7.15), and the process parameters were optimized. The conditions given by software are: the MWD time is 4.6 or 4.4 min; the HPD time is 9.0 or 8.6 min; and the sample mass is 620 or 600 g. Under those conditions the moisture content is 1.0 10-2kg water/kg wet basis, and the effectiveness ratio is 0.70 kg water/kwh. The results of confirmatory experiments conducted under the optimized conditions show the combined drying have superiority of decrease of energy consumption and increase of handling capacity over the single MWD or HPD.1 IntroductionSilica sand is one of a silicate mineral with properties as hard, anti-friction and less reactive, commonly used as raw material for foundry and construction. The silica sand obtained from mineral dressing processes such as scrubbing, magnetic separation and flotation. Its moisture content is approximately 0.08~0.12 kg water/kg wet basis. The most common methods used for drying are solar drying and hot air drying. But these methods have some shortcomings: for example, the solar drying has longer process time due to low energy yield, [1] hot air drying has low-energy efficiency and a lengthy drying time. [2]Microwave is electromagnetic waves with frequency are 300MHz to 300GHz. The outstanding features of microwave heating are rapidity and selectivity. The water specific inductive capacity of 60~78 is much bigger than common materials, the moisture always quickly absorb electromagnetic wave and rapidly transfer to vapors. So, it can significant reduce the drying time. [3] Heat pumps (HPs) are devices for raising the temperature of low grade heat energy to a more useful level using a relatively small amount of high grade energy."

Jan 1, 2011

By D. Brandt

The Dos Pobres Mine is a copper oxide heap-leach mine located near Safford, Arizona. Mine production is 180,000 tons (163,293 tonnes) per day with a stripping ratio of 2:1. During the startup phase of the mine, the required fragmentation size was easy to achieve as the ore was highly weathered and fractured near the surface. As the mine depth increased, the proper fragmentation size became harder to achieve due to less weathering and different rock types. Because copper recovery increases as crusher product size decreases, achieving the appropriate product size at the crusher is the operating priority. The Engineering Department started a project to improve fragmentation through blasting and thus increase throughput in the crushing system. It soon became clear that input from other departments was going to be required to make this a safe and economical project. Therefore the Crush and Convey and Ore Control departments worked together to evaluate all available data on blast patterns and explosive loads and tracked performance and results. Using image analysis, Drill Energy Index and databases, we have been able to improve fragmentation size and verify the results while controlling costs.

Jan 1, 2011

By Sunil Koppalkar, Guillaume Noel, Ahmed Bouajila, Makni Sami, Claude Gagnon

"Gold gravity recovery circuits utilizing enhanced gravity separators have become an integral part of many of the modern gold processing plants. Thus, efforts to improve the operating efficiency have been a topic of interest for metallurgists for many years. As part of this endeavour, a methodology to estimate the portion of gold in the ore that could be recovered by gravity separation (gravity recoverable gold or GRG) was developed at McGill University. It has been reported in the literature that the gold content estimated with this methodology is the theoretical maximum that is available for gravity recovery that could only be approached but never achieved. A comparison of GRG recovery obtained in the laboratory with the actual recovery in the plant shows that plants recover between one-third to two-thirds of the value predicted by the laboratory test.Research conducted at COREM shows that particle shape transformation during grinding is a major cause of the discrepancy (even though the bleed percent processed, the quality of cyclone classification and the operating conditions of the gravity separator also contribute to the difference). To analyze the gold particle shapes and their deportment, samples were collected from different streams of a grinding-gravity circuit in a gold plant and compared to a concentrate sample from the standard GRG test. A particle characterization methodology based on gold morphology was developed. GRG mapping in a conventional grinding-gravity circuit and the transformation of GRG into non-GRG, as mainly explained by gold particle reshaping, will be discussed. The knowledge gained from the shape analysis will be used to develop shape distributions and partition curves for the classification of shapes.INTRODUCTIONGravity concentration using centrifugal concentrators has gained increasing popularity since the invention of the enhanced gravity concentrators in the nineteen eighties. Among these, the semicontinuous centrifugal gravity concentrators are most commonly used for recovering gold and platinum group minerals (PGM) from grinding circuit streams. The benefits of gold gravity recovery are now well understood and the acceptance by the mining industry is overwhelming. The occurrence of reasonable amounts of gravity recoverable gold (GRG) in an ore prompts gold mills to install gravity circuits. Thus, the increased use of gravity concentration has necessitated a better understanding of the behavior of gold in grinding circuits and of the factors affecting the performance of the gravity concentrator (Laplante et al., 1995). Due to its high density (19.3 g/cm3 when pure) and malleability properties, gold tends to accumulate in circulating streams making it attractive for gravity recovery. The gravity recovery units are typically installed on a bleed stream of the cyclone underflow, mill discharge or cyclone feed."

Jan 1, 2011

By Clemens Schmetterer, Patrick J. Masset

"The surface tension represents an important property for the modelling of high temperature processes. In this study the surface tension of two Al2O3 – CaO – SiO2 model slags and the influence of the admixture of 5 up to 30 wt.% FeO were studied. The surface tension measurements were carried out using the sessile drop technique on BN substrates under Ar atmosphere (10-6 atm O2) up to 1500 °C.IntroductionThe aim of VIRTUHCON1 is the virtualization of high temperature conversion processes, a task that requires thorough understanding of these processes. In many of these conversion processes slag plays an important role to control the properties of the product, to protect the reactor lining or simply as waste. Slag surface tension is one of the materials properties that is needed for the description of such processes, since it influences the interactions between the components in the reactor, e.g. at the slag – Fe interface in the blast furnace.Surface and interfacial tensions have thus received considerable attention in research, but the number of investigations in this particular pseudo-quaternary system is surprisingly low. Furthermore, the literature data are subject to different measurement conditions and techniques which complicates the data analysis and comparison.The slag atlas [1] offers a compilation of the available literature until 1986 (shown in Table I), but literature search has not revealed more recent studies of this system until now. For example, Elliott and Mounier [2] determined the surface tension of ACSF slags using the double tube maximum bubble pressure technique at 1200 °C. They kept their slags in contact with Cu-S-F mattes, and the slag therefore contained a certain amount of sulphur which acts as a surfactant and lowers the surface tension. The compositions of their slags were scattered over a wide composition range and they did not use a common ACS base mixture for their tests, either. The surface tension values vary between 417 and 446 mN/m, but due to the reasons just mentioned no trend in the measurements can be observed and the influence of FeO admixture on the surface tension cannot be deduced. Further information including the temperature dependence is available from Pavlov et al. [3], Ishchanov and Shushkov [4] and Murav’eva and Kaplun [5]; the diagram on page 446 in Ref. [1] has been drawn from these sources. Both positive and negative temperature coefficients are reported in these works. SiO2 is the only pure constituent that has a positive temperature coefficient [6], but a correlation of the temperature coefficient with the SiO2 content was not found to be conclusive."

Jan 1, 2011

By Jim Huerta

Diesel fuel usage in the mining industry continues to escalate. This is because approximately 60 percent of all mined materials are surface extracted by large equipment using diesel fuel, which continues to increase in cost per gallon. For example, coal mining uses large equipment such as wheel loaders, wheel dozers, draglines and [ ] dredgers. In one year, three of the largest U.S. coal mining operations consumed approximately 567 million to 852 million L (150 million to 225 million gal) of diesel. At an approximate cost average of $3.25/gal the expenditure on diesel is $487 million to $731 million per year. So, are there any solutions that could reduce this cost burden? Yes, there are. Coal mining companies can extract less ore; use more efficient extracting equipment that consumes less fuel; wait for a significant reduction in the cost of fuel; or find and use technology that would create efficiencies that would lower the cost. Nanotechnology is one such technology that might provide the means to create the efficiencies that will significantly lower diesel fuel costs.

Jan 1, 2011

By Helmut Mischo

For more than 100 years, diamond mining has been Namibia?s most important mining sector. Today, it provides the highest foreign currency income for the country?s development. Since the late 1970s, offshore mining of diamonds has gained more importance and now more than 60 percent of Namibia?s generally high-quality stones come from those offshore deposits, with a steady increase expected for the coming years. Diamonds in Namibia The mining industry is one of the three pillars of the Namibian economic development, along with tourism and fishing. Diamond mining is one of the two main mining activities in Namibia and diamond mining operations are rapidly moving from onshore to offshore deposits. This article provides a comprehensive overview of the current and future situation of the Namibian mining industry, with a special focus on the tasks and new technical developments for the successful excavation of beach and marine diamond deposits. The different deposits and the adequate applied mining technologies and methods are shown in examples.

Jan 1, 2011

By D. Bogh

Wound rotor motors are used in difficult mining applications where there is a need to start high inertia, hard starting loads while limiting inrush current They are recognized as robust and simple to control. This paper will cover the performance, specification, and important issues to be considered when applying medium voltage wound rotor motors in mining applications. Medium voltage grinding, crusher, and conveyor applications will be discussed. Specifically covered are motor efficiency, speed range, and rotor control. Crane motors often have wound rotor construction, but their load cycle and ratings are outside the scope of this paper.

Jan 1, 2011

By Qingchun Yu, Baoqiang Xu, Yongnian Dai, Bin Yang, Fulong Zhu

"In this paper, the mechanism of the carbothermic reduction-chlorination process to extract aluminum from alumina in vacuum was investigated. The carbon monoxide (CO) content of the gas, phases of the reduction slag, surface morphology of the reduction slag and the product aluminum were measured by means of gas chromatography (GC), XRD, and SEM. The experimental results indicated that the content of CO in the gas decreased, but Al4C3 increased with time at 1773K during the carbothermic reduction process of alumina. AlCl(g) and graphite (C) were produced by the reaction between Al4C3 and AlCh(g) at 1773K, and then aluminum beads generated after the decomposition of AlCl(g). It implied the mechanism of alumina carbothermic reduction-chlorination process in vacuum involves three steps as follows: the carbothermic reduction of A}z03 to produce Al4C3, the chlorination of Al4C3 by AlCh(g) to produce AlCl(g), and the decomposition of AlCl(g) to produce Al(l).IntroductionAluminum is the basic raw material for many industries [1], and it is used extensively because of various excellent properties such as light weight, good malleability, high strength, excellent thermal conduction, high corrosion resistance and so on [2]. Industrial production of aluminum currently includes refining alumina and electrolytic aluminum processes. However, its development has been effected by some factors such as high energy consumption and heavy environmental burdens [3]. In the past several decades, there had been numerous attempts to produce aluminum by new methods. Extracting aluminum from alumina or bauxite directly by carbothermic reduction-chlorination process had been studied [ 4-6]. Although the alumina carbothermic reduction process [7~9] had been studied, the mechanism of the carbothermic reduction-chlorination process had not been systematically elucidated.In order to investigate the mechanism of the carbothermic reduction-chlorination process in vacuum, GC, XRD and SEM techniques will be used to determine the CO content and to characterize the surface morphology and composition of the slags at various temperatures."

Jan 1, 2011

By Jeremy Morris

The city of Indianapolis has more than 25,000 homes currently on septic systems. Many of these systems do not function well because of their age and surrounding soil conditions. As Indianapolis has worked to eliminate septic systems and install sanitary sewers in large unsewered areas on the north-west side, capacity of the existing Belmont North Interceptor (BNI) became a concern. The BNI system currently services an area of approximately 80 km2 (31 sq miles) located within the northwest quadrant of the city (Fig. 1). Monitoring of the existing interceptor indicated portions of the sys-tem flowing half- to two-thirds full during dry weather conditions and surcharging during some wet weather conditions. Further analysis of the BNI based on growth projections coupled with increased sewershed yield resulting from the city?s septic tank elimination program (STEP) indicated dry-weather flows could potentially triple over the next 20 years. Based on these modeling results and current wet weather capacity issues, the city determined further STEP projects could not be performed within the BNI service area until

Jan 1, 2011

By Joseph M. Kurtak

The Bureau of Mines conducted a four year (1985-1988) mineral assessment of the Juneau Mining District in southeast Alaska as part of its ongoing statewide mining district evaluation program. Following an extensive literature search, the Bureau investigated mines, prospects, and mineral occurrences in the area. This report describes the results of Bureau work in the Eagle River area of the Juneau gold belt; a component of the Juneau Mining District comprising 87,000 acres between the Mendenhall Glacier and Berners Bay. Gold and silver have been the only metals having significant production from the area and occur mainly in quartz stringer and fissure type veins hosted by phyllites, greenschists, greenstones, altered diorite dikes and quartz diorite gneiss. Gold also occurs in several small placer deposits. Approximately 21,100 oz of gold and nearly 9,000 oz of silver were produced over a 60 year period. Currently, the only mining activity consists of some exploration and minor placer gold production. Inferred and indicated lode gold resources having mineral development potential total approximately 796,000 tons with a weighted average grade of 0.22 oz/ton gold.

Jan 1, 2011

By Mark P. Meyer

During 1991 through 1993, the U.S. Bureau of Mines (Bureau) -Alaska Field Operations Center (AFOC) in cooperation with the Bureau of Land Management (BLM) -Arctic District Office and the State of Alaska, Division of Geological and Geophysical Surveys (ADGGS), conducted exploration, geological, geochemical, geophysical, mineral resource, and mineral potential investigations in the 6.7 million hectare Colville Mining District (CMD) study area. This mining district study area, located in northern Alaska, includes the Colville River drainage basin as well as 0.35 million hectares of the southern part of the National Petroleum Reserve in Alaska (NPRA). This investigation was conducted as part of the Bureau&apos;s continuing Mineral Land Assessment (MLA) mining district program. The Bureau&apos;s MLA mining district program is designed to provide reliable and comprehensive mineral resource information that supports mineral resource policy and land use decisions made by Congress and Federal land management agencies.

Jan 1, 2011

By W. G. Pariseau

This contribution focuses on the role of stress analysis for mine planning and the selection of suitable computer programs for the task with special emphasis on coal mine pillars. In this regard, barrier pillars that defend a set of five main entries at the Crandall Canyon coal mine in central Utah were formed during extensive longwall mining north and south of these main entries. Numerical analysis for ground control guided the mine planning and permitting. Retreat mining of pillars led to disastrous events August 6 and 16, 2007, with the loss of nine lives. A most difficult lesson taught by the Crandall Canyon tragedy is the need for education in the selection and use of computer programs for pillar design. Much of this contribution is taken from a report prepared for the Mine Safety and Health Administration (Gates, et al, 2008). Details appear in Appendix Q of the report (Pariseau, 2008). The Crandall Canyon mine is about 16 miles west of Huntington, Utah, in the Wasatch Plateau coal field. Geology of the Wasatch Plateau is described by Doelling (1972) as gently dipping Cretaceous sandstones, mudstones, coal seams, and shales. Joint systems are present in strata above and below coal seams where cleat systems are present as described by Hucka (1991). Several major fault systems transect the field and form grabens with 450- 760 m of drop. One such structure is Joes Valley fault that crosses the Crandall Canyon mine. Mines in the Wasatch Plateau are generally developed from outcrops in steep canyon walls. Overburden increases rapidly as mining progresses into the plateau; mining depth varies with topography between 450 and 600 m in the region of interest. A stratigraphic column derived from a borehole into the mine is shown in Figure 1. There are 11 layers in the column.

Jan 1, 2011