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By von Wielligh. L., D. G. Hattingh, M. N. James, W. Thomas

"SynopsisThe process of joining materials by friction is based on generating the heat necessary to create a solid-state mechanical bond between two faying surfaces to be joined. In simple terms, the components to be joined are subjected to frictional heating between rubbing surfaces, causing an increase in interface temperature and leading to localized softening of interface material, creating what is described as a ’third body’ plasticized layer. This plasticized zone reduces the energy input rate from frictional heating and hence prevents macroscopic melting. The plasticized layer can no longer transmit sufficient stress as it effectively behaves as a lubricant (Boldyrev and Voinov, 1980; Godet, 1984; Singer, 1998; Suery, Blandin, and Dendievel, 1994). The potential for this solid-state frictional joining process to create high-performance joints between, for example, dissimilar materials with limited detrimental metallurgical impact, and reduced defect population and residual stress level, has had a very significant impact on fabrication and repair in industrial sectors such as transport. This paper presents a brief overview of the advances made within the family of friction processing technologies that could potentially be exploited in the nuclear industry as alternative joining and repair techniques to fusion welding.Modern friction processing technologies can be placed into two main categories: those that make use of a consumable tool to achieve the intended repair or joint (friction stud and friction hydro-pillar processing) and those making use of a non-consumable tool (friction stir welding). The most mature friction joining technology is friction rotary welding, where a joint is formed between original parent materials only. A new addition in this category is linear friction welding, which opens the potential for joining complex near-net-shape geometries by friction heating. The continuous innovation in friction processing over the last 25 years has led to the development of a number of unique processes and applications, highlighting the adaptability of friction processes for specialized applications for high-value engineering components.IntroductionAssessing the potential for using alternative joining and repair techniques for specific applications in a given industrial sector is informed by an appreciation of the current size and potential growth in that sector. Power generation by nuclear fission has been out of favour over the past few years, due to several high-profile nuclear incidents, e.g. the Fukushima Daiichi nuclear disaster, as well as concerns over disposal of nuclear waste and spent fuel rods. However, due to rapid increases in the demand for electricity, coupled with many fossil-fuel fired plants reaching end-of-life, there is renewed interest in installing additional nuclear capacity."

Jan 1, 2015

By Christiaan Zeilstra, Jan van der Stel, Koen Meijer, Gerard Louwerse, Tim Peeters

The steel industry is producing about 5% of the world wide CO2 emission. Therefore the European steel industry has defined a research program to reduce the CO2 emission by 50% per ton: ULCOS. Since its start in 2004 ULCOS has identified four technologies for further development. Two of these technologies which produce liquid hot metal are discussed. The ULCOS blast furnace is based on recycling of decarbonated topgas and the capture and storage of CO2. The concept has been demonstrated during three campaigns at LKAB EBF in Luleå, Sweden. The smelting reduction process HIsarna is a combination of the cyclone-technology and Hismelt. The process has been demonstrated successfully in four campaigns at a pilot installation on the IJmuiden steelmaking site.

Jan 1, 2015

By Bai-ru Xia, Cang-qin Jia, Qi-wu Huang

Limit Analysis Theorems has revealed to be a powerful tool for the development of numerical models aiming the determination of the load bearing capacity of structures reached by plastic collapse. This work presents a numerical formulation for the computation of strict upper bounds of the collapse loads of rigid-perfectly plastic mechanical systems, derived within the kinematical theorem framework. A key advance of this present method is that the problem is described only in terms of nodes and discontinuities connecting those nodes rather than element or bodies. The alternative approximation procedure to the traditional finite element method might involve discretization of a given body using a suitably large number of nodes laid out on a grid, with the failure mechanism comprising the most critical subset of potential discontinuities interconnecting these nodes. Potential discontinuities which interlink nodes laid out across the problem domain are permitted to crossover one another, giving a much wider search space than when such discontinuities are located only at the edges of finite elements of fixed topology. Highly efficient interior point method solvers can be employed when certain popular failure criteria are specified (e.g. Mohr-Coulomb). By adopting this processing approach it is possible to solve very large problems which normally exceed the memory capacities of a single computer. The developed numerical tool reveals to be robust and versatile, able to solve a wide range of 2D problems. Velocity singularities are automatically identified and visual interpretation of the output is straightforward. Several numerical examples including rock slope are studied by the new method, and the results are very close to those calculated by using analytical method and FEM.

Jan 1, 2015

By K. Thuro, B. Sellmeier, M. Krautblatter

"Recent rockfall events, like the Tramin rockfall at January 21st, 2014, underline the significance of a comprehensive hazard assessment. A common way of estimating the hazard along infrastructure is the performance of run-out modelling using 3D rockfall codes like Rockyfor3D or RAMMS::Rockfall (Dorren, 2010, Bartelt et al., 2013). The potential block volumes are often roughly estimated from talus material and an overview of the source area, where the magnitude assessment is usually physically and intellectually demanding. Nevertheless especially for increased magnitudes, the volume estimation is crucial in terms of hazard analysis. Mid-Magnitude-Events exceed the load capacity of the most mitigation measures and their date of failure is hard to predict. Here we define the term Mid-Magnitude-Events as block volumes between boulder falls (10-100 m³) and block falls (100-10,000 m³) (Whalley, 1984).The current contribution provides an approach of integral process analysis for a 200 m3 carbonate block above the federal road B 305 near the city of Salzburg in the Bavarian Alps, Germany. We performed detailed analysis of the critical carbonate block exposed to planar failure. The block volume and the dimensions of the failure surface were mapped in detail, due to the unique occasion of an accessible failure surface. The discontinuity persistence was recorded to assess a minimal degree of fragmentation for a potential failure scenario. A maximum degree of fragmentation was estimated due to recording of block dimensions at the talus slope resulting from frequent rockfalls.We performed parameter studies in terms of run-out modelling using the code RAMMS::Rockfall (Bartelt et al., 2013), taking the recorded data for block fragmentation into account. In our contribution, we aim to demonstrate a comprehensive approach for hazard assessment of mid magnitude rockfalls, taking detachment processes, fragmentation and run-out analysis into account."

Jan 1, 2015

By Enzo Palumbo, Joël P. T. Kapusta, François Larouche

In light of the rapid deployment of bottom blowing smelting in China over the last ten years, one has to wonder why it has taken the copper industry so long to adopt ultra-high oxygen enrichment via Savard-Lee type injectors. As early as 1976, Kellogg and Henderson suggested, in their landmark paper on energy usage in the copper industry, that ‘maximum use of oxygen enrichment of process air’ was one of seven ‘energy saving features’ for copper matte smelting and converting. Yet today, shrouded injection and high oxygen enrichment has not been implemented in copper bath smelting outside China and Vietnam. In this paper, the authors explore the reasons why bath smelting processes such as the Noranda Reactor and the Teniente Converter still operate around 40% oxygen enrichment, while the bottom blowing SKS/BBS process typically runs at 65 to 75% oxygen, with all three processes producing white metal. Are there fundamental metallurgical explanations for this striking difference beyond the long-standing skepticism towards high oxygen shrouded injection and its perceived high implementation cost?

Jan 1, 2015

By Eduardo Lozano, Vilem Petr

The use of explosives bring countless benefits to our everyday lives in areas such as mining, oil and gas exploration, demolition or avalanche control. However, because of the potential destructive power of explosives, strict safety procedures must be an integral part of any explosives operation. The goal of this paper is to provide a solution against the hazards which unfortunately accompany the use of explosives. For this reason, a blast shield is specifically designed and tested for protecting personnel against these unpredictable effects. This document will develop a complete analysis answering the following questions: what are the potential hazards from an air blast; what are their effects; and how can we be protected against them. In order to answer these questions, theoretical, analytical, and numerical calculations are performed. Finally, a full blast shield prototype is tested under blasting conditions proving its effectiveness as a safety device while explosives are used.

Jan 1, 2015

By G. B. Harris, C. W. White

A study to investigate the recovery of base metals, notably copper, nickel, cobalt, zinc and manganese from iron-free concentrated chloride solutions using ion exchange was undertaken. In such solutions, apart from nickel and, to a lesser extent manganese, these metals are present predominantly as complex anions, and therefore conventional separation techniques based on cationic resins are not applicable. The results demonstrated that zinc, copper and cobalt can all be separately recovered leaving nickel and manganese behind. Specifically, zinc is a major nuisance element in nickel and cobalt processing, and the testwork showed that it can be preferentially removed prior to copper and cobalt. Selective resins for both copper and cobalt were identified, and it was demonstrated that the strength of the chloride background matrix has a significant effect on the efficiency of separation. An additional major advantage in such systems is that stripping can mostly be effected with water. Finally, some observations are made on the hurdles that must be overcome when attempting to introduce and commercialise new technologies.

Jan 1, 2015

By M. du Plessis, D. F. Malan

"Crush pillars are designed to be in a crushed state whilst being formed at the mining face. The residual stress state of these failed pillars provides a local support function in mining stopes and is used in the majority of the intermediate depth South African platinum mines. On mines utilising crush pillars, the pillar dimensions are selected to achieve a width to height ratio of approximately two. This is not achieved in most cases as a result of practical mining problems and poor pillar-cutting discipline. Furthermore, pillar dimensions are seldom adjusted to compensate for the various factors governing crush pillar behaviour. The pillars should, however, be in a crushed state whilst being formed or whilst still in close proximity to the mining face to prevent potential damaging seismicity.An underground investigation was conducted into the behaviour of the crush pillars in a trial site on the Merensky Reef at Lonmin Plc. The aim of this investigation was to examine the mechanism of pillar crushing and the related rock mass behaviour. The underground test results and pillar behaviour are compared to a limit equilibrium model to investigate if the model provides a useful approximation of the behaviour of the crush pillars. This paper details some of the preliminary findings.INTRODUCTIONOn most mining operations, the design of crush pillars is based on trial and error. As the pillar strength is unknown, the pillar sizes are adjusted to obtain the correct behaviour. Crush pillar dimensions are generally selected to give a width to height ratio (w:h) of approximately 2:1, (Ryder and Jager, 2002). Several factors affect the behaviour of the crush pillars and in many cases satisfactory pillar crushing is not achieved. This results in a seismic hazard in many of the mines using crush pillars. If pillar crushing is not initiated whilst the pillar is being formed at the mining face, as the mining face advances and the pillars move to the back area of a stope, some pillars may burst while oversized pillars may punch into the footwall. If pillars are designed in such a way that they are fractured during cutting by the face abutment stresses so that the pillars will already have yielded and reached their residual strength, further compression of the pillars will be associated with an increase in load and stability will be ensured, (Ozbay and Roberts, 1988). The stiffness of the strata must therefore be greater than the post-peak stiffness of the pillar (Figure 1) or violent pillar failure and hanging wall instability will occur. The pillar design should be aimed at determining pillar dimensions for which the post-peak curve of the pillar is as flat as possible."

Jan 1, 2015

By S. Hume, J. Shepherd

Meso-2,3-dimercaptosuccinic acid(DMSA) was studied as an additive for thiosulfate leaching of gold. DMSA was added to solutionscomposed of either sodium thiosulfate or calcium thiosulfate and the solutions were tested for their ability to leach pure gold samples as well as a calcined gold ore from Barrick Gold Corp. Results showed prolonged leaching of pure gold samples when DMSA was added at a concentration of 5µM; however, higher concentrations were shown to inhibit leaching. Differential capacitance measurements of the interface indicated that DMSA adsorbed as a defective monolayer on the surface of gold at low concentrations and formed a more compact monolayer with increased concentration. It is proposed that a concentration of 5µM DMSA produces a defectivemonolayer on the surface that still allowsthe transport of oxidants to the underling metal while inhibiting the formation of polysulfide passive layers that arise fromdecomposed thiosulfate.The 5µM DMSA/CaS2O3 system was also studied using calcined ore. Results showed that the initial leaching rates in the presence of DMSA are lower than those obtained in thiosulfate alone. However, after 10h, prolonged leaching is again observed when DMSA is included.

Jan 1, 2015

By Wilson Pascheto

One of the main outcomes of a capital project is the reliability of a new plant, system or equipment. During 20 years of experience working in various capital projects for the mining industry, the author experienced failures which have caused significant losses to Owners, in many cases amounting to millions of dollars and almost jeopardizing entire projects. Often, failures were related to faulty design, shop fabrication and/or construction. Therefore, significant opportunities exist in the Mining Industry to improve the success rate of capital projects, improve on-line time at start-up, minimize the occurrence of unplanned maintenance due to equipment failures, and all this with positive contribution to health and safety. This paper presents some examples of failures and how they could have been prevented by proper Quality Assurance methodology. It also discusses some of the main challenges in the implementation of such methodology, including awareness of the Materials discipline and availability of trained Engineers.

Jan 1, 2015

By Kazuyoshi Kamimura, Masaya Kawata

"It has been 30 years since the cement deep mixing (CDM) method developed in Japan. CDM method has been applied to many structures. While various technical improvements have been implemented in the meantime, the single-axial and double-axial technologies used at the time of its initial development are still prevalent.In response to the recent trend of reducing construction costs, we developed a triple-axial CDM method called the “Lemni 2/3 Method.” This method uses two lemniscate motions caused by newly developed auxiliary stirring devices and employs a double-axial injection method in which the cement slurry injection takes place only from the outer two axes. In this way, it is possible to create a stabilized body around the three axes. Moreover, this method does not require substantial equipment investment as conventional construction machine and facilities can be used without modification and large volume work is possible.With these technologies, this method can achieve a substantial reduction in the construction period and cost, while ensuring the same level of improvement quality as conventional methods. As a result, this method is being applied to ground improvement work in a variety of places.Lemni 2/3 Method was first put to practical use in 2004. Since then, the method has been used for ten projects. In this paper, we show some application examples of this method.OUTLINE OF TRIPLE-AXIAL CDM METHOD (LEMNI 2/3 METHOD)In the newly developed CDM method (Lemni 2/3 Method), work efficiency is improved by employing triple-axial stirring blades instead of the conventional single- or double-axial type. Existing conventional construction facilities for double-axial type can be used with only minor equipment additions, because the cement slurry injection takes place only from the outer two axes.Construction Machine and Construction MethodThe combination of major construction machines of the Lemni 2/3 Method differs little from the standard specifications of the double-axial type as shown in Fig. 1. Existing work control equipment can be used without modification, which is further evidence of the simplicity, convenience, and economy of the new method. The Fig. 2 photo shows a full view of the construction machine, and the Fig. 3 photo shows the stirring blades and the auxiliary stirring devices. The work procedure for the Lemni 2/3 Method is shown in Fig. 4."

Jan 1, 2015

By Khaled M. Mohamed, Michael M. Murphy, Ted M. Klemetti, Heather E. Lawson

"The design of rib support systems in U.S. coal mines is based primarily on local practices and experience. A better understanding of current rib support practices in U.S. coal mines is crucial for developing a sound engineering rib support design tool.The objective of this paper is to analyze the current practices of rib control in US coal mines. Twenty (20) underground coal mines were studied representing various coal basins, coal seams, geology, loading conditions, and rib control strategies.The key findings are: (1) any rib design guideline or tool should take into account external rib support as well as internal bolting; (2) rib bolts on their own cannot contain rib spall, especially in soft ribs subjected to significant load—external rib control devices such as mesh are required in such cases to contain rib sloughing; (3) the majority of the studied mines follow the overburden depth and entry height thresholds recommended by the Program Information Bulletin (PIB) 11-29; (4) potential rib instability occurred when certain geological features prevailed—these include draw slate and/or bone coal near the rib/roof line, claystone partings, and soft coal bench overlain by rock strata; (5) 47% of the studied rib spall was classified as blocky—this could indicate a high potential of rib hazards; and (6) rib injury rates of the studied mines for the last three years emphasize the need for more rib control management for mines operating at overburden depths between 500 ft and 1,000 ft.IntroductionEfforts to improve the stability of underground mine ribs have continued for decades. These efforts by mining professionals around the world persisted throughout the 1990s and 2000s as well, though much of this work focused on rib support methodology and selection of proper support for a specific location. Despite these efforts, it is unfortunate that there has been a continual occurrence of rib-related fatalities in underground coal mines. While overall improvements in rib safety have been achieved, the average fatality rate is still about 1.3 fatalities per year over the last 18 years (Jones, 2014).To manage and control the rib hazard, rib support is used in U.S. coal mines. The current rib support methods for U.S. mines fall into two main categories: rib control based on intrinsic support systems and those based on external support systems. Intrinsic or rib-bolt support requires a roof bolting machine that can install a bolt fixture into the rib. Furthermore, the appropriate level of support needed to control the ribs with an intrinsic-based support system as well as the design parameters for those support systems for various mine conditions have not been established in U.S. coal mines. Furthermore, surface control systems are often an integral part of these support systems and must be considered in the system design."

Jan 1, 2015

By Eric Lutz

"Great effort has been expended for more than 40 years to improve the workplace safety and health of surface and underground miners across the United States. When looking at the past decade, withstanding the 2010, Upper Big Branch (UBB) disaster that took the lives of 29 miners, this effort has resulted in a generally decreasing trend from 57 fatalities (22 coal; 35 metal/non-metal) in 2005, to 45 (16 coal; 29 m/ nm) in 2014. Through August of this year, there have been 23 mining-related deaths (eight coal; 15 m/nm). These results reflect continued diligence and perseverance on the part of miners that stay true to our legacy; and demonstrate significant investments from mine-site leadership, mining corporations, and state and federal regulators. However, over the past five years there have been an average of 32 fatalities per year, with a low of 36 (2011 and 2012) to a high of 45 (2014). If we know that there will be somewhere between 30 and 50 mining related deaths next year, which of us will volunteer to be counted as one of the numbered? Clearly, we all agree that one fatality is too many; and as evidenced by changes following UBB, deaths in any sector are deaths reflective of all mining across all sectors.The impact of each miner death touches us all. Miner’s deaths are felt deeply by family and friends, most significantly the children; their communities in which they served, supported, and worshiped; and by society that has lost a hardworking, dependable contributor. Further, to take a slightly cynical, but realistic view, miner fatality events impact the financial vitality of mining and contracting companies and broadly diminish investor confidence. Just as important, these events significantly impact our communities and result in negative public perceptions, which ultimately drive regulatory policy and related compliance pressures. This resulting pressure forces operations to broadly address safety and health gaps in very specific ways (i.e., see U.S. Mine Safety and Health Administration (MSHA) regulations regarding lids for trash cans) minimizing a mine site’s opportunities for operational flexibility. To break this cycle that is the operational reality, mining companies are focusing tremendous efforts on fatality prevention and specifically on dedicated investment to prevent multiple fatality events."

Jan 1, 2015

By Rob Boom, Yasuyuki Tozaki, Greg Traquair

The objectives of the business case are to examine a proposed metallurgical project and answer fundamental questions about project feasibility, risks, opportunities, and value. A business case fulfills these basic functions: estimates economic value; helps to understand competitiveness; serves as a risk management tool; and serves as a communication tool. A business case evolves with the project life cycle, and supports the gate reviews at the end of each phase of engineering, through to project construction and operations. A business case must be holistic, including all elements of scope that can impinge on project risk and value.

Jan 1, 2015

By M. Cai

"It is well known that Peak Particle Velocity (PPV) plays a critical role in triggering rockburst damage in burst-prone underground mines. To estimate the PPV distribution around excavations, advanced numerical modeling can be used. In wave propagation numerical modeling, velocity field is often assumed to be uniform around an excavation. However, it is observed that wave velocities near mine openings are not constant, but rather non-uniform. Wave velocity in a rock mass depends on many factors such as rock quality and confinement. In particular, confinement has a large influence on wave velocity. The confinement around an excavation is low at the wall boundary and increases gradually and reaches a constant value far away from the excavation boundary. Hence, stress redistribution due to excavation will have a profound influence on wave propagation in underground mines. A better understanding of the influence of excavation effect on wave propagation helps to interpret the field observation of rockburst damage and improve mine safety. For this purpose, a non-uniform velocity model need to be constructed and the influence excavation effect should be taken into account in numerical wave propagation modeling.In the present study, a non-linear velocity model is developed firstly by considering the influence of confinement on wave velocity. This model links wave velocity to confinement explicitly. A coupled numerical method is then developed and used to study the seismic wave pattern around excavations in underground mines. Two codes, FLAC and SPECFEM2D, are coupled in the analysis. The motivation of developing the FLAC/SPECFEM2D coupled approach is to take merit of each code, such as the stress analysis capability in FLAC and the powerful wave propagation analysis capability in SPECFEM2D. The coupling process is realized through three steps: (1) static stress redistribution around an excavation is analyzed in FLAC; (2) data for coupling analysis, such as non-uniform velocity field (based on the new developed velocity model), mesh, absorbing boundaries, etc., are generated by FISH functions in FLAC and passed to SPECFEM2D; and (3) wave propagation modeling is performed in the SPECFEM2D considering a fault-slip seismic source. Because stress redistribution around the excavation is considered, non-uniform velocity field for the SPECFEM2D model can be obtained and this is a notable feature of this study. Very large difference in the S-wave response in these two modeling approaches with uniform and non-uniform velocity fields can be seen from the modeling results.Using the FLAC/SPECFEM2D coupled modeling approach, accurate velocity models can be constructed and this in turn will help to produce accurate PPV distribution around the excavations. Accurate PPV contours can be used to identify high rockburst risk zones for improved dynamic ground support strategy."

Jan 1, 2015

By John J. Jonas, Hong Qin

Cylindrical samples of pure titanium were subjected to uniaxial compression at room temperature, leading to the formation of three generations of twins. Many primary contraction twins were observed as the initial texture was favourable for their formation. Numerous secondary extension twins formed within the primary contraction twins and some tertiary contraction twins within the secondary extension twins. The orientations of these three generations of twins were determined by electron backscatter diffraction techniques and their associated Schmid factors (SFs) were calculated. The formation of the twin variants selected in each generation and the absence of certain potential variants are accounted for by rotating the twinning displacement gradient tensor expressed in the twin system reference frame into the crystallographic reference frame of the relevant neighbouring grain. The presence of the observed primary, secondary and tertiary twins is explained in terms of the ease of imposing the required accommodation strains on the neighbouring grains. By contrast, certain first, second and third generation potential high SF twins were absent because their formation would have required accommodation by the most difficult deformation mode: pyramidal glide.

Jan 1, 2015

By Ambarish Ghosh, Subhaprasad Chakraborty

"Construction of basement floors has become necessary to meet the requirement of parking in office and residential complexes and in hospitals for radiotherapy treatment. Important projects coming up in Kolkata are mostly in closer proximity of residential buildings, office buildings and historical monuments. Sheet piling is mostly used as temporary shoring system during construction. Deep excavation in urban environment creates great problem related to construction induced vibration due to driving of sheet piles for basement, pile driving etc. which raises the chances of damage of adjacent buildings and nearby structures. Vibratory sheet-pile driving is the most common method of sheet pile installation. The knowledge of induced vibration due to this phenomenon is still very deficient. This paper presents the analysis of measured vibration data collected from different sites of Kolkata with varying soil profile. Typical two case studies of sheet pile and pile driving has been presented and the vibration values are analysed. The responses of the vibration are reported in terms of peak particle velocities (PPV). To evaluate the effects of vibration due to pile driving two aspects have been considered: the effect of the energy entering the ground from the pile and the effect of the soil condition.INTRODUCTIONIn urban areas infrastructure development projects are mainly located adjacent to existing structures like residential buildings, offices and historical structures. The construction work of such project influences the surrounding environment as well as human perception (Wiss 1981). During the construction of basement for residential complexes and hospitals sheet piling is mostly used as temporary shoring system or as to support the earth mass. The vibration induced due to driving of piles and sheet piles have been presented herein. Deep excavation projects close to existing structures increase the concern of environmental impact. For this reason the vibration assessment and prediction has become a subject of great interest. It is important to develop a site specific model for predicting the ground vibration resulting from pile and sheet pile driving at the construction sites. The developed model gives the efficacy to guide the engineer to select the construction methodology ensuring the safety of the surrounding structure. The model developed here is site specific and the parameters that has been used are dependent on the soil condition and the energy source."

Jan 1, 2015

By J. Andres

"Freeport-McMoRan’s Sierrita operations refines molybdenum disulfide in a ferric chloride leach to remove impurities. To understand bottlenecks in the leach process and the true capacity of the leach system, a cross-functional team was established to look at theoretical models, kinetics of the leaching process, equipment limitations and operational strategies. A series of in-plant tests were run which resulted in a road map for improved throughput. INTRODUCTION Molybdenum, a vital component in the steel industry, is often found in nature as molybdenum disulfide (MoS2). Molybdenum disulfide deposits can exist as standalone components in an ore body, or can also be found within copper porphyry nodes. Processing for these copper/molybdenum porphyry ore bodies involves a first stage of flotation to produce a bulk concentrate before separation of the copper and molybdenum concentrates in a second stage of flotation. In this second stage of flotation, a reagent is added to suppress the copper particles, while allowing the molybdenum disulfide particles to remain hydrophobic and continue to float. This separation is very good at keeping the molybdenum out of the copper concentrate; however a portion of the copper continues to float through the circuit. As a result, there is typically some amount of copper in the final molybdenum concentrate. This copper must be removed in order for the molybdenum disulfide product to meet product quality specifications. Once the raw molybdenum disulfide product has been made, a separate process must be applied to remove any copper, lead, or other impurities remaining in the concentrate. This process usually involves the selective leaching of impurities out of the bulk solid. Gupta mentions three specific types of leaching agents, sodium cyanide, ferric chloride, and hydrochloric acid for the removal of sulfide impurities. Sodium cyanide is useful for the removal of copper compounds such as bornite, covellite, and chalcocite.1 Sodium cyanide solution dissolves these copper compounds, and the remaining molybdenum solids are filtered to produce a pure molybdenum concentrate. Ferric chloride works similar to that of sodium cyanide, but is particularly efficient in removing chalcopyrite and galena compounds. These compounds are easily chlorinated at elevated temperatures, producing copper chloride and lead chloride, through the reactions presented below:"

Jan 1, 2015

By G. M. Scamans

In the past ten years there has been considerable penetration of aluminum automotive body sheet (ABS) into automotive structures. The exponential increase in demand is resulting in major investments in heat treatment and finishing capacity across the globe. Line speed and tonnage throughput is limited by the continuous heat treatment (CHT) floater furnace rather than the cleaning and pretreatment section where electrolytic treatments that offer higher line speeds should come into favour and roll coating of pretreatment should predominate. The capacity limiting surface texturing pass will either be eliminated or moved to the finishing line or a dedicated mill. The key to making aluminum both embedded carbon and cost competitive with steel for more and more affordable classes of vehicles lies in recycling of both prompt scrap and, in the longer term, end of life vehicle scrap. For the first time scrap separation technology is available that can compete effectively with hand sorting and can sort aluminum shredded vehicle scrap into wrought and cast alloys and then into individual alloy groups. The challenge is to use more end of life scrap in alloy formulation whilst at the same time extending the property range in terms of both strength and formability.

Jan 1, 2015

By Silas C. Nichols, Jennifer E. Nicks

"Limit states design (LSD), or load and resistance factor design (LRFD), is a method to account for the uncertainty in loads and resistance through a reliability calibration that requires all applicable limit states (strength, service and extreme) to be checked during foundation design. LRFD has been in use internationally for several decades; however it wasn’t until recently that engineers working on highway projects were required to use the method for the design of highway bridges and other appurtenances. Although the bridge community has been using a form of limit states design for structural components since the early 1970s, the design of foundations for bridges, walls and other geotechnical features had long been performed using allowable stress design (ASD), whereby all uncertainty in loads and material resistance is combined in a single factor of safety. While the move to LRFD was viewed as a more rational approach for the design of bridges and structures, the transition to its use for geotechnical engineering has been met by many with confusion and difficulties in application. This article will revisit the history of transition from ASD to LRFD for geotechnical engineering, summarize the status of the transition and issues with its use, and briefly discuss some emerging research opportunities for improving and advancing the design platform.Background and HistoryUntil about a decade ago, foundations and substructures for bridges were traditionally designed using ASD, while the superstructure was designed using load factor design (LFD), a precursor to LRFD that incorporated factored design loads but no risk assessment. This combination led to uncertain and incompatible safety margins in design for the various bridge components. In 1986, the American Association of State Highway Transportation Officials (AASHTO) Subcommittee on Bridges and Structures (SCOBS) concluded that the standard bridge specifications in use at the time for U.S. transportation projects had significant inconsistencies and gaps, wasn’t up to date with emerging technology and that the development of new specifications was warranted. The proposed solution by the subcommittee was to transition to a more coherent method of design where applicable failure and serviceability conditions could be evaluated considering the uncertainties associated with loads and resistance."

Jan 1, 2015