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By A. Atrafi, L. Barroilhet

The top size of particles in the flotation of potash ores, which can be as large as 4 mm, exceeds by far the top size in other flotation plants. It is then understandable that while long chain amines are used in the flotation of fine fractions (below 0.8 mm) of potash ores the coarse particle flotation also requires an extender oil. While new and very promising fluidized-bed flotation machines (e.g. HydroFloat) constitute a significant development in the flotation of coarse particles, in the area of extender oils, as reviewed in 2007 by Strathdee, Gotts and McEachern, there have been no new developments to replace the industry standard asphaltene-based carcinogenic extenders. This situation first of all results from the experimental problems that arise when water-soluble minerals like sylvite are to be tested in saturated brine. Both oils and longchain amines are water/brine insoluble. The oil with the amine dissolved in it can however be emulsified and then used as an extender oil. Such oil droplets must wet KCl particles and the emulsion must be stable to avoid handling problems. In this paper we test the use of the phase inversion technique as a method of studying wettability of KCl particles by the oil in saturated brine, and the effect of amine dissolved in this oil on the wettability. The results show that this relatively simple technique can be used to characterize the wettability of fine KCl particles by the tested oil and to determine the effect of added amine on it, and so it can be useful in selecting proper extender oils.

Jan 1, 2016

By Ewan Selers, Gary Cavanough

Drilling automation technology is well advanced and automated drill rigs are in use at a number of operating mines. This is not the case for the other drill and blast processes due to significant technical challenges to overcome. These challenges, with regard to the current “on bench” practices, include placing the initiators, loading the explosive and connecting up the initiation system. Although difficult, these challenges will be solved with engineering advances.

Jan 1, 2016

By Richard Giffen, Michael Trabold, Pablo Lemus

"As part of the new 2nd Ave Subway Project, an existing tunnel constructed in the 1970’s will be connected to the new subway and used as new running tunnels. The existing tunnel had to be modified to comply with newer structural and fire life safety codes and to be connected to the new cut and cover station at 96th St. This paper will discuss the complexities of tying an existing tunnel constructed over 40 years ago into the new station and allowing for movements due to the unloading of the existing tunnel and the differential settlement of the two structures during both the construction and permanent condition. Topics that will be discussed include structural analysis, ground improvement techniques, selection of support of excavation walls, working in contaminated soil and instrumentation and monitoring of the structures. It will also cover retrofitting the tunnel to comply with updated Fire/Life/Safety requirements. PROJECT OVERVIEW The Second Avenue Subway (SAS) will be the first major expansion of New York’s subway system in over 50 years. To be constructed in four phases, it will run from 125th St. in Harlem to Hanover Square in the Financial District (see Figure 1). For most of its length, the alignment is directly under the Second Avenue roadway."

Jan 1, 2016

By Nobuharu Isago, Atsushi Kusaka, Kosuke Kawata, Dohta Awaji

"The immediate ring closure method, in which the entire periphery of the excavation area is closed immediately with an initial support within a short distance from the excavation face, has been increasingly used in Japan, especially, as one of the most effective countermeasures against difficult ground conditions in conventional tunneling. For reasonable design of this method, the performance requirements for the initial support should be clearly stated. The analysis of construction data of 30 road tunnels and the three-dimensional numerical modeling based on real data suggest that the immediate ring closure stabilizes the tunnel structure and the ground around it because of the inner pressure effect of the initial support, especially, for low ground competence factor and small internal friction angle. Finally, the bending compressive strength and the cross-sectional geometry of the initial support have to be considered in the tunnel design while considering the earth pressure and ground properties. INTRODUCTION Conventional tunneling methods often deal with difficult ground conditions such as soft ground or squeezing ground conditions. The immediate ring closure method, in which the entire periphery of the excavation area is immediately supported within a short distance from the excavation face (Figure 1), has been increasingly used in Japan as one of the most effective countermeasures against difficult ground conditions in conventional tunneling (e.g. Takahashi et al., 2011; Nakaoka et al., 2013). The immediate ring closure method was empirically identified as effective for reducing ground surface subsidence and tunnel deformation. However, the working effects of the method have not been clarified sufficiently. To improve the design of this method, the working effects of this method and the performance requirements for the initial support need to be clarified. The relation between the effect of immediate ring closure and earth cover has been clarified (Mashimo et al., 2008; Awaji et al., 2013),"

Jan 1, 2016

By Bruce Hebblewhite, Jim Galvin

"A coal burst occurred on 15 April, 2014 at the Austar Coal Mine, located west of Newcastle, NSW, Australia. The burst resulted in fatal injuries to two men working as part of the mining crew at the development face. At the time, a continuous miner was being used to mine a longwall development gate road through heavily structured coal, at a depth of approximately 550m. A number of pre-cursor bumps had occurred on previous shifts, emanating from the coal ribs of the roadway, in proximity to the coal face.This paper reviews the geological, geotechnical and mining conditions and circumstances leading up to the coal burst event; and presents and discusses the available evidence and possible interpretations relating to the geomechanical behaviour mechanisms that may have been critical factors in this incident. The paper also discusses some key technical and operational considerations of ground support systems and mining practices and strategies needed for operating in such conditions in the future.INTRODUCTIONAustar Coal Mine is an underground longwall coal mine located near Cessnock in the Hunter Valley of New South Wales (NSW), Australia and is the only underground mine still extracting the Greta Seam in this region. The mine was the first in Australia to adopt the Chinese-developed Longwall Top Coal Caving (LTCC) method for thick seam extraction. Typically seam thickness ranges from 4m to 7m and depth of mining from 480m to 560m, with future mining planned down to depths of up to 700m, making it one of the deepest operating coal mines in Australia.On 15 April 2014, a pressure burst occurred in the left hand rib at the active mining face of B Heading, 2 to 3 cut-through, Maingate A9 panel, during development of the gateroads for the ninth longwall top coal caving panel. Strata in the general vicinity was affected by disturbed geology and multiple geological structures. Figure 1 shows a section of the mine plan as at October 2014 (six months after the accident), indicating the current longwall extraction panel (AS) and the development panel A9 where the accident occurred. (Note: Neither development nor longwall face positions changed significantly between the time of the accident and the date of this plan). At the time of the accident the current longwall face was in excess of 1,000m away from the Maingate A9 development panel face position."

Jan 1, 2016

By Shawna Von Stockhausen, Hong Yang, Tung T. Vu, Derek Penrice, Kevin Huynh

"The Regional Connector Transit Corridor is a 1.9 mile long light rail transit project in downtown Los Angeles, California. The project includes approximately 4,930 feet of twin bored tunnels together with a mined crossover cavern, 3 deep stations, and other cut-and-cover structures. The bored tunnels will be excavated using an earth pressure balance tunnel boring machine through Fernando Formation (extremely weak to weak rock) and alluvium. The tunneling will be performed in close proximity to a large number of existing structures, including the existing Metro Red Line tunnels with as little as 6 feet of separation. Thus, the evaluations of the tunneling effect on these structures and the instrumentation and monitoring program is an essential part of the project design. This paper provides a very brief overview of the considerations and evaluations of the tunneling effects on the existing structures and results of evaluation obtained during the final design stage of the project. INTRODUCTION The proposed Regional Connector Transit Corridor (RCTC) project provides a 1.9 mile-long connection between the Metro Gold Line from Pasadena and East Los Angeles; and the Metro Blue Line to Long Beach and the Expo Line to Culver City. The alignment is shown in Figure 1. The Regional Connector will provide new tracks through downtown Los Angeles. The project will extend underground from the Metro Blue, Expo, Red, and Purple Lines’ 7th Street/Metro Center Station following Flower Street, curving northeast to the north of 3rd Street under the 2nd Street Tunnel. The alignment will then continue eastward under 2nd Street, turning northeast to cross under the intersection of 1st and Alameda Streets, then splitting into two branches above the ground surface, one branch extending north along Alameda Street and the other extending east along 1st Street. The project elements include 3 deep stations, a SEM cavern, segments of TBM bored tunnels, and cut-and-cover guideway structures. The bored tunnels have an excavated diameter of 20.3 feet. The subsurface conditions along the tunnel alignment generally consist of artificial fill overlaying finer-grained alluvium (dominantly medium dense to dense sandy soils), underlain by coarser-grained alluvium (a wide variety of medium dense to dense sandy and gravely soils). Below the coarser-grained alluvium is Fernando Formation, which is characterized as extremely weak to very weak sedimentary bedrock. A long stretch of the alignment will be excavated in this formation. The soil layers above the Fernando Formation are of variable thickness and spatial distribution. The geologic profile is shown in Figure 2."

Jan 1, 2016

By J. Kolacz

"A new sensor based sorting system has been developed, providing a possibility for laboratory scale testing and further scale-up of the separation results to the industrial operation. The new system contains different sensors as: X-ray detectors, visible light cameras, NIR cameras, ultraviolet cameras and magnetic sensors, in the same sorting unit. The sorting unit allows advanced calibration options and fine-tuning of the installed sensors to achieve the best separation effect under controlled conditions. Finally, the processed material can be analysed and separated by the rejection mechanism, similarly to the industrial scale operation. At the same time, the process is carried out with limited amount of material allowing detailed statistical calculations for processed particles and all sensor types. The optimal settings and sensor types are specified for the industrial application.The paper describes the scale up of the results achieved for iron ore and coal, where the test work was first carried out using the new laboratory sorting system and where the industrial scale sorting system has been built, in the final stage. The industrial scale sorting results showed a very good correlation between the laboratory and full scale operation. Thanks to the detailed study carried out in the laboratory equipment, the settings of the sensors in the full scale operation provided much better separation efficiency. It was especially important to provide proper setting for the X-ray sensor data calculations, which can be very critical for achieving the best results. During the industrial scale sorting of coal, the input material had 40-55% rock particles as the direct source of ash in the coal stream. The optimal laboratory unit settings and transferring these settings to the industrial sorter, provided 98.8% efficiency for removing rock particles with only few % losses of coal."

Jan 1, 2016

By G. Wang, L. R. Moore, Y. Xiong, A. Gorken

"Feldspar may represent 60% of the earth’s crust, but the mineral does not exist in a pure state. It is generally associated with quartz, iron containing minerals such as mica, and titanium containing minerals such as rutile. Feldspar itself can even exist in different lattices from those containing sodium to various divalent ions. As such, its beneficiation has become a process that is quite complicated, when compared to the beneficiation of other minerals. It is this complexity that has made feldspar beneficiation dependent on tailor made reagents to successfully yield the industry specified feldspar products. This paper reviews the mineralogical variations found from two feldspar mines and the development of collectors to specifically target a Fe+Ti concentration of < 0.05%, while maintaining a feldspar recovery greater than 90%.INTRODUCTION Feldspar is a class of aluminum silicates that represents the most abundant mineral on earth (Vidyadhar, 2002). This class of mineral can further be defined by the types or concentrations of cations present in the crystal lattice, MAlSi3O8 (M = K, orthoclase and microcline; M = Na, Albite; M = Ca, Anorthite) (Heyes, 2012). Feldspar is most commonly mined and processed for either the alumina used in glass making or for the alkalis used in ceramics. The alumina is known to improve product hardness, durability, and resistance to chemical corrosion. The alkalis act as flux, which means they not only lower the melting temperature of the mineral mixture, but also assist in connecting the other components present in ceramics. It was stated in 2009 that the world production of feldspar was in excess of 18.3 million tons produced, with the majority coming from China, Italy, and Turkey. Raw feldspar is typically found with quartz, iron containing minerals such as mica, titanium containing minerals such as rutile, and other feldspar minerals (Celik, 2001). Quartz is stated as having a negative effect on the melting point of the feldspar, whilst the iron and titanium based mineral contaminants are known to have negative effects on color and quality of the product produced; these mineral contaminants must therefore be separated prior to application (Barns, 1997 & Celik, 2001). Mineral flotation and magnetic separation are the most common means of feldspar beneficiation. However, conditions vary greatly from mineral contaminant to mineral contaminant (Table 1). Some literature suggests feldspar can be floated with an amine, but this generally yields lower than acceptable recoveries and often still requires the magnetic separation of iron based minerals to achieve the desired grade (Amarante, 1997 & Heyes, 2012). Feldspar flotation can be further improved with the addition of hydrofluoric acid (HF) as a silica depressant and feldspar surface modifier, but this still requires the removal of some of the other minerals first. Rutile can be floated with an anionic fatty acid collector at a pH range of 7-8 or with a petroleum sulfonate at a pH < 4 (Celik, 2001), while mica can be floated with a petroleum sulfonate or an amine collector at a pH of 3.5."

Jan 1, 2016

By E. Siami-Irdemoosa, S. R. Dindarloo

"Discrete event simulation is a stochastic mathematical modeling tool with applications in queuing systems. Many mining operations, both surface and underground, can be simulated in the context of queuing theory , for example open pit loading and haulage operation, underground level and vertical transportation, and mineral processing circuits. A computer simulation model of the operation is an invaluable tool to study both the system’s dynamics and conducting sensitivity analysis on different effective elements on system performance. In this paper, merits of discrete event simulation in decision making in mining engineering is discussed. Moreover, a stochastic simulation framework for selection and sizing of shovels and dump trucks in surface mining is presented to elaborate one example for applicability of the method in mining operations. INTRODUCTION Mathematical modeling is a valuable tool in design, optimization, and decision making in both surface and underground mining operations. Several researchers have tried to study different aspects of mining operations using a wide range of mathematical techniques such as linear programming[1], analytical hierarchy process [2], non-linear programming[3], genetic algorithms[4-5] ,mixed integer programming [6], machine repair model[7], queuing theory [8], and conventional spreadsheet calculations based on experience and engineering judgments. There are different uncertainties in typical mining operations (e.g. material loading and haulage, drilling, and blasting). For example, in a truck-shovel operation, different governing activities such as loading, haulage, and dumping cycles are stochastic variables. Moreover, analytical modeling of a large truck-shovel operation is very complicated. Thus, application of analytical and/or deterministic techniques cannot guarantee a solution for different problems that are encountered in daily mining operations. Discrete-event system simulation (DES) is a modeling method for such time discrete and probabilistic phenomena [9]. DES has been employed by different researchers in mining engineering through available software and languages such as GPSS, SIMAN- ARENA, and SLAM [10-14]. Most of the studies so far, tried to evaluate some “what-if” scenarios, to understand the possible effects of changing different input variables on overall mine economics. For instance, Baffi and Ataeepur (1996) used Arena to simulate a truck-shovel operation [10]. Also, Sturgul has conducted extensive studies in the application of DES in the mining engineering field [15- 17]. A very good background review of application of this technique in the industry can be found in [15-16]. Previous studies have shown that, different approaches including deterministic, stochastic, and experimental methodologies result in considerable differences in outputs [18]. These techniques lead to different solutions, regardless of the quality of technique/software itself or knowledge of the modeling team. Hence, the first step is to develop a comprehensive simulation framework to obtain nearly the same optimal results for the same input variables, regardless of the employed technique."

Jan 1, 2016

By R. Esteban, D. Runnels, S. Girgin, J. Torrealba-Vargas

"Each mineral processing project requires early testwork to evaluate the economic potential of a deposit. The testwork needs to be efficient and it should provide enough information to obtain key parameters, first for a high level flowsheet selection at the conceptual and PEA stages and then, for later stages, to confirm the flowsheet selection and optimize the metallurgical efficiency of the plant. The testwork should consider all rock types or lithologies present, and carry out testwork for the purpose of sizing the major processing equipment.A successful project requires that the project stakeholders develop an efficient sample collection program to produce enough material for a scoping and pre-feasibility level program. This involves the participation of a team of geologists, mining and metallurgical engineers in the project, as early as possible, to define the deposit characteristics that need to be validated.The project schedule requires a close control of the testwork scope, procedures, and timing, but also the efficient analysis of results to provide indications of red flags that could impact circuit design as early as possible.In some cases, projects are put on hold due to fluctuations of the world economy until the return of more favorable conditions. In that scenario, prior data analysis of former testwork results could reduce significantly the amount of testwork required to restart a project. The paper will also present examples where the analysis of former testwork data was used to reduce the amount of new testwork in addition to presenting examples of latest projects where the above-mentioned test program approach was followed."

Jan 1, 2016

By P. Zhang, S. Al-Thyabat

"Phosphate rock contains traces of rare earth elements (REEs) and can be a secondary source of these critical materials as large tonnages of phosphate rock are mined annually. Attention has mostly focused on the extraction of REEs from phosphogypsum, which contains more than 70 percent of the REEs reporting to phosphate concentrate, with only limited work conducted on REE extraction from sand tailings and slime even though they account for 16 percent and 15 percent, respectively, of REEs mined with phosphate matrix.In this work, phosphate flotation tailings were upgraded by gravity separation and froth flotation. Gravity separation was conducted using a laboratory shaking table, while flotation was conducted in a Denver D-12 flotation cell. The concentrated tailings were then leached by nitric acid followed by REE extraction with solvent and ion-exchange resin.The sand tailings were assayed as having 2.6 percent phosphate (P2O5 ) and 198.1 µg/g REEs. It was found that the shaking table could produce tailing concentrate assayed as having 8.6 percent P2O5 and 616 µg/g REEs but with only 20 percent REE recovery, while the froth flotation produced froth concentrate assayed as having 8.1 percent P2O5 and 368.2 µg/g REEs with 63.5 percent REE recovery. Leaching the flotation concentrate with 5.2 M (25 percent) nitric acid followed by extraction with solvent and ion-exchange resin yielded precipitates with REE contents of 0.926 and 0.314 percent, respectively, compared with 0.716 and 0.213 percent when table concentrate was used.IntroductionRare earth elements (REEs) consist of a group of 17 elements: the 15 lanthanides along with yttrium (Y) and scandium (Sc). They are rare not because of their scarcity in the Earth’s crust but because they are rarely found in economic and mineable deposits. REEs are called “seeds of technology” because of their importance to some critical technological industries such as renewable energy, hybrid cars, electronics and batteries. On average, an electric car or a hybrid car contains about 10 kg of REEs (Grasso, 2012; Radhika et al., 2011).REEs are usually categorized into light (LREE) and heavy (HREE). LREEs consist of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pr), samarium (Sm), europium (Eu), gadolinium (Gd) and scandium (Sc), while HREEs consist of terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and yttrium (Y). About 200 minerals contain traces of REEs, but only three are considered economically significant: bastnasite, with the formula La,Ce(CO3)F; monazite, with the formula(Ce,La,Nd,Th)PO4; and xenotime, with the formulaYPO4 (Jordens, Cheng and Waters, 2013)."

Jan 1, 2016

By N. Pajunen, R. Mäkikoskela

"The current state of environment has been achieved by acting linearly. At the same time, we know that transition towards circular economy cannot be made the same way that we have used to, trusting only a market economy and economic growth. Environmental improvements have been promoted, some progress has been made, but major steps towards sustainability have not been taken. Industry is now facing significant change, from process related environmental thinking to product-based environmental thinking.Engineers make decisions which have lifelong influence and even longer on environment and society. Material engineers in case of saving natural resources and increasing material cycle, have an important role to play in the transition towards sustainability. Best knowledge of minerals and materials is in the material development phase. If we want to increase the cycle of different materials, it is vital to make decisions towards circular economy in early phase of product´s life cycle.The target of this study is to promote circular economy; to increase material efficiency; to save natural resources; and to extend product lifecycles in process industry via product design and material development. In this study we have a new kind of cooperation. We combine two disciplines, engineering science and fine arts. We promote sustainability via breaking out the silos. We bring the cyclic artistic thinking into engineering science and environmental research. The new research combination makes the existing information visible in a new way, and it will change attitudes and ways to act by means other than traditional linear rationality.We have tested the new working method via the industrial case study with the chosen product: the sandwich panel of construction industry. The target of the study was to create something new from the chosen product with artistic thinking. The working method will be presented in this paper."

Jan 1, 2016

By R. Cooper, K. De Wet, A. Janwong

"Horsehead Metal Products is a zinc refinery in Mooresboro NC treating crude Waelz Oxide (WOX) to produce Special High Grade Zinc by a hydrometallurgical process, comprising leaching, zinc solvent extraction/electrowinning (SX/EW), melting and casting and bleed treatment. Cadmium removal by zinc dust cementation plays an essential role in the bleed treatment circuit to prevent a build-up of cadmium in the circuit. Silica, although not present at significant levels in the WOX feed material (approximately 0.3%), had a significant impact on the efficiency of cadmium cementation with zinc dust, most likely due to the passivation of zinc dust particles with silica gel. Solid/liquid separation efficiency by filter press was also impacted. The silica levels were mapped throughout the circuit in an attempt to identify the source of the silica issues. Adjustments including using PLS as feed to cementation, pH control in WOX leaching and neutralization have been introduced to mitigate the issues created by silica gel in the circuit. INTRODUCTION Located in North Carolina, Horsehead Metal Products Inc. is a hydrometallurgical zinc refinery processing Waelz Oxide (WOX) to produce Special High Grade (SHG) zinc. The flowsheet, known as the Modified Zincex® process, consists of leaching, solvent extraction, electrowinning, melting and casting and bleed treatment as illustrated in Figure 1. Cadmium cementation, part of the bleed treatment process, provides an essential bleed of cadmium from the circuit, as metallic cement. The Cadmium cementation circuit consists of agitated cementation reactors, a zinc dust addition system, filter presses, agitated purification (releach) reactors and a cadmium concentrate filter press Silica can be found in several forms in acid leaching. The first form is fine silicate particles. The size of the particles can vary from one to twenty microns (1). Fine silicate particles can lead to the formation of crud in solvent extraction circuits (2, 3). At Mooresboro, crud has been observed in Depletion, which is part of the solvent extraction circuit. Silica content in the solution in this section is high. The second form of silica is monosilicic acid Si(OH)4, which begins to polymerize almost immediately upon being leached into solution. Monosilicic acid polymerizes to silica gel or a silica precipitate dependent primarily on supersaturation (5). Factors that influence the rate of polymerization include temperature, sulfuric acid concentration / pH, hydrofluoric acid concentration, seeding, and dissolved salts concentration such as zinc and aluminum in the solution (4, 5, 6). In sulfate systems, silica solubility is reported in the range of 150 to 450 ppm of SiO2 (3, 5, 7)."

Jan 1, 2016

"The use of gas, temperature and airflow sensors to monitor mine ventilation atmospheres offers numerous safety and operational bene-fits to mines. Detection of dangerous gases, changes to airflows and temperature variations are some of the obvious benefits of using at-mospheric sensors in mines. The prediction of atmospheric conditions between sensors however is potentially difficult, and gaining full cover-age a mine will require either many sensors or a method of extrapolat-ing and predicting atmospheric conditions between and downstream from a sparser array of sensors. A dynamic simulation computer model technique is demonstrated to predict time based changes to atmosphere conditions downstream from sensors. The dynamic model predicts the time based changes to conditions throughout a mine model by simulating the mixing, addition and dilution of gases and airflow changes in incremental time steps. The advantages of this method is that a real time overview of full mine atmospheric conditions can be viewed at all locations, even areas without sensors. In addition, with careful planning and consideration of potential contaminant sources, the number of required sensors can be minimized. INTRODUCTIONMine Ventilation Sensors The importance of continuously monitoring mine atmospheres has been recognised since mining underground began and the effects of harmful gases on human health were discovered. Through the 19th and early 20th centuries, coal miners would take canaries underground with them as an early detection system against life threatening gases such as carbon dioxide, carbon monoxide and methane (Figure 1). The canary, normally a very songful bird, would become agitated, stop singing and eventually die if not removed from these gases, signalling the miners to quickly exit the mine (Davalle, 2011)."

Jan 1, 2016

By W. Zhang

"The adsorption of collector on bornite has been studied in situ in aqueous solutions by applying an atomic force microscopy (AFM). The AFM images show that xanthate, such as potassium ethyl xanthate (KEX) and potassium amyl xanthate (PAX), adsorbs strongly on bornite mainly in the form of insoluble metal xanthate, which binds strongly with the mineral surface without being removed by flushing with ethanol alcohol. This adsorption mechanism is very similar to the one obtained with chalcocite/xanthate system. However, the result also clearly shows that the adsorption of xanthate on bornite is totally different from its adsorption on chalcopyrite, during which oily dixanthogen is the main adsorption product on chalcopyrite surface. The obtained AFM images also showed that the adsorption increases with increasing the collector’s concentration. When Cytec Aerofloat 238, a dialkyl dithiophosphate collector, is used, it adsorb on bornite mainly in the form of an oily substance, which can be rinsed off mineral surface by flushing with ethanol alcohol. AFM images also show that the adsorption of Cytec Aerofloat 238 increases with increasing the adsorption time. INTRODUCTION The adsorption of collector on mineral surface is vital for a successful flotation process to achieve a satisfying recovery. Historically, many works have been carried out to clarify the adsorption mechanism of collectors on sulfides. (Gaudin and Schuhmann, 1936, Poling and Leja, 1963; Allison et al., 1972, Fuerstenau, 1982; Leja, 1982; Woods, 1984) Compared to other copper minerals such as chalcopyrite and chalcocite, much less work has been done to study the adsorption collector on bornite. Allison et al. (1972) studied the reaction products of various sulfide minerals with xanthate solutions and reported that the measured rest potential of bornite in 6.25×10-4 M KEX solution at pH 7 was +60 mV and the reaction product of PAX on bornite was cuprous alkyl xanthate. Mielczarski and Suoninen (1984a, 1984b) applied the XPS and studied the adsorption of potassium ethyl xanthate on cuprous sulfide. It was reported that there was a relatively rapid formation of a well-oriented monolayer of xanthate ions followed by a slow growth of disordered cuprous xanthate molecules on top of this layer. Buckley et al. (1984) investigated the surface oxidation of bornite by linear potential sweep voltammetry and X-ray Photoelectron Spectroscopy and proposed the adsorption products on bornite depended on the solution potential. Zachwieja et al. (1987) studied the electrochemical flotation of the bornite-ethylxanthate system and reported that KEX reacted with bornite through an electrochemical oxidation reaction forming cuprous xanthate between -0.4 and -0.2v (SCE). Hangone et al. (2005) studied the flotation of a bornite-rich copper sulfide ore using thio collectors and their mixtures and reported that the highest copper recoveries were obtained with the diethyl dithiophosphate (di C2-DTP)."

Jan 1, 2016

By Henning Schwarz, Ade Ogunsola, Anas Almousa

"The Riyadh Metro, commissioned by Arriyadh Development Authority “ADA” - the executive arm of The High Commission for the Development of Arriyadh -, forms part of a new public transport-system of Saudi Arabia’s fast growing capital city. The Design & Build project consists of 176 km of Metro Line with 57 km of tunnels. Beyond the Design and Construction, an additional aim of the ADA is to introduce up-to-date methodologies and improve safety in construction projects. A systematic dilapidation survey of buildings and infrastructures was a prerequisite for designing the required instrumentation and monitoring tools. Site investigations required of existing methodologies and the use of geophysical methods for achieving reliable results. Large diameter TBM tunneling is challenging in hot weather conditions and karstic ground. The present paper shows how modern technologies for underground construction are introduced into the local industry and gives an outlook on future projects in the Kingdom of Saudi Arabia. INTRODUCTION Riyadh, the capital city of the Kingdom of Saudi Arabia, is a fast growing city with more than 5.7 million inhabitants. The growth of the city is linked to the recent history of the Kingdom, where some initial milestones from the 1950’s can be highlighted: Revenue generation from the exportation of oil from the Kingdom; downstream investment of oil revenue in the reconstruction and development of the Kingdom; a general plan for the settlement of the Bedouins; the provision of a public electricity network for the city; the opening of the Riyadh - Dammam railway corridor providing a link from the capital to the Eastern Region; the commissioning of Riyadh airport (converted to Riyadh airbase, after the opening of King Khalid International Airport in 1983); and the relocation of ministries and other central government agencies in 1955. In 1974, The High Commission for the Development of Arriyadh was established as the organizational, planning, executive and coordinating body responsible for the development of Riyadh. Arriyadh Development Authority “ADA”, established in 1983 is the High Commission’s executive, technical and administrative arm. The ADA is responsible for implementing the High Commission's organizational, planning, executive and coordinating decisions and missions. The ADA’s president is a member of the High Commission (ADA 2015). One of the remits of the ADA is the preparation and execution of a transport plan for the city of Riyadh."

Jan 1, 2016

By L. Cáceres, G. Leinenweber, P. Bustamante

"Given the severe scarcity of fresh water sources in Northern Chile the use of seawater has become the only alternative to allow mining expansion. This option however poses several technological challenges as a result of the high concentration of natural salts that promote various forms of metal corrosion. Therefore the steel piping protection has been a constant challenge for design engineers responsible for solving the problems of corrosion. Known protection alternatives are varied and expensive, a few of them are rubber coatings, protection based centrifuged concrete, extra wall thickness of pipes in combination with corrosion inhibitors, extra wall thickness of pipes without using corrosion inhibitors, and the use of highly corrosion resistant steel materials.In this framework the aim was to study the corrosion kinetics of carbon steel pipe API 5L X70 under electrochemical and weight loss testing. The test conditions include a range of seawater velocities between 0.2 to 3.0 m/s.For electrochemical experiments the API 5L X70 steel specimen was a 4 mm diameter disk embedded in an 8 mm diameter Teflon rod and exposed to seawater. Duplicated coupons were placed in a standard test apparatus that was built according to the standard ASTM D 2688 – 94.The main results were: a) corrosion mechanism explained in terms of the counterparts partial processes which are the hydrogen evolution and oxygen reduction reaction; b) for the test specimen a corrosion band like feature that suggest a lateral dispersion of aggressive solutions from corrosion pits; c) a range of corrosion rates between 1 and 1.96 mm/year for flow rates between 0.2 and 3.0 m/s; and d) a convenient inhibitor dose between 20–25 mg/L for optimum inhibition efficiency to obtain a maximum value of 80% for corrosion efficiency."

Jan 1, 2016

By Paul Nicholas, Raju Gottumukkala

"India’s economy is expanding with rapid urbanization. Improvement in infrastructure is a keystone to the Indian government’s economic plans, including expansion of transit systems. Most of these systems are designed with elevated and underground sections. New Delhi, a city of 23 million people, suffers from heavy traffic congestion and pollution. The transit (metro) system is seen to be of critical importance. Phase 3 of the Delhi transit system project is 140 kilometers (km), with 40 km of twin-bore tunnels requiring 35 tunnel boring machines (TBMs) for construction. Transit systems are also under design or construction in Chennai, Bangalore, Kolkata, Hyderabad, Jaipur and Mumbai. Most have twin-bore tunnels. At present, 55 TBMs are operating on underground metro construction, and future projects will increase this number. This paper highlights the unique challenges of construction of underground metro systems in highly congested urban environments, using Kolkata and Delhi systems as examples. INTRODUCTION The first transit system in India was constructed in Kolkata (India’s third-largest city by population.) This line is 28 kilometers (km) in length, has underground and at-grade sections, was built in phases, runs north/south, and has 24 stations. This project was sanctioned in 1972, started construction in 1984, and was completed in 1995. The tunnels were constructed primarily by cut and cover methods with some open-face, compressed air shield tunneling. In 2006, the urban transport policy recommended construction of transit rail systems in all urban cities with a population exceeding 2 million. Further, in 2014 the central government stated that it would assist in financing transit systems in all cities with a population of over 1 million. In 2015, the central government approved the development of transit systems in 50 additional cities across India with a budget of $75 billion (see Figure 1). Transit development is just part of a huge expansion in planned rapid transport systems, which include metro, bus, high-speed rail, and monorail systems. Metro systems will include elevated and underground sections with twin-bore tunnels and underground stations. In the Delhi/National Capital Region (NCR), now the largest city in India by population, Delhi Metro Rail Corp (DMRC) was formed in 1995 as a joint venture company between the central government and Delhi state. DMRC operates the Delhi metro system. (see the case studies described later in this paper). DMRC has developed an external function to carry out studies and to offer consultancy to other cities planning transits. Since its inception, DMRC has produced Detailed Project Reports (DPRs) for every metro and monorail project in India. In 2012, DMRC became a partner in the management consultancy for Jakarta Mass Rapid Transit System, its first project overseas. DMRC became a model organization for other cities to follow. These cities have included Chennai, Hyderabad, Kolkata, Bangalore, Jaipur, Mumbai, Ahmedabad, and Nagpur. Other cities (e.g., Lucknow and Patna) are in the metro planning phase. Metro systems are under construction or partially operating in Hyderabad, Bangalore, and Jaipur."

Jan 1, 2016

By J. Y. Liu

In Comparison to the application of HPGR (high-pressure grinding rolls) in the cement industry and in iron ore processing, the introduction of this energy-efficient comminution technology to processing of nonferrous base-metal ores has progressed slowly as yet. In the field of minerals industry, challenges lies not only in the large variety of the feed material with respect to particle size, density, hardness, moisture and mineralogy of the material but also in complexity of the processing flowsheet, which need to be addressed from case to case based on result of HPGR comminution test work. Whereas conventional comminution test with HPGR in lab-scale or pilot scale needs quite a large amount of feed material, a compressive stressing test of particle-bed in piston-die device provides an effective way to study interparticle breakage behavior of ore material with much less feed. In the present study the effects of interparticle breakage on comminution of a copper ore has been investigated by compressive stressing of particle bed in a piston-die device. The feeds to the particle-bed stressing tests were four narrow size fractions in the size range of 0.3~3.35 mm and a broad size fraction of 0/3.35 mm. The pressures applied were in the range between 30 and 180 MPa. The results showed that the specific energy consumption increases linearly with the pressure; the product fineness increases also with the pressure, but the magnitude of this increase declines as the pressure goes up. Under the same stressing intensity, the product size distribution curve becomes steeper as the particle size decreases, so there is no self-similarity between product size distributions of different feed sizes. The suitability of a material-characterization model for interparticle breakage was verified for this ore. In addition, the effect of interparticle breakage on comminution of this ore with respect to its influence on the downstream flotation were analyzed in terms of size-metal distribution and mineral liberation.

Jan 1, 2016

By Willem P. C. Duyvesteyn

"Scandium International Mining Corp (SCY) has been involved in the commercial development of its Nyngan Scandium Project for about ten years. Various studies at a variety of global R&D organizations have been carried out in an attempt to define the deportment of scandium in both the limonite as well as the saprolite phases of Nyngan ore to assist with process development. Technologies such as sulfuric acid baking, high pressure acid leaching, sulfuric and hydrochloric acid atmospheric leaching and heap leaching have been extensively investigated both at the bench and pilot scale level to arrive at the most economic process flow sheet that will be discussed in some detail in this paper. Solvent extraction, ion exchange and other refining technologies have been tested and an optimum configuration has been established for the Nyngan project which is expected to be the first primary scandium mine and metallurgical plant in the world.Because of a lack of product availability the current scandium market is limited to less than 20 tons per year. Technologies have been identified to produce product with different specifications for aluminum alloys and solid oxide fuel cell applications. Preliminary economics have identified that Nyngan will be a robust and low capital cost project that can readily be expanded as the size of the scandium market increases."

Jan 1, 2016