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By Mansoor Barati, Xue Yin, Yanhui Sun, Alex McLean, Yindong Yang

The formation and evolution of inclusions in Ti-Stabilized, 17Cr Austenitic Stainless Steel produced by the ingot casting process were investigated through systematic sampling of liquid steel and rolled products. Analysis methods included total oxygen and nitrogen contents, optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The results indicate that the composition of inclusions was strongly dependent on the types of added alloying agents. During the AOD refining process, after the addition of ferrosilicon alloy and electrolytic manganese, followed by aluminum, the composition of inclusions changed from manganese silicate-rich inclusions to Al2O3-rich inclusions. After tapping and titanium wire feeding, pure TiN particles and complex inclusions with Al2O3-MgO-TiOx cores coated with TiN were found to be the dominant inclusions when [%Ti] was 0.307 in the molten steel. These findings were confirmed by thermodynamic calculations which indicated that TiN inclusions could be formed in the liquid phase due to the high contents of [Ti] and [N] in the molten steel. From the start of casting to the rolled bar, there was no obvious change in the composition of inclusions compared to the titanium addition stage. Stringer-shaped TiN inclusions elongated along the rolling direction with lengths varying from 17 to 84µm were observed in the rolled bar, which could detrimentally impact the mechanical properties of the stainless steels.

Jan 1, 2015

By G. Minhas, M. Pule, Y. Laffitte, M. c. McGurn, T. Tzanetakis, Peacey. J., R. Susilo

Titanium (Ti) metal production from titanium tetrachloride (TiCl4) using magnesium (Mg) as a reducing agent is the well-known Kroll process. A chloride route is used to avoid oxidation of the titanium sponge. The sponge is consolidated into ingots and can then be made into powder by melting and atomizing or by hydriding/dehydriding. Attempts at direct powder production have met with difficulties, including low Ti yield and the formation of very fine particles (particles between 25-100 µm are desired). This paper discusses two methods to produce Ti powder in a molten salt medium using magnesium powder as a starting material instead of a pool of molten magnesium. The first method is a direct reduction of gaseous TiCl4 injected in the melt with the magnesium powder in suspension in the molten salt. The second method is a two stage TiCl4 reduction reaction where recycled Ti was used to form titanium dichloride (TiCl2) in the first stage followed by addition of magnesium powder into molten salt in the second stage. A correlation between Ti yield and processing variables such as TiCl4 to Mg ratio, Mg particle size, TiCl2 concentration in the melt, and reaction temperature was studied. The Ti powder formed was also analyzed for particle size distribution. Despite challenges and difficulties encountered, this paper shows some promising results which could provide guidance to others working on direct Ti powder production.

Jan 1, 2015

By X. Q. Jiang, D. L. Chen, A. Macwan

Magnesium alloy, being the lightest structural material, is a key candidate for the weight reduction of vehicles in automotive and aerospace industries; however, its poor corrosion resistance and difficulty in deformation are limiting factors. Recently, Al/Mg/Al tri-layered clad sheets have been considered as a promising alternative to improve corrosion resistance and formability of magnesium alloys. The aim of this study was to evaluate the tensile properties and deformation behavior of Al/Mg/Al tri-layer clad sheets at different temperatures and strain rates. Yield strength (YS), ultimate tensile strength (UTS), and elongation were observed to increase with increasing strain rate. With increasing temperature from -40°C to 180°C, YS and UTS decreased and ductility increased. The strain hardening exponent evaluated via three equations of Hollomon, Swift, and Afrin et al. showed a similar increase with increasing strain rate and decreasing temperature. The fractographic analysis showed partial debonding of clad interface especially at higher strain rates and lower temperatures.

Jan 1, 2015

By A. Hashempour, D. Javani

"Selection of an optimal bit is a critical issue in drilling engineering. Specific energy (SE) and Cost per Foot (CPF) are the most common methods for evaluation of bit efficiency and optimal bit selection. The major shortfall of both methods is that they do not directly account for geological and geomechanical parameters of formations being drilling. In this paper, results of using the two foregoing methods are compared using Formation Drillability (FD) method, which directly accounts for geological and geomechanical parameters of a formation. This method combines various geological and geomechanical parameters and yields a dimensionless parameter indicating the formation drilling hardness (drillability). Results of this study show that the amount of energy, cost and time spent for drilling a unit volume / length of an identical formation may vary in different wells. This is due to the fact that geological and geomechanical characteristics of a formation may vary among wells and even within short intervals of a single well. Therefore, an optimal bit may not be appropriately selected, if drilling and economical parameters are the only factors considered and the formation geological and geomechanical specifications are ignored.INTRODUCTIONMany authors such as Bilgesu, Al-Rashidi, Aminian, and Ameri (2000) and Clegg (2006) conducted research in the evaluation of bit performance and optimum bit selection. Almost all of them tried to establish a good relationship based on geomechanical parameters. Primary examples are the research done by Ubaldi (1999), Macini, Magagni, Da Dalt, and Valente (2007)."

Jan 1, 2015

By K. Lagnese, C. Robinson, S. Muddasani

"Mine water generated from underground coal mining operations contains both dissolved and particulate solids. Dissolved solids primarily consist of sodium, calcium, magnesium, potassium, chlorides and sulfates. When discharged to a receiving stream without treatment, these constituents create a potentially toxic environment for aquatic life. A case study is presented to discuss how a centralized treatment plant treats mine water from six locations to meet discharge limitations for chlorides. Located in West Virginia, this facility consistently achieves less than the NPDES permit limitation of 218 mg/L chlorides in the discharge while generating almost zero liquid waste. The dissolved solids concentration in the influent ranges between 5,000 and 10,000 mg/L, with chloride concentrations of 1,000 to 2,000 mg/L and sulfate concentrations of 2,000 to 6,000 mg/L. The mine water is treated using advanced treatment technology to produce clean water for discharge or reuse. The treatment process comprises aeration, softening, filtration, reverse osmosis, RO reject softening, evaporation, crystallization, final effluent remineralization and sludge dewatering. The solid waste generated in the treatment process is landfilled on site. The leachate is sent back to the facility’s thermal treatment process. Because no liquid waste leaves the property, this plant is termed a “Zero Liquid Waste” (ZLW) facility. INTRODUCTION The advanced water treatment system was built to meet a new 218 mg/l regulatory limitation imposed by the West Virginia Department of Environmental Protection for chlorides discharged to surface waters. The system is designed to treat a maximum flow of approximately 5 million gallons per day (795 m3/h) of mine water. The treatment process utilizes reverse osmosis (RO) membrane treatment to achieve the effluent criteria, and evaporation and crystallization technology to manage the RO concentrate from the water treatment process. As a result, the system produces clean water for discharge while generating zero liquid waste. The effluent water can be used for industrial purposes or discharged to a receiving stream. A Water Impact Index (WIIx) study indicated that discharge of this high-quality water into the Monongahela River watershed may improve the water quality for downstream water users. The waste produced in the treatment process, including softening sludge and salt, is disposed of in an on-site landfill."

Jan 1, 2015

By Q. F. Wang, M. H. Lai, T. Q. Liu, G. G. Dong

Compared with the traditional pre-treatment process, biological oxidation process has many advantages including higher gold recovery, less cost, easier operation. The bio-oxidation reactor is the most important equipment for biological oxidation process. In this paper, the characteristics of biological oxidation are investigated, and the design principles are proposed based on laboratory tests. Both increasing the tank height and taking new inflation system can enhance higher dissolved oxygen. The new type of large-scale industrial bio-oxidation reactor is designed, which is 9.5 m in diameter and 10 m in height. The bio-oxidation reactor metallurgical performance has been tested by industrial-scale experiment. The slurry of flotation concentrate is divided into two parts to feed two bio-oxidation reactors. The feeding rates of two reactors are adjusted on the basis of getting the same content of S, Fe, As in overflow. The result shows that the feeding rate of the new type of 700 m3 bio-oxidation reactor is 3.72 m3 per hour, and the feed rate of the conventional 700 m3 bio-oxidation reactor was 3.23 m3 per hour. The processing capacity of the former is 15.2% higher than that of the later, which demonstrates the new type of bio-oxidation reactor has higher oxidation rate.

Jan 1, 2015

By G. O. Oniyide, H. Yilmaz.

"This paper presents the result of the research done on the effect of temperature on the dilatancy of rocks from the Bushveld Igneous Complex (BIC), where the South African Platinum mines are located. The BIC has higher virgin rock temperature (VRT) than the gold mines of the ‘Witwatersrand Basin Complex’. If the platinum mines advance to ultra-deep levels as the gold mines, since the Merensky Reef has been reported to extend beyond 5km, then the virgin rock temperature at 5 km below surface would be approximately 140oC. Hence, there is a need for the investigation of rock behaviour at high temperatures. Five different rock types (norite, leuconorite, mottled anorthosite, pyroxenite and chromitite) were tested in a 2600 kN servo-controlled multi-purpose triaxial testing machine. The tests were done at a constant strain rate of 5 x 10-1 S-1 and a confining pressure of 10 MPa within temperature range of 20 °C (ambient temperature) to 140 °C. The results show a general strength reduction and increasing dilation angles with increasing temperatures. The results also demonstrate that dilation angle is close to the internal friction angle at lower temperatures; however, they are greater at higher temperatures.INTRODUCTIONMany challenges are faced with increasing depth of mining in underground mines. The most obvious are heat, in-situ stresses and those associated with logistics. Issues related to underground heat have mainly focused on the side effect of heat on workers' health, increasing production costs as a result of higher cost of ventilation. The effect of increasing temperature with increasing depth on the behavior of rock has not been given much consideration. Generally, gold mines in South Africa are deeper than the platinum mines but the latter have higher temperature gradient, which makes the platinum mines to be warmer at similar mining depths. Although the study of the effect temperature on the behaviour of rock can be beneficial to both gold and platinum mines, the focus of the research is limited to the platinum mines because of their higher temperature gradient. Donoghue (2004) stated that the virgin rock temperatures (VRT) and air temperatures increase with depth, due to the geothermal gradient and auto-compression, that is, compression of air by its own weight."

Jan 1, 2015

By R. Panchadhara, P. A. Gordon

"A non-local formulation of the classical continuum mechanics theory called peridynamics is used to study driven dynamic fractures in the near wellbore region. The controlled application of pressure on the inner walls of the borehole can create multiple fractures that initiate from the borehole and propagate radially outwards. The number of fractures and their final length is primarily controlled by the loading conditions and the in-situ stress state. It is the objective of this study to use a novel numerical technique called peridynamics to investigate: 1) the influence of loading conditions on the fracture pattern, and 2) the effect of in-situ stress anisotropy on fracture propagation. In peridynamics, the momentum equation from the classical theory of solid mechanics is replaced with the integro-differential momentum equation of peridynamics. As a result, discontinuities in the body, such as fractures, occur spontaneously. The material is represented by a continuum body with material points that interact non-locally with all other points within a specified distance. Fractures evolve using a damage evolution law, wherein, damage at any point is represented as the ratio of the number of broken bonds in the current configuration to the total number of bonds in the undeformed configuration.Simulations are performed on simplified test cases and the results are compared to relevant experimental and numerical studies found in the literature. It is shown that the loading rate significantly influences the number of fractures initiated from the borehole as well as their extent. Low loading rate produces fewer fractures, whereas, high loading rates produce longer and a greater number of fractures from the borehole. The numerical method successfully predicts the fracture pattern obtained from a wide range of loading conditions. Predictions also indicate that the resultant fractures are shorter when in-situ stress is applied. Numerical results show that the fracture extension is largest in the direction perpendicular to the minimum compressive stress for the range of loading rates used in this study."

Jan 1, 2015

By B. Panton, J. Carvalho, E. T. Brown

High-capacity, post-tensioned anchors have found wide-spread use in initial dam design and construction, and in the strengthening and rehabilitation of concrete dams to meet modern design and safety standards. Despite the advances that have been made in rock mechanics and rock engineering during the almost 80 years in which post-tensioned anchors have been used in dam engineering, some aspects of the rock engineering design of high-capacity rock anchors for dams have changed relatively little over the last 30 or 40 years. This applies, in particular, to the calculations usually carried out to establish the grouted embedment lengths required for deep, post-tensioned anchors. These calculations which involve a number of aleatory and epistemic uncertainties, usually make simplified assumptions about the distribution and values of rock-grout interface shear strengths, the shape of the volume of rock likely to be involved in uplift failure under the influence of a system of post-tensioned anchors, and the mechanism of that failure. The resulting designs are generally conservative. These aspects of the rock engineering design of large, post-tensioned rock anchors for dams could be improved by making greater use of modern, comprehensive, numerical analyses in conjunction with 3D models of the rock mass structure, realistic rock and rock mass properties, and the results of prototype anchor tests in the rock mass concerned.

Jan 1, 2015

By J. G. Kim, B. G. Chae, D. S. Cheon, E. S. Park

The underground structures such as high-level radioactive waste disposal thermal energy storage should be designed and constructed considering thermal-mechanical characterization because of long term and/or cyclic thermal stress. High temperature changes in these structures can extend the existing cracks and generate new cracks in surrounding rock mass. In case of long term and/or cyclic thermal stress conditions, it is possible to lose the function of structures caused by the significant cracks and fracture growth in the rock mass. In this study, the critical thermal crack temperature of the granite, limestone and thermal Kaiser effect were evaluated. Experiments were carried out with the heating speed of 1.5?/min. To avoid thermal shock and target temperatures were set at 150? and 250?. In order to verify the thermal Kaiser effect, the samples were heated by 150 ? after 2-3 repetition to 250?. The generation and growth of cracks were observed through an acoustic emission measuring system. The variation of the physical rock properties was measured before and after thermal experiments. After compared with the thermal experiments using PFC2D, numerical simulations were carried out at higher temperatures (400?). The experiments showed that the initial thermal crack temperature of granite and limestone is about 35?, 32? and the critical thermal crack temperature were about 69? , and 49? , respectively. The experiments confirmed the thermal Kaiser effect of experimented granite and limestone due to thermal cyclic loading. From the numerical analysis, the critical crack temperature showed the same tendency as the thermal experiments. The P and S wave velocity of the sample after the experiment were reduced. Therefore, when heat is applied in long-term and repetitive conditions, these cracks may affect the function and stability of the underground structure. Therefore, further studies of thermal stress effects should be performed.

Jan 1, 2015

By T. Johnson, K. Lambrych, D. Kelley

Materials for construction of equipment used in hydrometallurgical plants are selected based on a combination of their ability to perform as required in aggressive process environments as well as their cost. As a material of construction, fiber reinforced plastic (FRP) has been shown to provide equal if not improved durability relative to alternative materials such as corrosion resistant alloys at a considerably lower cost. This is particularly true in the case of equipment used in acid leaching processes for copper, cobalt, nickel and rare earth elements. The selection and extensive use of FRP over alloys in new hydromet plant construction in North and South America illustrates this advantage of FRP effectively. This paper will compare corrosion performance and cost of plant equipment fabricated with stainless steel alloys and FRP made with Epoxy Vinyl Ester thermoset resins. Real world case histories for FRP piping, storage tanks, extraction vessels, and electrowinning cells combined with laboratory based corrosion studies will be reviewed to demonstrate how FRP materials are selected for hydrometallurgical equipment.

Jan 1, 2015

By Libao Zhu, David J. Williams, Nazife Erarslan

"Statistics show that the drawbell in underground mines is usually subjected to significant damage by impact loading due to falling ore. Drawbell damage causes a large quantity of residual ore to remain on the drawbell, thus leading to a huge waste of ore resources. In this study, the Cavity Monitoring System (CMS) and Surpac software were employed to visualize the 3-D damage. Also, the Discrete Element Method (DEM) was employed to perform simulations of the falling ore to investigate the damage evolution of drawbells under repeated ore impact and obtain the dynamic damage accumulation mechanism. The reason of drawbell damage was found due to the micro-shear cracks. The numerical simulations of a drawbell damage process under repeated impact loading showed the main failure type was shear failure and this type damage was found increasing with more ore falling. INTRODUCTIONDrawbells are an important part of underground mines and play a significant role in ore recovery in terms of safety, economy and efficiency (Brunton et al., 2010; Hustrulid & Bullock, 2001; Trueman et al., 2002). In most cases, blasted ore is gravitated along the drawbell and finally arrives at the footwall of the drawpoint. However, some of the blasted oversize ore blocks clog the drawbell road and those ore pieces are called hang ups (Penswick, 1997). However, any damage on a drawbell is believed to be the reason for these hang-ups. In the literature, researchers have reported that the stability of the draw-point is influenced by the stress distribution above and near the drawbell (Butcher, 1999; Neverov & Neverov, 2013). Much research in the literature has been done on draw-points in underground mines. In fact, rockfalls cause very serious damage on a small impact area in a very short time (Volkwein et al., 2011). Hoek (2000) pointed out that the blasted ore causes progressive ravelling and even collapse of the drawpoint, thus the ore in the stope is abandoned. In this paper, the Cavity Monitoring System (CMS) was employed to obtain the damage profile of a drawbell due to the impact of rockfalls and to confirm the residual blocking ore on the damaged drawbell. Then, the drawbell damage evolution due to repeated falling ore was simulated by the Discrete Element Method (DEM)."

Jan 1, 2015

By H. Kuno, H. Kobayakawa

A borehole inclinometer with FBG optical fiber sensors has been developed to clarify very slow slope movements, and the results of its application to a real slope have been shown. The main characteristics kept in mind while developing this inclinometer are as follows. Firstly, the workability must be good so that only one cable is required for taking the measurements, because the inclinometer is composed of several FBG sensor elements constructed on an optical fiber. Secondly, the minimum interval of the distorted measurements must be close, namely, within 100 mm. Thirdly, the inclinometer must excel in thunder resistance. The measurements were executed by setting up the developed borehole inclinometer on a slope where the rate of displacement is several millimeters per year. The movement of the device was developed by comparing it with that of the results of an existing borehole inclinometer. The area of the displacement concentration, 1 m in width for 4-m sections, was confirmed by the existing borehole inclinometer. The boring core, recovered using a high-quality drilling technique, was examined. Landslide clay was not permitted at the location where the displacement had concentrated as a result of comparing the measurement results with the boring core, and the rotation of gravel by the movement of the slope’s land block was allowed. These results show the slope being caught in the stage just before a primary landslide. In addition, the feature whereby the slope behavior depends on the depth was analyzed by comparing the information on the underground displacement with precipitation and earthquake records.

Jan 1, 2015

By D. Kalumba, S. Jjuuko

"Thin Spray-on Liners resist relative small deformations (< 1 mm) between rock blocks or fragments in terms of a combination of shear, adhesive and tensile-bond strengths. Shear-bond strength addresses the ability of a thin liner to resist stresses that act parallel to the rock-liner interface. Therefore quantification of shear-bond strength is essential in the formulation of design standards and requirements for Thin Spray-on Liners. In this paper Thin Spray-on Liner support mechanisms are reviewed. In addition previous methods of Thin Spray-on Liner shear-bond testing are discussed. The paper also explains the research being carried out at the University of Cape Town to investigate the effect of different parameters on the shear-bond strength.INTRODUCTIONRock surface support is widely used to combat rockfalls and resulting injuries and fatalities in the vicinity of active faces (Potvin, 2002), where workers spend most of their time (Adams & Baker, 2002; Potvin, 2002; Lacerda, 2004). The conventional (traditional) surface support systems in underground rock support include passive methods such as mesh and lacing and active methods such as shotcrete. However, rockfall sources between 1990 and 2000 in Nevada gold mines showed a steady increase in rockfall injury associated with mesh support as shown in Figure 1 (Lacerda, 2004). The conventional methods also negatively impact the mining operations with regards to costs, logistics and mining cycle times due to large material volumes (Tannant, 2001; Ozturk & Tannant, 2010; Ferreira, 2012). Therefore, these systems need to be substituted, with enhanced methods, in order to realize the business target of the mining industry of providing the planned return on investment made without harm and within budget."

Jan 1, 2015

By Hidekatsu Takeuchi, Masaru Sakakibara, Shigeo Tanabe, Kenji Harada, Akihiko Suzuki, Shoji Morihana

"Deep mixing (DM) method, one of the most commonly used solidification methods, is based on the principle of solidifying soft ground. It can be classified into two categories such as Cement Deep Mixing (CDM) method and Dry Jet Mixing (DJM) method which apply hardening agent in slurry condition and in powdery condition respectively. In recent years, DM methods have undergone changes that have evolved them from the traditional method to meet the needs of the diversifying market. Among them, the Contrivance-Innovation Clay Mixing Consolidation (CI-CMC) method is a DM method which mixes a cement-type hardening agent in slurry condition mechanically with soils in situ and incorporates the innovative technique, “atomized ejection” that has been developed to allow faster installation of larger diameter columns without sacrificing quality compared with conventional methods. At this technique, the atomized hardening agent is discharged together with compressed air through a device incorporated into the mixing blade. It also has advantages of performing the works with low-displacement of the surrounding soils in consideration of environmental friendliness and with higher penetration capability against hard ground.This paper presents the technological outline of the above-mentioned CI-CMC method, focusing on the atomized-ejection technique, followed by some construction examples, applied to the self-earth-retaining wall, to the hard ground and the area adjacent to the existing structures.INTRODUCTIONAccording to the accumulation of its case histories, Deep Mixing method has been receiving the demands of its application to more challenging conditions, such as harder ground condition, and requirement of lower displacement of the surrounding ground during its operation. In addition, to match its price against the other cheaper methods and widely receive its benefit of higher quality, the cost reduction of Deep Mixing is also one of the major challenges. For the cost reduction, higher productivity and lower consumption of the material to obtain the equivalent strength and homogeneity with the conventional method are required.The Contrivance-Innovation Clay Mixing Consolidation (CI-CMC) method has been developed to meet these demands. CI-CMC incorporates the mist ejection that has been developed to achieve faster installation of larger diameter columns without sacrificing quality compared with the existing methods. Normally, we obtain cement columns of about 1.0 m in diameter by using Deep Mixing method. To increase the productivity, it is not preferable to drastically increase the penetration and withdrawal speed of the mixing blades because of the hardness of the ground and restriction by minimum number of passage of rotating blades per a certain height of the soil cement. Instead, the expansion of diameter of the columns will simply increase the productivity. The development of the new mist ejection system, as shown in Photo 1, has enabled the diameter of soil cement columns to 2.0 m on single axis while 1.6 m on double axes. Mist ejection means that the hardening agent slurry is sprayed into the ground in mist form together with compressed air thereby achieving homogeneous mixing and reducing the resistance on rotating blades."

Jan 1, 2015

By D. Settles, R. Rose, P. L. Dunn

"A new mineral sands operation is being developed in Georgia by Southern Ionics, Inc. (SII). Prevailing mineralogy and certain design constraints required detailed testing and circuit analysis to create a robust separation processes. The floating wet concentrator plant (WCP) and mineral separation plant (MSP) flow sheets were designed based on historical testing information and recent SII test campaigns on various composite feed samples. The flow sheets were finalized through rigorous process and orebody sequence modeling.The process uses traditional physical separation equipment; however a new MT spiral, the MG12, was selected for use on board the WCP for roughing duty. The MG12 spiral is a two-stage, twelve-turn spiral that has been proven to achieve very high recoveries of heavy minerals. The floating plant includes feed desliming operations, a central MT surge bin for optimum spiral circuit feed control and ancillary operations for concentrate and tailings handling. Scrubbed heavy mineral concentrate (HMC) is then transported to the MSP for concentration of the titanium and zirconium bearing mineral fractions.The testing, flowsheet development, and plant design will be described and explained, and a brief summary of the current project status will be given.IntroductionSouthern Ionics Inc. (SII) is a privately held chemical manufacturing company, founded in 1980 by Milton Sundbeck. SII focuses primarily on the sale of specialty and intermediate inorganic chemicals. Core markets include cement and refinery catalysts, molecular sieves, zeolites, pulp and paper, pharmaceuticals, TiO2 and water treatment. SII is built on the four cornerstones of service, quality, technology and delivery with all SII facilities ISO certified and key products used in potable water treatment certified to NSF standards. SII owns and operates its own transportation fleet and is focused on being a low cost producer, committed to safety and the environment."

Jan 1, 2015

By T. Rockley, B. Goertz, S. McDaniel, J. Brune, K. Bakhsh

"Researchers at the Colorado School of Mines, under a project funded by the Alpha Foundation, have developed a working prototype of a dust sample collection device designed to determine if sufficient rock dust has been placed in an underground coal mine to prevent coal dust explosions. When used in conjunction with the Coal Dust Explosibility Meter (CDEM), the device will provide near instantaneous results on the quality of rock dusting at the tested location. The sampling device applies a pulse of air to a testing surface and collect a representative sample of mine dust based on the pneumatic entrainment process during a mine explosion. The use of both physical testing and Computational Fluid Dynamics (CFD) modeling has allowed researchers to refine the design to accurately represent the particle entrainment and optimize the sample size collected for the CDEM. The prototype is being tested in a mine environment to produce information of usability and practical aspects of mine dust sampling. This paper is a progress report summarizing the current status of sampler development. Researchers expect to have a fully developed and tested sampler in early 2016. INTRODUCTION Underground coal mines face the danger of methane and coal dust explosions. The disaster at Upper Big Branch mine (2010) has demonstrated the impact of a violent coal dust explosion that fatally injured 29 miners. Reviewing the history of coal dust explosions, researchers found that that mine operators and mine inspectors do not have a reliable method of collecting dust samples to assure that sufficient amounts of rock dust have been places to inertize the coal dust. This is a problem specifically with small mines that do not have dedicated safety departments to track rock dusting work. The aim of this research is to develop a simple, portable device that can help underground mine examiners collect dust samples from workings and test the explosibility of the sample near instantaneously. Researchers determined that the current brush-and-pan sampling method required by MSHA (MSHA 2013) is flawed in several aspects: Mechanical sampling with a brush exerts forces on the mine dust that may differ significantly from those present during an explosion. Also, U.S Bureau of Mines research (Nagy 1965) has determined that only the top 0.125 inches of the mine dust layer will be entrained in a coal dust explosion. Using a handheld pan and brush, it is difficult to correctly and repeatably sample a layer of this exact thickness. The following will describe the CFD modeling and experimental testing for the development of the prototype sampler. Researchers analyze the accuracy and performance of the prototype during the course of the build process."

Jan 1, 2015

By A. Mosqueda Martinez, L. C. Trytten, R. P. Kofluk, J. J. Budac

The Corefco ammonia leach nickel refinery treats Ni-Co mixed sulphides from the high-pressure acid leaching of Moa Bay nickel laterite. Due to the low iron content of the feed, the ammonia leach process generates a leach residue with ~10% Ni+Co. Since commissioning a leach residue pressure filtration circuit in 2002, this residue has been stockpiled, dried, and sold commercially. For several years, the residue was sold to nickel smelters overseas. In 2014, re-processing of the residue in the high-pressure acid leach was tested. Lab test work was completed showing excellent extraction of the contained nickel and cobalt, and additional beneficial effects in the high-pressure acid leach circuit. A plant test in Moa confirmed the results, and preparation for shipment of the valuable leach residue for re-processing has begun. This paper outlines the test work and results, and some commercial considerations.

Jan 1, 2015

By Zhan-fang Cao, Hong Zhong, Li-feng Li, Shuai Wang, Xiao-yu Cao, Guang-yi Liu, Ming-ming Wang

"In recent years, there has been an increasing focus on the hydrometallurgical processing of molybdenite, with the decline of high-grade and easily handled molybdenum minerals. In this work, a novel method of selective extraction of complex molybdenite concentrate, which is characteristic of high-grade copper ore, has been investigated. The results show that the leaching of chalcopyrite was impacted by the pH of the electrolyte when sodium carbonate and ammonium acid carbonate were added to the electrolyte. The leaching rate of molybdenum reached 99.39%, but chalcopyrite could not be leached at all in 240 min under experimental conditions of liquid-to-solid ratio 25:1, concentration of NaCl 4 mol/L, pH=9, room temperature and agitation speed 400 rpm. The grade of copper in the residue was 21.84%, with a recovery 99.93%. The technology of selective electro-oxidation leaching of molybdenum and recovery of copper from complex molybdenite concentrate is an effective separation method. The diffusion control model can be used to describe the process of leaching of molybdenum. The activation energy of the leaching reaction was found to be approximately 9.21 kJ/mol.IntroductionWorldwide, high-grade and easy-to-handle ore is decreasing, while the proportion of low-grade and complex ore is increasing. Porphyry copper ores with associated low-grade molybdenite are very abundant in China. Molybdenum is a valuable byproduct in the processing of porphyry copper deposits where the molybdenum is present in low quantities in the form of molybdenite (MoS2). In the conventional processing of copper sulfide ores by froth flotation, most of the molybdenite in the ore floats along with the copper sulfides. In this way, a bulk copper-molybdenum concentrate is produced. Afterward, the bulk coppermolybdenum concentrate is treated by differential flotation to obtain a rougher molybdenum concentrate, which requires several successive cleaning steps to produce a final molybdenum concentrate. However, it is widely recognized that flotation alone cannot economically produce a high-grade molybdenite concentrate, i.e., with less than 0.5% Cu. Therefore, in most cases, it is necessary to use a final step of chemical purification of the molybdenite concentrate to reduce the copper content to a level suitable for the market (Antonijevic and Pacovic,1992; Gerhardt et al., 2001; Fu and Zhong, 2003; Reza et al., 2006, Rafael et al., 2013)."

Jan 1, 2015

By Eurípides do Amaral Vargas Jr., J. A. de Mello Franco

"It is frequently necessary to excavate a tunnel for Civil Engineering purposes, or wells for petroleum exploitation, in laminated rock mass like schists or phyllites or in highly foliated gneisses. The determination of the pre-existing in situ stresses is essential, in order to assure the stability of these excavations. In most cases, the pre-existing triaxial stress field is arbitrary in relation to the tunnel or well axis. For these rock masses the concept of Generalised Plane Strain can be correctly utilized.There are closed form solutions for the calculation of stresses in anisotropic rock masses under Generalised Plane Strain conditions (Lehknitskii, 1981 and Hong , 1994). Based on these analytical solutions, established for the cases of Generalised Plane Strain, a synthetic problem will be formulated: the theoretical in situ stress tensor acting on this rock mass will be determined, with the aid of Bayesian Inverse Problem Techniques, as developed by de Mello Franco (2009). Additionally, the reliability of results obtained will be evaluated, in accordance with the research performed by this author. INTRODUCTIONThe Inverse Problem Technique, as developed in the paper, is based on the definitions and concepts obtained from the current literature and used for the solution of Inverse Problems, but the innovation to be presented is the utilisation of Bayesian Techniques and the determination of the reliability of the results obtained. This will be shown in a synthetic example where the determination of the in situ stress tensor, from strain measurements in a drill hole is supposedly performed. It is assumed that this drill has its axis arbitrarily placed in relation to the rock mass. Generalised Plane Strain conditions will hold for use with problem. The equations of Beltrami – Mitchel, in agreement to Lekhnitskii (1981) and Ong (1994), will be used in this synthetic case, for calculating strains, hypothetically measured in the hole before the final excavations. Finally a synthetic example for the determination of the in situ stress in a fully anisotropic rock mass, based on Bayesian Techniques and its reliability, developed in de Mello Franco (2009) is presented."

Jan 1, 2015