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By R. C. Gilmore

Underground longwall coal mining sections may develop explosive mixtures of methane-air in the mined-out gobs. If the panel are operated as bleederless or sealed gobs, progressive sealing along the gate roads as the longwall face retreats limits the flow of fresh air into the gob and thus deprives potentially explosive atmospheres of oxygen. In a project sponsored by the National Institute for Occupational Safety and Health (NIOSH), researchers at the Colorado School of Mines have used computational fluid dynamics (CFD) modelling to simulate the flow of gases in longwall gobs. Modelling indicates that targeted injection of nitrogen through the seals along the gate roads inbye the face can be used to control the size and location of methane and air clouds within the gob and to minimize or eliminate the explosion hazard resulting from the formation of flammable methane-air mixtures in longwall gobs.

Aug 1, 2013

By A. E. Cameron

The theory of atomic distribution of the stranger atoms in the space lattice of the solvent metal has been well developed by Rosenhain. It has long been known that the addition of one metal to another to form a solid solution increases the strength and hardness of the solvent metal. This increase is practically proportional to the amount of added substance up to the limit of solid solubility. To account for this increase in hardness and strength, Rosenhain assumes that the stranger atoms occupy positions on the solvent metal space lattice. Atomic attractions about the stranger atoms will not be the same as in the case of the pure metal, and there will thus be a disturbance of the orderly arrangement of the atoms on the space lattice, or a distortion of the lattice. Such a disturbance would interfere with the ease of slip along the planes and would thus tend to promote strength and hardness. Rosenhain notes that not only may there be a local disturbance of the lattice about the stranger atom but there may well be also a measurable change in the dimensions of the lattice as a whole. The relative amounts of local and general distortion of the lattice will depend upon the nature of the lattice itself. As Rosenhain says, "If the lattice is comparatively soft and flexible the distortion is likely to be largely local. In a stiff lattice, however, local distortion will be resisted and there will be a correspondingly increased general distortion."

Jan 1, 1927

By O. Moselhi

Material can be seen as the fuel needed to execute the project from inception to completion. Material installed provides good indicators of progress achieved onsite vis-a-vis project schedule performance. It correlates well with the role of the schedule performance index (SPI) of the earned value method (EVM). Material is recognized to have a significant impact on achieved progress for physical completion of project activities. This paper presents a study on the development of material status index (MSI) in support of the EVM. Unlike the SPI, the newly developed index account for the criticality of project activities. This is carried out considering the total float of each activity, percent float (i.e. the ratio of float to activity duration) and the total float of the path on which the activity is located. MSI, can independently and jointly with SPI provide root causes behind problems encountered during project execution. In turn MSI can reveal material related factors behind the performance detected by joint interpretation of the two indices. MSI serves to provide added value in alerting management to take corrective actions. While SPI and MSI may have different values, they can jointly augment and enrich the captured project status based on EVM. To demonstrate the capabilities of the developed MSI method, it is implemented on a case study. The case encompasses the construction schedule of a hydro power station constructed in northern Quebec. Different scenarios are adapted from the real case to demonstrate a set of practical aspects of the developed index. The results generated from the analysis of the case study illustrate the useful features of MSI beyond those of the traditional SPI on two fronts; causation and the considerations of criticalities of actives.

Aug 1, 2013

By David J. McDougall

"IntroductionThe production of pig iron, wrought iron bars and castings in Quebec during the 18th and 19th centuries has been so closely identified by historians with the Forges du St. Maurice on the St. Maurice River a few miles north of Trois Rivières (Three Rivers), that one is sometimes left with the impression that it was the only iron works that ever operated in the province. There were however, about twelve others, one of which was so completely re-built that it should probably be considered as a separate entity. All but two were constructed after the midpoint of the 1800s, coinciding with the growing Canadian demand for ""charcoal pig"" for railway car wheels and castings for industry, and about half of them were technically, if not economically, successful. The misconception about the Forges du St. Maurice may have come about either because of its long history of somewhat less than continuous production over a century and a half, or a tendency of Quebec historians to concentrate on events in the French-Canadian rather than the English-Canadian milieu, but whatever the reason, the other Quebec iron work s have been generally ignored. All but one of the Quebec blast furnaces could be described as ""preindustrial"" with capacities ranging between three and ten tons per day, the exception being the Radnor furnace built in 1892 with a maximum production of about 35 tons per day and an alleged capacity of 50 tons per day.Until a railway network was completed in the 1880s, the location of all the Quebec iron works except the Grantham Iron works was dictated by close proximity to adequate ore reserves because horse transport was of little use beyond a ten-mile radius. The other essentials of forest resources (mainly soft woods) for charcoal, limestone for flux and water power, were generally available except within a few miles on either side of the St. Lawrence river. Among the dozen iron works established in Quebec between 1732 and 1880, seven used bog iron ore in charcoal-fired furnaces."

Jan 1, 1983

By C. Mills, A. O. Burt

"The paper examines the role of gravity concentration in both an historical context and within the modern mineral processing industry. It discusses the principles of the process on both a theoretical and practical level. The importance of more mineralogy and its effect on the choice of the wide range of equipment available is discussed. The paper concludes with a discussion on the relative merits of gravity concentration with other forms of processing.IntroductionIt is an unfortunate, albeit popular, misconception among otherwise enlightened engineers in the mineral processing industry that gravity concentration was a process developed in the dark ages, perfected in the middle ages, and abandoned in the modern ages.Gravity concentration was developed in the dark ages - long indeed before that. Agricolau: cited examples of gravity concentration, crude examples admittedly, being practiced over 3000 years ago. However, gravity concentration is not dead. Far from it. As recently as 1978 it was reported that the total mineral tonnage treated by this process in the United States was greater than that processed by flotation. Coal represents the bulk of the or e treated by gravity separation in the U.S.A., with iron ore representing a major portion of the balance."

Jan 1, 1985

By P. Ashtari

Influence of Sr and Mn single and combined additions on the modification of the Fe-containing intermetallic compounds and mechanical properties of Fe-rich AA319 aluminum alloys have been investigated, The microstructural features e,g, morphology of the Fe compounds and eutectic Si has been correlated to the mechanical properties, It was demonstrated that modification of the Fe compounds from the platelet ß-Al5FeSi to the Chinese script a-Al8Fe2Si compound improves the UTS and elongation of the alloys by 10.3% and 83.9%, respectively. Moreover, the simultaneous modification of the Fe compounds and eutectic Si increases the UTS and elongation of the alloys by 15,3% and 116,1%, respectively.

Jan 1, 2005

By R. V. Kumar, C. Schwandt, S. Subramanian, S. Sampath, S. Vimalnath

Waste waters and industrial effluents containing toxic heavy metals such as Pb, Hg, As and Cr, beyond permissible limits (0.1 ppm, 0.01 ppm, 0.02 ppm and 0.05 ppm, respectively) (WHO, 2011), pose serious threats to the ecosystem, when discharged into the environment. It thus becomes imperative to monitor the concentration of the toxic heavy metals and treat them before discharging. In this study with the above objective in mind, a microbial sensor has been developed using P. aeruginosa cells drop coated onto a carbon paste electrode (CPE) for the detection of Pb(II) ions in aqueous solutions. Detailed biosorption experiments confirmed that complete bioremoval of lead could be achieved using P. aeruginosa cells under optimum conditions of pH and biomass loading. For the electro-analytical determination, the Pb(II) ions were initially preconcentrated on the P. aeruginosa modified CPE, reduced and then anodically detected with oxidation of Pb0 using differential pulse anodic stripping voltammetry (DPASV) technique. All the experiments were carried out in the presence of 0.1 M sodium acetate buffer and KNO3 as background electrolyte. The parameters namely pH, scan rate, biomass loading, deposition potential, deposition time and concentration of Pb(II) ions were optimized for the biomass modified CPE, to obtain maximum voltammetric response. Under the optimized conditions of pH 5.6, scan rate of 0.008 V/s, biomass content of 1.7–1.8×109 cells/mL, deposition potential of –1.2 V, and deposition time of 500 s, the developed microbial sensor showed a linear response for the peak current between 0.5×10-5 M and 1×10-8 M of Pb(II) ions with the R2 value of 0.9979. The lowest limit of detection (LLOD) was determined as 2.4×10-7M of Pb(II) ions (0.05 ppm). The redox mechanisms of Pb(II) ions on the P. aeruginosa modified CPE surface are discussed.

Jan 1, 2016

By Shantanu Patel, C. Derek Martin

"The objective of this work is to develop a practical numerical approach for applying the confining pressure to discrete element cylindrical triaxial tests. A layer of membrane particles with very low stiffness and extremely high contact bond strength was created around the lateral boundary of the cylindrical numerical specimen. To prevent the membrane particles from penetrating into the rock specimen on application of confining forces and to provide a smooth boundary surface, the space between the membrane and rock particles was filled using small-diameter packing particles. The results of this method were compared with those of rigid boundary method with confining pressure of 20MPa. The results obtained show that new approach gives both peak strength and post peak response that are in closer agreement with laboratory findings. BACKGROUNDThe discrete element method (DEM) has become the cornerstone for simulating both intact material and discrete fractures for low porosity strong rocks (ISRM Classes R3 to R6). Despite the advances in its application, simulating realistic behaviour of intact rock using the DEM remains a challenge. The bonded particle model was introduced as a potential solution for simulating the complex mineral grains in strong rock and other granular materials (Potyondy and Cundall, 2004; Utili and Nova, 2008; Salot et al., 2009). While some issues were resolved, a remaining challenge is the lack of the bonded particle model to simulate the brittle response commonly observed in strong rocks during the triaxial compressive test. Such behaviour is shown in Fig. 1 for Lac du Bonnet Granite at a confining pressure of 20MPa."

Jan 1, 2015

By L. Chunpongtong

ABSTRACT Oil sands production occurs on a massive scale, making orebody estimation a challenge. In rainy conditions, operators can have difficulty accessing ore at the mapped location. Without enough inventory as a buffer, the high-cost stockpile is depleted quickly, necessitating the removal of significant amounts of overburden and interburden to meet plant feed requirements. The inventory curve—a plot of ore inventory on a period-by-period basis—plays an important role in selecting an appropriate scheduling scenario. This paper presents a programmable method for creating an inventory definition by using a pit optimization tool.

Jan 1, 2014

By Haruka Takeura, Tomoaki Murata, Kazunari Yoshida, Masato Adachi

"Pure magnesium is a material with high functionality, however, the cold drawing of this material is very difficult, that is why, until this day there are no optimal cold drawing conditions. Furthermore, cold drawing of pure magnesium wire shows a problem with internal defects that occurs under certain conditions. In this research, the aim is the suppression of internal defects, and final target is to create the optimal cold drawing conditions for pure magnesium wires. The first step is the investigation of the drawing limit by using 250°Cannealed wire. As a result, reduction of 10% per pass was chosen for stable wire drawing. However, in this case, it was found that internal defects occurred at total reduction of over 45% during drawing. Investigation of intermediate annealing conditions that can suppress internal defects, and influence on internal defect that the die half angle and reduction per pass. As a result, it was found that the drawing condition capable of suppressing internal defects most efficiently was 13% reduction drawing by using under 6°half angle die. Consequently, it’s possible to manufacture a cold fine drawn pure magnesium wire of 100µm, without defects in the center of the wire and hindering its mechanical properties.INTRODUCTIONMagnesium is a light and high functionality material that has high vibration absorbency, heat dissipation, electromagnetic wave-shielding and recycling efficiency (Conruy, 1989). However, proper cold wire drawing conditions haven’t been established, that is why warm or hot processing is commonly used (Oishi, Mori, &Kawabe, 2005). As a result, strength improvement of the wires is not possible, that is why the production of medical tools is disregarded. If it was possible to cold draw magnesium wires, the applications for material products would expand. Further, in wire drawing such difficult processing material, if appropriate processing conditions are not selected, defects will be generated inside the drawn wire."

Jan 1, 2017

By Kazutoshi Haga, Batnasan Altansukh, Yasushi Takasaki, Mohd Yazid Bin Abdul Razak, Atsushi Shibayama

"In this study, the volatilization behaviour of arsenic (As) and antimony (Sb) from arsenicantimony bearing minerals such as tennantite (Cu12As4S13)/tetrahedrite (Cu12Sb4S13) in copper ore was investigated using a roasting process. Specifically, the thermal decomposition of tennantite and the arsenic volatilization were investigated under nitrogen and air atmosphere. The roasting experiments were performed at temperatures ranging from 500 to 1,200oC and different retention times using a laboratory electric furnace. The results indicated that over 95% volatilization was achieved at 700oC. On the other hand, when the temperature increased to 1,200oC, volatilization rate of Sb reached to 90%. Therefore, volatilization of Sb requires high temperature compared to As. It suggests that As and Sb can be separated using temperature difference. Selective removal of As is possible at 700oC, subsequently Sb can be recovered as a volatilized product by increasing the temperature to 1,200oC. Meanwhile, volatilization of Cu and Fe was not observed on these conditions. The content of As and Sb in the residues obtained from roasting at 700 and 1,200oC was less than 0.3 and 0.75 mass%, respectively. The Cu content in solid residue at 1,200oC increased to 34 mass%. The clean copper concentrate with lower amounts of arsenic and antimony was obtained from the process. INTRODUCTIONRecently, arsenic (As) and antimony (Sb) contents in copper (Cu) concentrates are increasing year by year. Arsenic and antimony are present with Cu minerals such as enargite (Cu3AsS4), tennantite (Cu12As4S13) and tetrahedrite (Cu12Sb4S13) that associate with copper sulfides [chalcopyrite (CuFeS2) and bornite (Cu5FeS4)]. They are normally concentrated by flotation and treated in copper smelters. However, treatment of copper concentrates containing high amounts of arsenic and antimony by a smelting process is difficult due to environmental implications of toxic arsenic and antimony. As demand for copper continues to grow, the need to source copper from several types of resources including those that contain high levels of As/Sb becomes necessary. Therefore, a novel processes for the treatment of As/Sb bearing Cu concentrates are required. Reviews on copper resources such as enargite, tennantite and tetrahedrite containing high amounts of arsenic and antimony are covered widely in literatures by many researchers (Padilla et al., 1998; Welham, 2001; Vinals et al., 2003; Guo & Yen, 2005; Balaž & Achimovicova, 2006a; Filippou et al., 2007; Mihajlovic et al., 2007; Lattanzi et al., 2008)."

Jan 1, 2016

By F. Awotwe-Appiah, P. Koshy, J. Dankwah, J. R. Dankwah

This research investigates the generation of an effective carbonaceous material from waste ‘pure water sachets’ and their subsequent utilisation as reductants for the reduction of the Opon Mansi iron ore. Composite pellets of Opon Mansi iron ore and pulverised carbonaceous material generated from waste pure water sachets were heated from room temperature to 1200 °C in a gas fired furnace for seventy minutes. The reduced pellet was analysed chemically for its oxygen and carbon content using a LECO Oxygen/Nitrogen and LECO Carbon/Sulphur analysers, respectively. It was observed that nuggets of metallic iron were readily produced with the carbonaceous materials acting as an effective reductant and source of chemical energy. XRD analysis of waste ‘pure water sachets’ revealed that the polymer was semi-crystalline with peaks that were identical to those of high density polyethylene (HDPE). Gas emission behaviour of the iron ore-PWS pellet was studied in a horizontal tube furnace at 1200 °C using an infrared gas analyser; the results revealed an exhaust gas rich in the reducing gases CO and CH4 along with CO2.

Jan 1, 2015

By G. Bartolacci

In a COREM-McGill collaborative research and development project, gas dispersion parameters and froth properties were manipulated in a copper flotation plant to study interactions between the collection and the cleaning zones. In this paper, specific work on developing some relationships between operating conditions and froth stability in several different types of flotation cells is reported. Froth stability, measured by image analysis, was related to the following process conditions for specific flotation machines in an industrial case study: Gas flow rate, collector dosage, pH, frother type and dosage. Across the range examined, froth stability was improved through an increase in gas flow rate and/or frother dosage. Metallurgical results (grade and recovery) showed that both gold and copper were dependent on froth stability. Results indicated that flotation conditions could be optimized by monitoring froth stability.

Jan 1, 2007

By W. Dingley, G. R. Hoey

"AbstractWear of six types of grinding balls was compared with and without corrosion inhibition in grinding Ni-Cu sulphide and hematite ores in laboratory ball mills. Forged steel balls (Rc 60 to 65) and three types of white cast iron balls (Rc 50 to 65) were susceptible to corrosive wear and two types of stainless steel balls [AISI Type 440C (Rc 65) and AISI Type 302 is; 35)] were relatively immune. The relative wear rates of the five types of hard balls (Rc 50 to 65) were dependent on the corrosivity of the ore. Ranking of the hard balls with respect to wear resistance was consistent for the sulphide and hematite ores in the presence of corrosion inhibition, whereas their ranking was different for the two ores in the absence of inhibition.The electrochemical potential of the grinding balls was measured during grinding and was found to be a useful measurement for assessing the susceptibility of an alloy to corrosive wear. Reduction of ball wear for forged steel and white cast irons with corrosion inhibition was concomitant with a shift of ball potential to less active values. Ball potentials in the presence of inhibition were indicative of non-corroding metal surfaces.IntroductionA PREVIOUS STUDY by the authors (1) showed that corrosion inhibitors - sodium nitrite, sodium chromate and sodium metasilicate - reduced wear of forged steel grinding balls by up to 49% in grinding Ni-Cu sulphide ore. Although the mechanism of wear reduction was not elucidated, it was concluded that corrosion must play a significant role in the wear of grinding media. Remark and Wick (2) of Battelle Pacific Northwest Laboratories have also evaluated corrosion inhibitors for the reduction of metal wear using abrasive and n on- abrasive te sting procedures. Their research was sponsored by 16 companies throughout the world. Preliminary results indicated that anodic inhibitors prevent from one-fourth to one-half of the loss due to corrosion."

Jan 1, 1977

By S. E. Jackson, L. J. Cabri

Quantitative determination of gold at sub-ppm concentrations in sulphide minerals is an important component of deportment studies for sulphide-gold deposits. Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS) analysis is preferred for this application because it rapidly and cost-effectively provides spatially resolved (<20 pm), low ppb concentration data for gold and other elements in mineral grains. Recent advances in LA-ICP-MS analysis include the development and application of elemental mapping. Raw signals from multiple line scans or lines-of-spots are deconvoluted and calibrated to generate elemental maps which provide detailed information on spatial variations of gold and other elements within and between grains.

Jan 1, 2011

By Edward Martinez

Due to its unique properties, chrysotile asbestos is used in many diversified applications. In recent years, a better understanding of the structure and properties of chrysotile has evolved due to the research efforts of many investigators. A summary of the results of some of these investigations is given. An attempt is made to show the relationships between the properties of chrysotile and its crystal structure. Examples taken from the literature are cited in which methods have been developed for modifying the properties to improve the performance of asbestos in some applications. These include the effect of pH on the positive zeta potential and the addition of sodium silicate to improve filtration characteristics. The dehydroxylation and formation of forsterite when chrysotile is heated are also discussed.

Jan 1, 1966

By H. L. Ramandi, P. Moore

"The corrosion of support bolts in underground mines has become an increasingly prevalent issue over the past two decades. With an increase of premature failures due to Stress Corrosion Cracking (SCC), it is evident that understanding the environmental factor influencing the cable bolt corrosion is critical for maintaining effective ground support hence the safety and productivity of underground spaces. Experimental testing of rock and cable bolts were accomplished in a variety of packings, including saturated clay, saturated coal, mine water and grout/cement to investigate their corrosion behaviours. Water samples were obtained and analysed for pH and electrical conductivity (EC) during the experiment. After a period of 76 days the bolts were retrieved and analysed visually. Primary factors were found to be the presence of geological materials and the aeration of the bolts, i.e. the vicinity to air and air flow, while secondary factors were observed to be pH levels and EC. It was also found that the coal/clay interfaces and the water/grout/cement interfaces are non-relevant to corrosion of rockbolts and cable bolts. The proposed framework can be applied to other reinforcement materials used in underground spaces for improved understanding of corrosion environment.INTRODUCTION Rock bolts and cable bolts are the major reinforcement elements used in mining industry to improve the rockmass properties for safe and productive mining. They are normally used to pin large beams or blocks of rock in underground mines to stabilise the rockmass in the roof (strata) against collapse. The rockbolts are typically low cost hot rolled rebar while cable bolts are composed of strands of wire, normally wound together around a central king wire (Hyett and Bawden, 1993; Vandermaat, 2014). The typical length of the bolts in underground mines is 2.4 m and 4–12 m for rockbolts and cable bolts, respectively (Vandermaat, 2014; Windsor and Thompson, 1997). Cable bolts are much more flexible and usually offer a much higher load capacity than rigid rockbolts. Their increased length and flexibility allows cable bolts longer than the height of a roadway to be used in underground mines."

Jan 1, 2017

By K. Sun

The exothermic behavior of the intermetallic reactions inside an Al-Mn metallic powder compact and its assimilation fundamentals in molten aluminum were examined. In this study cylindrical compacts were manufactured and tested. The experimental work involved simultaneous temperature measurements of three thermocouples as well as detection of the apparent weight of the cylindrical specimen during its assimilation in liquid aluminum. The details of the intermetallic reactions prior to the compact complete disintegration were investigated by microscopically studying the morphology and local composition in a partially reacted compact. The variation of manganese concentration in the melt was determined by chemically analyzing the samples taken from the molten aluminum at specific time intervals. The exothermic reaction increases the compact&apos;s temperature above that of the liquid aluminum. In tandem with this exothermic reaction, the compact is suffering a swelling action. This swelling action disintegrates the cylindrical specimen, which is assimilated into the liquid aluminum. The intermetallic reactions proceed in a stepwise manner. Both the bath temperature and the compact composition impact on the exothermicity of the intermetallic reactions. However, when the amount of Mn in the compact is greater than 75-wt%, the maximum centerline temperature rise is slightly reduced as Mn amount increases.

Jan 1, 2004

By G. Gabra, M. Nagamori, J. J. Panneton

"RESUMELa calcination contrôlée de 10 serpentine permet de produire de 10 magnésie active. Le degré de I&apos;activation est mesure par 10 solubilité du magnésium dans les acides faibles tel que I&apos;acide acétique, La serpentine contenue dans les résidus d&apos;amiante du Québec peut donc être activée par calcination. Le teneur en magnésie active des rejets d&apos;amiante calcinés est fonction de divers paramètres: température, temps de calcination, granulométrie, etc. Les rejets d&apos;amiante de différentes provenances démontrent des comportements thermochimiques différents qui sont étudiés dans Ie présent travail au moyen d&apos;ATD, de TG, de la diffraction des rayons X et de la lixivation par l&apos;acide acétique. On constate qu&apos;un maximum d&apos;environ 80% de la magnésie totale peut être activé dans certains rejets d&apos;amiante du Québec et Ie degré d&apos;activation dépend de la provenance.vIntroductionOn sait depuis longtemps que la serpentine, Mg3Si2O5(OH)4, un silicate hydroxylé de magnésium, devient amorphe lorsqu&apos;elle perd de I&apos;eau d&apos;hydratation entre 600 et 700 °C. La serpentine ainsi calcinée est alors dissociée en magnésie et en silice. Cette magnésie, dite active, est soluble dans un acide faible ou même dans les solutions de sels d&apos;ammonium.Plusieurs precédés chimiques ont été proposés afin d&apos;extraire sous forme de composés magnésiens la magnésie de la serpentine. La plupart de ces procédés comportent une activation par calcination de la serpentine préalablement à une Iixiviation par un acide ou par une solution d&apos;un sel d&apos;ammonium.Malgré la contamination par Ie fer et par d&apos;autres éléments, les compositions chimiques des rejets de différentes mines d &apos;amiante du Québec, présentées au tableau 1, sont très proches de la serpentine typique. Puisque Ie degré d&apos;activation de la magnésie varie grandement d&apos;une serpentine à I&apos;autre lors de la calcination, la première étape de la recherche sur la transformation chimique des rejets d&apos;amiante du Québec se résume à une étude de leurs comportements thermochimiques."

Jan 1, 1982

By S. Parkash, A. J. Szladow

Vigorous agitation of suspensions of coking coals in water (or light mineral oils) will often result in catast rophic loss of caking properties. It is shown that this deterioration is not a consequence of oxidation of the coals (by dissolved oxygen), but that it can be qualitatively connected with internal "solid-state" reactions which appear to derive their activation energies from cavitation of the liquid.

Jan 1, 1971