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By S. Abu-Samra

By virtue of its complex nature, the construction industry comprises a wide spectrum of interrelated variables and factors. This multifaceted character of the construction industry puts the use of engineering modeling tools and techniques on top of project management necessities. This research introduces a macro-level earthmoving management system using Genetic Algorithms (GAs) to reach the optimum allocation of earthmoving equipment. The Earthmoving Equipment Management System (EEMS) functions through four integrated modules: (1) A Central Database containing information about projects and available equipment; (2) An Equipment per Segment Selection module that calculates the cut and fill quantities, plots the Mass Haul Diagrams, and selects the equipment types to be used for each segment; (3) An Equipment Pool module which determines the production and cost for each available equipment, based upon the project site conditions; and (4) An Optimization Engine equipped with a GA optimization solver. This engine formulates the optimum earthmoving cost for all projects, by changing the number of allocated equipment. The Optimization Engine takes into account the number of available equipment and calculates the weekly equipment allocation. The EEMS model was implemented on an earthmoving company conducting five different projects on hand. The model proved to be an effective tool in providing decision makers with optimum equipment utilization on a multi-project scale to minimize the earthmoving cost. The results were then compared with the company?s existing micro-level management system, demonstrating better performance on the level of savings, amounting to 13% of total earthmoving cost.

Aug 1, 2013

By L. Tong, D. Robinson

"The stirred milling of nickel laterites offers possibilities for improving liberation and selective size reduction of soft nickel-bearing minerals in laterites. Batch grinding tests were performed in a netzsch™ lME4 stirred mill on siliceous goethitic, goethitic, and saprolitic nickel laterites. Tests on the -2,000 µm sample displayed the effects of selective comminution. The -38 µm product of grinding the -2,000/+38 µm feed confirmed the effects of selective grinding and nickel upgrading. Size classification followed by stirred milling is recommended for nickel upgrading. The energy requirement in the stirred milling was also investigated.RÉSUMÉ le broyage par billes de latérites comportant du nickel offre des possibilités d’amélioration de la libération et de la réduction sélective de la taille des minéraux nickélifères tendres dans les latérites. Des essais de broyage en vrac ont été effectués dans un broyeur à billes netzschMD lME4 sur des latérites nickélifères à goethite siliceuse, à goethite et saprolitiques. Des essais sur l’échantillon -2000 µm présentaient des effets d’une comminution sélective. le produit -38 µm de l’alimentation -2000/+38 µm confirme les effets d’un broyage sélectif et du rehaussement de la teneur en nickel. Pour améliorer la teneur en nickel, il est recommandé de classifier le minerai en fonction de sa granulométrie, puis d’effectuer un broyage à billes. l’énergie requise pour le broyage à billes a aussi été étudié."

Jan 1, 2015

By G. T. Lapidus, R. Zárate-Gutiérrez

Selective leaching of lead from a Pb-Ag-Zn concentrate with hydrogen peroxide in citrate solutions was studied at room temperature. Leaching tests were performed, varying the H2O2 concentration and the solid-liquid ratio, holding the solution pH constant at 7, and the citrate concentration at 1 M. Lead extractions of 100 % were achieved with 4 and 5 times the stoichiometric quantity needed to form elemental sulfur, with only a small amount of metal impurities dissolved (Ag, Zn and Fe). The lead solubility limit at those conditions was found to be ~21 g L-1. X-ray diffraction analyses of the leach residues were free of galena (PbS), while other metal sulfides, such as sphalerite (ZnS), chalcopyrite (CuFeS2) and pyrite (FeS2), were basically unaffected.

Jan 1, 2014

By T. A. Utigard

To improve recoveries of Ni, Cu and Co in the Inco flash furnace, a new operating concept was investigated. By adding sufficient coke to form a supernatant coke layer, a reducing barrier would form allowing for improved reduction of descending oxidized sulfide mineral particles formed in the flame. The objective of this investigation was to study the kinetic mechanism and efficiency of the coke layer to produce a sulfur deficient matte. The mechanism and rate of carbon reduction of each of the phases formed in the flash flame, i.e. sulfides and oxysulfides were investigated by means of X-ray visualization tests. Graphite-slag reduction was also conducted for comparison purposes. In the case of slag, poor wettability and the formation of a gas film on the surface of the carbon reductant are often blamed for limiting the reaction surface area that ultimately results in poor reaction kinetics. The X-ray visualization tests confirmed that matte and oxysulfide wet coke better than slag and that the rates of reduction of matte and oxysulfide are faster than that of slag.

Jan 1, 2005

By Y. Mudryk, D. Paudyal, K. A. Gschneidner, V. K. Pecharsky, M. Khan

"Rare earth intermetallic compounds are utilized commercially as magnetic and battery materials, electron gun electrodes, etc. Several of these intermetallics will be briefly discussed. There are many other rare earth intermetallic compounds which are not utilized industrially but have unusual properties which are of fundamental interest and may have future technological applications. Several of these materials are discussed as well.INTRODUCTIONTens of thousands of rare earth intermetallic compounds exist, but physical properties (primarily their magnetic behaviors), other than their crystal structures have been measured for only a small percentage of these materials. Among these are the commercially important compounds: Nd2Fe14B, and the SmCo5 – Sm2Co17 family – well known high strength permanent magnets; (Tb0.3Dy0.7)Fe2, Terfenol-D, a giant magnetostrictive material; LaNi5Hx a critical component of the rechargeable Ni metal hydride batteries; and LaB6 an electron emitter. There are, however, many other intermetallic compounds which are not utilized industrially, but none-the-less, exhibit interesting, and sometimes, exotic physical properties which are of fundamental interest and may have some future technological significance. These include: the giant magnetocaloric effect compounds Gd5Si2Ge2 and La(Fe13-xSix)Hy; the RCu and RAg families of ductile intermetallics; the mixed intra-lanthanide (R,R')Al2 compounds in which magnetic transitions disappear and reappear as one R is substituted for by R'; and GdNi which exhibits large dilations along two crystallographic directions and a larger contraction in the third direction at the Curie temperature resulting in zero volume change as GdNi orders magnetically via a second order phase transition.COMMERCIALLY IMPORTANT INTERMETALLICSNdFeB Permanent MagnetsThe Nd2Fe14B permanent magnets were discovered in 1984 independently in the USA and Japan. It is a ferromagnet and with proper heat treatment and processing Nd2Fe14B is the strongest near room temperature permanent magnetic material known today. This intermetallic compound is utilized as a permanent magnet in many applications, such as electric motors (e.g. the modern automobile contains up to 35 electric motors), spindles for computer hard disc drives, microphones and speaker magnets for cell phones and other audio equipment, direct drive wind turbines, actuators, and Magnetic Resonance Imaging (MRI) units. There are two kinds of NdFeB permanent magnets – bonded and sintered. The bonded magnets have a lower magnetic strength than the sintered magnet. The highest strength magnets are obtained by small substitutions of Dy (up to a maximum of 10%) for Nd, because Dy can significantly increase the coercivity and thus the energy product (a measure of the magnetic strength or hardness). The bonded magnets account for about 12% of the NdFeB market (~82 metric kt per year, containing ~20 kt/a of Nd). The NdFeB permanent magnet market is growing at a rate of about 15% per year. (Burzo & Kirchmayr, 1989; Kobayashi & Hirosawa, 2001; Coey, 2011)."

Jan 1, 2012

By \/eena Sahajwalla, Jonathan Dicker, Paul O'Kane, Cath Skidmore, James Dankwah, Magdalena Zaharia, Rita Khanna, David Knights, N Saha-Chaudhury, Somyote Kongkarat

Due to the inherent limitations of current methods of disposal of end of life polymeric materials, avenues are researched towards developing alternative, environmentally friendly and economic recycling processes. Different polymeric materials (i.e. rubber, high density polyethylene (HDPE) and polyethylene therephtalate (PET)), quite distinct in terms of chemical structure and composition, were considered in the present study as carbon resources in EAF steelmaking. Investigations were conducted in both laboratory and industrial scale steelmaking to assess the effectiveness of using these materials as carbon sources for slag foaming in EAF steelmaking. Slag foaming is important because it enhances furnace efficiency.

Jan 1, 2011

By Sepulvedam Jaime E., Levi Guzmán Rivera

"Grinding media consumption rates and their dependence on key operating conditions in semiautogenous grinding mills is analyzed on the basis of a detailed mathematical model recently developed by Moly-Cop´s specialists which describes and takes into account the three primary media consumption mechanisms, namely: abrasion/corrosion, surface spalling and impact ball breakage. The influence of key mill operating conditions – such as ball filling, discharge grate opening, mill speed, lifter profile, and ball quality – on their corresponding grinding media consumption rates is explored via a variety of model simulations, discussing in every case the independent contribution of each of the indicated consumption mechanisms to the estimated total ball consumption rate.INTRODUCTIONA thorough understanding of the independent contribution of each grinding media wear mechanism is extremely important, especially in semi-autogenous grinding (SAG) operations where macrowear (spalling) and ball breakage cannot be ignored or neglected. The high impact conditions imposed in modern SAG milling environments has created serious challenges for grinding media manufacturers since their products must be able to perform with minimal breakage and surface spalling.GRINDING MEDIA WEAR MECHANISMFor SAG milling operations, at least 3 different mechanisms have been identified as the main contributors to the observed overall grinding media consumption, here referred to as: abrasion / corrosion, ball breakage and surface spalling.Wear by Abrasion/CorrosionThe abrasive/corrosive wear mechanism has been discussed in depth in previous publications (Benavente Hector, 2007; Guzman Levi, 2014; Sepulveda and Morrow, 2014). The most widely accepted approach to mathematically characterize the consumption (wear) kinetics of grinding media in rotary tumbling mills is known as the Linear Wear Theory (Prentice, 1943; Norquist, 1950; Sepulveda, 2004) which claims that—at each instant 't' after a grinding body enters the mill load—the rate at which the body loses weight is directly proportional to its surface area exposed."

Jan 1, 2016

The comminution circuit at Tarkwa Gold Mine was commissioned as a Single Stage SAG mill operated in closed circuit with hydrocyclones designed to process 4Mtpa. The circuit was later expanded by adding a secondary ball mill in closed circuit with hydrocyclones with a view to treat 12Mtpa. The change in the circuit configuration and assigning the low aspect ratio SAG mill for primary grinding application makes the Tarkwa experience unique in terms the optimisation strategy and operating philosophy. This paper reports the findings from a series of surveys performed on this plant. The surveys reported include data obtained when the SAG mill was operated as a single stage mill in closed circuit with hydrocyclones and also SABC mode under two different feed conditions. The differences in operating philosophy between the initial single stage SAG circuit and the current SAG/Ball mill circuit are discussed.

Jan 1, 2012

By N. Shi, T. G. Joseph

ABSTRACT One-twentieth-scale field trials for conventional and concept dipper designs were compared to mid- and ultra-class-sized conventional dipper performance. Digging effort was used as the performance indicator for comparison. It was shown that linear relationships exist between dipper capacity, suspended hoist load, and peak hoist load. A ratio of conventional and concept dipper performance at the 1/20th scale was then evaluated to allow prediction of the performance of an ultra-class concept design using an independent ultra-class conventional dipper dataset. The outcome indicated a peak hoist requirement of 15.5% less to achieve the same production as the conventional design.

Jan 1, 2011

By Laura Kelsey

Contaminant Robust In Situ Water Extractor CRIWE Nafion-based water clean-up Extract purified water from natural extraterrestrial sources In situ water processing for downstream electrolysis Chemically resistant to process contaminants such as acid

May 1, 2013

By L. R. Plitt

A new simple correlation has been developed to evaluate the performance of classifiers. The new correlation has been tested on existing data from 150 different hydro-cyclone classification tests. It is shown that this model provides a meaningful improved method of mathematically describing the classification process.

Jan 1, 1971

By F. Henríquez, V. Iriarte, L. Vinnett, J. Yianatos, F. Díaz

Metallurgical characterizations of the collective (Cu/Mo) and selective flotation plants were carried out in Minera Los Pelambres, Chile. The selective plant allows the valuable minerals of Cu and Mo to be separated. The evaluation involved two surveys consisting of metallurgical sampling as well as residence time distribution (RTD) measurements to determine load distribution. The RTD data were obtained in real-time by means of the radioactive tracer technique. In addition, metallurgical data was reconciled and supported by effective residence times. In the collective plant, a performance comparison of parallel rougher circuits was carried out, which included a bank of six mechanical cells of 250 m3 and banks of nine mechanical cells of 130 m3. In the selective plant, the Cu and Mo evolution along the plant was evaluated. The results in the selective plant allowed for performance evaluation of mechanical and pneumatic cells in primary flotation. In both plants, mineral losses were evaluated and their relationship with circuit configuration (cell types and circuit layout) was determined. The metallurgical characterization was a powerful tool to evaluate circuit performance and to detect improvement opportunities at industrial scale.

Jan 1, 2015

By Harry F. Weaver

WHEN 1 was assigned by the Director of the United States Bureau of Mines to present a paper at this annual meeting of the Mining Society of Nova Scotia, 1 was grateful, honoured, and elated to realize finally a life-long desire to see your beautiful land and visit with you who have the good fortune to live and work here. Naturally, in preparing for this important event, 1 wanted to give you something of special interest within the limits of the subject so I chose an area dose to my heart -the operation of our Federal coal mine inspection service, which has, as its fundamental purpose, the prevention of accidents in and around ?Coal mines. In 1957 the United States had 10,879 active coal mines scattered throughout 28 States and the Territory of Alaska. The production of coal for the year was about 515,472,000 tons, including 2.5,472,000 tons of anthracite and 490,000,000 tons of bituminous coal and Hgnite. Anthracite is mined principally in a comparatively small area of one State. AU the 28 States and the Territory produce bituminons coal and/or lignite. The beds mined range from 18 inches to more than 100 feet in thickness and from the horizontal to the perpendicular.

Jan 1, 1958

By L. Trytten, S. Bass, P. Nawrocki, J. Mercer

The Sherritt Fort Site nickel refinery and fertilizer plant has been operating continuously since 1954. The ammonia leach process uses ammonia and sulphuric acid, producing nickel and cobalt and an ammonium sulphate byproduct. One of the features of an ammonium sulphate based process is the aggressive nature of ammonium sulphate to concrete and structural steel. After six decades of operation, portions of the structural steel and concrete at the Sherritt facility have become degraded. Infrastructure replacement programs started in earnest more than a decade ago with pipe racks and electrical infrastructure, and have now progressed into building steel. Replacing and repairing this infrastructure within the tight constraints of an operating plant poses several difficult challenges. This paper will outline the approach taken to accomplish this difficult work, and discuss key learnings from the ongoing program.

Jan 1, 2015

By H. J. McQueen

The irregular history of Mg wrought products is briefly described. The temperature and strain rate dependence of microstructural evolution, flow stress and ductility of Mg alloys in hot working, are described. The flow curves rose rapidly to a peak stress which was lower as temperature T rose and strain rate e declined and above 300°C the curves extended into plateaus until failure. Clearly grains not oriented for slip undergo mechanical twinning in the initial stages (a 0.15) at all temperatures. Basal slip proceeds in suitable grains and in the twins. The stress concentrations at grain and twin boundaries lead to slip on non-basal systems and to the formation of subgrains with greater dynamic recovery (DRV) at higher T or lower e. With increasing strain, misorientation builds up resulting in dynamic recrystallization (DRX) first at twin intersections and later at grain boundaries which have become quite serrated. Even after extensive straining at high temperatures, the new grains are found mainly along the boundaries of the original grains, leaving their centers with only basal slip except when nucleation at twins leads to completion of DRX throughout a grain. Despite similar shear modulus and melting point to Al, hot mechanical forming behavior of Mg alloys differ due to differences in crystal slip systems, twinning, and second phases. Moreover, the influences on forming of alloy additions (solutes, segregation in casting, dispersoids, precipitation) and impurities are not as well catalogued as for Al. Despite the benefits from dynamic recrystallization, varied grain orientation effects, heterogeneous substructures and the resulting stress concentrations result in considerably lower ductility for Mg alloys at the same stress level as for Al materials. Application of these theories to extrusion, rolling and forging and the effects on product properties are surveyed.

Jan 1, 2006

By John A. Hudson, Xia-Ting Feng, Joseph S. Y. Wang

Evolution over decades and progress over last five years have been made in many topics of interests to rock mechanics, geosciences, physics, and multi-disciplinary interactions in underground research laboratories and development facilities, as well as in underground energy recoveries and environmental assessments. Rock mechanics and geotechnical engineering advances are associated with quantifications of disturbed/damaged zones and rock alternation and bursting processes and creation of underground spaces and accesses associated with deepening of shafts and lengthening of tunnels. Geophysics and earth sciences advances are associated with continuing collections of seismic, electromagnetic, and gravitational data and conducting various thermal, hydrological, mechanical, chemical, and biological investigations, both separately, simultaneously, and in different coupled ways. Astroparticle and underground physics advances are associated with many long term experiments to detect rare events and needs for increasing larger and deeper halls to accommodate next generation detectors, shielings, and isolations. There are also increasing interesting in underground settings to explore multidisciplinary and inter-disciplinary sciences and technologies. Energy and environmental sciences and assessments have evolved from traditional oil and gas focuses to recent activities associated with green resources and alternative recovery/disposal strategies. The evolution and progress of these interdependent and related fields are discussed in this quadrennial Congress.

Jan 1, 2015

By T. G. Joseph, E. Lampard

ABSTRACT: Surface mining operations must manage variability from within their operations as well as variability imposed upon them by external forces. A framework to manage both internal and external variability through the continuous review and adjustment of a mine plan during active mining lifetime operation is introduced, to minimize lost production and maintain operational safety. The observational approach of “observe, evaluate, interpret, predict, and adapt” is employed as the backbone of this approach. Although written with a surface mining operation in mind, the framework outlined in this paper would be equally applicable to any mining or processing operation.

Jan 1, 2011

By H. Karakul

Determination of P-wave velocity (Vp), which is closely related to intact rock, is a nondestructive, easy and less complicated procedure. Due to these advantages, there is an increasing trend to predict the geomechanical properties of rocks from Vp. In addition to mineral content, cementing material and porosity, degree of saturation (Sr) are also other factors influencing geomechanical properties of the intact rock. However, up to the present, in the studies on the prediction of geomechanical properties of rocks from Vp, the effect of Sr has not been investigated. By considering this issue, in this study, it was aimed to correlate strength properties (uniaxial compressive and tensile strengths) and Young’s modulus with Vp of various rock types under different degrees of saturation. In addition, geomechanical properties of rocks were estimated from theoretical P- and S-wave (Vs) velocities, which were calculated based on their mineralogical compositions. For this purpose, fourteen different rock types were collected from several parts of Turkey and a comprehensive laboratory testing program was conducted. In the statistical analyzes, a series of different prediction relationships were developed by using independent variables such as Vp, Sr and effective clay content (ECC). Simple regression analysis results indicated that although prediction of the geomechanical properties of rocks from Vp at different degrees of saturation was possible, the equations developed would yield some under- or over-predictions. On the other hand, the multivariate equations developed have very high prediction performances and are very useful tools to estimate the geomechanical properties from the measured Vp at any Sr value. In addition to mineralogy, the variation in geomechanical properties with increasing Sr is also associated with the combined effect of porosity and clay content, which is first described in this study by the term Effective Clay Content (ECC). It is also noted that strength properties of rocks at any Sr may also be estimated using the empirical relations based on the theoretical Vp and shear-wave velocity (Vs) values, which are calculated from their mineralogical compositions.

Jan 1, 2015

By R. L. Veenstra

This paper explores the connection between the stresses observed and the failure mechanisms present in the modelled cemented paste backfill. In order to look at this connection, the authors have used a previously developed model to conduct a sensitivity analysis of the model?s strength and permeability input parameters. The results from the sensitivity analysis were then compared to determine what causes modelled stresses and failure mechanisms to vary. Increased insight into the behaviour of the modelled paste will help clarify how paste behaves in the field.

Aug 1, 2013

By Yan-Jun Shen

The rock mass classification system, BQ (basic quality), is the only national system that is suitable to most kinds of rock engineering in China. It uses two main aspects of the rock mass, the intact uniaxial compressive strength (UCS) and the rock intactness index (KV), to obtain the rock mass BQ. The index KV could be measured by the acoustic wave method. However, because this method is an indirect approach to characterize the rock mass structure, misfits often occur between the test results and the actual rock mass characteristics. Therefore, a new parameter KGSI expressed by the geological strength index is proposed to replace the original KV, and a new method is presented to express the value of BQ as a function of the UCS and the KGSI. Then, the underground excavations at five hydropower stations were chosen as examples to study the relationship between the revised BQ and the each of the international systems (RMR, Q or RMi). In addition, the applicability of the RMR, Q, or RMi system is discussed for China?s rock characteristics and geological conditions, and suggestions are given for improving the revised BQ system.

Aug 1, 2013