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By A. Banerjee, J. P. Weiler, J. Jekl, J. T. Wood, R. Berkmortel

"The work presented here is part of an ongoing project designed to develop predictive capabilities of the local mechanical properties, and thus, structural behaviour of a thin-walled high-pressure die-cast AM60B magnesium alloy component. This work focuses on developing correlations between process parameters and local microstructure. Numerical simulations of the die filling and solidification behaviour of the AM60B component were used to estimate local process parameters such as solidification rate, temperature gradient, filling velocity, etc. These estimated parameters were used to establish semiempirical correlations with measured VALUES (of the local microstructure measured in regions throughout the component of different solidification conditions. INTRODUCTIONHigh-pressure die-cast magnesium alloys are experiencing increasing use in structural automotive components. A strength-to-weight ratio comparable to steels and its ease of castability allow for these alloys to be utilized in such capacities as instrument panel beams, seat and door frames, and engine cradles, among others (Gjestland and Westengen, 2007). However, the current use of these alloys is limited due to variations in local mechanical properties. These local property variations restrict part designers to assume lower than actual properties, resulting in larger sections, thus diminishing the light-weighting advantages of magnesium alloys. If these local property variations could be predicted, part designers would be able to optimize die-cast magnesium alloy components and fully take advantage of the light-weighting capacity of these materials.The work presented here is part of an ongoing project aimed at developing predictive capabilities of the local mechanical properties, and bulk mechanical performance, from variations in local microstructure, and ultimately from local process parameters in die-cast magnesium alloys. This project, unique in its nature, is based upon the results determined from fifty sequentially cast AM60B magnesium alloy instrument panel beams provided by Meridian Lightweight Technologies (shown in Figure 1)."

Jan 1, 2012

By G. J. Kipouros, P. W. Kingston, W. F. Caley

"Current practice in advanced materials processing has involved the dispersion of a second-phase, commonly SiC, glass, or other non-metallic fibres/whiskers/particulates to enhance physical characteristics of the matrix. These matrices may be either ceramic or metallic but in either case it is important that the physical and chemical properties of each phase be compatible. The dispersed, finely divided second phase is often both expensive and foreign-produced and may exhibit chemical instability at elevated temperatures. Thus, it would appear that certain naturally-occurring industrial mineral fibres/whiskers/particulates might offer an attractive and low-cost alternative. Suitable candidates, such as wollastonite and sillimanite, are available in Canada and may be milled to produce particles whose shape is appropriate for this application. It is suggested that wollastonite, in particular, may be a useful modifying agent in metal matrix composites utilizing AI, Al-Si, Zn-Al or other light metals and alloys. In addition, the possible use of these minerals in ceramic matrix materials is also addressed, with reference to a preliminary thermodynamic analysis of the systems involved.IntroductionBackgroundA composite material may be thought of as consisting of a matrix component, the properties of which are improved by the addition of a second component or dispersed phase which forms a distinct three-dimensional interface with the matrix. This matrix is commonly either metallic or ceramic, which leads to the two most popular types of composites: metal-matrix composites (MMC); and ceramic-matrix composites (CMC).Such materials are by no means new. Early composites include fiberglass, mixtures of plaster and horsehair in wall plastering, as well as use of natural materials such as bamboo in fishing rods. Some of the newer applications include high strength, low-weight bicycle rims, as well as the more familiar role in aircraft and automobile engine components."

Jan 1, 1993

By Sukumar Bandopadhyay, Arunapuram Sundararajan

"Unique production and environmental problems are associated with multiple seam mining where dragfines are used for overburden and interburden removal. On the production side, the problems are decreased dragfine efficiency in chopdown operations, the general need for spoil rehandle, complications in sequencing stripping and coal handling operations, and potential stability problems in highly stacked spoil. Many variations of dragline methods have been reported in the literature to encounter these problems. Because of the physical properties and peculiar hydrology of sub-arctic region mining of multiple seams in such areas probably could not be done with the methods used in temperate regions.The properties of thawed material would make spoil hard to place in a stable manner and thus would influence the mini sequence. For instance, multiple seam mining which requires some rehandling of spoil and prolonged exposure of overburden and interburden material might be precluded by the instability of thawed spoil and therefore mining techniques have to be modified. Since the deployment and operation of a dragline in modes different from conventional schemes will affect productivity, it will be necessary to study the effects on production of changing the dragfine operational schemes. This paper presents a heuristic simulation model of multi-seam dragline operation of a sub-arctic mine that can be used to analyze the handling of overburden and detailed study of the dragfine performance."

Jan 1, 1986

By L. Gawlik

Since the beginning of the 20th century, coal has been the world?s main source of primary energy. In the last few decades, consumption of coal has gradually decreased in some European countries and elsewhere due to the introduction of other energy sources. Regardless, industry continues to use solid fuels for energy production despite of their association with carbon dioxide emissions (about 7 billion Mg). For global development going forward, it is important to estimate what level of energy consumption can be expected as far into the future as the next few decades. To answer this question, specialized global institutions such as the International Energy Agency, the World Energy Council, the World Coal Institute, the U.S. Energy Information Administration, the International Institute for Applied Systems Analysis, as well as oil companies (BP, Shell), conduct periodic forecasts of world energy consumption. The development of such forecasts is very complex because their reliability is influenced by many factors that are difficult to estimate, such as economic development, population growth, climate change, and public awareness. We are all aware that the global demand for electricity will rise significantly in the coming years as a result of anticipated population growth, industrial development, rising living standards, and the general development of civilization. The world?s mineable resources in 2010 were as follows: coal 665.6 million Mg, brown coal 195.4 billion Mg, oil 163 million Mg, and natural gas 185.5 billion m3. The annual global primary energy demand in 2008 was more than 12 billion toe (12,267 Mtoe). In 2006, electricity production in the world amounted to 18,921 TW?h. The structure of the primary energy mix in TW?h (2006) was as follows: coal 41.0%; natural gas 20.1%; nuclear fuel 14.8%; hydro energy 16.0%; liquid fuels 5.8%; and other renewable energy sources 2.3%. The European Union (EU) is one of the largest coal consumers in the world. In 2010, the EU-27 produced 396.1 million Mg of brown coal, and 132.9 million Mg of hard coal; 188 million Mg of coal was imported from outside the EU. The largest hard coal producers in the EU-27 are Poland, Great Britain, Germany, the Czech Republic, and Spain; major brown coal producers are Germany, Greece, Poland, the Czech Republic, and Hungary. For many years, the Polish energy sector has been based on domestic fuel sources ? hard coal and brown coal. The characteristic feature of the Polish balance of primary energy resources is a very high share of coal ? much higher than the world average. Pursuing the decarbonisation of the Polish economy may jeopardize Poland?s energy security, leading to a significant increase in electricity prices, which would hamper the country?s economic development. Price volatility and supply uncertainty are now the dominant features of the international markets for oil and natural gas. The high share of these fuels in meeting energy needs is the reason for unrest in many countries, including those in the EU. Under these circumstances, coal may become the stabilizing element of EU energy security.

Aug 1, 2013

By C. O. Aksoy, H. Kose, K. Heasley, E. Yalçin

"In Turkey, the growing demand for lignite has resulted in increased lignite production and an emphasis on improving underground recovery. This has resulted in a gradual increase in the application of the retreat longwall mining method and also in the extraction of the safety pillars protecting permanent underground structures (drifts, shafts) in mines prior to their abandonment.Extracting these safety pillars presents a special hazard to mine employees and the stability of the mine. Often subjected to high stresses, the behaviour of these pillars is not always predictable. Special care must be taken to ensure that infrastructure does not collapse prematurely, and that working conditions remain safe. Otherwise the extraction must be halted, and the remaining coal lost.This investigation reports on a study of the stability of safety pillars during the final extraction phase of the Hustas mine in Soma, Turkey.” The model construction was based on mine plans, and material properties were derived from physical properties testing. Observed subsidence effects from other mining events were used to calibrate the overburden lamination thickness.The model results compared well with surface physical disturbance occurring as a result of mining, as well as with conventional longwall stress redistribution theory and underground observations. The study has shown that properly calibrated models can be useful in assessing mine safety during remnant pillar extraction. The LAMODEL results demonstrate the convenience of this easy to use software."

Jan 1, 2004

By J. C. Botham, T. D. Brown

"Coke is the most costly item in steelmaking via blast furnaces . Recent innovations in cokemaking have been directed toward reducing this cost while simultaneously improving coke quality and expanding the range of coals used in the process. It is also important to meet increasingly stringent environmental legislation.Improvements in coke quality have been achieved by novel blend selection procedures, by charge density control using both selective pulverization and partial briquetting, and by the use of modifying additives.The Canadian Carbonization Research Association provides a focus for Canadian cokemakin g research which has demonstrated these technologies in a series of pilot-scale experiments."

Jan 1, 1980

By P. J. Poirier, J. A. Meech, H. Raabe

"An Expert System has been implemented to assist operators in applying knowledge about froth conditions in the control of the flotation circuit at Highland Valley Copper. For some time, the personnel at Highland Valley Copper have recognized that froth type is a useful indicator of good operating conditions. However, the operating strategy based on froth type recognition is an ad-hoc skill in which different operators use a variety of terms, features and procedures to identify and solve problems. The first phase of this project developed an on-line consultative system to advise and tutor so that the diffuse expertise could be rationalized and consolidated into a standardized format.The second phase has brought this knowledge into a real-time environment to advise the operators on the floor in identifying froth types and troubleshooting corrective action. This paper describes the steps taken to acquire the knowledge, to design the required system features and to implement the real-time version of this system.INTRODUCTIONThe use of expert systems in the mineral industry has been gaining popularity in recent years. Minnova Inc, Les Mines Selbaie, Wabush Mines, Potash Corporation of Saskatchewan are just a few examples of Canadian mining companies that use expert systems to monitor or control their plants. Applications in the field of flotation include Brenda Mines (Edwards, 1992), Mt Isa Mines Ltd (Lacouture et al, 1991), Outokumpu (Karhu, 1989) and Kidd Creek (Burrows et al., 1989).Expert systems are defined as ""computer systems that apply reasoning methodologies on knowledge in a specific domain in order to render advice or recommendations much like a human expert"" (Turban, 1988). The main areas of application are diagnosis, training, process monitoring and control, and design. There are basically two main types of expert systems: Consultative systems, which are off-line applications in diagnosis and design, and on-line realtime systems, used for supervisory process control and real-time advising."

Jan 1, 1993

By Herbert D. Drechsler

"THE FOLLOWING are some comments on the article, ""International Trade in Minerals and Economic Development"", by M. Sengupta, published in the October 1976 issue of the CIM Bulletin.Sengupta says in the introduction that ""The mechanism through which this growth (economic development) has occurred is basic ally straight forward"". His statement is quite misleading and perhaps it is better to quote Gerald Meier:""Development economists must operate in an imperfect second-best world, away from the simplified premises of neoclassical economics. Their subject matter is therefore not yet a coherent or self-contained discipline. Denied recourse to a set of general principles, perhaps the student's most sensible introduction to economic development is through a study of 'leading issues' that are at the time a major preoccupation of the development economist and development practitioner"" .Sengupta quotes an authority who wrote 18 years ago. Academic and operating development economists today know full well that existing theory is quite deficient. Sociologists, political scientists and engineers in this field also know that economic, social, political and technical development involves all academic disciplines.Sengupta indicates that tariffs in developed countries prevent less developed countries from supplying refined metal, or manufactured and semi-manufactured products. He lists Zambia, Chile and Zaire as examples of copper concentrate exporters, as inadequately shown in Table 1. He is wrong."

Jan 1, 1977

By O. Benavente, M. C. Hernández

Selenium is obtained mainly from copper anode slimes, which is a by-product of the copper electrorefining process. Selenium is present in copper anode slimes as silver and copper selenides. Traditionally, selenium has been obtained by pyrometallurgical processes; however, hydrometallurgy has now been incorporated either full or partial to the conventional process. Some hydrometallurgical processes are been developed and used at laboratory level an industrial scale. This document describes theoretical background and results of characterization and dissolution of selenium from a decopperized anode slimes in an alkaline oxidizing system. The results have indicated that the oxidizing leaching process reaches a practically complete dissolution of selenium (up to 90 %); the undissolved portion is due to the generation of a AgCl around the particle surfaces that delays the progression of the reaction. The results indicated that 90% of selenium extraction can be obtained by dissolution under moderate conditions of pH, temperature and reagent concentration in oxidizing medium. INTRODUCTION Selenium is distributed in the earth's crust in most rocks and soils. Selenium is essential, as it has wide range of applications in the medical and food industries as well as, used in semiconductor, sensors and photochemical devices. Selenium is rarely found in the native state, 90% of selenium is obtained from copper anode slimes, which is a byproduct of the copper electrorefining process (Lu, Chang, Yang, & Xie, 2015; Xiao et al., 2017; Yang et al., 2018). In anode slimes, selenium is present as an intermetallic compound, as Ag-Cu selenides. Currently, selenium is recovered from the anode slimes via hydrometallurgical and pyrometallurgical processes (Lu et al., 2015). The traditional pyrometallurgical method recovers selenium effectively, but faces difficulty as a result of increased energy costs and strict environmental regulations associated with the process (Li, Yang, Jin, Chen, & Tong, 2017). Therefore, hydrometallurgical processes are proposed in oxidizing medium such as nitric acid, alkaline leaching with sodium nitrate, wet chlorination and pressure leaching, amongst others (Hait, Jana, & Sanyal, 2012; Kim & Wang, 2010; Xiao et al., 2017; Yang et al., 2018).

Jan 1, 2019

By Reis. E., P. Pino Véliz

"Along the process of defining the fundamentals of a ferronickel project, several questions require proper answers from the very beginning such as the size and characteristics of the laterite deposit (oxide or silicate), the mineralogical variability, and the selection of the most valuable process route. In general, these elements will be defined along the progress of the exploration and feasibility studies, and definitive engineering. Also, from the very preliminary estimates, three questions are very common: what should be the plant capacity (annual tonnes of contained nickel), what will be the probable capital required (CAPEX), and what will be the estimated timeline (schedule) between the initial stage, say the feasibility study and the plant start-up and ramp-up to designed capacity. The accuracy of the capital cost estimates also progresses along the different stages of development from ±50% at the Preliminary Economic Assessment (PEA) stage down to ±5% for the Detailed Engineering and Construction stage. These accuracies of estimates have been, in some ways, accepted by the mining community and investors. The industry accepted benchmark for ferronickel projects in terms of CAPEX are then in the order of US$50,000 per tonne of nickel contained in the FeNi product. In this paper, the authors analyze in some details three ferronickel projects for lateritic ores that have selected the Rotary Kiln - Electric Furnace (RKEF) as the suitable technological route and have started production in the period 2006–2016. Some key aspects of the ferronickel projects are examined: 1) size and type of deposit; 2) flowsheet selection; 3) evolution of capital cost as a function of capacity from the feasibility stage to construction; 4) comparison between planned production scale and actual ramp up; 5) estimated capital expenditure (CAPEX) compared with actual figures; 6) nickel price evolution and timing of the approval for the project to proceed to construction and production start-up. The objective of this paper is to identify key elements that should be addressed in future projects and that are proposed as benchmark figures for similar projects."

Jan 1, 2017

By Anna M. Ferrero

Stability condition of underground excavations have to be assessed to guarantee safe operations within the quarrying working areas. This objective requires a reliable assessment of the rock mass natural state of stress and of the stress redistribution induced by the excavations. This goal is often complicated by difficult geological conditions induced by tectonic stresses, complex topographies and large and irregular excavation geometries. Consequently, the acting state of stress needs to be measured by specific in situ measurement devices. This work refers on an in situ measurements campaign carried out by CSIRO tests in an underground quarry located in the Carrara marble basin. The difficult path carried out for interpretation of the measurements is described in this paper. In particular, the numerical modeling performed using the Boundary Element Method (BEM) first, to study the influence of both surface topography and excavation geometry and then the Distinct Element Method (DEM) to evaluate the influence of rock discontinuities in the measurement zone are illustrated in this work. Parametrical analysis of the rock mass mechanical features is also described in order to calibrate the numerical models and analyze the experimental results. The work has been carried out trough several phases, which are: characterization of the rock mass through geostructural surveys: this allowed us to classify the rock mass and determine the mechanical and physical parameters necessary for modeling; on-site measurement of stress levels through the application of over coring techniques; numerical analyses for the simulation of excavation phases, using the Examine3D (BEM) engineering analysis code. comparison between the measured stress levels and those numerically calculated and subsequent calibration of the BEM model; Numerical model of the forecasted excavation based on the calibrated (BEM) model.

May 1, 2009

By Amin Jafari

Macrosegregation has always been an important issue with the solidification processes, particularly in Direct-Chill Casting of Aluminum alloys, where uneven properties, surface and bulk defects and limitations in productivity can be arisen due to macrosegregation in the cast product. Following the global attempts to practically predict the macrosegregation, in the present work, a numerical model was developed based on an industrial scale DC casting process to simulate the solidification and macrosegregation in an Al-4.5%Cu billet. Interesting aspects of this investigation are concerned with an efficient numerical scheme to keep simplicity, consistency and desired physical resolution of the solidification phenomena together. In the mathematical model, coupled conservation equations of mass, momentum, energy and species were solved numerically using finite volume method. A different numerical scheme, called SIMTLE, was introduced to link the energy and species equations with the phase diagram of the alloy. Calculations were performed on an industrial case and obtained results were compared to available experimental data to assure the performance of the model. Different macrosegregation features were predicted and discussed on the solidifying Al-alloy billet.

Oct 1, 2011

By J. P. Harrison, G. F. Gambino

"This paper examines unpredictability in the parameters governing hydraulic fracturing (HF) as used in stress amelioration for underground excavations, with the aim of showing how this unpredictability may affect design decisions. Using uncertainty models that are appropriate to particular levels of information and degrees of uncertainty, this paper demonstrates how these can aid in decision-making related to feasibility assessments of HF arrays for stress amelioration.Cave mining operations produce large underground voids and high stress concentrations around critical mine locations. These stress concentrations increase the potential for rock burst events. Although de-stress blasting has a long history for redistributing high stress concentrations, to improve safety and reliability HF is now being trialled as an alternative.Unfortunately the HF process is extremely uncertain, and so predicting fracture propagation geometry is difficult. Although the major parameters governing HF propagation have been previously identified, no indication has been given regarding the contribution that uncertainty in these makes to unpredictability in the overall HF system. Using simplified models of HF and referencing a recently proposed characterization of unpredictability, we relate unpredictability in the various governing parameters to the effect it has on strain energy density (SED) in the surrounding rock. Within these models we analyse SED as well as the stress intensity factor (KIc) when investigating the effect of parameter uncertainty and its influence on various crack propagation criteria (Sih & Macdonald, 1974). These models are applicable to unpredictability associated with the development of new fractures; the case of pre-existing fractures is the subject of on-going work.The paper will assess in greater detail the various governing parameters, and investigate the appropriate use of other uncertainty models. As a result, we will show how assessment of uncertainty in HF parameters can be used to both guide feasibility studies and determine the optimal allocation of resources to improve the final design."

Jan 1, 2015

By Ross Dimmock

The productivity of a mine has the same goals as the quest to complete a tunnel project both safely and within time. A key aspect to achieving this goal is to excavate and support the working face as quickly as possible, allowing early re-entry to start construction of the next advance in safety. As with tunnels, the use of high performance wet-mix sprayed concrete has increased in mines dramatically over the last few years, and year on year has seen a stepwise increase in shotcrete performance, particularly in the first few hours. Shotcrete early age strength development clearly offers mining teams enormous advantages by allowing early, safe re-entry to the face. This paper illustrates that in the hard rock tunnelling field, modern shotcrete approaches do not cause delays in re-entry, but allow a continuous construction cycle. Furthermore, the paper identifies the most suitable, up-to-date shotcrete admixture and equipment technology available to the mining community to permit early re-entry.

May 1, 2003

By A. G. Pronk, D. M. Burton

"A regional till sampling program in the Upsalquitch Forks-Tetagouche Lakes area, centred some 70km west of the city of Bathurst, has proven an effective method for gold exploration in the heavily glaciated interior of northern New Brunswick. Prospecting activities within this area over the past three years, have led to the discovery of several gold occurences associated with quartz-carbonate alteration in a variety of intrusive rock types emplaced along major fault zonesQuaternary mapping shows that the glacial history is complex. However, the displacement of material is uniform in distance and direction, and the till is generally thin (0.5 m to 2.0 m) and locally derived, making the interpretation of till geochemical patterns relatively simple for the explorationist. Previous studies have shown the the fin e-grained gold is best detected in the -250 mesh (-0.063 mm) till fraction (clay plus silt) and that the C-horizon is the preferred medium for analyses.Samples were collected on a 2 km grid and analyzed f or Cu, Pb, Zn, Au, Ag, As, Sb, Mn, Fe, Ni, Co, and Cd. Results indicate that concentrations of 10 to 20 ppb Au can effectively delineate areas of anomalous gold in bedrock associated with fault structures, and that a good potential for discoveries exists to the west of the known occurrences, where up to 678 ppb A u has been detected in tills. IntroductionThis paper reports on the result s of surficial geological investigations conducted over the past two field seasons in north-central New Brunswick. The stud y area is located in the Upsalquitch Forks-Tetagouche Lakes map area s (N.T.S. 21 0 19 and 21 0 (10) 70 km west of the city of Bathurst (Fig. I). The area is situated on the margin of the New Brunswick Highlands and has a maximum elevation of 640 m (for a detailed description of the physiography, see Rampton et al. 1984).Historically, exploration in northern New Brunswick has concentrated on base metals within the Cambro-Ordovician Tetagouche Group, resulting in the discovery of man y significant massive sulphide deposits (Brunswick No.6 and No. 12, Heath Steele, Caribou, Armstrong Brook, Orvan Brook, McMaster, Murray Brook, and Restigouche). Auriferous base metal occurrences along the Rocky Brook-Millstream Fault have also been previously investigated."

Jan 1, 1988

By F. S. Su, P. Z. Pan, X. T. Feng, F. Yan, W. W. Ji

"This paper aims to simulate the spalling failure behavior in hard rock based on a self-developed numerical model, i.e. a rock discontinuous cellular automaton (RDCA). A crack initiation and propagation criterion is proposed based on the plastic strain, which is used to link the continuity and discontinuity during the failure process. The discontinuities of rock, such as cracks and other internal boundaries, are represented by discontinuous displacement functions, i.e. tip enrichment and step enrichment. The partition of unity is used to improve integral precision of the elements intersected internal boundaries, which is traced by a level set method. Arbitrary crack geometries can be conveniently represented and it does not require any remeshing in the modeling of crack initiation, propagation and coalescence. Numerical modeling of excavation in hard rock using RDCA is conducted. The spalling failure process of hard rock induced by excavation is well simulated. The depth and shape of hard rock spalling failure are good agreement with in situ observation.INTRODUCTIONThe excavation in rock mass is more and more popular. At the same time, the disasters, such as rock burst, rock spalling and falling etc, induced by excavation are quite prominent. Numerical modeling is an important way to help us understand the failure mechanism of rocks. Many numerical methods have been used to simulate the excavation of rock mass. For example, the finite element method (FEM) (Karakus and Fowell, 2003), the discrete element method (DEM)(Cundall and Strack, 1979, Labra et al., 2008), Finite difference method (FDM)(Zhu et al., 2009), Element Free Galerkin Method (Belytschko et al., 1994), Discontinuous displacement analysis (DDA) (Shi, 1988) and Boundary element method (BEM) (Katsikadelis, 2002, Chen and Hong, 1992) are commonly found in the stability analysis of excavation in rocks. In the modeling of crack propagation or excavation, most of these methods are tedious since the internal boundaries have to be consistent with the element boundaries. And in many cases, the remesh has to be conducted. In recent years, people are interested in particular types of FEMs, such as the extended finite-element method (XFEM), the particle discretization scheme finite-element method(PDS-FEM(Hori et al., 2005, Oguni et al., 2009)), the combined finite-discrete element method (FEM/DEM) (Munjiza and Wiley, 2004, Cai, 2008) and spectral-element method(Gharti et al., 2012) etc."

Jan 1, 2015

By Yoginder P. Chugh

This paper discusses design of sprays systems for dust control around a continuous miner (CM) in about 4.2 m (14 ft.) high mining areas with about 1.0 m to 2.0 m (3-6 ft.) of out-of-seam dilution mining. The challenges included low air volumes and velocity at the end of the line curtain, dust produced from out-of-seam dilution rock being very fine with 50% of the particles less than 10 micron, poor capture of aerosol through scrubber suction inlets, dust escaping through the sides of the loading pan in mining high areas, overloading of dust-laden air in the wet-scrubber, and dust rollback toward workers. The challenges were resolved through CFD modeling of airflows; improved line curtain installation, redesign and varying the spatial locations of spray systems as compared to low mining height areas. Water sprays on CM is the primary engineering control for dust control in coal mining. In 2010, the authors developed several spray system concepts for dust control (Chugh, Patwardhan, Gurley, & Hirschi (2009), Chugh & Gurley (2009), Chugh 2012). These included increased contact time between dust particles and water droplets, improved potential for the dust aerosol to be sucked in through suction inlets, and reduced dust-roll back to the operators and workers. CFD modeling was used to understand airflow patterns around mining areas and to identify spatial locations for sprays to minimize dust exposure of CM operator (CMO), haulage unit operator (HUO), and workers downwind of the operating CM in the last open crosscut (LOXC). Face area ventilation plays a key role in dilution and removal of dust generated by mining operations. High mining heights and large pillar sizes associated with longwall mining reduce the air volume reaching the face area to achieve good dust dilution.

Aug 1, 2013

By A. Uribe-Salas, J. A. Finch, B. J. Huls

Froth depth or interface level is an important control variable in column flotation which can influence both grade and recovery. A common method of locating the level is based on sensing the hydrostatic pressure at one or more points along the column. The level position is then calculated from these pressure readings using an equation which includes the bulk density in the froth and bubbling zones. The precision with which the level is detected depends on how well these density values represent both zones. The calculation of these bulk densities from theoretical considerations is not possible and, therefore, the practice is to estimate them by calibration. Unfortunately, the calibration parameters often do not report the level with an acceptable accuracy. A portable conductivity probe has been developed to detect the position of the interface from conductance measurements across the interface. The location of the interface corresponds to the position where a large change in conductance is observed, which is primarily a consequence of the difference in gas holdup between the bubbling and froth zones. This probe can be used to detect the position of the interface to an accuracy of± 5 cm. The probe can be used while the column is in operation, which allows the on-line calibration of the level detection system. Results obtained in its application in a pilot-scale column (0.91 min diameter) are described.

Jan 1, 1989

By S. Banisi, J. A. Finch, A. R. Laplante

"A technique for on-line simultaneous estimation of gas and solids holdup (volume fraction), based on a combination of conductivity and pressure difference measurements, is proposed and tested in a laboratory flotation column (10cm in diameter and 447cm in height). Fundamental concepts underlying this technique and the effect of relevant parameters are discussed. In the studied range, 3-30 %v/v gas holdup and 2-18 % v/v solids holdup, experimental results showed good agreement between the estimated and actual holdup values (as determined by an isolating technique). The relative accuracy of the solids holdup estimation increased when solids density or solids concentration increased. Frequent re-calibration of pressure transducers was found necessary for accurate phase holdup estimation.IntroductionGas holdup is a key parameter in controlling the performance of flotation columns. For example, flotation rate is affected by bubble size and gas rate both of which, in turn, affect gas holdup. Moreover, gas holdup also determines the slurry residence time which indicates a direct influence of gas holdup on recovery.Gas holdup determination has been the focus of many studies (e.g., Castillejos, 1986; Marchese et al., 1992). Some of the techniques which have been used are given in Table 1."

Jan 1, 1994

By Dr. G. R. Hoey

"Abrasive wear and corrosive wear of carbon-steel grinding balls occurred simultaneously during the wet-grinding of hematite iron ore, and Ni-Cu sulphide ore, in laboratory ball mills. Two corrosion control methods, the use of corrosion inhibitors and pH control, were investigated and found to be effective means of reducing or preventing corrosive wear. Up to 50 % reduction of total ball wear resulted from the use of these methods.Corrosive wear is caused principally by the reaction of oxygen in air with the carbon-steel grinding balls, probably by the following reaction: 2Fe + O2 + 2H20 - 2Fe2 + 40H-.IntroductionA survey of corrosion problems in Canadian sulphide ore mines was completed and the findings were published in 197l(l). The corrosion survey was used to develop the present research program with the objective to find more economical and effective ways and means to reduce the corrosion that occurs in the mining and metallurgical industry. The purpose of this presentation is to review the projects being done by staff members of the Corrosion Section, Extraction Metallurgy Division, on corrosive wear and its control in wet-grind ball mills.Both abrasion and corrosion contribute to metal consumption during wet grinding of ores. The total wear of grinding media in this study is assumed to be equal to the sum of corrosive wear and abrasive wear. A great deal of research and development has been reported in the literature on ways to improve the abrasion resistance of grinding media but only a small number of studies has been reported on the corrosion resistance of conventional grinding media."

Jan 1, 1974