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To allow routine measuring of the exposure of underground workers to N02 from diesel engines and residual gases from blasting. The Approach: A miniature sampler absorbs NO2 which can be measured using a simple method adaptable to both multiple automatic analyses or individual on-site analysis. How It Works: The NO2 sampler is encased in a plastic tube approximately half the length of an ordinary ball point pen and clipped to an underground worker's hard hat. Removal of the end cap activates the personal sampler. Air from the working place enters the open end and diffuses at a controlled rate down the tube interior. The diffusion rate is dependent on tube dimensions (ratio of cross-sectional area to length). The closed end of the tube contains stainless steel mesh which is coated with triethanolamine (TEA) for absorbtion of all NO2 reaching it. Other oxides of nitrogen are not absorbed. The amount

Jan 1, 1975

By Daudi R. Waryoba

Keywords: Wire Drawing, OFHC Copper, Recrystallization, Orientation imaging Microscopy (OIM), Texture inhomogeneity Textural inhomogeneities have been investigated in oxygen free high conducting (OFHC) copper wire drawn at room temperature to a true strain of 2.31, and isothermally annealed at 250°C and 750°C for annealing times ranging from 10 s to 1 hr. Local orientations were mapped by means of orientation imaging microscopy (OIM). The microtexture of the drawn wires showed a strong <111> + weak <100> duplex fiber texture at the inner core, whereas the mid and surface regions had a comparatively weak texture. Annealing at 250°C resulted into a recrystallization which originated from the mid section, proceed towards the surface regions and ends in the inner core. Recrystallization resulted into a strong<100>+weak<111> duplex fiber texture. A similar textural inhomogeneity was observed during short annealing at 750°C. However, prolonged annealing gave rise to abnormal grain-growth that proceed from the inner core to the outer surfaces with a dominant <111> fiber component at the inner region and mixed components of <111>, <100>, and <112> at the outer surfaces.

Jan 1, 2005

The refractory nature of residual gold in Kalgoorlie calcines is caused by occlusion in dense pyrrhotite formed by fusion within pyrite grains during decomposition. Fusion of pyrite increases as the rate of heating exceeds the rate of sulphur expulsion. By controlling these rates in relation to each other in a fluidised system fusion is limited and an expanded structure is formed. The increased area presented to cyanide solution, and the decreased diffusion distance, makes gold more accessible for extraction. Gold extraction from expanded pyrrhotite, before oxidation for porosity, is comparable with extraction from fully oxidised calcines from Edwards roasters. A method is suggested for standardised comparison of cyanidation residues.

Jan 1, 1957

By Roberto Folchi

"This article deals with the excavation of a tunnel below the town of Isola LIRI, nearFrosinone, in central Italy. The tunnel was driven into a conglomerate formation, of lacustrine_fluvial origins, consisting in carbonate clasts with a sandy_silty matrix and calcitic cement. ""Drilling andblasting"" had to be adopted in place of a tunnel boring machine which had showeduneconomical performances. Good advance speed rates were achieved notwithstanding thepresence of some above structures to safeguard. The nearest structure (an old votivechapel) was less than 10 meters (33 ft.) far from the tunnel crown; the nearest residentialstructure was at about 15 m (49 ft.)."

Jan 1, 1993

By Matti Kongas, Kari Saloheimo, Antti Remes

"The paper studies the control performance of the flotation process as a function of the measurement accuracy and sampling frequency of an on-stream XRF analyzer, using a simple dynamic model. An additional aim is to assess how the economical result of a mineral flotation process depends on the quality of process control based on the on-line elemental assays.An on-stream XRF analyzer measures the concentrations of slurry lines in a continuous cycle from several process points. The control performance depends on the analytical accuracy and sampling frequency of the concentration measurement. With a long cycle time, the state of the process changes before a new measurement becomes available. With short measurement times the statistical variance of the counted Xray pulses increases, increasing the random error in the analysis. In addition, the measurement accuracy depends on the concentration of the component to be measured from the slurry.To quantify the effect of analysis error and frequency to process control, a simple dynamic process model is created in the Matlab environment. Data from a copper flotation circuit is used as a test case. The process model comprises a first order reaction equation and the grade-recovery -relationship estimated from process data. The control was modeled using the control strategies implemented into a rule based advanced control system. The economical performance of the control was studied by calculating the overall net smelter return at various analyzer parameter combinations."

Jan 1, 2003

By Jelke Dijkstra

This paper presents the results of model pile load tests in a photoelastic material. The soil in this test is represented by an assembly of photoelastically sensitive glass particles, which allows for optical measurements of stresses. In the same test setup, displacements around the pile are measured using digital image correlation (DIC). During the pile installation stresses and strains are recorded. Tests were performed in loose and medium dense particle assemblies. The development of stresses and strains around the pile tip and pile shaft are quantified and presented in this paper. For the loose conditions the results show a small influence on the stress state. For the medium dense conditions a clear stress change is observed.

Jan 1, 2006

By John H. Johnson

A study of mine air quality was conducted using the latest advanced continuous monitoring instruments. An overview of the various interacting variables in the mine that affect air quality is presented. One effort involves the evaluation of portable instruments, the development of measurement techniques, sample analysis procedures and computer programs for statistical analysis of measurement data, and the application of the instruments and techniques to the measurement of the concentrations of CO, CO2, NO, NO2 and particulate matter in a lead and a copper underground mine. A second effort involves the first application of the Mine Air Monitoring Laboratory (MAML), a mobile trailer containing laboratory type instruments, sampling and data systems for the measurement of CO, CO2, NO, NO2 and particulate matter. The data from the MAML for blasting and for operating diesel equipment are analyzed and presented in various plots.

Jan 1, 1977

By M. Massinaei, S. Abasi, M. Oliazadeh

Reliable measurement and control of the pulp-froth interface (froth depth) in the flotation columns is critical to achieve the desired metallurgical performance. Shallow froths result in a reduction of grade because of particle entrainment and deep froths reduce recovery because of the drop back of entrained and weak hydrophobic particles to the pulp zone. The cleaner circuit at Miduk copper concentrator consists of three parallel MicrocelTM flotation columns 4 m in diameter and 12 m in height. The interface level of the flotation columns is measured by two pressure sensors located at 1.4 and 2.4 m from the cell lip (in the collection zone). In this study the performance of the level detection system at different operating conditions was evaluated. A calibrated float-ultrasonic location system was used for measuring the actual froth depth. The results indicated that the existing level control system was subject to considerable error. The absolute error was found to be 33.27 cm. This was mainly attributed to the constant set-point value assigned to the froth density (ρf=0.3 g/cm3), which actually varies with the operating conditions. The actual froth density at different conditions was calculated and its average value (ρf=0.12 g/cm3) was re-set in the control system. This resulted in substantial reduction in the level-detecting error. Recommendations for more accurate measurement of the interface level were presented. INTRODUCTION Froth flotation is a complicated process because of many involved variables. One of the most significant controlled variables in the flotation process is the pulp-froth interface (froth depth). The froth depth has a profound influence on the metallurgical performance parameters (i.e. grade and recovery). Shallow froths result in grade reduction because of particle entrainment and deep froths reduce recovery resulted from the drop back of entrained and weak hydrophobic particles to the pulp zone (Finch and Dobby, 1990). Various techniques have been developed for measuring the interface level of the flotation cells in the last few decades. These techniques can be classified as: Techniques based on hydrostatic pressure measurements (Finch & Dobby, 1990), Techniques based on the density gradient (float) (Moys & Finch, 1988), Techniques based on conductivity measurements (Uribe-Salas, 1991), Techniques based on temperature measurements (Moys & Finch, 1989).

Jan 1, 2019

By R E. Myers, G N. Phillips

Many of the worldÆs larger iron ore deposits are hosted by rock sequences of Archaean to early Proterozoic age. Most models for the genesis of these deposits are influenced, either directly or indirectly, by the nature of the atmosphere at the time of their formation, and more specifically by the presence or absence of oxygen in the early atmosphere. Since the early-1950s, the geological literature suggests that the Archaean atmosphere was æreducingÆ, and that it may not have contained significant amounts of free oxygen until ca 2 Ga. There are many different definitions of the term æreducingÆ, but the criterion adopted here is whether crustal iron was limited to Fe2+, or whether Fe3+ was also widespread, ie was there scope for redox changes in the state of iron? Significantly, major Australian banded iron formations span this period of inferred atmosphere transition, eg Mt Goldsworthy, Mt Tom Price, Middleback Ranges. Geological evidence for a reducing Archaean atmosphere is both ambiguous and controversial (see review by Phillips, Law and Myers, 2001). Many earlier ideas (eg no Archaean redbeds; all very large iron ore deposits being post-Archaean) have been disproved by dating, whereas other evidence (eg homogeneous detrital gold grains, inferred palaeosols) has not withstood geological scrutiny. The interpretation of some data sets (eg inferred detrital uraninite and pyrite in some Archaean meta-sedimentary rocks) is still controversial. In fact, some lines of evidence now suggest that oxygen was present in the atmosphere well before 2.5 Ga (eg sulfates in the Pilbara craton, carbon distribution in clastic sedimentary rocks). An oxidising Archaean atmosphere has important implications for the development of iron formations. First, the atmosphere is an obvious potential source of oxygen to stabilise ferric iron minerals. Second, reduced fluids in equilibrium with ferrous iron are commonly inferred to transport iron in solution to the depositional site. The redox state of the atmosphere thus provides critical constraints on the solution chemistry of surface waters, effective transport paths for iron and particularly on viable precipitation mechanisms. Iron formations developed from fluids in equilibrium with the atmosphere also have the potential to provide important constraints on the evolution of EarthÆs early atmosphere. If an oxygenated atmosphere is a necessary condition for the development of iron formations, then the Archaean atmosphere must have been oxidising since at least 3.5 Ga. If the redox state of the atmosphere is not a necessary condition, then the time distribution of iron formations cannot be used to provide constraints on atmospheric evolution. Given these uncertainties, models for the genesis of iron ore deposits of Archaean or early Proterozoic age should not rely on a reducing atmosphere in the absence of independent evidence and the alternative of an oxidising atmosphere should also be considered.

Jan 1, 2002

By I. L. Follington

This paper describes the research and development programme to develop a prototype underground auger mining system aimed at developing and demonstrating an underground auger mining system able to provide economic access to thinner (<1.8 m) coal reserves of South Africa. Data concerning the performance of modern coal augers under South African coal mining conditions were gained from a proven surface auger which operated across a range of coal types. These data were analysed and considered in conjunction with historical information regarding previous attempts at building underground augers dating back to the 1950s. Drawing on these data a prototype underground auger mining system, the BryDet BUA 600 underground coal recovery auger, was designed and manufactured by the BryDet Development Corporation in collaboration with Eskom and Cutting Edge Technology Pty Ltd with support from Anglo Coal and the Ingwe Coal Corporation Ltd. The prototype BryDet BUA 600 underground coal recovery auger commenced trials in March 2000 at the Matla Mine near Witbank in South Africa. The initial trials were undertaken in an open cut to facilitate the commissioning and training associated with a prototype mining machine. A total of 30 holes was augered in the box cut before the machine moved underground. The prototype BUA 600 first achieved the target penetration depth of 80 m in its third hole. The prototype BUA 600 is a new underground mining system which has passed early testing with ?flying colours? and could provide access to extensive underground coal reserves unmineable by conventional mining techniques both in South Africa and elsewhere around the world.

Jan 1, 2001

By Met M, Worner H. K

In pursuance of the investigation into the influence of various elements on the properties of lead during the past year, the effect of several elements on the creep rate of commercially pure lead has been investigated; a standard initial stress of 500 lb. per sq. in. having been adopted for comparison purposes. Other work which has been carried out indicates that the relative results of creep tests may be altered by varying the applied stress, but this aspect of the problem will need to await further investigations for itscomplete elucidation. The results obtained with dilute tellurium alloys are considered sufficiently interesting, and in some respects are so extraordinary, as to warrant publicatiorr at this stage.n must be realised however that, since the results obtained appear to be at variance with those said to have been obtained in practice and those previously published, the present investigation can only be considered as a contribution to our knowledge of the general problem.Consequently it is not considered advisable or necessary to offer detailed explanation of the results given. In fact, some features of the tests about to be described will need further investigation before an adequate explanation is possible.

Jan 1, 1936

By P. Huang, D. W. Fuerstenau

Various factors that control the natural flotability of talc, including differences due to crystal face and edge effects, were delineated. For study of talc depression phenomena, dextrin was used as a model depressant. For the enhancement of talc flotation, dodecylammonium acetate (DDAA) was used as the collector. The interaction of DDAA with talc was assessed by flotation experiments and electrokinetic (zeta potential) measurements, from which the role of hydrophobic bonding can be demonstrated. The results presented in this paper provide useful information on how the crystal chemistry and surface chemistry control the electrical double layer, adsorption phenomena, wettability, and flotation behavior of talc in aqueous media.

Jan 1, 2003

By W. D. Dietzman

This Bureau of Mines report presents a continuation of statistics pertaining to distribution of petroleum reservoirs (or fields), wells, and production by depth and producing rate classification in the United States. These statistics show the change that has occurred since results of a similar study were published by the Bureau of Mines in 1967. Data are presented in tabular form by State for the 18 principal oil-producing States and by subdivision for the two largest oil-producing States, Texas and Louisiana. Tabular summations and graphical illustrations are presented for the Nation. The data are classified by 4-barrel-of-oil-per-day rate increments up to 36 barrels and one increment of greater than 36 barrels of oil per day and by 2,000-foot depth increments up to 8,000 feet and one depth increment of greater than 8,000 feet. The overall average producing rates for States and the Nation have been published for many years, and although such rates are useful, they are very general descriptions of producibility. A breakdown of production, wells, and reservoirs by various depths and rates and by State or by State subdivision provides a more detailed description of producibility.

Jan 1, 1975

By Bernard Baum

Combined preservative/fire retardant systems were pressure impregnated into Douglas fir and Ponderosa pine samples and evaluated for decay, flammability, and mechanical properties. The objective of the evaluation was to identify cost-effective systems for use with mine timber, and to provide an information and data base from which Federal code regulations could be established. Thirty systems, based on combinations of commercially available preservatives and fire retardant impregnants and coatings, were applied to Douglas fir samples and evaluated for decay and flammability. The ten most promising systems were ap¬plied to both fir and pine and reevaluated for decay and flammability before and after water leaching. The five best systems were given a thorough laboratory evaluation using both pine and fir. Evaluations included flame spread, smoke density, toxic gases, decay, compressive strength, flammability after artificial weathering, and cost. All systems had acceptable toxic gas levels and smoke densities, but flame spread was only borderline acceptable for most of the samples tested. A trade-off analysis showed Acid Copper Chromate/Fyrprufe with Albi-107A/144 intumescent paint and Koppers NCX to be the-best systems. Recommendations are made for further large-scale testing using the two best Systems.

Jan 1, 1978

By Arthur V. Petty

In Bureau of Mines research on recycling chrome-containing refractory wastes, used refractories from argon-oxygen decarburization and electric steelmaking furnaces were beneficiated. By means of dry magnetic separation on minus 6-mesh crushed wastes, a concentrate was produced. After minor adjustments to the particle size distribution, full-size refractory brick were dry-pressed by a commercial producer and fired to 1,450° and 1,730° C. Standard testing procedures were used to determine the cold-crushing strength, modulus of rupture at 25°, 1,300°, and 1,500° C, hot load, thermal shock resistance, thermal expansion, and slag resistance. Optical and electron microscopy were used to determine grain-bonding mechanisms, and energy-dispersive analysis of X-rays was used to determine elemental distribution. The test results indicate that the beneficiated material could be used to produce a refractory product suitable for moderate-temperature applications.

Jan 1, 1982

By K. J. R. Ford

"Significant advances in mining and metallurgical operations have occurred over the last two decades, to define ore bodies via geological mapping, mineralogical analyses, geostatistical models and resource reserve modeling. Metallurgical process measurement, controls and modeling have also significantly progressed, with advanced instrumentation, control software, data capture systems and simulation tools. This progress together with development of the science of geometallurgy has allowed geologists, mineralogists, miners and metallurgists to start working together to define geometallurgical ore units and link these to mine planning and projected metallurgical performance. However, application of full geometallurgical programs into existing mine-processing operations or into new “greenfield” projects has been slow. This is mainly due to higher costs, limited dedicated technical resources and little or no corporate leadership. Additionally, life-of-mine cash flow models, the “dollars”, have been largely driven by ore tonnage rates, pay-metal grades and fixed pay-metal percentage recoveries, with few or no geometallurgical parameters included.Here defined, the “electrons” represent intrinsic ore characteristics embracing chemical composition, mineralogy, gangue components and their associated fundamental metallurgical processing phenomena. With its ever expanding treasure chest of measurement and modeling tools, geometallurgy paints a much clearer picture of the “electrons” for the geologist and metallurgist. But to fully understand and realize the real net value of ores over the life of a mine, a comprehensive link of “electrons to the dollars” is essential. Intrinsic characteristics of geometallurgical ore units are by definition linked to their metallurgical processing, but importantly need also to be related to operating costs, capital requirements and revenue.This paper discusses this important linkage under topics of ore geology and mineralogy, metallurgical processing, waste disposal, environmental issues, metal refining, project engineering and lifeof- mine models. Topics are illustrated by multi-metal references and by case examples from gold ore heap leaching and manganese ore smelting projects. 1"

Jan 1, 2013

By Wesley Schmutzler

The Deep Mixing Method (DMM) was employed to raise and support the LPV (Lake Pontchartrain and Vicinity) -111 Levee in New Orleans. Even using innovative technologies, the tight schedule to achieve the 100 year elevation by June 1, 2011 was a daunting endeavor. The size and scope of DMM proposed for LPV-111 was on a scale never attempted outside of Japan. Over 1.65 million cubic yards of DMM was installed. LPV-111 is adjacent to the Bayou Sauvage Wildlife Refuge, which is the largest urban National Wildlife refuge in the United States. By utilizing DMM to control settlement and improve stability of the taller levee, side slopes were steepened from the conventional 1V:4H to 1V:2.85H, thus avoiding encroachment into the Bayou Sauvage and reducing the amount of clay needed for the completed levee. The COE utilized Early Contractor Involvement (ECI) for this contract. The ECI process allowed for input from the DMM contractor, TREVIICOS South, in order to optimize equipment resources and material requirements. This paper gives an overview of the extensive DMM requirements for LPV-111 and explains the benefits of the ECI process.

By I. Mc Dougall

Finite element models were generated of two submerged arc furnaces of different geometries. A 48MW circular furnace and a 68MW 6-in-line rectangular furnace were studied. The electrodes, raw material, slag and molten metal were included in the model. ANSYS/Multiphysics was used to predict the current density distribution in the electrodes, raw material, slag and molten metal as a result of the three phase AC current. The effect of the electrode immersion on the current path was studied. The ?proximity effect? caused a pronounced asymmetry in the electrode currents in the circular furnace, whilst the electrode currents in the rectangular furnace exhibited radial symmetry. The current distribution in the melt in both furnaces indicated that the bulk of the current flows between phases. The current density is greatest between electrodes. Results were compared to qualitatively similar published work, operating experience and results of furnace dig-outs.

Jan 1, 2007

By Francesco Vegliò, Luigi Toro, Francesca Pagnanelli

"Different hydrometallurgical processes have been studied in order to recover manganese(II) from oxidised minerals such as MnO2 (Vegliò and Toro, 1994). An innovative acid reductive leaching carried out in soft experimental conditions was here considered using agro-industrial wastes containing carbohydrates as reducing agents (Vegliò et al., 1998).The leaching process was investigated from a kinetic and equilibrium point of view in order to optimize the experimental conditions and obtain high purity and concentrated MnSO4 solutions.The overall leaching process (not considering the complex network of intermediate oxidation reactions of the carbohydrates in hot sulphuric acid medium (Vegliò and Toro, 1994)) can be described by the following reaction:24 MnO2 + C12H22O11 + 48 H 24 Mn2+ + 12 CO2 + 35 H2O (1)A Shrinking Core Model (SCM) was modified by a variable activation energy term to take into account both the variable reagent concentrations and the reaction rate change with respect to the manganese dioxide conversion. The influence of the particle size in the kinetic model is discussed with the support of SEM analysis and BET surface measurements before and after leaching.Manganese extraction yield was maximised (170-190 g/L) using appropriate carbohydrates and acid excesses, while impurity concentrations were kept low (Fe<10ppm and Ca<300ppm) pre-treating the ores, using hydroalcoholic leaching medium and different combinations of down-stream processes. In particular precipitation, solvent extraction and adsorption onto active carbon were tested to eliminate Fe and Ca from MnSO4 solutions."

Jan 1, 2003

By M Eggers, H Baxter

This paper discusses the geotechnical condition of bedding shears and small- and large-scale faults and shears in Archean banded iron formation (BIF) bedrock, based on observations of core and televiewer images. Information that can be collected includes the orientation of defects, infill thickness, strength and material type, defect shape and surface roughness.The spacing and continuity of bedding shears may be critical to slope design where performance is structurally controlled with bedding dipping out of a wall. The intensity of development of the bedding shear is a useful indicator of the amount of shearing a bedding surface has been subjected to. This can allow for engineering judgement to be used in adopting peak or residual shear strengths along defect surfaces when developing the design.The spacing and continuity of bedding shears may also contribute to the blockiness and degradation of a rock mass where the structural orientation is otherwise favourable. Additionally the condition, thickness and strength of infill of major fault structures can affect slope design and performance, depending on orientation.Comparison of the condition of structures observed in core with the corresponding in situ televiewer image has been made to assess what characteristics are most accurately captured by each technique and whether the additional information gathered from using the televiewer technique is justified by the cost. The question of whether the data collected by a televiewer is sufficient to ultimately replace the need for core is considered.CITATION:Baxter, H and Eggers, M, 2013. Fault and shear characterisation in archean banded iron formation bedrock - a comparison between core and televiewer data collection techniques, in Proceedings Iron Ore 2013 , pp 47-56 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013