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In the UK during the 1990s the energy companies had developed a policy of æDash for GasÆ, building large natural gas power stations to produce more than 30 per cent of the UKÆs electricity demand. The price of imported thermal coal was dropping and the electricity generators were putting pressure on the UK coal producers to produce coal at a reduced cost. Imported coal from Columbia, South Africa, America and Australasia had increased their market share in thermal coal sales to over 50 per cent of a 55 Mtpa market. The pressure on the UK coal industry to reduce costs and improve productivity levels from an ever decreasing resource was high. Companies were benchmarking their operations on the imported coal producers and had to realign their organisations, productivity levels and costs to world best practice, not just technically, but in world class organisational management techniques.

Jan 1, 2005

By B. R. MacKay

Introduction Of all Canada's mineral resources, its coal deposits have probably received the most continued attention by the Geological Survey since its inception ninety years ago. A casual review of the many geological maps of coal areas by the Geological Survey will show how geological and topographical detail on the maps has gradually increased to meet the ever urgent demands of the mining industry. In the early stages of exploration, the mapping done, especially in the coalfields of the Rocky mountains, was largely of a reconnaissance nature. On these maps the topographical relief, where shown, is indicated by form lines or by hachures, the boundaries of the coal-bearing formations are only approximately defined, and the geological structure of the coal seams is illustrated by one or more generalized cross-sections. Once mining development on a coal area began, there arose a demand for more detailed maps. To meet this need, topographical and geological maps on a scale of one inch to a mile were made, in which the ?topographical relief is shown by contour lines having generally an interval of 100 or 200feet. On the geological maps, the boundaries of the formations are accurately delineated, and the geological structure of the area is illustrated by one or more structure sections drawn across the area, which show the position and attitude of fault lines, the crests and troughs of folds, and the attitude of the various formations (See maps of Costigan Coal Field, 1905, and Cascade Coal Basin, 1907, by D. B. Dowling).

Jan 1, 1932

By Hans Chr Andersen

Almost every form of iron ore and carbon material has been used as a raw material in the production of pig iron in electric reduction furnaces. Experience derived from the operation of the large 33,000-kva. Tysland-Hole furnaces, however, indicates that production results are very much influenced by the raw material conditions. The author presents the principle pattern of the metallurgical structure of the interior of an electric pig iron furnace. On the basis of this, he discusses the variations of electrical and metallurgical conditions for the process which will take place with changing raw materials. The formation of a coke bed underneath the electrodes, and its influence on the furnace operation, is illustrated. Quality and grain size of the coke added to the charge will influence the build-up of the coke bed and will thereby also affect the electrical re-''Elektrokemisk A/S, Oslo, Norway. resistance and reduction potential in the furnace.

Jan 1, 1963

By H. Dolezal

An investigation was made on the use of magnesium for the direct reduction of rutile to make low-cost, offgrade titanium which could be upgraded to an acceptable grade of metal by electrorefining. Reductions made with charges containing magnesium chloride under hydrogen yielded products with oxygen con-tests close to the theoretical equilibrium composition. Two reduction products were made from rutile for use in electrorefining amenability tests: (1) a product from reduction in an inert atmosphere which contained 88.9 percent titanium and 4.42 percent oxygen, and (2) a product from reduction in a hydro-gen atmosphere which contained 92.5 percent titanium and 2.40 percent oxygen. Reduction products obtained under both of these conditions were amenable to electrorefining.

Jan 1, 1965

By X. Gu

Mining operations, especially surface coal mines, have great impacts on the local ecosystem and the environment. However, it has been a common practice in mine design that the economic evaluation considers only the operating and capital costs, while the costs incurred due to ecological damage are left out. Such practice underestimates the total cost of mining and ignores the difference in ecological impacts between different mine design alternatives. With growing interest in sustainable development, the mining industry is under increasing pressure to operate not only based on economic and engineering principles but also on principles of sustainability. Therefore, estimating ecological costs of mining and considering such costs in the mine design process is an important step towards reducing ecological impacts at the design stage. The objective of this paper is to quantify the ecological costs of open pit coal mining and to demonstrate the influence of such costs on the ultimate pit design. The ecological costs of mining are estimated based on the areas and types of land damaged by mining activities and the carbon emission from energy consumption. Four major components of ecological cost are identified, namely, lost value of direct eco-services, lost value of indirect eco-services, prevention and restoration costs, and the cost of carbon emission from energy consumption. Necessary equations are given for estimating these costs. An algorithm is described for ultimate pit optimization in coal deposits with near-horizontal coal seams. A case study is presented in which the ultimate pits with and without ecological costs are optimized and compared to show the influence of ecological costs on the pit design outcome.

Aug 1, 2013

By Amir Hajizadeh Omran, Mehdi Irannajad, Sima Mohammadnejad, Fardis Nakhaei

"This study presents an experimental program performed to investigate the effects of flotation variables including gas flow rate, froth depth, slurry solids percent, frother/collector dosage and pH on the froth bubble size during desulfurization of an iron ore. These conditions were varied using a central composite design (CCD). Image analysis techniques have been developed and used successfully to characterize the froth bubble size. Results of the CCD experiments showed that the flotation variables have different effects on the froth bubble size. The froth height, air flowrate, pH and solid content had the most important influence on the froth bubble size. The interaction between the collector-frother, pH-collector, frother-air flowrate, solid content-froth height, pH-froth height and solid content-pH were also significant. Process state can be accurately deduced from the froth surface appearance, providing a convenient way to quantify the parameters as a function of the process control. INTRODUCTION Flotation processes are subjected to a wide variety of process disturbances, some of which are made by the change in mineral features and others to variation in operating procedures. Feed and air flow rates, densities, size distributions and shapes of particles, surface properties, and reagent dosages and compositions can all change, often with significant effect on the performance of the plant (Moolman et al., 1996a). Flotation process efficiency is governed by the wettability of the solid as well as the surface tension at the liquid-gas. Both of these properties are influenced by operational conditions encountering in a flotation process. The structure of froths developed on the pulp surfaces of flotation cells has a remarkable effect on both the grade and recovery of minerals in the concentrate (Shean and Cilliers, 2011)."

Jan 1, 2018

By D. Holz

In this work we present a novel level set-based model for the real-time simulation of soil deformations. A level set defined by a signed distance function and sampled in a regular 3D grid represents and tracks the soil volume under deformation. Moving away from classical 2.5D heightfield representations of soil to a full 3D volume representation allows for improved tracking of cutting tool operations and the simulation of near-vertical or vertical soil faces. The proposed level set representation furthermore provides a versatile mathematical platform for modeling additional effects such as soil slip, and does not suffer from the sampling limitations of commonly used heightfields. Cutting forces applied to the tool are simulated via a formulation based on the Fundamental Equation of Earthmoving, modified to support inclined soil surfaces and transient states of tool motion. Discretisation of this 2D cutting force model with respect to the tool surface allows capturing the effects of irregular 3D terrain shapes on blades and buckets. The surcharge created during cutting operations is tracked in the form of particles and included in the soil failure force computation. We make use of an adaptive, hybrid level set-based and particle-based soil deformation scheme, which allows the soil deformation to be simulated in real-time.

Aug 1, 2013

By D. Harrington

Fire is always a serious-menace, whether in a residential or in an industrial region; in wartime it is particularly damaging in an industrial plant. The mining industry is especially vulnerable, as its plants are generally more or less isolated front centers of population and do not have access to modern fire-fighting equipment; moreover, owing to the transitory rapture of most mines, their surface structures; are often relatively flimsy and flammable.. Trained firemen seldom are available at or near mining plants to teach the fundamentals of fire-fighting to local fire brigades, with the result that efficiency in combating actual fires is lacking. Often the attitude "it can't happen here" is held by the management of a mining property, unless the plant has suffered a serious fire; even then lapse of time is very likely to induce forgetfulness as to the possible hazards. The necessity for producing metals for the prosecution of this war has increased management's responsibility. Whereas heretofore the loss of a plant or mill by fire meant merely monetary less to the stockholder of the company, now the national interest is affected, in that the nation suffers from loss of production of minerals indispensable for war purposes.

Jan 1, 1943

By G. W. Douglas

The need for dimensionally stable filled polymer composites has spurred the quest for materials that possess a negative coefficient of thermal expansion (CTE). Finding minerals and materials with a negative CTE large enough to counteract the substantial CTE found in polymers proves challenging. Much research has been per-formed over the last decade to uncover various materials that possess this unusual behavior. A list of materials that have demonstrated negative properties are discussed, as well as the experimental use of one such material (ZrW2O8), in a polymer matrix composite. Other negative properties, such as negative Poisson?s ratio and negative stiffness, are also examined. Key words: Negative properties, Coefficient of thermal expansion, Zirconium tungstate

Jan 1, 2010

By Jan Klein

"The last decade of the 20th century saw the development of one of the last missing geophysical tools for mineral exploration: the Airborne Gravity Gradiometer. It is possible that Airborne Induced Polarization, one of the stillelusive systems, will make its debut in the next few years. In this sense, the paper point out are the most recent and important improvements in geophysical technologies for mineral exploration. Airborne techniques are followed by the systems used on the ground and in boreholes. New equipment and data processing and modeling software are referred to. Brief remarks are made about developments that can be expected in the years to come, these will be mainly focussing on deep search in rugged and conductive terrains. "

Apr 24, 2001

By Essie Esterhuizen, John Ellenberger, Dennis Dolinar

"Underground stone mines in the United States use the room-and- pillar method of mining. The stability of the roof between pillars determines the mining dimensions and size of equipment that can be used. The findings of a survey of roof span stability issues and design practices are presented, and the observed factors contributing to roof instability are discussed. Identified stability issues are evaluated, such as maximum roof span, horizontal stress, and roof beam stability. The results of field observations, roof monitoring, and numerical analyses are used in the evaluation. The importance of the first roof beam thickness and its impact on roof stability and support requirements is presented. An evaluation of the current experience with stone mine roof spans relative to international experience is presented. A step-by-step design procedure is suggested which emphazises the need to collect adequate geotechnical data, understand the immediate roof stability, select a mining direction, and meet support requirements.INTRODUCTIONIn room-and-pillar mines, the roof between the pillars is required to remain stable during mining operations for haulage as well as access to the working areas. Roof and rib falls account for about 15% of all reportable injuries in underground stone mines (Mine Safety and Health Administration, 2009). Therefore, the stability of the roof is an important safety consideration. The size of the rooms in underground stone mines is largely dictated by the size of the mining equipment. Large mining equipment is used, requiring openings that are on average 13.5 m (44 ft) wide by approximately 7.5 m (25 ft) high to operate effectively (Esterhuizen et al., 2007). The dimensions of the roof spans are largely predetermined by the equipment requirements, and design is focused on optimizing stability under the prevailing rock conditions. If the rock mass conditions are such that the desired stable spans cannot be achieved cost effectively, it is unlikely that underground mining will proceed. In addition, large roof falls can extend across the full width of a room and may extend more than 5 m (16 ft) above the roof line. These large falls are a safety hazard and can have a significant impact on mine access and production. The National Institute for Occupational Safety and Health (NIOSH) research into stone mine roof stability has focused on identifying both the causes of roof instability and techniques to optimize stability through design."

Jan 1, 2010

By L. A. Bertram, F. J. Zanner

"The goal of this paper is to present a tool to simulate transient melting of the electrode tip. This capability is needed to develop and test furnace control algorithms since experimental determination is difficult and expensive. Simulation incorporates parameters (including arc voltage, arc current, electrode gap and furnace pressure) from previous quasi steady experiments with 460 mm diameter Inconel 718 electrodes.Cathode heating rates (determined by classical as well as experimental arc models) are linked to these independent variables. After radiative loss adjustments to the heating, transient one dimensional melting is computed. IntroductionThe vacuum arc remelting (VAR) process attempts to improve the physical and chemical homogeneity of a static-cast electrode by remelting and solidification in a quasisteady manner. To achieve steadiness of furnace operation requires automatic controls based on inputs measuring physically relevant state variables of the process. Previous industrial scale VAR studies (1,2,3) involving stainless steels, superalloys, and other alloys have provided a basis on which control strategies of some generality can be proposed (4). Of these measurements, the data for Inconel 718 is the most complete, so discussion in this paper is restricted to this alloy.Studies of the In 718 alloy subjected to the VAR process have established that melt rate M (kg/hr) depends not only on the melt current 1m (kA) supplied to the furnace, but also on ambient gas pressure of CO, PCO (micron), and electrode gap ge (mm) as well (1):"

Jan 1, 1986

By L. B. Tsymbulov, N. A. Fedorova

The equilibrium of exchange reaction (Cu20)+[Ni]=(Ni0)+2[Cu] taking place in the course of interaction of metallic nickel-containing copper melts with different oxide melts (Cu20-NiO, Cu20-NiO-Si02, Cu20-NiO-FeO(Fe203)) in the area of their homogeneity has been studied. The studies, based on the known value of equilibrium constants and defined copper and nickel activity indices in metallic melts and equilibrium concentrations of Cu, Ni, Cu20 and NiO, determined the YNio/ycu2o ratios in the oxide melts of the above systems. For the equilibrium between nickel-containing copper and binary oxide melt Cu20-NiO, values of YNiO and Ycu2o were determined both by calculation and experimentally. Based of the data conclusions regarding oxide melts construction are presented.

Jan 1, 2007

By D. M. Muir

Many plants produce iron(II)/(III) waste liquors which must be treated by neutralisation and precipitation to remove the iron. Iron can be precipitated as crystalline goethite or jarosite by controlled oxidation at low pH and as magnetite by controlled oxidation at high pH, but only at elevated temperatures (>70°C). This study focuses on the characterisation and settling properties of the iron oxides produced at ambient temperatures using various neutralising agents in order to improve the performance of thickeners. It was found that two-stage addition of caustic to FeC12 solutions produced a fast settling material characterised by Mossbauer spectroscopy and XRD as maghemite and magnetite. However, lime and magnesia additions resulted in more ferrihydrite formation and much lower settling rates because of the enhanced oxidation of Fe(II) by air. Settling rates decreased significantly as the proportion of Fe(III) to Fe(II) in the liquor increased. The mechanism of iron oxide precipitation is discussed together with some reasons for the different behaviour of the neutralising agents.

Jan 1, 2006

By T. H. Dubaniewicz

Many mines rely on toxic gas sensors to help maintain a safe and healthy work environment. This report describes a prototype monitoring system developed by the U.S. Bureau of Mines (USBM) that uses light to power and communicate with several remote toxic gas sensors. The design is based on state-of-the-art optical-to-electrical power converters, solid-state diode lasers, and fiber optics. This design overcomes several problems associated with conventional wire-based systems by providing complete electrical isolation between the remote sensors and the central monitor. The prototype performed well during a 2-week field trial in the USBM Pittsburgh Research Center Safety Research Coal Mine.

Jan 1, 1995

By D. J. M. Farnsworth

Since the 1.940's, the bulk of the ore production from the Sullivan Mine has come from pillars. These pillars, located from 100 to 2000 feet below surface, have been subjected to considerable ground pressure. Mining techniques were adopted to minimize the problems of deteriorating ground conditions. These techniques included an orderly sequential blasting of pillars along a retreat front, stage blasting of tall pillars in horizontal slices and utilization of broken pillars as "buffers". The latter two techniques involved leaving substantial tonnages of broken ore in place for as long as 4 years. Rapid oxidation of metal sulphides, with attendant heat and noxious gas generation, had occurred in a few very localized areas of the mine associated with a major water course. However, in a very short period starting in 1972, sulphide fires spread to several of the large blocks of broken ore that had been left inactive for lengthy periods. There proved to be no feasible method of extinguishing these fires, except by complete removal of the burning ore. The attendant problems of handling large tonnages of burning ore have had considerable negative impact on the mine operation. The chemical reactions involved in these sulphide fires have been studied by the mine staff to determine the conditions necessary for' initiation and propagation of the tires. Techniques to safely and efficiently handle hot ore have been implemented and refined. Lastly, and most important, mining methods at the Sullivan Mine have been revised to ensure that additional fires do not occur.

Jan 1, 1977

By A. Rajoria

A dynamic process model for predicting the fluidized bed roasting of copper concentrates with high arsenic content is presented in this work. Mass and energy balances were performed based on roasting mechanism derived from thermodynamic data of species. The reaction rate data, obtained from pilot plant studies on major reactions, were used in tuning the kinetic parameters of the model. DEAS, a dynamic simulation package, is used in setting up the fluidized bed roaster plant model. The effect of process parameters such as concentrate feed rate, concentrate composition, airflow and cooling water rate on the temperature and conversion of roasting reactions are analyzed. The plant model captures the highly transient conditions occurring during the plant start-up, shutdown and other process perturbations. The application of this model in constructing a virtual plant environment for validating the operating procedures and operator training is presented.

Feb 23, 2014

By P. E. Churchward

The Bureau of Mines developed a process using amines for recovering tungsten as ammonium paratungstate from alkaline leach liquors without producing synthetic scheelite as an intermediate product. Over 90 pct of the tungsten in low-grade scheelite or ferberite concen-trate was recovered as ammonium paratungstate by (l) autoclave leaching the concentrate with Na2CO3, (2) solvent extraction of the acidified leach liquor with kerosine solutions of either a quaternary amine (Aliquat 336) or a primary amine (Primene JM-T), (3) stripping the tungsten values from the quaternary amine with ammoniacal NH4C1 or from the primary amine with NH4OH, and (4) crystallization of ammonium paratungstate from the strip liquor. Reagent consumption in pounds per pound of W03 recovered was, for the quater¬nary amine, 3 Na2CO3, 3.5 H2SO4 , 2.2 NH4Cl, 1 NH3, and 0.4 glacial acetic acid; for the primary amine, it was 3 Na2CO3, 3.5 H2SO4, .06 NH4Cl, and 0.9 NH3. Both reagents extract molybdenum along with tungsten. Silicate and phosphate are partly extracted and contaminate the product; leach liquors containing these impurities require preliminary purification.

Jan 1, 1966

By N. Bahrani

Knowledge of the state of stress in the Earth?s crust is very important to the safe and efficient development of underground excavations in mining and civil engineering projects. A number of methods have been developed over the past 40 years to assess the stress field in the rock mass. These range from local estimates derived from compilation of regional stress databases to back-analysis of field observations to dedicated in situ measurements. The Geomechanics Research Centre (GRC) at MIRARCO has a long history of undertaking in situ stress characterization and measurement. In this paper, the stress measurement techniques used by the GRC, including overcoring and undercoring in addition to borehole breakout back-analysis, are briefly reviewed. The limitations and application of each technique for different ground conditions and the challenges involved during the field work and in interpretation of the results are discussed. A successful stress measurement campaign is not limited to acquiring valid local measurement, but must include a careful interpretation and integration of the measurement with other geological and geotechnical context information. Based on our experience, it is suggested that all available stress indicators and data are combined and integrated with the local geological and geomechanical conditions to derive a consistent stress characterization for a given site.

Aug 1, 2013

By W. de Klerk, M. B. Thorpe

Golden Star Resources Bogoso operates in Ghana’s Western Region. The gold recovery plant includes; a flotation circuit producing a concentrate for the BIOX® process that oxidizes sulphides before a CIL circuit; and a dedicated CIL circuit. BIOX® uses bacteria, therefore water from the BIOX® and CIL plants remained separated; CN water could not be introduced into the flotation / BIOX® circuit. The operation built a process water inventory with high TDS and installed a process water treatment plant (PWTP). Water was released in compliance the permits but containing some thiocyanate. The PWTP brine was returned to the TSF, further exacerbating the TDS. The operation experienced a drought removing the traditional water sources; the team evaluated the options to maintain production - various water streams were laboratory tested provided options for water use. The paper presents the story (treatment chemistry and process chemistry) of continued operations by treating stored water and PWTP discharge water with peroxide; brine usage within the CIL circuit, which increased gold recovery (laboratory testing) and reduced the TDS. Water flows were further modified to include hydraulic tailings re-mining to a CIL circuits. Details of the recovery, basic chemistry and costs savings are provided.

Jan 1, 2014