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By Mariana Beatriz dos Reis Silva

A influência da temperatura de reaquecimento e do tempo entre passes na evolução microestrutural dos ASTM F138 e ISO 5832-9 durante o processamento termomecânico simulado foram investigados. Ambos os materiais foram reaquecidos a 1200°C e, por comparação, o ISO 5832-9 foi reaquecido a 1250°C. As amostras foram submetidas a simulações de deformações em testes de torção com tempo entre passes de 50 e 5 s. As amostras foram caracterizadas por MO, MET, EDX, EBSD e testes de microdurezas. As curvas de tensão-deformação, a evolução microestrutural e precipitação foram analisadas e correlacionadas com o refinamento de grãos. O aço ISO 5832-9 reaquecido a 1250°C mostrou um comportamento diferente devido a maior dissolução dos precipitados.

Aug 17, 2017

By P. W. van Deventer

?Soil quality is the capacity of a soil to function, within ecosystem and land use boundaries, to sustain biological productivity, maintain environmental quality, and promote plant, animal and human health?. In the long-term, vegetative rehabilitation of mining wastes aims at, as far as possible, the proper ecological integration of the reclaimed area into the surrounding landscape, which is sustainable and requires minimal maintenance. A certain succession pattern is therefore needed. Recent ecological concepts recognize the role of the substrate?s quality and nutrients in affecting the rates and directions of succession patterns. Although pedogenesis and eventually soil quality in mine waste are not well known, monitoring of soil quality parameters in kimberlite mine tailings reveal a remarkable establishment and or improvement of specifics oil quality indicators. During the same time the vegetative cover?s total functionality as well as reproductive ability improved. Functions of soil, and thus soil quality, can be assessed at the field, farm, ecosystem, pedosphere, and global scale. It is recognized, however, that management of soil becomes increasingly difficult at larger scales, but for demarcated mine waste sites it is possible to ameliorate and manage and assess soil functions and quality. Therefore the significance of the study is the following: soil functions and quality become inseparable from the idea of system sustainability, and are considered as key indicators of ecosystem sustainability on rehabilitated mine tailings material.

Jan 1, 2008

In choosing such a threadbare subject for a paper I fear that I may in some measure be taxing your patience, yet as upon the accuracy with which the work is done depends the result of conclusions drawn as to whether a property will be profitable to work or otherwise. The subject cannot be too well threshed out, and I trust that upon certain points that have come within my own experience I may be able to give 'hints that will prevent others from making mistakes. First as to alluvial. Gold is often found from the grass roots down, often ill particular horizontal bands in the wash, but more generally concentrated either on a true or false bottom. When sampling dry ground for proposed hydraulicing I have obtained accurate results only by taking the whole of the dirt from measured shafts, stacking it as it was lifted on a tarpaulin, and putting the whole quantity through a carefully constructed box. In wet ground careful borings will in most cases give fairly correct results, but where it is possible to sink shafts, that should be done, as a guide is then also obtained as to the nature of the wash, whether it is bouldery, cemented, or free. Sampling in a face is a more difficult work in many respects than in new ground, as so many elements enter into action to spoil accurate sampling. Of course the great thing to avoid is sampling in any place where either natural or artificial concentration has taken place, and very much has to be left to circumstance and the sampler's own judgment. In passing I may mention that I have on several occasions seen diggers deceive themselves in wet ground where they were sinking and coping as best they might with water. They would take a dish of dirt from the bottom of their hole, pan it off, and take the result as a fair yield, and on the strength of it perhaps spend a lot of time and money in tail races and whereas in their sample there had been a process of concentration carried on, the movement and working in the water had caused the gold to work down, and anything like accurate estimations by the method pursued were out of the question.

By Secretary of the Interior

"INTRODUCTION The Bureau of Mines Synthetic Liquid Fuels Program again forged ahead during 1952, and important technical advances led the way to improved methods of converting coal and oil shale into liquid fuels. Marking the eighth year of activities under this program, the pact 32 months brought a new domestic industry nearer realization.The increasing demand for gasoline and oil and the rising cost of finding new petroleum, coupled with America's growing dependence on imports and the unsettled international situation, have continued to emphasize the importance of the Bureau's Synthetic Liquid Fuels Program. Oil, the indispensable material of wartime, likewise has critical importance in peacetime, touching as it does the life of every individual. Supplementing petroleum with synthetic liquid fuels will not only conserve this Nation's petroleum reserves but also will bring into greater use its tremendous reserves of coal, as well as the vast deposits of oil shale for which no other practical use has yet been found.The Bureau of Mines Synthetic Liquid Fuels Program is one of the most important and far-reaching of the Government's research projects. Through development of commercial synthetic liquid fuels, the United States can obtain oil products from its great inland reserves of coal and oil shale to supplement petroleum in any quantity that may be necessary, consistent with economic and other requirements, such as national defense. The use of raw materials from such deposits would be of highest importance in wartime, when shipping lanes are menaced by the enemy. The Synthetic Liquid Fuels Program of the Bureau of Mines and research efforts of industry have advanced. American technology to the point where it is now possible to begin the design and construction of prototype plants. Certainly, significant improvements will be made as the program continues, but this prospect in no way alters the fact that the start of prototype plants should be encouraged. These plants, as the first step in the development of a synthetic fuels industry, would serve a threefold purpose:"

Jan 1, 1953

This report provides the results of an industrial engineering study that assessed the safety and efficiency of underground ore handling in U.S. metal mines. One of the primary findings of the study was the improvement needed in controlling muck size in the ore handling stream. Oversize ore causes much additional labor, creating work stoppages and is a principal cause of accidents in metal mines. This report includes data on block caving, back cut and fill room and pillar, shrinkage stoping, and sublevel stoping.

Jan 1, 1974

Existing processes for the recovery of platinum group metals (PGM) from UG-2 ores place stringent requirements with regard to chromite content upon feed material to the plant. An alternative hydrometallurgical process for which this is not an issue is proposed that involves reductive roasting of the ore followed by leaching with HCl/chlorine, ion exchange, and recovery of PGM from the ion exchange eluate by reduction. Problems associated with leaching of PGM are discussed and results of laboratory testwork for each of the process steps are given.

Jan 1, 2004

By F. D. Wang

This report presents a structural-mesh-generating computer program for the two-dimensional finite-clement method of mine structural analysis of single and multiple openings in nonhomogeneous rock mass. This program greatly reduces the amount of input data required and the chances of error which otherwise are large owing to the large amounts of data and the complex mesh involved. The program description, a user's guide, example problems, and program listing are included.

Jan 1, 1971

By Marlon Mendieta, Cristhian Guillén, Ned Vásquez

Actualmente en mina Cerro lindo, el 60% de la producción de mineral proviene de la explotación de banqueos descendentes con el método Sublevel Stoping y ante la problemática del incremento de incidencia de “repies” en los tajeos de producción que estuvo afectando la recuperación de mineral y el performance de las voladuras, se tiene como objetivo incrementar la recuperación de mineral y mejorar el performance de las voladuras; se plantearon alternativas y propuesta de mejora en del diseño y esquema de carguio mediante la aplicación de reforzadores de carga, para la explotación de banqueos descendentes.

Sep 29, 2023

By C. Balci

Specific energy is defined as the amount of work required to break a unit volume of rock and is used to predict the performance of mechanical miners. It is obtained from full-scale rock cutting experiments, which require large block samples, experienced personnel and expensive equipment found in only a few research centres in the world. Estimation of the optimum specific energy, at which a given geological formation is excavated at optimum cutting geometry in the most energy efficient manner, from mechanical rock properties to predict the performance/efficiency of roadheaders is the basic aim of this study. The mechanical rock property tests require only core samples, which are easier to obtain and to test. In this context, full-scale rock cutting tests are performed on 23 different rock, mineral and ore samples including sandstone, claystone, tuffite, chromite, trona and copper collected from some operating mines in Turkey. The optimum specific energy values are obtained for each sample. Physical and mechanical property tests are performed on the core samples obtained from the same samples to determine uniaxial compressive strength, indirect (Brazilian) tensile strength, static and dynamic elasticity moduli, Schmidt hammer rebound values, density, and Cerchar abrasivity index. The relationships between the optimum specific energy and the mechanical rock properties are analysed using statistical methods. The results indicate strong relationships between the optimum specific energy and the mechanical rock properties. The strongest relationships are found by using uniaxial compressive strength and tensile strength. The performance models developed in this study are in good agreement with the empirical models previously developed for roadheaders and can be used reliably for prediction purposes. Keywords: Mechanical excavation, roadheader, performance prediction, rock cutting, optimum specific energy, mechanical properties of rocks.

Jan 1, 2004

By Narendra Gupta, Gaurav Srivastava, Abhinav Sharma

From the days when plain detonators and safety fuse were used for initiation of commercial explosives, the commercial blasting and mining industries have made rapid strides. With the advent of electronic detonators in the late ‘90s, the face of commercial blasting was changed forever. The Mining Industry in India initially took a while to embrace Electronic Blasting Systems (EBS), however, more recently the industry has taken to EBS in a big way.

Jan 1, 2015

By D. Endara, E. De la Torre, S. Echeverria

"The study was conducted with the sulfide mineral from the province of Zamora Chinchipe. It was characterized physical, chemical and mineralogical, obtaining between its main results a copper concentration of head ore of 0,58 %. The mineral was homogenized and taken to direct closed circuit: rollers mill - vibratory sieve (mesh # 16). Flotation was carried out in two stages: the collective and selective where in each one were performed 6 water recirculation as suggested by the technique used to relate information of a batch flotation to a continuous circuit called cyclic flotation tests (LCT). In the collective flotation (bulk) 2 Kg of mineral were grinded with 10 Kg of balls for 30 minutes and 62.5% of solids, the pulp was taken to the flotation process with solids percentages of 33.3% and pH 7, it was conditioned with 45 g / t of KAX 1%, 50 g/t of Aerofloat 208 and 20 g /t of Pine oil. The concentrate and tailings bulk obtained were filtered separately for the recovery of water and it was recirculated to the next grinding of 2kg mineral. In the selective flotation 1Kg of bulk concentrate was carried to regrind for 40 min, 62.5% percent of solids, 10 g of lime and 5 g of tannin FLOATAN T5, the pulp was taken to the roughing-collection-refining flotation circuit controlling the pH between 10.5 and 11 where conditioning (60 g/t of Aerofloat 208 and 30 g/t of Pine oil) and adding lime to the circuit and FLOATAN according to the procedure. The four fractions obtained from the circuit were filtered; the water was recirculated to the regrind process of the bulk concentrate. In the collective flotation process tends to stability in the fourth recirculating water to obtain a copper content of 4.5% and a recovery of 87%, recirculated water represents 69.8% of all water used in the 6 recycles. In the selective flotation circuit the fifth recirculating of water is the optimal where obtaining a copper content of 13% and a recovery of 72%, recirculated water in the selective flotation circuit represents 95% of the total water used in the 6 recycles."

Jan 1, 2018

By Marius B. Wechsler

There are considered deep piles which are fixed in blocks of rotating machinery foundations. A mathematical background is developed for determining the behavior of this kind of piles for motions caused by horizontal and vertical oscillations, as well as by roc-king and twisting. It is assumed that the piles come across a top soil layer of depth c, not capable of lateral support, and penetrate over a length b, in a bottom firm soil layer, or in a bottom soft soil layer in which vibrations can produce voids around the piles. With respect to b and c, as well as to the elastic properties of piles and soils, the analysis leads to the maximum bending moments and shear forces subjecting the piles, to the maximum lateral bearing on the bottom soil layer, as well as to the deflection of the pile and the displacement of the foundation block. The results of the performed analysis can be applied to seismic loads too, and they are illustrated by a numerical example.

Jan 1, 1987

By M P. Cipold, J F. Bachmann, C C. Bachmann, J Ha

Knowledge of fuel qualities is of ultimate importance for the efficiency of chemical plants or power stations. Although most blending yards are equipped with automatic samplers and the derived samples are processed in the laboratory, the quality variation of the blended product may still be strong. This is caused by several reasons. First of all the process of sampling, crushing, dividing and analysis is time consuming. Results are available only with a delay of two to 24 hours. During this time blending is operated without knowledge of the main parameters. Conveyors with high throughput require expensive sampling systems capable of handling samples which are representative. The frequency of sampling needs also to be high in order to be representative. This results in high maintenance costs and also downtime of the sampling system.Online analysis of bulk materials has matured over time and today it can supplement but not replace laboratory analysis. As an example, J&C Bachmann has realised a coal quality monitoring system on the coal supply of a South African coal processing plant. The plant consumes ~42 Mt of coal per annum. The blending yard consists of two sets of three heaps where coal of six different mines is blended according to the factory’s requirement. From there, the blended coal is fed to the factory on two different belts.In 2010 the plant installed a TEXAS X-ray fluorescence analyser as a trial. It was tested under different conditions on several belts before the customer decided to install six TEXAS analysers on the feed belts to the stackers and two more analysers on the reclaimer belts. All analysers are installed directly on the belt and not on a substream.During the test period blending strategies were developed in close cooperation between the customer and J&C Bachmann. The use of the analysers in conjunction with the blending model has proven that the variation of the reclaimed coal quality was decreased significantly, which results in increased process performance and significant cost savings.CITATION:Bachmann, C C, Bachmann, J F, Cipold, M P and Ha, J, 2017. Online quality control of a coal blending yard, in Proceedings Eighth World Conference on Sampling and Blending , pp 125–128 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017

By Luis Enrique Vargas

Las técnicas estadísticas multivariantes (análisis factorial y el análisis cluster), permiten establecer el grado de interdependencia y la relevancia de las correlaciones múltiples entre las variables estudiadas (46 elementos traza), características que no se pueden determinar con los métodos descriptivos tradicionales. En ese sentido, el presente trabajo aborda la investigación realizada a la cuenca del río Huaura, Lima, donde se efectuó un muestreo de sedimentos activos de corriente en 393 estaciones representativamente distribuidas. Dichas muestras han sido tamizadas con la malla 200 y analizadas por el método ICP-MS, previa digestión con agua regia, con el objetivo de determinar elementos traza distintivos en sedimentos activos, de acuerdo al ambiente geológico del cual provienen, mediante su comportamiento multivariante, dispersión y distribución geoquímica secundaria y así identificar elementos traza de interés minero, relacionados a los elementos traza distintivos previamente definidos.

Sep 14, 2009

By John Bradford

El presente texto describe la geología, historia, geografía del yacimiento epitermal de oro denominado Poracota. Dicho yacimiento es un sistema epitermal de alta sulfuración que está ubicado a 160 km al NW de Arequipa y se hospeda en el Arco Volcánico continental calco-alcalino del Sur del Perú, del Oligoceno superior al reciente. Asimismo, se encuentra en una importante franja de mineralización epitermal de metales preciosos del Mioceno, que incluye las minas de oro-plata de Orcopampa, Arcata, Shila, Cailloma y Sukuitambo, la mina de plata-metales comunes de Madrigal y los recientes descubrimientos de Ares y Chipmo. La zona aurífera está en la zona de silicificación intensa, es sílice cavernosa (vuggy) y en cuarzo-alunita sobrepuesta por pirita. La zona de cuarzo-alunita envuelve a la zona aurífera silicificada y la alteración decrece hacia afuera a dickita, caolinita, illita, clorita y calcita.

Apr 26, 1999

By Foster Bruner

Jul 20, 1956

Novel flotation reagents were developed to improve the flotation of coarse particles. Laboratory tests conducted on an anthracite coal sample from Kyung-Dong Coal Company, Korea, showed that the reagents can successfully clean 2?3 mm top-size materials. Pilot-scale tests conducted on a 1.41 mm x0 coal gave substantially better results than those obtained using kerosene as collector. The pilot-scale test results were used to develop a flowsheet, in which the 1.41 mm x0 fraction is cleaned by flotation and the 4 x1.41 mm coal is cleaned by single-stage spirals. The performance of this circuit was compared with another flowsheet, in which the 0.5 mm x0coal is floated using the conventional flotation reagent, with the 4 x0.5 mm material being cleaned using two separate spiral circuits. The performance of the two flowsheets was compared by computer simulation. The results showed that the flowsheet consisting of the coarse particle flotation circuit can give substantially higher yield sat a given product grade. Keywords: coal flotation, coarse particle flotation, collector, spirals, computer simulation.

Jan 1, 2002

By George J. Conroy

This Bureau of Mines report summarizes the results of a study of mine inspection records covering 2,200 mining installations over a 3-year period ending December 1974. Tables show the relative frequency of violations of certain provisions of the Coal Mine Health and Safety Act of 1969 in particular areas of concern, such as circuit breakers, grounding, and permissibility. Examples of past use of the data and analyses are presented.

Jan 1, 1976

On the Role of Dixanthogen in Froth Flotation

Sep 13, 2010

By Carl R. Peterson

[In lTI n,v und I'gr'oun nllnin~ Opt'I'ali n' the high . t cost is the loading and I 3ulage of t tln-of -D"'line ot'. 01' hauling costs can be r duced signifi-cant\v with the us ~ (r \) >It corn'e)'OI' " a COnlTllOn pl'acti c i.n coal and other s 0 t'L rn I n r' a l III i, n e , '. Jf 0 vel s i z ' () f' e can bee 1 i 11.11 tl ate I rH'i 0 I' lO C n v e . in g, ]

Jan 1, 1976