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By J. C. Reid

Pre-cambrian scheelite deposits in Northeastern Brazil are widespread in a high grade metamorphic terrain. Previously these deposits had been interpreted as contact-metasomatic. In this paper, a volcanigenic model is invoked based on the volcanic setting (proximal to distal) and the absence of associated felsic intrusives and spatially associated metasomatic skarns. The tungsten was introduced into sediments by volcanic- exhalative processes and subsequently remobilized and further concentrated by heat and metamorphis fluids associated with high-grade metamorphism and migmitization. An alternative syngenetic - diagenetic model is discussed which requires the transport of tungsten by heteropoly acids and deposition of the tungsten as a function of Eh and Ph conditions and different clastic depositional environments. While such stratabound tungsten deposits are considered rare in North America, the hypotheses developed in this paper may open new areas for exploration.

Jan 1, 1983

By U. C. Galimidi, J. M. Stewart, A. J. Van Rensburg

The effect of body movement on convective heat transfer from a man performing a block-stepping task was investigated experimentally by direct measurements of convective heat transfer. A series of experiments was conducted in which a nude man was required to stand at rest or to block step at 12 and 24 steps per minute. Wind speed, which was kept constant during each experiment, spanned the range 0,5 to 3,5 m/so Air temperature was kept constant at 43 °C in all the experiments. The results showed conclusively that the convective heat-transfer coefficient depends on the stepping rate. The effect of body motion can be regarded as being equivalent to an increase in the velocity of the free stream. The equivalent increase in air speed was found to be 0,36 and 0,77 m/s for 12 and 24 steps per minute respectively. Data from various sources, including the present study, indicate that wind speed should be increased by about 0,30,0,55, and 0,80 m/s to account for low, moderate, and vigorous body movements respectively. These findings are of direct relevance to the practical assessment of heat stress.

Jan 1, 1979

The development of the Moura Coal Preparation Plant is described, commencing with the first'stage of the plant commissioned in 1963. The subsequent expansion stages are traced through to October, 1973. The plant has undergone frequent stages of expansion and modification and this process is continuing. The development programme for 1974 is described as proposed in late 1973. The characteristics of the Moura and Kianga field coal seams with respect to washability are summarised and some comment is made on the blending of these coals prior to washing, to ensure production of export grade coal within specification.

Jan 1, 1974

By Douglas J. Harvey, Chi-Mou Ni

"This paper presents an analysis technique for the solidification of metal castings. This method, based on a modified finite difference scheme with an irregular mesh, is capable of dealing with the complex geometries of castings. The nonlinearities in material properties of specific heat and thermal conductivity, arising from the phase change during solidification, are accounted for in the step-by-step calculations. Two solidification problems are solved with this analysis technique and the calculated results compare satisfactorily with experimental data. IntroductionCasting process design engineers are often faced with the difficult problem of designing castings to be produced porosity-free. Since the solidification of metal is affected by many interacting variables such as the thermal conductivity, density, and specific heat of both the molten metal and the mold, it is easily seen why this is a difficult task.Typically, casting tooling design is an intuitive process which builds on past successful methods. After processing equipment is constructed, trial castings are made and examined for dimensions and integrity. Changes in the tooling are generally required to improve casting soundness or to reduce cycle time. In the permanent mold process, tooling is complex and difficult to alter after initial construction. The water-cooled steel molds are part of the complete automated system. Associated holding furnaces, pouring ladles, casting conveyers, and utility connections all make other than minor adjustments a costly and time consuming task. An analytical method for using the principles of heat transfer for predicting solidification patterns would be of great value in the permanent mold process by minimizing costly changes."

Jan 1, 1986

By T. D. Oulton

The only known attapulgite clay deposits of any considerable extent and purity in the United States are roughly bisected by the Georgia. Florida state line between Decatur County, southwest Georgia, and Gadsden County, northwest Florida. Although attapulgite clay occurrences both farther East and South are known and have been mined to some extent in the past, at the present time it can be said that substantially: all of the commercial attapulgite clay mining and pro¬cessing is concentrated in a roughly rectangular area some 25 miles long by 15 miles wide,, in the general region of Attapulgus, Georgia, and of Quincy and Havana, Florida. Within this area are located the clay processing plants of the four major producers as well as most, if not all, of the currently active mining operations. The approximate location of the plants and of some of the open mines are shown in the local area map, Figure No. 1, for the purpose of orientation only.

Jan 1, 1965

By R. Reeves

Coal producers and utilities depend on automated coal blending systems to reduce costs and meet stringent environmental regulations. Over 30 systems installed in the United States since 1987 use on-line PGNAA (Prompt Gamma Neutron Activation Analysis) analyzers to accurately control the blending process. Experience and detailed engineering are required to integrate real-time data produced by the coal analyzer with a control system to meet demanding performance specifications. This article reviews successful installations and lists important features including interfacing analyzers with plant control systems, specifying feeders and weigh scales, and managing data.

Jan 1, 1995

By Ryokichi Shimpo

Much amount of sludge is produced from the wastewater treatments in surface finishing industry. There are many problems for the abandonment of the sludge because of the high water content and heavy metals included. It is often observed that hexavalent chromium, which is toxic, is generated in the course of heat treatments of the sludge for reducing its amount by dispersing water. In this study, conditions of the sludge calcinations for reducing water contents have been examined. Maximum hexavalent chromium generation was observed in the temperature range around 773 K, at which most of the crystallization water decomposed from the sludge. When the heating temperature became higher than 1173 K, the amount of the hexavalent chromium extracted from the calcined sludge became as low as 10 mg/kg sludge. When the sludge was heated with iron oxides, FeO or Fe203, iron ferrite has been synthesized which may be used as a magnetic material. The amounts of hexavalent chromium generated in the heat treatment with iron oxides were not much different from those without iron oxides.

Jan 1, 2003

By H. Billmayer

This report covers the period from June 17, 1974 to February 20, 1975, and describes the work performed in compliance with the requirements of Contract No. H0346102 and Modification No. 1 thereto. The purpose of the contract was to design protective canopies for an Elkhorn Scoop, a Lee Norse Miner, a Wilcox Miner and a Wilcox Bolter; to construct mockups of the canopies; and to obtain machine operator evaluations of the canopy designs by assessing the mockups while installed on their machines in the mines. The overall program objective was to achieve protective canopy designs for the four machines which would be acceptable to the operators.

Jan 1, 1975

By Pierre Mousset-Jones, Jaak Daemen, Songlin Zhang, Jon Hurley

Most western United States open pit gold mine ore bodies are disseminated deposits. The mineralization is so irregular that it is difficult to visually identify the ore/waste boundary. Blast hole samples are used to interpolate digging polygons based on the pre-blast position of the bench. Dilution caused by blasting is of major concern at these mines, since blast movement can mix and dilute the ore and move it beyond flagged digging polygons established on the blasted rock according to their pre-blast location. Typically, mines try to reach a compromise between blast fragmentation and movement.

Jan 1, 1994

By Robert P. Vinson, Fred N. Kissell, Edward D. Thimons

Because of the high number of accidental methane gas ignitions in metal and nonmetal mines, the Bureau of Mines searched for a simple guideline that would allow mine personnel to evaluate the methane hazard in a given mine. Air samples were collected by the Bureau in 53 metal and nonmetal mines and analyzed for trace evidence of methane gas. Samples were collected in the returns and at the working faces. Those mines classified as gassy by the Mine Safety and Health Administration had a significantly higher average methane concentration than those classified as nongassy. Of the 9 gassy mines sampled, 7 had methane concentrations above 100 ppm, whereas only 1 of the 44 nongassy mines had a concentration above 100 ppm. The 100-ppm concentration may be used as a simple and convenient guideline for forecasting the methane hazard in a mine, whether or not the mine is classified as gassy. There was no consistent correlation between commodity mined and methane concentration, nor was there a correlation between mine depth and methane concentration. Neither of these factors can be considered a guideline for predicting methane hazards.

Jan 1, 1979

By S. Vaidya, R. C. McKellar, N. K. Sinha

Nominally [001]-oriented nickel-base single crystal (SX) superalloy CMSX-10 was investigated at 900°C under constant load, equivalent to an initial stress of 700 MPa, for creep strains from 7% to fracture strain (18.2%). The cross-sectional dimensions of initially uniform cylindrical specimens were measured along their entire length after the tests. The cross-section changed from circular to near elliptical shape. The anisotropic deformation, measured in terms of eccentricity, increased with the increasing strain level, but for a given strain level, it remained constant along the entire length of the initially uniform gauge section. The results are discussed in terms of diameter, eccentricity, area, local stress and microstructural observations. The most striking observation was the fact that all the specimens displayed a yoke-like shape, or the reduction of cross sectional area, at two locations within the originally uniform gauge section. Such observations have not been reported in the literature for single crystal superalloys.

Jan 1, 2006

By Robert L. Brooks

This paper is intended for companies at all levels of the Explosive Industry and in particular, those that do not have a risk manager. It is strictly informational in nature and no reference is made, or intended towards any existing insurance company or agency.

Jan 1, 1993

By W. W. Weller

Heat capacities of ferrous molybdate (FeMoO4) and ferrous tungstate (FeWO4) were measured over the temperature range 51° to 298.15° K. Ferrous tungstate has a lambda type heat capacity anomaly at 74° K. The 298.15° K entropies are FeMoO4) 30.9 cal/deg mole and FeW04) 31.5 cal/deg mole.

Jan 1, 1966

By Mario L. Villa

During 1938, oil activities in the Argentine Republic showed a favorable balance due to the increase in crude-oil production, the incorpora- tion of new producing areas and the discovery of deeper productive horizons. Drilling was as follows:

Jan 1, 1939

By Jürgen Kretschmann, Christina Suarez, Jürgen Brune, Stefan Möllerherm

"The Ruhr region in Germany’s North-Rhine Westphalia is going through significant change. By the end of 2018, the last two underground hard coal mines in the Ruhr, Ibbenbüren and Prosper-Haniel collieries, will close their portals and bring an end to more than 200 years of coal mining and an industry that was once the economic and cultural backbone of the area. Ruhr is undergoing an impressive economic and cultural transformation, as it gradually shifts from being a region once dependent on coal and steelmaking to a post-mining region focused on redesigning itself as a cultural center. This article focuses on the socioeconomic impacts of the transformation into post-mining and the roles of the government, labor unions and local community to aid the transformation from the perspective of an American student. It will look into the cultural values that are helping to drive the transformation and compare them to American standards and values in order to determine if a similar approach can be used in the United States and its coal industry. History and backgroundUnderground hard coal mining has had a long history and a significant impact on the culture and economy in Ruhr since the early 19th 20century. The Ruhr region is located in the heart of the German state of North- Rhine Westphalia. Ruhr is bounded by the Rhine River in the west, the Ruhr River in the south and the Lippe River in the north, with the Emscher River running through its center.The Ruhr is home to around 5.1 million people and spans an area of approximately 4,500 km2 (1,730 sq miles). Before the era of industrialization, the Ruhr was a rural, agricultural region. Small-scale coal mining began in the 13th century, with coal being used for heating, cooking and metallurgical processes, including steelmaking. With 19th-century industrialization, coal mining became a significant driver of the region’s economic structure. Steam engines, and soon, electric motors, allowed for the pumping of mine water and for powerful hoists hauling from deep shafts, enabling miners to reach deeper coal seams that were once thought impossible to mine. The Ruhr mining boom began in the 1850s, supported by Prussian economic policies that attracted many workers and their families to the region. The population grew from 400,000 in 1850 to 5.7 million in 1957. The coal and steel industries were key contributors to Germany’s “Wirtschaftswunder” — or “miraculous economic recovery”— in the 1950s. In 1956, the coal industry reached its peak production of around 112 Mt/a (124 million stpy) of coal and employed almost 600,000 miners."

Mar 1, 2019

By Louis W. Cope

Since its discovery, Cuba has been called the “Pearl of the Antilles.” The country remains that, albeit a little tarnished these days. In Havana, many of the buildings are being refurbished, while some new ones are under construction. Since 1991, the laws have been relaxed so that Cuba is developing a mixed economy of central control with free market. Joint venture agreements have been signed with businesses from many countries. This does not include the United States due to its embargo. But even these regulations have been relaxed some.

Jan 1, 2003

The implementation of NAFTA in January 1994 was expected to have small but beneficial effects on the Mexican economy, mostly through increased investments. Mexico's mining industry was especially likely to benefit, as mineral investment funds would be diverted to the now safer Mexico and away from similarly endowed but more risky Latin American mineral economies. The results during the past two years have shown that it is government and macroeconomic factors that influence investment flows, rather than the fine tuning of trade flows through so called “free-trade" agreements.

Jan 1, 1998

By J Hartog, V Beehan, D Beeson

Treating an ore blend from five different deposits at Newgold’s Peak Gold Mine (PGM) has always been a challenge due to the inherent variability between each of the orebodies.Operating the processing plant at PGM with a ‘normal’ level of process control and a good operations and metallurgical team has allowed the processing plant to achieve above the name plate design at 102 t/h and recoveries in the order of 92.8 per cent for gold and 88.4 per cent for copper.With a company value and culture of striving for continuous improvement, PGM implemented the Manta Cube® system, an advanced process control system, for the semi-autogenous grinding (SAG) mill, gold leach circuit and tailings thickener over a 12-month period throughout 2012 and 2013.The overall benefits of implementing the Manta Cube® system has led to an increase in mill throughput of at least two per cent, improved SAG mill liner life, a ten per cent decrease in cyanide consumption and a reduction in flocculant of at least 30 per cent with no detriment to the gold and copper recoveries.The entire project had a payback period of less than two months, and the combined benefits resulted in an overall increase in revenue of at least $5 million per annum. This is quite significant for a processing plant the size of PGM.This paper describes the methodology, overall results and economic benefit of applying the Manta Cube® system on-site at Newgold’s PGM.CITATION:Hartog, J, Beehan, V, Karageorgos, J and Beeson, D, 2014. Optimisation of the Peak Gold Mine’s processing plant through advanced process control, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 335–344 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By Courtenay de Kalb

The Exposed Treasure gold-mine has, for the past four years, been one of the largest producing mines of Southern California, its annual output havirig con~tituted I per cent. of the total gold and silver production of the entire State. At the present moment the property is idle, owing to the large quantity of water encountered on the lower levels, which will require the installation of a powerful pumping-plant before operations call be recommenced. Moreover, a prompt change in the character of the ore has occurred at water-level, which makes imperative an extensive campaign of development in the region of the un-oxidized ores before a plant adapted to their treatment call be definitely decided upon. The character of the changes encountered in these deeper ores makes the geology of this deposit a matter of importance, riot only for the immediate district, but for the desert region of Southern California in general, where many mines exist having in the oxidized belt conditions that, in many respects, resemble those in the Exposed Treasure mine. The deposit is situated in an apparently isolated butte about 2.5 miles south from the town of Mojave, on the Mojave desert. The butte, though apparently isolated, is in Fact geologicallg part of an extinct volcano, known as Soledad butte, which rises out of the plain 1.5 miles SW. of' the mine, to an altitude of 4,650 ft. above sea-level. Other buttes also rise from the desert plain toward the south and east, and again to the westward, all being closely related geologically to Soledad butte,—the whole constituting a single system as to origin and time. Since the end of the period of active volcanism in this region, there has been extensive denudation, the ancient plateau having been dissected during an epoch of apparently exces-

Jan 1, 1908

By Robert A. Field

Static-Load Piledriving utilizes a hydraulic push to facilitate the installation of a pile. The pile is not rotated, impacted or vibrated. A smooth pushing force advances the pile incrementally into the ground. Static-Load devices must have a reaction mass to push against. The most simple form of a Static-Load device is a jack; more advanced equipment, such as the Still Worker, also utilizes this approach. This paper focuses on the use of the Still Worker on three challenging projects. In each case, the existing site conditions made it risky, or unattractive, to utilize conventional impact, vibratory, or drilled-shaft equipment.

Jan 1, 1997