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By Gerhard Mücke

Geothermal and operational reasons in the German coal mining industry make it necessary to an increasing extent to climatize coal faces and headings by means of refrigeration plants. Air coolers installed on coal faces as well as in gateroads play an important part in such climatization. They must transfer, under difficult conditions, the refrigerating capacity supplied by central or de-central refrigeration plants from the chilled water to the air in the workings. The performance data of two new types of coalface coolers and of two different types of gateroad coolers were measured in two testing stations under different thermo- dynamic conditions with dust-free fresh air. As air coolers must be installed particularly at working points with a high .dust load the heat exchanging surfaces are fouled for the most part causing an essential reduction of the refrigerating capacity. The investigations therefore were extended to measurements with a certain dust load in the intake air of the coolers.

Jan 1, 1980

By Klaus Beckmann

Gentlemen : My object reads "Longwall Rapid Advance of Coal Mining in the Federal Republic of Germany". It is true that the percentage of coal obtained in your country from longwall faces, with at present 1.2, is still rather low, but it increased considerably since 1966 with 0.4 %. The coal mines of the Federal Republic of Germany ever used longwall as the classical method of coal getting. All attempts to introduce bord and pillar mining did not lead to any wider application of this method. The principal reasons, for this appear to have been: - the deeper depth of our workings, - the wish to keep working losses as low as possible and to utilize the deposits opened up by deep and therefore expensive shafts to the furthest possible degree, - the dense sequence of seams and the mutual influencing of the working points, - the high number of disturbances in the geologically much stressed deposits, - and the necessary considerations to the protection of the densely built-upon surface.

Jan 1, 1970

By R. Schuerch, C. Cimiotti, M. Piemontese, N. Karlin, P. Perazzelli, P. Halton

The new Los Angeles, California JWPCP effluent outfall tunnel will transport secondary-treated effluent from the Joint Water Pollution Control Plant in Carson to White Point Manifold. The tunnel will be approximately 7 miles (11 km) long with a finished internal diameter of 18 ft (5.5 m). The TBM is designed to cope with high water pressure up to 10 bar. The geotechnical challenges are due to the heterogeneous subsurface conditions: in the first half of the alignment, the tunnel runs through soils with a low overburden under urban areas, and, in the second half, the tunnel runs through extremely weak, intensely faulted rock masses with high overburden. Following an overview of the project, this paper focuses on the northern portion of the alignment and presents a decision-making procedure developed during pre-excavation phase in order to cope with the expected heterogeneous conditions during mining. The risk assessment and the TBM operational design of the southern portion will be dealt with in a future paper.

Jun 13, 2023

By W. S. Fyfe, R. J. Puddephatt, S. Zhou

Gold is easily mobilized at temperatures within range 600-11OO°C by gases such as Cl2, CO, H2S, in gas mixtures, at low pressures. Such gases are relevant to conditions of granulite facies metaomorphism in environments of magma underplating. These observations suggest an efficient mechanism for moving gold to the upper crust during major thermal events. The efficiency of precipitation of gold at lower temperatures is related to available mineral surfaces and pyrite appears to be an excellent substrate for gold precipitation.

Jan 1, 1989

By J. Morris, R. Sellaro

Petro-diesel is a common collector for coal flotation, but the partitioning of diesel range organics (DROs) in process streams has not been widely studied. Preliminary research suggested that under normal dosing schemes total residual DRO contents in process waters should be limited to the sub-ppm water-soluble fraction (WSF). Further, polycyclic aromatic hydrocarbons (PAHs) should partition proportionately with DROs. The purpose of this study was to confirm these findings in laboratory flotation tests. Total DRO and specific PAH contents were measured in the waters associated with the concentrate and tailings streams. The results show that concentrate waters consistently had higher amounts of DROs than tailing waters. Moreover, the DRO contents in both streams generally increased with increasing diesel dosage. In line with preliminary research, DROs appeared to be limited to the WSF, and PAHs tended to partition proportionately with DROs. Under typical operating conditions, it appears that residual DROs should not present an environmental concern, but conditions should be avoided that allow significant overdosing of diesel.

Jan 1, 2014

By P. M. Godinho

The debut of the sustainable development concept in the political arena, and the publication of Our Common Future in 1987, represents the starting point of present concerns and efforts associated with the sustainability of the ecosphere and its ecological and human subsystems. The sustainable production and consumption of natural resources, in particular mineral resources, represents a central aspect of the problem. In this context, an important goal has been to develop sophisticated management systems, which consider sustainability principles, in organizations within the system of minerals and metals (SMM). The development of indicators is only part of this challenge. The extractive industries (EI) as an important stakeholder of the SMM (should) have similar priorities. If embraced, this challenge offers great opportunities, one of them being the potential for advancing the understanding of how these organizations learn and change. The identification of its main determinants offers, in theory, the possibility for their management and a faster achievement of the sustainability levels to which they (should) aspire.

Jan 1, 2007

By Fernando de Oliveira Durão

A complete computer package for the steady-state simulation, either in analysis or in design mode, of mineral processing flowsheets is described. The main features of the simulation package are: modular architecture, flexible structure and sequential solution strategy. Different detail levels of mathematical models of several mineral processing unit operations have been developed and implemented as unit modules (FORTRAN routines). Unit operations currently modelled are: coarse/fine crushing, grinding, screening, hydrocyclone classification, gravity separation, heavy media separation, froth flotation, high gradient magnetic separation and solid-liquid separation. In design mode, a simulation study is stated as a general non linear optimization problem. The objective function is a weighted sum of square deviations between the design specification set points and the calculated values, subject to non linear equality and inequality constraints. The optimization problem solution is obtained solving successive Quadratic Programming subproblems followed by inexact line search of an exact penalty function (Powell algorithm). One non trivial example is discussed, illustrating the design capabilities of the simulation package.

Jan 1, 1992

By D. M. S. Bhatia

Twenty-six insitu analyses of cubic galena crystals from a Mississippi Valley-type deposit were undertaken with a laser microprobe spectrograph to study the variation of nine trace elements from the crystal center to its periphery, both along the diagonal and vertical. The general trend is an increase in the concentrations of Ag, Ga, Ge, and In with As showing the opposite trend Bi, Cd and Sn did not show any pattern. Sb was not detected. These variation patterns nay serve as a model for similar studies of other Mississippi Valley-type deposits.

Jan 1, 1984

By Donald E. Hulse

Selection of a block size for a computerized 3 dimensional ore body model is an exercise in compromises. Larger blocks decrease the use of computer resources and decrease the variance of the block estimates. Smaller blocks increase the resolution of the model and the selectivity which can be used in the planning, but increase the variance of estimates in the individual blocks. A common rule is that blocks can be as small as one fourth the average sample spacing, however this ignores the interrelationship between the block size, the sample spacing, and the variogram model. This paper will explore this relationship Kriging estimation variance will be used as a comparative measure of estimate quality. Graphical techniques will be used to show that there is a point where smaller block sizes cease to contribute to the resolution of the model. A method of evaluating the consequences of block size decisions will be examined.

Jan 1, 1992

By John Jonkman

Two major changes occured during the last 5 years in the applications of computers. First, the cost of computer equipment decreased drastically in an era of high inflation. Second, technological breakthroughs in hardware and software have been applied successfully so that the average person can successfully utilize the computer without having to be a computer expert himself. The mining industry has recognized that computing technology has evolved to a point where it can be applied successfully to assist in improving productivity. Since equipment downtime is one of the major reasons for lost production, the Kennecott Minerals Company has developed a comprehensive maintenance information system which now assists the maintenance department in minimizing equipment downtimes. This paper discusses the primary features and functions of this system, the state-of-the-art technology that has been applied, and the benefits that resulted from using this system. Programs to support mobile equipment maintenance scheduling, which currently are under development, are reviewed and a summary of future applications is given.

Jan 1, 1982

By A. K. Ghose

The increasing application of roadheading machines in the coal industry has prompted the development of an appropriate selection methodology for such machine applications in specific locales. Accurate geological sections and comprehensive rock testing are required for all machine tunneling. Using suitable geotechnical parameters and index tests, sensitive both to excavability and standability of the strata, a classification scheme has evolved to help evaluate the rock mass vis-a-vis application of a given weight-class of roadheading machine. The classification parameters include point load index, brittleness, abrasiveness, average crack density, and ground water, which with assigned numerical ratings, lead to a quantitative global rating of the rock mass. For each rock mass class, the selection of an appropriate roadheading machine is recommended. The paper illustrates the application of the rock mass rating system and also describes simple index tests for evaluating the classification parameters for brittleness and abrasiveness. Manuscript not received in time for publication.

Jan 1, 1983

By Bob Katsiouleris

Having passed through the worst of times for industrial minerals demand, there are signs that the best of times lie ahead. If the downturn was the result of unsustainable economic policy, the path forward has everything to do with sustain-ably meeting the demands of more people enjoying higher standards of living than ever before. Minerals producers must be poised to understand and meet their requirements well into the next decade. Successfully marketing industrial minerals - the building blocks of a growing and increasingly urban world population - will depend on producers? ability to respond nimbly to a rapidly changing and regionally evolving macroeconomic environment. A renewed focus on energy conservation, sustainable agriculture and building practices and consumer demand for products with a smaller environmental footprint will drive product and market segmentation strategies. These trends will not only shape the way industrial minerals producers do business, but also the type of skills and people they will require to run those businesses.

Jan 1, 2011

By J. Morris, R. Sellaro

El petrodiesel es un colector común para la flotación de carbón, pero la partición de compuestos orgánicos de diesel (DRO por sus siglas en inglés) en corrientes de proceso no ha sido ampliamente estudiada. Investigaciones preliminares sugieren que bajo esquemas de dosificación normales los contenidos residuales totales de DRO en aguas de procesos deben estar limitados a la fracción soluble en agua (WSF por sus siglas en inglés) sub-ppm. Es más, los hidrocarburos aromáticos poli-cíclicos (PAH por sus siglas en inglés) debería segmentarse de manera proporcional con los compuestos orgánicos de diesel (DRO). El propósito de este estudio fue confirmar estos resultados en pruebas de flotación realizadas en laboratorio. Se midieron los contenidos totales de DRO Y PAH en aguas asociadas con los flujos o corrientes de concentrados y relaves. Los resultados muestran que las aguas con concentrados tenían de manera consistente mayores cantidades de DRO que las aguas de relaves. Es más, los contenidos de DRO en ambos flujos generalmente se incrementaban con el aumento de la dosis de diesel. De acuerdo con la investigación preliminar, los DRO parecían estar limitados a la fracción soluble en agua (WSF) y los PAH tendían a segmentarse proporcionalmente con los DRO. Bajo condiciones de operación típicas, los DRO residuales no deberían representar una preocupación medioambiental, pero deben evitarse situaciones que permitan una sobredosis significativa de diesel.

Jan 1, 2014

By R. Patterson

Tracer gas sampling methods are useful for monitoring ventilation systems, especially in remote or inaccessible areas, and can be utilized for analysis of the ventilation system immediately following a mine emergency. However, the success of this technique is largely dependent on the accuracy of release and sampling methods. Analysis of sampling methods is crucial for rapid response and dependable results during emergencies. For the purpose of this study, four well-accepted sampling techniques currently used in the mining industry were compared using solid-phase microextraction (SPMe) fibers with sulfur hexafluoride (SF6), an industry standard, as the tracer gas. Current sample collection techniques include plastic syringes, glass syringes, Tedlar bags and vacutainers. SPMe fibers are used in a variety of industries, from forensics to environmental sampling, and are a solventless method of sampling analytes. To analyze these sampling methods, samples were taken from a 0.01 % standard mixture of SF6 and nitrogen and analyzed using electron capture gas chromatography. A relative standard error of less than 10% validated results to compare the accuracy of various methods. The technical and practical issues surrounding each sampling method were also observed and discussed.

Jan 1, 2011

By D. E. Ranta, G. H. Giroux, A. W. Randall, D. A. Barr

Zinc-lead ores of the Pine Point District, Northwest Territories, Canada, are hosted in paleokarst cavities within a Middle Devonian carbonate barrier complex. Of the nearly 100 deposits found, most are irregularly distributed along two main regional stratigraphically controlled trends. The ores, which occur predominantly as open space filling, form deposits most of which average one million tonnes in size with an average grade of 10% combined zinc plus lead. Geological features related to karsting control not only distribution of deposits but also their shape, size and grade. The higher grade ore in these deposits generally occurs in a relatively small core area. Consequently, accuracy of reserve estimation is dependent on drill-hole density and understanding of karst geometry. Several case examples will be reviewed to demonstrate the relationship between shape, size and grade of deposit, geological reserves and drill-hole density, along with a discussion of geological ore reserve estimation methods.

Jan 1, 1992

By E. A. Domínguez

Kaolin deposits of Patagonia (Argentina) were formed by ?in situ? alteration of volcaniclastic rocks or by erosion, transportation, and deposition of residual clays in small basins. The mineralogy, geochemistry, grain size distribution, and specific surface area of natural and washed kaolins were studied in order to point out the relationships with the ceramic process. Primary kaolins are coarse-grained, kaolinite+quartz±halloysite, with a very low specific surface area. Sedimentary clays are either kaolinitic?smectitic and very fine-grained or kaolinitic with a coarser particle size distribution. An interdependence between mineralogy, chemistry, particle size distribution, texture, surface activity and ceramic behavior was found. Plasticity is strictly dependent on surface activity and expandable clay minerals. Slip rheology is affected by soluble salts, smectite, and tubular halloysite. Kaolinite-halloysite play an opposite role versus smectite-I/S in slip casting and tile pressing. Kaolinite and quartz are beneficial for drying behavior while expandable clay minerals increase drying sensitivity. Firing behaviour is mainly affected by minor components supplying fluxing oxides.

Jan 1, 2010

By John S. Lagarias

When ore bodies are faulted or mill feed turns refractory, mining managers and engineers act vigorously to convert imminent failure into eventual success. The recent proliferation of onerous "environmental" regulations and restraints is likewise a threat to successful mining enterprise, in some ways more insidious and dangerous than the problems presented by natural obstacles. The regulatory burden has become so heavy that a pall of pessimism covers much of the mining enterprise. In this paper we frankly recommend a Pollyanna approach, making not just "the best of it" but directing the whole environmental process: first, to improve our planning, engineering, and operating procedures; and, second, to demonstrate the need for modification of laws and regulations which are intolerably burden-some to both the mining industry and the public. It is customary for government officials and environmentalists to point out how great are the new environmental regulations and how successfully these have improved the natural environment in particular and the quality of life in general.

Jan 1, 1978

By D. Pappas

Over the past decade, the number of contractors working in underground coal mines has nearly doubled; however, the effect this has had on the industry's injury rates has been the subject of much speculation. The confusion exists because the U.S. Mine Safety and Health Administration (MSHA) database does not assign contractor hours to the individual mining operations where they worked. To better understand the safety record of the contractor segment of the industry, the National Institute for Occupational Safety and Health (NIOSH) undertook a comprehensive analysis of the data contained in the MSHA database. The first part of the study compared overall contractor and operator trends from 1983 to 2009 related to employment, hours worked and injury rate. One unexpected finding was that the larger contractors tended to have higher injury rates than the smaller ones. The second part of the study directly addressed the role of contractors on the safety record of 10 large underground coal mines. A detailed analysis provided both injuries and estimated contractor hours worked at these mines for the period 1992-2007. Comparison between the estimated contractor injury rates and the reported operator injury rates at these mines indicated that the contractor injury rates were significantly higher at most of the operations studied. However, the industry-wide data indicates that contractor and operator injury rates have converged since 2005 and are now equivalent. Mining Engineering, 2011, Vol. 63, No. 11, pp. 73-79. Official publication of the Society for Mining, Metallurgy and Exploration, Inc.

Jan 1, 2011

By Joseph K. Cavey

To accommodate the new Pier A expansion at BWI airport, a 1.8 m (6.0 ft)diameter stormwater pipe was constructed below active Runway 15R-33L. The jacked tunnel alignment runs east/west below the runway, and the depth the crown was 6.1 m(20 ft). Soil conditions consisted of very loose to medium sand and gravel, with some medium stiff clay and silt. Super Jet Grouting was selected as the ground treatment system, creating large diameter columns. All work was performed from the surface of the runway between the hours of 12 am and 6 am. Monitoring points along the tunnel in the grout zone indicated zero settlement during tunneling. Tunneling operations in front of and beyond the treatment zone experienced significant settlement. Super Jet Grouting in the treatment zone provided a low permeability continuous stable soilcrete that was readily mined while the runway remained in service.

Jan 1, 2003

By William Petruk

Performance assessments are carried out to monitor operations, to evaluate performance and to identify processing problems. The assessment involves collecting and analyzing representative samples from critical points in a flowsheet and interpreting the data. Sample analysis techniques include chemical analyses, mineralogical investigations, mineralogical analyses, and materials balancing. Chemical analyses provide the lowest cost assessment and should be used liberally, particularly in monitoring a process. Materials balances performed on chemical assays for a suite of samples are used as a first step in evaluating a process. Mineralogical investigations are more expensive than chemical analyses but need to be used only at the beginning of mining and metallurgical operations and as a second step in assessing processing problems. Quantitative mineralogical analyses combined with materials balancing provide the most complete performance assessment, but the procedure is expensive. On the other hand, the assessment has the potential of a large payback when carried out where warranted.

Jan 1, 1991