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Coal that meets customer specifications is often stored in silos prior to being loaded into railcars. However, it is often found that, after loading, the coal contained in a particular car does not meet customer specifications. This can occur because of the variability inherent in the coal and because of segregation, mixing and flow inside the silo. Some contracts now require the coal in each car to be within specification. Silo flow models are used to predict quality in such cases. However, developing an accurate silo flow model for each case is difficult and time consuming. This paper examines the viability of using an online analyzer in conjunction with a feedback circuit to optimize the quality of the coal being loaded into trains, so that each car meets the quality specifications.

Jan 1, 2002

By R. E. Weeks, D. J. Millenacker

Utilization of true in situ technologies for mining copper in Arizona will involve a complex environmental permitting process. This process is a key factor in determining the feasibility, costs, and implementing time- frames required for development of this innovative mining method. The regulatory structure in Arizona is presently changing due to enactment of the Environmental Quality Act (EQA) of 1986 and development of new aquifer protection rules and regulations. The US Bureau of Mines has reviewed the comprehensive hydrogeologic characterization, ground water monitoring, mechanical integrity testing, well construction, contingency planning, and other regulatory elements that will serve as mechanisms to assure protection of ground water resources. The purpose of this paper is to inform the domestic copper industry of the significance of the new Arizona regulatory structure and its implications for prospective in situ operators.

Jan 1, 1987

By K. J. Stratford

The selection of a suitable mathematical function for the modelling of the partition curve for dense medium cyclones is discussed. Five alternative functional forms (based on three basic functions) are compared using data obtained in the course of an extensive experimental study of a 610mm dense medium cyclone. It is shown that, for adequately sampled tests, any of the functions may be used, although a function based on the Weibull distribution is shown to be most suitable. Where data are poor, all functional forms exhibit disadvantages, notably in terms of a reduction in precision of parameter estimation. This problem can be exacerbated by the complex numerical techniques required to estimate the parameters of a particular function. A set of ideal requirements for a performance function are presented.

Jan 1, 1986

All coal preparation unit operations in which fine coal is handled depend to some extent on wettability of coal surface by water. The wetting results from interactions between the coal surface and water molecules that are determined by the composition of coal matrix (interrelated with coal rank) and heterogeneous constituents such as oxygen functional groups, mineral impurities and pores. The contact angle of water on an unoxidized, homogeneous coal hydrocarbon matrix is calculated to be 100o, and much lower values measured on real coal specimens result from contributions from the heterogeneous constituents. While the effect of wettability is critical in flotation and oil agglomeration, suppression of respirable dust, and coal water fuels, it has been shown to play a significant role also in coal flocculation with semi-hydrophobic and totally hydrophobic flocculants.

Jan 1, 1995

By T. Yegulalp, K. S. Lackner

Zero emission coal plants capture their own CO2 emissions. Since they have no smoke stack, they emit no pollutants to the air. Zero emission plants circulate a gas stream, to which fresh fuel is added and from which spent fuel and impurities are removed as solids or liquids. Coal is gasified via hydrogenation, steam reforming or CO2 gasification (Boudouard reaction). The gas is oxidized in a fuel cell and the resultant water and CO2 are partially removed before returning the remaining gas to the gasifier. The high conversion efficiency of zero emission power plants, which exceeds 70% even in realistic designs, stems from combining fuel cells with careful heat management. The paper generalizes the concepts and outlines the thermodynamic basis of zero emission power plants.

Jan 1, 2004

By Barry T. Kilbourn

Yttrium Oxide is versatile; it is essential for television phosphors, for microwave garnets, for laser crystals and for high-performance ceramics, to name but a few advanced applications. When produced commercially, the material must satisfy not only stringent specifications regarding chemical purity but, increasingly, also meet closely defined physical parameters. The techniques needed for its production range from solvent extraction to carefully controlled precipitation and calcination. The processing steps from mineral concentrate to pure oxide will be described and related to the final oxide. The simple word "material" has complex connotations; it means, to paraphrase "Alice", exactly what we want it to mean. Throw in the label "advanced" and the picture darkens further! Just what is an advanced material and how does it differ from a common-or-garden material?

Jan 1, 1990

By Wei Wu

A computer-aided method for optimization of bench blast design in surface mines is presented. The design procedures basically consist of two steps. Firstly, a series of normalized, full- scale bench crater tests must be carried out in the field to find the optimum burden that produces the largest amount of acceptable fragments and other parameters that defines the effective fracture zone. Next, the locations and initiation sequence of blast-holes will be determined in such a way that each hole, at its time of firing, will be responsible for same amount of burden rock and will be in a position favorable to effective fracture of burden rock. A computer software "B.B." which can assist the second step of the design is fully introduced and its application is illustrated by an example.

Jan 1, 1992

By S. Ouyang

The four most important parameters controlling the flow of as in coal are the gas content, permeability, diffusion coefficient and clear characteristics. Estimates of these and, more importantly, a good knowledge about the variations in their values over time are important for proper simulation of long-term gas production. This paper describes experimental techniques for the estimation of diffusion-coefficient and permeability values, along with their time dependency under simulated in situ conditions. It is shown that the permeability and diffusion-coefficient values are not constant, as they are usually assumed to be. There is a significant variation in their values, probably as a result of changes in the microstructures of coal associated with release and flow of gas. Finally, a technique to estimate clear parameter is presented.

Jan 1, 1997

By C. F. Bonney

Spherical or oil agglomeration has been recognised for many years as a possible process for the recovery of mineraVmetal values. BP has investigated the potential of spherical agglomeration for a number of minerals as have other workers. Testwork has also been carried out by both BP and others on the selective agglomeration of fine coal. The spherical agglomeration of both minerals and coal depends on the use of an immiscible liquid e.g. a hydrocarbon which is added to a suspension of the solids in water. On agitation the oil is distributed over oleophilic/hydrophobic surfaces and particle impact allows inter-particle liquid bridges to form causing agglomeration. It is also possible to enhance the oleophilicity of the material to be recovered by the use of collectors similar to those used in froth flotation.

Jan 1, 1998

By Kotaro Ohga, Gota DEGUCHI, Kiyoshi HGUCHI

The situation of Japanes coal mine is in the severe enviroment, because the policy on coal mining has changed. Every year one or two coal mines will be foced to close. To continue the production of coal, we have to reduce the cost of production. Therefore, the mining by longwall method which is more than 250m was attempted at Taiheiyou Coal Mine to reduce the cost and this mining method have had successful results. To get successful results by this mining method, the controlling and prediction of gas emission from the longwall panel will be most important things. In this paper, the comparison of the predicted gas emission from the mining panel based on the measured gas content by using new device with the observed results is described.

Jan 1, 1993

By Bok-youn Kim

Presently, mobile diesel equipments contributes a lot in improving the economical feasibility of underground mining and tunneling operations. Even in Korea, quite a large number of diesel equipments is being applied to the underground workings already. This paper introduced the production procedure, characteristics and evaluation technology on diesel particulate matter(DPM) that is known as a carcinogen For easy measurement of DPM using laser dust monitor, the conversion factor(K) to gravimetric concentration was acquired. The field measurement of DPM was conducted to make a comparison between locally manufactured on-road equipments and imported equipments specially designed for underground use. According to the Government regulation revised h 1996, it was learned that the critical pollutants among the diesel exhaust is DPM instead of NOx which have been considered as a critical pollutants.

Jan 1, 1997

By Denise Herzog, Sukumar Bandopadhyay

This paper presents an application of analytical hierarchy pro- cess (AHP) to predict the ranking of three beneficiation methods for a low grade, bulk gold deposit located in the interior Alaska. Seven criteria (attributes) were used for evaluating each beneficiation method. For each criterion a matrix of pairwise comparison between methods was developed. The normalized eigenvector of each matrix scales the beneficiation methods with regards to that criterion. An overall scale is constructed by weighting the scales of all the criteria. Methodology used also indicates a measure of inconsistency. This measure is useful in identifying possible errors in expressing judgments as well as actual inconsistencies in the judgment themselves. The outcome of the pro- cess is the best or optimum beneficiation method, considering all the necessary objectives, criteria, and alternatives in a single integrated framework.

Jan 1, 1996

By W. M. Shaver, R. Letourneau, W. R. Dengler

Dynatec Mining Limited contracted to sink a 1500 metre (4960 ft.) concrete lined shaft for Falconbridge Nickel Mines in Sudbury, Ontario, Canada. The shaft is 6.3 metres (20.5 ft) in diameter inside the concrete lining and is equipped with steel furnishings. Dynatec used the owner supplied 4.6 metre (15 ft.) diameter double-drum hoist to sink the shaft with 12.5 tonne buckets for muck removal and 4 cubic metre concrete buckets for concrete placement. One of the unique features of the shaft sinking operation is the use of a four-boom electric hydraulic drill jumbo permanently mounted in the shaft sinking stage. This paper will describe the performance obtained with the electric hydraulic drilling equipment and the high capacity muck removal and concreting equipment.

Jan 1, 1991

By Leo Langland

One of the primary functions of the Geotechnical Services-Materials section of the Arizona Department of Transportation (ADOT) is locating, sampling, and evaluating potential aggregate deposits throughout the State. This information is essential in designing, estimating, and bidding highway construction projects. The nature of materials used for aggregate varies greatly within Arizona. The northeastern or plateau section is famous for its scenic sedimentary formations that are, how- ever, too soft to make suitable aggregate. Volcanic materials are widely used in place of more conventional geologic units. In contrast, the southwestern, or Basin-and-Range section, contains a relative abundance of good aggregate, especially a diversity of gravels. The paper will review the off ice, field, and laboratory methods used by the ADOT Materials Section in satisfying its needs for aggregate information in Arizona.

Jan 1, 1987

By Margaret Armstrong, Chris Roth

One advantage of kriging is that it provides both an estimate of the block or point grade, and an indication of the local precision via the kriging variance. If one assumes that the estimation errors are normally distributed, then confidence intervals for the grades can be calculated. But in mining, grades are rarely normally distributed; in general, they are skew. This is particularly true for precious metals. In this paper we study confidence intervals for variables with non-normal distributions. Using a non linear geostatistical technique, the grades are transformed into their normally distributed equivalents. Confidence intervals are obtained for these normal variables, and back transformed to give the corresponding confidence intervals for the grades, for either points or blocks. This approach is applied to gold data from the Witwatersrand basin in South Africa.

Jan 1, 1996

By P. Somasundaran, Brij M. Moudgil

All the major interfacial technologies encountered in mineral processing involve adsorption of surfactants and/or polymers. With the need for processing low grade complex ores it is imperative that conventional techniques such as flotation and flocculation be extended to meet the challenge of treatment of fines. Addition of surfactants or polymers is indeed not limited to the solid-solid separations but extends to particle size reduction in the form of grinding aids and dewatering operations as well. Although progress has been made in recent years to understand the science involved in various interfacial processes, more challenges and opportunities exist today than ever before in processing of the low grade finely disseminated ores. A brief review of the recent advances and the challenges in mineral processing, especially, those related to the interfacial technologies is presented.

Jan 1, 1989

By C. K. Blair, V. J. Hucka, E. P. Kimball

In central Utah, a coal mining operation is taking place under an 0.5-m (20-in.) pressurized natural gas pipeline. The room-and-pillar method with pillar extraction is being used to extract the coal from the seams. The pillars beneath the pipeline will not be extracted; however, there is a possibility that some subsidence may occur due to pillar failure. To assess possible damages on the pipeline, an attempt has been made to predict subsidence in the area where pillars may collapse. The resultant values of subsidence strain and slope have been used to determine the magnitude of strain, stress, and shear induced in the pipeline. Also, a network of survey points has been installed along the pipeline to detect ground move¬ment that would indicate excessive subsidence.

Jan 1, 1987

By Julie Mitchell

The U.S. Bureau of Mines is conducting research on the application of expert sys tens technology to mining equipment diagnostics and predictive maintenance, to increase mining productivity and efficiency. One of the greatest hindrances to mining productivity is the breakdown of equipment, causing lengthy and costly delays. A diagnostic maintenance expert system (DIMES) is being developed for the hydraulic system of a continuous coal mining machine. Through the use of such a system, the frequency of equipment failures and repair time should be significantly reduced. This paper describes the application domain, the functional requirements, and the problem approach for DIMES, the design and implement at i on of the knowledge- based system, the sensor work involved with the project, and the future plans for the continued development of this and other expert systems.

Jan 1, 1989

By A. Mehmet, W. A. M. te Riele

A pilot-plant investigation in a NIMCIX contactor has shown that activated carbon can extract more than 93% of the gold in return-dam solutions. The average gold concentration in the barren solution was less than 0.003 mg/L from a feed averaging 0.048 mg/L. The carbon was eluted by the Zadra procedure. The operating conditions of the elution-electrowinning circuit are reported, and the elution of the gold and other metals is discussed. The reactivation of the carbon by use of the Rintoul kiln is described, together with the results of reactivation. The consumption of reagents in the process cycle is presented in sufficient detail to allow the economic viability of this technique to he evaluated for the recovery of gold from low-grade solutions.

Jan 1, 1990

By E. F. ‘Pat’ Nelson, Richard Broom

Our portion of this afternoon’s session is dedicated to the operation of automatic process control associated with small to medium size primary or SAG milling circuits. In recognition of the subject matter of this symposium, specifically precious metals, our historical reference is Rosario Dominicanna in the Dominican Republic, one of the largest gold producers in the Western Hemisphere. Plus a backward glance to review very briefly the initial performance of the big primary mills at Island Copper in British Columbia and Pima IV in Arizona. We will then get to the subject at hand with a discussion of a retrofit control logic recently installed on a 5000 hp primary mill. The focus of this review is the simple, inexpensive, and cost effective character of this retrofit installation.

Jan 1, 1984