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By Richard Klimpel

The laboratory ball mill grinding of coal/water slurries is described for three coals. Emphasis is placed on the measurement of specific rates of breakage for various operating conditions. Corresponding rheological information is also presented based on data collected using a rotational viscometer. A rheological explanation of the influence of various slurry fluidity conditions on the specific rates of breakage is presented. This rheological approach has proved useful In both the identification of suitable chemicals for increasing breakage rates in coal/mineral slurry grinding and in the plant scale implementation of dense slurry grinding systems.

Jan 1, 1982

By K. B. Rojiani

Surface mining activities disturb large tracts of land resulting in the potential for greatly increased downstream sediment loads. The Surface Mining Control and Reclamation Act of 1977 places increased emphasis on the protection of the environment from the adverse effects of surface mining operations. Surface mining activities must be planned to minimize disturbance to the hydrologic balance, erosion and sediment contributions to receiving streams. Sediment ponds must provide a sediment storage volume equal to the accumulated sediment volume from the drainage area as determined by the Universal Soil Loss Equation (USLE) or other empirical methods established by the regulatory authority. It has thus become extremely important for the mining industry to secure more accurate estimates of potential erosion losses and sediment yield. Accurate estimates of sediment yield are required for the planning, design and successful operation of sediment control systems such as detention ponds and other alternative control structures and for evaluating the effectiveness of land management practices. The principal soil loss prediction procedure available for use is the LISLE. The USLE procedure is inadequate for use in predicting soil loss from surface mine regions for a number of reasons. These include: 1. The USLE was developed to estimate average average annual loss from agricultural soils. It cannot predict accurately soil loss for specific storm events. In surface mine regions a major portion of the soil loss occurs during the initial six months to one year of active mining. Accurate estimates of soil loss over short periods are thus required for the design of control structures. 2. The slope length and gradient factors used in the USLE were obtained from data or cropland having slopes ranging

Jan 1, 1983

By Omotayo Kalejaiye

The Siwek 20-L chamber is widely used throughout the world to evaluate the explosibility of dusts. This research evaluated the quality of dust dispersion in the Siwek 20-L chamber using Pittsburgh coal, Gilsonite, and purple K dusts. A Pittsburgh Research Laboratory (PRL) optical dust probe was used to measure optical transmittance through the dust cloud at various locations within the chamber. A total of 540 tests were performed, with triplicate tests at five nominal dust concentrations and six locations. The two standard dispersion nozzles (rebound and perforated annular nozzle) were compared. The transmissions corresponding to the normal ignition delay period were used to: (a) determine variations in spatial uniformity of dispersion obtained with both nozzles; (b) make comparisons between the experimental transmission data and those calculated from theory for the three dusts; and (c) make comparisons with transmission data measured in the PRL 20-L and Fike 1-m3 dust explosion chambers. The uniformity of dispersion for the three dusts was similar with both nozzles, despite the differences in nozzle geometry and mode of operation. Transmission data of the three dusts were all significantly lower than those calculated from theory. This was discovered to be, in part, due to significant reduction in particle size that occurred during dispersion. By measuring particle sizes before and after dispersion, values of 60%, 50%, and 20% reduction in particle size (based on the surface-weighted mean diameter) were obtained for Pittsburgh coal, Gilsonite, and purple K, respectively. Transmission data from the PRL 20-L, Fike 1-m3 and the Siwek 20-L chambers indicated comparable results in terms of uniformity of dispersion. However, transmission data from the Siwek 20-L chamber were significantly lower than those of the PRL and Fike chambers. Again, this was attributed, in part, to the significant reduction in particle size that occurred during dispersion in the Siwek chamber. The design of the outlet (dispersion) valve of the Siwek 20-L apparatus charge vessel was largely responsible for the particle break-up. The contribution to particle break-up by the dispersion nozzles and the high level of turbulence in the chamber were found to be minimal. This is a significant finding in that the dust particle size tested for explosibility in the Siwek chamber is considerably smaller than the original dust sample.

Jan 1, 2010

By Douglas Kathol

Coal in the 1990?s Exit of the integrated oil company [Shell Arco Mobil Exxon Mapco Kerr McGee Hansen Nerco Sun] Continued decline in coal prices Significant mergers & acquisitions (M&A) activity ?Most properties traded, some twice ?Significant consolidation ?Massive recapitalization ?New industry leaders ?Frustrated expectations

Jan 1, 2002

By D Lautier, A A. Ndiaye, A Galli

Traditionally gold producers had built up hedge books to protect themselves against adverse changes in the commodity price, but diversified mining groups were staunchly opposed to hedging in any shape or form. The situation has evolved over the past few years. Gold miners have been reducing the size of their hedge books in line with the rising gold price. Commentators have talked about ædouble-digit dehedgingÆ and have suggested that this is the final countdown for gold hedge books. It sounded as if the era of hedging by mining companies was drawing to a close. But as appearances can sometimes be misleading, we decided to find out what mining companies were actually doing. Companies listed on stock exchanges are now obliged to give details of their derivatives holdings in their annual reports. Two or three years ago there was no such obligation. Our reality check was based on the latest annual report issued by three multinational mining groups; two with diametrically opposed views on hedging (Rio Tinto and Barrick) and the third (BHP Billiton) with an intermediate position. This snapshot of their derivative positions at a point in time revealed that Barrick and BHP Billiton have substantial derivatives positions (worth billions of dollars) to protect against adverse changes in foreign exchange rates and interest rates. Moreover Barrick has recently started hedging against increases in fuel prices. Despite its opposition to hedging, Rio Tinto has derivative positions worth several hundred million dollars, but these are primarily a legacy from various mergers and acquisitions over recent years or were entered into as a condition of project financing. Lastly we were surprised to discover that Barrick was holding asset-backed commercial paper (ABCP). So the idea that mining companies donÆt hedge their risks is just another urban myth.

Jan 1, 2009

By D. A. Stout

Mr. Chairman and Members of the Rocky Mountain Coal Mining Institute: Your Secretary has asked me to write upon a subject' which is a most interesting one, and which has a very wide scope. In view of the great need for further decreasing costs at its coal mines, the Colorado Fuel and Iron Company began early in 1924 to experiment with methods of mining which had not previously been. tried out at its mines, and which were selected because of the greater possibilities for the concentration of the work, better grouping of workmen, and increased tonnage per workman, with a resultant increased efficiency, better supervision, and lowered costs. Because of the great competition of the day, means and methods must be provided by which fewer mines can be made to produce larger tonnages and at a lower cost. Western physical conditions are such as to make our problems far more complicated and not so easy of solution as compared to many of the eastern fields where conditions are more favorable for the operation of the mines. The dry condition of our Western mines on account of a relatively low humidity, and with additional gaseous conditions, makes the problem still more difficult to solve. A study of new methods was necessary before adoption, and this was particularly true of the method of extracting the coal. Where mechanical means are used, particularly in the coking coal mines of this state, due consideration must be given to the type, and machines or conveyors should not be installed solely on the basis of their performance elsewhere, without the knowledge of local influencing factors. In trying out the newer methods of extraction at our mines, very careful consideration has been given to the question of safety and the adoption of any new methods must provide adequate means of protection to employes, and be approved by' the State Coal Mine Inspector. In any large industry there are a few outstanding operating costs, and usually the leading ones in their order are labor cost, material cost, and power cost. The things which we, hope to accomplish: 1. Reduce labor costs. 2. Reduce material costs. 3. Reduce power costs by the con 4. Reduce the amount of powder used per ton of coal produced. 5. Increase the lump percentage (particularly at the domestic mines). 6. Reduce accidents and annual compensation payment. 7. Reduce haulage costs. 8. Reduce cost for track work. 9. Reduce cost for timber and timbering, and increase the recovery of timber at a considerable additional saving. 10. Reduce the brushing costs. 11. Reduce the amount of rock hauled to the outside. 12. Reduce the cost for drainage. 13. Reduce the cost for ventilating. 14. Reduce cost of inspection and supervision. 15. Reduce the cost for shot firing. 16. Reduction of number of working places. 17. Grouping of men with increased sociability. 18. Increased tonnage per man. 19. Reduction in total number men employed. In the consideration of the methods used and now working successfully, there were three points which were considered outstanding, to make them wholly successful: ventilation, roof control, and transportation. For making the experiments, those mines were selected where conditions

Jan 1, 1925

By I. C. Edwards, G. E. Agar

INTRODUCTION Many research efforts over the past years have been devoted to the study of energy consumption in comminution and the characteristics of the broken material. The old "laws" have been superseded by more general methods of analysis1,2,3 but these methods have not received much attention outside the laboratory. The work to be described here was done in order to obtain scale-up information on wet rod milling of sylvinite. EXPERIMENTAL A 30 x 51 in. Denver rod mill with a scoop feeder was used for these tests. Ore was fed from a variable speed screw conveyor into the feed box along with saturated brine. The mill was filled to approximately 45% of its volume with 2400 lbs of a mixed rod charge. The minimum possible feed rate was 2.5 tph and the practical maximum for this mill was 8 tph. Individual tests were run by setting the solid feed rate, then adjusting the brine flow rate to give the desired pulp density. After steady state, as evidenced by constant discharge pulp density, had been reached, samples of the discharge were taken at 15-minute intervals. These samples were filtered, washed with alcohol, dried, then screened on Tyler screens using a Ro-tap shaker. The sylvinite feed was regular plant feed that had been scalped at 20 mesh and was tapped from the coarse ore bins. It had been previously passed through a roll crusher set at 3 inches and after scalping was essentially minus 1 in. plus 20 mesh. RESULTS The screen analysis of samples from each series of tests was plotted on double logarithmic scale paper to determine the reliability of the series. In some cases, a faulty sample or screening procedure dictated that the results of one test be discarded. The criterion is a simple one — if the slope of one plot was noticeably different from the others in the series, it was discarded. The only cases that caused difficulty were those in which the brine was not thoroughly displaced from the solids. When this occurred agglomerates were easily identified on the screens and the whole of the sample was retained on 3 or 4 screens. There were no border line cases. The number N given in Table 1 is the number of size analyses that were pooled to form the data shown in Fig. 1. While examining the reliability of the sizing and sampling by plotting the data, it became apparent that there was no significant difference between grinds made at 50 and 60% solids. For the analysis given here, these tests were regarded

Jan 1, 1967

By O A. Cottrill, G A. Oldfield, S B. Nowell

Host-rock û wallrock major and trace element geochemistry associated with epithermal gold mineralisation in the Hauraki Goldfield of New Zealand is poorly documented, even though rock geochemistry is a recognised tool in exploration. Such responses assist in recognition of the regional scale imprint of fossil hydrothermal activity, and indicate targets for detailed evaluation within these alteration zones.   Recent investigation of gold deposits in the Waihi (Gladstone), Golden Cross (Empire), Thames (Waiotahi) and Coromandel (Tokatea) areas indicate enrichments of Au, As and Sb in the andesitic wallrocks hosting mineralisation. Of the other elements examined, Si, K and Rb are enriched, and Na, Ca, and Sr are depleted at all deposits. These trends are best developed in the vicinity of veining. In deposits with clay alteration dominating (Waiotahi and Tokatea) there is also depletion of Mg, Mn, Zn and Cu. Ba and Cr are variably enriched or depleted within different styles of alteration. Base-metal enrichment in the wallrocks is not a feature of Hauraki deposits.

Jan 1, 1990

By René G. del Villar, Jules Thibault, René del Villar

"Some key control variables of industrial processes, associated with product quality, often cannot be measured directly or frequently enough to establish adequate control. In such cases, it is possible to use available measurements to provide a prediction for these process variables and use them in a control strategy, thereby giving rise to what is now commonly called a softsensor.In some industrial grinding circuits, the on-line particle size analyzer is shared between various sampling points. Therefore, for a given location, the actual measurement is only available every 10 to 20 minutes, a delay which is unacceptable for automatic control purposes. To alleviate this problem, a softsensor based on an artificial neural network has been investigated. First, the structure of the neural network and different schemes for the training process are analyzed. Then, the performance of the neural network softsensor is compared with other inferential methods such as ARMA models and Kalman filters.IntroductionGRAHM, French acronym of the Research Group on Computer Applications in the Mineral Industry at Laval University, began in 1990 a research project on Knowledge Based Automatic Control (KBAC). This project, sponsored by a consortium of eight mining companies and the federal and provincial governments, seeked to screen advanced (knowledge-based) methods for data processing (filtering, mass balancing, etc) and automatic control (model-based) for their use in the mineral processing operations and the transfer of the project results to the sponsor companies.In parallel to more academic research work, a number of case-studies have been undertaken with the cooperation of partner companies. Among such works, a very successful one has been the design and installation of a new control strategy for one of the Kidd Creek (Falconbridge Ltd.) grinding circuits. This project was related to the evaluation of a number of control strategies and the implementation of one of them, as selected by the plant management, in the concentrator.A total of sixteen control schemes were evaluated on one of the dynamic phenomenological simulators developed at GRAHM, a trademark of this research group [ l]. The calibration of the simulator models was done based on industrial data gathered by GRAHM and Kidd Creek personnel. Then, the simulator was used to test the performance of various PID-based control schemes, designed to achieve the control objectives set by the Kidd Creek personnel. The best scheme proposed called for controlling the cyclone overflow particle size by manipulating the water addition rate to the cyclone feed box and the circulating load by manipulating the circuit ore feed. The particle size analyzer (PSI-200) available for monitoring the product size, was unfortunately shared (multiplexed) among various streams of the plant, which meant a 14 min delay between two consecutive readings for any particular stream. This induced the plant personnel to choose an alternative control strategy, one which controlled the cyclone feed density instead of the cyclone overflow particle size."

Jan 1, 1996

By Scott Rosenthal, David Gilkey, Michael McGivern, Lorri Birkenbuel, Daniel Autenrieth, Ty Murphy, Hadi Aldossari

A safety climate case study was carried out at a surface metal mine where investigators administered the Liberty Mutual Short Scale Safety Climate Survey to 365–368 miners to measure safety climate in consecutive years. Following the baseline safety climate survey in 2019, Foundations for Safety Leadership (FSL) training was conducted with 81 middle to upper management employees at the mine site. Investigators found statistically significant differences in the pre vs. posttraining FSL assessment scores of the middle to upper management employees who attended the training. The follow-up safety climate evaluation was compared to baseline scores and revealed no significant improvement. The overall baseline company safety climate score of 76.38 increased minimally to 76.50 (p-value = 0.616). Investigators also evaluated differences in safety climate between the company’s three major divisions (operations, maintenance, and administration). Both years administration had the highest mean score and operations had the lowest mean score. The authors attributed the statistically significant differences found among the three major divisions to various dissimilarities in their work environments.

Aug 13, 2021

By Dennis A. Long

Slip and fall accidents are a major cause of lost-time injuries associated with large mobile equipment in surface mines. An evaluation of the safety hazards associated with getting on and off large surface mining vehicles showed that most of the accidents occur at the point where personnel attempt to mount or dismount the machine at ground level. The major hazardous design conditions were identified as excessively flexible supports for lower steps or rungs, inappropriate ground-level-to-first-step distances, poor step designs, access designs that use vehicle components as steps or walkways, and inadequate hand- rail and guardrail designs, Additional hazards are introduced by the lack of proper maintenance of ladder hardware and the work practices of operators in carrying articles while mounting and dismounting the vehicle. This Bureau of Mines report describes the design and in-mine testing of improved access system for large mobile mining equipment.

Jan 1, 1984

By L. A. Morley

Electricity is a major cause of lost-time accidents and fatalities in the mining industry. Major hazards and unsafe practices that contribute to electrical hazards are identified in this paper. Recommendations for reducing electrical accidents in surface mining are given and are directed toward the following three areas: preventing equipment contact with overhead lines, preventing maintenance related accidents, and defining system protection techniques.

Jan 1, 1986

By Noel N. Moebs

Bureau of Mines studies of mine roof fall problem in the Pocahontas No. 3 Coalbed of southern West Virgania and southwestern Virginia have established that type and sequence of rock are significant factors in roof competence. The poorest conditions occur where the immediate roof consists of slump structures and slickensided rock. The best conditions occur where the roof consists of a sequence that coarsens upward from shale to massive sandy shale. A small manual of color photographs of rock types was devised to aid in identifying drill cores. Proper identifications should enhance the prediction of areas of potential roof problems in advance of mining.

Jan 1, 1981

By M. S. Klima, V. Choudhry

Coal gasification solid residue (slag) contains unconverted carbon (char) which is considered an impurity for utilization applications of slag. Under this study, table concentration was used to process approximately 24,000 pounds of a nominal -3.4 mm gasifier slag (~85% ash) to separate high (~100%) ash slag from low (~50%) ash char. The results indicated a nearly ideal separation of the slag from the char for sizes coarser than about 1 mm. An overall slag yield of 71% was obtained. The slag was sufficiently clean to be used as feed material for the production of expanded lightweight aggregate. The recovered char had an ash content of about 47% and was a nominal -1 mm in size.

Feb 24, 1997

By F. D. Fox

The Flambeau and Ridgeway Mines, both owned and operated by wholly owned subsidiaries of Kennecott Minerals Company, were located very close to populated areas having initial concerns about health, safety and the environment. The success of both operations depended upon developing a framework of community support and enhancing sustainable development opportunities throughout the entire life cycle of the mining operations to address these concerns. The protection of the Flambeau River was the cornerstone of the Flambeau Mine’s success. The highest priority for the Ridgeway Mine was to ensure long-term physical, chemical and ecological stability of the reclaimed mine site. Both of these goals have been achieved and are discussed in this paper, which highlights Kennecott Minerals Company’s integration of sustainable development principles into its business decision-making and management processes.

Jan 1, 2003

By F. W. Horton

This paper covers the salient features of the occurrence and mining of sheet mica in the United States and the preparation of mica for market; presents the results of a study of the physical properties of domestic and foreign micas, which the author hopes may he of interest to every mica user, as it definitely answers many questions as to the suitability of various minas for particular purposes; and discusses mica-trade conditions and the future outlook for the domestic mica industry. ACKNOWLEDGMENTS The author takes pleasure in acknowledging his indebtedness to J. R. Thoenen, of the United Stator Bureau of Mines, under whose guidance the work reported herein was performed, and to Frank L. Hess, also of the Bureau, for information on the geological and mineralogical characteristics of mica-bearing pegmatites.

Jan 1, 1935

By I M. van Waveren, F Hasibuan, M J. Crow

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. Two Hg-Au occurrences west of Bangko, Sumatra occur within the West Sumatra Permian Volcanic Plutonic Arc. The Melipun Hg-Au occurrence was exploited in the past and mineralisation occurs within a hydrothermally altered cupola of a buried intrusion. The Salak Hg-Au occurrence occurs within the outcrop of the Dusunbaru pluton, likely within the remnants of a caldera in which hydrothermal mineralisation was developed. Both occurrences formed late in the history of the volcanic arc, probably between the Triassic and early Jurassic. The Melipun occurrence may have potential at depth, but that at Salak is small and lies within the area of a proposed Geopark.CITATION:Crow, M J, van Waveren, I M and Hasibuan, F, 2015. Two Hg-Au occurrences in the west Sumatra Permian volcanic-plutonic arc west of Bangko in Sumatra, Indonesia , in Proceedings PACRIM 2015 Congress, pp 573–578 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By Keith L. Harris

The economy continued to expand during the second quarter, but at a much slower pace than expected. According to latest estimates released by the Department of Commerce, the real gross national product (GNP) grew at a seasonally adjusted annual rate of 0.6% compared with a revised growth rate of 3.8%2 for the first quarter of 1986 and 2.3% for the second quarter of 1985 (table 1). The strong growth of personal consumption expenditures, Government purchases of goods and services, and residential investment was moderated by the growing trade deficit, declining investment in business inventories, and the continuing lag in nonresidential investment. Much of the decreased capital spending for the nonresidential sector for the first and second quarters resulted from reduced petroleum exploration and drilling in response to low petroleum prices. Capital spending and trade continue to be areas of weakness for the economy. Real new plant and equipment expenditures for 1986 are estimated to be 1.3% below those of 1985 (table 2). Real net exports of goods and services decreased $24.6 billion, as exports declined 5.6% and imports grew 16.5%. About two-thirds of the $19.3 billion increase in imports was in petroleum and petroleum products, which, because of their lower prices, should help the economy in the future. In response to the sluggishness of the economy, the Federal Reserve System reduced its discount rate from 6.5% to 6% in early July. Inflation, as measured by the fixed-weighted GNP price index, declined from a revised 2.5% in the first quarter to 1.9% in the second quarter because of significantly lower energy prices.

Jan 1, 1986

By AIME AIME

FOR the use of workmen and employees, the company should establish a dispensary and a -hospital where workmen who suffer accidents or professional diseases may be taken care of; and at suitable places in the mine or metallurgical plant it should install first-aid stations. Workmen have a right to receive 75 per cent of their wages while they are unable to perform their work as result of a professional disease; but some companies pay full wages and in the case of natural disease, with the exception of venereal, alcoholism, injuries from fights, and chronic illnesses, 50 per cent of their wages up to a period of two months. The number of diseases the Law considers as professional is large and increases almost daily. Among the professional diseases, the one which has caused greatest harm to the miners and expense to the companies is silicosis. To avoid its propagation, companies should take every possible precaution that the working atmosphere is free from dust, abating this by frequent sprinkling of the workings using, wet drills and furnishing the workmen adequate protective apparatus such as respirators.

Jan 1, 1937

By Navid Bahrani

Introduction ? Today?s economic market is motivating underground mining companies to increase development advance rates and enhance their NPVs. ? For example, block cave mining involves development of kilometers of drifts with multiple pillars. ? The cyclic nature of drill and blast, and its inherent tendency to damage the surrounding excavation rock mass and increase support demand often result in poor advance rates ? This has motivated mining companies to replace the conventional drill-and-blast as the main excavation method with alternative methods such as mechanized excavation. ? There is little experience with mechanized or non-explosive excavation methods in hard rock metalliferous underground mining.

Oct 1, 2010