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By S. J. Aresco

The Bureau of Mines has been active in promoting the purchase of coal for Government use under specifications that define the requirements in terms of heating value of the coal, expressed in British thermal units, and the composition as shown by proximate analyses. To these, when required, are added the ash-softening temperature, the free-swelling index, and the Hardgrove grindability index. Under most of these specification contracts the bidders guarantee the quality of the coal, and that guaranteed by the successful bidder becomes the standard of his contract. The deliveries are sampled in accordance with instructions 5/ issued by the Bureau of Mines; the samples are analyzed in the Bureau laboratory to determine whether the coal is of the quality guaranteed by the contractor and, if it is not, a price adjustment is made. Analyses of the delivered coal and tipple samples (samples collected at mine tipples as coal is being loaded into railroad cars or trucks) provide valuable data for use in evaluating future bids. In addition, the continuous sampling of coal as delivered is a check on the practical results obtained in burning the coal.

Jan 1, 1962

By Toshiyuki Kawai

Copper concentrate smelting directly in P-S converters was started at Onahama Smelter in 1983. Thereafter, the tonnage of concentrate smelted through the P-S converters increased, such that by 2002, it equaled the tonnage smelted through the reverberatory furnaces. In 2003, 56% of the total copper concentrates treated at Onahama Smelter were processed directly through the P-S converters. Technical improvements are reviewed and advantages of direct smelting in P-S converters are reported.

Jan 1, 2005

The following pages discuss the objectives, the background, and scope of work of an industrial engineering analysis of far-,n haulage systems in underground retreat coal mining. This study ran concurrently with an existing industrial engineering study of methods of improving safety and production efficiency in underground pillar extraction. 1. OBJECTIVES The objective of this project was to provide basic data inputs that will inpart knowledge as to the major constraint to pillar extraction sections. Furthermore, the industrial engineering study will suggest ways to optimize haulage systems and to develop more efficient work practices and operational techniques that will maximize equipment utilization.

Jan 1, 1975

By Fred P. Giese

Southeastern reserves of titanium ores are large, widespread, and ample for anticipated demand. The leading titanium industries are mining and beneficiating sand deposits, principally in Florida, and manufacturing titanium pigments. Most of the mineral output is consumed by the producers themselves. In 1962, 20 percent of the national pigment capacity was in the Southeast.

Jan 1, 1964

By Ben Aleck

The objective of this program was to adapt Space Shuttle technology on high-performance spherical pressure vessels to cylindrical pressure vessels. Specifically, a cylindrical aluminum liner overwrapped with fiberglass filaments and prestressed by yielding the liner under a sizing pressure was to be replaced by a higher strength-to-weight ratio steel liner overwrapped with a higher strength-to-weight ratio filament. The steel was cryoworked stainless steel and the new fiber was Kevlar 49. In addition, the heavyweight ends of the aluminum liner were to be replaced by thin-walled domes which required multiple helix angle wraps for their support, in place of the single kite-string wrap from pole to pole of the aluminum overwrapped design. The use of cold swaging of tube-ends to form bosses, demonstrated on subscale development efforts, had not been achieved full-scale when the contract was initiated. Difficulties arose with the full-scale demonstration which were not solvable at the time with the designs and equipment available. hence, an unanticipated development was the finally selected method of making the 4-in.-diameter stainless steel liner with a single boss and no welds in an 0.020-in.-thick wall, from an 0.050-in.-thick, 13-in.-diameter disk. The demonstration vessel failed by leakage during the prestressing step because embedded oxides had formed flaws in the boss region. Such flaws have been avoided by proper temperature control during hot spinning. Hence, a new design was developed which weighs half as much as its recently developed predecessor. Funds ran out before adequate testable hardware was produced.

Jan 1, 1983

By D. Bogh

Wound rotor motors are used in difficult mining applications where there is a need to start high inertia, hard starting loads while limiting inrush current They are recognized as robust and simple to control. This paper will cover the performance, specification, and important issues to be considered when applying medium voltage wound rotor motors in mining applications. Medium voltage grinding, crusher, and conveyor applications will be discussed. Specifically covered are motor efficiency, speed range, and rotor control. Crane motors often have wound rotor construction, but their load cycle and ratings are outside the scope of this paper.

Jan 1, 2011

By D. C. Bailey, D. I. Hodson

Paper presented at the annual joint meeting of the IMM and IMinE held in Harrogate, 31 January 1991. The Neves-Corvo copper-tin mine is the highest-grade large-tonnage copper operation in the world and is now arguably the most significant producing base-metal mine in Europe, rating in the top ten world producers of both copper and tin. A description is given of the initial exploration work and the development of the project from the orebody discovery in the Iberian Pyrite Belt of southern Portugal in 1977 to full operating capacity in 1990. The chronological account includes discussion of the main organisational, financial, technical and environmental decisions and of the various difficulties encountered, and the challenges of the future are identified. The project was brought in on schedule and within budget

Jan 1, 1991

By Leandro Echavarría

El presente texto describe el sistema epitermal de Arcata, situado en Arequipa, Perú. Arcata es un distrito epitermal de sulfuración intermedia rico en plata y metales base, cuya mineralización se hospeda en vetas de rumbo predominante noroeste y movimiento principal paralelo a la inclinación que forman una estructura de fosa (graben). Las vetas poseen texturas de relleno de espacios abiertos como bandeados costriformes, en cucarda, crecimientos en peine y brechas, con ganga de cuarzo, calcita, rodonita y rodocrosita. Por su parte, los minerales de mena más comunes son galena, esfalerita, calcopirita, con los metales preciosos hospedados en sulfosales de plata (pirargirita y tetrahedrita). Asimismo, se ha identificado una compleja secuencia paragenética con varios pulsos responsables de la mineralización económica.

Apr 22, 2003

As part of its research and development activities concerning coal mine operational/emergency communications sys terns, the Bureau of Mines commissioned several contractors to conduct electromagnetic (EM) noise studies and measurements that would aid the development of improved coal mine operational/emergency communications systems. The bulk of the noise studies and measurements were conducted in 1971. The Pittsburgh Mining and Safety Research Center (PMSRC) inherited the responsibility for monitoring the electromagnetic noise activities by mid-to-late 1971, and initiated a review and evaluation of the current and planned electromagnetic noise work. Arthur D. Little, Inc., (ADL) was asked by PMSRC to assist it in performing this review and evaluation by placing stronger emphasis on certain tasks of existing Contract No. H0122026. This technical memorandum report presents the findings, conclusions, and recommendations of our review and evaluation of the electromagnetic noise measurements of the five contractors we were asked to examine. Our review and evaluation effort included meetings and telephone discussions with technical staff of each contractor; serving as Technical Discussion Leader of a "Contractor's Round Table Meeting on EM Noise, Surface and Subsurface, Operating and Non-Operating Mines" called by the Bureau of Mines; examination and discussion of contractor reports and relevant open literature; sample verification calculations; and the documentation of our findings, conclusions, and recommendations by this report.

Jan 1, 1972

By Michel Aubertin

Les haldes à stériles contenant des minéraux sulfureux réactifs constituent un milieu favorable à la production du drainage minier acide (DMA). Au sein de ces haldes, les processus physiques, géochimiques et biologiques qui mènent à la production du DMA sont nombreux et complexes. Un des aspects critiques qui affecte la génération de DMA est la distribution et le mouvement de l?eau dans les roches stériles. La modélisation numérique est un outil qui permet de comprendre, pour éventuellement contrôler, les mouvements de l?eau (et donc réduire la production du DMA) dans les haldes pendant la période d?exploitation de la mine et à sa fermeture. Plusieurs simulations numériques des écoulements non saturés dans des haldes ont été effectuées. Pour ces simulations, on a considéré divers types de matériaux, diverses conditions atmosphériques et diverses configurations géométriques. Les simulations réalisées montrent que l?on peut contrôler les mouvements de l?eau en introduisant des couches de matériaux fins intercalées dans les haldes formées de matériaux grossiers. Des couches horizontales ne sont cependant pas appropriées puisqu?elles peuvent, dans certains cas, favoriser la création de zones humides susceptibles d?amplifier les effets du DMA. Une faible inclinaison des couches de matériaux fins vers l?extérieur permet de palier à ce problème. Les couches inclinées favorisent un drainage des haldes vers la périphérie. Ceci a pour effet de garder sèche une grande partie des stériles et de réduire, par le fait même, la production du DMA.

Nov 1, 2002

By K. M. Li, Y. D. Zhang

The selection of stripping dragline is a complicated problem. Several factors, such as the deposit buried conditions, the demand of mine production rate, cast blasting result, the mining/stripping operation method and parameters, etc. may comprehensively influence the optimal selection of technical specifications of the dragline. Under these circumstances, the basic thinking and procedures for dragline selection are put forward as follows. •Step 1—Initially estimate the dragline annual stripping rate and stripping bench height according to the annual coal production rate and advancing speed of mining front. Then the feasible alternatives of dragline sizes can be calculated and selected from the existing dragline series. •Step 2—A computer simulation model is developed to simulate the dragline stripping operation, to obtain a series of working face parameters, then to select the best dragline alternative. This step can be interactively iterated until the satisfactory results are obtained. •Step 3— Sensitivity analysis can be done with the systems simulation model by changing the stripping bench parameters, e.g. stripping bench height and cut width, etc. to verify and modify the selection results if necessary. The mathematical model for dragline stripping simulation has been set up. The flowchart of the model is shown. A case study for a large surface coal mine with annual production rate of 16 Mt/a is followed. The dragline bucket capacity and operation radius, stripping bench height and cut width as well as other parameters are comprehensively optimized and selected. Keywords: Open cast, dragline, specification, selection, cast blasting

Jan 1, 2003

By J. Barrett

State-of-the-art wireless communication and location-tracking technologies will dramatically change the face of mine worker safety. The MineTracer System developed by a Liberty Lake Washington company is a broad capability wireless sensor network based on a new breed of technologies known as wireless mesh systems. In this paper, R&D Manager Jim Barrett summarizes the balance of engineering tradeoffs that result in a system that (1) performs well, (2) is survivable against many types of mine accidents, (3) operates for many hours post-accident on battery power, (4) meets stringent MSHA requirements for intrinsic safety, and (5) is economically affordable for the mines.

Jan 1, 2009

By N F. Fraser

Seafield ResourcesÆ offshore placer gold project covers c.10 000 km2 of the Westland continental shelf between Karamea and Jacksons Head, from the low-water mark out to the 120 m isobath (Figure 1). De Beers Marine (DBM), the marine diamond subsidiary of the De Beers Group, will carry out the project with geological input from Placer Solutions (PSL). DBM bring a wealth of expertise and advanced technology to the project, developed during their 20 years of exploration and mining of diamond placers on the Atlantic shelf of southern Africa, where they have also maintained a strong environmental record.   Glaciers and high-energy rivers emanating from the Southern Alps have transported substantial quantities of gold bearing sediment onto the Westland continental shelf during Pleistocene glacial periods, when fluvial gradients are steeper, sea level is c.120 m lower and most of the shelf is exposed. These deposits have been extensively reworked by the advancing shoreline and marine processes during interglacial marine transgressions, and most are now buried beneath a variable thickness of post-glacial marine sand, silt and mud. DBM will use side-scan sonar, swath bathymetry, Chirp sub-bottom profiling and a magnetometer to map the sea floor and sediments beneath it, guided by PSLÆs predictive geological model for gold distribution on the shelf. Cactus grab and vibro-core samples will be used to ground-truth the geophysics and provide stratigraphic, sedimentological and gold distribution data for incorporation into the geological model. Areas of interest identified by the geophysical and sampling data will be investigated in more detail, with closer-spaced geophysics and Mega-drill sampling to a maximum sediment depth of 20 m beneath the sea floor. These samples will be raised to the ship with air-lift suction technology, processed onboard for mineralogical and grade information, then returned to the sea floor. Environmental baseline data will be gathered from Van Veen grab samples of seabed sediment taken throughout the area during the prospecting programme.

Jan 1, 2005

By M J. Van Der Merwe

The mining industry is facing a serious skills resource shortage, growing commodity demand and cyclical prices. This makes focus and allocation of resources in the early stages of project development very important. To assist with these six key elements in the project prioritization process is proposed, namely: 1) Define the project vision, objectives and business case, 2) Determine the potential show stoppers, 3) Determine the key value drivers, 4) Track changes and provide regular feedback, 5) Evaluate the alternatives and, 6) Ensure proper gate management governance at the decision point. Incorporating these elements in the project development process will assist in resource allocation and focus on the high value aspects of projects and alternatives during the early stages of the project development lifecycle. Keywords: Resource allocation and focus, vision, show stoppers, value drivers, project prioritization, linear programming, business case modelling, management decision.

Jan 1, 2008

By Billy J. Thorne

The damage model in PRONTO simulates the dynamic fracture behavior of brittle rock. It is based on work started by Kipp and Grady, [lg] continued by Taylor, Chcn and Kuszmaul [I91 [20] and recently.modified by B. J. Thorne (first documented here). The essential feature of this model is the treatment of the dynamic fracture process in rock as a continuous accrual of damage in tension, where the damage mechanism is attributed to microcracking in the rock medium. The fundamental assumption of the damage model is that the material is permeated by an array of randomly distributed microcracks which grow and interact with one another under tensile loading.

Jan 1, 1989

By J. Tian

"BHP Billiton carried out a pre-feasibility study on the LanPing zinc deposit to evaluate the possibility to jointly develop the zinc deposit into a large-scale zinc project with their Chinese partner. The unique characteristics of the complex LanPing zinc orebody and ore are 1) smithsonite (ZnCO3) as one of major zinc bearing mineral besides sphalerite, 2) varying and irregular oxidation degree of zinc (0 ~ +90%) in the different zone and depth of the deposit, and 3) varying host gangue from limestone/calcite dominant to quartz dominant, which requires a robust and flexible flotation process to recovery zinc from both sulphide and oxide efficiently.The conventional mineral processing flowsheets have been tested on the LanPing samples taken from the various orebodies by various parties during the past 20 years that includes a sequential flotation flowsheet that was tested in a demonstration plant using the mixed ore. The results of the demonstration plant runs show that the conventional oxide flotation using Na2S and amine collectors could achieve 50 ~ 75% of oxide zinc recovery at very high sulphidiser consumption for the mixed ore but the highly oxidised ore did not satisfactorily respond to the flowsheet in terms of performance consistency and efficiency of oxide zinc recovery, which is very crucial to the overall economics of the project."

Jan 1, 2003

By Dae S. Young

The paper point out a new procedure to calculate the volumetric distribution of rock fragments. The method combines the practicality of digital image processing of the rock surface with the theoretical volume calculations based on principles and laws of fractal geometry. The final volumetric distribution curve is compared with the results from traditional sieving indicating close agreement.

Jul 17, 2000

By S. Jayson Ripke, Shane Hoff

Cleveland-Cliffs’ Northshore Mining Company operates a magnetic iron ore (taconite) concentrator and pelletizer in Silver Bay, MN. These are two recent cost reduction projects: 1. Rougher Magnetic Separators were upgraded throughout the concentrator; throughput and recovery were simultaneously improved. 2. Green Ball Roll Screens on one agglomeration circuit were upgraded from 3.5-inch to 2.5-inch rolls. Throughput improved by 24% from 62 to 77 LTPH. Green ball size distribution improved as an added benefit.

Jan 1, 2005

By Jan J. Cilliers, Nicolas Barbian, Esther Ventura-Medina

"Froth structure and stability are known to play an important role in determining flotation recovery and selectivity. An industrial sampling campaign was performed to develop a clearer understanding of the effect of flotation variables on froth stability and the role played by the resulting stability on flotation performance.Froth stability was estimated as the fraction of bubbles bursting on the surface of the froth through image analysis and the solids loading on the bubbles at the top surface. The image processing was performed using the Smartfroth software on the top surface of the froth. The system gives measurements of bubble size distribution, average bubble size and froth velocity. The froth velocity was used to estimate the volume of bubbles overflowing the weir yielding to the fraction of air overflowing the cell. This measurement is the complement of the rate of bubble bursting on the top surface. Also samples of the lamellae were taken by touching the top surface of the bubbles with a glass slide. Then, the amount of solids and liquid per unit area in the bubble lamellae was estimated gravimetrically. Both measurements were used to establish stability criteria.It was generally found that high air flowrates resulted in a drop of froth stability showed by a drop in the fraction of air overflowing and a decrease in the solids loading and simultaneously produced low copper recoveries and low concentrate grades. Deep froths only allowed a small fraction of air to overflow and consequently produced low recoveries. An increase to high frother dosage did not result in an improved fraction of air overflowing, hence producing low recoveries. Likewise, low frother addition only allows low recoveries because the resulting unstable froth cannot support itself. Low aeration was found to be preferential as it allowed high particle loading, therefore high bubble stabilisation, and low gangue entrainment, resulting in the highest flotation performance."

Jan 1, 2003

By J. J. Lukasko

The U.S. Bureau of Mines developed an alternative electrochemical process for the production of calcium metal. The current industrial practice is costly, complex, and inefficient. The Bureau method involved electrowinning of a calcium-tin alloy followed by electrorefining to produce calcium metal. In the electrowinning cell, CaCI2 was fed to a KCI2-CaCI2 electrolyte. The calcium was electrowon at 6500 C into the pure molten tin cathode until the cathode contained 7.5 wt pct Ca. Current efficiency for electrowinning averaged over 90 pct. The resulting calcium-tin alloy served as the anode for the electrorefming cell, which employed a [CaC~-CaF2] fused salt as the electrolyte. Calcium metal was electrorefmed at 8500 C with a current efficiency of 85 pct based on calcium metal recovered. The calcium metal analyzed 99.2 pct, which is purer than commercially produced calcium.

Jan 1, 1990