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By Sharon G. Roness

Powder River Basin (PRB) mines were originally built to serve power plants designed specifically for their: coal. Sulfur was the major concern. Btu content and sodium limited the market for some plants. The PRB market has now extended to plants that are converting from other coals because of the Clean Air Act. These new customers are more sensitive to constituents that affect boiler and precipitator performance. At the same time, the prospect of deregulation is forcing power companies to improve cost controls. Kerr-McGee Coal's Jacobs Ranch Mine has responded to the changing marketplace with an expanded coal quality and customer service program.

Jan 1, 1998

By D. B. Reger

DAVID B. REGER.-T Want to 'add that since this paper was prepared a well is now being; drilled it the location recommended do the last page. It was not, however, done at my instance; it was done at the instance of Dr. White, the State- Geologist of West Virginia, who has been trying for several years to induce the large oil and gas companies to make a test of some of these, deep sands in West Virginia and a well is now just being started in Wood County, right at this immediate

Jan 4, 1917

By Ronald P. Hollenbeck

This study reviews and discusses the fluorspar industry in the Eastern United States, with emphasis on factors controlling the industry such as production, consumption, uses, and transportation. The greatest potential for increased consumption of fluorspar in the immediate future was found to be in the manufacture of fluorine chemicals and steel. Important factors affecting the future domestic industry include imports and the maintenance of adequate domestic fluorspar reserves. Exploration, commercial deposits, mining and milling, reserves, and new developments in the industry are covered.

Jan 1, 1967

By Hon-Yim Ko

The properties of coal from the Pittsburgh seam, procured from the Bruceton and Federal No. 2 Mines were found to be similar. Strength and stiffness properties of Beehive Mine coal were determined and the material found to be isotropic. Mechanical, index and geologic properties of roof and floor coal measure rocks from Beehive mines were measured and correlated. Analytic formulations are given for coal creep under uniaxial loading, while triaxial creep is being investigated. Results of testing of coal model structures are compared with predictions from using several material models.

Jan 1, 1976

By Marco Antonio Meggiolaro

Notches are preferential sites for fatigue and for environmentally assisted cracking (EAC) initiation. Semi-empirical notch sensitivity factors have been used for a long time to quantify notch effects on fatigue design. Recently, this concept has been mechanically modeled using techniques which properly consider the notch tip stress gradient influence on the fatigue behavior of mechanically short cracks. This model properly calculates such values from the basic fatigue resistances of the material, its fatigue limit and crack growth threshold, considering the characteristics of the notch geometry and of the loading, without the need for any adjustable parameter. Such criteria to estimate notch sensitivity and tolerable short cracks on fatigue have been extended to EAC conditions and verified by proper tests. In its simplest version, the criterion for the maximum tolerable stress under EAC conditions uses the resistances to crack initiation and to large crack propagation and the characteristic short crack size under EAC, considering the crack size and stress intensity factor. Moreover, the tolerance to short cracks under fatigue and under EAC conditions can be unified in an extended Kitagawa-Takahashi diagram, a new and potentially very useful tool for material selection tasks.

Aug 8, 2018

Between 1993 and 2003, a series of AG and SAG mill pilot plant trials were conducted using Hardinge Ical pilot plant scale SAG mills on numerous ore samples and ranging across a wide variety of operating conditions. The data from these tests were used to evaluate the design of SAG and AG mill circuits for over a dozen projects, of which about half were eventually constructed and commissioned. The data were also used in the development of SAG mill modelling, scale-up and simulation procedures by several consultants who had access to part of the data set. Recently, we have had the opportunity to bring this data together and further analyse the consolidated dataset. This paper reports on the outcomes of this analysis that has identified the impacts of different AG/SAG circuit flowsheets and operating conditions on energy efficiency and operating cost.

Jan 1, 2012

By J Bartlett, P Quigley

Historical research has played a significant role in the rebirth of the Bendigo Goldfield. The historical research undertaken by the company has been directed to specific areas such as verifying the total gold production of the field, the gold production from defined blocks on each of the major anticlines, the extent of workings of each mine which exceeded 200 m depth, the size and style of reefs mined in each shaft and also within specific domains of the field. Application of this data has assisted in the determination of possible dimensions of different reef styles and the location of mineralisation within each reef system. Description of grade variation, percentage of quartz and the amount and species of accessory sulphide minerals, as well as early geotechnical observations accompanying stoping methodologies, provides valuable analogues for reef structure being defined in the current program. Historical information on shafts on the two anticlines the company is exploring has allowed the postulation and recognition of repetition of reef development within the same stratigraphy in the hinge zones of the adjacent folds. The similarities of mineralisation styles across the field within both specific lithological units and structural setting has had important implications in respect to exploration drill targeting and the estimation of grade and tonnes.

Jan 1, 2003

By W. R. ARGYLE, R. A. SHERMAN, Henry Kreisinger, John Blizard, B. J. CROSS, A. R. Mumford

On entering the World War the United States was confronted with the necessity of building in a short time a large number of ships of tonnage adequate to transport troops and war materials to Europe and to carry food supplies to the allied countries, whose merchant fleets had suffered greatly by submarine warfare. The necessity of building ships quickly led to the formation of the United States Shipping Board, which was charged with the duty of developing an efficient organization for the purpose. Such an organization was developed under the name of the Emergency Fleet Corporation; it was under the control of the Government, but could conduct its business in the most direct way, like a private corporation. In order to build the largest- number of ships possible without drawing too heavily on the steel industry, which was already taxed heavily by the production of munitions, it was decided to build wooden as well as steel ships. These ships were built from a few standard designs to enable a large number of duplicate parts to be fabricated in inland shops and transported by railroad to the shipyards on the seacoast, where they were assembled into ships. In other words, the plan was to manufacture the ships rather than to build them. The shops on the seacoast were reserved to make those parts of the ships' equipment that could not readily be transported. The inland shops made the parts that could be transported to the seacoast by railroad. Among the more important parts of the ships' equipment to be standardized were the boilers. As the Scotch marine boiler in large units is bulky and can not be transported by railroad, and as, for the same capacity,much more steelis needed in its construction than for water-tube boilers, a few simple designs of water-tube boilers were developed that inland shops having ordinary equipment could make in large quantities.

Jan 1, 1924

By J. N. Van Sant

Lignite mining in North Dakota was begun about 1884 to supply the domestic needs of settlers. Annual production has grown rather slowly but steadily, exceeding 3 million tons in 1950. The western part of the State has lignite reserves, amounting to 351 billion tons, underlying an area of 28,000 square miles. Contour strip mining has almost completely replaced underground mining as the method of production. Lignite is often found under rather shallow and easily removed overburden, and this is the primary reason for the change in mining practice. Current mining operations are conducted where the overburden is 30 to 70 feet thick. Contour strip mining results in high production rates, at present 27 to 56 tons per man-day. These high production rates result in relatively low production costs.

Jan 1, 1959

By Andrés Gómez

"La simulación se puede aplicar en toda las operaciones mineras, en este caso específi-camente en carguío, acarreo y descarga (palas-camiones-botaderos, excavadoras-camiones-tolvas de transferencia; y tolvas de transferencia-trenes-concentradora/bo-taderos). Se simula en función del tonelaje de producción, el requerimiento del número de palas, excavadoras, camiones, trenes, equipos auxiliares y capacidades de tolvas de transferencia, concentradora y botaderos. Se aplica en diferentes empresas mineras brasileras y chilenas como base para el planeamiento y toma de decisión en tamaño y número para la adquisición de camiones, cargadores, equipos auxiliares, etc. "

Sep 1, 2017

By A. G. Moon

Kennecott Copper Corporation's Chino Mines Division concentrator is located in Hurley, New Mexico. Construction of the concentrator was started in 1910 and its capacity was progressively increased over the years to the present nominal 20, 425 t/d of ore (22, 500 stpd). The principal copper minerals present in the ore are chalcopyrite and chalcocite with much of the chalcotite intimately associated with pyrite. Lime is used to depress pyrite, and flotation at a high pH or alkalinity is required for optimum recovery of chalcocite with good rejection of the pyrite. Regrinding is also required to liberate chalcocite-pyrite middling grains. Accurate control of the lime addition is necessary to obtain both optimum metallurgy and minimum lime usage. At low pH levels, flotation cell control is difficult due to excess froth, but excessively high pH levels can go unnoticed because froth characteristics do not change from those experienced at the deisred pH. With manual control of the lime addition, the desired pH can be exceeded for periods of up to two hours. In 1972 a major renovation of the flotation and regrinding circuits was com¬pleted and at that time a new lime distribution and control system was placed in operation. Limestone is obtained from a nearby quarry west of Hurley. The limestone is crushed, sized and fed to a rotary kiln and the quicklime product is stored prior to slaking. The lime is slaked, as required, in a mixing tank-classifier type slaker and the lime slurry is pumped to a concentrator storage tank from which it is distributed through a conventional closed loop system. The current average lime usage rate is approximately 6 kg/t of ore (12 lb per st).

Jan 1, 1976

By Shadia J. Ikhmayies

The SnO2/CdS/CdTe thin film solar cells were fabricated on glass substrates by using the spray pyrolysis (SP) technique for the deposition of the SnO2 and CdS layers and vacuum evaporation for the CdTe layer. The transmittance curves were used to investigate the interdiffusion in the two interfacial regions SnO2/CdS and CdS/CdTe by taking the first derivative of the absorbance as a function of wavelength. The appearance of new bandgaps around the bandgaps of SnO2:F, CdS:In and CdTe layers is a strong evidence on the interdiffusion in the two interfacial regions and/or the formation of quantum dots.

Jan 1, 2010

By William H. Eatock

The Saskatchewan ore zone strikes slightly south of East, from the Alberta border to Manitoba; and dips to the South. The conventional mines are located along a broad strike line from Saskatoon to Esterhazy-Rocanville. Nine conventional mines have developed ore bodies at a nominal depth of 915 metres (3000 ft.). One mine had developed an ore body at 1525 metres (5000 ft.) by solution mining. Mining reserves of 100 years are not unusual in this vast ore body. Most of the mines were brought on stream during the 1960s. All the conventional mines were influenced by practices developed at Carlsbad, N.M. By 1970, the industry was faced with serious over-capacity resulting in the cancellation of some projects and the introduction, by the provincial government, of the Potash Pro-rationing Regulations designed to share the available market amongst all the producers. This resulted in production rates as low as 40% of capacity. As a result, the 1970s were characterized by attempts to reduce cost, rather than improve production or processing techniques. In recent years, the plants have all been brought to full capacity, and are currently involved in a massive program of expansion, which promises a period of advancing technology.

Jan 1, 1980

By Ji-He Wei

Keywords: stainless steel, AOD refining, side and top combined blowing, mixing characteristics, water modeling The fluid mixing characteristics in the bath during the side and top combined blowing AOD (argon-oxygen decarburization) refining process of stainless steel have preliminarily been investigated on a water model unit of a 120 t AOD converter. The geometric similarity ratio between the model and its prototype (including the side tuyeres and the top lances) was 1:4. On the basis of the theoretical calculations for the parameters of the gas streams in the side tuyeres and the top lances, the gas blowing rates used for the model have more reasonably been determined. The influence of the tuyere number and position arrangement, and the gas flow rates for side and top blowing on the characteristics has been examined. The results demonstrated that the liquid in the bath underwent vigorous circulatory motion during gas blowing, without obvious dead zone in the bath, resulting in a well mixing effectiveness. The gas flow rate of the main tuyere had a governing role on the characteristics, a suitable increase in the gas flow rate of the subtuyere could improve mixing efficiency, and the gas jet from top lance could make the mixing time prolong. Corresponding to the oxygen top blowing rate specified by the technology, a roughly equivalent and good mixing effectiveness could be reached by using six side tuyeres with an angle of 27 degrees between each tuyere, and five side tuyeres with an angular separation of 22.5 or 27 degrees between each tuyere. The relationships of the mixing time with the gas blowing rates of main-tuyeres and sub-tuyeres and top lance, the angle between each tuyere, and the tuyere number have been obtained.

Jan 1, 2005

By Arash Khosravifar

The seismic design of extended pile shafts for the combined effects of dynamic shaking and liquefaction-induced lateral spreading is investigated using nonlinear dynamic finite element analyses (NDA). Results of NDA parameter studies are used to illustrate how inertia and lateral spreading loads combine during shaking. The NDA results are used to evaluate equivalent static analysis (ESA) methods. Implications for design practice are discussed.

Jan 1, 2010

By Eduardo Rojas, Pedro Landeros

El Teniente Mine expansion plans are currently under development and construction stages through an integrated project strategy that will allow the continuity of future mining. The deepest sector corresponds to Andes Norte Project that faced rockburst risks during tunneling in a completely different manner, implementing different actions for the mitigation of seismic hazard and seismic risk management, based on the following main aspects: rock mass preconditioning techniques such as destress blasting and hydraulic fracturing, improvement of rock support design with the inclusion of elements with higher energy dissipation capacities, use of mechanized equipment for the most critical activities in addition to re-entry protocols and improvements in geological, geomechanical and seismic data collection procedures to reduce the uncertainty of rock mass behavior. The current seismic risk management strategy integrates all of these elements and is the basis of construction methodologies in use, supporting the technical feasibility of tunneling in high-stress environments.

Apr 26, 2022

By S. Ranganathan

Production of ferro-chromium in the submerged-arc furnace is highly energy-intensive. Several process rates have been attempted to reduce the specific energy consumption in the production of this alloy. An exhaustive understanding of the thermo-chemical features of the production process can be used to reduce the specific power consumption significantly. The knowledge can be used to reduce the energy drain through undesired reactions in the process can be minimised. Plant trials have shown that specific energy consumption up to 100kWh/tonne of hot metal can be obtained by adopting this strategy. The process requires modification in operation practice and does not require any capital investment unlike other processes adopted for reducing power consumption. The principle of thermo-chemistry involved in this process development and results of plant trials are discussed in detail.

Jan 1, 2007

By Rudolf E. Greuer

Two computer programs for the real-time calculation of concentration distributions in the ventilation system of underground mines were designed. They allow one to simulate the movement of fumes or other contaminants with the ventilating air, the calculation of concentrations at any given point and time, and the determination of the total contaminant exposure at different places in the mine. Multiple and time variable contaminant sources can be handled and recirculation is no obstacle. The, first program is based on an airflow distribution which has, in the input data, to be stated. The second program has been linked to in existing program for the calculation of airflow distributions. Two versions of this second program are provided to accommodate the two existing programs. Several executed examples demonstrate the program performance.

Jan 1, 1981

By K. Dufresne

Blasting in geothermally high temperature ground and/or extremely reactive ground is an increasing common challenge for surface and underground mines. Many current PETN based non-electric and electronic detonators have manufacturer published in-hole temperature limits ranging from 55°C to 65°C (131°F to 150°F). When confronting blasthole temperatures above the manufacturer published limits, operations may request site-specific guidance and qualification for use. The advised safe loading window for in-hole PETN based detonators is often too short to be practicable for production blasting. To overcome limitations of PETN based initiation systems, surface mines with high temperature ground and/or reactive ground are known to load blastholes with a qualified high temperature bulk emulsion that are top primed with a cartridge of temperature qualified detonator sensitive emulsion plus an RDX detonating cord downline. As there is no in-hole delay detonator in this system, blasthole timing is accomplished with surface delays. Although this system is safe, top priming and surface delaying does influence floor quality and top size fragmentation, and safe loading windows times reduce blast block size and increase blasting frequency. A mining company with a site characterized by geothermally high temperature ground plus highly reactive ground employed a blasting system like the one described above. The site desires to improve blasting performance by moving to an in-hole delay initiation system that can withstand the site ground conditions. At the request of the mining house, DynaEnergetics (hereafter “the company”) developed an electronic initiation system for application in geothermally high temperature ground and/or extremely reactive ground conditions. The DynaEnergetics IGNEO high temperature electronic initiation system is rated for in-hole use in ground up to 150°C (302°F) for 48 hours. The detonator consists of a high strength detonator with an HMX base charge and thermally resistant downline. To make up a primer, the detonator is inserted into a booster charge assembly that is fitted with a small HMX shape charge. This high energy primer is designed to be compatible and reliable for firing bulk emulsions, including those with high percentages of urea inhibition to combat reactive ground. Up to 1000 detonators may be programmed in 1ms increments up to 1500ms. The system is controlled by a digital firing panel that can be used with either a wired or wireless trigger. The system enables high temperature and/or reactive ground sites to utilize in-hole delay initiation and realize the associated performance benefits

Jan 1, 2024

By L. A. Homeniuk, R. Bonnar

"The Fond-du-Lac uranium deposit is located on the northern rim of the Athabasca Basin. The uranium mineralization is, for the most part, confined to the Athabasca Group, which is underlain by pre-Helikian metamorphic rocks of the Western Craton.The deposit is characterized by a remarkable train of mineralized glacial erratics which led to the original discovery. The mineralization is present as a ""high-grade"" core and a diffuse ""low-grade"" aureole. The ""high-grade"" core occurs as a stockwork of steeply dipping pitchblende veins which strike N 50°E. Hematite, siderite and secondary silicate are also abundant. The ""low-grade"" aureole contains uraniferous goethite, argillaceous material and rare carbon buttons. Recent alteration to coffinite has taken place along the margins of pre-existing ore minerals.The ""high-grade"" core is 390 m long and 10 to 40 m wide, and is surrounded by an irregularly shaped zone of ""low-grade"" mineralization with a similar length and a width of up to 350 m.Comparing the Fond-du-Lac deposit to other unconformity-type deposits, several important differences can be noted:1. Ninety per cent of the ore is above the unconformity, in the Athabasca sandstone.2. The deposit is not associated with underlying graphitic rocks or a major structure.3. The clay-rich alteration zone is not extensive around the Fond-du-Lac deposit.Although there are differences with other Athabasca unconformity-type deposits, the high-grade portion below the unconformity suggests a common origin.The ore deposit is postulated to have been formed from uranium-bearing solutions which entered the stockwork of fractures. Following the reduction in part of these solutions by pre-existing carbonaceous matter and pyrite and/or chemical reaction with pre-existing hematite, deposition continued as a result of decreasing temperature and pressure. Subsequently, minor supergene redistribution of the uranium has taken place."

Jan 1, 1982