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By James W. Bass

Introduction Atmospheric fluidized bed combustion (AFBC) is an improvement over coal-fired boiler design. It offers several advantages over conventional boilers. AFBC can meet sulfur and nitrogen oxide emission regulations without the need for add-on flue gas treatment equipment. The relatively low combustion temperature inhibits ash melting, thus reducing slagging and fouling that can in turn increase a boiler's fuel flexibility. AFBC process The fluidized bed boiler that operates at atmospheric pressure on the fire side (AFBC) is relatively simple and no different in purpose from those pulverized coal boilers used by utilities today. Fluidized bed boilers can generate steam at the pressure and temperature needed by modern steam turbines. Only the firing system is different. In fluidized bed combustion, the fuel can be almost any coal or waste fuel. It is burned in the presence of a bubbling bed of limestone. Air is forced through the bed at a velocity sufficient to support the weight of the bed particles. When the bed is fully fluidized, it bubbles like a boiling liquid. Although the burning coal makes up less than 1% of the fluidized bed, all the bed particles are heated quickly by the turbulence. The calcium in limestone reacts with sulfur dioxide produced in coal combustion to form calcium sulfate in a dry solid state. In this way, sulfur emissions regulations can be met without installing flue gas desulfurization equipment. Boiler tubes submerged in the bed absorb heat directly from the turbulent solids. The heat converts water in the tubes to steam or superheats the steam. Because of the intimate contact of the boiler tubes with the fluidized bed, heat transfer is highly efficient. Consequently, less boiler tubing surface is needed to generate the same amount of steam as in a comparable pulverized coal boiler. The optimum temperature for sulfur capture is relatively low, about 815°C (1500°F) as opposed to 1370°C (2500°F) for pulverized coal boilers. This results in the formation of lower levels of NON. Because operating temperatures are below those that fuse coal ash, a single design can burn a variety of coals without slagging or fouling problems. TVA's AFBC development program Tennessee Valley Authority's (TVA) involvement in AFBC development began in 1974 and has addressed the technical uncertainties through a comprehensive program of design, experimental, and analytical studies. In 1979, TVA and the Electric Power Research Institute (EPRI) developed plans for a 20-MW AFBC pilot plant, a 10-fold scale-up over the next largest test facility. Pilot plant design features TVA constructed the pilot plant at the Shawnee Steam Plant near

Jan 4, 1986

By Steve Kral

More than 111,350 mining and construction industry professionals from throughout the world gathered in Las Vegas, NV, March 19-23 for ConExpo-Con/Agg 2002 and IFPE 2002. The triennial event is the Western Hemisphere’s largest equipment show for the quarrying, aggregates, construction and ready-mixed concrete industries. Despite the difficulties in the world economy, ConExpo-Con/Agg 2002 attracted more than 2,450 exhibitors from throughout the world. This was an increase from the 1,882 exhibitors that were on hand for the 1999show. And this year’s show occupied more than 180,225m2 (1.94 million sq ft) of exhibit space at the Las Vegas Convention Center. This was an increase from the160,900 m2 (1.73-million sq ft) occupied at the 1999event.

Jan 1, 2002

By P. W. Godbehere

"INTRODUCTIONMagnetic mill linings have been developed from an invention by Mr. Bertil Brandt, the originator of the Skega rubber lining. The OREBED magnetic mill lining is a concept in which rubber covered strontium ferrite permanent magnets are arranged on the inside wall of a mill shell so that they attract magnetically susceptible material be it ore, media or tramp, to form a protective layer over the magnets and to serve as an operating surface with indefinite life.Noranda Mines Ltd. through its associate Norcast Division of Noranda Metal Industries formed a joint venture with the inventors to market magnetic mill linings in North America. For the past twelve months trials have been undertaken in conjunction with Orebed Inc. to test and develop these linings for grinding mill applications at the Horne Concentrator. Two independent milling circuits are currently being operated, one treating a siliceous gold ore and the other a copper slag.This paper presents the results of the magnetic lining test programme to date."

Jan 1, 1983

By Chris Larsen, Ian Orford, Mike Cooper

"An autogenous grinding circuit was commissioned at the Brunswick concentrator in October 1998. The autogenous grinding circuit replaced existing surface crushing plants, fine ore storage, rod and primary ball mills. The 8.54m diameter x 4.27m long (EGL) AN1 mill is driven by a bidirectional variable speed 6.3MW ABB wound rotor motor with Slip Energy Recovery (SER) drive. The AG mill was subsequently converted to SAG operation in May 1999 for a number of reasons. The mill is operated in closed circuit with horizontally inclined 660mm diameter cyclones to produce a circuit product P80 of 85 microns. Extensive test work and JKSimMet design modeling resulted in a production circuit operating closely within design expectations.The circuit is highly instrumented and controlled via a hybrid Programmable Logic Controller (PLC-5) and Fisher PROVOX Distributed Control System (DCS) that is in communication with the property information highway. An expert control system (Gensym G2) is used for control of the SAG mill load.Engineering and construction were completed in 28 months from the time of management approval for the project. The Brunswick AG/SAG mill circuit was commissioned on schedule at the $M 23.5 forecast budget."

Jan 1, 2001

By J. Chlopas, D. J. Barratt, M. V. Sharp

"This paper describes the modifications made to the Fox Mine copper concentrate bin in order to obtain a continuous flow condition. The design of these modifications is based on test results obtained on Fox Mine concentrate using the flow factor testing machine in the research facilities of Cominco at Trail, B.C.The original design consisted of a cylindrical steel bin on a concrete slab with two slot-discharge openings. Based on predictions of the maximum mass flow hopper angle for conical and wedge shaped hoppers for the concentrate on various potential bin lining materials, Ultra-High Molecular Weight (UHMW) Polymer was selected as a liner.Using the recommended angles for conical and wedge shaped hoppers, the profile of the bin base was changed to suit the existing slot openings.The initial method of fastening the liner resulted in failure of the connections. Subsequent modification to the zinc concentrate bin fastener system proved satisfactory and it has now been in operation for over one year without any separation of the lining material.Utilization of flow testing procedures on concentrate samples has demonstrated that proper design of storage bins or hoppers to achieve continuous flow can be incorporated into the design of new plants."

Jan 1, 1978

By B. G. Tarasov

This paper proposes the further development of a recently identified shear rupture mechanism (fan mechanism) that elucidates a paradoxical feature of hard rocks ? the possibility of shear rupture propagation through a highly confined intact rock mass at shear stresses that can be significantly less than frictional strength. In the fan mechanism, failure is associated with consecutive creation of small slabs (known as ?domino blocks?) from the intact rock in the rupture tip, driven by a fan-shaped domino structure representing the rupture head. The fan head combines such unique features as extremely low shear resistance, self-sustaining stress intensification, and self-unbalancing conditions. Consequently, the failure process caused by the mechanism is inevitably spontaneous and violent. Physical and mathematical models explain unique and paradoxical features of the mechanism, which can be generated in primary ruptures and segmented faults. The fan mechanism provides a novel point of view for understanding the nature of spontaneous failure processes, including shear rupture rockbursts. The process explains, in particular, features of shear rupture rockbursts such as activation at great depths, generation of new shear ruptures in intact rock mass, nucleation of hypocentres at significant distances from the excavation, shear rupture development at low shear stresses, and abnormal rupture violence.

Jan 1, 2014

Plan de l?exposé ?? Présentation du site de la mine Restigouche et du mandat confié à Genivar ??Dénoyage de la mine ??Processus d?enlèvement des boues au fond de la fosse ??Utilisation de Géotubes dans le procédé à l?usine de traitement des eaux.

Feb 1, 2008

By C E. J de Ronde, I C. Wright

Oceanic subduction-related volcanic frontal arcs extend over 20 000 km within the western Pacific basin and over 21 500 km worldwide, yet they remain largely unexplored with respect to active seafloor mineralization. Systematic exploration of 26 major submarine volcanoes along ~840 km of the Kermadec arc northeast of New Zealand has documented ten (39 per cent) as being hydrothermally active. This frequency of venting is comparable to that on slow-to-moderate rate spreading mid-ocean ridges, which comprise ~80 per cent of the 60 000 km-long global system of spreading centers. The chemistry of fluids discharged from the Kermadec arc volcanoes is moderated by magmatic components in both the gaseous (CO2 + SO2-H2S) and liquid (Fe) phases at very high concentration.The high frequency of venting coupled with chemically rich discharge discovered during this first systematic survey of any arc system forecasts submarine arcs as being important sources of chemicals to the oceans and as potentially lucrative exploration sites for seafloor mineralization. The exploration protocols developed during these surveys include bathymetric mapping of mostly unknown volcanic edifices, followed by detailed water column profiling and sampling to detect and characterize volcanic fluid emission signatures. These procedures are being refined as the survey progresses, both for efficiency and as direct seafloor observations become available for predictive application of water column plume information to guide seafloor mineral exploration.

Jan 1, 2002

By Felipe Perissé Duarte Lopes

The tensile properties of DGEBA/TETA epoxy matrix composites reinforced with different amounts of curaua fibers were evaluated. Tensile specimens with up to 35% in volume of long, continuous and aligned curaua fibers were room temperature tested in an Instron machine. The fracture was analyzed by SEM. The results showed significant changes in the mechanical properties with the amount of curaua fibers. This was compared to other bend-tested composites with distinct matrices. The fracture analysis revealed a weak fiber/matrix interface, which could be responsible for the comparatively low performance of some properties.

Jan 1, 2010

By Mark Van Dyke, Ted Klemetti, Joe Wickline

"The identification and mitigation of adverse geologic conditions are critical to the safety and productivity of underground coal mining operations. To anticipate and mitigate adverse geologic conditions, a formal method to evaluate geotechnical factors must be established. Each mine is unique and has its own separate approach for defining what an adverse geological condition consists of. The collection of geologic data is a first critical step to creating a geological database to map these hazards efficiently and effectively. Many considerations must be taken into account, such as lithology of immediate roof and floor strata, seam height, gas and oil wells, faults, depressions in the mine floor (water) and increases in floor elevation (gas), overburden, streams and horizontal stress directions, amongst many other factors.Once geologic data is collected, it can be refined and integrated into a database that can be used to develop maps showing the trend, orientation, and extent of the adverse geological conditions. This information, delivered in a timely manner, allows mining personnel to be proactive in mine planning and support implementations, ultimately reducing the impacts of these features. This paper covers geologic exploratory methods, data organization, and the value of collecting and interpreting geologic information in coal mines to enhance safety and production.The implementation of the methods described above have been proven effective in predicting and mitigating adverse geologic conditions in underground coal mining. Consistent re-evaluation of data collection methods, geologic interpretations, mapping procedures, and communication techniques ensures continuous improvement in the accuracy of predictions and mitigation of adverse geologic conditions. Providing a concise record of the work previously done to track geologic conditions at a mine will allow for the smoothest transition during employee turnover and transitions. With refinements and standardization of data collection methods, such as those described in this paper, along with improvement in technology, the evaluation of adverse geologic conditions will evolve and continue to improve the safety and productivity of underground coal mining."

Jan 1, 2019

By R. L. Amelunxen

"In January 1983, Gibraltar Mines Ltd. started an exploratory program on Column Flotation with hopes of improving performance of the Molybdenum Cleaning circuit. The encouraging results led to a column test trial in the Bulk Copper Cleaner circuit where the test unit has per¬formed well. A program was undertaken to understand the mechanics of column operation. A year and a half later, Gibraltar is considering the replacement of existing Bulk Copper and Moly Cleaning flotation cells with a fully computer con¬trolled Column Flotation circuit.BRIEF SUMMARY OF TESTWORKInitial testwork was done with a home made 20 inch diameter x 31 foot high column, equipped with a doppler flow-meter at the tail line and automatic level conrol. This loop maintained constant level in the column by throttling the tail valve. This column was placed in a variety of locations around the Moly circuit as shown on Figure 1 a, b. Test re¬sults indicated that the column could achieve much higher grades than the conventional cells, but recovery wise, the performance was low. Spillages from overloaded pump boxes were a common frustration during this time.Column control strategy was reviewed; and, in light of information received from McGill University, changed to conform with the methods that had been employed by D. Wheeler, of the Column Co. of Canada4 and Gaspe Copper Mines3.The column was tested replacing a portion of the bank, figure lc. The results obtained were more or less equal to the circuit. However, as we had Nitrogen gas connected to the column and not the regular cells, the column was kept in service. With the use of Nitrogen in the column, the usual copper depressant, Sodium Cyanide could be replaced with Sodium Hydrosulphide, hence lower operating cost.As time went on, a 10 inch diameter column was added in series to re-treat the concentrate of the 20 inch diameter column with hopes that the copper content would decrease from 0.6% down to 0.3% in order to save on subsequent leach¬ing costs. So far, results indicate there has been some im-provement, hut we are not achieving 0.3% copper. (See figure 1d)."

Jan 1, 1985

By Rajendra Singh

Underground depillaring of contiguous coal seams/sections is a difficult problem, which becomes even more complex if the interburden/parting between them is thin. Conventionally, the depillaring with caving of contiguous seams/sections is done in descending order. However, if the parting is thin, the influence of the top sections/seams working over the standing pillars of bottom the sections/seams becomes extremely important for the safety and optimal exploitation of coal. Field investigations were carried out at Nowrozabad East mine where superimposed pillars of the Johilla top section were depillared above the developed pillars of the Johilla bottom section with a 3 m thick parting between the two sections. The competency of the 3 m thick parting (which consists of alternate layers of shale, sandstone and shaly sandstone) was improved by reinforcement (underpinning). The strata control investigations did not show any considerable instability problem of the 3 m thick reinforced parting and pillars of the bottom section due to top section depillaring. On the basis of this field investigation and a laboratory study on simulated models, simultaneous extraction of both the sections, along with reinforcement of the parting, was suggested for the geomining conditions of the Johilla top and bottom sections. Adopting the suggested simultaneous depillaring process, two sub panels of Johilla top and bottom sections have successfully been extracted without any strata control problem. This paper presents this case study along with the results of the strata monitoring conducted to evaluate performance of the underground structures during the field trial.

Jan 1, 2004

By D. Bois, P. Keating, J. Lemieux, M. A. Vallée, M. Allard, R. S. Smith, L. Z. Cheng, M. Chouteau, K. Fountain

"A comparison of data from INPUT, GEOTEM, and MEGATEM airborne electromagnetic (AEM) systems over the Aldermac deposit, Québec, Canada, was undertaken to evaluate the relative ef¬ficiency of these systems for the detection of small, deep conductors. The Aldermac orebody was mined between 1933 and 1934 to a depth of 200 m. A deeper mineralized zone was discovered in 1987. The MEGATEMII system was used to acquire 90- and 30-Hz data over the deposit in 2003 as part of a research project. These MEGATEMII data were compared with data acquired by other AEM systems (GEOTEM and INPUT), and the results show that the MEGATEMII response is ten times larger than the other sys¬tems. For the dB/dt response, 30 Hz gives a better signal-to-noise ratio, whereas 90 Hz has a better signal-to-noise ratio on the B-field.The data were evaluated by numerical modeling. The deposit was best represented by a complex mod¬el, comprising two weakly conductive bodies to approximate the alteration halo, two deeper prisms repre¬senting known orebodies, and three bodies ranging in thickness from 3 to 6 m and in resistivity from 12 to 20 ohm·m, representing the chargeable overburden. This implies that the MEGATEMII system is able to see a small conductive body at more than 200 m depth in an area where the response is contaminated by conductive overburden."

Jan 1, 2009

By Greaves M. C

X-ray fluorescence spectroscopy used for the analysis of mill samples results in improved control of flotation concentrators.Techniques and equipment for sampling pulp streams, filtration and drying, grinding, briquetting and X-ray fluorescence analysis of samples have been developed.The current methods in use permit the analysis for lead and zinc in six pulp samples within 30 min total elapsed from the start of sampling. The X-ray method gives a precision at least equal to the former routine wet-way assay methods.The equipment is used also for pilot plant control, as a means of solving complicated analytical problems and in the rapid qualitative analysis of exploration samples.INTRODUCTIONIn milling and concentrating operations, classical methods for the assay of lead and zinc have been mainly of use for accounting purposes and for the post-mortem examination of plant operations, but have been of little value for rapid mill control. Where attempts have been made to apply these methods to control assaying, it has been necessary to modify the procedures and introduce short cuts which have tended to reduce their reliability.Even with these shortened procedures, the time taken to obtain a limited amount of information rendered them of little value for the control of milling operations where sudden, large fluctuations can occur. In recent years, a number of new and rapid analytical techniques, based on physical rather than chemical principles, have been introduced.These include direct reading emission spectroscopy, x-ray fluorescence spectroscopy and atomic absorptionspectroscopy.

Jan 1, 1964

By W C. Cook, S J. Mathews, A H. Purvis

The Golden Cross Gold Mine is located at the head of the Waite kauri Ri ver, 8 km northwest of Waihi near the southern end of the Coromandel Range. The mine produces gold and silver from epithermal veins hosted by Miocene andesitic flows and pyroclastics of the Coromandel Group. Golden Cross is owned in joint venture by Coeur Gold NZ Ltd (80 per cent) and Viking Mining Company Ltd (20 per cent). Mining is by open pit and underground methods. Mineralisation in a near-surface sheeted/stockworked vein zone is mined from the open pit. The deeper Empire Vein System is mined from underground where higher grade mineralisation is restricted to generally discrete veins. The open pit stockwork zone is west of and offset from the updip trend of the Empire Vein System. The Empire (hangingwall) Vein strikes generally north-northeast and dips steeply west. Dips become subvertical at greater depth. The hangingwall vein is a well developed, generally continuous structure with relatively high gold grades. A complex footwall vein system forms shallow west-dipping offshoots to the hangingwall vein. Structure and gold grades become increasingly erratic away from the hangingwall vein. The better developed footwall veins carry economic grades and high 'spot' grades over 50 g/t Au are not uncommon. Highest gold grades are associated with tightly crustiform banded sections of quartz veins and with dark fine grained siliceous breccias. The main hangingwall vein occupies a major north-northeast trending fault structure, the Empire Fault. Footwall veining forms within subordinate splinter fault zones. There has been extensive multidirectional pre-, syn- and post-mineralisation faulting. Fault manifestation is highly dependent on host rock characteristics. The central part of the hangingwall vein and surrounding silicified country rock has been shattered by a major fault structure, the West Mine Fault, forming a poorly consolidated, blocky quartz-breccia ore zone. Away from the more brittle ore zones and associated silicified envelope, wide clay-filled shears mark the major fault trends. Development of the deposit is considered to have occurred in two distinct stages related to separate episodes of dilational jog movement on the Empire Fault. The first phase reactivated the pre-existing Empire Fault as a dilational fissure with subordinate splinters on the footwall side. The Empire Vein System (hangingwall and associated footwall veining) formed during this phase. A second phase of renewed movement with further dilation resulted in more extensive fracturing of the Empire Vein and surrounding country rock and formed the sheeted/stockwork veining of the open pit. An upwards/westward migration of the hydrothermal system is assumed but fluid pathways between underground and open pit veining are unclear. Ore extraction and mining geology methods have responded to improved understanding of the grade and structural variability, and changing ground conditions inherent in the vein system. The underground mine produces ore from flatback cut and fill, post-pillar and bench stopes. Open pit and underground ores are campaign milled through a conventional CIP plant.

Jan 1, 1993

By J. G. Pippenger

The mining industry has been Australia?s major economic driver over the past decade, contributing 8% to Australia?s Gross Domestic Product and 26% of Australian Stock Exchange Market capitalisation. Australia is the world's leading exporter in coal, iron ore, alumina, lead and zinc; and second largest in gold and uranium. While driving the economy, this resource boom has also created a demand for professional and operating talent that has far outstripped the capacity of Australia?s 21 million residents. I moved to Australia some 10 years ago and have not looked back. This unique island continent with its mix of Indigenous and diverse immigrants ? many still proud of their convict ancestry ? has offered life long memories both professionally and personally.

Jan 1, 2011

By E. M. J. Alenius

This paper describing the mining practices at the United Verde open-pit mine at Jerome, Ariz., is one of a series being prepared by the United States Bureau of Mines on mining practices, methods, and costs in the various mining districts in the United States. The purpose of this paper is to present the methods used in developing and operating the mine, and to discuss the problems encountered.

Jan 1, 1930

By V. Brabie, S. Jansson, L. Bohlin

The rate of dissolution of solid MgO-C and doloma into liquid in CaO-Al2O3-SiO2-MgO slag at different temperatures was studied under conditions of forced convection by rotating cylindrical refractory specimens in a stationary crucible containing the molten slag. The corrosion rate was calculated from the change in diameter of the cylindrical specimens. Refractory specimens were 13 mm in diameter and 70 mm long. The specimens were rotated for15 to 120 minutes at speeds of 100 to 400 rpm in the molten slag. The rate of corrosion increased with temperature and with the rotating speed of the rod, and decreased when the slag was nearly saturated with MgO. The experimental results confirm the assumption that the diffusion of magnesium oxide through the slag phase boundary layer controls the corrosion process. The corrosion mechanism seems to be the dissolution of the refractory materials into the slag, followed by penetration of pores and grain boundaries and dispersion of the grains in the slag. Keywords: MgO-C refractory, doloma refractory, molten slag, corrosion rate, corrosion mechanism

Jan 1, 2004

By Jeffiey B. Austin, Maurice Tagami

"The ores of the Iberian Pynte Belt are typically massive sulphide ores with very fine grained mineral textures. EuroZinc Mining Corporation is currently evaluating one of the massive sulphide deposits located near the town of Aljustrel, in South Central Portugal. The deposit contains significant grades of lead, zinc and silver. The ores are comprised solely of sulphide mineralization consisting of pyrite, sphalerite, galena and some secondary copper minerals. Liberation requirements for these ores are typically 22 to 25 microns. A selective flotation process has been utilized to produce separate lead and zinc concentrates for sale to off-site contract smelters.This paper outlines the process test results and describes the process parameters required to optimize the process parameters. Ths test program has been conducted in support of the re-opening of the facilities in Aljustrel. The 3500 tpd mining and milling facility was commissioned in 1990 and operated for 18 months before closing. The previous facility was designed to produce three products using a selective copper-lead-zinc flotation process. EuroZinc Mining Corporation is proposing to re-open the operation, selectively mining from a lead-zinc phase of the massive sulphide deposit and produce only lead and zinc concentrates.Results are presented and discussed.PROJECT HISTORY AND CURRENT PROJECT OBJECTIVESThe EuroZinc Aljustrel Project is a potential major producer of lead, zinc and silver located in the Iberian Pyrite belt of south-central Portugal. The town of Aljustrel is historically associated with mining dating to the time of the Romans. The area is rich in pyrite deposits, and sections of the pyrite deposits contain significant zones of copper, lead, zinc and silver. Mining in Aljustrel during the last century (1900’s) included a major pyrite mining operation, which produced feed for sulphuric acid production. Pynte mining operated from the 1930’s to the early 1970’s and a short-lived base metal operation from 1989 to 199 1."

Jan 1, 2000

By S. G. Shabestari, S. Saeidinia, P. Mokarian

"The experiments were conducted to investigate the influence of various process parameters in rotary degassing of aluminum alloy AS5U3G. Degassing was carried out by use of argon inert gas. The flow rate of the gas was investigated in the range of 12 to 21 L/min., 350 to 500 rpm rotor speed, 6 to 12 minutes degassing time, and 755°C to 780°C melt temperature. Degassing efficiency was evaluated through measuring the density of RPT samples. By optimizing the process parameters, RPT sample density was increased up to 2.73 g/cm3, which guaranties the production of high-quality aluminum castings. Tensile strength and elongation were increased considerably by degassing process. Scanning electron microscopy (SEM) shows small size and well-distributed microporosity. IntroductionOne of the major problems associated with the casting of aluminum alloys is the formation of gas porosity. Aluminum and its alloys are very susceptible to hydrogen absorption. Because solubility is much lower in solid state than liquid state, hydrogen atoms leave their position during solidification and combine together to form hydrogen molecules. These micrometer- scale cavities, called microporosity, cause the reduction of mechanical properties, particularly strength, ductility, fracture toughness, fatigue resistance, pressure tightness, and corrosion resistance (Laslaz, 1991; Jorstad and Rasmussen, 1993; Sigworth and Wang, 1994; Korasani, 1996; Anson and Gruzleski, 1999; Zhang et al., 2000). To avoid these problems and produce good quality castings, it is necessary to remove hydrogen from the melt. Several methods are available for degassing aluminum melt. One of them is a rotary degassing system using inert gas, e.g. Ar or N2. Various thermodynamic and kinetic factors govern the removal of hydrogen from molten aluminum (Anderson, 1987; Sigworth, 1987; Pignault, 1993; King and Reynolds, 1995). These are some parameters that affect degassing efficiency. Some of them are discussed here and some are examined in this project."

Jan 1, 2004