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By Daven N. Compton

The optical properties of Au nanoparticles have been known for some time, with both Au colloids and Au nanoparticles embedded in glasses having been extensively studied. In this study, Pt nanoparticles have been incorporated into Au colloids, and the linear and non-linear optical properties investigated. UV-VIS spectrophotometry, fluorescence spectroscopy and the z-scan method have been used to examine the effects of such additions.

Oct 1, 2003

By LESTER W. STRAUSS

OUR early knowledge of history and geography attracted most of us to the mineral resources of South America. The romantic tales of the Spanish activities, which were curiously alluring, and Prescott's exceptional bi-Conquest histories-Mexico and Peru-no doubt fired our minds with the .then metallic wealth of the Spanish colonies. Later developments, intensified within the past eighty years, have, however, changed its fame which now rests on such metallics as copper and tin, and among the non-metallics on nitrate of soda and petroleum. South America proper, excluding Panama, is made up of thirteen countries, a coincident parity with our original thirteen States. Its area is given as 7,231,300 square miles, or slightly less than North America (8,037,000 square miles), is made up as follows:

Jan 1, 1930

By Ernest Baafi

A simulation model RoadSIM using the ARENA modelling system has been developed to evaluate roadway development options for a given development panel configuration. The RoadSIM simulation system has provisions for variability/randomness in operations including cutting and loading at the face, tramming and discharge of coal to the boot end and availability of equipment. The modelling system provides a means for assessing the operational limitations of roadway development practices at a particular coalmine. It is a ?what if? tool that allows a range of equipment, configurations and operating practices to be assessed in terms of achievable advance rates and equipment utilisation. Output from the system is in the form of a dynamic visualisation as well as summary reports and detailed logs of operations over time.

Oct 1, 2009

By Vern L. Kegler

This paper is one off a series dealing with mining methods and costs, sponsored and published by the United States bureau of Mines. ACKNOWLEDGMENTS The author acknowledges the, constructive and helpful suggestions and criticism of W. F. Lamoreaux, vice-president, and general manager of the Ducktown Chemical & Iron Co. United States Geological Survey Professional Paper- 139, by W. H. Emmons and F. B. Laney, has been drawn upon for some of the information contained in the paragraphs or history and geology.

Jan 1, 1931

By Yannis Faitakis, Simon Bergeron

"This paper describes the implementation of model-based predictive control (MPC) on a vacuum heat exchange network at Alcan's Jonquière Complex. The plant produces alumina from bauxite ore using the Bayer Process.The MPC system was commissioned in 2000, by Alcan personnel and an Advanced Control Engineer from Matrikon. The application has achieved an uptime of about 97%.The benefits were:• Energy savings : 0.5% - live steam reduction• Reduced variation: standard deviation of key temperatures reduced by 50%• Plant throughput increase: via the automated use of surge tanks• Decreased supervision time: by plant operations• Faster and easier diagnosis of problems and plant constraintsThe benefits were higher than expected with a payback time around 12 months.The purpose of the vacuum heat exchange network is to recover energy from a hot stream (pregnant liquor) by transferring it to a cold stream (spent liquor). The system is very tightly coupled, and the main constraints of the multivariable control system are: • to control the many tank levels involved in the process (8 tanks)• to maximize the temperature of the heated streams (spent liquor)• to prevent cooled streams (pregnant liquor) from cooling to below a minimum temperatureThe system includes 9 manipulated, 14 controlled and 2 feedforward variables.The advanced control implementation runs under an expert system environment and provides added flexibility to the overall control strategy."

Jan 1, 2003

By Wilbur I. Duvall

This paper discusses general principles of underground opening design based on the concept that with the necessary input data regarding the geology of a site, the physical properties of the rocks, the in situ stress field in the rock and the general geometry of the underground openings, the rock formation can be classified into six major categories which are useful for design purposes. Using simple theories for the criteria of failure for rock In compression and tension, general elastic theory for stress concentration around openings and In structures, beam theory for stability of roof rock, and elementary inelastic theory for creep phenomena, basic design techniques are outlined for the various rock classifications. The need for field evaluation of the theoretical design is stressed and some general techniques that should be used in these field evaluations are discussed. Where appropriate, the need for additional studies and research is noted.

Jan 1, 1977

By David Mitchell, Daan Delport, Frik Marx, Mike Shapiro

The use of copper cooling elements to enhance refractory lining life in pyrometallurgical vessels is common in modern furnace design. Copper elements typically incorporate a base panel with cast in cooling passages and an integral extended surface (formed of pins, fins or similar) onto which suitable refractory material is cast. The metallic, conducting parts are located towards the cold face of the lining, with the refractory material interposing between the coolers and the process. The coolers are designed to arrest wear of the refractory material by freezing a layer of slag or partially reacted material onto the hot face, thereby rendering the lining inert to further attack [1]. These coolers have achieved success in new furnaces and relining of existing vessels. The freeze layer is prone to mechanical damage during operational and process instability. The coolers must be capable of extracting the additional heat flux under upset conditions to facilitate rapid self-repair of the freeze layer and prevent further refractory wear in the intermittently exposed areas. However, operational experience has shown that the high heat flux capabilities of the copper coolers have some disadvantages, especially in processes producing vapours which form corrosive compounds when condensing onto the cold surfaces of the coolers. When corrosive conditions develop, the entire composite will fail due to loss of structural integrity, and as a result of leaks from the cooling water passages. This paper describes recent developments in the approach to the design and manufacture of copper cooler panels customized to achieve specified heat fluxes and temperature profiles, thereby reducing the formation of corrosion mechanisms in applications with corrosive gaseous environments and enhancing refractory lining life. Condensation formation prevention is achieved by adjusting the geometry of the cooler and selection of suitable materials of construction.

Jan 1, 2007

By P. Campbell, E. M. Gardy, L. Hachkowski

Introduction The efficient process control of a uranium mill and its associated mining operation requires a nearly continuous knowledge of the uranium concentration in the ore. Generally, the approach is to use laboratory assays of grab samples from the mill feed belt. In some cases, elaborate and expensive systems have been used to ensure random sampling, but even with these systems, mass-balance discrepancies still exist. There is a requirement for an on-line instrument that can give a prompt, accurate analysis of a large portion of the feed stock. The authors have recently evaluated a laboratory system that achieves these goals using neutron activation and delayed neutron counting. The development of the on-line uranium ore analyzer is a consequence of previous work done at the Whiteshell Nuclear Research Establishment (WNRE) (Campbell et al., 1978 and 1981), and is based on the emission of delayed neutrons after the neutron irradiation of fissionable materials. The mechanism of delayed neutron emission has been described (Keepin, 1965), but briefly is as follows. The fission fragments resulting from irradiation are in an excited state. Certain of these delayed fission products, precursors, decay to a more stable state by the emission of a delayed neutron. The delayed neutrons can be divided into six groups with effective half-lives ranging from 0.2-55 sec. It is important to note that more than 50% of the delayed neutrons are emitted within the first 6 sec after irradiation; this has an influence on the design of the analysis instrument. Measurement Cycle The measurement cycle involves a neutron irradiation, a delay time, and a counting period. The laboratory demonstration model of the ore analyzer comprises a californium-252 neutron source, a source chamber, a pneumatic transfer facility, and a neutron irradiation and counting module (Fig. 1). The ore sample is placed in the irradiation chamber. The neutron source is transferred to the center of the chamber for a 5-sec irradiation while the helium-3 thermal neutron detectors are switched off. As the source returns to the storage chamber, the detectors are switched on and the delayed neutrons counted. The total assay cycle is 16 sec. The current instrument design calls for the ore to be cut from the main belt every 16 sec by a mechanical arm and dropped into the analyzer directly, or via another belt. The cycle starts when there is a sufficient mass of ore in the irradiation chamber to depress a switch and stops when the delayed neutron count is finished. The ore is then dropped through the bottom of the analyzer chamber and returned to the main belt. The counts from each cycle are accumulated and the data reduced to give the desired information. Key for Fig. 1 A-Helium-3 neutron detector B-Wax moderator for neutrons C-Irradiation chamber D-Funnel for receiving ore E-Gate F-Transducers G-Biological shield for neutron source H-Transfer tube for neutron source I-Neutron source J- Microprocessor K-Accumulator for hydraulics L-Control panel M-Electro-hydraulic servo valve to control movement of the source N-Electro-hydraulic proportional valve to control movement of the gate O-Hydraulic power unit Irradiation and Counting Equipment Irradiation of the ore is achieved using a 1 X 10 7 neutron*s-1 californium-252 neutron source. The source is contained in an iron capsule and pneumatically transferred between the irradiation/counting and storage chambers. The irradiation/counting chamber possesses 12, 600-mm (24-in.) long helium-3 thermal neutron detectors embedded in an annulus of wax (Fig. 1). Two sets of six detectors are each interfaced to a preamplifier, amplifier and single-channel pulseheight analyzer system, and the two systems are connected to a scaler. A special timing unit controls the transfer of the source and the on and off switching of the detector assembly, in sequence with the movement of the source. Results and Discussion In the experimental demonstration, using the 107 neutron.s-1 source, a 10% uranium ore was measured to ± 10% (2o total error) in 10 cycles and ±6% (2o) in 100 cycles. Since a larger source was not available, it can be statistically predicted that a 109 neutron-s-1 source could be used to measure a 0.1% ore to ± 10% (20) in 10 cycles. The uranium can occur as discrete nonhomogeneous particles in the ore, and the error caused by such a distribution of particles is ± 4% (2o), as determined by

Jan 1, 1984

By R. C. Gegg

The property of MacLeod-Cockshutt Gold Mines, Limited, is in the Little Long Lac area of the Thunder Bay Mining Division, Ontario, about four miles south of the Canadian National railway station of Geraldton. The town of Geraldton is about 170 miles east of Port Arthur and 22 miles west of Long Lac, which is on the main line of the Canadian National railway. The Trans-Canada highway passes through the property and during the winter season the road is maintained between Port Arthur and Long Lac. Electric power is supplied by the Hydro-Electric Commission of Ontario from their Cameron Falls plant and is distributed at 44,000 volts by a local transformer station. Early History The South orebody was discovered by diamond drilling in the spring of 1936. This is a porphyry contact orebody with major pyrite and minor arsenopyrite mineralization. Some gold is present in the 'free' state, but for the most part it is locked in the pyrite, with little or none in the arsenopyrite. Preliminary test work was based on comparing straight cyanidation with bulk flotation and cyanidation of the concentrates. The overall results by the two methods were found similar, but for economic reasons the flotation-cyanidation process was adopted. Before the mill came into operation, a new and entirely different type of orebody, consisting of massive sulphide lenses in banded iron formation, was discovered to the north of the existing workings. These bodies are an intricate mixture of pyrite and arsenopyrite, both carying gold.

Jan 1, 1949

By A. M. Cameron

THE HOISTING PLANT at the Stobie section of the FroodStobie mine is a two-shaft installation designed to handle a daily production of 18,000 tons of ore at depth. The two vertical shafts are within 100 feet of -each other, an arrangement made to provide the needed capacity and to give flexibility of operation (Figure 1). No. 7 shaft, used for handling men and supplies as well as for hoisting ore, has been sunk to the 3000 level and is served by a manhoist handling two cages and an orehoist with two 14-ton capacity Kimberley skips. No. 8 shaft, so far completed to a depth of 1,900 feet, handles only ore. The hoist is semiautomatic with push-button control and the skips are 15-ton capacity bottom-dump. The ore-loading pocket for first stage hoisting at both shafts is 120 feet below 1,600 lev-el and additional pockets are planned, as the shafts are deepened, at 800 foot intervals down to 4,000 feet.

Jan 1, 1956

By Saba Gharedash

In this study the results of a series of numerical simulations which are conducted for one of the tunnels of the Mashhad metro line 2 project are presented to evaluate the role of tunnel face support pressure and soil strength parameters on deformation of tunnel lining and face deformation. To achieve this goal, comparative numerical simulations of a mechanized tunnel advance in soft non- homogeneous soil on top of the ground water table and beneath the building are conducted and sensitivity analysis is performed. Development of a step by step tunnel construction process is modeled using a three dimensional finite difference model (FLAC3D) taking into account all the relevant components of shield tunneling. In order to understand the mechanism of the effects of a variety of support pressures on face deformation and lining stresses, numerical simulations are conducted. It is found that the use of different face supports causes a considerable influence on the forces of tunnel lining. In addition, it is revealed that building weight help to change the stress paths and the stress distributions in the tunnel lining.

Aug 1, 2013

By S. M. Moore

Technological advances in underground coal mining have reduced fatalities but may not have reduced worker exposure to cumulative injury risk factors. The objective of this study was to evaluate the prevalence of cumulative injuries before and after the implementation of technological advances in underground coal mining and to make a general cost estimate for these injuries. A previously published algorithm was utilized to identify cumulative injuries within the Mine Safety Health Administration (MSHA) database for two data sets: 1983-1984 and 2003-2004. For both, the following were determined: the number and percentage of cumulative injuries, the average days lost, the average age at the time of injury, the average years of experience and the general cost estimate by body part. The percentage of cumulative injuries remained largely unchanged (37 percent in the 1983-1984 period and 33 percent in the 2003-2004 period). The average number of lost days due to cumulative injuries increased (36±55 days and 62±82 days, respectively), which may have been due to the increased worker age (seven years older in the 2003-2004 period), increased length of employment (seven years longer in the 2003-2004 period) or other factors such as changes in medical practices. Cumulative injuries to the back decreased by 10 percent, while cumulative injuries to the knee increased by 8 percent. The reduction in back injuries may be due to the implementation of assist devices, while the increase in knee injuries may be related to kneeling/crawling in low-seam mines. Cumulative injuries were found to remain a major financial burden on the industry. Recently, National Institute for Occupational Safety and Health (NIOSH) developed tools to assist mining companies with incorporating an ergonomics process into their existing health and safety programs. The participating companies have reported tremendous success. Therefore, it is recommended that ergonomics processes be implemented as a means to systematically identify and address the root causes to cumulative injuries and ultimately reduce costs.

Jan 1, 2008

By Jeremy Theys

The Sacramento Regional County Sanitation District (SRCSD) is improving the sewer system in the Natomas area of Sacramento, CA. The Upper Northwest Interceptor (UNWI) system is an ongoing series of tunnel pipeline projects that will provide sewer conveyance for all residents of northeast Sacramento County to the New Natomas Pumping Station, located North of downtown Sacramento, also in the city of Sacramento limits. The New Natomas Pumping Station then carries wastewater flowsto the Sacramento Regional Wastewater Treatment Plant in Elk Grove via the existing Lower Northwest Interceptor. The Joint Venture of Traylor Brothers, inc. and J.F. Shea (TSJV) were awarded the UNWI 1&2 project in late September, 2007. The planned 5.8 km (3.65 mile) construction route for UNWI 1&2 begins at the New Natomas Pump Station and runs north along the East Drainage Canal to the begin-ning of UNWI 3&4 at Bridgecross Drive. UNWI 1&2 includes approximately 5.8 km (19,240 feet) of 3.65 m (144 inch) inside diameter pipe using Earth Pressure Balance Tunneling Methods. The project also includes 16.76 m (55 feet) of 3.04 m (120-inch) diameter interceptor pipeline, twenty three access manholes spaced approximately 305 m (1,000 feet) apart along the alignment, a 2.13 m (84-inch) by 3.65 m (144-inch) transition structure, a 3.65 m (144-inch) by 3.04 m (120-inch) transition structure, and the connection of three existing sanitary sewer lines to the interceptor.

By P. Massi

"Wholly owned by the Coniagas Mining Company, the oldest continuously listed mining company on the Toronto Stock Exchange, St. Andrew Goldfields is located on Hwy. 101 approximately 30 miles east of downtown Timmins, Ontario. Geographically situated on the Porcupine-Destor Fault, the mine and mill in Stock township is positioned in the heart of Northeastern Ontario's goldmining communities.In July 1988, a 600 ft. shaft, hoist, and compressors were already in place when construction started on a 500 T.P.D. capacity C.I.P. mill and crushing plant.By June 15, 1989 the mill was commissioned and attained the design capacity by August of that same year. Since then, changes to the circuit have increased throughput to 900 T.P.D. from two significantly different ore sources.Meeting the Ministry of the Environment's guidelines is an ongoing commitment utilizing the Inca S02 process in line between the tailings pond and secondary polishing pond.INTRODUCTIONExploration on what is now known as St Andrew Goldfields' Stock Township Mine was carried out ln the early l960 1 s by Hollinger Mines Ltd. The property was acquired by Quebec Sturgeon River Mines 1n 1973 and the main shaft was started ill 1979.When St Andrew Goldfields was incorporated 1n 1983, exploration and development commenced to identify the ore body. The company decided 1n 1987 to bring the Stock township property into production after an extensive feasibility study and testwork at Lakefield Research in Toronto. Leslie Engineering was contracted to design, engineer and procure al 1. equipment from the coarse ore bin to the tailings distribution system and backfill plant"

Jan 1, 1992

By Andrea Koschinsky, Peter E. Halbach, Margret Halbach, Andreas Jahn

"Ferromanganese crusts contain hydrous Mn and Fe oxides as main metal compounds together with some economically interesting minor elements such as Co, Ni, Ti and Cu and trace metals such as Mo, W, Nb, Te, Ga, Pt, and REEs. Some of these metals or semimetals have a great future potential as innovative high-technology constituents. All of them are highly enriched in the crusts compared to seawater composition.The Mn in the crusts mainly originates from the O2 - minimum zone in the oceanic water column. The agent for Mn2+ oxidation is dissolved oxygen, transported upwards from colder deep water layers by turbulent eddy diffusion. The Mn itself descends from surface waters and is carried down to the O2-minimum zone by fecal pellet transport. In contrast, Fe is mainly supplied from carbonate dissolution of planktonic skeletons in the water column. These relationships result in the fact that the oceanic water depth strongly controls the metal composition of ferromanganese crusts: the Mn - group metals are more enriched in shallower water, whereas the concentration of the Fe - group metals increase with water depth. The REEs play a very important role with regard to the trace metal composition of the crusts: their concentrations increase with water depth mainly controlled by a decreasing Mn/Fe ratio.In seawater, REEs occur as carbonate complexes; preferably, the light rare earth elements (LREEs) form REECO3 +(aq) and the heavy Rare Earth Elements (HREEs) REE(CO3)2 (aq) complexes. The REEs are transition metals, their 6s orbital of the outermost shell is filled before the filling of lower 4f electron shells is completed, thus the configuration of the valence electrons is similar in all the REEs, and all REEs exhibit similar chemical behavior and exist, dominantly, as 3+ cations. The ionic radius decreases progressively from La3+ (1.18 Å) to Lu3+ (0.97 Å), this phenomenon is called "lanthanide contraction". Due to the fact that REEs in seawater form cationic and anionic carbonate complexes, the two main hydrogenetic constituents, hydrous !-MnO2 and Fe-oxyhydroxide, fractionate the group of REEs by surface absorption processes. According to the pHZPC-concept the ?- MnO2 phase has an electronegative surface, and Fe-oxyhydroxide a slightly positive surface charge at seawater pH. These relationships are the main reason for the observed REEs fractionation."

Sep 1, 2014

By T. Phiri, Antoine Floribert Mulaba-Bafubiandi

Microwave energy has been recently used in minerals processing to speed up the leaching process or to improve the liberation of targeted minerals (Al-Harahshed and Kingman, (2003); Bradshaw et al., (2001)). Applied to the roasting of sulphide minerals, microwaves allow the ?tunning? of calcine types and products quality in addition to the energy savings as opposed to the conventional roasting (Mulaba, 2006). As more than 85% of world zinc is produced through the ?roast-leach-electrowin? route, an attempt was made to optimize cost, energy and product quality for metal extraction process route. The use of microwaves was the alternative process route selected for the optimisation. Pyrite concentrate (0.17% Zn, 0.09% Cu, 35.71% Fe, 43.76% S) and sphalerite concentrate containing 43.81% Zn, 0.37% Cu, 3.86% Fe and 44.39% S were microwave roasted in a multimode cavity of 2.45 GHz with varying power levels and for different durations. The produced calcines were characterized using AAS, XRF, XRD and Mossbauer spectroscopy while the determination of residual Sulphur was used as products quality control tool to ascertain the degree of roasting achieved on the feed. The leachability of the produced calcines in HCl, HNO3, H2SO4 and HNO3 + HCl has been studied in terms of the best leaching yield, process kinetics economics and environmental aspect. With 800 W power for 30 minutes, ZnO and Fe2O3 were formed corresponding to a 70% sulfur removed from sphalerite and 80% from pyrite concentrates respectively. While the roasting of the above concentrates appeared to be a first degree processes, it was noticed that the microwave assisted roasting of sphalerite and pyrite concentrates yielded lower sample surface temperature for a shorter time (i.e.less than 30 minutes) microwave exposition. Longer time (more than 30 minutes) microwave exposure showed a linear increase in temperature in function of power level used. While optimum roasting conditions were found at 800W, 30 minutes, a 10% increase of sulfur removal was noticed while pyrite concentrate was microwave roasted. Sulfuric acid was seen to give higher leaching yield than nitric acid. Zinc dissolution was hindered by the presence of franklinite.

Jan 1, 2007

By Gungor Tuncer, Ali Kahriman, Abdulkadir Karadogan, Umit Ozer, Ertugrul Kaya, Kagan Ozdemir

The results of bench blasting on quarries, have important influences on the performance of subsequent mining activities such as loading, hauling, crushing, grinding etc., and the total costs of that mine. Drilling and blasting is an important step in mine producing chain and its results such as fragmentation, muckpile shape and looseness, dilution, damage and rock softening effect the efficiency of downstream processes. Within the scope of this study, the three different hydraulic excavators’ working performances have been studied considering the particle size distribution after bench lasting at a quarry in Istanbul Turkey. Five shots have been realized on the quarry and average particle size of muckpile after each shot were assessed by digital image analysis method. Bucket loading times have been measured by stopwatch study after five shots. Excavator bucket loading times were also estimated by bucket loading time estimation formula which was published in ISEE 2007 Conference, Ozdemir et al. 2007. Estimated and measured times have been statistically analyzed and the accuracy rate of formula has been determined for five events.

Jan 1, 2008

Improvement of Phosphate Ore Flotation Performance Through Sized Flotation

Sep 13, 2010

By W. Pozo

En 1959, la concentradora Toquepala inicia sus operaciones con una capacidad limitada de 38,500 toneladas de mineral por día. En ese sentido, se inició un programa de investigación para modernizar y optimizar las operaciones de la concentradora en el futuro. Entre los logros obtenidos a partir de dicho programa están: la reducción del consumo de energía en el proceso de flotación de la planta de cobre, como del consumo de Asmol en la planta de moliddenita, así como se la reducción en el consumo de reactivos. En consecuencia, el presente trabajo señala la evaluación metalúrgica de la operación de la concentadora de Toquepala a futuro y los resultados de la aplicación del programa.

Apr 1, 1991

By David J. Dunn, Richard G. Martin

Of many physical parameters critical to design of grinding processes, impact of grinding media is among the most difficult to measure or predict. Yet impact of falling grinding balls, pebbles, or rods accomplishes the fine grinding essential to metallurgical recovery of most important minerals. Unfortunately, the same impacts that break ore fragments deform or crack grinding mill liners. A project was undertaken at Climax Molybdenum Company to measure impact forces in operating ball mills so that they might be used to calculate stresses in liner materials and be correlated with service performance of mill liner alloys. Towards that end, a method of measuring impact forces on ball mill liners using an instrumented grinding ball has been developed. Preliminary tests show that impact forces and contact stresses imposed on bare mill liners are quite high but are greatly reduced by cushioning when coarse ore particles are crushed between balls and liners. Compressive and shear stresses induced in liners not protected by coarse ore are so severe that deformation or minute subsurface cracking are inevitable in all but the small production grinding mills, regardless of mill liner alloy strength or hardness.

Jan 1, 1979