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By K. Feindel

The distribution of water in operating fuel cells must be carefully managed to optimize the performance, durability, and functionality of the system. For example, the ionic conductivity of polymer electrolyte membranes decreases as membrane hydration is reduced. Flooding at the cathode inhibits mass transport, and it can lead to failure of materials. Build up of liquid water in the gas flow channels of a fuel cell stack will create a non-uniform distribution of pressure drops across the individual cells. We will discuss the application of 1H NMR microscopy to investigate in situ the production and distribution of water throughout an operating H2/O2 polymer electrolyte membrane fuel cell. Polymer electrolyte direct methanol fuel cells posses high theoretical storage capacities as power systems for portable electronic devices. There are, however, two long-standing hurdles to development of practical methanol fuel cell systems. First, the electro oxidation of methanol at the anode of the fuel cell is poisoned by absorbed carbon monoxide, an intermediate in methanol electro oxidation. Second, methanol readily crosses over from the anode to the cathode of the fuel cell. This methanol crossover wastes fuel, and it poisons the electro reduction of oxygen at the cathode. We are investigating use of 2-propanol as an alternative to methanol as a fuel. 2-Propanol is less toxic than methanol, and it is less prone to crossover from the anode to the cathode. More significant, however, is that the electro oxidation of 2-propanol to acetone is faster than the electro oxidation of methanol because it avoids formation of adsorbed carbon monoxide. We will present active catalyst systems for the electro oxidation of 2¬propanol to acetone in fuel cells. We will also present methods to convert the resulting acetone back into 2-propanol, possibly leading towards rechargeable portable fuel cell systems.

Jan 1, 2005

By Sean Junor

Cameco Corporation ?One of the world?s largest producers of uranium ?Operations in Saskatchewan, Ontario, the United States and Kazakhstan ?Development projects in Australia ?One of the best employers for Aboriginal Canadians Geographic location ?Remote or northern operations ?Northern Saskatchewan ?Residents of Saskatchewan?s north (RSN) ?Wyoming ?Nebraska

May 1, 2010

By J. I. Jr. Moore

Many articles have been written about the various operations of Britannia mines and mill, as well as treatises on the geology and ore deposits. A partial list of these papers is given below. Most of these papers have covered well the history of Britannia, and have included a thorough discussion of the geology and ore deposits; therefore, in this paper, no account of these subjects. is necessary. However, a short description of the ore deposits will be given as an aid to a clear understanding of the descriptions of the various mining methods. The Ore Deposits The ore deposits at Britannia occur along a shear zone and are five in number, named for the claims in which they lie, as follows: Jane, Bluff, Fairview, Empress, and Victoria. Each of these deposits is called a mine, as they are separated by 500 to 1,000 feet of barren ground. The Jane mine, although the first producer of the Britannia group, has not been in operation for a number of years. The deposit is a silicified replacement in sediments; with very little evidence of shearing. The Bluff deposit is a highly silicified replacement in porphyry, massive and irregular, very hard in the upper 600 feet with practically no shearing, and softer within chlorite schist in its lower 1,000 feet . The Fairview deposit consists of a series of twelve distinct veins or lodes, rather lenticular in shape, and occasionally merging.

Jan 1, 1928

By L. I. Kiss, A. Larouche, V. Dassylva-Raymond

Control of the quenching capacity of the cooling water is of primary importance for maintaining the quality and recovery rate of ingots produced by direct chill casting. Industrially, this can be done using a cylindrical metallic probe undergoing rapid quenching by direct immersion in a reservoir filled with casting water. Such a test rig originally developed at Alcan Arvida Research and development Centre was modified and used to assess the role of key parameters affecting the boiling heat transfer. During the tests, the probe of the instrument undergoes the effects of different heat transfer mechanisms. An experimental study was performed in order to clarify the details of the probe-water heat transfer during rapid quenching. The heat flux along the surface was determined by mathematical modeling using the measured temperature signals, while the corresponding heat transfer regimes like stable and unstable film boiling, nucleate boiling and natural convection were identified by the analysis of high-speed video recordings. Aluminium

Jan 1, 2006

By J. Kicki

The paper depicts the current status of the EKSPERT mining machinery management system and shows the prospects for its further development. The system is the result of a rare attempt to utilize the comprehensive dataset; this refers to a precisely identified group of users and is used to develop a solution with a scope that encompasses other areas of activity within the company. The authors present the incredible flexibility and usefulness of the system used at KGHM Polska Miedz S.A. for everyday control of the mining machinery fleet. The issue of visual aspects of the reports generated by the system is handled separately and used as a tool allowing for implementation of the methodological assumptions of EKSPERT. A concept for creating a system for assisting decision making in the process of mine management with the use of IT tools and production monitoring is also discussed. The solution is based on integration of information from both the monitoring field and visualization of the technological process around the Production Reporting Center.

Aug 1, 2013

By J. M. Ortiz, J. Haas, W. Kracht, G. Pamparana

This work explores the effect of ore hardness variability on the design of a solar photovoltaic system with battery storage and grid backup, to operate a semi-autogenous grinding mill (SAG). First, a case of two synthetic ore populations was studied, without any consideration of spatial distribution. The mean and variance of the ore hardness (measured in specific energy consumption) of both populations were subjected to a sensitivity analysis. The operation was evaluated with one and two stockpiles. The latter allows classifying according to ore hardness to adapt the SAG energy consumption to the solar cycle. The results show that using two stockpiles allows achieving a larger autonomy (i.e., fewer energy imports) at lower total costs, especially when the difference of mean hardness between the two populations is large. The difference in variance (between the two populations) has a smaller impact on the design recommendations. Second, a case study was performed considering the spatial distribution of geometallurgical units. Two cases were considered: (a) brownfield, when there is historical information of the actual variability of the ore hardness; and (b) greenfield, when the system design relies mainly on geometallurgical modeling. Brownfield and greenfield planning result in similar sizing recommendations of the solar power plant if precise drill cores are available. In this case, geometallurgical modeling is an effective tool for forecasting the energy demand necessary for designing the power plant. INTRODUCTION Solar energy can help make mining more sustainable (Moreno-Leiva et al., 2017). With falling battery costs, an autonomous solar supply is soon to become an economical alternative in many parts of the world, even in the presence of a larger power grid (Child et al., 2017). Although this, places with high solar radiation such as the Atacama Desert in Chile, nowadays show a large potential of incorporating solar energy as a supply of energy. Many of the Chilean copper mines are in this zone making it interesting to study their compatibility and potential of integrating this renewable source to their operation. The power demand in a copper mineral processing plant is determined by the main power loads in grinding and flotation, with grinding typically the largest power consumer, especially the semi-autogenous grinding (SAG) mills (Wei and Craig, 2009). In Chile, it corresponds on average the 50% of the electrical energy consumption (COCHILCO, 2013). Solar energy production is determined by the irradiance perceived into the solar photovoltaic (PV) panels (which varies through the geographic location) and several other climatic parameters such as the current season, humidity, temperature, altitude, and others (Molina et al., 2017). Also, solar energy is only generated during the sun hours, getting to a maximum generation at a certain peak hour during midday, and finally dropping to zero during the night. This shows a cyclic parabolic profile as shown in Figure 1. Due to the SAG mill operated continuously, the power supply always must be available. During the night, to continue supplying the energy, it is necessary to complement the solar power generation with a battery energy storage system (BESS), which will act as a power backup and a buffer. For the optimal sizing of this PV- BESS system, information of the demand profile is needed (Pamparana et al., 2017). In the case of the SAG mill operation, the resulting demand relates to the ore-hardness for a specific throughput and grind size (Morrell, 2004). Therefore, for a given throughput and target grind size, a harder ore would require more power, and variable hardness results in more variable demand and a subsequent need for larger energy storage (Bueno et al., 2015). Due to the ore-hardness variability and the operation of the mill, the power demand profile in inherently variable.

Jan 1, 2019

By David Dreisinger

Arsenic occurs in nature in association with many valuable metals including copper, nickel, cobalt, gold and platinum group metals. The recovery of these valuable metals is of course complicated by the need to extract and stabilize arsenic in a form suitable for disposal. In this paper, a review of some recent developments related to hydrometallurgical treatment of arsenic bearing materials is provided. The key aspects of metal dissolution, arsenic stabilization and disposal are discussed.

Jan 1, 2014

By D. Lemieux

A gold bearing pyrite concentrate was treated at the pilot scale for the extraction of gold. Mineralogical analysis of the concentrate identified gold to be mainly present in the form of a solid solution in pyrite. This gold distribution resulted in a poor extraction yield of 55% by direct cyanidation. A piloting campaign including an oxidative pre-treatment by roasting in a fluid bed was followed by treatment with halogens for gold extraction has led to a gold extraction yield of 96.5%. Sulphur removal during the oxidation was very efficient at >99.5% and gold extraction by the halogens was completed within a 1 hour contact time. The piloting was performed on a 300 kg sample and uses a diluted solution of hypohalites as the oxidizing agent for gold extraction. Sulphuric acid was injected in the reactor during the halogens treatment to lower pH to 2. The diluted solution of hypohalites (1-3%) was generated by electrolysis during the piloting campaign in a membrane-less electrolysis cell. The extracted gold was recovered over activated carbon in column and the gold depleted brine was treated for impurities removal and recycled for further gold extraction. With the recycling of water and brine, the regeneration of hypohalites and with a barren solid that is inert and stable, the Nichromet Extraction technology is a green process where the protection of the environment does not preclude profitability.

Aug 1, 2013

By Richard Hurteau

Design and validation of an integrated guidance system for articulated ground vehicles is investigated. The development of an autonomous industrial vehicle must take into the account the specific geometry of these vehicles; they can be composed of a tractor with 1 or 2 trailers or of articulated type like LHD. Moreover the tractor-trailers type vehicles can have on-axle hitch configuration or positive/negative off axle configuration. The path-tracking of a tractor-trailer vehicle in restricted space is presented and discussed in this paper. Recent results obtained in simulation and validated by experimentation are also presented. These studies can lead to better ways of maneuvering an articulated vehicle in a restricted space or automatically executing of docking and parking maneuvers

May 1, 2002

By João Felipe Costa, Jair Carlos Koppe, André C. Zingano

Abstract - Traditional mine planning based on block models built with interpolation techniques such as kriging does not take into account the uncertainty associated with the estimates. These models are inadequate for short-range mine planning. In contrast, conditionally simulated models reproduce the actual variability (histogram) and spatial continuity (variogram) of the attributes of interest. Conditional simulation can be used to address the problem of measuring the uncertainty associated with an estimate. This paper outlines how the sequential Gaussian conditional simulation algorithm can be used to assess uncertainty of grade estimates and also illustrates how simulated models can be incorporated into mine planning and scheduling. A case study demonstrates the efficiency of the method in assessing risk associated with geological and engineering variables.

Jan 1, 2000

By T. G. Joseph

The strain softening relationship developed in part 1 is now applied to coal. Having determined the post-failure stress-strain curve for coal specimens, this information can then be used in a finite element program, such as Phase 2, to examine the post failure characteristics of coal pillars. Using example data, the strength of coal pillars of different width/height ratios are estimated and compared with well-known empirical pillar size-strength relationships. In addition, the post-failure stress-strain behaviour of a coal pillar is compared with an empirical relationship reported in the literature.

May 1, 2002

By John S. Stevenson

"Although we have no uranium- producing mines as yet in British Columbia, uranium, associated with gold and cobalt, has been found in two deposits in amounts such that the combined value of the metals not only warrants the further exploration of these deposits, but also encourages the search elsewhere in the Province for other similar deposits.Where uranium-bearing veins have been found in British Columbia, the uranium mineral is the crystalline variety of uranium oxide, uraninite, rather than the massive, non-crystalline variety, pitchblende, such as found in the Great Bear Lake deposit and in other similar deposits along the southwestern margin of the Precambrian shield.The principal occurrences of uranium known so far in British Columbia are associated with bodies of granodiorite and quartz diorite along the eastern side of the Coast Range belt of batholiths. In this part of the Province, interesting amounts of uranium occur on the Gem property in the Bridge River area and on the Victoria property south of Hazelton; and smaller amounts occur on the Red Rose, Rocher Debouze, Delta, and Ohio properties, also south of Hazelton. At the Gem and the Victoria, the uranium mineral, identified as uraninite, occurs in deposits that also contain abundant cobalt-nickel sulpharsenides, and molybdenite.At these properties, the uraninite occurs as clusters of small black crystals of sub-metallic lustre that may be seen upon careful -searching of a highly radioactive specimen with a hand lens. Under the microscope, the uraninite is seen to be in the form of cubes or modifications of cubes that may occur as individual grains widely scattered throughout the gangue or may be gathered into clusters of several grains. The grain size of the uraninite is in general small. Although a few clusters of grains are up to about 10 mesh in diameter, the individual grains, whether in clusters or widely disseminated, are rarely more than 400 mesh in diameter."

Jan 1, 1950

By Jin-Hwa Song

Rolling temperatures and cross rolling ratios were varied to investigate the effect of crystallographic texture of alpha-phase on the anisotropy of mechanical properties in modified Ti-6A1-4V alloy. Hot rolling method was unidirectional and cross rolling, during which the rolling temperature was in the range of 830°C and 920°C. Cross rolling ratios were varied from 0.3 to 1.0 at 875°C. For unidirectional rolling, as the rolling temperature increased texture changed from the mixed basal and transverse texture to the simple transverse texture. Contrary to other work, it was observed that the maximum intensity of transverse components increased with the increase in rolling temperature. For cross rolling, on the other hand, the transverse texture component was almost suppressed at 830°C, giving rise to a symmetrical basal texture. With increasing cross rolling temperature, the transverse texture components developed again. A simple transverse texture, which showed two maxima appearing circularly 90° apart, was observed at 920°C. It was found that unidirectional rolling could not eliminate the transverse texture, which resulted in the anisotropy of mechanical properties. The anisotropy of mechanical properties obtained from tensile and V-notch Charpy test was closely related to the crystallographic texture and its intensity at each rolling condition. To obtain the isotropy of mechanical properties by cross rolling, it is suggested that cross-rolling ratios should be controlled above 0.5. The variation of rolling temperatures and directions has great influence on the anisotropy of impact value rather than tensile strength.

Jan 1, 2004

By Robert J. McCarthy

Many technologies have been adopted over the last half century for the haulage of material from open pit mining operations. Some of the technologies utilized include rail, off-highway trucks, conveyors, and slurry pipelines - each having its unique application and benefits. Over time, truck haulage has become the primary means of surface mine material movement, though recently it has been plagued by problems of tire shortages, high diesel fuel costs, labour shortages, and carbon emissions. This paper focuses on In-Pit Crushing and Conveying (IPCC) as a competitor to truck haulage which has the potential to solve many of these problems. An overview of the available technology is presented along with measures required to overcome perceptional if not physical barriers to implementing this technology in modern open pit mines.

May 1, 2011

By M. Hawker, M. Kreuh

The mining and metallurgy industry is known to be of cyclical nature associated with price volatility. As such, some years are quite lucrative and other years require mining companies to tighten their belts. The field is a mix of junior, mid-tier, and major mining companies. One thing that is common to all of them is the time required and the cost to develop a flowsheet in accordance with best practices. Although a long list of factors can impact flowsheet development, this paper will include the impacts of: experienced metallurgical engineers and laboratories, representative samples for high quality and valuable testwork results, and following engineering development stages. The paper also provides typical time frames to complete selected engineering flowsheet development steps.

Jan 1, 2014

By J. A. Drozdiak, A. Bamber

In this paper we examine, through pilot-scale testing, the possibility of operating a circuit comprised of two stages of HPGR comminution, followed by grinding through a horizontal stirred mill. In order to assess whether the novel circuit design could achieve the reduced energy requirements indicated in the literature, two more-established circuits, a cone crusher / ball mill and an HPGR / ball mill, were examined using a combination of testing and flowsheet simulation. The results showed that, based solely on the specific energy requirements for comminution, the HPGR / stirred mill circuit achieved a reduction of 9.2% and 16.7% over the HPGR / ball mill and cone crusher / ball mill circuits, respectively.

Jan 1, 2012

By Rainer Süss

An investigation was carried out by Mintek to investigate the influence of a range of alloying additions (vanadium, cobalt, zirconium, antimony and germanium) on the formability and hardenability of alloys with gold content >90 wt%. This paper reports on the hardening mechanisms that can be utilised to increase the hardness of gold (>90 wt% Au) by conventional alloying, as well as the hardening effect obtained by alloying with specific elements. Preparation methods for the alloys are described, which include the steps of melting, annealing, quenching, cold working and age hardening. Focus is given specifically on alloys that were developed at Mintek with a gold content >90 wt%, which are not only harder, but exhibit good resistance to tarnishing and corrosion.

Oct 1, 2003

By Yongqiang Liu

Background For refractory gold ores with high carbonate contents ! Acid pressure oxidation ! High acid consumption (if low sulfur content) ! Low oxidation efficiency due to CO2 in autoclave ! Problems with slimy precipitates (gypsum, etc.) ! Alkaline pressure oxidation ! Difficulty in fixing arsenic ! Low gold dissolution due to iron hydroxides/oxides coating ! High reagent costs Summary ! Carbonate and sulfide minerals had similar floatability across the pH range tested (5 - 12) using sodium oleate as a collector; ! Thioglycollic acid or citric acid depressed the flotation of pyrite but could not depress chalcopyrite when used alone; ! Combination of thioglycollic acid and citric acid had a much stronger depressive effect, and the mixture depressed chalcopyrite as well as pyrite between pH 8 and 11 without affecting the flotation of calcite and dolomite; ! Calcite could be separated from chalcopyrite and pyrite; dolomite could be separated from pyrite but not from chalcopyrite under the tested conditions.

Apr 1, 2005

By J. A. Russell

"UNTIL the last few years, the collieries of the Dominion Coal Company, Limited, while highly mechanized as to the cutting and transportation of the coal, still relied on the hand-loading of coal from the seam onto face conveyors. In these circumstances it was possible to assure that no large proportion of extraneous materials would be loaded with the coal, and the product could be quite well cleaned for the market by screening and hand-picking.Within the past few years, however, the Company has introduced an intensive programme of mechanization which will result in the virtual elimination of hand-loading .of coal. It has been the experience of other producers that mechanical loading inevitably leads to a very large increase in the amount of impurities in the product. This is occasioned by the fact that, at least up to the present, all types of loading machines have relied on the coal being broken from the seam by under-cutting and shooting. In this operation, a certain amount of roof and pavement material inevitably becomes mixed with the coal and, since selective loading is impossible with a loading machine, all this foreign material is loaded out with the product."

Jan 1, 1952

By H. Wilhelm, W. I. van Drunick

The Anglogold Ashanti (AGA) Navachab single stage SAG mill has provided an excellent setting for incremental optimization. Over the past decades, several interventions have resulted in marked improvements in specific performance; including steel ball scat removal, re-design of the mill lifters, replacement the pebble crusher and cyclone cluster, as well as the use of a vibrating screen in place of a discharge trommel. Recent initiatives now include an operating fine DMS circuit, studies on pre-crushing of the ROM feed and also fine-screening as an alternative to hydrocyclone classification. The current optimized state of the Navachab mill allows it to operate at approximately 20% higher efficiency when compared to mills of similar shell dimensions in gold mining, treating similar ore. This paper describes the systematic improvement of the SAG circuit to its current state.

Jan 1, 2012