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By Les F. Sawatsky

Surface drainage, particularly mine closure drainage, must be properly considered during all stages of mine planning because it presents constraints that are critical to economic mine operation, minimizing environmental impacts and ensuring compliance with government regulations. Deficient mine site drainage increases costs of operation, causes unnecessary environmental impacts and may result in regulatory violations. The scope of this paper includes stream diversions around mine areas, drainage systems within the mine disturbed footprint, and closure drainage works to control surface water, ground water, erosion, sedimentation, and seepage discharges following mine operations. Developing selfsustaining drainage facilities upon mine closure, requires a mine plan that develops appropriate topography and constructed drainage courses that replace the function of pre-disturbance drainage systems without aggravated erosion and deterioration. Drainage criteria, particularly closure drainage criteria, represent important constraints on mine planning and are best considered by integrating drainage features into the mine plan well in advance of mining activities. Integrated mine planning by a multi-disciplinary team is recommended to achieve closure objectives at minimum cost and maximum effectiveness The geomorphic approach to channel design is an effective means of providing a drainage system that has the appearance, function and longevity of natural systems. By incorporating this technique into closure drainage planning, mine operators can construct sustainable (walk-away) drainage systems that require little or no maintenance in the long-term. This paper presents a process by which drainage criteria and associated mine plan constraints can be integrated into the mine planning process. This paper outlines the process for detailed design of drainage facilities, particularly closure drainage systems that are designed by the geomorphic approach.

May 1, 2009

By Michel Aubertin

Using mine wastes as backfilling material for underground stopes has been a common practice for more than 60 years. Waste rock and tailings are used as filling materials because they are available at a reasonable cost to support the rock walls. Backfilling is also very advantageous because it reduces the amount of mine waste disposal on the surface. In underground mines, the backfill must first ensure stability of the opening, while increasing recovery of ore and minimising dilution. It is thus critical to accurately evaluate the pressures exerted on the walls and on the barricades placed near the base of the stope. In this presentation, existing solutions for evaluating the stresses on stope walls and barricades are briefly reviewed. The authors then present recently developed analytical solutions that take into account the stress transfer from the backfill to the walls in the stope and access drift. The stress state solution, which is based on arching theory, considers the influence of the stope geometry and barricade position within the drift. The method gives the pressure generated by partly or fully submerged backfill. The solutions apply shortly after backfill deposition, when the effect of pore water pressure cannot be neglected, and also for long term conditions under a fully drained state. Experimental testing and numerical modelling results are used to validate the proposed equations. Both numerical and analytical results show that the total pressure on barricades can be significantly increased by water pressure, while the effective stress is decreased (compared to dry or drained conditions). A discussion follows on the implications of the results for backfill applications.

Nov 1, 2008

By S. Afshar, E. Dajoux, C. Allaire

For various reasons, molten salts, mainly chlorides and fluorides, are used in the aluminum industry. In the holding and melting furnaces, these salts may have different roles such as protecting the metal from oxidation, reducing the metal content of the skim or removing inclusions or impurities from the metal bath. However, the use of these salts may also have some undesirable effects such as easy attack of the furnace lining refractory materials by molten aluminum. The aim of the present investigation was to clarify and to compare the effects of chloride versus fluoride salts, on the corrosion process of the aluminosilicate based refractory materials. A laboratory test and procedure, simulating the conditions at the metal line in the aluminum treatment furnaces, was used. Different aluminum alloys (A1-5wt.%Mg, A1-5.5wt.%Zn and 7075 alloy) and chloride or fluoride salts (MgC12, KC1, CaCl2, NaC1, MgF2, CaF2, NaF and cryolite) were used as well as several aluminosilicate materials. Thermogravimetric measurements were also carried out in order to analyze the effect of the salts on the oxidation of molten aluminum alloys. The experimental results showed that fluoride salts are more aggressive than chlorides against the tested refractory products. It is postulated that the fluorides prevent the formation of a protective oxide layer on the metal surface, favoring at the same time the corrosion of refractories. Moreover, it was found that the presence of Na in fluoride salts increases significantly the aggressiveness of the aluminum alloy towards the refractory samples.

Jan 1, 2004

Recently, renewed interest in the recovery of uranium from leach solutions has necessitated a re-examination of the hydrometallurgy methods used for uranium in the 1960?s to 1970?s. A synthesizing overview of the lessons learned in those decades together with examination of recent developments in this area is warranted. This paper considers uranium recovery chemistry from acid and alkali leach solutions using solvent extraction and resin ion exchange, and provides information on circuit selection and configuration, equipment selection and design, as well as operational considerations. The unique thermodynamics of uranium solvent extraction are also presented and discussed.

Aug 1, 2010

By J. Koike

Mg alloys for structural application have attracted much attention. However, high process cost and poor mechanical reliability are major concerns upon expanding the application to a wider area. In order to break through these barriers, better ductility is desired at lower temperature. Plastic anisotropy and peculiar twin formation appear to play key roles in the deformation and fracture mechanisms of Mg alloys. In the paper, dislocation slip and twin formation are reviewed. The effects of crystallographic texture and grain size are discussed. The results suggest that a good control of microstructure and texture can improve ductility and mechanical reliability of Mg alloys.

Jan 1, 2006

By R. J. Bowell

Mineralogical controls exert significant control over the extraction of uranium from its ores. Uranium speciation, associated mineralogy, deportment and uranium mineral availability are all factors of consideration when assessing leachibility. This study presents data from laboratory uranium extractions undertaken on several contrasting uranium ores from a wide range of orebodies. The results provide insight into the mineralogical factors of importance when considering uranium extraction. These results are presented within the wider context of geometallurgy and demonstrate how geometallurgical assessment, even at an early stage of mine development, can greatly assist in the design of a suitable extraction scheme.

Aug 1, 2010

By J. O. G. Posada

Magnesium derived foams were prepared by using the so-called baking of powder blended precursor material method. This method comprises mixing magnesium powder with a small fraction of blowing agent (ZrH2, Cs2CO3 and CaH2) and Ni like catalyst, compacting this mix and creating a foam by heat treatment above the magnesium melting temperature. The resulting samples were characterised by microscopy, gas adsorption (BET method) and by small angle neutron scattering. Several mathematical models were used in order to determine particle size distribution, fractal dimension and total pore volume fractions.

Jan 1, 2005

By M. Bertrand

Oxalic precipitation is usually applied to process radioactive wastes or to recover actinides from a multicomponent solution. Precipitation reactions being highly sensitive to many operation parameters, the computer simulation appears to be a very effective tool to forecast the evolutions of the system subjected to various operating conditions. This study focuses on the tetravalent uranium oxalate precipitation modelling which combines population balance and hydrodynamics. Both experimental and numerical studies are carried out in order to analyse the reactor design influence on the precipitate characteristics. The simulations taking into account primary nucleation and crystal growth are in agreement with experiments.

Aug 1, 2010

By Linruo Zhao, Qi Yang, Akihiro Sato

TiN coating has a wide range of tribological applications from wear reduction of cutting tools to erosion protection of gas turbine engine compressor components. The performance of TiN coating depends on its microstructure, mechanical properties and adhesion strength which are influenced by the coating deposition process. In this study the effects of cathodic arc deposition conditions on the microstructure, hardness, adhesion and erosion resistance of TiN coating were investigated experimentally. It was found that varying deposition temperature, substrate bias and N2 pressure could derive a processing window in which TiN coating with superior erosion performance can be fabricated.

Jan 1, 2010

By Yoshitaka Mitsuda, Masao Miyake, Masafumi Maeda

A leaching treatment was investigated to recover metals including rare earths from the mixtures of hydrogen storage alloys and nickel hydroxide. A potential-pH diagram of the La-Ni-H20 system including the domain of stability of LaNi5 was drawn to find appropriate leaching conditions. Alkaline solutions containing ligands that form complexes with nickel ions were supposed to be available to separate hydrogen storage alloys from the mixture. When the mixture was leached with ammoniacal alkaline aqueous solutions, the nickel hydroxide was dissolved and the hydrogen storage alloy was recovered as its original alloy.

Jan 1, 2004

By X. B. Wang, Z. Q. Guo

Slagging coal gasification process became a highlight of coal chemical industry in China during the last decade. Refractory lining's life of slagging gasifiers is one of the most critical factors for a cost-effective operation. The paper introduces current status of coal gasification in China, lining structure of slagging gasifiers and performance of refractory lining. It also summarizes the major factors impacting on refractory wear in slagging coal gasifiers in four Chinese chemical plants, based on ten years of industrial experience. The utilizability is discussed in terms of cost-effectiveness of high chromia refractories and possibility of the alternatives.

Jan 1, 2004

By P. W. Waggitt

ABSTRACT From approximately 1986 until 2000, uranium production was at a historic low. In 2003, uranium mineral exploration surged, despite the global financial crisis; however, the shortage and aging of qualified and experienced operators and regulators might soon become a constraint to this upsurge. This is true for all types of engineers, geologists, other scientists, tradespeople, and technicians. The situation raises questions about how the global mining industry in general and the uranium sector in particular will cope with future staffing needs. In this paper, the author examines the current situation and describes how some organizations are seeking possible solutions.

Jan 1, 2014

By A. Innus, R. Pelletier, C. Allaire

Refractory used for molten aluminium confinement is typically assessed separately for thermo-physical properties and molten aluminium resistance. This present work provides a case study comparison of four commercial refractory products that were subjected to a test procedure that combines mechanical impact, thermal shock with molten aluminium contact. The main conclusion of this work is that physical and mechanical property values by themselves do not, and cannot, predict the response of refractory to potential interactions between molten aluminium contact and thermal shock and mechanical impact. Adequate physical simulation is imperative to quantify the effect of such interactions.

Jan 1, 2004

By D. L. Chen, Q. Zhang

The effect of particle sizes on the low cycle fatigue (LCF) life of discontinuously reinforced metal matrix composites (DR-MMCs) has been widely studied. However, how the particle size affects the LCF life of DR-MMCs quantitatively is still lacking. The aim of this investigation is, therefore, to present an analytical model linking the LCF life to the particle size. This model, based on the enhanced dislocation density in the matrix and the load bearing effect of particles, showed that a decreasing particle size results in a longer LCF life, and the results predicted are in good agreement with the experimental data.

Jan 1, 2004

World copper electrowinning tankhouse plant practices have been surveyed. This survey is a supplement to previous surveys that have been carried out in 1995, 1999, 2001, 2002 and 2003. On a world basis, process technology trends include the further installation of automated electrode handling systems including permanent cathode systems, automated cathode handling machines, fully automatic cranes and polymer concrete cells. Designs also have included larger electrode sizes and higher electrolyte flows and current densities. Overall these trends have further resulted in optimized tank house productivities and improved electrowon cathode purity. Most greenfield copper electrowinning projects are occurring in South America and Central Africa.

Jan 1, 2007

By M. Fainerman-Melnikova

The use of strong base ion exchange resins for the extraction of uranium was pioneered in the 1950?s. Ion exchange technology is applicable to dilute leach solutions such as those obtained from in-situ, heap leaching or in-plant processing of low grade ores. A further advantage of ion exchange processes is that fluidised bed technology allows for treatment of solutions with a relatively high concentration of suspended solids and resin-in-pulp technology can treat leach slurries. However, the extraction of uranium with strong base resins is severely affected by the presence of chloride ions in solution. In areas where high quality water is not readily available, the use of saline water as process water would extend the potential application for ion exchange in uranium processing. Our research program has studied the effectiveness of a wide range of commercially available ion exchangers in uranium extraction from saline solutions. In the present work, we examine the impact of salinity (ranging from chloride concentrations found in groundwater to those present in sea water), on the uranium extraction with weak base anionic resins (WBA). The effect of pH and the presence of the competing impurities are also discussed.

Aug 1, 2010

By K. Karan

Oxygen reduction reaction in PEM fuel cell cathodes involves participation of three reactants - oxygen, hydrogen ions, and electrons. Electrochemical reaction in the catalyst layer is, therefore, influenced by how these species are transported to the reaction site. The two-phase boundary locations at which percolating networks of ionically conducting electrolyte and electronically conducting Pt/C meet are feasible reaction sites. The electrolyte phase also provides pathway for the transport of dissolved oxygen. Most of the 3-D models describe the catalyst layer as an ultra-thin layer, thereby, losing useful information on the distribution of electrochemical reaction rate. In this paper, we extend our previous work on 2-D cross-the-channel modeling of PEMFC cathode based on agglomerate catalyst layer. In particular, we take a closer look at the influence of proton conductivity on the reaction rate distribution in the catalyst layer. As well, we re-examine the role of anisotropic transport coefficient of the porous transport layer (PTL), commonly known as the gas diffusion layer, on the current density distribution under the channel and the rib of the flow-field plates. Results from both a 2¬D and a 3-D models will be presented.

Jan 1, 2005

By M. D. Viera

The purpose of the study is to show, through real cases of companies in Chile, the different problems concerning valuing or economically appraising a mining ore resource with the traditional techniques. The study demonstrates that, with the risk analysis and real options theory application, one could determine the most probable value for a mining resource or mining business, and the risks cover of uncertainty scenarios. The study discusses different methods and criteria employed in the ore resource evaluation or mining assets. It also shows a comparative analysis of the different methods in order to explain various distortions, errors, risks and imprecisions of each of them. the companies are becoming aware of the risks' importance and the impact they have on the commercial value and resource estimation models. Now, the real options are the techniques that somehow make it possible to value and control the risk cover of the business. The company valuation could help respond questions like: ? How much is my business worth? ? How much has the investment profitability of my business been? What could be done to improve this profitability and create value?

Jan 1, 2007

The NorthMet deposit of PolyMet Mining is located in northern Minnesota, adjacent to the Iron Range. The deposit is polymetallic with values of Cu, Ni, Co, Zn, Pt, Pd and Au. The processing route selected for extraction of these values utilizes bulk sulfide flotation followed by hydrometallurgical treatment. The hydrometallurgical process has been thoroughly tested on the bench and pilot plant scale at SGS Lakefield Research. The major steps in the process are; ? Chloride-assisted total pressure oxidation for extraction of base and precious metals ?Thickening/filtration/washing of the barren residue from total oxidation ? Reduction and precipitation of Au, Pt, Pd from the oxidation solution ? Partial neutralization of autoclave acid using limestone ? Copper SXlEW for production of copper cathode ? Treatment of a portion of the raffinate from Cu SX to recover NilCo/Zn as either a mixed Ni-Co-Zn hydroxide or as separate Ni hydroxide, Co hydroxide and a Zn sulfate solution. ? Recycling of the remaining raffinate to the autoclave as coolant The process flowsheet, chemistry and bench/pilot plant test results will be reported in this paper.

Jan 1, 2007

By N. Maleki

Magnesium matrix composites are widely used in automotive and aerospace industries for achieving higher performance due to their light weight. The Mg2Si intermetallics compound in Mg/Mg2Si composite exhibits many excellent properties such as high melting temperature, high hardness, and low thermal expansion coefficient. However, under normal cast conditions, the primary Mg2Si phase exhibits coarse Chinese script or dendritic morphologies and the eutectic structures is very brittle resulting in the low ductility and strength of the alloys. Modification treatment is a very effective method to obtain fine microstructure and improve the mechanical properties of the alloys due to low production cost. In this investigation various amount of bismuth addition have been carried out on Mg?5wt %Si alloy to refine and modify the morphology of coarse Mg2Si in order to improve the corrosion resistance of the composite product. The effect of Bi content on microstructure of Mg2Si/Mg composite was investigated by optical and scanning electron microscopy followed by EDX analysis and X-Ray diffraction. In order to compare corrosion resistance of unmodified and modified specimens, Immersion test and potentiodynamic polarization (PD) were used. The results showed that by Bi addition, the size of primary phase Mg2Si was considerably reduced and the morphology was modified from a coarse dendritic shape to a polyhedral shape. The results also indicated that the corrosion resistance of Mg?Si alloys was improved by the addition of 1%wt of Bi due to the reduction, refinement and evenly distribution of Mg2Si phase. Indeed, both the morphology and distribution of Mg2Si intermetallic had a great influence on the corrosion behavior of Mg/Mg2Si composite.

Oct 1, 2011