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By C. Edwards

ABSTRACT: Milling operations in northern Saskatchewan’s Athabasca Basin have produced uranium continuously since 1975. During that period, the Athabasca Basin has been one of the world’s premier uranium camps, yielding more than 660 million lb (299,370,964 kg) of U3O8. In this paper, the author describes former and current milling operations and discusses why and how the milling process has changed and developed over the past 35 years. The author’s considerations for the future of uranium extraction in the Athabasca Basin conclude the paper.

Jan 1, 2012

By W. Burger

In underground mines worldwide, a large number of short and small diameter slot holes need to be excavated. Herrenknecht has developed and built a new boxholeboring machine based on the well-proven Microtunnellingpipe jacking technology. The innovative Boxhole Boring Machine significantly increases work safety and requires only minimal drift dimensions. The high and consistent production rates that can be achieved result in enormous time savings compared to conventional drill and blast excavations. GENERAL ASPECTS In gold, copper and ore mines ventilation shafts are required to prepare block caving operations, to discharge ore onto the transportation level and to provide evacuation shafts. A high level of occupational safety and efficiency is the main objective when drilling vertical or inclined shafts. The faster and more safely shafts can be constructed, the earlier the actual production in the mine can start or be continued. Mechanized or conventional methods (drill&blast) that have been used to date only partially meet the required safety standards and fail to provide the requested production rates.

Jan 1, 2012

By C. Montoya

This paper shows, through a case study, the impact of multivariate grade modelling upon mine design and mine planning. A deposit explored by drill holes is considered, in which the grades of five elements (copper, silver, molybdenum, arsenic, and antimony) are of interest. Forty alternative models of the deposit are constructed by fitting the joint correlation structure of the grade variables and using conditional cosimulation. In addition, a reference model, obtained by averaging the alternative models, is also considered. The study shows that the resulting mine design (final pit characteristics and production schedules) is sensitive to the grade model under consideration, and that the design based on the reference model may not be optimal when compared to the alternative models based on cosimulation. However, when assuming a given long-term plan and extraction sequence, the grades and net present value (NPV) calculated on the reference model are unbiased with respect to those calculated on the alternative models with the same extraction sequence. The latter allow assessing the possible dispersion of the actual grades and NPV around their expected values, and are useful for the planner in order to determine the probability of meeting given production targets and of exceeding or falling short of given threshold grades. Additionally, unlike cosimulation, the separate simulation of each grade variable leads to unrealistic resource models and to biased results in mine design and mine planning. This approach should therefore be avoided, unless the grade variables are spatially uncorrelated.

Jan 1, 2012

By Alain Duchesne, Dominique Fonfrede, Alan Broca

The technique involves the removal, in one piece, of an unwanted concrete pile section, exploiting the principle of crack propagation induced using gas pressure. The device, or pod, is made of a container in which an over-pressure is generated. After a predetermined time delay of 72 hours, gas and pressure are produced by the reaction between a calcium base chemical and water.

Jan 1, 2012

By Andrew Hall

Many Latin American countries are facing a scarcity of water. As such, infrastructure decisions are quite different from those made in parts of the world that experience a positive water balance. In the latter case, the water treatment approach tends to be ?treat and discharge.? For Latin American regions facing the challenges that go with a negative water balance, the focus is on resource optimization and reuse. Historically, the water challenge has had a significant impact on economic development in Latin America, especially in sectors such as mining, where water usage is high. At the same time, countries such as Chile and Brazil are major development targets for mining and oil and gas operations. Given the water supply challenge, industry is increasingly turning to technologies and processes that maximize water recovery and reuse. With sulfide precipitation and ion exchange water treatment processes for example, it is possible to treat and recover more than 99 percent of water for reuse onsite. These technologies have been applied successfully in other regions of the world where water conservation practices are essential to economic survival.

Jan 1, 2012

By Muamer Medusalic, Kim Henley, Lucas Bottomley

The period from 2009 to 2012 has witnessed a large rise in the number of blast-generated fume events in Eastern Australia, where highly visible oxides of nitrogen (NOx) are produced from coal mine blasting. Fume production mechanisms have been poorly understood by mine operators, and practical measures to reduce fume were initially elusive. Over time, data on fume events has been collected and analysis has pointed to a range of contributing factors associated with fume production.

Jan 1, 2012

By Arnaud Faucher, Amar Sabih, Sudarshan Martins, Tristan Martin, Sami Makni, Peter Radziszewski, Poorya Hosseini, Francois-Raymond Boyer

The measurement of acoustic signals produced by a tumbling mill has been previously used to determine the operating state of the mill and correlate the variations of the sound intensity with the operating conditions of the mill. Separately, the discrete element model (DEM), a software simulation of the mill, was developed to provide insight into the operation of the mill. Presently, there has not been much work reconciling the DEM simulation of the mill with the acoustic signal. Working from basic principles of linear, time-invariant systems, agreement between an acoustic DEM simulation and the measured signal is sought. First, the impulse response function of the mill is measured. The DEM provides the forces applied to the mill shell as a function of time. A convolution of these simulated shell forces and the transfer function gives the simulated acoustic signal. This signal is compared to the measured acoustic signal, both in the time domain and the frequency domain. Finally, a discussion of the results is given.

Jan 1, 2012

By M. Z. A. Bakar

To investigate the differences in the radial drag pick cutting performance in dry and saturated sandstone, a suite of linear rock cutting test was performed using linear rock cutting machine (LRCM). Experimental results of 50 data passes, incorporating 350 data cuts were used to compute cutting, normal and side forces required for determination of other performance related parameters. Although the forces required to cut the dry and saturated rock were in congruence for most of the spacing and depths of cut combinations; but the overall averaged cutting and normal forces for saturated rock cutting were found to be 9.9% and 9.4% respectively higher than the dry rock cutting. The increase in the overall averaged forces was attributed to strength variability of one of the saturated block affecting the overall forces. The side forces experienced a negligible drop in saturated rock cutting. An increase of 28% and 9% in the actual and nominal specific energy values respectively was also recorded when cutting saturated rock as compared to the dry rock cutting. The increase in saturated rock specific energy is attributed to production of large amount of fines and few large sized chips directly contributing towards increase in specific energy. The optimum s/d ratio for dry rock tests was found to lie between 6 and 8 whereas for saturated rock cuts this value lied between 5 and 9.

Jan 1, 2012

In 2011, the value of mineral production increased in the United States for the second consecutive year (Table 1). Production increased modestly for most mineral commodities mined in the United States, and price increases, especially for precious metals, resulted in increases in the value of production. Minerals remained fundamental to the U.S. economy, contributing to the real gross domestic product (GDP) at several levels, including mining, processing and manufacturing finished products. Minerals? contribution to the GDP increased for the second consecutive year. Trends in other sectors of the domestic economy were similar to those in mineral production and consumption rates. U.S. apparent mineral consumption (industrial) of 11 mineral commodities decreased substantially from 2005 to 2010 (aluminum, cadmium, cement, copper, iron, lead, salt, soda ash, steel, tin and zinc). Data for 2011 were not calculated, but the data show a sustained decrease (especially for the metals) preceding the recession through 2010, so consumption seems to be behaving differently than production and GDP. After continued decline following the 2008?2009 recession, the construction industry began to show signs of improvement during 2011, with increased production and consumption of cement, construction sand and gravel, and gypsum ? mineral commodities that are used almost exclusively in construction. Crushed stone production, however, continued to decline.

Jan 1, 2012

By A. Alfantazi, E. Asselin

"The corrosion of commercially pure titanium (CP-Ti) was studied from room temperature up to medium temperature (~160°C) under conditions relevant to medium temperature chalcopyrite leaching processes. The corrosion rates were measured by immersion and electrochemical tests in sulfuric acid. The influences of chloride, cupric and ferric ions on the corrosion rate and behavior were also investigated. Corrosion of the CP-Ti did not account for the total current density measured by linear polarization tests. The corrosion rates of CP-Ti under medium temperature leaching conditions were surprisingly high. The corrosion rate measured in ferric containing solution at 160°C was approximately 20 mm/yr.INTRODUCTIONTitanium exhibits excellent corrosion resistance in many aggressive environments because of the formation of a very chemically stable, highly adherent, and protective oxide film on its surface (Mitsuo et al., 2002). Because titanium is the only metal available at a reasonable cost that resists the high temperature corrosive slurries in many leaching processes, it is often chosen as autoclave liner material where it is subjected to severe conditions of acidity, temperature and pressure (Grauman and Say, 2000).A number of distinctly different hydrometallurgical processes for the pressure leaching of chalcopyrite have been developed and patented by various companies and they can be classified into low, medium and high temperature regimes (McDonald and Muir, 2007). For example, chalcopyrite concentrate may be processed at medium temperatures (115-175°C) and pressures of 800-2200 kPa (Dreisinger, D., 2006; Sahu and Asselin, 2011). The lixiviant may contain 20 to 55 g/L sulfuric acid, 8 to 12 g/L chloride ions, 10-25 g/L Cu2+ (Jones, 1995, 1997, 1999), and less than 1 g/L Fe3+ (Defreyne et al., 2005). The amount of these additions is determined by the grade of the ores and details are shown in Table 1."

Jan 1, 2012

By Chenhui Liu, Hong-ying Xia, Bingguo Liu, Wei Li, Jinhui Peng, Libo Zhang

"Dielectric property is an important limiting factor in the development of microwave processing of minerals and ores. In this study, we used an open-ended coaxial sensor method to measure the complex permittivity of an ilmenite concentrate (41%TiC>2) and microwave absorption properties from room temperature to 100°C. The results show that the dielectric constant, loss factor and loss tangent increase with temperature rising at 2.45GHz. Microwave absorption properties of this ore are highly dependent on temperature and frequency. Ilmenite concentrate can be used as raw materials to prepare wideband microwave absorbing material. The research will be helpful in explaining the thermal running of microwave dielectric heating the ilmenite concentrate.IntroductionAs the sources of high-grade titanic mineral are decreasing worldwide, the utilization of low-grade minerals such as ilmenite has attracted more attention [1,2]. Because Panzhihua ilmenite has complex minerals and high contents of MgO, CaO, S1O2 , it is difficult to upgrade the ilmenite to titanium-rich slag and farther produce synthetic rutile and titanium dioxide pigment [3]. Therefore, it is desirable to develop new technology for processing ilmenite ore [4]."

Jan 1, 2012

Tracer gases are an effective method for assessment of mine ventilation systems, but their dispersion characteristics can differ substantially as ventilation parameters, such as flow path and velocity, vary. This research utilizes Computational Fluid Dynamics (CFD) to model a simplified full scale model mine, details a sensitivity study examining mesh size for an underground coal mine simulation, and examines gas dispersion parameters to determine the optimal model methods for simulation of tracer gases in underground coal mines. These models can be used to determine how a given tracer gas profile might be generated in a mine or areas of a mine that are not accessible, for example, immediately following a mine disaster. Accurate simulation scenarios can allow for the remote determination of the status of the ventilation network, but the sensitivity of the simulation at mine scale must be carefully examined.

Jan 1, 2012

By Brian Putland, Fred Kock, Leigh Siddall

Single stage semi-autogenous / autogenous (S/AG) milling has become a common design for a variety of ore types with the advantages of being comparatively low capital cost and flexible for future expansion. The single stage SAG/AG milling option is ideal for starter projects with significant exploration and expansion potential. Currently a number of the largest SAG mills designed are installed in single stage configuration. This paper discusses the challenges associated with the process design of single stage SAG/AG milling circuits, the design flexibility required to ensure a robust circuit and the operating techniques adopted at successful installations.

Jan 1, 2012

By S. Özgen

In this study, the possibility of beneficiation of chromite tailings in the Uckopru/Fethiye-Turkey region by a combination of hydrocyclone and multigravity separator (MGS) was investigated. The two significant operational parameters of hydrocyclone, which were diameter of the apex and diameter of the vortex, and the three significant operational parameters of the MGS, which were drum speed, tilt angle, and wash water, were varied and the results were evaluated with the central composite rotatable design. In order to produce a chromite concentrate by hydrocyclone and MGS, mathematical model equations were derived by computer simulation programming, applying the least-squares method using Minitab 15. Second-order response functions were produced for the grade and recovery of chromite concentrates.

Jan 1, 2012

By Núbia Suely Silva Santos, Alexandre da Silva Crespo, Frederico Muylaert Margem, Sergio Neves Monteiro, Anderson de Paula Barbosa, Michel Picanço Oliveira

"Environmental considerations in addition to technical, economical and societal benefits are increasingly promoting the substitution of natural fibers for glass fiber in polymer matrix composites. However, natural fibers are heterogeneous in their dimensions, specially the cross section, which plays an important role in their mechanical strength. The fibers extracted from the petiole of the buriti palm tree is a relatively unknown but promising natural fiber for composite reinforcement. In this work, a statistical analysis of the density of buriti petiole fibers using the Weibull methodology was performed. An attempt to correlate the fiber density with the diameter, precisely measured by means of a profile projector, was carried out. The results revealed an inverse dependence between the buriti petiole fiber diameter and corresponding density. Fracture tip observation by SEM suggested a possible mechanism that could justify this inverse correlation.INTRODUTIONIn the past decade polymer composites reinforced with natural fibers obtained from cellulose-based plants, known as lignocellulosic fibers, have been applied in several engineering sectors, specially the automobile industry as both interior and outside component [1-4].Environmental benefits as well as economical, social, and technical advantages are actually promoting the substitution of these lignocellulosic for the traditional glass fiber in polymer matrix composites [5]. Today several lignocellulosic fiber are being extensively investigated [6-11] and considered for reinforcement of polymer composites. Some relatively unknown lignocellulosic fiber with reinforcement potential, however, still need to be characterized aiming at future application in composites. This is the case of the fibers stripped of from the petiole of the buriti palm tree, which is endemic in the central and northern regions of South America [12,13]. Preliminary works on the possibility of using the buriti petiole fibers as composite reinforcement, has shown favorable results [14,15]."

Jan 1, 2012

By R. J. Visintainer, W. L. Whitlock

"Difficulties with the sizing and operation of centrifugal froth pumps are common and the underlying fluid dynamics are complex. Design and selection often relies on previous experience, offering unreliable guidance for novel applications or unexpected problems. The current paper describes a program of extensive laboratory testing on froth handling centrifugal pumps, covering a range of flows, heads, speeds, viscosity, air content and froth stability. Variations in impeller vane design and the effectiveness of an airlock venting apparatus were also examined. The program resulted in a better understanding of centrifugal froth pump dynamics and insight for the troubleshooting of field applications.INTRODUCTION The Challenge of Pumping Froth In pumping mineral processing froth, the handling of large quantities of air within the fluid is often unavoidable. Efforts to reduce the amount of air present at the pump suction, while always recommended for improving pump performance, may have limitations. Some strategies may also carry an economic penalty, such as unwanted process dilution (e.g. due to water spray or injection), or increased capital cost of equipment due to oversized pumps, sumps and/or piping. Froth pumping losses fall into several categories, as described below and represented graphically in Figure 1. • Density effects: Entrained air reduces the pressure created by the centrifugal pump in direct proportion to the reduction in bulk density. This is not a true “loss”, since the head produced by the pump (in meters of froth), may remain unaffected. However, the reduction in pressure often leads to a corresponding increase in pump speed required to drive the system, which itself leads to increased NPSH required by the pump (NPSHR). Furthermore, by adding a gas phase, the overall volumetric flowrate is increased, assuming a fixed quantity of de-aerated liquid being handled. This leads to increased suction velocity which further reduces the NPSH margin by simultaneously increasing pump NPSHR and decreasing system NPSH available at the pump suction (NPSHA). • Viscosity effects: Increased viscosity introduces an additional factor in some froth pumping applications, such as oil sands bitumen froth. Losses result from increased shear stress within the fluid flow, which increase with flowrate. Viscosity also facilitates the formation of airlock by reducing turbulence and allowing individual bubbles to coalesce more easily within the flow stream. Finally, it increases pump NPSHR by increasing local pressure drop in the vicinity of the vane inlet edges. • Airlock effects: Also known as air binding, it occurs when air or gas coalesces within the pump suction or impeller passages and begins to collect there, held by buoyancy forces within the rotating flow field. In essence, the liquid “floats upwards” towards the pump suction against the outward directed centrifugal forces. The airlock acts as a blockage, with corresponding reductions in flow, head and efficiency. NPSHR also increases, due to increased velocity and distorted streamlines in the flow circumventing the blockage."

Jan 1, 2012

By Nickolas Vlahopoulos, Nicholas Stowe

A concept has been proposed for the focusing of underwater energy. An array of spherical TNT charges is used to achieve this aim. The goal of the present research effort is to model such a system and identify optional arrangement and detonation timing schemes. A fast-running model is necessary to perform optimization analysis due to the highly iterative nature of most optimization algorithms. This requirement renders the use of sophisticated numerical solvers impractical. An analytical, physics-based model must be developed to satisfy the demands of the multiple charge optimization problem. This model must capture shock propagation speed, pressure-time histories throughout the fluid domain, and multiple charge interaction phenomena. Such a model is presented herein.

Jan 1, 2012

By Sudarshan Martins

The measurement of acoustic signals produced by a tumbling mill has been previously used to determine the operating state of the mill and correlate the variations of the sound intensity with the operating conditions of the mill. Separately, the discrete element model (DEM), a software simulation of the mill, was developed to provide insight into the operation of the mill. Presently, there has not been much work reconciling the DEM simulation of the mill with the acoustic signal. Working from basic principles of linear, time-invariant systems, agreement between an acoustic DEM simulation and the measured signal is sought. First, the impulse response function of the mill is measured. The DEM provides the forces applied to the mill shell as a function of time. A convolution of these simulated shell forces and the transfer function gives the simulated acoustic signal. This signal is compared to the measured acoustic signal, both in the time domain and the frequency domain. Finally, a discussion of the results is given.

Jan 1, 2012

By D. Nutakor

This paper presents the results of a study conducted on a slope failure that occurred in the Q7 mining cut at Rio Tinto's Bingham Canyon Mine. The slope failure occurred in a weak rock mass with an estimated rock mass rating of 25%. The failure mechanism was of the circular type, involving ten 15-m (50-ft) benches and covered a total width of 152 m (500 ft). The analysis used Adam Technology's photogrammetric method with a two-dimensional rock fall simulation program (RocFall software) to design a 3-m- (1 0-ft-) high berm located 7 m (24 ft) from the toe of the failed mass. Back and predictive analyses were performed on a cross-section through the slide using Slope/W software, resulting in flattening the interramp angle (IRA) from 44° to 38°. This design modification produced a factor of safety (FOS) of 1.14. Sensitivity analysis involving FOS vs. pore water pressure showed that FOS is sensitive to water saturation. A dewatering system using a series of horizontal holes drilled below the slide and dewatering holes drilled from a drainage gallery has since been established to improve the stability of the slope. Throughout the one-year period since this investigation, no significant slope movement has been detected by the slope stability radar, and mining is in progress below the failure.

Jan 1, 2012

By H. S. Price

This report discusses the development of a mathematical model that describes the flow of methane only and methane and water in a coal bed during mining operations. Because of the complex geometry, boundary conditions and fluid properties, the model is based on a numerical solution to the equations describing flow. The goals for the development of this model and requirements to which it complies are for the most part expressly stated in Request for Proposal No. 50110752. In addition to the capabilities specified under the scope of work the model can handle an anisotropic porous medium and a source term has been added which will simulate, somewhat, the effects of desorption. This term will be pressure dependent. The effect of time on such a term is only taken care of in the change of pressure with time. This source term will have the dimensions of Mcf/day/Mcf pore volume. It will be a part of the input data to be supplied by the user and will be entered as a table of rates versus pressure. These models consider the fracture system as the main porosity. All computed results pertain to the fractures. The source term mentioned above represents the flow from the matrix porosity into the fracture. Such flow should be small compared with the flow between fractures since these models handle only one porosity structure system.

Jan 1, 2012