Search Documents

By Jorge Amaya

A critical aspect of long-term open-pit mine planning consists in computing a production schedule based upon a block sequencing strategy. Such a schedule should specify when and if blocks should be extracted in such a way as to maximize NPV, while satisfying wall-slope and production capacity constraints. It is well known that this problem can be modeled with integer programming (IP). However, integer programming is not used in practice because the size of typical block models makes such problems intractable to standard IP solvers. In this article we describe a scalable IP-based methodology for solving very large (millions of blocks) instances of this problem. We show that embedding standard IP technologies in a local-search based algorithm we are able to obtain near-optimal solutions to large problems in reasonable time. This methodology has been tested in several mine wide block models.

Oct 1, 2009

By Jorge Amaya

A critical aspect of long-term open-pit mine planning consists in computing a production schedule based upon a block sequencing strategy. Such a schedule should specify when and if blocks should be extracted in such a way as to maximize NPV, while satisfying wall-slope and production capacity constraints. It is well known that this problem can be modeled with integer programming (IP). However, integer programming is not used in practice because the size of typical block models makes such problems intractable to standard IP solvers. In this article we describe a scalable IP-based methodology for solving very large (millions of blocks) instances of this problem. We show that embedding standard IP technologies in a local-search based algorithm we are able to obtain near-optimal solutions to large problems in reasonable time. This methodology has been tested in several mine wide block models.

Oct 1, 2009

By James R. Yeager, Eric L. Hoffman, John R. Clark

"Abstract -This paper describes fire assaying and ‘high tech’ alternatives for gold analysis, including advantages and disadvantages of each method. These ‘high tech’ methods include INAA (instrumental neutron activation), aqua regia digestion/AA (atomic absorption), GFAA (graphite furnaceatomic absorption) or ICP/MS (inductively coupled plasma emission mass spectrometry) and a combination of cyanidation with AA, GFAA or ICP/MS methods.Fire assay remains the stalwart among analytical methods for gold but, even with its multiple analytical finishes, is not fool-proof for recovering 100% of the gold present. Consumers of assays should not blindly trust the assay results without consideration of quality control data. Laboratories can and do make mistakes. Some of these can be easily discovered if you do your own due diligence. All these measures should ensure that gold analysis values from successive campaigns and from different laboratories meet acceptable levels of accuracy and precision, and can be correlated together, particularly when they occur in neighboring holes. This is essential just as much for prospect evaluation as for project feasibility."

Jan 1, 1998

By K. G. Eriksson

"The first tentative test made to try rubber lining in grinding mills was made in the early twenties. However, because of poor rubber compounds and design the results did not prove to be promising.In the early sixties successful trials of rubber linings were carried out as a result of a cooperation between boliden AB and Skega AB.One of the reasons rubber was not used earlier for linings was the difference in wear characteristics between rubber and steel. The ability to successfully develop rubber mill liners depends on three factors:l. Design2. Material (rubber compounding)3. Experience (knowledge)DESIGNThe main difference between steel and rubber, in material aspect, is the elasticity and the low tensile and shearing strength of rubber. It is necessary to take maximum advantage of the elasticity and to reduce tensile and shearing forces by minimizing the sliding of the mill charge. This is accomplished by using the Lorrain type of liners, i.e., lifter bars and plates. It is, however, necessary to keep a certain balance between lifter bars to optimize liner life and grinding performance."

Jan 1, 1983

By Lorna Ortiz-Soto

A series of titiania- and silica-supported Au, Pt and Pt-Au catalysts prepared through different synthetic routes have been investigated in terms of their structural properties, adsorption of CO, and catalytic activity for the selective catalytic reduction of NO by propylene and the oxidation of and CO. Catalysts prepared by incipient wetness impregnation from individual Pt and Au precursors, exhibited characteristics very similar to those of monometallic Pt catalysts. This behavior is consistent with a model in which the two metals remain segregated due to their miscibility gap, and only Pt participates in the adsorption of CO and the reactions under consideration. In contrast, catalysts prepared from a Pt2Au4(C=CtBu)8 organo-bimetallic cluster precursor exhibited different behavior both in terms of CO adsorption and their catalytic activity for the three reactions examined. The combination of the kinetic, spectroscopic and structural characterization data suggests that in this case Pt and Au remain intimately mixed in the form of Pt-Au bimetallic particles, and that the presence of Au modifies the behavior of Pt.

Oct 1, 2003

By Ross Dimmock

The productivity of a mine has the same goals as the quest to complete a tunnel project both safely and within time. A key aspect to achieving this goal is to excavate and support the working face as quickly as possible, allowing early re-entry to start construction of the next advance in safety. As with tunnels, the use of high performance wet-mix sprayed concrete has increased in mines dramatically over the last few years, and year on year has seen a stepwise increase in shotcrete performance, particularly in the first few hours. Shotcrete early age strength development clearly offers mining teams enormous advantages by allowing early, safe re-entry to the face. This paper illustrates that in the hard rock tunnelling field, modern shotcrete approaches do not cause delays in re-entry, but allow a continuous construction cycle. Furthermore, the paper identifies the most suitable, up-to-date shotcrete admixture and equipment technology available to the mining community to permit early re-entry.

May 1, 2003

By Y. T. John Kwong

Abstract - To exploit an ore deposit without unduly impacting the environment is a challenge that can only be met by the concerted efforts of traditionally independent teams working on a mining project. Not only is detailed geology required of geologists to help mine engineers to develop a mine plan that assures generation of the least possible amount of mine waste, but metallurgists also have to select the most environmentally friendly mineral processing schemes, and communicate with environmental engineers with regard to complications that process chemicals may pose on proper mine waste management. Traditional ore deposit models typically emphasize the geological and mineralogical aspects of ore genesis to facilitate exploration for similar deposits. Recent research has shown that potential environmental liabilities such as acid mine drainage and metal leaching can readily be predicted according to deposit types. The choice of mining methods, mineral processing schemes, and decommissioning options are also largely dictated by the composition and setting of an orebody to be mined. Integrating such related information into traditional ore deposit descriptions would lead to the development of comprehensive environmental ore deposit models. The latter would facilitate communication among staff of the varied components of a mine project and aid with the selection of a combination of methods and strategies that would assure minimum environmental risks and impacts, reduce the overall project cost, and enhance sustainable development.

Jan 1, 2003

By Y. Konishi

This paper reviews the mechanism and kinetics of bioleaching of chalcopyrite by the thermophilic archae Acidianus brierleyi in batch and continuous-flow reactors. Rate data for the batch bioleaching of chalcopyrite concentrate were collected to clarify mechanism of the chalcopyrite bioleaching with A. brierleyi. The chalcopyrite leaching was markedly accelerated in the presence of A. brierleyi, and greater than 90% copper leaching was achieved within 10 days. Chalcopyrite leaching took place predominantly as a result of direct attack by adsorbed bacteria on the sulfide surface, the chemical leaching with ferric iron being insignificant. Batch rate data collected under a variety of operating variables were analyzed with our batch bioleaching model, in order to estimate microbial kinetic and stoichiometric parameters for the microbial growth on chalcopyrite. The batch model and the estimated parameter values were used to find optimum operating conditions. Moreover, the batch model was extended to describe the bioleaching in continuous-flow stirred tank reactors. Simulations based on the continuous reactor model and the estimated parameter values were used to predict the leaching fraction as a function of the number of reactors connected in series.

Jan 1, 2007

By I. Bakry

Uncertainty is an inherent characteristic of construction projects. Neglecting uncertainties associated with different input parameters in the planning stage could well lead to misleading and/or unachievable project schedules. The objective of this paper is to present a new approach towards scheduling repetitive construction projects while accounting for uncertainty. The paper presents an algorithm that quantifies anticipated delays resulting from different sources of uncertainty in the form of fuzzy time buffers. Through inserting the time buffers in strategic places in a time schedule, the algorithm provides protection against those main anticipated delays. The presented algorithm comprises two integrated components, a scheduling component responsible for producing a basic Linear Scheduling Method (LSM) schedule with deterministic activity durations, and a buffer component that handles fuzzy buffers sizing and insertion. The presented algorithm offers four different buffer insertion techniques covering different cases of interrelations between successive activities. The algorithm is implemented in a spreadsheet application, which automates calculations, yet allows users to fine tune the algorithm to fit the project at hand. With a focuses on highway construction projects as an example of repetitive construction projects, this paper accounts for sources of uncertainty such as weather, site conditions, change orders and equipment related delays. A hypothetical case is studied and explained to further demonstrate how the proposed algorithm works.

Aug 1, 2013

By B. S. Riess

A novel design for an automated uranium pellet stacking system is presented. This system is designed as a drop-in solution to the current production line to enhance the fuel pellet stacking process. The three main goals of this system are to reduce worker exposure to radiation to as low as reasonable achievable (ALARA), improve product quality, and increase productivity. The proposed system will reduce the potential for human error. This single automated system will replace the two existing pellet stacking stations while increasing the total output, eliminating pellet stacking as a bottleneck in the fuel bundle assembly process.

Aug 1, 2010

By H. W. Hughes

"The Wasamac Gold Mines mill, situated 10 miles from Rouyn-Noranda on highway 59, commenced milling April 1st 1965 at a rate of 700 tons per day. This has gradually increased to over 1200 tons per day in December. The mill has done up to 1400 tons on occasion.The ore was formed in the Wasa shear zone by means of replacement. The minerals which replaced the original rocks were carbonates, quartz, pyrite, chlorite, gold and silver. Work index varies from 9. 6 on the chlorite to 11. 6 on the quartz. The gold is very finely disseminated throughout the gangue and while associated with the pyrite is not included in the pyrite. Very seldom is gold found or seen in the free state.Test work showed a medium fine grind of 85 to 90 per cent was necessary to achieve a 95.00 per cent extraction. Straight cyanidation time of 30 to 36 hours was indicated. This has been borne out by subsequent mill performance with a grind around 87 per cent minus 200 mesh and extraction ranging from 95 to 96 per cent.When it was decided to bring the Wasamac property into production, the Bicroft Uranium Mines Ltd. crushing and grinding units together with one pebble mill and the pachuca tanks from Dyno Uranium Mines Ltd. were purchased.Wasamac crusher house and mill buildings are of laminated wood construction, covered with 5/ 8th inch plywood and corrugated iron sheeting."

Jan 1, 1966

The Boleo project is located in Mexico close to the town of Santa Rosalia on the Baja Peninsula. The Boleo deposit contains copper, cobalt, zinc and manganese values as oxides with minor sulfides. The Boleo deposit is metallurgically challenging due to: 1) the requirement to recover four separate metals; 2) the presence of high levels of clay in the deposit resulting in difficult solid-liquid separations, and; 3) the need to use seawater for the bulk of the processing. Baja Mining, Bateman Engineering and SGS Lakefield Research have collaborated to develop and test a process flowsheet to recover copper, cobalt, zinc and manganese products at Boleo. The key steps in the flowsheet are: ? Feed preparation (scrubbing and ball milling of oversize) in copper raffinate ? Ore leaching using oxidative and reductive leaching ? CCD washing using high rate thickening technology ? Copper SXlEW ? Treatment of a bleed solution for cobalt, zinc and manganese recovery The process for cobalt, zinc and manganese recovery involves iron and aluminum removal followed by cobalt/zinc bulk extraction using CSIRO's DSX solvent extraction system and selective zinc and cobalt stripping. The zinc strip solution is evaporated to produce zinc sulfate monohydrate crystals to market and cobalt is recovered via a further SXlEW process as high purity metal. Manganese is precipitated as manganese carbonate from the DSX raffinate solution. This paper will review the Boleo process flowsheet and provide detailed results from the 2006 pilot plant operation conducted at SGS Lakefield in Canada.

Jan 1, 2007

By K. C. Sole

In most copper solvent-extraction operations, an important consideration in choice of extractant is the requirement for high selectivity of copper over iron. Ester-modified aldoxime extractants presently offer the best Cu:Fe selectivity. In some plants, however, the process feed liquors contain significant amounts of manganese but little iron. Although manganese is not chemically extracted by oximes, trace amounts are carried over to the electrowinning circuit by physical entrainment. This may result in anodic oxidation of manganese which, in turn, can cause oxidative degradation of the organic phase when returned to the solvent-extraction circuit in the spent electrolyte. Many of these operations prefer to operate with higher levels of iron reporting to the advance electrolyte, as appropriate control of the Fe(II)/Fe(III) couple will ensure that manganese remains in the benign Mn(II) form. A new reagent, LS 4202, designed by Cytec, now offers the possibility of tailoring the iron co-extraction, so that appropriate Cu:Fe selectivity can be achieved in the solvent-extraction operation to maintain an electrolyte Fe:Mn mass ratio of >10:1, while retaining the other benefits offered by ester-modified aldoximes. The results of an integrated solvent extraction-electrowinning pilot-plant trial are presented, in which the performances of the conventional extractants ACORGA® M.5774 and LIX® 984N are compared with LS 4202. The Cu:Fe selectivity is demonstrated, along with results on the transfer of other impurities to the advance electrolyte.

Jan 1, 2007

By W. Qin

The nucleation of d hydride in Zircaloy-4 has been studied using electron backscatter diffraction. Hydrides prefer to nucleate at intergranular rather than intragranular sites. (0001) a -Zr//(111) d -ZrHx is the most common crystallographic relationship. The hydride platelets are generally interlinked each other and form a chain-like configuration. Based on thermodynamic model, the formation mechanisms of the hydrides at different sites and the interlinked structure were analyzed. We found that the misorientation of two adjacent grains has a crucial effect on hydride nucleation sites, and the tensile stress near the tips of hydride platelets is a key factor affecting the appearance of interlinked structure.

Aug 1, 2010

The original JKMRC AG/SAG mill model was developed over 30 years ago and has been upgraded a number of times since then, with the current published version being the Variable Rates model that is now over 15 years old. Since this model was developed further enhancements have been derived, some of which are applied in-house and some which have yet to be incorporated. The published and the commercially available model in JKSimMet is currently undergoing a comprehensive overhaul with a vastly extended data base for model evolution and validation. Improvements developed within the AMIRA P9 project, in-house development and a number of collaborative projects, are being incorporated into the upgraded model structure. Enhanced capabilities will include: power-based breakage rates scaling; a far wider mill filling range (from 10% to 40%) that exhibits peak in throughput as mill filling increases; higher ball loads; improved pebble discharge function; improved slurry discharge function incorporating important mill design and operational influences; and the new size dependent breakage function. The model will also be able to accommodate some influence of liner design and multi-component ores (blends of hard and soft components). This upgrade is still a work in progress but substantial changes have been made to date. This paper presents some of the new improvements and their influence on the predictive capability of the model.

Jan 1, 2012

By D. Magoon

The metals industry has enjoyed a resurgence in prices and demand for its commodities during the global surge in economic activity that began in 2005. This success has brought with it an unprecedented demand for professionals in all sectors of our economy. Nowhere is that more true than in the mining and metallurgy sectors. However, this welcome improvement follows on the heels of almost two decades of challenging markets for the mining and metallurgy. Our sector's protracted economic slump created a paucity of demand for professionals that had several consequences. Our industry came to be viewed as a low ?tech, uninteresting place to work. Low demand for professionals encouraged students to seek other career options. Reduced demand for graduates, coupled with diminished program funding by our sector, resulted in dramatic shrinkage in university mining and metallurgy programs. This paper explores the lessons to be learned from our recent economic history and discusses some strategies for addressing our image issue. Attracting and retaining good employees is also strongly influenced by a company's reputation and record as a good employer. This reality is very well illustrated by the findings of an international survey undertaken by Towers Perrin in 2005 of 86,000 employees of mid-sized and large companies in 16 countries. The key findings related to attracting and retaining employees are presented. These findings are also discussed in the context of their specific applicability to the mining and metallurgy industry.

Jan 1, 2007

By J. D. Stinnette

Traditionally, airflow requirements for diesel equipment operating in underground environments such as mines and tunnels were determined by multiplying the vehicle power by a ventilation rate that was either mandated by regulations(s) or determined empirically from known quantities. In some cases, utilization factors were further used to adjust (reduce) the total airflow calculations for a diesel equipment fleet. However, in light of the drastic reductions to diesel equipment emissions mandated by the US EPA Tier IV and EURO Stage 4 regulations, there is currently a great deal of uncertainty in the underground mining industry among those responsible for the ventilation of planned new mines or the expansion of current mines. Tier IV engine standards mandate a reduction of DPM and NOx of approximately 95%, but can ventilation rates at mines with Tier IV equipment (or equivalent) really be reduced by a factor of twenty? This paper outlines some of the factors that affect the airflow required for the ventilation of modern diesel-powered equipment and examines how they can be applied in determining a reasonable ventilation rate for Tier IV compliant equipment operating in subterranean environments.

Aug 1, 2013

By R. C. Snider

The Roy Lloyd Mine in northern Saskatchewan is a high-grade underground gold mine which is currently supplying ore to Golden Band Resources Inc. (Golden Band)?s Jolu mill. Prior to the operation of the mine, an underground exploration program was conducted intermittently at the site. During both the underground exploration phase and mining, Golden Band has implemented water recycling to reduce freshwater usage within the mine in order to address concerns over the potential for impacts associated with freshwater usage and to reduce the volume of effluent discharged from the site. Golden Band initiated an underground exploration program at the Roy Lloyd Mine site (formerly called the Bingo Project) in October 2007 to better delineate the mineralization of the Bingo gold deposit. The exploration program provided geological information required in order to improve the confidence level of the geological resource model and also provided information to aid in the mining of the deposit, such as the determination of groundwater inflow rates. Underground production mining started in March 2011. This paper provides an overview of the mine water recycling methods implemented at the site during both the exploration and initial mining phases of the project, and the success/drawbacks of these measures to date, including the potential cost savings in the form of reduced treatment and monitoring costs inherent in a reduction of the volume of effluent discharged from the site. The paper will also discuss options that are currently being evaluated in order to further assist Golden Band?s ability to recycle water and reduce the volume of effluent discharged to the environment, while ensuring effluent discharged from the site to the environment meets criteria.

Nov 1, 2011

By R. Harris

The vacuum thermal route for magnesium production today accounts for roughly 80% of the global production of magnesium despite significant investment in the competing electrolytic technologies, This is up from 30% of the global production 10 years ago and is all the more significant because global magnesium production has more than doubled in the same time, A review of the sophisticated anhydrous magnesium chloride production technologies provides some explanation for this sea change in technology usage, However, an examination of the economic factors provides compelling reasons, The present review outlines some of the salient strengths and weaknesses of the competing technologies, It also offers suggestion as to where future R and D and economic effort needs to be vested to improve the sustainability of the world magnesium market in terms of its value and impact.

Jan 1, 2006

By Don Peel, Jeremy Richards

Abstract - Aggregates (sand, gravel, and crushed stone) are low unit-cost products extracted in very large volumes for the construction of buildings, roads, and other infrastructure essential to modern society. Because of their low unit value, transportation costs are a key factor in resource economics, and deposits are commonly developed close to market (i.e., close to towns and cities, or along low-cost transportation corridors). This proximity results in potential conflict with residents over land use, disturbance, and pollution. Management of aggregate resources in Alberta is examined in the light of resource geology and distribution, and governance. A case history of development of the Calahoo-Villeneuve deposit is described, and the conflicts between residents and developers that led to establishment of an Area Structure Plan (ASP) are explored. The plan sets limits to, but at the same time safeguards, resource extraction, and defines terms for compensation to residents through a voluntary levy on production (Community Enhancement Fund). This fund is used to support community activities and to pay for a groundwater monitoring program. The ASP is examined within the context of the "Seven Questions to Sustainability" as set out by Mining,Minerals and Sustainable Development-North America (2002). It is concluded that the ASP, for the most part, provides a good model for conflict resolution and sustainable resource development, which could usefully be applied in other jurisdictions. The ASP was developed at a municipal level, and adoption at a provincial level would aid sustainable development of aggregate resources across the province.

Jan 1, 2003