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By Michel Ruel, Ali Soltanzadeh

This paper describes how to make advanced control choices when difficult processes need improvement. The decision-making process involves choosing between a rules-based approach and a model-based approach as well as weighing benefits and drawbacks, complexity and simplicity, investment and results. This paper will present briefly each solution: basic control, advanced regulatory control, model predictive control and expert systems such as fuzzy logic controllers and neural networks. Three examples are presented: ARC (Advanced Regulatory Control) on pH in a comminution circuit, MPC (Model Predictive Control) for combustible management and FLC (Fuzzy Logic Control) on a Semi Autogenous Mill. The article then proposes a decision tree for selecting the most appropriate approach. A table will compare usage, development, commissioning, maintenance and lifecycle costs for each approach. Finally, conclusions and suggestions will summarize the methodology.

Jan 1, 2014

By Maureen A. McGuinness

Kidd Mine, an Xstrata Copper operation in Timmins, Ontario, operates a 400 t/h pastefill plant that provides paste backfill to stopes at the depth of 9000 ft. This paper will cover the operating practices of the pastefill plant both on surface and underground, highlighting tailings excavation, paste mix design and the pipe maintenance program. Kidd Mine, une opération d'Xstrata Copper à Timmins, Ontario, opère une usine de remblai d'une capacité de 400 t/h. Le réseau de distribution permet d'acheminer le remblai en pâte juste qu'à une profondeur de 9000 pi. Cet article couvrira le mode opératoire de l'usine de remblai tant à la surface que sous-terre en mettant l'emphase sur l'extraction des rejets miniers, la recette du remblai en pâte ainsi que le programme d'entretient du réseau de distribution.

Feb 1, 2008

By L. Bichler, C. J. Verdon

In this work, the effect of doping yttria stabilized zirconia (YSZ) with 5, 10 and 15 mol% erbium oxide (Er2O3, erbia) was investigated using spark plasma sintering (SPS) technique. Sintering was carried out at 1300°C with 30 and 60MPa uniaxial pressures and a 5min hold time. Densification kinetics were studied using displacement response from the SPS machine. As-sintered microstructure characterization was carried out via scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques, while chemical composition was characterized by energy dispersive X-ray spectroscopy (EDS). The results suggest that sintering carried out at 60MPa produced high density composites even though erbia dopants were found to inhibit material densification and grain growth during sintering. 5, 10 and 15mol% erbia- YSZ had cubic crystal structures, as verified by XRD analysis.

Jan 1, 2014

By M. Pierce

Empirical relations exist for the estimation of rock block strength at scales larger than standard core sizes. Two recently published relations account for the significant impact that microflaws (pores, open cracks, veins) and weathering/alteration can have on scale effect. These relations were used to estimate the rock block strength of heavily microfractured quartzite from the Bingham Canyon Mine. Predictions were compared to the results of Uniaxial Compressive Strength (UCS) tests conducted on cylindrical core samples of varying microfracture intensity and diameter. The comparison confirms the sensitivity to microfracturing suggested by existing relations and suggests that they would benefit from more detailed consideration of microfracture strength, density and persistence over a range of scales. The results of a numerical study illustrate how Synthetic Rock Mass (SRM) modeling techniques could be used to complement empirical data in the development of such relations.

May 1, 2009

By H. Lachmund, R. Bruckhaus

At Dillinger Hüttenwerke/Germany steel production of grades for linepipe applications especially for sour service has a long tradition. The BOF process after replacement of the vessels is optimized by a newly developed lime addition model and variations in lance tip geometry. Equipped with three state-of-the-art VOD tank degassers metallurgical requirements of lowest contents of e. g. sulphur, nitrogen and hydrogen can be achieved. Three continuous casting machines of vertical bending type with solid core even improve already high levels of cleanliness. The vertical part corresponds to the metallurgical length of 12 to 15 m and therefore assures a maximum of cleanliness after solidification before bending. Slab thickness up to 400 mm can be produced with model controlled dynamic soft reduction. The accurate alignments of the casters assure minimized segregation and microporosity. Surface and internal cracks can be avoided by special cooling, bending and straightening strategies.

Jan 1, 2005

By Guojun Wang, Zejun Chen, Wenchang Liu

Al/Mg/Ti laminated metal composite sheet (LMCS) can combine the merits of each of metal components, and obtain excellent performances. It incorporates the advantages of high strength, light weight, easy melt and atomization, and good space adaptability to substitute for the bumper Al sheet of Whipple shield structure for space debris shield. The Al/Mg/Ti LMCS was fabricated by hot roll bonding technology in a certain sequence. The manufacturing process and parameters were analyzed and studied, including the first rolling reduction, roll boding temperature and stacking structure of each metal. The microstructure of dissimilar metals and bonding interface were characterized and analyzed. The optimized manufacturing procedures and parameters were presented based on the microstructure and mechanical properties of LMCS. The research results offer some guides and references for controlling the shape of bonding interface, optimizing the annealing process, improving the mechanical properties of Al/Mg/Ti LMCS.

Jan 1, 2015

By H. M. Lewis

The current status of the international zinc market is summarized, and a supply /demand outlook is presented for the next five years. A number of technical problems facing the industry are outlined. Introduction ZINC has sometimes been called the unknown metal. Considering that on a world basis it ranks third among non-ferrous metals in production and consumption, zinc retains a certain modesty. It has no distinctive colour like copper, lacks the low density of aluminum or magnesium and is not always easy to identify as a product. The 'spangle' of galvanized steel is probably zinc's most distinguishing feature. The purpose of this article is to develop an over-all review of zinc. Starting with the current position of the metal, the major factors that will shape its future will be described so that an assessment of the outlook for zinc can be made.

Jan 1, 1978

By C. G. Anderson

Alkaline sulfide leaching technology (i.e. ASL) has been studied, presented and published throughout the literature and utilized in some current engineering studies. Yet, the actual industrial applications are very few and the knowledge about these is very limited. Hence, a large gap between the laboratory, publications, engineering studies, and the actual industrial plant exists. Recent studies of ASL applied to copper enargite concentrates definitively bear out this dichotomy. Hence, this paper will seek to dispel the common misperceptions that continue to surround the selective industrial ASL hydrometallurgical technology. For edification of the reader, a listing of ten common misconceptions and myths is listed. As well, ASL history, fundamental aspects and a new flowsheet application for simultaneous gold and high purity antimony oxide production from low grade materials is included. The associated estimated economic considerations are also included to heighten enlightenment about the application of this industrially proven technology.

Jan 1, 2014

By Xiu-Xiang Tao

This study investigated bio-liquefaction of lignite and its model compounds of thymol, bezioc acid and quinoline by a fungus, Hypocrea lixii AH. It analyzed, during bio-liquefaction, enzyme activity of oxidase, LiP, Lac, MnP and polyphenol oxidase, and degradation products by UV-Vis, FTIR, 13C NMR and GC-MS. The results showed that the bio-liquefaction percentage (by mass) of lignite was up to 44.86 %. The bio-liquefaction products of lignite were mainly aniline, amide, ether, carboxylic acid ketone and ester. The aromatic ring number was 1-3 with an aromatic carbon ratio of 0.328, which indicated rings opening, bonds breaking and oxidation reaction. By considering with the enzyme activity analysis results, it showed that LiP and Lac catalyzed reactions to open aromatic cycles and to break bonds; esterase to break ester bond; and peroxidase in oxidation reaction.

Aug 1, 2013

By Nick D. Rose

The Dy deposit is a 21 Mt Pb-Zn-Ag-Au SEDEX-type massive sulphide resource located in the Anvil District, Faro, Yukon. This relatively unexplored orebody lies at a depth of 480 to 920m below surface, dips 20 to 35o and comprises vertical ore thicknesses of 3 to 28m at a 9% Pb + Zn cut-off grade. The deposit has been tested at depth with 63 surface diamond drillholes, but has not yet been explored or developed by underground means. Over the past decade, pre-feasibility investigations were conducted for two separate owners of the property to determine the economic viability of developing an underground mine at Dy. Following these previous studies an assessment was undertaken between 1998 and 2000 to further investigate geotechnical considerations for underground mining. The results and conclusions drawn from this study provide direction for possible future exploration at Dy.

May 1, 2002

By Scott Hopkins

Simulation tools are preferred for evaluating complex systems due to its ability to mimic reality and quickly evaluate many different what-if scenarios and find global solutions. A simulation model is capable of representing variable and dynamic disturbances that are typically encountered in day-to-day operations; this is where spreadsheet models or linear programs fall short because they cannot account for the dynamic behavior and relationships. The simulation model used for this work was developed by Xstrata-Nickel (previously Falconbridge). The simulation tool is very flexible and can be used to simulate different mining and development methods. The scope of the modeling included production mining, geology, equipment fleets, equipment maintenance and random failures, manpower, shift schedules, and cycle activity times. A case overview of the 170 Orebody will be presented along with the challenges associated with data collection for the model inputs. Results and lessons learned will also be discussed.

May 1, 2008

By G. Deschenes

"This literature survey discusses the recovery of gold from thiourea solutions. An overview of techniques used and general comments on the basic cyanidation methods are presented. The chemistry and mechanisms of cementation, activated carbon, resins, electrowinning, solvent extraction and pressure reduction are examined. Conclusions and recommendations give orientation for future research and development activities in this field.RésuméCette revue littéraire traite de la récupération de I ‘or des solutions de thiourée. Elle fait un survol de I ‘ensemble des techniques utilisées tout en introduisant des commentaires généraux sur la méthode classique qu'est la cyanuration. La cémentation, Ie charbon active, les résines, l'électroextraction, I ‘extraction par solvant et la réduction sous pression sont les méthodes analysées tout en considérant leur caractère chimique respectif ainsi que les mécanismes qui y sont rattaches. Des conclusions sont tirées et différentes recommandations sont suggérées pour orienter la recherche dans ce domaine."

Jan 1, 1986

By J. Schmidt

Cold drawing of copper wire rod is usually combined with an in-line annealing process to adjust the ductile microstructure of the wire again. One important key factor for successful annealing is the quality of the copper itself. Rod producers can check the recrystallization behaviour of the rod by different methods: chemical analysis, Spiral Elongation Test (SEN) as well as the Rapid Elongation Test (AR) are some examples of common testing methods. The comparison of the results of these methods does not always show sufficient correlations. The paper introduces firstly the SEN and AR-Tests and their different approaches to the mentioned task. The second step is to compare some results of the SEN-Test with the results of the AR-Test and identify causes of deviations. Thirdly, the effect of pre-annealing is discussed, which is especially common for wire rod with diameters of more than 8 mm.

Jan 1, 2007

By M. S. Moats

As smelter feeds become more complex, the impurities that ultimately report to electrorefineries are changing. Many of these impurities collect in the electrolyte and must be controlled. As commercial copper electrorefineries look to expand their capacities by increasing their operating current density, the interaction between electrolyte composition and anode passivation can cause operational difficulties. To improve the industry's understanding of the passivation phenomena, the role of electrolyte composition was evaluated using commercial electrorefining anode samples. The electrolyte composition variables examined were copper, acid, nickel, arsenic, chloride, thiourea and glue. Finally, the role of non-commercially utilized additives, such as bromide and polyethylene glycol were studied. From this investigation, electrolyte parameters that inhibit copper dissolution through copper sulfate precipitation, copper oxide stabilization and/or absorbed species lead to accelerated passivation. Species that prevent passivation have the ability to complex cuprous ions. Possible mechanisms for the role of each.

Jan 1, 2007

By M. Huang

Electrodeless conductivity was employed to investigate the feasibility of continuous on-line monitoring of the free acidity of sulphate and/or chloride solutions of Cu and other base metals from various hydrometallurgical processes. These solutions were measured with both commercial and experimental electrodeless conductivity sensors from 15 to 250°C. It was confirmed that hydrogen ion has the greatest impact on conductivity by carrying the bulk of the current because it is the most mobile ion. In combination with a solution speciation analysis the conductivity sensor can be calibrated to account for the contribution of Cu electrolytes as well other dissolved salts allowing fast and accurate on-line measurement of free acid. The sensor was tested at both lab and pilot scale with very good performance. The average difference between the measured and the titrated acid concentration was less than 5%, which is excellent for industrial applications.

Jan 1, 2007

By H De Beer

The 14MW SAG mill at Tarkwa, Ghana, experienced a frozen drop charge incident on 10 February 2010. This caused downtime of 112 hours, a repair cost of $200k and production loss of 162,000 tons, corresponding to a loss of $8.9M. A new locked charge protection system was installed on the two Tarkwa mills on 30 July 2010, mitigating this risk. This system calculates the ore angle in real time while the mill is starting up and trips the mill if the ore angle exceeds a trip angle setting. The calculation of the ore angle is derived from the mill motor rotor currents only - no mechanical transducers are required. The head of Gold Fields West Africa, Peter Turner, says of the new system: "This is excellent work and the type of technology that has had and will continue to have, major opportunity cost impacts on our business."

Nov 1, 2011

By P. van Zyl, M. Lombaard

The 14MW SAG mill at Tarkwa, Ghana, experienced a frozen drop charge incident on 10 February 2010. This caused downtime of 112 hours, a repair cost of $200k and production loss of 162,000 tons, corresponding to a loss of $8.9M. A new locked charge protection system was installed on the two Tarkwa mills on 30 July 2010, mitigating this risk. This system calculates the ore angle in real time while the mill is starting up and trips the mill if the ore angle exceeds a trip angle setting. The calculation of the ore angle is derived from the mill motor rotor currents only - no mechanical transducers are required. The head of Gold Fields West Africa, Peter Turner, says of the new system: "This is excellent work and the type of technology that has had and will continue to have, major opportunity cost impacts on our business."

Jan 1, 2012

By M. Isac, R. I. L. Guthrie, S. Ge

The Al-Mg-Sc-Zr alloys have shown exceptional potential as structural materials for transportation applications. These alloys have proved to be good candidates to be processed as thin strips via the Horizontal Single Belt Casting (HSBC) process. The HSBC process is a near-net-shape casting technology, which involves casting molten metal directly into thin strips, close to the final product thickness, at high cooling rates. It offers an efficient, economical and environmentally-friendly approach to the production of metal strips. Fluid mechanics and associated heat transfer are important aspects of any casting process, and the novel HSBC process is no exception. Three dimensional Computational Fluid Dynamics (CFD) simulations using ANSYS FLUENT 14.5 were performed, in order to assess the importance and effects of the various operational conditions of the HSBC process. This enabled process parameter optimization. Numerical predictions were validated against experimental casting results.

Jan 1, 2014

By Carlos Palacios M., Brian K. Townley

"Abstract - The mainland Aysén region of Chilean Patagonia (44°15' - 47°30'S) is a representative segment of the South American active continental margin, distinct with respect to northern and central Chile. Mineralization consists mainly of polymetallic deposits, with important Zn-Pb mines and more recently discovered Au-Ag deposits, unlike the central Andes, which are dominated by Cu mineralization. On a regional scale, rocks may be grouped in four main map units: 1) the Paleozoic metamorphic basement; 2) upper Jurassic-Cretaceous calc-alkaline volcanic and marine sedimentary rocks; 3) the Patagonian batholith, and 4) upper Cretaceous to Miocene basalts and marine and continental sedimentary rocks. The upper Jurassic-Cretaceous rocks and the Patagonian batholith formed in a volcanic arc and back-arc setting superimposed on the Paleozoic metamorphic basement.Based on geographic location and geologic and tectonic setting, ore deposits in this region are assigned to three groups, from south to north: El Faldeo, Fachinal, and El Toqui. The El Faldeo group (south of 47°05'S) includes upper Jurassic Zn-Pb skarn and associated polymetallic massive sulfide vein deposits locally overprinted by Au-rich epithermal mineralization, hosted by volcanic and sedimentary rocks and/or by rocks of the metamorphic basement. The Fachinal group (46°05' - 47°05'S) consists of volcanic-hosted lower Cretaceous Au-Ag epithermal deposits, except for the Mina Silva and Manto Rosillo deposits, which are metamorphic basement-hosted Zn-Pb skarns. The El Toqui group (44°30' - 46°05'S) comprises lower Cretaceous Au-rich Zn-Pb skarns and associated polymetallic veins, as well as Au-Ag-rich epithermal deposits, hosted by volcanic, intrusive, and marine sedimentary rocks. Galena lead isotopic signatures for each deposit group indicate a decreasingly radiogenic trend from south to north, suggesting different lead sources or differences among underlying crust. Three metallogenic provinces and two metallogenic epochs are proposed for the Aysén region: the El Faldeo metallogenic province of Late Jurassic age; and the Fachinal and El Toqui provinces of Early Cretaceous age. Résumé - La partie continentale de la région d’Aysen (Patagonie chilienne, 44°15' - 47°30'S), est unsegment représentatif de la marge continentale active d’Amérique du sud, différent des segments du nordet du centre du Chili. La minéralisation, qui consiste essentiellement en des dépôts polymétalliques, avec d’importantes mines de Pb-Zn, et des dépôts d’Au-Ag récemment découverts, différe de celle des Andes centrales où domine la minéralisation cuprifère. A l’échelle régionale, les roches peuvent être regroupées en quatre unités cartographiques principales : 1) le socle métamorphique paléozoïque, 2) les roches volcaniques calco-alcalines et les sédiments marins du Jurassique supérieur-Crétacé, 3) le batholite patagonien, et 4) les sédiments marins et continentaux ainsi que les basaltes du Crétacé supérieur-Miocène. Les roches du Jurassique supérieur-Crétacé et le batholite patagonien, formés dans un contexte d’arc volcanique et d’arrière-arc se superposent au socle métamorphique paléozoïque.Fondé sur la localisation géographique ainsi que sur le cadre tectonique et géologique, les dépôts de minerais de cette région se répartissent en trois groupes, du sud au nord, El Faldeo, Fachinal et El Toqui. Le Groupe El Faldeo (sud de 47°05'S) contient des skarns à Pb-Zn du Jurassique supérieur associés à des veines de sulfures massifs polymétalliques, localement recoupées par des minéralisations épithermales, riches en Au, et contenus dans des roches sédimentaires et volcaniques et/ou dans des roches du socle métamorphique. Le Groupe Fachinal (46°05' - 47°05'S) consiste en des dépôts épithermaux Au-Ag, se trouvant dans des roches volcaniques du Crétacé inférieur, excepté pour les dépôts de la Mine Silva et Manto Rosillo, où des skarns à Pb-Zn, se trouvent dans le socle métamorphique. Le Groupe El"

Jan 1, 1999

By L. H. McKay

Tailing Dams Three types of dam have been structed to impound tailings from the Allenby mill: 1.- By classifier unit 2.- By earth dam 3.- By direct deposition of tailings The first type, which includes two dams, was built across a shallow valley which sloped down to Similkameen river, just below the mill site. Two earth embankments, one below the other, were built across the valley. Tailings were then piped to Akins classifiers mounted on wooden wheels. The classifiers were set up at one side of the valley and gradually moved ahead on the sand embankment created by the sand discharge from these classifiers, the slime overflow going to settli.ng ponds formed by the dams. Decanting wells were built in the settling ponds by placing four six-by-six timbers vertically in the ground, two feet apart, to which two-by-six tongue-and-groove boards were nailed. The elevations of the ponds were raised, as required, by nailing additional two-by-six boards on the well and bolting on more six-by-six timbers when required. The bottoms of the wells were attached to a covered launder made of three-inch lumber laid on a one per cent grade. This launder carried the overflow through the dam. The second type of dam was built across a long, narrow valley, known as Hitchen's Flat, the upper ~n d of which was about 2½ miles north of the mill. This valley, an ideal tailings site, was 4,000 feet long and from 600 to 800 feet wide. An earth embankment with a concrete spillway through the top was built approximately 28 feet high across the lower end of this valley. Tailings were then dumped into the upper end of valley, with no further expense until the basin was filled up to the level of the flume where this entered the valley. When the upper end of the valley was filled to this point there was still room for more tailings at the lower end. Therefore, a pump was installed to elevate the tailings to build a wall around the upper end of the valley by depositing sands from a launder built up on 20 foot supports and sloping both ways from the pumping station around the upper end of the basin.

Jan 1, 1950