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By G. B. Bosworth, M. J. Lake, J. W. Hogg

The Quintette Coal operation in northeastern British Columbia has one of the world's largest Preparation Plants, with a design capacity of 6.5 million tonnes per year of clean coal.This paper will discuss several innovative aspects of the flowsheet and plant design with particular reference to the selection of process equipment, materials handling and control systems.The operations and maintenance experience during the first two years of production will be described and discussed in relation to the design objectives.

Jan 1, 1987

By Y. Qi

A cell-level nonlinear dynamic model of solid oxide fuel cell (SOFC) based on physical diffusion principles is built in this note. It demonstrates that reactant diffusion processes from gas flow bulks to triple phase boundaries (tpbs) play an important role in the dynamic behaviors of SOFC. The simulation shows that under certain condition, the effect of the double layer capacitance may be neglected. The phenomenon of slow rise of voltage in current interrupt experiment may be explained by the dynamic behaviors of partial pressures in the vicinity immediately above tpbs.

Jan 1, 2005

By Steve Simard

Suite aux excellents résultats, obtenus avec la technologie des détonateurs électroniques dans des chantiers longs trous de grandes dimensions, nous avons décidé d?étendre cette technologie dans les ouvertures, dans le dynamitage de piliers et dans différents chantiers complexes. Cette technologie nous a permis d?effectuer l?abatage de chantiers avec un très grand nombre de trous sans détériorer le terrain. L?équation est bien simple avec les détonateurs électroniques, plus gros sont les dynamitages moins de fois les épontes se font ébranler, moins de blocs d?effondrement se retrouvent dans les points de soutirages entre les dynamitages et plus la fragmentation est meilleure. La flexibilité d?opération que nous avons obtenu avec les détonateurs électroniques est difficilement quantifiable, mais elle nous a permis de maintenir notre rythme de production mensuelle même avec certains chantiers complexes. Il est bien certain que l?utilisation des détonateurs conventionnels a encore sa place dans une mine conventionnelle comme Beaufor, mais l?utilisation des détonateurs électroniques a aussi sa place dans certaines situations spéciales. Pour terminer, bien que la technologie des détonateurs électroniques soit encore dispendieuse, nous pensons encore l?utiliser pour optimiser certains dynamitages et ainsi maintenir notre flexibilité d?opération.

Oct 1, 2004

By D. T. Smith, S. J. Strohmayr

Originally developed as a step change in ultrafine grinding efficiency, the IsaMill™ has made inroads into conventional ball mill and tower mill mainstream grinding duties during the last 5 years - beginning with the Anglo Platinum mainstream grinding projects in South Africa. At the 2006 SAG Conference, plant testwork on the incorporation of IsaMill™ technology into the McArthur River (Northern Territory, Australia) Pb/Zn primary grinding circuit was reported. The IsaMill™ has now become an integral component of that circuit, treating up to 1mm top size feed and directly producing P80 45 µm rougher flotation feed. Two 1.1 MW IsaMills™ are now used in this duty contributing to a 27% increase in overall plant throughput and a reduction in rougher feed size distribution. In this paper, we report on the current state of development and performance of the IsaMill™ in the primary grinding duty at McArthur River and also consider future directions.

Jan 1, 2012

By D. S. Cronan, S. P. Varnavas

Abstract - Metalliferous precipitates from submarine hydrothermal discharges have been investigated at four inshore locations off Milos in the Hellenic Volcanic Arc. The fine fraction of the sediments shows considerable variability in the concentrations of elements frequently associated with hydrothermal activity. Manganese varies from 30 ppm to 2500 ppm, encompassing the entire range of values found off Santorini also in the Hellenic Arc. Iron occurs in lower concentrations than off Santorini and Yali, while other elements often associated with hydrothermal activity such as Pb, Zn, As, and Cu also show enrichments in sediments from the hydrothermal vent areas. Selective leaching studies have shown that most elements are variably distributed between the different phases of the sediments but with enriched Pb, Zn, and Mn mainly in easily soluble secondary phases. Hydrothermal inputs are strongest at Palaeochori Bay, less at Voudia Bay and lowest at the Airport Springs and Rivari. The weathering of sulfide and possibly other orebodies is also thought to contribute to some of the elements enriched, while background concentrations are largely supplied from detrital sources.

Jan 1, 1999

By Bruno Bussière

Acid Mine Drainage (AMD) from mine wastes is one of the most environmental challenge currently facing the mining industry. AMD is the result of the natural oxidation of sulphides exposed to air and water. When mining wastes have the potential to produce AMD, these reactive wastes have to be managed to meet existing environmental regulations. The LTA site (property of Barrick Gold Corp.) contains sulphide tailings that have the potential to generate AMD. The closure option Barrick selected was to construct a multilayered cover with capillary barrier effects (CCBE). The main objective of this CCBE is to prevent the production of Acid Mine Drainage (AMD) from the tailings stack covering an area of approximately 60 ha. Since its construction in 1996, the cover has been monitored to evaluate its performance. Two of the measured parameters are volumetric water content and matrix suction. This paper presents some of the main results from the monitoring program that started seven years ago. The results show that the cover is largely able to maintain a high degree of saturation (greater than 85%) in the moisture-retaining layer. The actual performance of the CCBE on the flat surface of the 60 ha site is even better than expected at the design stage. The area that requires more specific attention with the LTA cover is the influence of slopes that can reduce the performance of the CCBE during dry periods. However, these effects seems to be local and do not significantly affect the overall performance of the CCBE to mitigate the production of AMD at the LTA site.

May 1, 2003

By L. Xia, B. Hart, K. Douglas

In the flotation of Rare Earth Element (REE) bearing minerals, oxalic acid is reportedly acting both as a depressant and pH modifier. Testing has established the significance of oxalic acid in the flotation process however its specific role in either the recovery or selectivity of REE over their gangue minerals is not well understood. Pulp pH reduction trials with alternative acids have not shown the same effect on the REE mineral recovery or the depression of gangue phases. This work examines the effect of oxalic acid on the surface of gangue minerals (quartz and carbonates (dolomite and calcite)) in a series of conditioning tests. Gangue surface analyses by TOF-SIMS indicate that oxalic acid inhibits the transfer of secondary ions generated during the conditioning process from one mineral phase to another. In this regard, the oxalate anion acts to fix ions in solution through chelation, limiting their participation in surface adsorption.

Jan 1, 2014

By Xuehui Xia

Abstract -There are a number of sedimentary exhalative massive sulfide (SEDEX) deposits in the Proterozoic Langshan-Zhaertai rift at the western segment of the northern margin of the North China platform in China, including more than ten large, medium and small deposits located in a belt of 300 km EW by 50 km to 100 km NS, with large Cu, Pb, Zn, Ag, and S reserves. In several representative SEDEX deposits in the rift, the mineralizing elements are prominently zoned, horizontally or vertically, with Cu decreasing but Pb increasing from west to east, Cu decreasing but Zn increasing from bottom to top, and Zn restricted to the bottom half. The ore-hosting rocks, characterized by a clear manganese halo, have developed a polymetallic mineralization in positive relation with their carbon contents. Their isotopic aspects are: ?34S has relatively large positive values, fluctuating between +5‰ and +35‰, compared with Pb isotopic compositions which are less variable, with a model age of 1600 Ma to 1800 Ma, showing that they are mantle-derived. The mineralizing materials were associated undoubtedly with the contemporaneously faulting events in the rift. The deposits owe their origin to seafloor exhalation, with sedimentary rocks as their hosts.

Jan 1, 1999

By J. Fournier

A novel sol ? gel (SG) synthesis procedure utilizing varying ratios of glycine and ethylene glycol to total metal cations has been developed to create high purity nanometer sized La0.65Sr3.5MnO3 powders. X-ray powder diffraction (XRD), transmission and scanning electron microscopy (TEM, SEM), and dynamic light scattering (DLS) have confirmed that the crystallite sizes of such powders are ~ 20 nm, and the aggregate particle sizes vary between 100 to 300 nm. Mixing varying weight percents of SG LSM powders with commercially available Praxair LSM in a composite LSM/YSZ functionally graded cathode has been shown, through the use of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), to exhibit enhanced oxygen reduction kinetics vs. at conventional cathode materials.

Jan 1, 2005

By R. J. Chase, C. Davies

"The Merelani graphite-tanzanite deposit is located in northeast Tanzania, 14 kilometers south of Kilimajaro International Airport and in close proximity to the towns of Moshi and Arusha. The graphite mineralization is hosted by relatively undeformed linear Proterozoic metasedimentary gneisses, several of which have been subjected to hydrothermal alteration resulting in tanzanite mineralization. Exploration work comprised detailed geological mapping coupled with pit and trench channel sampling and a subsequent 1500 meters of diamond drilling. In addition, metallurgical tests have shown the graphite to be of unusually coarse flake size, crystallinity and high purity.Feasability studies have shown the economic viability of a major coarse flake graphite deposit with the measured resource to 50 meters in excess of 9 million tonnes assaying over 85 graphitic carbon. Production is due to start by the end of the first quarter of 1994 with the processing plant design capacity initially set at 15 000 tonnes per annum.In addition to graphite production, tanzanite will be produced through selective mining within the graphite open pit in the upper horizon and from underground workings within the lower horizon.The Merelani graphite-tanzanite deposit will be the first major orebody to be exploited through means of private funding since Tanzania gained independence"

Jan 1, 1994

By A Smirnov

The problem of thin and very thin coal seam extraction is examined in a long perspective of Ukraine?s fuel and energy industry development. The technical and economic benefits of the coal seam selective mining technique are described, including beneficial environmental impact.

Aug 1, 2013

By Ken G. Stowe, Stephen L. Chryssoulis, Christian Bendel, Joe Y. Kim, Ewald Niehuis

"TOF-SIMS (Time-of-flight secondary ion mass spectrometry) was used to detect collectors sorbed onto the surface of mineral particles in concentrate and tailings samples from the Brunswick, Matagami and Kidd Creek concentrators. This technique uses ion beams from either Cs or Ga sources to sputter the particle surface, a method which reduces fractionation of the collector molecule during sampling.In the Brunswick Zn circuit, sphalerite particles lost to the scavenger tails had less amyl xanthate and isobutyl xanthate compared to sphalerite recovered to the Zn final concentrate. Xanthates were detected on the surface of sphalerite particles floating to the CuPb final concentrate.At Matagami, significantly more isopropyl xanthate and isobutyl dithiophosphate were detected on sphalerite recovered to the Zn final concentrate, compared to sphalerite lost in the Zn rougher tails.In the Zn circuit of Kidd Creek, sphalerite lost to the tails had on average ten times less xanthate compared to sphalerite recovered into the Zn final concentrate. Xanthate was also detected on the floated pyrite particles. In addition to isobutyl xanthate, amyl xanthate was also detected on the floated sphalerite and pyrite particles.This preliminary investigation has (a) demonstrated the ability of TOF-SIMS to detect individual collectors on particle surfaces from plant samples and (b) shown that TOF- SIMS is an excellent tool, complimentary to TOF-LIMS, in establishing the surface chemistry of minerals as related to mineral processing."

Jan 1, 1995

By V. I. Birss

Planar solid oxide fuel cells (SOFCs) offer great promise as stationary power generation devices, primarily due to their flexibility in terms of fuels, high energy conversion efficiency (when both electricity and heat are captured), and their relatively low fabrication costs. However, the anode performance can be compromised by such factors as exposure to certain sulfur-containing fuels and the deposition of coke when using hydrocarbon fuels. In terms of the cathode, its performance is limited primarily by the slow kinetics of the oxygen reduction reaction, while its lifetime can be negatively affected by factors related to the corrosion of currently used stainless steel interconnect materials. This talk will present an overview of these challenges and some possible solutions to these problems. The presentation will also focus on how electrochemical methods can be used to evaluate and improve the performance of SOFC anodes, cathodes, and interconnect materials. In addition, recent promising research efforts directed towards performance enhancement of SOFCs through the use of nanoscale electrocatalysts will be discussed.

Jan 1, 2005

By Weimin Fu

Chondrite-normalized rare earth elements (REEs) profiles and high field strength elements (HFSEs) in rocks and minerals represent important tracers of geological processes. Of these the birdwing-shaped profile with negatively-sloped light REE ((La/Sm)N >1), positively-sloped heavy REE ((Tb/Yb)N <1), and strong negative Eu anomalies is commonly associated with large-scale hydrothermal systems or granitic intrusions. In a different way, severe deviation of Nb/Ta, Hf/Sm ratios from those of chondrite may also indicate hydrothermal signatures in the rocks involved as these ratios are generally stable and chondritic in normal magmatism as a result of their nearly identical ionic radii and charge. In this study, we present a typical setting where birdwing-shaped REE profiles together with Nb/Ta, Hf/Sm ratios unusually higher than those of chondrite, are systematically developed in a series of garnetite, quartzofeldspathic gneiss, Fe- or Mg-rich aluminous gneiss, and sulfides and magnetite. These units and associated Cu-Au mineralization form a VHMS-style hydrothermal system in the granulite-facies 1.4 Ga -1.35 Ga volcano-plutonic, arc-related Bondy gneiss complex (BGC), western Grenville Province, Canada. Outside the recognized hydrothermal system of the BGC, such REE profiles are not observed. Instead the surrounding felsic and mafic gneisses display primary trace element characteristics of island-arc magmas, suggesting that granulitefacies metamorphism did not modify significantly the trace element signatures of the protoliths. Although magmatic fractionation of accessory minerals can produce birdwing-shaped profiles, it cannot explain the extreme fractionation of isovalent trace elements (Nb-Ta) and the high Zr content of the hydrothermal rocks. Neither is it compatible with the lack of significant Nd depletion that would normally incur during this process. Following our study, we demonstrate that F-rich fluid and mineral phases enriched in LREEs and HREEs respectively must have been involved in the main hydrothermal alteration and REE fractionation process in the BGC. Preferential removal of REEs from the interstitial glass of the volcanic protoliths together with dissolution of plagioclase and subsequent external influx of HREEs and HFSEs can produce birdwing-shaped REE profiles. In turn, such profiles and/or unusual Nb/Ta, Hf/Sm ratios can be used as a sensitive marker of hydrothermally altered rocks in targeting mineral exploration.

May 1, 2003

By Xuanxue Mo, Kaihui Yang

"The Laochang mine, located in the Sanjiang area of southwestern Yunnan Province of China, is a volcanogenic massive Pb-Zn-Cu sulfide deposit. It is hosted by a pyroclastic sequence of Early Carboniferous age, namely the lower member of the Yiliu Group, which was intruded by syenite and rhyolite porphyry. The volcanic suite is basaltic or basaltic-andesitic in composition, has alkaline affInities, and is associated with the initial rifting along the margin of the Baoshan-Shanstate continental microplate (Yang, 1989). The ores are typically Pb>Zn>Cu in composition, averaging 3.820/0 Pb, 3.51% Zn, from 0.01% to 1.85% Cu (0.107% av.), a high average content of Ag (113 glt) and recoverable amounts of Au, n, Gd, Ga, Ge, In. A massive sulfide zone, in which lenticular and stratiform orebodies are localized in a sulfide-<:arbonate-silica shale unit or sulfidic tuffIte horizon that usually overlies coarse-grained pyroclastic rocks, is underlain by a stringer sulfide zone developed in a subvolcanic intrusion or volcanic sequence. The sulfIde mineral assemblages, from the top to the bottom of the deposit, are: realgar + orpiment - galena + sphalerite + pyrite - chalcopyrite + pyrite + pyrrhotite + arsenopyrite. Oxide and sulfate minerals occur rarely in the massive ores. The massive ores are generally fme-grained and banded, but coarse-grained ore, colloform and framboidal texture, and growth-zoned pyrite and sphalerite are common. Sedimentary features such as graded bedding, brecciated and deformed ore clasts, and chaotically emplaced blocks, are well preserved, indicating that the massive orebodies have undergone slumping and displacement. Alteration is weak in the hanging-wall rocks, but strong in the stringer zone. Two distinctive alteration zones have been identifIed: the upper zone, characterized by an assemblage of quartz, carbonates, chlorite, albite, zeolite and sericite, and the lower zone containing diopside, tremolite, actinolite, gamet, clinozoisite, and epidote.The general features of the Laochang deposit are in accord with the descriptive model of VMS deposits (Lydon, 1984). However, it falls into neither the Zn-Cu group nor the Zn-Pb-Cu group chemically (Franklin et al., 1981). The depositional setting of the Laochang deposit is quite different from Cyprus or Besshi-type massive sulfide deposits. Laochang is hosted by alkaline lavas that were erupted in a submarine continental rift. Although some features of the Laochang deposit are similar to those of Kuroko-type deposits, there are remarkable differences in the alteration mineral assemblage, the proportion of ore-forming elements (lead enriched) and the amounts of oxides and sulfates. These suggest corresponding differences in ore fluid composition and the associated ore-forming environment. Thus, the authors suggest that the Laochang deposit may be a distinct type of VMS deposit."

Jan 1, 1993

By Jocelyn Koshinsky

The uranium milling process at the Key Lake Operation of Cameco in Northern Saskatchewan, Canada results in the leaching of untargeted metal(loid)s such as arsenic, iron and nickel that are found at high concentrations in the ores. To mitigate the environmental impact of the leached As, Fe and Ni in the mill waste solution (raffinate), the pre-discharge mine tailings (rafffinate and residue) are neutralized with slaked lime, resulting in the formation of secondary As-, Fe- and Ni-bearing mineral phases which serve to control their concentrations to very low levels in the tailings porewater. As part of an ongoing investigation into the long-term evolution (10,000 year) of arsenic mineralogy in the Deilmann Tailings Management Facility (DTMF) at Cameco?s Key Lake Operation, it has become necessary to characterize secondary As-bearing mineral phases during the neutralization process prior to the discharge of the tailings and compare these to in situ As-bearing mineral phases in the tailings facility. This is primarily to determine if changes have occurred over time to As-bearing mineral phases in the tailings facility as well as to investigate whether alternate neutralization techniques may have a beneficial effect on the stability of mineral phases formed. Thus a bench-scale model was developed and preliminary testing conducted to simulate the mill neutralization process (i.e. neutralization of synthetic raffinate solutions with incremental amount of slaked lime to terminal pH values). The resulting ?tailings? (precipitates and supernatant) were then separated and analyzed. XRD analysis of the precipitates shows that the Fe occurred mostly as ferrihydrite. This was complimented with results from Raman spectroscopy which further indicated that the As appeared adsorbed onto the ferrihydrite. Results of geochemical modeling of the bench-scale test compared well with supernatant profiles from ICP-MS analysis.

Aug 1, 2010

By B. R. Maas

Processing material at a consistent rate through the continuous countercurrent decantation (CCD) thickeners presented a major bottle neck to unlocking additional value from one of the post-flotation streams at the Kansanshi processing plant. The manual operation of the thickeners making up the CCD train resulted in frequent imbalances and process upsets across units. The automation of CCD trains is notoriously tricky as the available manipulated variables are outnumbered by the parameters requiring regulation. The implementation of an advanced, auction-based, control philosophy to manage the movement of both slurry and solution inventory through the train addressed this parameter imbalance and lead to the stabilisation of the circuit. Since the commissioning of this control strategy: an additional 7 200 dmt/day (+36% throughput) of material can reliably be processed through the train, the number of monthly downtime events has reduced, and a saving of $354 000/month in reagent cost has been achieved. INTRODUCTION CCD operation Agitated leaching is a common method used in hydrometallurgy to extract a metal from its host ore. The host ore is initially finely ground to liberate the surfaces of the valued minerals and improve the kinetics of the leaching process. The ore is then contacted in an agitated tank with a lixiviant to dissolve the desired metal into the aqueous phase. The resultant slurry from the leaching process comprises of a solution pregnant in the metal salt and a barren ore. The first purification step taken after leaching is to wash the pregnant liquor solution (PLS) from the depleted ore. On the industrial scale, a set of between two to ten thickeners arranged in a countercurrent configuration is often used to carry out this separation (Perry & Chilton, 1973). The slurry is introduced at the head of the train and a wash solution at the tail. The two streams are pumped through each thickener countercurrent to one other. At each stage the residual PLS in the slurry is mixed and diluted down with the countercurrent overflow solution from the downstream thickener. The diluted slurry is fed into the thickener where the solids separate out through gravity sedimentation. The settled solids are channelled towards the underflow of the thickener by a rake mechanism and pumped downstream to the next thickener in the train. The outcome is the recovery of a PLS from the overflow of the lead thickener and a slurry of washed solids from the underflow of the tails thickener.

Jan 1, 2019