Greater Sudbury, Canada
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Suorineni F.T.,Laurentian University | Suorineni F.T.,University of New South Wales | Mgumbwa J.J.,Laurentian University | Kaiser P.K.,Laurentian University | And 2 more authors.
Transactions of the Institutions of Mining and Metallurgy, Section A: Mining Technology | Year: 2014

Part 1 of the paper defined shear loaded orebodies and showed through case histories that both pillars and excavations are at elevated risks of failure when mining these orebodies. Part 2 of the paper presents new knowledge on the behaviour of pillars and excavations when mining such orebodies. Numerical modelling is used to understand the behaviours of these structures in the orebodies. It is established that pillars in shear suffer confinement loss compared to their equivalents under pure compression. The confinement loss increases with increasing shear loading in pillars with width : height (W : H)§1. For pillars with W : H §1, the Lunder and Pakalnis (1997) empirical pillar design chart should be used with caution. For excavations in eccentrically loaded orebodies, passive and active high stress envelopes are created in the excavation process. The combined effect of the active high stress and tension zones often results in excavation surface sloughing. © 2014 Institute of Materials, Minerals and Mining and The AusIMM.

Moula M.G.,University of Guelph | Szymanski G.,University of Guelph | Shobeir B.,Vale Base Metals Technology Development | Huang H.,Vale Base Metals Technology Development | And 3 more authors.
Electrochimica Acta | Year: 2015

The anodic dissolution of two laboratory-made Ni samples obtained using the carbonyl method was investigated to understand the origin of residue formation in the anode basket in an electroplating tank. The first sample was obtained with 3 ppm addition of carbonyl sulfide to introduce a small amount of sulfur (CN-S sample). The second was obtained without sulfur impurities (CN sample). Linear sweep voltammetry and chronopotentiometry were applied to characterize the dissolution of these samples. The dissolution of the CN-S sample took place in the active region at low overpotentials. This behavior is determined by the presence of sulfur impurities that break down the passive layer and facilitate Ni dissolution. The CN sample without sulfur was dissolved at high overpotentials. The overpotential-time plots displayed regular large amplitude oscillations in which the overvoltage periodically moved between the transpassive and passive regimes. The anodic dissolution of this sample was controlled by two competing processes: breakdown and formation of the passive layer. Scanning electron microscopy and white light interference microscopy were applied to monitor the morphological changes of the two samples as a function of the dissolution time. The results of these studies showed that the CN-S sample dissolved uniformly across the surface. However, the roughness and the aspect ratio of the protruding features on the surface increased with time. This sample produced a fine residue due to detachment of small protruding crystallites. In contrast, the dissolution of the CN sample involved pit formation and took place predominantly from the bulk of the pits. The dissolution of this sample left a porous skeleton of more passivated Ni. The residue in this case consisted of large, porous chunks of the skeleton. © 2014 Elsevier Ltd. All rights reserved.

Bobicki E.R.,University of Alberta | Liu Q.,University of Alberta | Xu Z.,University of Alberta | Manchak N.,University of Alberta | Xu M.,Vale Base Metals Technology Development
Materials Science and Technology Conference and Exhibition 2013, MS and T 2013 | Year: 2013

Grinding required for mineral liberation represents the largest energy consumption in mineral processing. Great effort has been made to reduce the energy intensity of grinding. A process involving the treatment of ultramafic nickel ores by microwave irradiation prior to grinding has been developed. Two different ultramafic nickel ores were studied: one from a deposit near Thompson, Manitoba, Canada (Pipe ore), and the other from the Okanogan region of Washington State, USA (OK ore). Ore grindability and pentlandite liberation were studied as a function of microwave pre-treatment time. The costs and benefits of microwave pre-treatment are discussed specifically with reference to energy usage. Copyright © 2013 MS&T'13®.

Ewaschuk C.M.,McMaster University | Swartz C.L.E.,McMaster University | Zhang Y.,Vale Base Metals Technology Development
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2013

The manual scheduling of operations in a Converter Aisle for Nickel Smelting is both a timeconsuming and tedious task The challenge of manually scheduling this process involves several tasks on multiple units (such as tapping of matte from furnaces, charging of converters, blowing, and skimming slag from converters) Furthermore, these tasks need to be carried out subject to a number of operational constraints that include upper and lower matte level limits in the furnaces, and the number and timing of the blowing operations required for a converter batch This already complex set of tasks is further complicated by emission limits, which places additional constraints on the Converter Aisle operation However, when process disruptions invalidate the nominal schedule, it falls on operators to rely on operating protocols and experience to navigate the process operations and obey operating constraints as best as possible These considerations motivate the development and use of an optimal scheduling decision support system that is capable of timely process scheduling, while respecting operational constraints, to achieve a given objective The work presented formulates the operation scheduling as a mathematical optimization problem, where the relationships between the material flows, compositions, operating procedures, event timing and various constraints are captured, and the optimization objectives are quantified The problem is expressed in a standard mathematical form that is amenable to solution using commercial optimization software The project explores optimization opportunities in order to identify optimal scheduling configurations that are not realizable based on human intuition due to the complexity inherent in the process Copyright © 2013 IFAC.

Yang S.,McMaster University | Pelton R.,McMaster University | Abarca C.,McMaster University | Dai Z.,Vale Base Metals Technology Development | And 3 more authors.
International Journal of Mineral Processing | Year: 2013

Hydrophobic polystyrene nanoparticles (latex) were evaluated as replacement collectors for pentlandite flotation with a view to improving processing of ultramafic ores. Nanoparticles adsorb onto pentlandite particles, rendering them sufficiently hydrophobic to induce flotation. Polystyrene nanoparticles bearing surface imidazole groups specifically bind nickel ions and appear to improve selectivity (i.e. nickel grade), presumably because of chelation interactions between the imidazole groups and the pentlandite surface. Very high nanoparticle concentrations were required for high pentlandite recoveries under the high ionic strength conditions typically used in industry because the nanoparticles were coagulating. The path to commercially relevant nanoparticle flotation collectors involves increasing the colloidal stability of the nanoparticles while minimally impacting hydrophobicity. © 2013 Elsevier B.V.

Chen J.,McMaster University | Yu J.,McMaster University | Zhang Y.,Vale Base Metals Technology Development
Computers and Chemical Engineering | Year: 2014

Accurate measurement and prediction of pellet size distributions are critically important for material processing because they are essential for model predictive control, real-time optimization, planning, scheduling and decision support of material production. Mechanical sieving is one of the traditional methods for pellet size measurement in industrial practice but cannot be applied in real-time fashion. Alternately, multivariate image analysis based pellet sizing methods may acquire the size information non-intrusively and thus can be implemented for on-line measurement in industrial applications. Nevertheless, the conventional multivariate image analysis based pellet sizing methods cannot effectively deal with the pellet overlapping effects in the still images, which may lead to inaccurate and unreliable measurements of size distributions. In our study, two novel video analysis based pellet sizing methods are proposed for measuring the pellet size distributions without any off-line and intrusive tests. The videos of free-falling pellets are first taken and then the free-falling tracks of pellets in video frames are analyzed through the two video analysis based pellet sizing approaches. In the first video analysis method, the Sobel edge detection strategy is adopted to identify and isolate the free-falling tracks in order to estimate the diameters of the corresponding pellets. For the second video analysis approach, the filtered gray-scale video frames are scanned row by row and then the particle diameters are estimated and predicted through the built Gaussian process regression (GPR) models and a fine designed counting rule so as to eliminate the overlapping effects of nickel pellets along the horizontal and vertical directions. The utility of these two video analysis based pellet sizing methods is demonstrated through the measurement and estimation of free-falling nickel pellets in two test videos. © 2014 Elsevier Ltd.

Dong J.,Vale Base Metals Technology Development | Xu M.,Vale Base Metals Technology Development
Water in Mineral Processing - Proceedings of the 1st International Symposium | Year: 2012

Diethylenetriamine (DETA) has been used as an effective pyrrhotite depressant at Vale's Clarabelle Mill for more than a decade. In the fall of 2004, DETA started showing up as copper-DETA complexes in the effluent of the waste water treatment plant. Sporadic monthly copper exceedances have been observed since. DETA is a strong chelating agent and forms stable complexes with heavy metal ions (Cu 2+ and Ni 2+), leading to an ineffective removal of the DETA-metal complexes by conventional lime precipitation method. In the future, more challenging ores will be processed and will require more DETA to be added in order to achieve the grade/recovery target. To avoid the exceedances of heavy metals in effluent due to DETAmetal complexation, effective mitigation strategies are being developed to reduce DETA level in the tailings water. These strategies include: (1) maximizing adsorption of DETA onto pyrrhotite and rock tailings while minimizing desorption during processing and disposal of tailings, (2) adding natural zeolite as extra sorbents to capture additional free or complexed DETA in the tailings water if necessary, and (3) finding DETA replacements as pyrrhotite depressants. In this paper, DETA adsorption and desorption properties are studied on pyrrhotite and rock tailings, natural zeolite and the mixture.

Xu M.,Vale Base Metals Technology Development
Separation Technologies for Minerals, Coal, and Earth Resources | Year: 2012

Over the years, a comprehensive procedure has been established for ore evaluation and flowsheet development at Vale Base Metals Technology Development. When an ore sample arrives from a mine with an existing concentrator, the ore is subject to a set of standardized tests following a known flowsheet. This is termed ore evaluation. When an ore sample comes from an exploration project, the ore is subject to testwork that starts from simple batch tests to complex flowsheet tests. This is termed flowsheet development, which consists of nine steps that generally proceed in sequence: sample selection/ore preparation, grinding time determination, mineralogy analysis using Mineral Liberation Analyzer, incremental rougher flotation, staged rougher and scavenger flotation, batch full circuit simulation test, spreadsheet calculations, miniplant testing (20-50 kg/h), and pilot plant testing (>100 kg/h). This paper describes these steps and discusses the best practices for reliable and accurate assessment of ore separability.

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