Search Documents

By A. L. Mular

This paper provides a worthwhile contribution to the knowledge needed for calculating and using mathematical models of grinding circuits. The computer search algorithm proposed should remove much of the guesswork as well as reduce computer processing costs and improve the accuracy of estimated parameter values for grinding mill models.

Jan 1, 1970

By R. S. Boorman, H. G. Ansell

"Poor separation of lead from a copper concentrate of a major base metal producer was thought to have resulted from copper (0.2-0.4%) in the galena which caused it to float with chalcopyrite. No inclusions of copper mineral were detected which could account for the flotation of galena. The tendency for copper-bearing galena to float with chalcopyrite was confirmed by Hallimond-tube experiments in which the floatability of copper-doped synthetic galena (0.1-0.4% Cu) was approximately four times as high as copper-free galena. The difference in the cell edge (5.9338 ± 0.0003 A, Cudoped galena; 5.9361 ± 0.0002 A, Cu-free galena) indicated that the copper was lattice-bound and did not occur as submicroscopic mineral inclusions."

Jan 1, 1973

By A. Sutherland Brown

"The Red Rose Mine is in the Rocher Deboule Range, 8 miles south of Hazelton. The mill camp (elevation 4,000 feet) is on Red Rose Creek, 11 miles by road from Skeena Crossing. The mine camp is one mile northeast and 1,600 feet above the mill camp on a spur of Red Rose Peak.The Red Rose mine was described in the Jubilee Volume, Structural Geology of Canadian Ore Deposits (Davis, pp. 129-131), but regional geology and mine development have progressed to a stage at which a more complete description is possible.The property was first located in 1912, and for the next 7 years was prospected actively for gold and copper on the southern extension of the Red Rose shear. Scheelite was first discovered in the vein in the northern part of the shear in 1923. The Consolidated Mining and Smelting Company of Canada, Limited optioned the property in 1939, and after a drilling program in 1940 the present mine development was initiated in the vein in the northern part of the shear. A 75-ton-per-day mill started operating early in 1942 and continued until 1943. The property was inactive until 195 l, when Western Tungsten Copper Mines Limited leased the property from The Consolidated Mining and Smelting Company of Canada, Limited. A mill, which later was enlarged to 140 tons per day, started operations at the end of 1951. The mine and mill were closed in December, 1954.The mine has twelve levels and sub1evels, and most of the workings are in the plane of the vein (see Figure 2a). The level interval is not constant, but between the lower four levels is 87 feet (100 feet in the plane of the vein). Access is provided by four adits; the 800 (elevation 5,659 feet), 600 (5,920 feet), 300 (6, 133 feet) and 200 levels (6,237 feet). The 600 level is the main haulage, and from it the ore is transported to the mill by aerial tram. From this level an inclined shaft extends in the vein to the lowest level (I, 100)."

Jan 1, 1949

By F. L. Wu

Based on the analysis of a sealed coal mine resulting from a fire-triggered explosion, limitations were discovered in the re-entry procedures used to reduce the size of the sealed area that were being applied during the process of re-opening the mine. The analysis of two re-opening plans in a mine using mechanical ventilation showed that the estimation of the degree of damage of two air doors close to the working face with the fire was key to the identification of the optimum mine recovery plan. The operation points of airflow and air pressure of the main fan under either the doors? damaged or intact conditions can be estimated through the use of a ventilation network simulation program. Starting the main fan for a short time period and measuring its operation points of airflow and air pressure allowed their comparison with the simulated values. This procedure provided a reasonable estimation of the degree of damage of the ventilation structures and more confidence in choosing a recovery plan. Through this process, it was possible to conclude that the two doors were still intact. Consequently, the final plan of installing a new main fan in the main decline, sealing the initial upcast shaft and unsealing the auxiliary downcast shaft, was proven to be reasonable at the mine site.

Aug 1, 2013

By D. Gaboury

Most hydrothermal gold deposits contain quartz with fluid inclusions that record composition and temperature of the mineralizing event. Quartz has strong chemical and mechanical resistances to weathering and abrasion. Hence, quartz fragments occurring on weathered surfaces or in till cover have the potential to be used for gold exploration as far as we know what is the signification of the volatile content of the fluid inclusions for gold mineralization. In this perspective, fluid inclusions were analyzed in pure quartz by solid-probe mass spectrometry from gold deposits hosted in the Archean Abitibi (Canada) and Paleoproterozoic Birimian (Western Africa) belts. This approach provides the relative abundance of volatiles from families of fluid inclusions decrepitating at specific temperatures (Td). Fluids in gold deposits are aqueous-dominated with CO2 and minor H2S in accordance with their fundamental role as gold-ligands (H2S) and for pH-buffering (CO2) of the gold-bisulfide solubility. However, there is no correlation between CO2 and H2S contents of fluid inclusions with the gold grade of the samples. This suggests that trapped fluids represent a marginal portion of the fluid history recorded by the veins. However, in barren quartz veins away from known mineralization CO2 or H2S are commonly absent. Wide ranges in H2O Td from 250 to 450°C and CO2-H2O Td offsets are common, indicating phase separation. The content of other volatiles seems to be more dependent on the geological setting. Helium content may suggest proximity to a crustal-rooted fault, a critical parameter for gold mineralization. Methane and especially C2H6 appear to be indicative of fluid buffering by organic-rich material such as graphitic-shale. These rocks may provide an important primary gold reservoir from sedimentary metal-rich pyrite. Nitrogen-bearing fluids may be related to a magmatic component but can also be derived from organic-rich sedimentary rocks. For gold exploration, quartz containing CO2- H2S-bearing fluid inclusions and having H2O-CO2-Td offsets within 250 - 450°C has strong vectoring potential.

Jan 1, 2011

In the present work, the effect of pH, non-ionic polyacrylamide flocculant and anionic polyphosphate on rheology and settling behaviour of colloidal TiO2 suspensions (15 ? 50 wt% solid) is investigated. Maximum particle aggregation, reflecting in the highest suspension settling rate and maximum shear yield stress was achieved at pH 7.2, the isoelectric point (iep), consistent with DLVO expectation. However, the maximum aggregation condition at the iep also resulted in the poorest suspension consolidation behaviour. Significantly enhanced consolidation was achieved for a more dispersed suspension at pH values away from the iep but at reduced settling rate. Thus, when pH alone is used to control conditions which facilitate strong interparticle attraction, a high settling behaviour which is not conducive to compact consolidation results. Improved suspension consolidation may be achieved at the iep via anionic polyphosphate addition which leads to attenuation of the strongly attractive van der Waals forces and emergence of "soft" repulsion due to weak inter-particle electro-steric forces. The weak repulsion act to lubricate particles involved in the hydrodynamic interactions which controls the compressibility of the sediment bed, allowing a compact consolidation of solids to be obtained. Alternatively, non-ionic polyacrylamide homo-polymer (Magnafloc 333) was fairly effective in flocculating titanium dioxide suspensions leading to high settling rate and acceptable pulp consolidation at the iep.

Jan 1, 2006

By D. M. Maijer, S. L. Cockcroft, A. B. Phillion, P. Fan, C. Reilly, H. Khadivinassab

A combined experimental / numerical approach is proposed to investigate the bulk transfer of solute due to liquid metal feeding during shape casting of aluminum alloy A356 (Al-7Si-0.3Mg). A dumbbell-shaped experimental casting geometry has been developed, which promotes solute redistribution due to liquid metal feeding. The redistribution of solute in trial castings is evaluated based on the area fraction of eutectic phases. In the numerical model, silicon species segregation during solidification are calculated assuming the Scheil approximation, and are coupled with macro-scale solute transport due to Darcy flow in the mushy zone and feeding flow. The model has been implemented within the commercial CFD software, FLUENT, which simultaneously solves the thermal, fluid flow fields and species segregation on the macro-scale. The experimental and numerical results are compared and contrasted to examine the effects of liquid metal feeding in this casting.

Jan 1, 2014

By Ning Zhang, Yan Chen, Qikang Yi, Linjian Ma, Guoan Wang

Laboratory tests were performed to explore the effects of frequency on the deformation property of rock salt subjected to cyclic loading under confining stress condition. A two-stage (transient and steady) evolution law of axial cumulative strain was obtained through cyclic stress-strain curves complied from the loci of minimum load of each cycle. The unloading modulus decreases with loading cycles/time as a negative exponential function. The damage of rock salt under cyclic loading is reflected by the degradation of elastic modulus. A unified damage evolution equation considering the effects of frequency and time was established based on the experimental results. A new creep damage model for rock salt was proposed by introducing the non-stationary modular components in Burgers creep equation according to the Lemaitre equivalent strain theory. Comparative study indicates that the new model can accurately describe the creep deformation and damage evolution of rock salt under different loading frequencies. This paper provides a more reasonable model and relevant mechanical parameters for the stability analysis of compressed-air storage cavern in the injection and withdrawal durations.

Jan 1, 2015

By G. Girard, A. Larouche, J. Colbert, G. Doyer

"The Direct Chill (DC) casting process uses water to extract heat from molten aluminium and helps to control the solidification process. Many factors such as the water flowrate, water distribution around the mould and water impingement angle have significant impacts on the solidification process. It has been noted that the chemistry variation of the cooling water is also an important factor that has a major impact on the presence of defects on the ingot. A significant change in the water quality can produce defects on the ingots such as cracks, bleedouts, or runouts. Understanding the impact of water quality variation on ingots is therefore essential to ensure good ingot production and reduce defects. This paper aims at describing a new approach to follow the variations of process water quality over time. It is an original and innovative method, which is still under progress. A water quality and stability index (WQSI) is under development to evaluate changes in the water composition based on water physico-chemical parameters. The index is calculated by comparing each of the actual parameters with historical values previously modeled by a statistical law. It is a dimensionless number having an adjustable weight factor for each parameter. The positive or negative contribution of each parameter, with respect to the water cooling capacity, is taken into account to calculate the WQSI. The current selection of parameters is based on knowledge from the literature as well as on empirical experience. When the developed tool will be mature, it could be used to track water variations upon time and anticipate problems, enabling proactive actions to ensure good ingot production.INTRODUCTIONFor many years, the impact of water chemistry on heat transfer, during DC casting, has been of great interest in the aluminum industry. Several papers have been published to demonstrate the correlation between water chemistry and heat transfer (Yu, 1985), (Gildemeister, 2014). Although numerous studies do present the effects of water parameters (i. e. hardness, conductivity, oil, and grease…) on cooling capacity under controlled experimental conditions, they do not reflect the strong interactions between the parameters and variations present in a casting center. Wells and Cockcroft also demonstrated that laboratory based studies are not fully representative of real heat transfer in an industrial casthouse, there are too many factors involved (Wells, Li, & Cockcroft, 2001). In this context, it becomes very difficult to obtain a quantifiable relationship between the capacity of water to cool the ingot and ultimately the performance of the cast."

Jan 1, 2016

By B. S. Kim, Y. D. Kim, T. S. Kim, T. B. Kim, H. J. Chae

"The Nd-Fe-B scrap was placed in Fe crucible with pure Mg in an Ar atmosphere, and the scraps were melted using an induction heating method. The effects of experimental parameters such as melting temperature (range of 993K to 1073K) and holding time (15min-600min) on the ability of extraction were investigated. The microstructure and diffusion layers were analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), and the constituent phases were characterized using XRay Diffraction (XRD). Diffusion of Nd through the Nd-Fe-B scrap into liquid Mg was described, and the diffusion coefficient of Nd in liquid Mg was estimated.INTRODUCTIONNd-Fe-B magnets are usually produced either from comminuted melt-spun ribbons as bonded magnets or hot pressed bulk magnets, or by sintering in conjunction with prior green compaction in an applied magnetic field (Sagawa et al., 1984). These magnets have been widely used for various electromechanical and electronic devices such as voice coil motors (VCMs) and magnetic resonance imaging (MRI) (Samardzija et al., 2012; Matsuura et al., 2006). The production of the Nd-Fe-B magnets is increasing by about 20% per year because of their excellent magnetic properties. However, the expansion of Nd-Fe-B magnet market induced a concern for the scarcity of Nd at the aspect of natural resource. Therefore, the development of an effective recycling process for Nd-Fe-B magnet scraps is an extremely important issue from the viewpoint of resource and energy conservation. Several recycling processes for the Nd-Fe-B magnets have been proposed (Uda et al., 2002; Lyman et al., 1993]. It has been reported that the best separation of rare-earths from the Nd-Fe-B magnets is obtained by sulfuric acid dissolution followed by precipitation of recyclable rare-earth salts. However, this process can make a large amount of waste water including dangerous solutions. Recently, (Xu et al., 2000) have reported a technique to extract Nd from 18Nd-72.4Fe-0.9B-1.82Pr-5.3Dy (wt.%) magnet scrap by using liquid metal extraction (LME) processing. However, these techniques seemed to be difficult for application, because the scraps consist of an infinitesimal amount of other minor elements (Pr, Dy, Cu, Al and Tb), and these minor elements can make a new intermetallic compounds with Mg. Also, some oxides or the plated Ni metal can be preventable to reaction between solid-liquid (S/L) interfaces. For these reasons, the substantive reaction mechanism between Mg and Nd-Fe-B scrap is not clear. In this study, the simple composition of 33Nd-66Fe-1B (wt.%) magnet scraps were prepared using an induction melting process. The effects of the experimental parameter on the diffusion properties between Mg and scraps were investigated to determine whether these methods could be used in industrial application in a liquid metal extraction (LME) process."

Jan 1, 2012

By V. S. Gischig, G. Preisig

Hydraulic stimulation of deep reservoirs is an essential procedure for developing engineered/enhanced geothermal systems (EGS), but also in other Geo-energy contexts. The goal is enhancing permeability to such a degree that fluid flow rates within the reservoir are sufficiently high for an economically productive reservoir. Two fracture stimulation mechanisms are distinguished that may occur concurrently during the hydraulic treatment: 1) During hydro-fracturing (HF) new tensile fractures are propagated from the borehole by means of a fluid pressure overcoming the minimal principle stress d3 plus the tensile strength T0 of intact rock. In case of a pre-existing fracture oriented normal to d 3 , the fracture can be opened by exceeding d 3 only. Fluid injection is performed via small packed intervals for creating a stack of hydraulic fractures. 2) During hydro-shearing (HS), over-pressure induces slip along pre-existing fractures that are favourably oriented in the stress field for reactivation in shear. Such stimulation is usually performed in a large packed interval or in an open borehole. Which mechanism occurs predominantly during stimulation depends on the rock mass structure and in-situ stress field, but also on the orientation of discontinuities intersecting the open-hole section and thus being pressurized. Both mechanisms also differ in how they affect fracture permeability. While permeability gained by HS is mostly irreversible due to rearrangement of asperity contacts accompanied with shear dilation, permeability enhanced during HF reduces nearly reversible after pressurization unless proppant is used to ensure permanent apertures. In this contribution, we critically discuss the pros and cons of both mechanisms regarding efficiency of enhancing permeability and the associated hazard of induced earthquakes based on literature review and numerical modelling. We review literature that reports on how much permeability required for productive EGS reservoirs and how much permanent permeability can be gained by stimulation. We also compile information regarding the degree of seismicity induced during HFor HS-dominated stimulation procedures, together with conceptual studies that reveal characteristics of seismicity associated with the two mechanisms. Many observations and models indicate that HF may have a higher tendency of being aseismic, while felt seismic events are usually associated with HS. Further, we present a hydro-mechanically coupled fracture flow model that investigates, if and to what degree the stimulation strategy can be designed such that one of the two mechanisms is evoked and dominates over the other. It shows that HS may dominate in presence of larger persistent fractures nearly optimallyoriented in the stress field, even if HF is attempted in short packed intervals. The model further demonstrates that stress transfer during HS promotes the development of permeability across an anisotropic layer of the stimulated rock instead of a large volume. Hence, the study sheds light onto the feasibility of creating productive EGS reservoirs in crystalline rock at several kilometres depths.

Jan 1, 2015

By John A. Hudson, Xia-Ting Feng, Joseph S. Y. Wang

Evolution over decades and progress over last five years have been made in many topics of interests to rock mechanics, geosciences, physics, and multi-disciplinary interactions in underground research laboratories and development facilities, as well as in underground energy recoveries and environmental assessments. Rock mechanics and geotechnical engineering advances are associated with quantifications of disturbed/damaged zones and rock alternation and bursting processes and creation of underground spaces and accesses associated with deepening of shafts and lengthening of tunnels. Geophysics and earth sciences advances are associated with continuing collections of seismic, electromagnetic, and gravitational data and conducting various thermal, hydrological, mechanical, chemical, and biological investigations, both separately, simultaneously, and in different coupled ways. Astroparticle and underground physics advances are associated with many long term experiments to detect rare events and needs for increasing larger and deeper halls to accommodate next generation detectors, shielings, and isolations. There are also increasing interesting in underground settings to explore multidisciplinary and inter-disciplinary sciences and technologies. Energy and environmental sciences and assessments have evolved from traditional oil and gas focuses to recent activities associated with green resources and alternative recovery/disposal strategies. The evolution and progress of these interdependent and related fields are discussed in this quadrennial Congress.

Jan 1, 2015

By P. Mpofu

In this work, the modification of interfacial chemistry of colloidally stable kaolinite clay dispersion has been carried out to improve its flocculation performance and dewatering behaviour. Synergistic action between dispersion pH, hydrolyzable metal ion and high molecular weight polymeric flocculant structure type (anionic polyacrylamide-acrylate copolymer (PAM) and non-ionic polyethylene oxide (PEO)) was found to play a pivotal role in inter-particle bridging, the enhancement of the settling rate and extent of consolidation of the pulps. Flocculation with PEO led to higher settlings rates in acidic than alkaline pH, whilst for PAM, the maximum dewatering rate was achieved in the neutral pH range 6 - 7.5. Upon shear, the PEO flocculated pulps showed dramatic improvement in consolidation to 40 wt%, the extent of which was greater at lower than high pH values. For PAM-based pulps were however, not shear-responsive, lower sediment solid contents of 15 - 23 wt% was observed between pH 3 and 11. Hydrolysable metal ions, Mn(II) and Ca(II), used respectively at pH 7.5 and 10.5 in conjunction with PAM and PEO, significantly enhanced the settling rates and consolidation of the pulps. The findings exemplify the strong links existing between pH-mediated particle surface chemistry. polymer structure-conformation, inter-particle bridging and dewaterability of kaolinite dispersions.

Jan 1, 2004

By D. M. Muir

The mineralogy of residues formed during the pressure acid leaching of arid region nickel laterite ore varies according to the salinity of the process water, alkali cation additives and the overall acid loading. In fresh water, hematite is the main iron-bearing leach residue component, together with amorphous silica and hydronium or sodium alunite/jarosite [(H3O,Na)(Fe,Al)3(SO4)2(OH)6]. As the process water salinity increases, or as NH4+ or K salts are added, alunite/jarosite is the kinetically favoured iron-bearing phase accompanied by an increase in acid consumption. The alunite/jarosite appears as two XRD distinct phases with different Fe:Al molar ratios. In weakly saline water, iron-rich alunite/jarosite slowly transforms to hematite and an aluminium-rich alunite/jarosite together with the release of acid. The addition of potassium salts forms a more stable alunite/jarosite whilst the addition of ammonium salts leads to greater transformation of alunite/jarosite at 250°C. Weakly saline process water gives enhanced nickel recoveries, whilst strongly saline process water gives lower nickel recoveries but higher soluble iron because of chloro-complexation. SEM and microprobe analysis shows very little nickel is associated with the alunite/jarosite and hematite phases. Nickel losses to the residues are attributed to adsorption on amorphous silica and to a lesser extent on alunite/jarosite.

Jan 1, 2006

?Hydrothermal breccias-genetic models ?Deep drilling-underground potential ?Deposit variety-test new ideas Exploration Summary

May 1, 2006

By K. Buxmann

Climate change is a subject of growing concern. Based on the International Energy Agency, about 19% of man made greenhouse gas emissions globally are generated by the transport sector. This paper will focus on the environmental aspects of the light-weighting in transport and the resulting savings of fuel and electricity. Aluminium is an option for lightweight applications in transport, with very high benefits not only in the use stage, but also in the stage of vehicle recycling. Life cycle assessment is used to quantify the relative benefits of light-weighting specific components of cars, commercial road vehicles, buses, ships and trains. A vehicle consists of many components, which are produced by different processes and undergo different types of end-of-life operations. This document does not intend to compare a generic aluminium vehicle with a generic "heavy materials" vehicle. It rather tries to use a pragmatic approach based on specific examples of components where aluminium is used and can be used in the design of new vehicles, also taking into account future developments. The case studies in this paper are based on real cases where aluminium was used. For each component, sensitivity analyses are applied to see the impact of specific parameters such as the end-of-life recycling rate and the use stage driving distance. Significant greenhouse gas savings by the use of aluminium are demonstrated for cars and even higher ones for trucks, buses, trains and ships. In addition, the total potential benefits of light-weighting with aluminium are shown on the global level.

Jan 1, 2007

By J. M. Hong, H. K. Zheng, R. Hu, C. B. Zhou

The Jinping-I double curvature arch dam, located in the middle reach of the Yalong River and with a maximum height of 305 m, is the world highest dam of the same type that has been completed. Since the second and third periods of the reservoir impounding, after which the reservoir water level was raised by about 200 m, a significant amount of leakage was observed out of the drainage holes deployed in the lowest drainage tunnel at the left-bank abutment at EL. 1595 m, with a pressure of 0.3 MPa at one typical hole when it was blocked. In this study, a number of analyses including water quality analysis, digital borehole imaging, tunnel geological mapping and in-situ groundwater monitoring were performed to investigate the source of leaking, the leakage passages and the performance of the grouting curtains. An inverse modeling procedure combining the orthogonal design, finite element forward modeling of the transient seepage flow, artificial neural network and genetic algorithm was invoked to further evaluate the permeability of the foundation rocks whose permeability was underestimated in design, using the in-situ measurements of flow rate and piezometric head. The geological structures that lead to the leakage were identified and the seepage flow behaviors in the dam foundation and the left bank abutment were assessed. Given the connectivity nature of the sub-vertically oriented fractures that induce the leakage event, it is found that some of the drainage holes with relative larger amount of discharge could be closed or blocked for reducing the amount of leakage without remarkably increasing the pore water pressure in the foundation rocks.

Jan 1, 2015

By G. R. Cope, J. S. Getsinger, K. D. Lund, T. Neale

"Mineral exploration in the Sicker Group, a belt of Paleozoic volcano-sedimentary rocks on Vancouver Island, has traditionally centred on auriferous polymetallic volcanogenic massive sulphide deposits such as those currently mined by Westmin Resources Ltd. near Buttle Lake. Recently, however, the focus of exploration in the Sicker Group has shifted toward targets of structurally controlled gold concentrations, with notable success. Major north and northwesterly-trending structural features such as the Cowichan-Horne Lake break (one of several regional high-angle thrust fault s active throughout a long period of geological time) and related fault systems have contributed to localization of gold mineralization.Using the extensive information database compiled by MPH Consulting Limited during numerous exploration projects in the Sicker Group, two cross sections through areas with significant gold occurrences southeast of Port Alberni are presented. The cross sections combine geological, geochemical and geophysical data in an attempt to emphasize the relationship between structural trends and gold mineralization. Examples from specific properties, including gold discoveries along the Mineral Creek fault zone, are used to illustrate this relationship."

Jan 1, 1990

By W. Zheng

Pipelines can develop stress corrosion cracks in either intergranular or transgranular form. Since the mid-1980s, numerous colonies of transgranular cracks have been found across Canada and many other countries in the world. While the intergranular form of cracking has been well studied in the past 40 years, the mechanisms governing SCC in near-neutral pH environment, i.e., the transgranular form of the cracking, are yet to be understood in greater depth. Over the past ten years or so, a large number of research publications have been available on this subject and this paper summarize our latest progress in understanding the mechanistic aspect of the problem. Better understanding of the role of mill scale surface and the steel metallurgy in crack initiation has been indicated in the recent literature. However, the initiation of SCC in the lab research still relies on loading conditions that are far more aggressive than those encountered in the field. Most crack growth studies in the past are also performed under very aggressive mechanical conditions, which could have prevented the observation of environment effects. However, more recent research at lower K or Delta K ranges seems to suggest a strong role of the environment. Naturally, modeling of growth should reflect the effect of the environment, steel metallurgy, and the changing mechanical properties of the pipe steel with time. For a specific steel in a given environment, the crack growth rates tended to increase with the strain rate, indicated either by the nominal applied loading frequency or by the calculated crack tip opening rate. Future research needs to address the issue of concurrent growth of multiple interacting cracks. More attention should also be given to concurrent initiation of multiple cracks in a colony, as failure is usually caused by a coalesced crack not by an individual crack. The effect of soil environment should not be limited to the chemistry of soil solution; other factors such as cathodic processes, the variation of environment with time and physical conditions of coatings should also be considered as part of the study.

Jan 1, 2005

By C. Liu

Zeta potentials and settling rates of an oil sands tailings sample taken from Syncrude Canada Ltd's Aurora Stacker Pilot Operation were studied. Two clay minerals, kaolinite and illite, were also studied since these are the major constituent minerals in the fine oil sands tailings. Process water, decanted water as well as distilled water were used. It was observed that the zeta potentials of the tailings solids showed maximum negative values in process water at pH 8-10, which coincides with the pH of commercial hot water bitumen extraction process. The settling rates of the tailings sample were very low, at 0.008 m/hr in decanted water and 0.04 m/hr in process water. The rates were increased to 1.0 m/hr in decanted water and 0.13 m/hr in process water at an addition of 50 g/t Ciba AF1235. Although the settling rate was higher the supernatant was cloudier in decanted water than in process water. Further increase in the dosages of Ciba AF1235 did not increase the settling rates in decanted water but gradually increased it in process water, reaching 0.46 m/hr at 100 g/t. The results indicated that lower concentrations of Ca2+ and Mg2 (in decanted water) benefited settling rates but did not benefit supernatant clarity. Test results also indicated that Ciba AF1235 caused selective flocculation of the tailings sample, since the top sediments had higher illite and lower quartz contents than the bottom sediments.

Jan 1, 2006