http://espace.library.uq.edu.au/ The University of Queensland en Fez http://blogs.law.harvard.edu/tech/rss http://espace.library.uq.edu.au/view/UQ:161504 2009-01-22T00:00:00Z Morrison, R. og Loveday, B. og Powell, M. S. og Djordjevic, N. og Cleary, P. http://espace.library.uq.edu.au/view/UQ:64585 The PFC3D (particle flow code) that models the movement and interaction of particles by the DEM techniques was employed to simulate the particle movement and to calculate the velocity and energy distribution of collision in two types of impact crusher: the Canica vertical shaft crusher and the BJD horizontal shaft swing hammer mill. The distribution of collision energies was then converted into a product size distribution for a particular ore type using JKMRC impact breakage test data. Experimental data of the Canica VSI crusher treating quarry and the BJD hammer mill treating coal were used to verify the DEM simulation results. Upon the DEM procedures being validated, a detailed simulation study was conducted to investigate the effects of the machine design and operational conditions on velocity and energy distributions of collision inside the milling chamber and on the particle breakage behaviour. (C) 2003 Elsevier Ltd. All rights reserved. 2007-08-14T00:00:00Z Djordjevic, N. og Shi, F. N. og Morrison, R. D. http://espace.library.uq.edu.au/view/UQ:188003 The operation of AG/SAG mills is sensitive to mill filling, therefore developing grindcurves to relate mill filling to performance indicators such as throughput, power draw, and product size can assist in achieving optimal mill operations. The throughput, power draw, and product size have been shown to peak at different mill filling levels. Establishing grindcurves can assist operators to decide on the best set point for operating their mill. Factors such as mill speed, mill inlet water, feed size distribution, and ore hardness all have an influence on the grindcurve, and form an integral part of the optimisation process. Test work has been conducted at a number of sites to develop grindcurves for different mills treating a range of ores. The results show great promise for use in optimising the operating set points for use in mill control. The methodology for developing grindcurves is described and the results from the case studies performed on fixed and variable speed mills are discussed. 2009-11-26T14:07:11Z Powell, M. S. og van der Westhuizen, A. P. og Mainza, A. N. http://espace.library.uq.edu.au/view/UQ:147580 2008-06-06T00:00:00Z Morrison, R. D. http://espace.library.uq.edu.au/view/UQ:265761 Flotation kinetics plays an essential role in developing a comprehensive understanding of the flotation theory providing pathways for describing flotation process through mathematical modelling. Classically, the description of flotation kinetics is characterised using a coefficient,named specific flotation rate constant (k). Simultaneously, it has been acknowledged that among the number of factors affecting flotation performance, the particle properties of the ore being processed are relevant. The physical-property-based modelling approach (PPBM) Links discrete specific rate constants to physical properties of the minera l particles, such as particle size and mineral Liberation. As a result of applying the PPBM a full set of specific rate constants is obtained. In order to establish which specific rate constants are needed for prediction, it is necessary to know their uncertainties and, then, to explore, if appropriate, the existence of redundancy in the data. This work aims to apply Positive Matrix Factorisation (PMF) to condense the information of flotation rate constant values obtained from physical-property-based size- by-liberation distribution for galena in the feed stream to a 40-L continuous flotation cell. PMF uses the uncertainties associated with the rate constant values to calculate the weights of residuals. The application of PMF with a rank 1 model fitted the matrix of rate constants so that residuals of the fit were comparable to assumed data uncertainties. The two vectors followed clear trends as functions of particle size and galena liberation that may constitute heuristic for predicting flotation performance. This will be confirmed with other case studies. A simple heuristic model of the rate constant matrix might consist of weighted averages of the kinetic rate constants by using the mass proportions associated. Comparison of such a heuristic model with PMF indicates that the two models are not identical, i.e., PMF distils different information to such a heuristic model. Hence, further analysis is required. 2012-01-23T00:00:00Z Sandoval-Zambrano, Gerson og Whiten, William J. og Gonzalo Montes-Atenas og Paatero, Pentti http://espace.library.uq.edu.au/view/UQ:163194 2009-02-05T00:00:00Z Morrison, R. D. og Gaylard, P. G. http://espace.library.uq.edu.au/view/UQ:3310 The original Mathews method for predicting stope stability has been extended and now contains 483 open stoping and caving case histories over a wide range of geotechnical conditions and stope dimensions. The mathematical framework upon which the Extended Mathews stability graph is based and the large database has facilitated examination of a number of outstanding issues surrounding the application of empirical stability graphs. This paper summarises how the framework of the Extended Mathews stability graph framework has been applied to quantify the effect of stress relaxation upon excavation stability, examine site-specifi c effects and highlight the poor correlation between stability graph parameters for narrow stope stability. Back-analysis of case studies where stope surfaces were relaxed has enabled the effect of stress relaxation upon excavation stability to be quantified and bounded. Detailed statistical analyses have demonstrated that a reliable stable-failure boundary requires at least 150 case histories, of which a minimum of 10% should be unstable stope surfaces. Marginal site-specifi c effects were observed for the operating conditions captured within the database. Apparent site-specifi c effects noted in previous literature were found to be attributable to operating conditions inadequately represented in the database. Statistical analysis of overbreak from 115 narrow-vein case studies has demonstrated that operating conditions in narrow-vein mines differ suffi ciently to warrant changes in the model framework to account for undercutting of stope walls and drill and blast parameters. Backfi ll abutments were found to behave the same as solid rock abutments. 2006-05-02T12:50:32Z Stewart, Penny og Trueman, Robert http://espace.library.uq.edu.au/view/UQ:224321 The surface area of fragmentation, especially in the finer size fractions, is a useful property to characterise the mechanisms of rock breakage. In the past, researchers have made assumptions with regard to the shape of fragments in order to estimate surface area, such as that all fragments are the same shape or all fragments are spheres. Often these assumptions were developed with inappropriate measures and returned considerable variability and error for the calculation of surface area. This paper reports a model to estimate fragmentation surface area from sieve sized raw data and a density measurement, with experimental validation down to a size fraction of –45 + 38 μm in a range of rock types. After characterisation of particle shape, a range of fragment shapes was found to be in each size fraction. Nevertheless, in the √2 sieve series the average fragment mass, volume and the size fraction standard deviations could be predicted reasonably accurately. Ellipsoid geometry was used to describe particle shape. Using these parameters and the number of fragments (also predicted) in each sieve size the individual surface area of each fragment was simulated. 2010-12-13T00:00:00Z Michaux, Simon P. og Djordjevic, Nenad http://espace.library.uq.edu.au/view/UQ:278865 2012-08-13T09:46:14Z Tuazon, D. og Corder, G. D. og Powell, M. og Ziemski, M. http://espace.library.uq.edu.au/view/UQ:263205 In the mining industry, high-level commitments to adopt sustainability have been made at the corporate levels of mining companies, but there continue to be problems when attempts are made to adopt these high-level sustainability aspirations and translate them into appropriate targets and methods at the more-specific operational level. The integration of sustainability principles into day-to-day mineral processing operational decision-making processes has unique challenges that are not addressed adequately by current tools and methodologies. A proposed methodology to achieve integration of sustainability at the operational level will direct the systematic and rigorous identification and qualification of sustainability issues and opportunities in an operation. The methodology, starting from a sustainability point-of-view rather than an operational one, guides the identification of process issues (‘‘problems’’) and opportunities by examining the operation, unit-by-unit, similar to a HAZOP process. Each issue or opportunity is qualified according to its measurability, scopes of impact and consequences so that it may be understood fully and the correct engineering problems are formed. The methodology has been tested with two case studies at minerals processing operations. At one site, the methodology identified a dust issue which had considerable business risks (loss of valuable product) compared to conventional engineering analysis processes. The other site also benefited from using the methodology as an opportunity to improve the milling circuit between the semi-autogenous grinding (SAG) mill and flotation circuit was identified. The opportunity not only showed a potential to improve the operational efficiency of the units concerned, but also potential improvements in water and energy (both direct and embodied) efficiency. It was important to utilise the holistic approach of the methodology in the identification of opportunities at this site; the goals of the operation showed a strong coupling between water and energy issues which would be difficult to overcome using the operation’s current organisational model which deals with such issues separately of each other. 2011-12-08T15:10:33Z Tuazon, D. og Corder, G. og Powell, M. og Ziemski, M. http://espace.library.uq.edu.au/view/UQ:285845 2012-11-19T13:30:28Z Bulelwa Ndlovu og Forbes, E. og Saeed Farrokhpay og Becker, M. og Deglon, D. og Bradshaw, Dee J. http://espace.library.uq.edu.au/view/UQ:161505 2009-01-22T00:00:00Z Condori, P. og Powell, M.S. http://espace.library.uq.edu.au/view/UQ:161742 Over 500 zircon grains separated from modern sediments in 10 drainages covering the Eastern Succession of the Mt Isa Inlier have been analysed for U - Pb ages, Hf isotopes, and trace elements, using in situ LAM-ICPMS techniques, to evaluate the efficacy of this approach in characterising large-scale crustal evolution. U - Pb age spectra are used to estimate the timing of terrane-scale events, primarily magmatic episodes; Hf isotopes provide information on the relative contributions of juvenile material and reworked older crust at each stage of crustal evolution; trace-element patterns of zircons are used to characterise original magma types. The integration of these data for individual zircon grains produces an event signature that provides more information than that gained from U - Pb dating alone. The data define four major stages of crustal evolution in the area: 2550 - 2330 Ma, 1950 - 1825 Ma, 1800 - 1600 Ma, and 1590 - 1420 Ma. Each stage, except the last, involved crustal extension, and ended with a period of crustal homogenisation, which is reflected in the isotopic composition of magmatic rocks generated by crustal reworking in the succeeding stage. Reworking of Neoarchaean crust contributed significantly to crustal magmatism throughout the Proterozoic history. A major input of juvenile mafic material around 1625 Ma (interpreted as the magmatic age of the Toole Creek Volcanics) is poorly represented in the database of conventional geochronology but is prominent in the detrital zircon record. The major late-stage granitic magmatism of the Williams and Naraku Batholiths (1520 - 1490 Ma) was generated almost entirely from older crust, with little juvenile input. The study demonstrates that sampling of carefully selected modern drainages and the analysis of statistically large numbers of detrital zircons can provide insights additional to those gained from conventional analysis of U - Pb and Sm - Nd systematics in selected rock samples. The integrated use of U - Pb age, Hf-isotope composition and trace-element patterns in detrital zircons is a powerful and relatively inexpensive tool for the analysis of terrane-scale crustal evolution, and for the correlation of terranes. 2009-01-27T10:41:44Z Griffin, W. L. og Belousova, E. A. og Walters, S. G. og O'Reilly, S. Y. http://espace.library.uq.edu.au/view/UQ:261827 2011-11-20T04:50:36Z Albijanic, Boris og Amini, Eiman og Wightman, Elaine og Ozdemir, Orhan og Nguyen, Anh V. og Bradshaw, Dee J. http://espace.library.uq.edu.au/view/UQ:193777 2010-01-25T00:00:00Z Morar, S. H. og Hatfield, D. P. og Barbian, N. og Bradshaw, D. J. og Cilliers, J. J. og Triffett, B. http://espace.library.uq.edu.au/view/UQ:131537 2008-03-04T00:00:00Z Narasimha, M. og Brennan, M. S. og Holtham, P. N. http://espace.library.uq.edu.au/view/UQ:288022 2012-12-30T00:54:06Z Long, Graham og Peng, Yongjun og Bradshaw, Dee http://espace.library.uq.edu.au/view/UQ:275798 2012-06-18T13:15:54Z Long, Graham og Yongjun Peng og Bradshaw, Dee J. http://espace.library.uq.edu.au/view/UQ:78876 A critical assessment is presented for the existing fluid flow models used for dense medium cyclones (DMCs) and hydrocyclones. As the present discussion indicates, the understanding of dense medium cyclone flow is still far from the complete. However, its similarity to the hydrocyclone provides a basis for improved understanding of fluid flow in DMCs. The complexity of fluid flow in DMCs is basically due to the existence of medium as well as the dominance of turbulent particle size and density effects on separation. Both the theoretical and experimental analysis is done with respect to two-phase motions and solid phase flow in hydrocyclones or DMCs. A detailed discussion is presented on the empirical, semiempirical, and the numerical models based upon both the vorticity-stream function approach and Navier-Stokes equations in their primitive variables and in cylindrical coordinates available in literature. The existing equations describing turbulence and multiphase flows in cyclone are also critically reviewed. 2007-08-15T00:00:00Z Narasimha, Mangadoddy og Brennan, Matthew S. og Holtham, Peter N. http://espace.library.uq.edu.au/view/UQ:245978 A review of past and present published works examining the interaction of polymeric dispersants with titania pigment particles is presented. Titania is the most important white pigments currently used in the world and its suspension properties are very important for consumer industries such as paints, papermaking and plastics; if aggregates are present, the end-use properties including gloss, opacity and storage stability will be highly affected. As polymeric dispersants are generally used to disperse titania pigment particles, it is very important to understand the interactions between the pigment particles and polymeric dispersants of varying functionality. Although, in principle, the adsorption of polymers onto titania pigment and influences on pigment dispersion and stabilisation are fairly known, it is nevertheless hardly possible to forecast the behaviour of a given polymeric dispersant in advance, unless to have a broad knowledge of the interaction occurring between pigment and dispersants and effect of dispersant structure upon adsorption. While only titania pigment is discussed, the issues raised may also apply to other mineral oxides such as alumina or zirconia. 2011-08-22T13:21:27Z Farrokhpay, Saeed http://espace.library.uq.edu.au/view/UQ:253848 2011-10-03T08:30:38Z Miller, J. D. og Li, J. og Davidz, J. C. og Vos, F. http://espace.library.uq.edu.au/view/UQ:103541 2007-08-23T00:00:00Z Mainza, N og Powell, Malcolm og Morrison, R. D. http://espace.library.uq.edu.au/view/UQ:103329 2007-08-23T21:30:39Z Johnson, N. W. http://espace.library.uq.edu.au/view/UQ:269333 2012-03-08T00:00:00Z Bueno, Marcos og Lane, G. http://espace.library.uq.edu.au/view/UQ:142829 2008-06-10T00:00:00Z Tucker, J. D. http://espace.library.uq.edu.au/view/UQ:224971 2010-12-16T00:00:00Z Tabatabaei, Reyhaneh og Vianna, Sergio M.S. http://espace.library.uq.edu.au/view/UQ:205485 2010-05-23T00:00:00Z Whiten, Bill http://espace.library.uq.edu.au/view/UQ:224167 Vascular anastomoses constitute a main factor in poor graft performance due to mismatches in distensibility between the host artery and the graft. This work aims at computational fluid-structure investigations of proximal and distal anastomoses of vein grafts and synthetic grafts. Finite element and finite volume models were developed and coupled with a user-defined algorithm. Emphasis was placed on the simplicity of the coupling algorithm. An artery and vein graft showed a larger dilation mismatch than an artery and synthetic graft. The vein graft distended nearly twice as much as the artery while the synthetic graft displayed only approximately half the arterial dilation. For the vein graft, luminal mismatching was aggravated by development of an anastomotic pseudo-stenosis. While this study focused on end-to-end anastomoses as a vehicle for developing the coupling algorithm, it may serve as useful point of departure for further investigations such as other anastomotic configurations, refined modelling of sutures and fully transient behaviour. 2010-12-10T11:49:20Z Schiller, N. K. og Franz, T. og Weerasekara, N. S. og Zilla, P. og Reddy, B. D. http://espace.library.uq.edu.au/view/UQ:192304 Polymeric depressants (modified guars and carboxy methyl celluloses) are used in the flotation of platinum-bearing ores in South Africa to reduce the recovery of naturally floatable gangue minerals such as talc. These polymers have always been considered to weakly adsorb (via physical adsorption forces) on gangue minerals and consequently the adsorption is considered to be an equilibrium process and therefore reversible. Micro-scale flotation tests on a talc sample showed that the floatability of the talc could be completely reduced by the adsorption of these polysaccharides but could be restored, depending on the conditions, by washing with water showing that the adsorption is reversible in a pure water system. Copyright © 2005 Elsevier Ltd All rights reserved. 2010-01-13T08:57:12Z Cawood, S. R. og Harris, P. J. og Bradshaw, D. J. http://espace.library.uq.edu.au/view/UQ:167383 2009-03-12T00:00:00Z Pokrajcic, Z. og Morrison, R. D. http://espace.library.uq.edu.au/view/UQ:131937 2008-03-10T00:00:00Z Musa, F. og Morrison, R. D. http://espace.library.uq.edu.au/view/UQ:99612 2007-08-24T00:00:00Z Dimitrakopoulos, R. og Fonseca, M. http://espace.library.uq.edu.au/view/UQ:165737 2009-03-03T00:00:00Z Vizcarra, T. og Wightman, E.M. http://espace.library.uq.edu.au/view/UQ:265763 2012-01-23T00:00:00Z Sandoval-Zambrano, Gerson og Montes-Atenas, Gonzalo http://espace.library.uq.edu.au/view/UQ:193785 2010-01-25T00:00:00Z Morar, S. og Bradshaw, D. og Harris, M. http://espace.library.uq.edu.au/view/UQ:98457 2007-08-24T00:00:00Z Gay, S. L. http://espace.library.uq.edu.au/view/UQ:224973 Froth stability is generally acknowledged as a key factor in achieving the required selectivity in froth flotation processes. Many techniques have been developed to assess froth stability, such as maximum froth height, the rate of froth decay (froth half-life time) and water recovery. The present work aims to assess the consistency between these different measurements. Experimental work was undertaken in both two-phase (liquid/gas) and three-phase (solids/liquid/ gas) systems. The two-phase systems were made up using two commercial frothers with different molecular structures (one a glycol and the other an alcohol type frother) at a range of concentrations. Fine hydrophilic solids and coarse hydrophobic solids, at different per cent solids, were added to make up the three-phase systems A foaming column was used to measure the maximum froth height and the rate of froth decay, while laboratory batch flotation tests were conducted to measure the water recovery. All three measures of froth stability suggested that froth stability increased with increasing frother concentration, but did not always provide a consistent interpretation on the effects of solid loading on froth stability. The results also indicated that the hydrophilic (non-floating or entrained) particles were the main component in the feed promoting stability in the froth phase, in these systems. 2010-12-16T00:00:00Z Tang, Dong og Wightman, Elaine M. og Franzidis, J-P. og Gonzalo Montes-Atenas http://espace.library.uq.edu.au/view/UQ:225180 2010-12-19T00:00:00Z Welsby, S. D. D. og Vianna, S. M. S. M. og Franzidis, J.-P. http://espace.library.uq.edu.au/view/UQ:161639 2009-01-23T00:00:00Z Powell, M. og Chandramohan, R. http://espace.library.uq.edu.au/view/UQ:161644 2009-01-23T13:02:51Z McBride, A. T. og Powell, Malcolm S. http://espace.library.uq.edu.au/view/UQ:103542 2007-08-23T00:00:00Z Shi, F. N. og Lambert, S. og Daniel, M. J. http://espace.library.uq.edu.au/view/UQ:98456 2007-08-24T00:00:00Z Runge, K. C. og Franzidis, J. og Manlapig, E. http://espace.library.uq.edu.au/view/UQ:263199 2011-12-08T00:00:00Z Tabosa, Erico og Runge, K. og Crosbie, R. og McMaster, J. og Holtham, Peter N. http://espace.library.uq.edu.au/view/UQ:147613 2008-06-06T00:00:00Z Rong, R. X. og Fulton, T. og Murdoch, S. http://espace.library.uq.edu.au/view/UQ:64830 Blasting has been the most frequently used method for rock breakage since black powder was first used to fragment rocks, more than two hundred years ago. This paper is an attempt to reassess standard design techniques used in blasting by providing an alternative approach to blast design. The new approach has been termed asymmetric blasting. Based on providing real time rock recognition through the capacity of measurement while drilling (MWD) techniques, asymmetric blasting is an approach to deal with rock properties as they occur in nature, i.e., randomly and asymmetrically spatially distributed. It is well accepted that performance of basic mining operations, such as excavation and crushing rely on a broken rock mass which has been pre conditioned by the blast. By pre-conditioned we mean well fragmented, sufficiently loose and with adequate muckpile profile. These muckpile characteristics affect loading and hauling [1]. The influence of blasting does not end there. Under the Mine to Mill paradigm, blasting has a significant leverage on downstream operations such as crushing and milling. There is a body of evidence that blasting affects mineral liberation [2]. Thus, the importance of blasting has increased from simply fragmenting and loosing the rock mass, to a broader role that encompasses many aspects of mining, which affects the cost of the end product. A new approach is proposed in this paper which facilitates this trend 'to treat non-homogeneous media (rock mass) in a non-homogeneous manner (an asymmetrical pattern) in order to achieve an optimal result (in terms of muckpile size distribution).' It is postulated there are no logical reasons (besides the current lack of means to infer rock mass properties in the blind zones of the bench and onsite precedents) for drilling a regular blast pattern over a rock mass that is inherently heterogeneous. Real and theoretical examples of such a method are presented. 2007-08-14T00:00:00Z Segui, J. L. B. http://espace.library.uq.edu.au/view/UQ:131942 2008-03-10T00:00:00Z Lamberg, P. og Vianna, S. M. S. http://espace.library.uq.edu.au/view/UQ:272600 2012-04-12T00:00:00Z Resabal, Vannie og Anacleto, N. http://espace.library.uq.edu.au/view/UQ:161763 Arising from the collection of numerical routines (validation toolbox) developed for validating discrete element method (DEM) predictions of charge motion in grinding mills, a range of rigorous charge analysis techniques have been developed. These provide descriptors of the motion and grinding regimes in a mill that hitherto have not been presented in the literature. To make the analysis meaningful, the descriptions of the charge motion were expressed as mathematical relationships that are applicable over the full range of charge motion that can be experienced in a rotary mill. The original division of the charge using the concept of the equilibrium surface, as proposed by Powell and Nurick (1996) [A study of charge motion in rotary mills. Part 1 – Extension of the theory. Miner. Eng. 9 (2), 259–268], has been refined to provide a surface that can be analytically derived from positional data. From this the position of the centre of circulation (CoC) of the charge can be objectively determined. The rate of circulation of the charge is calculated from knowledge of the position of the CoC. Improved techniques are presented for determining the shoulder and toe positions of the bulk charge. Plots of velocity, acceleration, interaction force, frequency of passing through a particular region, etc. can be expressed as a function of position in the mill. Through a consistent analytic characterisation of the charge, the influence of varying the operating conditions on the motion of the charge and the formation and intensity of different grinding regimes can be derived. This paper presents the methods to perform such an analytic characterisation and discusses how they may be used to improve milling efficiency. 2009-01-27T00:00:00Z Powell, M. S. og McBride, A. T. http://espace.library.uq.edu.au/view/UQ:98526 2007-08-24T00:00:00Z Vera, M. A. og Franzidis, J. http://espace.library.uq.edu.au/view/UQ:143810 2008-06-10T00:00:00Z Djordjevic, N.