Using positron emission particle tracking (PEPT) to investigate the motion of granular media in a laboratory-scale tumbling mill

 

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dc.contributor.advisor Govender, Indresan en_ZA
dc.contributor.advisor Mainza, Aubrey Njema en_ZA
dc.contributor.author Morrison, Angus James en_ZA
dc.date.accessioned 2016-02-11T06:58:00Z
dc.date.available 2016-02-11T06:58:00Z
dc.date.issued 2012 en_ZA
dc.identifier.citation Morrison, A. 2012. Using positron emission particle tracking (PEPT) to investigate the motion of granular media in a laboratory-scale tumbling mill. University of Cape Town. en_ZA
dc.identifier.uri http://hdl.handle.net/11427/16969
dc.description Includes bibliographical references. en_ZA
dc.description.abstract Positron emission particle tracking is a Lagrangian, single particle tracking technique in which the trajectory of a representative tracer particle is triangulated from the decay products of the positron-emitting radioisotope with which it is labelled. Although the trajectories of a tracer particle moving in a bulk of similar particles can be of interest, it is often more informative to employ the ergodic assumption and to thus convert trajectory data in the Lagrangian reference frame of the tracer particle into a fixed Eulerian reference frame. This has, in the past, been done by dividing 3D space into voxels and assigning a location probability density to each voxel based on the number of times that triangulated tracer particle locations fall into it- a process called simple binning. A major outcome of my work has been to develop an alternative probability density based on the cumulative time spent by the tracer particle in a given voxel. This method is called residence time binning, and the resultant probability distribution- which I argue is proportional to, among other things, the mass and solidicity distributions of the tracer particle - the residence time distribution (RTD). In this work I propose, implement and test the residence time binning method, and show that it significantly outperforms the simple binning method in all situations. A second thrust of my work has been to develop a suite of general analysis routines for positron emission particle tracking (PEPT) data, based on the RTD. This suite contains routines for the triangulation, optimisation and pre-processing of PEPT data, as well as for obtaining residence time probability and time-averaged kinematic distributions in 3D space, and for aggregating and visualising the results. I have also extended this general set of routines for the special case of cylindrical symmetry through the addition of routines for the further pre-processing of RTDs, as well as for the calculation of angular measures about an arbitrary axis in space. Finally, I further extended this set of routines for application to tumbling mills. My tumbling mill analysis includes the identification of charge features and regions, and the isolation of charge in each region so-defined for further analysis. These features, particularly the shape of the bulk free and equilibrium surfaces, the angular position of the centre of circulation (CoC) of the charge, and the position of its impact toe allow me to characterise the behaviour of the charge under a range of conditions. This characterisation, together with the shear rate distributions and power draughts that I also calculate, allow me to speak meaningfully about the evolution of grinding regions in tumbling mills- information that could be used to construct charge motion and grinding models to inform the use of tumbling mills in industry. In this work, I apply these analysis routines to a small subset of the experiments performed by the UCT Centre for Minerals Research (CMR) on laboratory-scale tumbling mills, and in so-doing elucidate the behaviour of charge in its different regions- and the evolution of such behaviour with mill operating parameters- and discuss the implications of these to grinding efficacy in tumbling mills. en_ZA
dc.language.iso eng en_ZA
dc.subject.other Physics en_ZA
dc.title Using positron emission particle tracking (PEPT) to investigate the motion of granular media in a laboratory-scale tumbling mill en_ZA
dc.type Thesis / Dissertation en_ZA
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Science en_ZA
dc.publisher.department Department of Physics en_ZA
dc.type.qualificationlevel Masters en_ZA
dc.type.qualificationname MSc en_ZA
uct.type.filetype Text
uct.type.filetype Image


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