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To improve upon the understanding and efficiency of the crushing/ i screening process, the Brenda Mines Limited secondary crushing plant was simulated. The plant consists of two stages of crushing, with a single stage of screening employed in closed circuit with the latter crushing stage. Acquisition of plant data was carried out according to full or modified factorial designs intended to cover normal operating ranges. The units sampled include a Symons Nordberg 7 - foot standard cone crusher, a Symons Nordberg 7 - foot short-head cone crusher and two Allis-Chalmers 8ft.x20ft. double deck virbrating screens. Sampling was carried out under conditions as close to steady state as was possible. All samples were screened at the plant using a standarized procedure. Raw data obtained around the screens was later adjusted by means of a least squares technique that assumes all measured values are in error. The models developed to describe both crushing operations are modifications of those used at Mt. Isa Mines Limited. The model parameters were empirically fitted to the observed data. Both models gave satisfactory performance. The model proposed for the vibrating screens was derived from small particle statistics. It is continuous over all size ranges and was judged to perform satisfactorily. Models for the short-head crushers and the screens can be extrapolated approximately twenty percent beyond their fitted data ranges. The fitted models were combined to enable a steady-state simulation of the complete secondary crushing plant. A study of the simulation was performed in accordance with a full factorial design modified to include intermediate ranges. Operating variables whose values were generated during the simulation remained within their fitted ranges, with the exception of the short-head crusher feedrate. Preliminary analysis of the simulation output shows that the results conform to expected and observed plant behavior. Further analysis with respect to short-head crusher power draw indicates that it may be possible to increase plant capacity under some conditions. The economic advantage of a digital simulation is demonstrated by the fact that the average cost for one computer run is approximately twenty cents. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

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Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1916. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed April 21, 2009)

Thesis (MScIng)--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

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A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree of Master of Science in Engineering. May, 2016 / Particle size and size range are among the characteristics that affect the segregation of particles in a jig hence they affect the separation efficiency. The effects of these variables on segregation of particles are not fully understood. This work aimed at contributing to knowledge in this area. To better understand how particle size and size range influence segregation, tests were conducted in which the effects of the density and shape of the particles on segregation were minimized by using as the feed material spherical glass beads of uniform shape and density. Batch experiments of two components systems of various particle sizes were conducted under the same set of jigging conditions: the jigging frequency and jigging time were respectively maintained at 60 cycles per minute and 999 seconds (16.65 minutes). The effect of these operating conditions on segregation was not investigated. At the end of each test run, the jig bed was split into horizontal slices and the composition of each slice was determined. The experimental results showed that below a particle size ratio of 1.50:1, the driving force for the segregation of particles, i.e. the particle size difference, was small hence a low degree of segregation was obtained. The degree of segregation increased above this ratio. However, above the size ratio of 2.00:1, interstitial trickling occurred. With the smaller particles tested (8, 6 and 4mm) poor segregation was observed when the size ratios were of 1.50:1 or less along with what is believed to have been remixing due to convective currents within the jig chamber. It was found that the particle size range had a more pronounced effect on size segregation than the particle size. From the results, it can be said that above a size ratio of about 1.50:1, size segregation is very pronounced. This suggests that density separations of real ores, where both the density and size of particles vary, would be impaired if the particle size range of the material fed to the jig exceeds this ratio. However, this needs further confirmation by testing multiple component systems.