UBC Theses and Dissertations
Digital simulation of a crushing plant Hatch, Christopher
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.
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