Browsing by Author "Van Deventer, Jan Stephanus Jakob"
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- ItemContributions to the mechanisms and simulation of mineral processing operations(Stellenbosch : Stellenbosch University, 1999-08) Van Deventer, Jan Stephanus Jakob; Lorenzen, L.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: This collection of 101 published papers is based on 19 years of research, mainly in South Africa and recently also in Australia. The main thrust of this work was the simulation of mineral processing operations where conventional modelling was inadequate owing to their ill-defIned nature. These papers presented some of the first applications of knowledge based systems and neural networks to mineral processing problems. A new methodology was proposed for modelling ill-defmed kinetic processes by relating rates to process conditions via non-parametric methods. The kinetic and equilibrium parameters could be related to adjustment factors if reference conditions changed. These methods were applied to batch and continuous flotation, leaching and adsorption systems as well as pyrometallurgical processes. In the case of continuous process data intrinsic reaction rates could be back -calculated and then related to process conditions via a neural net. It was explained how the configuration of mineral processing circuits could be optimised by a two-stage linear programming method where the constraints were determined interactively by a knowledge based system or neural network. In the case of non-linear system constraints neural nets were shown to detect and locate gross errors efficiently in material balancing problems. Several novel hybrid neural net architectures were proposed which allowed the integration of parametric fundamental knowledge with non-parametric heuristic knowledge. Furthermore, it was shown how neural nets could be used to extract knowledge from historical process data records. Pioneering work was conducted on the application of textural image analysis to flotation froth surfaces and ore particles on a conveyor belt. It was possible to relate image features to metallurgical performance via neural net architectures. Different types of topological maps were used to classify froth types, to track the profile of changes in process and flotation conditions, and to relate froth class to concentrate grade and recovery. Perturbations in the comminution circuit were reflected in perturbations in the froth image features and metallurgical performance. It was also shown that the spray angle of a hydrocyc1one as determined by image analysis could be used as input to a soft sensor for predicting size distribution. A model was developed to combine transport phenomena in the froth phase with fluid flow behaviour in order to optimise mechanical cells and flotation columns. Rate constants for the various sub-processes were determined by fitting models to concentration profiles measured at industrial plants. It was shown that the behaviour of the froth phase during the flotation of sulphides, gold and uranium was affected by galvanic interaction between metallic iron and the individual mineral species. A conceptual model was developed for the flotation behaviour of free gold in the presence of refractory sulphides for different oxidative conditions and different sequences of reagent addition. The use of diagnostic leaching to evaluate the efficiency of mineral processing operations was explained in detail. A first attempt was made to relate diagnostic leaching data to mineral liberation via semi-empirical equations and neural nets. It was explained how the liberation patterns of different types of gold ore could be distinguished by using topological maps. The mechanisms of selected sundry processes such as electrokinetic solid-liquid separation, flow splitting, induced aeration and jet reactors were also investigated.
- ItemKinetic model for the adsorption of metal cyanides on activated charcoal.(Stellenbosch : Stellenbosch University, 1984) Van Deventer, Jan Stephanus Jakob; Stellenbosch University. Faculty of . Dept. of .