Contributions to the mechanisms and simulation of mineral processing operations

[摘要] ENGLISH ABSTRACT: This collection of 101 published papers is based on 19 years of research, mainly in SouthAfrica and recently also in Australia. The main thrust of this work was the simulation ofmineral processing operations where conventional modelling was inadequate owing totheir ill-defIned nature. These papers presented some of the first applications ofknowledge based systems and neural networks to mineral processing problems.A new methodology was proposed for modelling ill-defmed kinetic processes by relatingrates to process conditions via non-parametric methods. The kinetic and equilibriumparameters could be related to adjustment factors if reference conditions changed. Thesemethods were applied to batch and continuous flotation, leaching and adsorption systemsas well as pyrometallurgical processes. In the case of continuous process data intrinsicreaction rates could be back -calculated and then related to process conditions via a neuralnet. It was explained how the configuration of mineral processing circuits could beoptimised by a two-stage linear programming method where the constraints weredetermined interactively by a knowledge based system or neural network. In the case ofnon-linear system constraints neural nets were shown to detect and locate gross errorsefficiently in material balancing problems. Several novel hybrid neural net architectureswere proposed which allowed the integration of parametric fundamental knowledge withnon-parametric heuristic knowledge. Furthermore, it was shown how neural nets could beused to extract knowledge from historical process data records.Pioneering work was conducted on the application of textural image analysis to flotationfroth surfaces and ore particles on a conveyor belt. It was possible to relate imagefeatures to metallurgical performance via neural net architectures. Different types oftopological maps were used to classify froth types, to track the profile of changes inprocess and flotation conditions, and to relate froth class to concentrate grade andrecovery. Perturbations in the comminution circuit were reflected in perturbations in thefroth 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 softsensor for predicting size distribution.A model was developed to combine transport phenomena in the froth phase with fluidflow behaviour in order to optimise mechanical cells and flotation columns. Rateconstants for the various sub-processes were determined by fitting models toconcentration profiles measured at industrial plants. It was shown that the behaviour ofthe froth phase during the flotation of sulphides, gold and uranium was affected bygalvanic interaction between metallic iron and the individual mineral species. Aconceptual model was developed for the flotation behaviour of free gold in the presenceof refractory sulphides for different oxidative conditions and different sequences ofreagent addition.The use of diagnostic leaching to evaluate the efficiency of mineral processing operationswas explained in detail. A first attempt was made to relate diagnostic leaching data tomineral liberation via semi-empirical equations and neural nets. It was explained how theliberation patterns of different types of gold ore could be distinguished by usingtopological maps. The mechanisms of selected sundry processes such as electrokineticsolid-liquid separation, flow splitting, induced aeration and jet reactors were alsoinvestigated.

[发布机构] Stellenbosch University