| The object of the present thesis was the development of a mathematical model suitable for computer simulation of hydrometallurgical processes. The model formulation was made for a strongly exothermic three-phase reaction system, namely the pressure oxidation process as applied to the treatment of refractory gold ores and concentrates. The steps followed during the course of this work involved first, the experimental identification of the intrinsic kinetics of the two principal refractory gold minerals, arsenopyrite and pyrite, and second, the development of reactor models describing the isothermal and non-isothermal behaviour of batch and multi-stage continuous reactors at steady state. Emphasis was given to the identification of feed conditions for autothermal operation.; The key features of the developed model are the coupling of both mass and heat balance equations, the description of the non-isothermal performance of a multi-stage continuous reactor, and the treatment of a two-mineral mixture concentrate. In addition, continuous functions are used to describe the size distribution of reacting particles and gas-liquid mass transfer rate limitations are assessed.; The model predictions were in good agreement with pilot-plant scale industrial data. Simulation runs of alternative reactor configurations and feed compositions elucidated the impact of the size of the first reactor stage, the rate limiting regime, and the sulphur content of the feed on the attainment of autogenous performance. |
