in Wiley InterScience (www.interscience.wiley.com).Published models apply particle size to predict bioleaching reactor performance. In this study mathematical models predicting the overall reaction rate of a bioleach reactor system are developed to establish which particle parameters are necessary to describe reactor performance. Since the intrinsic leaching rate is surface area dependent, the inlet particle size and residence time are model inputs. Three models, distinguished by the incorporation of age and/or size distributions, were developed from first principles through a segregation approach. Explicit dependence on the age distribution, allows the model extension to unsteady state behavior and imperfect mixing. The models are validated against pilot plant data for pyrite-arsenopyrite concentrates obtained from the Fairview Mine in South Africa. Simulation results indicate that only a model that considers both the particle age and size distribution is in good agreement with the data.
A study was undertaken to investigate the dynamics of chalcopyrite bioleaching. The analysis revealed significant dynamics features because the chemical leaching rate of chalcopyrite does not vary monotonically with solution redox potential but undergoes a maximum followed by a minimum as potential increases. The analysis does account for reaction passivation, an effect that has consistently been reported in the literature. The existence and stability of steady states were determined as functions of the solution redox potential, reactor temperature, and biomass concentration. It was found that the rate of bioleaching increased with temperature at lower overall solution potentials with competitive rates observed at high ferric/ferrous ion ratios. Both high and low overall bioleaching rates were observed with increasing biomass concentration, indicating an upper concentration limit before passivation. These results indicate that the frequently observed inhibiting rates may simply be artifacts of the system dynamics rather than due to physical phenomena.
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