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CRUNDWELL, F.K. Modeling, Simulation and Optimization of Bacterial Leaching Reactors. Bioengineering and Biotechnology 71 (2001) 255-265

Bacterial leaching represents an unusual prob- lem in biochemical engineering, because the substrate for bacterial growth is not supplied directly, but is a prod- uct of another reaction, the leaching of mineral particles. In addition, leaching is a heterogeneous reaction depen- dent on the particle-size distribution in the feed and on the kinetics of particle shrinkage. In this study, these ef- fects are incorporated in the material balance for each mineral by the number balance. Examination of the num- ber balance gives rise to a novel analysis of the compet- ing technologies for leaching. The model is completed by the addition of material balances for the ferrous and fer- ric ions, the dissolved oxygen, and for each bacterial spe- cies to the number balance for each mineral present in the feed. The model is compared with pilot plant data for three different ores. It is shown that the model is in ex- cellent agreement with the data. The performance of a bacterial leaching reactor is explored using the model, and the washout and sensitivity criteria are determined. It is shown that there are three washout conditions, in which the leaching conversion drops to zero. The wash- out conditions are dependent on the growth rate of the bacteria, on the rate of dissolution of the mineral, and on the rate of mass transfer of oxygen to the reactor. The critical washout condition is that arising from the rate of mineral dissolution. The optimization of a plant in which continuous tank reactors are configured in series is ad- dressed. This analysis shows that the primary reactor should be between 1.5 and 2 times the size of each of the secondary reactors in a series combination. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 71: 255–265, 2000/2001.