Modelling of bacterial leaching in heap with forced aeration

A transient model for bioleaching of copper sulphide minerals in heaps/dumps with forced aeration was developed for a bed formed by particles of different particle sizes. Equations for the transport of oxygen, mass balance for copper and ferric ions, and heat transport were considered. The reaction in the particles was described by the shrinking core model. The present work considers two principal objectives. First, the possibility to find some "average radius" that represents the performance of a heap with a distribution of particle size was studied. Two possible average radii were tested. The first one is the "weight average radius" where the weight fraction for each size is used as weighting factor. The second one is the "surface average radius" where the weighting factor is the specific surface fraction for each size. The simulations show that it is not possible find such average radius. This means that the performance of the heap can not be determined using an "average radius", therefore a distribution of particle sizes has to be used. And the second objective, heap bioleaching with forced aeration was studied identifying the zones where the aeration is not appropriate in order to optimise the aeration configuration. The criterion used for the optimisation is to obtain almost the same reaction rate at a same height. The simulations indicate that this may be obtained by increasing the gas flow or by decreasing the distance between the aeration channels.