Leaching reactors have been described using three different approaches. These models are the overall mass balance, the population-balance model and the segregated-flow model. Each of these models has been used extensively without the relationship between them being either understood or quantified. These models do not only differ in their conceptual basis, but also yield different results for the same reaction conditions. The conceptual relationship between the various approaches to the mathematical modelling of continuous leaching reactors is discussed, and it is suggested that the population-balance model is the most appropriate approach for the modelling of leaching reactors.

The population-balance method of the mathematical modelling of leaching reactors is discussed. The population balance incorporates the kinetic parameters obtained from the analysis of the batch experiments. Themodelisusedtoanalysethebatchlaboratoryexperiments andtopredicttheoperation of the continuous plant. The model accounts for the particle-size distribution of the feed, the residence- time distribution of the reactor, the leaching kinetics, and the solution mass balance.

The model is used to obtain predictions of the operation of the zinc pressure leaching reactor at Trail, B.C., and the bacterial leaching of a refractory gold ore at Fairview, South Africa. The predictions of the continuous operation are shown to be in excellent agreement with the data from the plant operation.