A comprehensive simulator which can be used for the design and optimisation of industrial flotation circuits must include models for the sub-processes taking place in both pulp and froth regions. While the kinetics in the pulp has been widely investigated, there is still a notable lack of understanding on the froth behaviour. This situation can be explained by the practical difficulty in quantifying the mass transfer of solids within the froth in terms of the rejection of entrained particles and the recovery of attached ones. The degree of entrainment has often been quantified via the behaviour of a tracer which ideally is a fully liberated, perfectly dispersed, non-floatable mineral species. However, it appears that further model development is necessary to allow the estimation of the degree of entrainment of hydrophobic species from that of a tracer. The methods available in the literature for quantifying the froth recovery of attached particles encompass indirect estimation based on either modified laboratory equipment or on the simultaneous fitting of various rate constants in a set of differential equations representing froth sub-processes. The outcomes of such methods must be viewed with caution as using modified equipment entails the uncertainty of extrapolating results obtained at laboratory scale whereas, in the methods based on simultaneous fitting, various combinations of rate constants could be fitted to the same set of experimental data.
The main objective of this thesis is to propose and validate a methodology for the direct estimation of both the degree of entrainment and the froth recovery of attached particles in industrial flotation cells. To this end, a set of mass balance equations has been developed which accounts for the transfer of suspended and attached particles throughout pulp and froth regions in a conventional flotation cell. In addition, an empirical partition curve has been developed to describe the variation of the degree of entrainment throughout the size distribution allowing the degree of entrainment of various mineral species to be estimated from the parameters of a tracer. Furthermore, special devices have been developed for the measurement of the mass transfer of air, suspended particles and attached particles up towards the pulp-froth interface in an industrial flotation cell, allowing the direct estimation of the froth recovery of attached particles without intrusive sampling of the froth. Finally, a linear model has been proposed which relates the froth recovery of attached particles with the degree of entrainment throughout the size distribution in the flotation cell being investigated. ........