The extended drop weight testing approach – What it reveals

Faramarzi, Napier-Munn, Morrison, Kanchibotla

Published in Minerals Engineering July 2020

ABSTRACT

The heterogeneous nature of orebodies introduces large uncertainties into all quantitative evaluations, process design and process predictions. Measuring the extent of the variability of ore competence will allow the design process to account for variation in process performance through a quantitative knowledge of its uncertainties related to ore hardness.

The conventional JKMRC drop-weight test (JKDWT) establishes the relationship between input energy (Ecs) and product fineness (t₁₀) from which the breakage potential parameter A × b can be estimated, by combining the broken progeny of groups of particles. A new method, the Extended Drop Weight Test (ExDWT), has been developed which is applied to individual particles and is therefore capable of capturing breakage heterogeneity at high resolution. This paper explores a number of features of the new method, based on breakage tests on individual particles from several different rock types.

The results showed that more accurate descriptions of particle size resulted in higher (softer) A × b values which suggests that the standard method may have been over-estimating rock competence. Regular-shaped cores broken diametrally were found to have higher (softer) A × b values than axially broken cores and irregular shaped particles. These tests also suggested that the true ore intrinsic heterogeneity is the main source of breakage variability measured by the ExDWT. The mean A × b values determined by the ExDWT showed no statistical difference to those determined by the standard JKDWT method, but the standard deviation of the estimate was much lower.

The results have demonstrated the potential of the new method for capturing the inherent heterogeneity of individual ore particles. Such information could be used to populate multi-component models of comminution.

Authors

Farhad Faramarzi, Tim Napier-Munn, Robert Morrison, Sarma S.Kanchibotla,

Julius Kruttschnitt Mineral Research Centre, Sustainable Minerals Institute, The University of Queensland, 40 Isles Road, Indooroopilly, Qld 4068, Australia

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Acknowledgements

The authors would like to acknowledge The University of Queensland and JKTech Pty Ltd. for sponsoring this research, and we also gratefully acknowledge Barrick Cortez Gold Mine for supplying ore samples.

We also thank the reviewers for many useful comments and suggestions which have been incorporated into the paper.

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