The extended drop weight testing approach – What it reveals
Section snippets
Introduction and background
The problems which mineral engineers confront in designing, optimising and operating mineral processing plants arise mainly from the heterogeneity of the feedstock (the ore). Unlike in manufacturing, in which all inputs are generally uniform and stable, concentrators have to deal with the exact opposite, and it is this reality which makes mineral processing uniquely challenging. It is therefore important to understand and manage this heterogeneity so as to learn how to manage it for best
Sample mass
The ExDWT quantifies the breakage potential of individual particles in a given sample of ore. It involves measuring three particle properties:
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Particle Mass
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Residual height of DWT after breakage
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Fragmentation (tn, where common values for ‘n’ are 2, 4, 10, 25, 50 and 75)
The mass of each particle is measured before breakage. Variation in the mass of particles within a size fraction affects the specific energy received per particle which is further described in Faramarzi et al. (2018b). This type of
ExDWT method with a single size fraction
The standard t10 is estimated based on the standard t10 size ‘’. In this approach, the geometric mean is assumed as the same for all the particles within a size fraction:where T and B are the upper and lower sizes of a given size fraction, respectively and GM is the geometric mean. It should be noted that the t10(std) represents the passing size in this context. In this paper, tn value refers to the degree of breakage, and tnØ represents its characteristic size. As an example,
A more general definition of the ‘t10 size’
The initial size of an irregular particle can be defined in a number of ways, depending on the purpose (Napier-Munn, 2014). In this paper only particles of a narrow size fraction –22.4 + 19 mm are considered. Here we determine the effect of five different definitions of the parent size of each particle and assess the impact on the t10 percent passing defined in the context of that estimate of parent size. These definitions are as follows:
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Standard t10 size, ‘’ – It is estimated based on
Conclusions
The ExDWT approach to testing the competence of rock particles estimates the benchmark A × b value using data from a large number of individual particles and the newly proposed concept of a tn-family per particle. This contrasts with the standard JKDWT method which fits the model to 15 data points, each one being the average response of several particles in a given size interval, and uses the traditional concept of the tn-family for a group of particles. The ExDWT breakage testing approach
CRediT authorship contribution statement
Farhad Faramarzi: Conceptualization, Investigation, Methodology, Formal analysis, Validation, Writing - original draft, Writing - review & editing. Tim Napier-Munn: Supervision, Writing - review & editing. Robert Morrison: Supervision, Writing - review & editing. Sarma S. Kanchibotla: Supervision.
Declaration of Competing Interest
The authors declared that there is no conflict of interest.
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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