A STUDY OF THE EFFECT OF IMAPCT ANGLE ON SURFACE BREAKAGE OF ANGULAR
AND SMOOTH PARTICLES
Mohsen Yahyaei a, Malcolm Powell a, Daniel M. Francioli b, Luís M. Tavares b
a Julius Kruttschnitt Mineral Research Centre (JKMRC), Sustainable Minerals Institute, The University of
Queensland, Brisbane, Australia
b Department of Metallurgical and Materials Engineering (COPPE), Universidade Federal do Rio de
Janeiro
ABSTRACT
Although low-energy incremental surface breakage occurs at the lower end of the collision energy spectrum,
due to a higher frequency of occurrence, it is a major mechanism of size reduction in milling. Thus it is
necessary to understand this mechanism of superficial breakage that is currently poorly addressed.
During the surface breakage process, particle shape evolves from angular to smooth as it moves through the
milling process. Evolution of particle shape changes the particle response to low-energy impacts. The
existing ore characterisation methods do not capture this change in behaviour due to evolution of particle
shape. Therefore, estimates of rock strength are affected by surface roughness of particles. This research
studies the effect of particle angularity in response to low-energy incremental impacts.
Low-energy incremental impact experiments were conducted using a gold/copper ore (C-Ore). Mass loss of
100 angular and 100 smoothed particles was tracked individually during low-energy incremental impacts by
dropping the particles from 4, 2, and 1 m heights into a steel plate. Incremental breakage testing was also
conducted using the JKRBT with 0.01 kWh/t specific energy to evaluate the repeatability of results using
the JKRBT. Results indicate that the average mass loss of angular particles for the first two impacts is 38%
higher than smoothed particles, decreasing to 7% after 10 impacts. The average mass loss of angular particles
rapidly declined during the first 10 impacts while the average mass loss of smooth particles was fairly
constant. The JKRBT set to the same energy level as dropping rocks from a 4 m height indicated a higher
breakage rate, possibly pointing to secondary breakage effects (Figure 1).
The experimental data and implications for mechanistic comminution modelling are presented.
Figure 1 – Comparison of cumulative breakage probability of JKRBT and dropping rock at same input
energy
KEYWORDS
Comminution, Surface breakage, JKRBT