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For several decades, the mining and mineral processing industry has contended
with high energy costs of which a large portion is due to mineral comminution
operations. This is related to the low fragmentation efficiency of comminution
which ranges from a value of only ~1 percent to a few percent and is typically
accompanied by low impact velocities ranging from 1 to 10 m·s-1.
In order to study comminution at higher strain rates than those of conventional
equipment, a compressed-air gas gun apparatus has been developed to directly
measure the quantitative parameters of impact velocity on aggregated rock samples.
Experiments have been conducted on three materials at projectile velocities up to
450 m·s-1.
The results suggest the energy efficiency of rock breakage can be improved by as
much as 2 to 3 times under high velocity impact for the same energy input level.
Data analysis and trends are influenced by the impact zone dimension, the hardness
and porosity of the material, and the degree of constraint of the sample.