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An investigation of the principles of laboratory-scale particle-bed comminution

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2008
Cimilli, Hande
The objective of this thesis is to investigate the principles of laboratory-scale particle bed comminution in a piston-die-press. The feed materials used in this investigation are quartz and calcite which were stage-crushed and dry screened to produce 3.35 x 2.36, 2.36 x 1.7, 1.7 x 1.18, 1.18 x 0.85, and minus 0.85mm size fractions. First, these narrow size fractions (excluding minus 0.85mm fraction) were comminuted under different pressures to determine the baseline for energy utilization. Then, these size fractions and minus 0.85mm size fraction were proportionately mixed to produce feeds of three different size distributions having three different Gates-Gaudin-Schuhmann (GGS) size distribution moduli (m=0.5, 0.7, and 0.9), and comminuted under different bed pressures of appropriate magnitudes to generate a reasonable range of specific breakage energy inputs. As a result of the experiments carried out, it can be concluded that higher amounts of fines were obtained from calcite samples than quartz at all narrow-range size fractions and distribution moduli. Furthermore, experimental results showed that the feed material having the widest size distribution (m = 0.5) showed more resistance to size reduction when compared with narrow-size fractions, which led to increase in energy consumption due to the presence of higher amounts of fines. Tests samples with distribution moduli of 0.7 and 0.9 showed higher resistance to size reduction than narrow-size samples, but the reduction ratios achieved with the size distributed samples were higher than those achieved with the narrow-size samples. In addition, by using t-curves (t50 and t10) the amounts of breakage of different samples were compared. Consequently, the distribution modulus of 0.9 gave better breakage results in terms of expended energy and amount of breakage than all narrow-size fractions, especially for the relatively soft mineral calcite.