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Abstract
Direct observation of charge shape and its motion in industrial mills is not possible; therefore, a combination of analytical and physical studies is used to determine charge trajectory. Software packages, which predict charge motion consider only the outermost layer of charge (single ball) and ignore the charge and the interactions of grinding elements. In the new version of the GMT (Grinding Media Trajectory) software, the effect of liners specification and bulk load on charge shape and trajectory are considered. The charge trajectory was measured in a laboratory mill with the diameter of 100 cm and length of 21.5 cm with the transparent end and compared with that of the old version of GMT. Four types of polyurethane rings were accurately machined to scale down the liners arrangements at two industrial mills. The model mill was operated at 55, 70 and 85% of the critical speed for ﬁve levels of mill ﬁlling (10, 15, 20, 25% and 30% by volume). The experiments indicated that the end walls effect was negligible for the model mill with the length of 10.8 cm and beyond. The proposed relationships to correct the trajectory and charge shape were validated by using the new liner of the Gol-E-Gohar iron ore company AG mill. The positions of shoulder, toe, toe departure and impact points were predicted with the relative errors of 5, 0.7, 2 and 0.2%, respectively. The GMT software was updated with the new relationships. The results of GMT simulation indicated that when the lifter face angle increased from 7 to 30˚, the distance between the charge impact point and the toe decreased from 40.1 to 11.2˚ for 30% ﬁlling. The change in the position of the impact point meant increasing the probability of charge impacting the toe, not the liner which favored more efﬁcient comminution practice.

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		KMPC Hemmat A Mineral Processing Digital Library
	All Years to Access Full-Text Export citations GMT: A SPREADSHEET-BASED SOFTWARE TO PREDICT CHARGE SHAPE AND TRAJECTORY IN TUMBLING MILLS By M. Maleki-Moghaddam, M. Yahyaei , S. Banisi Published in International Mineral Processing Congress (IMPC) at 2016 Direct link: http://kmpchemmat.ir/pii/74610 Abstract Direct observation of charge shape and its motion in industrial mills is not possible; therefore, a combination of analytical and physical studies is used to determine charge trajectory. Software packages, which predict charge motion consider only the outermost layer of charge (single ball) and ignore the charge and the interactions of grinding elements. In the new version of the GMT (Grinding Media Trajectory) software, the effect of liners specification and bulk load on charge shape and trajectory are considered. The charge trajectory was measured in a laboratory mill with the diameter of 100 cm and length of 21.5 cm with the transparent end and compared with that of the old version of GMT. Four types of polyurethane rings were accurately machined to scale down the liners arrangements at two industrial mills. The model mill was operated at 55, 70 and 85% of the critical speed for ﬁve levels of mill ﬁlling (10, 15, 20, 25% and 30% by volume). The experiments indicated that the end walls effect was negligible for the model mill with the length of 10.8 cm and beyond. The proposed relationships to correct the trajectory and charge shape were validated by using the new liner of the Gol-E-Gohar iron ore company AG mill. The positions of shoulder, toe, toe departure and impact points were predicted with the relative errors of 5, 0.7, 2 and 0.2%, respectively. The GMT software was updated with the new relationships. The results of GMT simulation indicated that when the lifter face angle increased from 7 to 30˚, the distance between the charge impact point and the toe decreased from 40.1 to 11.2˚ for 30% ﬁlling. The change in the position of the impact point meant increasing the probability of charge impacting the toe, not the liner which favored more efﬁcient comminution practice. Keywords Comminution, SAG mill, Charge shape, Charge trajectory