A simple calculation for residency time of grinding balls inside grinding mills

The residency time of grinding balls inside grinding mills has been calcula ted in the present work assuming an abrasive wear mechanism without breakag e. From the ratio of total weight of balls in the mill to the daily additio n weight of balls, the ratio of the grate openings size of the mill to the original ball size, and the rotation rate of the mill, the residency time o f grinding balls can be determined numerically. The influence of these para meters on residency time was studied in detail. The existence of grate open ings was shown to reduce the residency time significantly. The calculated r esults were fairly consistent with two experimental observations in both mi lls with and without exit grates. (C) 2001 Elsevier Science B.V. All rights reserved.