The charge motion in a tumbling mill is analyzed in detail using a num
erical simulation scheme known as the discrete element method (DEM). I
n particular, the profile of the ball charge, impact energy distributi
on and power draft ape predicted as a function of mill operating condi
tions. The analyses are verified by direct experimentation in a 90-cm
diameter ball mill of adjustable length fitted with a transparent end-
plate. The images of the charge motion are captured on a video camera
and analyzed with image-processing software. Simultaneously, the mill
power is recorded with a torque sensor. The DEM prediction of power dr
aw is compared with experimental measurements. Also, predicted charge
profiles are compared with video images. Both ball segregation and sur
ging phenomena are analyzed. A novel scheme of analyzing video images
for obtaining impact energy spectra is shown. In all cases, the result
s of the numerical scheme are in good agreement with experimental meas
urements, thereby proving that the three dimensional numerical code is
a viable tool for ball mill analysis. (C) 1997 Published by Elsevier
Science Ltd.