Mechanics of media motion in tumbling mills with 3D discrete element method

The charge motion in a tumbling mill is analyzed in detail using a numerical simulation scheme known as the discrete element method (DEM). In particular, the profile of the ball charge, impact energy distribution and power draft ape predicted as a function of mill operating conditions. 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 draw is compared with experimental measurements. Also, predicted charge profiles are compared with video images. Both ball segregation and surging phenomena are analyzed. A novel scheme of analyzing video images for obtaining impact energy spectra is shown. In all cases, the results of the numerical scheme are in good agreement with experimental measurements, thereby proving that the three dimensional numerical code is a viable tool for ball mill analysis. (C) 1997 Published by Elsevier Science Ltd.