POSITRON EMISSION PARTICLE TRACKING STUDIES OF SPHERICAL-PARTICLE MOTION IN ROTATING DRUMS

Positron emission particle tracking has been used to track the motion of a single radioactively labelled tracer particle within a bed of sim ilar particles in a partially filled horizontal rotating drum. Runs we re performed using 1.5 mm glass spheres in a 136 mm diameter drum and using 3 mm glass spheres in 100 and 144 mm diameter drums, at drum rot ation speeds from 10 to 65 rpm. An active surface layer approximately two-thirds as thick as the underlying bed layer was apparent in all ca ses. Considerable slip of the bed at the walls was observed in most ru ns, which is attributed to a rolling motion of the outermost layer of spheres. The axial dispersion coefficient was determined for each run and was found to be proportional to the frequency at which particles c irculate around the bed, and to be strongly dependent on particle size but independent of drum diameter. (C) 1997 Elsevier Science Ltd. All rights reserved.