AN RTD STUDY FOR THE FLOW OF LIGNITE PARTICLES THROUGH A PILOT ROTARY DRYER PART I; BARE DRUM CASE

In Part I of the present work a pilot rotating cylindrical drum, without an internal lifting flight system (bare) has been employed for the study of lignite motion through it, at ambient temperature. Tracer pulse stimulus - response experiments have been carried out io deduce residence time distribution ( RTD) data and relate them to the operating conditions ( slope, speed of revolution, etc.). Mean residence time, space-time and solids hold-up have been correlated with the drum operating conditions. Experimental data of mean axial velocity of solids have been compared with theoretical predictions and found to deviate within a ± 15% margin. A size segregation of particles during their motion through the kiln under a variety of operating conditions has been confirmed and quantified. An average maximum divergence of 20% between the residence time of the smallest and that of the largest nominal particle sizes has been assessed.