Experiments on the temperature distribution in the solid bed of rotary drums

Abstract

In rotary drum processes, the temperature distribution inside the bed is of key importance in improving product quality. Temperature differences in the solid bed could be caused by motion behavior, chemical reaction and heat transfer. The radial and circumferential temperature profiles in an indirectly heated rotary drum were measured using 15 Type K thermocouples assembled on both rotating and fixed rods that were attached inside the drum. The experiment was conducted with a constant filling degree and a constant rotational speed. Glass beads with a defined particle diameter were used as test material. The results show that temperature differs in the circumferential and radial direction. In radial direction, the temperature decreases from the inner wall to the boundary line in the passive layer, however, the temperature increased from the boundary line to the bed surface in the active layer. The temperature gradient in the upper part is lesser than the lower part of the boundary layer due to mixing of particles. A normalized temperature difference was calculated to show the temperature difference over time during the heating phase of the drum. The result obtained from the normalized temperature difference can give insight on how to predict the temperature difference inside the bed for other temperature ranges.