Fine powders were found to be fluidized in a rotating drum by internal cycling gas by the drum rotation. It is essentially a fluidized bed without requiring any external fluidizing gas. Such a rotating drum can be regarded as a new gasless fluidized bed for fine powders in contrast to a traditional fluidized bed, possibly leading to a considerable amount of energy savings. In addition, the fluidization quality of fine powders was found to be further improved with the assistance of drum rotation because of the shearing movement among particles that eliminates channeling and cracks and possibly also breaks agglomerates. Five regimes were identified in the rotating drum including slipping, avalanching-sliding, aerated, fluidization and re-compacted regimes. It was also found that drum wall friction plays an important role to fluidize fine powders because the friction carries particles to the freeboard, leading to gas cycling that fluidizes the powders. As well, three types of specially designed baffles were utilized to promote powder fluidization in rotating drums. These baffles effectively bring an early onset of all the regimes in rotating drums by reducing powder-wall slipping, carrying particles and bringing additional gas to the powders. (C) 2009 Elsevier Ltd. All rights reserved.