Pressure drop and power requirements in a stirred fluidized bed

Abstract

AbstractThe paper reports fundamental observations on the effect which stirring of fluidized solids has on the pressure drop. Typical power requirements are also given.The experimental pilot unit was of 6‐in. diameter and 12 in. high. A special blade or paddle type of stirrer had been built which permitted the evaluation of the effects of blade positioning, blade spacing relative to sense of rotation, as well as the effect of stirrer immersion and rotational speed.The observations disclosed that blade positioning relative to sense of rotation had a very profound effect on pressure drop as well as on power requirements. When the solids circulation pattern as normally induced by the stirrer was of the same general character as that ordinarily encountered in a dense phase fluidized charge, the resulting pressure drop was always considerably lower than the conventional unstirred fluidized bed pressure drop. Furthermore for this type of stirrer the power requirements were also lowest. For other stirrer designs and other induced solids convection patterns the pressure drop was less influenced and the power requirements were much greater.The solids used for the study were a relatively coarse silica sand for which both pressure drop as well as power requirement data were reported. Power requirement data were also obtained for a much finer alumina powder. When one emphasized the effect which particle properties, especially surface characteristics may have the level of the power data was much lower, although the data were of the same character as the characteristic values pertaining to the sand.