Presentato alla 8th European Conference in Chemical Engineering, Berlin (D), 26-29 settembre 2011. Session Particle Technology 29/9/2011 h11:00 ABSTRACT: Gas fluidization of mechanically vibrated cohesive silica powder (120 Hz) and a potato starch powder (70 Hz) was tested. The peak acceleration was the main parameter of the mechanical vibration which was changed. It was varied between 2g and 10g. Cohesion of both powders was such that proper fluidization was impossible without the application of mechanical vibration. The starch powder showed gas channelling which tended to disappear for high values of acceleration. At increasing acceleration, increasing bubbling and bubble size were observed. At low acceleration silica powder exhibited cracks which tended to disappear with increasing acceleration. Aggregate diameters were estimated by means of the Ergun equation and compared with those derived from a model in which the aggregate diameter was derived from powder flow properties measured with a shear tester. Results of the aggregate diameter obtained with both procedures show a decrease with increasing acceleration for both powders. In particular, the quantitative agreement between the two modelling approaches is good for silica powder in the entire range of the accelerations tested, and only for high acceleration for the starch powder. The minimum fluidization velocity of the powder was estimated from the aggregate diameter derived from the powder flow properties and the application of the Ergun equation, assuming a voidage between the aggregates constant with the acceleration. Model results are in satisfactory agreement with the experiments.
Aggregative behaviour in gas fluidisation of mechanically vibrated cohesive powders
BARLETTA, Diego;POLETTO, Massimo
2011
Abstract
Presentato alla 8th European Conference in Chemical Engineering, Berlin (D), 26-29 settembre 2011. Session Particle Technology 29/9/2011 h11:00 ABSTRACT: Gas fluidization of mechanically vibrated cohesive silica powder (120 Hz) and a potato starch powder (70 Hz) was tested. The peak acceleration was the main parameter of the mechanical vibration which was changed. It was varied between 2g and 10g. Cohesion of both powders was such that proper fluidization was impossible without the application of mechanical vibration. The starch powder showed gas channelling which tended to disappear for high values of acceleration. At increasing acceleration, increasing bubbling and bubble size were observed. At low acceleration silica powder exhibited cracks which tended to disappear with increasing acceleration. Aggregate diameters were estimated by means of the Ergun equation and compared with those derived from a model in which the aggregate diameter was derived from powder flow properties measured with a shear tester. Results of the aggregate diameter obtained with both procedures show a decrease with increasing acceleration for both powders. In particular, the quantitative agreement between the two modelling approaches is good for silica powder in the entire range of the accelerations tested, and only for high acceleration for the starch powder. The minimum fluidization velocity of the powder was estimated from the aggregate diameter derived from the powder flow properties and the application of the Ergun equation, assuming a voidage between the aggregates constant with the acceleration. Model results are in satisfactory agreement with the experiments.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.