Comportamento fluidodinâmico em leito de jorro constituído por mistura de partículas.

Abstract

The importance of the knowledge about fluid dynamics of spouted beds constituted by mixture of particles is apparent in a number of process in the chemical pharmaceutical industry and food technology. The dehydration of pulps and suspensions, the obtention of a blxine concentrated powder by attrition of annafto seeds( Bixa Qreiiana L), are examples. When particles of diameter in the order of 100um; whom we will call "entrainable" are present in the bed of spoutabies particles, the mechanisms of circulation are different of those in the conventional spouted bed. As the spoutable and a part of the entrainable particles circulate in the bed, an other part of the fines is trained and captured by the cyclone and the rest accumulate fluidizing at the top of the annulus. Although there are some studies about the fluid dynamics of beds with a mixture of particles with diameters of the same magnitude, works about the behavior of these type of systems when constituted by particles with great differences in size, are scarce, in previous work the effect of the presence of the powder, obtained by the attrition of the seeds, over the fluid dynamics of a spouted bed of annafto seeds was analyzed. Is this work, the results were extended to différents mass ratio of fine to coarse particles . A synthetic system of polypropylene and maize flour was also studied for comparison. An important influence of the fines proportion over the circulation characteristics and fluid dynamics parameters were verified. The characteristics curves were followed by the partial entraînement of the fines. It was observed that the APmâ* is decreased and APim is augmented with the increasing of the entrainable particles proportion. Nevertheless no influence of the fines over the Uim was detected.