Analise da fluidodinamica de leito de jorro durante o recobrimento de particulas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

Among the several unit operations that seek the modification of superficial characteristics of solid partic1es, the spouted bed appears as a substitute for the fluidized bed, to process a great variety of coarse solid materiaIs. The use of this technique for the partic1e coating, initially employed in the pharmaceutical industry, is promising, which motivated several studies involving basic equations for the design and improvement of this technology. This work investigated the fluid-dynamics of the conventional spouted bed during a coating process, using several inert partic1es such as polystirene, polypropilene, polyethilene of low density, ABS@, tablet and glass beads, and analyzed the influence of the physical properties of the partic1es and of the coating suspension on the fluid-dynamics. An aqueous polymeric suspension was used in the coating experiments. The suspension formulation is the same used in previous studies of coating of tablets (A T AÍDE, 1996). The suspension was characterized by the surface tension, specific mass, rheology and contact angle between the suspension and the solid surface. The fluid-dynamics essays with and without coating were made in a conical-cylindrical spouted bed already installed in the Laboratory of Fluid-dynamics and Drying (LFS). It was verified that the partic1es having a high contact angle with the suspension (polystirene, polypropilene and polyethilene of low density) did not present an efficient coating, but only the drying ofthe suspension. For the other partic1es (ABS, Placebo and Glass Spheres), it was obtained coatings with efficiencies in the range of 40 to 90%. The shape, angle of repose and density of partic1es affected the fluid-dynamic during the coating, and also the inter-partic1e friction and the partic1e circulation velocity in the annulus. It was also determined the maximum suspension flow supported by the bed for these three partic1es, at operating conditions established at preliminary tests. The solids velocity inside the spouted bed was also measured in order to correlate this circulation rate with the saturation degree of the bed. It was verified that the circulation of the partic1es in the bed is related with the saturation grade in the bed. In beds with higher saturation degrees, the partic1es are heavier and their velocities in the annulus decrease

ASSUNTO(S)

revestimentos processo de leito de jorro dinamica dos fluidos

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