Processamento de urucum em leito de jorro: estudos fluidodinâmicos.

Abstract

Annatto (Bixa Orellana L) is an important agricultural product in Paraíba, Northeastern of Brazil. To process the grains, drying and rnechanical extraction by attrition of a high bixine content powder, the spouted bed technique was proposed with good perspectives of industrial application. In the present work, the fluidynamic behavior of fluidized and spouted bed of annatto seeds were studied. For the spouted bed, the cone-cylindrical confíguration, with and without draft tube, was utilized. From the experimental results, the maximum and minimum spouting pressure drops as well as the minimum spouting velocity were evaluated. The data obtained in tlie conventional spouted bed were compared with those estimated from empirical correlations. Since these equations are not generalized they should give only approximated valuer for the parameters analyzed. To a understand more about the involved mechanisms in this process, a set of experiments was developed using a mixture of particles: tlie annatto seeds with tlie powder produced by attrition in different propontions. Because of tlie different properties of this mixture, the system is considered a pneumatic-spouted bed, combining the two behaviors.The preliminary results showed the following trends: an increase in the minimum spouting pressure drop, a decrease of the maximum pressure drop and of a maximum in the minimum spouting velocity with the increasing powder to seeds mass relation. From the measurements of tlie pressure drop in the annulus, the spout diarneter and the air annular velocity were calculated. The air distribution in the annulus showed good agreement with tlie EPSTEIN et alli (1988) model. For scaling up, three equipments were used, with column diameters of 18.0 cm, 30.0 cm and 60.0 cm, ali those with the draft tube. It has been observed that the minimum spouting velocity is greatest in tlie column of lowest diarneter. Nevertheless, the rninimum spouting and maximum pressure drops depend on both the relations column to inlet orifice diarneter, and input orifice to draft tube diarneter.