Estudo do desempenho de um leito de jorro convencional para secagem de leveduras.

Abstract

With the purpose of using the yeast obtained as by-product in the alcohol production on the animal feeding, a study related to the drying of yeasts was carried out. It was observed the performance of a spouted bed dryer. The dryer, whose internai diameter is 10,3 cm, 2?,3 cm tall and internai angle 60°, is formed by a conical basis united to an acrylic cylindrical column. Polystyrene particles (d = 0,326 cm, p = 1,045 g/m') made the bed of still particles (8 cm tall), involving both the conical and cylindrical regions. At the beginning, it was noted the characteristic curves survey and then with the minimum spouted bed results, the speed levei of the yeast drying study was defíned. It was observed that the presence of yeast affects the fluidity parameters: the maximum pressure falling was regarding the situation only with the still particles. This fact is related to a better solids circulation. The minimum spouted pressure was reduced with the increase of the amount of yeast fed. Regarding to the minimum jet speed, no significant variation was noticed with the proportion increasing, even on the presence of yeast A study showed the variable influence, the dryer air entry (0,185, 0,199, 0,213, 0,227 and 0,241 m/s) and the fed yeast percentage (1,2, 2, 4, 6 e 6,8% of still particles mass) in the drying. We evaluated the efficiency of dry yeast production, the retention of particles on the bed and the solids tenor after drying. According to the results obtained the efficiency of powder production was high in ali the experiments when compared to the fruit pulp drying (MEDEIROS, 2001; MORAIS, 1996). The retention of solids on the bed was low, with a variation from 0% to 23,1%, however the losscs werc high, suggcsting the ncccssity of improving the feeding method Regarding to the yeast production kinetic, the results show that the powder production taxes are practically the same. The statistic analysis of the dry yeast production taxes showed that it increases with the yeast percentage increasing, at any speed, under the condition studied. Regarding to the final product quality, it was determined the dampness and nutritional values of the dry yeast. The tenor of protein measure under the condition studied presents very closed values with the total proteins tenors practically constant, at a médium value of 51,53%, an accepted levei according to the legislation that specifies a protein minimum tenor of 25%. The dampness tenor increased with the increasing of yeast percentage at the same speed. It was verified that the dampness tenor varied between 11,19% and 31,34%, with most of them above what is demanded by the legislation (a maximum of 12%). The results obtained show the viability of the process, suggesting, however, the necessity of complementary studies with the purpose of improving the operational condition.