T he coating and encapsulating of particles presents many applications in the chemical, pharmaceutical, food and agricultural products industries. The objective is to apply a thin and uniform layer of material on the surface of a body (Picollo et al., 1997). Among the many applications of seeds coating, the enlargement of small seeds is included in order to facilitate the planting, the addition of herbicides, fungicides, fertilizers, micronutrients and inoculation (Liu and Lister, 1993).The spouted bed has often been used in studies related to the coating of particles. The cyclical motion of the material, which promotes a fast axial mixture of particles and an excellent gas-particle contact, are the reasons for the use of this technique for particles coating (Freire and Oliveira, 1992).
Coating of Soybean SeedsThe coating of seeds in a spouted bed has been the purpose of several studies. Liu and Lister (1992) studied coating mass distribution from a spouted bed seed coater. Conceição studied the influence of operational variables of the process on the soybean seeds coated with fertilizers and macronutrients (MAP and KCl).Lucas (2000) studied the inoculation of soybean seeds with Bradyrhizobium bacteria and the effects of some process variables on the final quality of the seeds and plants. These bacteria adhere to the plant's roots as nodules and supply the necessary of nitrogen, dispensing with the use of ammoniacal fertilizers. The Molybdenum and Cobalt micronutrients were incorporated into the bacteria in suspension, due to their low concentration in Brazilian soils and their importance for the soybean culture.The knowledge about coating distribution is of primary importance because very thick layers impair the germination of seeds by impeding the gaseous interchanges, while the very thin ones do not ensure the ideal activity of bacteria in the process of nitrogen fixation and may not contain the ideal amount of micronutrients. The ideal amount of bacteria is 8 × 10 -5 kg/kg of seeds and of micronutrients is 1.6 × 10 -3 kg/kg of seeds. The ideal bacteria count is 1 × 10 11 cells/kg of coating.Therefore, the objective of this work was to simulate the coating mass distribution of soybean seeds covered with inoculum and micronutrients in a spouted bed through a population balance model based on the general model described by Randolph and Larson (1988
Materials and Methods
MaterialsSoybean seeds, Vencedora variety, were used with a germination rate of 96.8±0.8%. The concentration of the slurry (C S ) used as a coating suspension was 1.3 × 10 6 kg of solids/m 3 of slurry, being 95% solid micronutrients and 5% inoculum. The commercial product used forThe coating of soybean seeds with bacteria and micronutrients favours the vigorous growth of the plant, dispensing with the use of ammoniacal fertilizers. The optimum thickness of the coating should allow the fundamental gaseous interchanges for the germination and the ideal conditions for the activity of the bacteria. The objective of this work was to simulate dynamic...