Influência dos parâmetros de reversão na homogeneidade de um leito durante a secagem de alumina

Abstract

An undesirable aspect of fixed bed dryers is that they generate a product with uneven distribution of moisture and temperature of the particles along it, in the direction of drying air flow. This can result in a non-quality product, which can lead to significant losses in subsequent operations. This disadvantage can be overcome by periodically reversing the direction of flow of the heated air, whose burden is the longer drying time and the higher cost. In the conventional process without inversion, the temperature in the layer closest to the inlet of the heated air reaches dynamic equilibrium faster than the later layers, while the layer farthest from the inlet takes longer to do so. In the drying process with periodic inversion, the dynamic temperature equilibrium is disturbed with each inversion. Thus, the reversal of the air flow direction confers a mixing character to the fixed bed drying, which must be proven in numerical experiments by the reduction of the humidity gradient. The reversal technique has as operational parameters the initial moment of application of the first change in flow direction and the time between subsequent inversions. The final paper proposal summarized here, aimed to evaluate the influence of these parameters on the degree of uniformity of a fixed bed during the drying of alumina particles. Numerical tests were performed using a MatLab® program developed in the Particulate Systems area of DEQ/UFSCar. With the results of the simulations, it was possible to identify trends of change in the homogeneity of the fixed bed, and that the parameters evaluated significantly alter the operation of the bed and must be analyzed in order to obtain the best uniformity of the process.