Investigação numérica e experimental dos fenômenos de segregação e aglomeração em um disco rotatório

Abstract

Among the equipment used for granulation, the rotating dish stands out for having a relatively simple geometry and a pronounced size-induced granular segregation. However, there is no consolidated understanding regarding the particle dynamic within the equipment. In this context, the present work aimed to study the segregating phenomenon of particles due to differences in size and material density in a rotating dish through numerical and experimental techniques. For this, glass and soy particles were used as granular material. By comparing the experimental and numerical results, it was verified that the DEM modeling adequately represented the segregation dynamics within the dish, allowing to evaluate the effect of the inclination angle, the rotational speed and the filling degree on this phenomenon. For both size and density-induced segregation, it was found that all operating conditions had a significant influence on the time to reach steady state and on the segregation intensity. The combined effect of size difference and density was also investigated. It was observed that the effect of the difference in granular size is greater than the effect of the difference in density. Additionally, the DEM approach to cohesive forces was used to model the presence of interstitial liquid in the granular bed, which occurs in wet agglomeration processes. In the numerical model validation stage, the use of the hybrid model composed of the Easo capillarity model for particle-particle contacts and the SJKR model for particle-wall contacts proved to be satisfactory, representing adequately the experimental results. The presence of humidity caused changes in flow regimes when the same velocities were considered. Through analysis of DTR curves, it was verified that the rotational speed of the rotating dish had a significant effect on the distribution of residence times and the effect of the short circuit in the granular beds with interstitial liquid was identified. When evaluating the intensity of agglomeration on the rotating dish, it was observed that the mass fractions of finer granules formed increased and those of larger granules decreased as the rotational speed was increased.