Investigação numérica e experimental do escoamento granular e dos fenômenos de segregação radial e axial em tambor rotatório

Abstract

Understanding the behavior of granular flows and particle dynamics is of fundamental importance with regard to project design and optimization of industrial equipment. Among them, the rotating drums have gained prominence due to their relatively simple geometry, which consists of a horizontal cylindrical structure that rotates around the axis itself. However, particle segregation has become one of the recurring problems in the use of this equipment, which may negatively affect the efficiency of the mixing process. In this context, the present work aimed to study the phenomenon of particle segregation in a rotating drum by numerical and experimental techniques. In the numerical study, the Lagrangian approach was used, in which each particle is accompanied individually, with the consequent application of the balance of forces, taking into account the interactions with the other particles through contact laws. Experimentally, the coefficients of restitution, static friction and rolling friction were measured, based on ASTM G194-08 norms, as well as the determination of the static angle of repose and the critical speed of centrifugation, evaluating the effect of equipment design variables and of granular physical properties. As for the Lagrangian approach, the experimentally obtained DEM parameters were used to quantify the granular diffusivity and segregation kinetics inside the rotating drum, evaluating the influence of granular physical properties such as diameter and density. For this, size and density ratios ranging from 0.1 to 1.0 were employed, with the drum operating at rotational speeds of 1.0 rad / s and 25% fill degree. Both diameter differences and density differences promoted the phenomenon of segregation in the radial and axial directions. Further analysis was performed in relation to the segregation kinetic constant and the stationary segregation index, for which the influence of granular properties was evaluated. When comparing the granular bed images in the study of the experimentally obtained flow regimes with those generated by the numerical resolver, the similarity between them was observed, allowing to affirm that the numerical tool was promising in the analysis of the phenomenon.