Estudo da segregação de material granular em tambor rotatório empregando a abordagem numérica Lagrangeana

Abstract

Understanding the behavior of granular flows and particle dynamics is of fundamental importance in designing and optimizing industrial equipments. Among them rotary drums have gained prominence due to their relatively simple geometry, which consists of a horizontal cylindrical structure that rotates about the axis itself. However, the segregation of particles has become one of the recurring problems in the use of this equipment, and may negatively affect the efficiency of the process. In this context, the present work had as objective to study the phenomenon of segregation of particles in a rotatory drum by means of numerical and experimental techniques. In the numerical study, the Lagrangian approach was used, in which each particle is individually monitored with the consequent application of the balance of forces, taking into account the interactions with the other particles through the contact laws. Experimentally, the coefficients of restitution, static friction and rolling friction were measured, based on ASTM standards. As for the Lagrangian approach, the calibration of the coefficients of rolling and static friction were performed. These parameters were evaluated in a Central Composite Design and compared with the values obtained experimentally. Through the technique of image analysis, numerical and experimental segregation indices were determined. Using Lagrangian and experimental approaches, the segregation phenomenon in rotatory drum was studied and the influence of granular physical properties such as size and density, as well as the operational conditions: rotation speed and degree of filling were evaluated. For this purpose, diameter and density ratios of 5.62 and 2.11, respectively, rotation speeds of 0.59, 1.10 and 1.77 rad / s and fill levels of 25 and 50% were used. Both the diameter differences and the density differences promoted the segregation phenomenon in the radial and axial directions. An analysis was performed in relation to the kinetic segregation constant, for which the influence of the operating conditions was evaluated. When comparing the images and the kinetics of segregation obtained experimentally with those generated by the numerical resolver, the similarity between them was observed, allowing to affirm that the tool showed to be promising in the analysis of the phenomenon.