Análise da dinâmica de partículas em um leito de jorro pseudo bidimensional por meio de experimentos e simulações Euler-Lagrange usando código open-source

Abstract

The spouted bed equipment is characterized by effective solid-fluid mixing, promoting intense contact between the involved phases. For this reason, it is a fundamentally important piece of equipment for the industry, as some industrial processes require an adequate rate of mass, energy, and momentum transfer. Among the operational difficulties in using a spouted bed are systems involving particles with different physical characteristics, such as diameter, shape, and density, resulting in non-uniform products and the emergence of operational instabilities during the scale-up process. Therefore, a systematic study of particle dynamics within the bed is of fundamental importance for optimizing industrial processes and improving the quality of final products. Considering the above, the general objective of this work was to study the crucial aspects of particle behavior in a pseudo-2D spouted bed through experiments and CFD-DEM (Euler-Lagrange approach) numerical simulations, using both a monoparticle system and a binary particle mixture system. To obtain a robust CFD-DEM model, the proposed methodology included the measurement of DEM parameters through experimental data, a rigorous assessment of the independence of computational mesh size concerning particle size, and a detailed analysis of turbulence models and wall boundary conditions for the fluid phase. The CFD-DEM simulations, incorporating the k-ω SST turbulence model and full-slip wall boundary conditions for the fluid phase, satisfactorily represented the experimental behavior of particle dynamics over time. It was possible to observe phenomena such as internal spout formation, main spout channel characteristics, the development of cavities and bubbles, and particle recirculation. The application of the Fast Fourier Transform (FFT) to the simulated temporal distribution of average volumetric particle velocities allowed the identification of both the pulsating regime of particles and the occurrence of multiple fountain regions within a pseudo-2D spouted bed. The number of collisions and collision force between particles were highly dependent on the initial particle load and the air velocity at the bed entrance. The study of binary particle mixtures, both experimentally and through simulations, allowed for a better understanding of particle behavior in a pseudo-2D spouted bed. The assessment of the segregation index, conducted experimentally and through simulations, showed typical mixing equipment behavior: as mixing progresses, the segregation index gradually decreases until reaching a pseudo-steady state. The higher the fluid velocity at the bed entrance, the shorter the time required to reach a final mixing condition. By analyzing particle trajectories, it was possible to identify percolation and fluidization mechanisms and analyze the effect of air velocity at the bed entrance on the mixing process. It was observed that the behavior of particles near the equipment wall is highly influenced by the probability of colliding with the nearest wall and being thrown in the opposite direction, as well as their trajectory being influenced by the material of the equipment wall. The analysis of contacts between particles of different diameters showed that, at higher velocities, particles tend to move faster and remain in contact for shorter periods. Thus, although there are more collisions, each collision is brief, and the number of simultaneous contacts may decrease.