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13th Spring School on Transition and Turbulence
Particle fragmentation in turbulent dense gas-solid fluidized beds jets: fragmentation potential modeling, parametric sensitivity study, and CFD-based optimization
Richard Tribess , SC
Co-Authors: Richard Tribess, Celso Murilo dos Santos, Wladir Pedro Martignoni, Dirceu Noriler, Henry França Meier
Presenter: Celso Murilo dos Santos
The distributor region of dense gas-solid fluidized beds is characterized by enhanced momentum rates and high solids concentration gradients. The high gas injection velocities can potentialize unwanted effects such as the bed material attrition, which can become a problem, affecting the fluidization process efficiency due to drastic changes in the particulate material properties. The design parameters of the injection nozzles found in gas distributors systems play a serious role in the particulate material fragmentation. This study aims at describing a fragmentation potential, considering the relationship between the breakage probability and the collision frequency between two particles, in an Euler-Euler framework using the TFM-KTGF model. 2D-axisymmetric simulations are performed and the influence of the injection nozzle design parameters is evaluated through a parametric sensitivity study. Based on the significant variables obtained from the parametric sensitivity study, the fragmentation potential is employed as an objective function to be minimized in a CFD-based optimization using the COMPLEX algorithm. Through the performed analysis, it was possible to observe that the proposed fragmentation potential is highly influenced by the injection nozzle’s design parameters, mainly the orifice diameter and the tube diameter, with differences of up to 600 times between the analyzed cases. Smaller orifice diameters aligned to bigger tube diameters showed considerably smaller results for the fragmentation potential. This behavior is related to smaller mean velocities in the nozzle outlet and larger orifice-to-particle diameter ratios. During the optimization procedure, a tendency for the inlet nozzles to reach the same geometrical characteristics was observed, according to the geometrical restrictions employed.
Dense fluidized beds, Attrition, Computational Fluid Dynamics, Parametrical sensitivity study, CFD-Based optimization