CFD evaluation of the influence of the draft tube on solids circulation in conical spouted beds

The particle circulation is important to guarantee process homogeneity and efficiency in conical spouted beds. This work investigated the influence of the draft tube on the solids circulation of conical spouted beds using a Computational Fluid Dynamics (CFD) Euler–Euler multiphase model. The solids mass flow in the spout and the particle cycle time were estimated for different conditions of solids bed height and inlet air velocities. Validation of the mathematical model was performed comparing the minimum spouting velocity according to experimental data from the literature, presenting deviations of 1.6% and 7.5%. Simulation results indicated a reduction in the minimum spouting velocity between 46.7 and 53.0% after the insertion of the draft tube in the equipment. However, the draft tube reduced the solids mass flow rate in the spout by approximately 70.5–78.0% when compared to configurations without the tube, hence causing a pronounced increase in solids cycle time. CFD performed a detailed and physically coherent analysis of the behavior of particle circulation parameters that are difficult to obtain experimentally.