Chemical Engineering Journal, Vol.362, 712-720, 2019
Fluid dynamics in continuous settler
Continuous settlers are present in the treatment of effluents and domestic water. They have low operational and maintenance cost; however, they can reach high separation efficiency. In this work, the fluid dynamic characteristics of the settler in bench scale, with no-concentric axial inlet in the feedwell were precisely evaluated, using both experimental and numeric approach. The velocity fields were experimentally obtained by PIV (Particle Image Velocimetry). Numerically, the three-dimensional flow was studied using the ANSYS CFX package. For more adequate representation of velocities, the RNG kappa-epsilon, SST kappa-omega, and BSL-RSM turbulence models were analyzed. After the validation of fluid dynamics, it was possible to perform multiphase simulations, analyzing the efficiency of solid particles removal. The Eulerian-Eulerian multiphase model was applied, along with the particle interfacial transfer model. The profiles of axial U and radial V velocity components allowed observing that the BSL-RSM model showed consistent results when compared to the experimental data. In relation to the separation efficiency, smaller particles (10 mu m) were verified to tend to be more evenly distributed in the settler, while larger particles are quickly deposited on the bottom. From the diameter of 100 mu m, there was no difference between the separation efficiency values obtained.
Keywords:Water treatment;Sedimentation;Turbulence;Computational fluid dynamics;Particle image velocimetry