Simulation of blade shape effect on mixing quality in the gas-liquid agitated vessel

The quality of airflow mixing inside the aeration vessels of wastewater treatment plants has an important effect on the transfer of oxygen to micro-organisms to decompose sewage compounds and increasing process efficiency. It can be said that the most important part of the aeration vessel is how to create an appropriate distribution of air flow by mechanical blades to improve mass transfer efficiency. In this study, the effect of blade shape on the quality of gas phase flow mixing in the gas-liquid agitated vessels was investigated by Computational Fluid Dynamics (CFD) technique. The multiphase flow behavior in the vessel was investigated by Eulerian-Eulerian multiphase approach and RNG k-ε was used to simulate the turbulentflow behavior. The studied blades included three types of angular blade designs (blade 1 (15-30°), blade 2 (15-30°) and blade 3 (45-30°). The results showed that according to the standard deviation of the gas phase distribution in theaxial direction of the vessel, the blade 1has16% better distribution than the blade 2 and also it has 22% better distribution than the blade3. Furthermore,the results showed that design 1 creates larger vortex regions in the vesselwhich causes 3.4% more than blade 2 and also about 13.5 % more than blade 3 in accumulation of gas phase.