Effect of air agitation on the flow phenomena of draft tube precipitator

摘要

Industry scale draft tube precipitators (Agglomerators and Growth tanks), especially the taller aspect ratio (H/T ≥ 2) precipitator in alumina Bayer process have the task to uniformly suspend alumina hydrate particles with minimum power consumption.It is important to note that the overflow particle concentration will be uniform if particles are uniformly suspended in the entire precipitator volume else gradients in particle concentration may prevail in alumina precipitators.In industrial operational practice, it is supposed that the injected air from the bottom of the draft tube precipitator assists and enhances the hydrate particle suspension.In the present work, investigation has been made to analyze the flow phenomena in the taller aspect ratio design with and without air agitation.Also, the work depicts the role of draft tube slots on the overall flow pattern and hydrate particle suspension.In order to analyze and characterize the flow phenomena, computational fluid dynamics (CFD) modeling study has been used to investigate the flow and hydrate suspension behaviour.