Efficacy of partial baffles for a vessel agitated by a Rushton turbine impeller

Masanori Yoshida, Kohei Ishioka, Hiromu Ebina, Koki Oiso, Hayato Shirosaki, Ryota Tateshita
2018 Chemical Industry and Chemical Engineering Quarterly  
Article Highlights • Standard baffling may not be the best approach for a vessel agitated by a Rushton turbine impeller • Baffle efficacy is reflected by the bulk liquid flow affecting the impeller power consumption • Partial baffles are effective in the flow and power, favorably comparing with full baffles Abstract For a vessel agitated by a Rushton turbine impeller, the efficacy of partial baffles was evaluated through examination of the liquid flow and impeller power characteristics. The
more » ... flow formed a pattern having circulation loops of different intensity and largeness depending on the baffle condition: the baffle length relative to the liquid depth for the vessel. Consequently, the liquid flow within the vessel affected the impeller power number. The characteristic circulation loops, which generally reflect the baffle efficacy, were assessed in terms of the discharge flow through the impeller and the energy transmission within the vessel based on the flow velocity profiles. The shorter length of baffles fitted partially in the upper half of the liquid phase was revealed to be effective, supported in combination by a comparable discharge flow and a successful energy transmission. Keywords: agitation vessel, Rushton turbine impeller, partial baffles, liquid flow, impeller power. When vessel-type apparatuses agitated by mechanically rotating impellers are used for lower viscosity liquids in turbulent flow regimes, the vessels have baffles in many cases. The standard is wall baffles which consist of four flat vertical plates, directed radially and spaced at 90° intervals around the vessel periphery, starting at the vessel bottom and running the length of the vessel side to the liquid top. This condition is often designated as fully baffled or standard baffle. Without the baffles for the vessel, formation of a central vortex results in poor mixing, with the free surface sagging downwards in the center.
doi:10.2298/ciceq170921001y fatcat:fuuxtnhdfrfrjgaga2vvnrg3o4