Energy efficient solids suspension in an agitated vessel–water slurry

Power consumption required to suspend water–solid slurries in a mechanically agitated tank has been studied over a wide range of design and solids conditions with the goal to improve the agitation energy efficiency. It is demonstrated that the power required for providing off-bottom solids suspension and solids dispersion could be reduced dramatically with baffles removed, as in comparison with conventional agitator designs where vertical baffles were used.Axial-flow impellers in baffled tanks were found more energy efficient to suspend solids off the bottom, consistent with the literature data. However, with baffles removed, radial-flow impellers were found more energy efficient than axial flow impellers. The effect of removal of baffles on the solids dispersion was also included. The impeller geometrical effects include pitch angle of blade, number of blades on energy efficiency were studied. The impacts of solid concentration and particle size on power consumption were also investigated.

► Power required for providing off-bottom solids suspension could be reduced dramatically with baffles removed.
► With baffles removed, radial-flow impellers were found more energy efficient than axial flow impellers.
► Less power is required to suspend small particles, for the same amount of solids mass.
► Improved solids dispersion could be achieved by removal of baffles.