Incorporation of Powder Particles into an Impeller-Stirred Liquid Bath through Vortex Formation

Abstract

The present study addresses the incorporation of fine particles into liquids via the creation of a large-scale swirling vortex on the liquid free surface using a rotary impeller positioned along the axis of a cylindrical vessel. Four types of particles are used in the experiments to investigate the incorporation efficiency of the particles into a water bath under different impeller rotation speeds. Additionally, the vortex characteristics are investigated numerically. The results reveal that two factors, namely the particle wettability and turbulent oscillations at the bottom part of vortex surface, play dominant roles in determining the particle incorporation behavior. Hydrophobic particles are incapable of being incorporated into the water bath under any of the conditions examined in the present study. Partly wettable particles are entrained into the water bath, with the efficiency increasing with the impeller rotation speed and particle size. This is because an increase in the impeller rotation speed causes vortex deformation, whereby its bottom part approaches the impeller blades where the turbulent surface oscillations reach maximum amplitudes. Another possible mechanism of particle incorporation is the effect of capillary increases of liquid into the spaces between particles, which accumulate on the bottom surface of the vortex.

Free surface entrainment of oxide particles and their role in ultrasonic treatment performance of aluminum alloys

“…The frequency of the free surface oscillations is much lower compared to the frequency of ultrasound waves because the oscillations are caused mainly by large-scale turbulent eddies and acoustic streaming. This mechanism is probably similar to that observed by Komarov et al [31] for a case when particles were entrained into water due to oscillating motion of vortex in a mechanically agitated water bath. Another interesting phenomenon is shown in Fig.…”

“…Entrainment of particles from the free surface, however, has been a subject of considerable interest in other fields such as mechanical stirring and agitation. For example, Komarov et al [31] investigated incorporation of fine particles into liquid from the free surface of a large-scale swirling vortex created around the axis of a rotary impeller in a cylindrical vessel. Two feasible mechanisms for particle penetration behavior were proposed.…”

Effects of Impeller Rotational Speed and Immersion Depth on Flow Pattern, Mixing and Interface Characteristics for Kanbara Reactors Using VOF-SMM Simulations

“…However, the velocity below the impeller is still very small no matter how fast the IRS is. These phenomena were also observed by T. Yamamoto et al [7][8][9][10] in the flow characteristic of aluminum melt by mechanically stirring. miniscule, making it particularly difficult to achieve global mixing of species in the reactor.…”

“…However, the velocity below the impeller is still very small no matter how fast the IRS is. These phenomena were also observed by T. Yamamoto et al [7][8][9][10] in the flow characteristic of aluminum melt by mechanically stirring. To further study the effect of operation parameters on the bath flow of KRs, the mean velocity of the fluid in the bath under different IIDs was also investigated by indirectly measuring the dynamic energy of the bath obtained from the mechanical stirring.…”

“…This result illustrated that increasing impeller rotation speed is an effective method to enhance the mass transfer behavior of reactors. Their more recent research [10] found that increasing rotation speed would increase vortex depth and the intensity of turbulent fluctuations on the free surface. He et al [11] investigated the coalescence and sedimentation behavior of falling droplets in a vessel of MSM.…”