A novel experimental set-up for generating microbubbles for the removal of inclusions from water and liquid metals

To enhance steel cleanliness, extensive research has been conducted on bubble flotation techniques for inclusion removal. However, effective removal of nonmetallic inclusions smaller than 50 μm remains a challenge during standard liquid metal processing operations. These tiny inclusions have insufficient rising speeds to enable them to float out to the slag layer on their own. Several studies have demonstrated that the use of 500-μm bubbles would be necessary to facilitate the flotation of sub-50-μm inclusion particles from liquid steel within a tundish. Our approach to generating microbubbles in liquid metals uses liquid shearing flows. This method splits forming bubbles into smaller sizes by applying intense shear stresses. As a result, significantly larger surface areas are created, enhancing the interaction between the microbubbles and the inclusions. To test the effectiveness of this approach, a novel setup comprising submerged nozzles within a liquid metal was designed, manufactured, and operated. This setup allowed for experimentation with different rotational speeds and effluent gas flow rates, thereby determining the bubble sizes produced. Microbubbles within the desired size range (400–600 µm) were successfully generated in a Cerrolow 136 eutectic alloy.