A new experimental campaign has started at the Department of Energy of Politecnico di Milano within the AURIGA project, aiming to investigate bubble coalescence in aqueous ionic-liquid mixtures. The activity is part of the bubble-scale research framework devoted to understanding the local mechanisms that govern gas-liquid flows and their impact on the behaviour of industrial bubble columns.
Bubble coalescence is a key phenomenon in multiphase reactors. Although it occurs at the microscopic scale when two bubbles come into contact and merge, it strongly influences bubble size distributions, gas-liquid interfacial area and flow-regime transitions, ultimately affecting reactor performance. Current understanding of the role of electrolytes and surface-active compounds on coalescence remains incomplete, particularly for ionic-liquid systems.
To address this challenge, a dedicated experimental facility has been developed to generate controlled bubble-pair interactions under well-defined conditions.
High-speed imaging at several thousand frames per second is used to capture the rapid dynamics of approaching, coalescing and rebounding bubbles. Advanced image-processing algorithms are then applied to automatically determine coalescence probability, approach velocity and coalescence time for hundreds of bubble pairs.
The campaign will focus on aqueous mixtures containing ionic liquids relevant for carbon capture applications. By identifying the conditions that promote or inhibit coalescence, the study will provide new insight into the interfacial mechanisms governing these systems and contribute to the development of more accurate models for bubble-column reactors.