Comparative study on the flow and mass transfer characteristics of submillimeter bubbles and conventional bubbles in gas-liquid two-phase flow

The differences in flow and mass transfer characteristics between a sub-millimeter bubble column and a conventional bubble column were explored systematically by using experimental and numerical simulation methods. A specific numerical simulation approach was proposed for the flow and mass transfer processes of sub-millimeter bubbles in gas-liquid bubbly flow. The results reveal that, under comparable operating conditions, the size distribution of bubbles in sub-millimeter bubble columns is narrower, with an average size reduced to approximately 3% of that observed in conventional columns. Moreover, the gas holdup increases by over two-fold, and the interfacial area enhances by two orders of magnitude. In addition, the radial distribution of gas and liquid in the submillimeter bubble gas-liquid two-phase flow is more uniform, and the degree of axial backmixing is smaller. Notably, the interfacial area within sub-millimeter bubble columns plays a pivotal role in intensifying mass transfer, even though their liquid-side mass transfer coefficient is lower compared to conventional columns. Leveraging the substantial interfacial area, the volumetric mass transfer coefficient within sub-millimeter bubble columns is approximately ten times that within conventional columns. Notably, simulation outcomes for large-scale bubble column reactors indicate that sub-millimeter bubbles have the potential to yield a more uniform gas holdup distribution, thereby exhibiting reduced sensitivity to initial gas-liquid distribution effects. © 2024 Materials China. All rights reserved.