Experimental Characterization of Gas–Liquid Mass Transfer in a Reaction Bubble Column Using a Neutralization Reaction

The bubble column developed at Otto-von-Guericke-Universitat Magdeburg (OVGU, AG Zahringer) was intended to facilitate the detailed characterization of a bubble column with a quick neutralization reaction as an interesting limiting case. The model column used for this purpose had a volume of about V = 12 L and a modular injection system for the production of bubble chains and a bubble curtain, consisting of four bubble nozzles. Exclusively optical measurement techniques have been used to measure bubble sizes, velocities and aspect parameters, as well as liquid velocity and concentration of the transferred component. The reaction examined in this column was the absorption of CO2 from the bubbles to the slightly basic liquid phase. The pH-change in the liquid phase could then be monitored by a laser induced fluorescence technique, called Two-Tracer LIF, involving two different tracer dyes. One of these dyes traces the pH-change, the other stays passive and images the lightening situation in the column, including bubble shadows and reflections. This “live-background” allows then for the correction of the pH images. The knowledge of bubble parameters, liquid velocity and pH-fields enables the calculation of further quantities like mass transfer coefficient and volumetric mass transfer coefficient. These kinds of measurements have been executed for a variety of parameters like gas flow rate, filling height, increasing liquid viscosity or decreasing liquid surface tension. The results, used also for validation purposes of numerical calculations in partner groups (see Chapters “ Euler-Euler Modeling of Reactive Flows in Bubble Columns”, “ Multi-scale Investigations of Reactive Bubbly Flows” and “ Chemical Reactions in Bubbly Flows”), are made available for interested research groups in a data-base accessible under https://www.lss.ovgu.de/Info/Downloads.html.