Characterization of a chemical reaction in a bubble column using Wire-Mesh Sensor and ultrafast X-ray CT

Design and operation of bubble columns are of main importance, since they strongly influence yield and selectivity of chemical reactions. In order to improve the process efficiency, a fundamental understanding of flow phenomena in bubble columns is necessary. A lot of research has been carried out for the investigation of hydrodynamics of bubble columns. Nonetheless, hydrodynamics is changing in the presence of a chemical reaction (e.g. shrinkage of bubbles due to mass-transfer processes). Hence, there is a strong interaction of hydrodynamics, mass-transfer and chemical reaction within bubble columns, which has been investigated in the past, amongst others, using the reaction of sodium hydroxide and carbon dioxide. However, most works are restricted to low gas holdups or provide only single point information due to the use of local probes (e.g. pH measurement). This contribution comprises the experimental investigation of the reaction of sodium hydroxide and carbon dioxide, applying Wire-Mesh Sensors for determining the locally occurring reaction steps at different operating conditions (e.g. gas flow rate of carbon dioxide, initial concentrations of sodium hydroxide). In turn, experimental results are compared with concentration profiles derived from known reaction kinetics. The application of Wire-Mesh Sensors for this purpose allows the visualization of the concentration distribution within the cross-section of the bubble column. Additionally, ultrafast X-ray computer tomography is used simultaneously to study the change of hydrodynamics during the reaction.