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Bubble column reactors are widely used in many industrial applications due to their simplicity and safety of operation. Despite these advantages, the design and scale‐up of bubble column reactors is still challenging especially for industrial conditions at elevated pressure and temperature. One reason is the uncertainties concerning the specific interfacial area which is directly dependent on the bubble size distribution, bubble velocity, and gas hold‐up. All these parameters are difficult to measure under industrial conditions due to the opaqueness of the bubbly flow and the safety risks of using organic solvents at elevated pressures and temperatures. This article introduces endoscopic bubble image velocimetry, a new measuring method that enables the detection of bubble sizes and bubble velocities in organic solvents at elevated pressure and temperature (pmax = 1.85 MPa and Tmax = 70 °C) for maximal gas hold‐ups of 16 %. For this system it becomes evident that the bubble size distribution for low superficial gas velocities is almost unaffected by pressure and temperature, whereas the bubble velocity decreases slightly.

Ziel des BMBF‐Projekts „Multi‐Phase”︁ ist die Optimierung von Mehrphasenreaktoren mit skalenunabhängigen Rechenmodellen, Messtechniken und ‐apparaten. Das Projektkonsortium verknüpft Kompetenzen der grundlagenorientierten Forschungspartner und verschiedener KMU aus dem Bereich der Mess‐ und Apparatetechnik mit den Anforderungen der industriellen Praxis. Evonik Industries AG führt die Übertragung von entwickelten Labordaten, Messtechniken und Modellen auf industrielle Maßstäbe und Stoffsysteme durch und stellt die Ergebnisse den Projektpartnern zur Verfügung. Hieraus werden signifikante Energieeinsparungen und eine deutlichen Minderung der CO2‐Emmissionen erwartet.

Bubble column hydrodynamics influence important performance parameters like conversion, selectivity, and yield of a chemical reaction. Backmixing of the liquid phase and gas holdup are thereby of particular importance. In order to determine these parameters, a number of correlations exist in the literature. These correlations are mainly derived from small-scale equipment operated under atmospheric conditions using the physical system air/water. Published experimental results regarding gas holdups and dispersion in bubble columns operated under high pressure are discussed and a recommendation for further research is given.

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