Tomography measurements of gas holdup in rotating foam reactors with Newtonian, non-Newtonian and foaming liquids

Rotating solid foam reactors have already proven to show high mass transfer rates and to be a potential alternative to slurry reactors. The rotation of a foam block stirrer results in a high mass transfer and in the development of different reactor sections showing specific hydrodynamics and gas holdup distributions. In order to optimize the reactor system the hydrodynamics in a lab scale reactor are studied using γ-ray tomography, a powerful method to measure the gas holdup in three-phase reactors. The influence of liquid properties, such as viscosity and surface tension, and the rotational speed on the gas/liquid distribution in the different reactor sections is investigated. Especially the viscosity has a strong effect on the entrapment of gas bubbles in the foam block structure, while the surface tension is the dominant parameter in the outer reactor section. The influence of these parameters on the inset of foaming and the collapse of the gas/liquid dispersion is investigated. Conclusions on the mass transfer performance are drawn and recommendations for further optimizations of the reactor design and the operational conditions depending on the liquid properties are developed.