Hydrodynamics and mass transfer in the horizontal rotating foam stirrer reactor

The rotating foam stirrer reactor is a novel type of multi-phase reactor where highly open-celled materials, solid foams, are used both as a catalyst support and as a stirrer. One of the advantages of rotating foam stirrer reactors compared to e.g. slurry reactors is the absence of a catalyst separation step. Moreover, in the standard foam stirrer configuration, i.e., the foam structures (blades or donut-shaped foam blocks) are mounted on a vertical shaft, the formation of finely dispersed bubbles and the fast refreshment of the catalyst surface lead to better mass transfer rates.
In this work, a new foam stirrer design is presented. A donut-shaped foam block is mounted on a horizontal shaft. Using gamma-ray tomography, the hydrodynamics of the system is described. When the reactor is partially filled with liquid, a "spray regime" is observed which leads to the formation of fine liquid droplets and fine gas bubbles enhancing the gas-liquid mass transfer rate. Furthermore, due to the centrifugal forces at high rotational speeds, the gas is separated from the catalyst only by a very thin liquid film. This enhances the liquid-solid mass transfer of the gas reactant, which is often the limiting component in hydrogenation or oxidation reactions. Mass transfer measurements will be discussed for different operation conditions.