Advanced analysis of liquid dispersion and gas–liquid mass transfer in a bubble column with dense vertical internals

Abstract The influence of dense vertical tube bundles in a batch bubble column reactor (BCR) of 100 mm diameter and 1100 mm clear liquid height on liquid dispersion and gas–liquid mass transfer was studied. In particular, the effects of different tube patterns (triangular and square pitch), tube diameters (8 and 13 mm) and bottom end designs (flat and U-tube) having a tube diameter-to-pitch ratio of approx. 1.3 were investigated. Dispersion coefficients were determined based on conductive tracer experiments recorded via wire-mesh sensors (WMS) with up to 90 measurement points distributed in the column’s cross-section in between the tubes. The gas–liquid mass transfer coefficient was determined via fast-responding oxygen needle probes. Tube pitch and pattern were identified as the most crucial design parameters for the extent of liquid dispersion. We found that particularly the U-tube bottom end design induces large liquid circulation patterns, which enhance dispersion. The presence of internals decreases the k l a value as a consequence of turbulence damping, which is also confirmed by lower k l values (e.g. 0.6 × 10 −3  m s −1 for the empty BCR and 0.25 × 10 −3  m s −1 for the square pitch with 8 mm tubes at 0.05 m s −1 superficial gas velocity), whereas the pitch is the most decisive design parameter. The U-tube bottom end design was identified as the most beneficial configuration with respect to liquid mixing and gas–liquid mass transfer.