Pulsing to improve bubble column performance: I. Low gas rates

• Published in: AIChE journal 2006-03, Vol.52 (3), p.1103-1115
• Main Authors: Knopf, F. Carl, Ma, Jia, Rice, Richard G., Nikitopoulos, Dimitris
• Format: Article
• Language: English
• Subjects: Air flow; Applied sciences; bubble columns; Bubbles; Chemical engineering; CO2mass transfer; Exact sciences and technology; Heat and mass transfer. Packings, plates; Hydrodynamics of contact apparatus; oscillation
• ISSN: 0001-1541; 1547-5905
• DOI: 10.1002/aic.10698

The liquid phase of a batch bubble column was subjected to low‐amplitude pulsations at modest frequencies (range 0–30 Hz). At low gas rates (up to 5 mL/s) using a single‐injector tube we found that substantial bubble breakage occurred at frequencies < 30 Hz. At the low flow rates examined, enhanced bubble breakup occurred mainly as a result of two‐phase flow developing within the injector tube. External sinusoidal pulsation caused high‐velocity water ingestion (suck‐back) and expulsion from the injector. This suck‐back action caused intense fragmentation of gas slugs within the injector, often into many very small bubbles, as high‐speed imaging showed. Mass transfer coefficients were measured as a function of pulsation frequency and driver amplitudes at several air flow rates, demonstrating the benefits of this type of pulsed bubble column. A simple dynamic mechanical model of the pulsed liquid column predicted resonance, which depended on membrane thickness of the driving piston. © 2005 American Institute of Chemical Engineers AIChE J, 2006