On the local gas holdup and flow pattern in standard-type bubble columns

Local gas holdups and bubble size distributions have been measured simultaneously in a standard-type bubble column equipped with a perforated plate as a gas disperser. High values in the time series of the local gas holdup which appear on a periodic basis could be detected and analyzed. The phenomenon of the bubble hose, defined as a zone of high bubble number density moving helically in a bubble column, has been recognized visually using photographs and by means of the recorded data. A formation mechanism for the bubble hose dependent on the gas disperser geometry capable of explaining the observed asymmetric liquid and gas flow pattern is suggested. The existence of a relationship between the bubble hose, the average bubble diameter and the superficial gas velocity has been demonstrated.