ON THE LOCAL GAS HOLDUP AND FLOW PATTERN IN STANDARD-TYPE BUBBLE-COLUMNS

Local gas holdups and bubble size distributions have been measured sim ultaneously in a standard-type bubble column equipped with a perforate d plate as a gas disperser. High values in the time series of the loca l gas holdup which appear on a periodic basis could be detected and an alyzed. The phenomenon of the bubble hose, defined as a zone of high b ubble number density moving helically in a bubble column, has been rec ognized visually using photographs and by means of the recorded data. A formation mechanism for the bubble hose dependent on the gas dispers er geometry capable of explaining the observed asymmetric liquid and g as flow pattern is suggested. The existence of a relationship between the bubble hose, the average bubble diameter and the superficial gas v elocity has been demonstrated.