GAS HOLDUP BEHAVIOR IN A TALL BUBBLE COLUMN WITH PERFORATED PLATE DISTRIBUTORS

The gas holdup in an 8-m high bubble column with a perforated plate distributor is measured over a superficial gas velocity range of 0.0075 to 0.54 m/s for an air-tap water system. Various combinations of the distributor design parameters, viz. the number, diameter and pitch of the holes, are tested for elucidating their effects on the gas holdup. The gas holdup behavior is described in relation to the bubble flow regime, which can be divided. in order of increasing gas velocity, into the dispersed bubble, the clustered/coalesced bubble and the slugging regimes. A correlation scheme is developed for predicting the gas holdup-superficial gas velocity relationship. Among correlation parameters, the critical gas holdup for the transition from the dispersed to the clustered bubble regime is predicted based on the bubble-wake concept; the onset of bubble clustering is induced via the bubble-wake interaction, which restricts the maximum gas holdup allowable for a homogeneous bubble dispersion. The proposed correlation scheme is capable of reproducing not only the "standard" curve for single-hole gas spargers but also the complex behavior observed for typical multi-hole distributors.