Understanding the phenomenon of liquid weeping requires knowledge of the bubbling and weeping cycle. Hence, an image analysis algorithm is developed and subsequently coupled with high-speed imaging techniques to examine the different stages in the bubbling and weeping cycle automatically. The bubbling and weeping cycle is studied under various operating conditions, using the developed algorithm, coupled with high-speed imaging techniques and the pressure fluctuation measurement. The effect of orifice angle (where the orifice angle is a measure of the orifice taperness) on the liquid weeping rate is evaluated over a range of superficial orifice gas velocities and justified with the aid of the developed algorithm, coupled with high-speed imaging techniques. A gas distributor plate with negative angle orifices is recommended for improved operation of industrial bubble column reactors over the range of superficial orifice gas velocities considered in this study, because it substantially decreases the liquid weeping rate.

Liquid weeping at the orifices of a gas distributor plate is one problem commonly encountered in bubble column operations. The effect of orifice surface roughness on the liquid weeping phenomenon in a bubble column is investigated over a superficial orifice gas velocity range of 143−703 cm/s. High-speed images of the bubbling and liquid weeping process are analyzed using a computer-aided image analysis algorithm. Pressure fluctuation in the plenum is also monitored. The liquid weeping rate is found to decrease with an increase in orifice surface roughness at low superficial orifice gas velocities while it increases with an increase in surface roughness at high superficial orifice gas velocities. Analysis indicates that the orifice surface roughness affects liquid weeping indirectly by changing the bubbling behaviors at the orifice. At low superficial orifice gas velocities, an increase in orifice surface roughness reduces the bubble size at bubble detachment. The reduction in pressure fluctuation in the plenum thus decreases the liquid weeping rate. On the other hand, as the superficial orifice gas velocity is approaching the bubbling/jetting regime transition, an increase in orifice surface roughness increases the transition velocity and hence the liquid weeping rate increases. Nonetheless, a modification of the orifice surface roughness is a viable solution to the liquid weeping problem in industrial bubble columns.