Effects of perforated plates on mass transfer and hydrodynamic behavior in the internal loop airlift contactor

Abstract

The performance of an airlift contactor with perforated plates inserted in the riser (ALC-P) was compared to those of a bubble column (BC) and a conventional airlift contactor (ALC). Although the overall gas holdup in all three types of contactors did not differ significantly from each other, the riser gas holdup in the ALC-P was found to be much higher than that in the ALC and in the bubble column. It was concluded that the perforated plate induced flow resistance in the system which resulted in a lower liquid velocity and a higher gas holdup. The investigation was also conducted to examine the effect of the design of a perforated plate on the performance of the ALC-P The design variables of interest included the size and number of holes in the perforated plate and also the number of plates inserted into the system. Reducing the size and number of holes in the perforated plate resulted in a higher flow resistance. This decreased the liquid velocity in the system while increased the gas holdup. Increasing the number of perforated plates was found to give similar results on both liquid velocity and gas holdup. The rate of gas-liquid mass transfer in the ALC-P depended principally on the riser gas holdup. Hence, it can be enhanced by inserting perforated plates with small hole size and sparse hole population into the ALC. In addition, inserting more perforated plate into the ALC was also found to be beneficial for the rate of gas-liquid mass transfer. The investigation revealed that the increase in the specific interfacial area between gas and liquid was the main factor responsible for this increase in the rate of mass transfer in the ALC-P