Measurement and Correlation of Critical Gas and Liquid Velocities for Complete Circulation of Solid Particles in External Loop Airlift Bubble Columns

The external loop airlift bubble column provides an easy way of good contacting among gas, liquid and solid phases due to a relatively high recirculating liquid velocity U L . The critical gas and liquid velocities for complete circulation of solid particles, U G,C and U L,C , were measured in two different scales of columns with air, tap water and aqueous CMC solutions, and ion exchange resin and glass beads (155∼3834 μm) were employed. The U G,C was determined as the inflection point on the plot of the pressure drop due to the suspended solid particles in the downcomer as a function of the gas velocity U G . The critical liquid velocity U L,C corresponding to the U G,C was obtained from the measured relationship between U L and U G . As a result, a unified dimensionless empirical correlation of U L,C was obtained within an error of 20% and a dimensionless empirical relationship between U L and U G was developed within an error of 15%.