Investigation of Hydraulic Behavior in a Gas-Agitated Disc and Doughnut Column for Solvent Extraction

Abstract

The gas-agitated extraction column represents a novel extraction technology that employs gas to break-up droplets. Hydraulic characteristics, including droplet size (d32), dispersed-phase holdup (xd), and gas holdup (xg), are critical for design and scaling-up of extraction columns. These parameters were evaluated using a 30 mm disc-and-doughnut column (DDC) equipped with a gas-input unit. The water as dispersed-phase and tributyl phosphate (TBP)/kerosene as continuous-phase. The results show that when no gas is introduced, the countercurrent cannot be maintained, and reach flooding directly. Once gas is introduced, the flow state returns to normal. Results indicate that d32 diminishes with increasing gas-velocity, suggesting that gas can act as a substitute energy for droplet fragmentation. The xd initially decreases and then increases with greater gas-velocity, while increasing with the velocities of two-phases. xg only increases with gas-velocity. Empirical correlations for d32, xd, and xg are proposed with deviations of 11.59%, 15.85%, and 4.29%, respectively.

Keywords: Gas agitated, Disc and doughnut extraction column, Sauter diameter, Dispersed phase holdup, Gas holdup