SIMULATION OF MASS-TRANSFER IN A BATCH AGITATED LIQUID LIQUID DISPERSION

A simulation model is developed to compute the transient Sauter-mean drop diameter and the fractional mass transfer in batch agitated liquid-liquid dispersions when the continuous phase, dispersed phase, or both phases offer significant resistance to mass transfer. This model accounts for mass transfer during drop breakup, drop-drop coalescence or rebounding, drop oscillations, and free motion of the drops throughout the vessel. Using 16 different formulations, 8 of which were developed here, the transient fractional mass transfer was predicted with an average deviation of +/- 20% for all four directions of diffusion and dispersion, using no adjustable parameters. However, to enhance the simulation, one constant in the breakage frequency was then varied to improve predictions to +/- 15% for 10 simulations, including 4 with surfactants present. Furthermore, the transient Sauter-mean drop diameter was predicted with an average deviation of +/- 8% for these simulations. The fraction of the total mass transferred due to drop-drop interactions was found to be indeterminate, but small, in this work. However, drop breakup and subsequent damped oscillations accounted for about 5% of the total transfer in the simulation for dispersed-phase-controlled systems and insignificantly for continuous-phase-controlled systems.