The
phenomenon of gas–liquid–liquid macro-mixing in a stirred tank is largely similar to that of liquid–
liquid and gas–liquid stirred tanks. Our experiments indicate that the gas–liquid–liquid macro-mixing
can be enhanced at higher gas holdups while damped at low gas holdups. Contrary to gas effect, the
dispersed oil phase at low holdups increases the macro-mixing intensity but at higher holdups
decreases the macro-mixing intensity of the continuous phase. The experimental results show that
axial impellers are more energy efficient for gas–liquid–liquid macro-mixing than radial impellers.
A simple correlation is developed for predicting the mixing time in gas–liquid–liquid three-phase
systems and satisfactory agreement with experimental data is observed.