Effects of operating parameters on residence time distribution in a REFLUX flotation cell

•Fluid behavior in the two-phase system approached a plug-flow rather than perfect mixing.•The feed flux was the most dominant factor affecting the mean residence time (MRT) in RFCTM.•Increase in bias with the same feed flux decreased MRT while not changing RTD pattern.•Intensification of gas flux increased the peak value of tracer concentration inside RFCTM.