Quantifying the flow and residence time distribution (RTD) in a reactor is critical for predicting reactor performance measures such as yield and selectivity. This work investigated a continuous industrial scale reactor (diameter 11 ft, height 37 ft) employing a 3-stage agitation system with a plunging jet inflow. In operation, the agitation and liquid level are adjusted based on throughput and the specific product being produced. The objective of this work was to quantify RTD under the different operating conditions of liquid level, throughput and agitation. Flow in the reactor was modeled with computational fluid dynamics (CFD). A combination of different modeling approaches was used to better facilitate the CFD simulations. The Volume of Fluid (VOF) method was used to model the plunging jet (gas-liquid) two-phase flow with unsteady-state simulations, while the Multiple Reference Frames (MRF) model was used to model the stirred tank with steady-state simulations. The two modeling approaches were interfaced by using the plunging jet simulation result as the input boundary condition for the reactor flow simulation. The effect of gas entrainment from the plunging jet impingement was accounted for by using the (dampened) velocity profile of the impinging jet. The RTD was obtained from stochastic particle tracking which tracks trajectories and residence times of massless tracers in the reactor. The Random Walk Model was used for dispersion of tracers due to turbulent eddies. A large number of tracers (>10,000) was needed to account for the random effects of turbulence and ensure statistically stable results. The Time Scale Constant in the Radom Walk Model was adjusted to accommodate significant turbulence level differences in discreet regions of the tank. The CFD-predicted flow pattern compared well with lab-scale experiments. The predicted mean RTD was consistent with the bulk reactor turn-over time