Detailed study of the gas-solid flow in FCC reactor was performed using Euler-Euler two-fluid model. Two distinct regions were identified in the reactor vessel based on differences in catalyst void fraction and fluid flow: the dilute phase congested disengager region and dense phase congested stripper region. Velocity profile revealed an inert yet random flow pattern in the disengager and a counter-current type of flow with a pronounced radial unevenness in the stripper. Residence time distribution proved that a small portion of oil vapour could linger over 5min before exiting despite that the apparatus may have a significantly shorter average residence time.