In an FCC apparatus in which swirl arms are used to discharge gas and catalyst from a riser, the swirling movement of the catalyst particles is inhibited while impeding the catalyst particles and gaseous products from exiting the disengaging chamber and entering a reactor annulus. The catalyst particles and gaseous products pass through a tunnel comprising a vertical wall to enter the reactor annulus. The vertical wall presents a face that is opposed to the angular direction in which the catalyst particles and gaseous products swirl.A baffle may be located at the intersection between the reactor annulus and the disengaging chamber to deflect catalyst laterally in a stripping section after exiting the reactor annulus. The baffle may be equipped with openings to fluidize the large proportion of catalyst passing over this region to effectively pre-strip this catalyst before it enters a stripping section.