Abstract: An apparatus for the catalytic cracking in the fluid state of hydrocarbon feedstocks which comprises a riser-type column (2); at the top of the riser (2) and concentric therewith, a chamber (1) for separation of the hydrocarbon vapors and the coke-laden catalyst particles; directly above the upper opening of the riser (2) and in the interior of said chamber (1), a ballistic separator (3); at least one unit for regeneration of the spent catalyst, fed by stripped particles received from said chamber. The chamber (1) for separation of the coke-laden catalyst particles and the stripping thereof comprises, at a level intermediate between the bed (6) of particles being stripped and the opening of the riser (2), a means (11) adapted to form a baffle for locally reducing the diameter of said chamber (1) and the free passage at the periphery of the riser (2), thereby reducing recirculating streams of hydrocarbon vapors in separation chamber (1) of the FCC unit thus avoiding overcracking.

Abstract: A process for the substantial homogenization of the mixture of hot solid particles and of the hydrocarbon vapors to be treated within a tubular reactor (preferably an FCC unit) for the cracking of hydrocarbons in a fluidized bed of hot solid particles. Directly downstream of the zone of injection, in the reaction zone of the feedstock to be or being treated, usually where at least 75 percent of the droplets of the feedstock are vaporized, there is injected into the reactor a fluid in the gaseous state at one or more points on the interior surface of the side wall of the reactor.