Patent ID: 7658889

Claim:
In a fluidized catalytic cracking unit comprising a vertically disposed riser housing a reaction zone, the improvement comprising at least one redistribution device for redistribution of catalyst inside said reaction zone, the catalytic cracking unit comprising feedstock injectors at a plane within the riser, and at a plane above the feedstock injectors, mixed temperature control (MTC) injectors, wherein said redistribution device has the general shape of a continuous ring adjacent the riser wall and along the inside periphery of said wall, said redistribution device creating a restriction in the cross section of the riser ranging between 30% and 45% and having a profile section at least partially rectilinear, and being located a) either in a zone encompassed between the plane of the feedstock injectors and the plane of the MTC injectors, or b) at a height of between 0.1 and 5 meters above the plane of the MTC injectors.