Abstract: A riser includes a housing in communication with a entry conduit and an exit conduit. The housing is defined by a holdup chamber having a volume of between about 1133 liters and about 45307 liters. The riser is designed to receive a hydrocarbon feed and a catalyst. An apparatus for fluid catalytic cracking includes a riser in fluid communication with a reactor vessel. A hydrocarbon feed stream and a catalyst travel through a first section of the riser at a first velocity of between about 1.5 msec to about 10 msec and through a second section of the riser at a second velocity of more than about 15 msec. A process for fluid catalytic cracking uses a riser with a holdup chamber. A hydrocarbon feed and a catalyst decrease in velocity in the holdup chamber to between 1.5 msec and 10 msec.

Abstract: A riser includes a housing in communication with a entry conduit and an exit conduit. The housing is defined by a holdup chamber having a volume of between about 1133 liters and about 45307 liters. The riser is designed to receive a hydrocarbon feed and a catalyst. An apparatus for fluid catalytic cracking includes a riser in fluid communication with a reactor vessel. A hydrocarbon feed stream and a catalyst travel through a first section of the riser at a first velocity of between about 1.5 m/sec to about 10 m/sec and through a second section of the riser at a second velocity of more than about 15 m/sec. A process for fluid catalytic cracking uses a riser with a holdup chamber. A hydrocarbon feed and a catalyst decrease in velocity in the holdup chamber to between 1.5 m/sec and 10 m/sec.

Abstract: The invention improves a system and apparatus for the recovery of fine solid particles entering the slurry system of a fluidized catalytic contacting process by returning a portion of the recovered solids from the main separator directly back to the reactor stripper. The invention recovers fine particulate material from an FCC main column and returns the particulate material to an FCC stripper to reduce the amount of fine material that continues to recycle through the FCC reactor and product separator. By returning fine particulate material from the FCC product separation zone directly to a low velocity area of the stripping section, the invention breaks the reactor--main column recycle loop that concentrates the fines. Fines entering the reactor stripper will not be carried back into the cyclones for unwanted return to the main column. By the recycling of fines to the stripper via this invention, the fines concentration in the slurry system can decrease by up to 300%.