Patent ID: 8349170

Claim:
A fluid catalytic cracking process, comprising: a) injecting a heavy hydrocarbon feed through one or more feed nozzles connected to an external fluid cracking reactor riser section wherein the external fluid cracking reactor riser section is in fluid connection with a lower internal reactor riser located inside of a fluid catalytic cracking reactor vessel; b) contacting the heavy hydrocarbon feed with a hot fluidized catalyst in the external fluid cracking reactor riser; c) passing at least a portion of the heavy hydrocarbon feed and the hot fluidized catalyst through the lower internal reactor riser; d) passing at least a portion of the heavy hydrocarbon feed and the hot fluidized catalyst from the lower internal reactor riser to an upper internal reactor riser; and e) retrieving a fluid catalytically cracked product stream and a spent catalyst stream from the fluid catalytic cracking reactor vessel; wherein at least a portion of the heavy hydrocarbon feed is catalytically cracked into lower molecular weight hydrocarbon compounds which are retrieved as the fluid catalytically cracked product stream; and wherein said fluid catalytic cracking reactor vessel, comprises: said lower internal reactor riser, wherein the lower end of the lower internal reactor riser is attached to the shell of the fluid catalytic cracking reactor vessel; and said upper internal reactor riser wherein the lower end of the upper internal reactor riser terminates in a conical section which is connected to a cylindrical sleeve section; wherein the upper section of the upper internal reactor riser is not in fluid connection with the dilute phase section of the reactor vessel, and at least two riser outlet ports are mechanically connected to the upper section of the upper internal reactor riser: and wherein the upper end of the lower internal reactor riser is in fluid connection with the upper internal reactor riser and the dilute phase section of the reactor vessel; the upper end of the lower internal reactor riser is not mechanically connected to the upper internal reactor riser; the largest diameter of the conical section of the upper internal reactor riser is larger than the diameter of the upper end of the lower internal reactor riser; the cylindrical sleeve of the upper internal reactor riser has a diameter larger than the diameter of the upper end of the lower internal reactor riser; at least a portion of the cylindrical sleeve of the upper internal reactor riser overlaps with at least a portion of the upper end of the lower internal reactor riser; and there is no mechanical means located in the region of the overlapping portion of the cylindrical sleeve of the upper internal reactor riser and the upper end of the lower internal reactor riser for restricting the eccentricity between the cylindrical sleeve and the upper end of the lower internal reactor riser.