Method and apparatus for cracking residual oils

In a combination gas oil catalytic cracking-regeneration operation comprising a riser cracking zone in combination with a single regenerator zone of restricted temperature limitations, below 1400.degree. F., the method for improving the operation with respect to feeds processed, catalyst regeneration and providing a high temperature operation for processing high boiling heavy residual oils which comprises,

• providing a riser cracking zone in combination with an added second regeneration zone, said second regeneration zone adjacent to but above said restricted temperature regeneration zone,
• passing a suspension of hydrocarbon product vapor and catalyst following traverse of the riser cracking zone into a suspension breaking zone which promotes the downward flow of separated catalyst particles from product vapors entraining catalyst particles, passing the product vapors through a passageway immediately adjacent the suspension breaking zone in open communication with a cyclone separation zone, separating hydrocarbon product vapors from catalyst in said cyclone separation zone and recovering said hydrocarbon product vapors separately from cyclone separated catalyst,
• stripping catalyst separated from hydrocarbon vapors before downward passage thereof to a lower portion of a dense fluid bed of catalyst in said temperature restricted regeneration zone,
• effecting a partial regeneration of the catalyst in a dense fluid catalyst bed in said temperature restricted regenerating zone up to 1400.degree. F. with an amount of oxygen sufficient to effect from 10 to 90 wt% removal of carbonaceous material and produce a flue gas rich in CO and provide catalyst particles with a residual carbon thereon, passing the partially regenerated catalyst through an external stripping zone and thence through a confined transfer zone to a bottom portion of the upper regeneration zone,
• further regenerating the partially regenerated catalyst comprising residual carbon in a dense fluid catalyst bed in the second regeneration zone at a temperature of from about 1500.degree. F. up to 1800.degree. F., and
• passing high temperature regenerated catalyst from said second regeneration zone through an external stripping zone before passage to said riser cracking zone for admixture with said high boiling heavy feed oil charged thereto.